Taking and Importing Marine Mammals; Taking Marine Mammals Incidental to Geophysical Surveys Related to Oil and Gas Activities in the Gulf of Mexico, 5322-5450 [2020-27252]
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Federal Register / Vol. 86, No. 11 / Tuesday, January 19, 2021 / Rules and Regulations
DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric
Administration
50 CFR Part 217
[Docket No. 201204–0326]
RIN 0648–BB38
Taking and Importing Marine
Mammals; Taking Marine Mammals
Incidental to Geophysical Surveys
Related to Oil and Gas Activities in the
Gulf of Mexico
National Marine Fisheries
Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA),
Commerce.
ACTION: Final rule.
AGENCY:
NMFS, upon request from the
Bureau of Ocean Energy Management
(BOEM), hereby issues regulations to
govern the unintentional taking of
marine mammals incidental to
geophysical survey activities conducted
by oil and gas industry operators, and
those persons authorized to conduct
activities on their behalf (collectively
‘‘industry operators’’), in Federal waters
of the U.S. Gulf of Mexico (GOM) over
the course of five years. These
regulations, which allow for the
issuance of Letters of Authorization
(LOA) to industry operators for the
incidental take of marine mammals
during the described activities and
specified timeframe, prescribe the
permissible methods of taking and other
means of effecting the least practicable
adverse impact on marine mammal
species or stocks and their habitat, as
well as requirements pertaining to the
monitoring and reporting of such taking.
DATES: Effective from April 19, 2021
through April 19, 2026.
ADDRESSES: Electronic copies of the
application and supporting documents,
as well as a list of the references cited
in this document, may be obtained
online at: www.fisheries.noaa.gov/
action/incidental-take-authorization-oiland-gas-industry-geophysical-surveyactivity-gulf-mexico. In case of problems
accessing these documents, please call
the contact listed below.
FOR FURTHER INFORMATION CONTACT: Ben
Laws, Office of Protected Resources,
NMFS, (301) 427–8401.
SUPPLEMENTARY INFORMATION:
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SUMMARY:
Purpose and Need for Regulatory
Action
These incidental take regulations
(ITR) establish a framework under the
authority of the MMPA (16 U.S.C. 1361
et seq.) to allow for the authorization of
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take of marine mammals incidental to
the conduct of geophysical survey
activities in the GOM. We received a
petition from BOEM requesting the
regulations. Subsequent LOAs may be
requested by industry operators. Take is
expected to occur by Level A and/or
Level B harassment incidental to use of
active acoustic sound sources. Please
see the Background section below for
definitions of harassment.
prescribe measures for mitigation,
monitoring, and reporting. They do not
preclude a U.S. citizen from applying
for an incidental take authorization for
a specified activity with different
parameters or required measures
through a separate request and process.
Background
Section 101(a)(5)(A) of the MMPA (16
U.S.C. 1361 et seq.) directs the Secretary
of Commerce (as delegated to NMFS) to
Legal Authority for the Action
allow, upon request, the incidental, but
Section 101(a)(5)(A) of the MMPA (16 not intentional, taking of small numbers
of marine mammals by U.S. citizens
U.S.C. 1371(a)(5)(A)) directs the
who engage in a specified activity (other
Secretary of Commerce to allow, upon
than commercial fishing) within a
request, the incidental, but not
specified geographical region if certain
intentional, taking of small numbers of
findings are made, regulations are
marine mammals by U.S. citizens who
engage in a specified activity (other than issued, and notice is provided to the
public.
commercial fishing) within a specified
An authorization for incidental taking
geographical region for up to five years
shall be granted if NMFS finds that the
if, after notice and public comment, the
taking will have a negligible impact on
agency makes certain findings and
the species or stock(s) and will not have
issues regulations that set forth
permissible methods of taking pursuant an unmitigable adverse impact on the
availability of the species or stock(s) for
to that activity and other means of
subsistence uses (where relevant), and if
effecting the ‘‘least practicable adverse
the permissible methods of taking and
impact’’ on the affected species or
requirements pertaining to the
stocks and their habitat (see the
mitigation, monitoring, and reporting of
discussion below in the Mitigation
such takings are set forth.
section), as well as monitoring and
NMFS has defined ‘‘negligible
reporting requirements. Section
impact’’ in 50 CFR 216.103 as an impact
101(a)(5)(A) of the MMPA and the
resulting from the specified activity that
implementing regulations at 50 CFR part
cannot be reasonably expected to, and is
216, subpart I, provide the legal basis for
not reasonably likely to, adversely affect
issuing this rule containing the
the species or stock through effects on
regulations, and for any subsequent
annual rates of recruitment or survival.
LOAs. As directed by this legal
The MMPA states that the term ‘‘take’’
authority, the regulations contain
means to harass, hunt, capture, or kill,
mitigation, monitoring, and reporting
or attempt to harass, hunt, capture, or
requirements.
kill, any marine mammal.
Except with respect to certain
Summary of Major Provisions Within
activities not pertinent here, the MMPA
the Regulations
defines ‘‘harassment’’ as: Any act of
Following is a summary of the major
pursuit, torment, or annoyance which (i)
provisions of these regulations regarding
has the potential to injure a marine
geophysical survey activities. These
mammal or marine mammal stock in the
measures include:
wild (Level A harassment); or (ii) has
• Standard detection-based mitigation
the potential to disturb a marine
measures, including use of visual and
mammal or marine mammal stock in the
acoustic observation to detect marine
wild by causing disruption of behavioral
mammals and shut down acoustic
patterns, including, but not limited to,
sources in certain circumstances;
migration, breathing, nursing, breeding,
• A time-area restriction designed to
feeding, or sheltering (Level B
avoid effects to bottlenose dolphins in
harassment).
times and places believed to be of
particular importance;
Summary of Request
• Vessel strike avoidance measures;
On October 17, 2016, BOEM
and
submitted a revised petition 1 to NMFS
• Monitoring and reporting
for rulemaking under section
requirements.
101(a)(5)(A) of the MMPA to authorize
These incidental take regulations
take of marine mammals incidental to
govern and allow for the subsequent
conducting geophysical surveys during
issuance of letters of authorization for
the take of marine mammals incidental
1 In the notice of proposed rulemaking (83 FR
to the specified activity described in
29212; June 22, 2018), NMFS provided a brief
this Notice, within the upper bounds of
history of prior petitions received from BOEM’s
take that was evaluated for this rule, and predecessor agencies.
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oil and gas industry exploration and
development activities in the GOM.
This revised petition was deemed
adequate and complete based on NMFS’
implementing regulations at 50 CFR
216.104.
On December 8, 2016 (81 FR 88664),
we published a notice of receipt of the
petition in the Federal Register,
requesting comments and information
related to the request. This 30-day
comment period was extended to
January 23, 2017 (81 FR 92788), for a
total review period of 45 days. The
comments and information received
during this public review period
informed development of the proposed
ITR, and all comments received are
available online at
www.fisheries.noaa.gov/action/
incidental-take-authorization-oil-andgas-industry-geophysical-surveyactivity-gulf-mexico.
In August 2017, BOEM produced a
final Programmatic Environmental
Impact Statement (PEIS) to evaluate
potential significant environmental
effects of geological and geophysical
(G&G) activities on the Outer
Continental Shelf (OCS) of the GOM,
pursuant to the National Environmental
Policy Act (NEPA). The PEIS is
available online at: www.boem.gov/Gulfof-Mexico-Geological-and-GeophysicalActivities-Programmatic-EIS/. NOAA
participated as a cooperating agency in
the development of the PEIS.
NMFS published a notice of proposed
rulemaking in the Federal Register for
a 60-day public review on June 22, 2018
(83 FR 29212). The comments and
information received during this public
review period informed development of
the final ITR, and NMFS has responded
to all comments received (see
Comments and Responses).
On February 24, 2020, BOEM
submitted a notice to NMFS of its
‘‘updated proposed action and action
area for the ongoing [ITR] process[.]’’
This update consisted of removal of the
area currently under a Congressional
leasing moratorium under the Gulf of
Mexico Energy Security Act (GOMESA)
(Pub. L. 109–432, § 104) from
consideration in the ITR. BOEM stated
in its notice to NMFS that G&G
activities are not likely to be proposed
within the area subject to the leasing
moratorium during the 5-year period of
effectiveness for the ITR and, therefore,
that the ‘‘number, type, and effects of
any such proposed G&G activities are
simply too speculative and uncertain for
BOEM to predict or meaningfully
analyze.’’ These Congressional leasing
restrictions are in place until June 30,
2022. Based on this updated scope,
BOEM on March 26, 2020, submitted
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revised projections of expected activity
levels and corresponding changes to
modeled acoustic exposure numbers.
BOEM’s notice and updated information
are available online at:
www.fisheries.noaa.gov/action/
incidental-take-authorization-oil-andgas-industry-geophysical-surveyactivity-gulf-mexico. These changes are
addressed as appropriate throughout
this final ITR. On September 8, 2020,
the President effectively extended this
moratorium through withdrawal under
the Outer Continental Shelf Lands Act
(OCSLA) of the same area covered by
the GOMESA moratorium from
disposition by leasing for 10 years,
beginning on July 1, 2022, and ending
on June 30, 2032.
Geophysical surveys are conducted in
support of hydrocarbon exploration and
development in the GOM, typically by
companies that provide such services to
the oil and gas industry. Broadly, these
surveys include (1) deep penetration
surveys using large airgun arrays as the
acoustic source; (2) shallow penetration
surveys using a small airgun array,
single airgun, or similar systems as the
acoustic source; and (3) high-resolution
surveys, which may use a variety of
acoustic sources. Generally speaking,
these surveys may occur within Federal
territorial waters and waters of the U.S.
Exclusive Economic Zone (EEZ) (i.e., to
200 nautical miles (nmi)) within the
GOM, and corresponding with BOEM’s
GOM OCS planning areas (i.e., Western
Planning Area (WPA), Central Planning
Area (CPA), Eastern Planning Area
(EPA)). The use of these acoustic
sources is expected to produce
underwater sound at levels that have the
potential to result in harassment of
marine mammals. Cetacean species with
the potential to be present in the GOM
are described below (see Table 4).
These regulations establish a
framework under the authority of the
MMPA (16 U.S.C. 1361 et seq.) and
NMFS’ implementing regulations (50
CFR 216.101 et seq.) to allow for the
authorization, through LOAs, of take of
marine mammals incidental to the
conduct of geophysical surveys for oil
and gas activities in the GOM. The
regulations are effective for five years.
Description of the Specified Activity
Overview
The specified activity consists of
geophysical surveys conducted by
industry operators for a variety of
reasons related to hydrocarbon
exploration, development, and
production. These operators are
typically companies that provide
geophysical services, such as data
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acquisition and processing, to the oil
and gas industry, including exploration
and production companies. The petition
describes a five-year period of
geophysical survey activity and
provides estimates of the amount of
effort by survey type and location.
BOEM’s PEIS (BOEM, 2017) describes a
range of potential survey effort. The
levels of effort in the petition (which
form the basis for the modeling effort
described later in the Estimated Take
section) were the high-end estimates.
Following BOEM’s update of the
petition’s geographic scope, these
estimates were revised accordingly.
Actual total amounts of effort (including
by survey type and location) would not
be known in advance of receiving LOA
requests from industry operators, but
take in excess of what is analyzed for
this rulemaking would not be
authorized. As noted above, BOEM has
updated the scope of the specified
activity/specified geographical region by
removing the area currently under
leasing moratorium through GOMESA
from consideration. The removed area
largely covers the EPA, including areas
in which NMFS had proposed time-area
restrictions as mitigation, but also
includes a portion of the CPA.
Applicants seeking authorization for
take of marine mammals incidental to
survey activities within the GOMESA
area during the 5-year period of
effectiveness for this rule will need to
pursue a separate MMPA incidental take
authorization. See Figures 1 and 2.
Geophysical surveys are conducted to
obtain information on marine seabed
and subsurface geology for a variety of
reasons, including to: (1) Obtain data for
hydrocarbon and mineral exploration
and production; (2) aid in siting of oil
and gas structures, facilities, and
pipelines; (3) identify possible seafloor
or shallow depth geologic hazards; and
(4) locate potential archaeological
resources and benthic habitats that
should be avoided. In addition,
geophysical survey data inform Federal
government decisions. For example,
BOEM uses such data for resource
estimation and bid evaluation to ensure
that the government receives a fair
market value for OCS leases, as well as
to help to evaluate worst-case discharge
for potential oil-spill analysis and to
evaluate sites for potential hazards prior
to drilling.
Deep penetration seismic surveys
using airgun arrays as an acoustic
source (sound sources are described in
the ‘‘Detailed Description of Activities’’
section) are a primary method of
obtaining geophysical data used to
characterize subsurface structure. These
surveys are designed to illuminate
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deeper subsurface structures and
formations that may be of economic
interest as a reservoir for oil and gas
exploitation. A deep penetration survey
uses an acoustic source suited to
provide data on geological formations
that may be thousands of meters (m)
beneath the seafloor, as compared with
a shallow penetration or high resolution
geophysical (HRG) survey that may be
intended to evaluate shallow subsurface
formations or the seafloor itself (e.g., for
hazards).
Deep penetration surveys may be twodimensional (2D) or three-dimensional
(3D) (see Figure 1–2 of the petition), and
there are a variety of survey
methodologies designed to provide the
specific data of interest. 2D surveys are
designed to acquire data over large areas
(thousands of square miles) in order to
screen for potential hydrocarbon
prospectivity, and provide a crosssectional image of the structure. In
contrast, 3D surveys may use similar
acoustic sources but are designed to
cover smaller areas with greater
resolution (e.g., with closer survey line
spacing), providing a volumetric image
of underlying geological structures.
Repeated 3D surveys are referred to as
four-dimensional (4D), or time-lapse,
surveys that assess the depletion of a
reservoir.
Shallow penetration and highresolution surveys are designed to
highlight seabed and near-surface
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potential obstructions, archaeology, and
geohazards that may have safety
implications during rig installation or
well and development facility siting.
Shallow penetration surveys may use a
small airgun array, single airgun, or
similar sources, while high-resolution
surveys (which are limited to imaging
the seafloor itself) may use a variety of
sources, such as sub-bottom profilers,
single or multibeam echosounders, or
side-scan sonars.
Dates and Duration
The specified activities may occur at
any time during the five-year period of
validity of these regulations. Actual
dates and duration of individual surveys
are not known. Survey activities are
generally 24-hour operations. However,
BOEM estimates that a typical seismic
survey involves approximately 20 to 30
percent of non-operational downtime
due to a variety of factors, including
technical or mechanical problems,
standby for weather or other
interferences, and implementation of
mitigation measures.
Specified Geographical Region
The OCS planning areas are depicted
in Figure 1, and the overlap of the
GOMESA moratorium area with the
planning areas (as well as with the
modeling zones, see discussion of
modeling zones below) is depicted in
Figure 2, showing the updated specified
geographical region.
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Only the northern portion of the GOM
contains Federal waters. BOEM manages
development of U.S. Federal OCS
energy and mineral resources within
OCS regions, which are divided into
planning areas. Within planning areas
are lease blocks, on which specific
production activities may occur.
Geophysical survey activities may occur
on scales ranging from entire planning
areas to multiple or specific lease
blocks, or could occur at specific
potential or existing facilities within a
lease block. NMFS provided a detailed
discussion of the specified geographical
region in the notice of proposed
rulemaking (83 FR 29212; June 22,
2018).
The prospective survey activities may
occur in the U.S. waters of the GOM,
within BOEM’s Western, Central, and
Eastern GOM OCS planning areas
(approximately within the U.S. EEZ;
Figure 1), but excluding the GOMESA
moratorium area (Figure 2). Although
survey activity in the GOMESA
moratorium area is no longer being
considered, the region has not changed
compared with what was described, nor
has substantive new information
regarding the region become available.
Therefore, we do not reprint that
discussion here and refer the reader to
that notice of proposed rulemaking for
additional detail.
BILLING CODE 3510–22–P
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BILLING CODE 3510–22–C
Detailed Description of Activities
An airgun is a device used to emit
acoustic energy pulses into the seafloor,
and generally consists of a steel cylinder
that is charged with high-pressure air.
There are different types of airguns;
differences between types of airguns are
generally in the mechanical parts that
release the pressurized air, and the
bubble and acoustic energy released are
effectively the same. Airguns are
typically operated at a firing pressure of
2,000 pounds per square inch (psi).
Release of the compressed air into the
water column generates a signal that
reflects (or refracts) off the seafloor and/
or subsurface layers having acoustic
impedance contrast. Individual airguns
are available in different volumetric
sizes and, for deep penetration seismic
surveys, are towed in arrays (i.e., a
certain number of airguns of varying
sizes in a certain arrangement) designed
according to a given company’s method
of data acquisition, seismic target, and
data processing capabilities.
Airgun arrays are typically configured
in subarrays of 6–12 airguns each.
Towed hydrophone streamers
(described below) may follow the array
by 100–200 m and can be 5–12
kilometer (km) long. The airgun array
and streamers are typically towed at a
speed of approximately 4.5 to 5 knots
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(kn). BOEM notes that arrays used for
deep penetration surveys typically have
between 20–80 individual elements,
with a total volume of 1,500–8,460 in3.
The output of an airgun array is directly
proportional to airgun firing pressure or
to the number of airguns, and is
expressed as the cube root of the total
volume of the array.
Airguns are considered to be lowfrequency acoustic sources, producing
sound with energy in a frequency range
from less than 10 Hz to 2 kHz (though
there may be energy at higher
frequencies), with most energy radiated
at frequencies below 500 Hz.
Frequencies of interest to industry are
below approximately 100 Hz. The
amplitude of the acoustic wave emitted
from the source is equal in all directions
(i.e., omnidirectional) for a single
airgun, but airgun arrays do possess
some directionality due to phase delays
between guns in different directions.
Airgun arrays are typically tuned to
maximize functionality for data
acquisition purposes, meaning that
sound transmitted in horizontal
directions and at higher frequencies is
minimized to the extent possible.
When fired, a brief (∼0.1 second)
pulse of sound is emitted by all airguns
in an array nearly simultaneously, in
order to increase the amplitude of the
overall source pressure signal. The
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combined signal amplitude and
directivity is dependent on the number
and sizes of individual airguns and their
geometric positions within the array.
The airguns are silent during the
intervening periods, with the array
typically fired on a fixed distance (or
shot point) interval. The intervals are
optimized for water depth and the
distance of important geological features
below seafloor, but a typical interval in
relatively deep water might be
approximately every 10–20 seconds (or
25–50 m, depending on vessel speed).
The return signal is recorded by a
listening device, and later analyzed with
computer interpretation and mapping
systems used to depict the subsurface.
There must be enough time between
shots for the sound signals to propagate
down to and reflect from the feature of
interest, and then to propagate upward
to be received on hydrophones or
geophones. Reverberation of sound from
previous shots must also be given time
to dissipate. The receiving hydrophones
can be towed behind or in front of the
airgun array (may be towed from the
source vessel or from a separate receiver
vessel), or geophone receivers can be
deployed on the seabed. Receivers may
be displaced several kilometers
horizontally away from the source, so
horizontal propagation time is also
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considered in setting the interval
between shots.
Sound levels for airgun arrays are
typically modeled or measured at some
distance from the source and a nominal
source level then back-calculated.
Because these arrays constitute a
distributed acoustic source rather than a
single point source (i.e., the ‘‘source’’ is
actually comprised of multiple sources
with some predetermined spatial
arrangement), the highest sound levels
measurable at any location in the water
will be less than the nominal source
level. A common analogy is to an array
of light bulbs; at sufficient distance—in
the far field—the array will appear to be
a single point source of light but
individual sources, each with less
intensity than that of the whole, may be
discerned at closer distances (Caldwell
and Dragoset (2000) define the far field
as greater than 250 m). Therefore, backcalculated source levels are not
typically considered to be accurate
indicators of the true maximum
amplitude of the output in the far field,
which is what is typically of concern in
assessing potential impacts to marine
mammals. In addition, the effective
source level for sound propagating in
near-horizontal directions (i.e.,
directions likely to impact most marine
mammals in the vicinity of an array) is
likely to be substantially lower (e.g., 15–
24 decibels (dB); Caldwell and Dragoset,
2000) than the nominal source level
applicable to downward propagation
because of the directional nature of the
sound from the airgun array. The
horizontal propagation of sound is
reduced by noise cancellation effects
created when sound from neighboring
airguns on the same horizontal plane
partially cancel each other out.
Survey protocols generally involve a
predetermined set of survey, or track,
lines. The seismic acquisition vessel(s)
(source vessel) will travel down a linear
track for some distance until a line of
data is acquired, then turn and acquire
data on a different track. In some cases,
data is acquired as the source vessel(s)
turns continuously rather than moving
on a linear track (i.e., coil surveys). The
spacing between track lines and the
length of track lines can vary greatly,
depending on the objectives of a survey.
In addition to the line over which data
acquisition is desired, full-power
operation may include run-in and runout. Run-in is approximately 1 km of
full-power source operation before
starting a new line to ensure equipment
is functioning properly, and run-out is
additional full-power operation beyond
the conclusion of a trackline (e.g., half
the distance of the acquisition streamer
behind the source vessel, when used) to
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ensure that all data along the trackline
are collected by the streamer. Line turns
can require two to six hours when
towed hydrophones are used, due to the
long trailing streamers, but may be
much faster when streamers are not
used. Spacing and length of tracks
varies by survey. Survey operations
often involve the source vessel(s),
supported by a chase vessel. Chase
vessels typically support the source
vessel(s) by protecting the long
hydrophone streamer (when used) from
damage (e.g., from other vessels) and
otherwise lending logistical support
(e.g., returning to port for fuel, supplies,
or any necessary personnel transfers).
Chase vessels do not deploy acoustic
sources for data acquisition purposes;
the only potential effects of the chase
vessels are those associated with normal
vessel operations.
The general activities described here
could occur pre- or post-leasing and/or
on- or off-lease. Pre-lease surveys are
more likely to involve larger-scale
activity designed to explore or evaluate
geologic formations. Post-lease activities
may also include deep penetration
surveys, but would be expected to be
smaller in spatial and temporal scale as
they are associated with specific leased
blocks. Shallow penetration and HRG
surveys are more likely to be associated
with specific leased blocks and/or
facilities, with HRG surveys used along
pipeline routes and to search for
archaeological resources and/or benthic
communities. Specific types of surveys,
including 2D and 3D surveys and
various survey geometries typically
associated with 3D surveys (e.g.,
narrow- and wide-azimuth (NAZ and
WAZ) and coil surveys), were described
in summary in the notice of proposed
rulemaking (83 FR 29212; June 22,
2018). We also described surveys
involving the placement of seismic
sensors in a drilled well or borehole,
including various types of vertical
seismic profiling and other types of
borehole seismic surveys. For full detail,
please refer to that notice or sections 1.2
and 1.3 of BOEM’s petition.
Surveys may be designed as either
multi-source (i.e., multiple arrays towed
by one or more source vessel(s)) or
single source. Surveys may also be
differentiated by the way in which they
record the return signals using
hydrophones and/or geophones.
Hydrophones may be towed in
streamers behind a vessel (either the
source vessel(s) or a separate vessel) or
in some cases may be placed in
boreholes (called vertical seismic
profiling) or spaced at various depths on
vertical cables in the water column.
Sensors may also be incorporated into
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ocean-bottom cables (OBC) or
autonomous ocean-bottom nodes (OBN)
and placed on the seafloor—these
surveys are referred to generally as
ocean-bottom seismic (OBS).
Autonomous nodes can be tethered to
coated lines and deployed from ships or
remotely-operated vehicles, with
current technology allowing use in
water depths to approximately 3,000 m.
OBS surveys are most useful to acquire
data in shallow water and obstructed
areas, as well as for acquisition of fourcomponent survey data (i.e., including
pressure and 3D linear acceleration
collected via geophone). For OBS
surveys, one or two vessels usually are
needed to lay out and pick up cables,
one ship is needed to record data, one
ship tows an airgun array, and two
smaller utility boats support survey
operations.
In summary, 3D survey design
involves a vessel with one or more
acoustic sources covering an area of
interest with relatively tight spatial
configuration (compared with 2D
surveys). In order to provide richer,
more useful data, particularly in areas
with more difficult geology, survey
designs become more complicated with
additional source and/or receiver
vessels operating in potentially
increasingly complicated
choreographies.
As compared with 2D and 3D deep
penetration surveys, shallow
penetration and HRG surveys are
conducted to provide data informing
initial site evaluation, drilling rig
emplacement, and platform or pipeline
design and emplacement. Identification
of geohazards (e.g., gas hydrates, buried
channels) is necessary to avoid drilling
and facilities emplacement problems,
and operators are required to identify
and avoid archaeological resources and
certain benthic communities. These
surveys may use single airguns or small
airgun arrays, but generally use various
types of electromechanical acoustic
sources. Please see our notice of
proposed rulemaking or BOEM’s
petition for additional detail regarding
these survey types and
electromechanical acoustic sources.
Summary of Representative Sound
Sources
Because the specifics of acoustic
sources to be used cannot be known in
advance of receiving LOA requests from
industry operators, it was necessary to
define representative acoustic source
parameters, as well as representative
survey patterns. BOEM determined
realistic representative proxy sound
sources and survey patterns, which
were used in acoustic exposure
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modeling and more broadly to support
the analysis, after discussions with
individual geophysical companies.
Acoustic exposure modeling is
described in detail in ‘‘Acoustic
Propagation and Marine Mammal
Exposure Modeling of Geological and
Geophysical Sources in the Gulf of
Mexico’’ and ‘‘Addendum to Acoustic
Propagation and Marine Mammal
Exposure Modeling of Geological and
Geophysical Sources in the Gulf of
Mexico’’ (Zeddies et al., 2015, 2017a),
hereafter referred to collectively as ‘‘the
modeling report,’’ as well as in ‘‘Gulf of
Mexico Acoustic Exposure Model
Variable Analysis’’ (Zeddies et al.,
2017b), which evaluated a smaller,
alternative airgun array. The reports are
available online at:
www.fisheries.noaa.gov/action/
incidental-take-authorization-oil-andgas-industry-geophysical-surveyactivity-gulf-mexico.
Representative sources for the
modeling include a single airgun, an
airgun array, and multiple
electromechanical sources. Two major
survey types were considered: Largearea seismic (including 2D, 3D NAZ, 3D
WAZ, and coil surveys) and small-area,
high-resolution geotechnical (including
single airgun surveys and surveys using
a CHIRP sub-bottom profiler in
combination with multibeam
echosounder and side-scan sonar; the
single airgun was used as a reasonable
proxy for surveys using a boomer). The
nominal airgun sources used for
analysis of the proposed action include
a small single airgun (90 in3 airgun) and
a large airgun array (8,000 in3). In
addition, the supplemental Model
Variable Analysis (Zeddies et al., 2017b)
provides analysis of an alternative 4,130
in3 array (see Letters of Authorization
section). We note that while highresolution geophysical sources were
conservatively included for
consideration in this rule to allow for
take authorization if necessary, some of
these types of sources would not
necessarily be expected to cause the
incidental take of marine mammals,
depending on the source type and/or the
manner in which it is operated (e.g.,
operational settings, mitigation
measures), and Letters of Authorization
would not be necessary in those cases.
Additional characteristics of the
representative acoustic sources and
representative operational parameters of
the different survey types that were
used in the modeling simulations to
predict the exposure of marine
mammals to different received levels of
sound are described in the modeling
report and in our notice of proposed
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rulemaking. Please see those documents
for additional detail.
We note that while it was necessary
to identify representative sources for the
purposes of modeling the number of
takes to be included in the analysis
under the rule, the analysis is intended
to be, and is appropriately, applicable to
takes resulting from the use of other
sizes or configurations of airguns (e.g.,
the alternative, smaller airgun array
modeled in the ‘‘Gulf of Mexico
Acoustic Exposure Model Variable
Analysis’’ report (Zeddies et al., 2017b)
referenced in the proposed rule and
available for public review as
supplementary material to the proposed
rule).
While these descriptions reflect
existing technologies and current
practice, new technologies and/or uses
of existing technologies may come into
practice during the period of validity of
these regulations. NMFS will evaluate
any such developments on a casespecific basis to determine whether
expected impacts on marine mammals
are consistent with those described or
referenced in this document and,
therefore, whether any anticipated take
incidental to use of those new
technologies or practices may
appropriately be authorized under the
existing regulatory framework. We also
note here that activities that may result
in incidental take of marine mammals,
and which would therefore
appropriately require authorization
under the MMPA, are not limited to
those activities requiring permits from
BOEM. There may be some activities
that do not require permits from BOEM,
such as certain ancillary activities, for
which an LOA under this rule may be
appropriate. Operators should consult
NMFS regarding the appropriateness of
applying for an LOA under this rule
prior to conducting such activities.
Estimated Levels of Effort
As noted previously, actual total
amounts of effort by survey type and
location cannot be known in advance of
receiving LOA requests from industry
operators. Therefore, BOEM’s PEIS
provided projections of survey level of
effort for the different survey types for
a 10-year period (and BOEM’s updated
scope refined those projections to a fiveyear period). In order to construct a
realistic scenario for future geophysical
survey effort, BOEM evaluated trends in
permit applications as well as industry
estimates of future survey activity. In
addition, GOMESA precludes leasing,
pre-leasing, or any related activity
(though not geophysical surveys) in the
GOM east of 86°41′ W, in BOEM’s
Eastern Planning Area (EPA) and within
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125 mi (201 km) of Florida, or in
BOEM’s Central Planning Area (CPA)
and within 100 mi of Florida (and
according to certain other detailed
stipulations). These leasing restrictions
are in place until June 30, 2022. On
September 8, 2020, the President
effectively extended this moratorium
through withdrawal under OCSLA of
the same area covered by the GOMESA
moratorium from disposition by leasing
for 10 years, beginning on July 1, 2022,
and ending on June 30, 2032. This
withdrawal prevents consideration of
these areas for any leasing for purposes
of exploration, development, or
production during the 10-year period
beginning on July 1, 2022, and ending
on June 30, 2032. Although the
withdrawal does not preclude
geophysical survey activity, similar to
the moratorium under GOMESA, the
lack of leasing opportunities may be
expected to curtail interest in
exploratory surveys to some degree.
In order to provide some spatial
resolution to the projections of survey
effort and to provide reasonably similar
areas within which acoustic modeling
might be conducted, the geographic
region was divided into seven zones,
largely on the basis of water depth,
seabed slope, and defined BOEM
planning area boundaries. Shelf regions
typically extend from shore to
approximately 100–200 m water depths
where bathymetric relief is gradual (off
Florida’s west coast, the shelf extends
approximately 150 km). The slope starts
where the seabed relief is steeper and
extends into deeper water. In the GOM
water deepens from 100–200 m to
1,500–2,500 m over as little as a 50 km
horizontal distance. As the slope ends,
water depths become more consistent,
though depths can vary from 2,000–
3,300 m. Three primary bathymetric
areas were defined as shelf (0–200 m
water depth), slope (200–2,000 m), and
deep (>2,000 m).
Available information regarding
cetacean density in the GOM (e.g.,
Roberts et al., 2016) shows that, in
addition to water depth, animal
distribution tends to vary from east to
west in the GOM and appears correlated
with the width of shelf and slope areas
from east to west. The western region is
characterized by a relatively narrow
shelf and moderate-width slope. The
central region has a moderate-width
shelf and moderate-width slope, and the
eastern region has a wide shelf and a
very narrow slope. Therefore, BOEM’s
western, central, and eastern planning
area divisions provide appropriate
longitudinal separations for the shelf
and slope areas. Due to relative
consistency in both physical properties
E:\FR\FM\19JAR2.SGM
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and predicted animal distribution, the
deep area was not subdivided. As
shown in Figure 3, Zones 1–3 represent
the shelf area (from east to west), Zones
BILLING CODE 3510–22–C
provided revised 5-year level of effort
predictions and associated acoustic
exposure estimates. BOEM’s process for
developing this information, described
in detail in ‘‘Revised Modeled Exposure
Estimates,’’ available online, was
straightforward. Rather than using the
PEIS’s 10-year period, BOEM provided
revised levels of effort for a 5-year
period, using Years 1–5 of the original
level of effort projections. BOEM stated
that the first five years were selected to
be carried forward ‘‘because they were
contiguous, they included the three
years with the most activity, and they
were the best understood in relation to
the historical data upon which they are
based.’’ NMFS concurs with this choice.
Levels of effort were revised based on
the basic assumption that if portions of
areas are removed from consideration,
then the corresponding effort previously
presumed to occur in those areas also is
removed from consideration. Revised
estimates of future effort and associated
Table 1 in the notice of proposed
rulemaking provided the 10-year
estimated levels of effort from BOEM’s
PEIS, estimated as 24-hr survey days,
including annual totals by survey type
and by zone for deep penetration and
shallow penetration surveys,
respectively. As the basis for the
analysis supporting the proposed
rulemaking, NMFS selected one high
survey effort scenario and two each of
moderate and low survey effort
scenarios from the ten survey effort
scenarios provided by BOEM. Of the ten
‘‘years’’ or effort scenarios, Year 1
(high), Years 4 and 5 (moderate), and
Years 8 and 9 (low) were selected as
representative effort scenarios and
carried forward for further evaluation.
However, as noted previously, BOEM
subsequently revised its proposed
action by removing the area subject to
leasing moratorium under GOMESA
from consideration in the rule. In
support of this revision, BOEM
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4–6 represent the slope area (from east
to west), and Zone 7 is the deep area.
BILLING CODE 3510–22–P
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Sfmt 4700
acoustic exposures draw upon the prior
projections and modeling approach,
which were subject to notice and
comment. Table 1 shows the percentage
reduction in survey area for each
modeling zone that results from BOEM’s
scope revisions, and Table 2 provides
the subsequent revised level of effort
projections for the 5-year period.
TABLE 1—PERCENTAGE REDUCTION IN
SURVEY AREA FOR EACH MODELED
ZONE
Modeling zone
1
2
3
4
5
6
7
............................................
............................................
............................................
............................................
............................................
............................................
............................................
E:\FR\FM\19JAR2.SGM
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Percentage
reduction
in area
100.0
2.7
0.0
98.2
4.0
0.0
33.0
ER19JA21.002</GPH>
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TABLE 2—PROJECTED LEVELS OF EFFORT IN 24-HR SURVEY DAYS FOR FIVE YEARS, BY ZONE AND SURVEY TYPE 1
Year
Zone 2
2D 3
3D NAZ 3
3D WAZ 3
Coil 3
Total
(deep) 3
VSP 3
Shallow
hazards 4
Boomer 4
Total
(shallow) 4
HRG 4
1 ......................
1
2
3
4
5
6
7
0
0
0
0
2
0
23
0
7
0
0
16
0
170
0
0
0
0
8
0
82
0
0
0
0
3
0
35
0
0
0
0
0
0
1
0
7
0
0
29
0
311
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
0
0
1
0
11
1
1
0
0
1
0
11
Total .........
..................
25
193
90
38
1
347
0
0
14
14
2 ......................
1
2
3
4
5
6
7
0
0
0
27
0
0
10
0
10
0
0
16
0
166
0
1
0
0
8
0
79
0
0
0
0
3
0
34
0
0
0
0
0
0
1
0
11
0
27
27
0
290
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
0
0
1
0
11
1
1
0
0
1
0
11
Total .........
..................
37
192
88
37
1
355
0
0
14
14
3 ......................
1
2
3
4
5
6
7
0
0
0
54
1
0
31
0
10
0
50
10
0
125
0
1
0
21
4
0
46
0
0
0
9
2
0
20
0
0
0
0
0
0
1
0
11
0
134
17
0
223
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
1
1
0
12
1
0
0
1
1
0
12
Total .........
..................
86
195
72
31
1
385
0
0
12
12
4 ......................
1
2
3
4
5
6
7
0
0
0
54
1
0
31
0
10
0
50
10
0
125
0
1
0
21
4
0
46
0
0
0
9
2
0
20
0
0
0
0
0
0
1
0
11
0
134
17
0
223
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
0
12
0
0
0
1
1
0
12
Total .........
..................
86
195
72
31
1
385
0
0
14
14
5 ......................
1
2
3
4
5
6
7
0
0
0
0
0
0
0
0
7
0
75
12
0
154
0
0
0
0
8
0
79
0
0
0
0
3
0
34
0
0
0
0
0
0
1
0
7
0
75
23
0
268
0
0
0
0
0
0
1
0
0
0
0
0
0
1
0
1
0
0
1
0
11
0
1
0
0
1
0
13
Total .........
..................
0
248
87
37
1
373
1
1
13
15
1 Projected
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levels of effort in 24-hr survey days.
2 Zones follow the zones depicted in Figure 3.
3 Deep penetration survey types include 2D, which uses one source vessel with one large array (8,000 in3); 3D NAZ, which uses two source vessels using one
large array each; 3D WAZ and coil, each of which uses four source vessels using one large array each (but with differing survey design); and VSP, which uses one
source vessel with a large array. ‘‘Deep’’ refers to survey type, not to water depth.
4 Shallow penetration/HRG survey types include shallow hazards surveys, assumed to use a single 90 in3 airgun or boomer, and high-resolution surveys using the
multibeam echosounder, side-scan sonar, and chirp sub-bottom profiler systems concurrently. ‘‘Shallow’’ refers to survey type, not to water depth.
This description of the specified
activity is a summary of critical
information. The interested reader
should refer to the notice of proposed
rulemaking (83 FR 29212; June 22,
2018), as well as BOEM’s petition (with
recent addenda) and PEIS, for additional
detail regarding these prospective
activities and the region. Required
mitigation, monitoring, and reporting
measures are described in detail later in
this document (please see Mitigation
and Monitoring and Reporting).
Changes From the Proposed Rule
This section provides a summary of
changes from the proposed rule. Each
section in which changes were made
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(e.g., Mitigation) includes a more
detailed list of changes made and a
fuller description of the rationale. The
following Comments and Responses
section also provides additional detail
relating to changes, in cases where the
change resulted from a public comment.
Most notably, as described in greater
detail above, BOEM updated the scope
of the specified activity/specified
geographical region that is the subject of
this rule by removing from
consideration the area that is subject to
the GOMESA leasing moratorium. In
accordance with this updated spatial
scope, BOEM provided revised activity
level projections and revised estimated
acoustic exposure numbers based on the
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same modeling that informed the
numbers evaluated in the proposed rule.
BOEM’s revised activity level
projections correspond with Years 1–5
of the original 10-year projections (see
Table 1 of the notice of proposed
rulemaking), which is a conservative
choice as these years contained higher
levels of effort than Years 6–10. In the
proposed rule, NMFS selected years that
were representative of different levels of
effort as the basis for the total taking
over five years, including one year of
relatively high effort (Year 1), two years
of relatively moderate effort (Years 4
and 5), and two years of relatively low
effort (Years 8 and 9). This selection is
now in part supplanted (with the two
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representative ‘‘low effort’’ years
replaced by one relatively high effort
year and one relatively moderate effort
year) by BOEM’s selection of Years 1–
5 and the associated updated levels of
effort.
The revised acoustic exposure
numbers form the basis for our analyses
in this final rule. Of note, the maximum
total taking, as well as the annual
maximum, that would be allowable
under the regulations has decreased for
most species and stocks, with the
exception of the annual maximums for
Atlantic spotted dolphin and bottlenose
dolphins, and the total taking over five
years for the Atlantic spotted dolphin,
which have increased slightly (please
see Estimated Take for additional
information). These changes (largely
decreases) in the take numbers do not
have a meaningful effect on the analysis
(except where impacts are significantly
reduced, e.g., for Bryde’s whales) and do
not change any of the findings.
In the proposed rule, NMFS included
several time-area restrictions, including
a seasonal restriction on airgun survey
activity in the ‘‘Bryde’s whale core
habitat’’ area (as well as alternatives to
this proposal that were offered for
public comment, including a year-round
restriction in the same area). Following
BOEM’s update to the scope of the rule,
two of these areas (the Bryde’s whale
area and the ‘‘Dry Tortugas’’ area that
was, in part, designed to provide
protection for sperm whales and beaked
whales) were removed from
consideration, as the specified activity/
specified geographical region no longer
includes surveys in the areas where
these proposed restrictions are located.
A third time-area restriction—the
‘‘Coastal Restriction,’’ designed to
protect bottlenose dolphins in coastal
waters most heavily impacted by the
Deepwater Horizon oil spill—has been
modified in consideration of public
comments. The restriction was proposed
to be GOM-wide within coastal waters
inside the 20-m isobath, and to be in
effect from February through May. The
area encompassed by the restriction has
been reduced to match the assumed
range of the northern coastal stock of
bottlenose dolphins (i.e., between 90–
84° W, but in effect only to the eastern
extent of the coastal waters portion of
BOEM’s updated specified geographic
region) while the temporal window has
been expanded to include January. In
addition, a proposed 13-km buffer to
this area has been removed.
In the proposed rule, NMFS defined
‘‘deep penetration’’ surveys as those
using arrays greater than 400 in3 total
volume. That delineation has been
revised to include surveys using arrays
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greater than 1,500 in3 total volume, with
arrays of 1,500 in3 total volume and less
considered ‘‘shallow penetration’’
surveys.
In the notice of proposed rulemaking,
NMFS proposed an exception to the
general shutdown requirements for
certain species of dolphins in relation to
airgun surveys, in which the acoustic
source would be powered down to the
smallest single element of the array.
Power-down conditions would be
maintained until the animal(s) is
observed exiting the exclusion zone or
for 15 minutes beyond the last
observation of the animal, following
which full-power operations may be
resumed without ramp-up. NMFS also
provided an alternative proposal for
consideration by the public, in which
no shutdown or power-down would be
required upon observation of the same
species of dolphins. Following review of
public comments, NMFS removes the
power-down measure for small
delphinids, in favor of the no-shutdown
and no power-down alternative. No
shutdown or power-down is required
for these species.
NMFS proposed a number of
extended distance shutdown
requirements on the basis of detections
of certain species deemed particularly
sensitive (e.g., beaked whales) or of
particular circumstances deemed to
warrant the extended distance
shutdown requirement (e.g., whales
with calves). These extended distance
shutdowns were all conditioned upon
observation or detection of these species
or circumstances ‘‘at any distance’’ from
the vessel. However, NMFS also
included as an alternative proposal for
public consideration a distance limit of
1,000 m for these shutdown
requirements. Following review of
public comments, NMFS determined
that a distance limit on extended
shutdown zones for relevant species or
circumstances was appropriate, but
determined 1,500 m was the appropriate
distance (rather than 1,000 m).
The proposed rule included an
extended distance shutdown for sperm
whales that was applicable upon
acoustic detection, but was not
applicable to visual detection.
Following review of public comments,
the shutdown requirement has been
expanded to include any detection of
sperm whales within the extended
distance shutdown zone, including
visual detection.
For shallow penetration surveys,
NMFS reduces the standard exclusion
zone from 200 m to 100 m, while
including an extended distance
shutdown requirement mirroring the
requirements for deep penetration
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5331
surveys, but within a distance of 500 m.
NMFS eliminates shutdown
requirements for HRG surveys (defined
here as surveys using electromechanical
sources such as multi-beam
echosounders, side-scan sonars, and
chirp sub-bottom profilers). The
proposed regulations required
shutdown for marine mammals within
the proposed exclusion zone for surveys
operating in water depths greater than
200 m.
NMFS eliminates proposed
requirements for visual observation
during nighttime ramp-up and preclearance, and for the use of third-party
PSOs aboard node retrieval vessels.
In the proposed rule, NMFS discussed
the use of an extrapolation method
recommended by the Marine Mammal
Commission for use in estimating
potential unobserved takes. NMFS
agrees with public commenters that the
appropriateness of the method for
application to observations conducted
from working source vessels (versus
research vessels) is unknown and, as
suggested through public comment,
NMFS will not require use of this
method but will continue to evaluate
approaches for assessment of effects to
marine mammal stocks, including those
based on extrapolation of marine
mammal detections, through the
adaptive management process and
subsequently apply them through LOAs
as appropriate.
NMFS has revised requirements
relating to reporting of injured or dead
marine mammals and has added newly
crafted requirements relating to actions
that should be taken in response to
notification of live stranding events in
certain circumstances, in order to reflect
current best practice.
The proposed rule indicated that LOA
applications with take estimates based
on modeling other than that specifically
included in the modeling report used to
support the EIS and the proposed rule
(the modeling report; Zeddies et al.,
2015, 2017a) would necessarily be
published for public comment prior to
the issuance of an LOA. Upon
consideration of public comment and
related supplemental materials, the final
rule more flexibly allows that if
applicants do not use the modeling
provided by the rule, NMFS will
publish a notice in the Federal Register
soliciting public comment, when the
model or inputs differ substantively
from those that have been reviewed by
NMFS and the public previously. Please
see the Letters of Authorization section
for more detail.
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Comments and Responses
NMFS published a notice of proposed
rulemaking in the Federal Register on
June 22, 2018 (83 FR 29212), beginning
a 60-day comment period. In that notice,
we requested public input on the
proposed rule and regulations,
including the variations of the proposed
rule, two economic baselines, and other
information provided in the Regulatory
Impact Analysis and associated
appendices, and requested that
interested persons submit relevant
information, suggestions, and
comments. In response to BOEM’s
change in scope and in consideration of
public comments, we modified our
action, as discussed in the following
responses to comments. Please also see
the Changes from the Proposed Rule
section, above. We note that one area of
significant concern for some members of
the public was potential impacts to
Bryde’s whales and related mitigation
measures. The reduced geographic
scope eliminates the need to consider
activity in the Bryde’s whale ‘‘core
habitat area’’ and eliminates the
majority of the incidental take of
Bryde’s whale that was evaluated in the
proposed rule.
During the 60-day comment period,
we received 17 comment letters. A letter
was submitted jointly by the
International Association of
Geophysical Contractors, the American
Petroleum Institute, the National Ocean
Industries Association, and the Offshore
Operators Committee (hereafter, the
‘‘Associations’’). A separate letter was
submitted jointly by the Natural
Resources Defense Council (NRDC),
Center for Biological Diversity,
Earthjustice, Gulf Restoration Network,
Humane Society Legislative Fund, The
Humane Society of the United States,
and Sierra Club (hereafter, ‘‘NRDC’’).
Additional letters were submitted by the
following: BP Exploration & Production
Inc. (BP), Consumer Energy Alliance,
CGG, Chevron USA Inc. (Chevron), the
Center for Regulatory Effectiveness
(CRE), the Florida Department of
Environmental Protection, the Marine
Mammal Commission (MMC), and eight
private citizens. NMFS has reviewed all
public comments received on the
proposed rulemaking. All relevant
comments and our responses are
described below, with comment
responses outlined by major categories.
All comments received are available
online at: www.regulations.gov. A direct
link to these comments is provided at:
www.fisheries.noaa.gov/action/
incidental-take-authorization-oil-andgas-industry-geophysical-surveyactivity-gulf-mexico.
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General Comments
As an initial matter, we note that
under the MMPA, NMFS generally does
not have discretion regarding issuance
of requested incidental take
authorizations for small numbers of
marine mammals, provided that (1) the
total taking associated with a specified
activity will have a negligible impact on
the affected species or stock(s); (2) the
total taking associated with a specified
activity will not have an unmitigable
adverse impact on the availability of the
species or stock(s) for subsistence uses
(not relevant here); and (3) mitigation,
monitoring, and reporting of such
takings are set forth, including
mitigation measures sufficient to meet
the standard of least practicable adverse
impact on the affected species or stocks
and their habitat.
In addition, NMFS’ proposed action—
the issuance of the ITR and any
subsequent LOAs authorizing incidental
take of marine mammals—addresses
only marine mammals (and their
habitat). As such, effects of the surveys
on other aspects of the marine
environment are not relevant to NMFS’
analyses under the MMPA.
The MMPA does require that we
evaluate potential effects to marine
mammal habitat, which includes prey
species (e.g., zooplankton, fish, squid).
However, consideration of potential
effects to taxa other than marine
mammals and their prey, or
consideration of effects to potential prey
species in a context other than the
import of such effects on marine
mammals, is not relevant to our action
under the MMPA. We have
appropriately considered effects to
marine mammal habitat. Separately,
BOEM evaluated effects to all relevant
aspects of the human environment
(including marine mammals and other
taxa) through the analysis presented in
BOEM’s PEIS (available online at:
www.boem.gov/Gulf-of-MexicoGeological-and-Geophysical-ActivitiesProgrammatic-EIS/), and effects to all
potentially affected species that are
listed under the Endangered Species Act
(ESA) and any critical habitat
designated for those species were
addressed through consultation between
BOEM and NMFS pursuant to section 7
of the ESA. That Biological Opinion,
which evaluated NMFS’ proposed
action (issuance of the ITR and any
subsequent LOAs) as well as all BOEM
and Bureau of Safety and Environmental
Enforcement (BSEE) approvals of
activities associated with the OCS oil
and gas program in the GOM, is
available online at:
www.fisheries.noaa.gov/national/
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endangered-species-conservation/
biological-opinions-issued-noaafisheries-office-protected. We do not
further address taxa other than marine
mammals and marine mammal prey.
Comment: The Associations comment
that the proposed ITR is a wellstructured and thorough document that
appropriately concludes that
geophysical activities in the GOM
would have no more than a negligible
impact on marine mammal populations,
and that they appreciate NMFS’ effort in
preparing the proposed ITR and
consideration of some of the
Associations’ previous comments.
Response: NMFS appreciates the
comment.
Comment: The Associations comment
that geophysical surveys play a critical
role in the safe and orderly development
of the oil and gas resources of the GOM.
Response: We acknowledge the
background operational information
provided by the Associations.
Comment: BP comments that the ITR
is a much-needed process to govern the
authorization of incidental takes of
marine mammals associated with
geophysical survey activity in the GOM.
Chevron also indicates support for
promulgation of the ITRs.
Response: NMFS appreciates the
comments.
Comment: BP comments that
projected survey efforts are
underestimated but did not provide
specific justification or
recommendations.
Response: Projected levels of survey
effort were formulated by BOEM and
included in their PEIS. BOEM’s PEIS
stated, ‘‘the scenarios contain
projections based on the analysis of
recent historic activity levels and trends
made by BOEM’s subject-matter experts
who also considered industry-projected
activity levels in their estimates.’’ These
projected levels of survey effort were
made available for public review on
multiple occasions during the
development of the PEIS, as well as
during the notice of receipt comment
period, in which the public was given
the opportunity to review and comment
on the petition itself (81 FR 88664;
December 8, 2016). Neither BP nor other
industry stakeholders submitted
comments on the BOEM-developed
effort levels, and no evidence was
provided that projected survey efforts
are underestimated. The projected levels
of effort were subsequently updated by
BOEM based on the removal of the
GOMESA area from consideration.
Comment: The Florida Department of
Environmental Protection (FLDEP)
expressed its concern regarding the
potential impacts of OCS oil and gas
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activities on marine and coastal
environments and the biological
resources and critical habitats
associated with them. The FLDEP also
indicated that former Secretary of the
Interior Zinke had made a commitment
to former Governor Scott to remove the
State of Florida from future
consideration for offshore drilling.
Response: NMFS acknowledges the
comments. Assuming that the
requirements of the MMPA are met, e.g.,
findings of negligible impact and small
numbers are made, NMFS does not have
discretion as to whether it may issue
ITRs and LOAs under those ITRs, and
NMFS has no authority to limit oil and
gas activities outside of prescribing
appropriate mitigation requirements.
Marine Mammal Impacts
Comment: The Associations (as well
as other industry commenters and the
CRE) stated, in summary, that there is
no scientific evidence that geophysical
survey activities have caused adverse
consequences to marine mammal stocks
or populations, and that there are no
known instances of injury to individual
marine mammals as a result of such
surveys, stating that similar surveys
have been occurring for years without
significant impacts. The Associations
stated that surveys have been ongoing in
the GOM for years and have not resulted
in any negative impacts to marine
mammals, including reducing fitness in
individuals or populations. Referring to
other regions, the commenters stated
that bowhead whale numbers have
increased in the Arctic despite survey
activity. The Associations go further in
claiming that ‘‘NMFS misconstrues its
legal obligations’’ and ‘‘NMFS violates
the MMPA’s best available science
requirement.’’
Response: Disruption of behavioral
patterns (i.e., Level B harassment) has
been documented numerous times for
marine mammals in the presence of
airguns, in the form of avoidance of
areas, notable changes in vocalization or
movement patterns, or other shifts in
important behaviors. See Potential
Effects of the Specified Activity on
Marine Mammals and Their Habitat in
the notice of proposed rulemaking. In
addition, there is growing scientific
evidence demonstrating the connections
between sub-lethal effects, such as
behavioral disturbance, and populationlevel effects on marine mammals (e.g.,
Lusseau and Bedjer, 2007; New et al.,
2014; Pirotta et al., 2018). Disruptions of
important behaviors, in certain contexts
and scales, have been shown to have
energetic effects that can translate to
reduced survivorship or reproductive
rates of individuals (e.g., feeding is
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interrupted, so growth, survivorship, or
ability to bring young to term may be
compromised), which in turn can
adversely affect populations depending
on their health, abundance, and growth
trends.
With specific regard to sound, as a
2017 report from the National Academy
of Sciences noted, while it is true that
‘‘[n]o scientific studies have
conclusively demonstrated a link
between exposure to sound and adverse
effects on a marine mammal
population,’’ this is largely because such
impacts are very difficult to demonstrate
(NRC, 2005; NAS, 2017), not because
they do not exist. Population-level
effects are inherently difficult to assess
because of high variability, migrations,
and multiple factors affecting the
populations. Appropriate studies are
exceedingly difficult to carry out, and
no appropriate study and reference
populations have yet been established.
Nonetheless there is a growing body of
literature and science illustrating the
connections between prolonged
behavioral disturbance and impacts to
reproductive success and survivorship.
Accordingly, it is not defensible to
conclude that sub-lethal acoustic
stressors cannot have population level
consequences. Based on the available
evidence, a sufficient analysis of the
potential impacts of airgun noise
requires consideration of impacts on
individuals and the potential for
population level effects. NMFS has
carefully considered the available
evidence in making the necessary
determinations (see Negligible Impact
Analysis and Determinations) and
determining the most appropriate suite
of mitigation measures.
Because some commenters repeatedly
cite (and misunderstand) public
statements by BOEM in support of a
contention that there is ‘‘no harm from
seismic,’’ we clarify the record by citing
BOEM’s own responses to similar
comments on their PEIS (BOEM, 2017).
BOEM stated: ‘‘It is critically important
to understand that BOEM’s . . . Science
Note . . . refers to impacts on marine
mammal . . . population sustainability
rather than effects on individual
animals. Studies have shown that
marine mammals may and do react to
sound through physical displacement
from or avoidance of the area of
ensonification and/or by altering their
vocalizations. This [PEIS] acknowledges
that significant acute physical injury to
or death of marine mammals is not
likely to be a direct result of seismic
noise. It does, however, acknowledge
that sublethal injurious effects are
possible and may, over time, result in
the eventual death of the individual(s)
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from these physical injuries and/or loss
of hearing with (as in the case of marine
mammals) the resultant inability to
forage and communicate with
conspecifics. Another prominent
concern is whether anthropogenic
sounds such as those generated during
seismic survey activities may ‘‘mask’’
communications between some marine
mammals. Depressed survival rates
related to energetic effects or other
impacts of noise are difficult to
determine. BOEM, however, does not
assume that lack of demonstrated
adverse population-level effects from
seismic surveys means that those effects
may not occur.’’
In support of assertions that there are
‘‘no effects’’ to marine mammals from
seismic surveys and that there is a ‘‘lack
of any harm’’ to marine mammals, CRE
cites statements made by NMFS, in
which we conclude that there is no
evidence that serious injury, death, or
stranding is reasonably likely to occur
as a result of such surveys, and that
Level A harassment is not reasonably
likely to occur for mid-frequency
cetaceans. CRE’s assertion that there are
‘‘no effects’’ and ‘‘no harm’’ to marine
mammals as a result of seismic surveys
is based on the fact that marine
mammals still exist in the GOM despite
survey activity. CRE overlooks the
evidence put forward for Level B
harassment, and the potential effects of
behavioral disruption, as well as the
additional effects of noise that do not
rise to the level of a take, but which
nevertheless must be considered when
evaluating the effects of a specified
activity on a species or stock.
The Associations assert that we
premise our decisions on the idea that
we must act conservatively because
effects that have not been conclusively
proven—which the Associations claim,
without evidence, do not and cannot
occur—could occur in the future. The
Associations state that we misconstrue
our legal obligations via the application
of ‘‘an additional layer of precautionary
bias’’ beyond that established in the
MMPA standards themselves, though
they do not demonstrate that the bias
exists. The Associations acknowledge
that the MMPA requires mitigation
sufficient to meet the standard of least
practicable adverse impact. Therefore,
some portion of the mitigation
requirements contained in the proposed
ITR would be necessary to meet that
standard. However, they provide no
analysis to support the contention that
specific mitigation requirements exceed
that standard. In fact, we have declined
to adopt the recommendations of other
commenters that are based on vague and
unexplained standards of
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‘‘conservatism’’ that are not required in
the MMPA. Here, we conducted the
requisite analyses of mitigation and
found that the requirements contained
in this final ITR, as modified on the
basis of new information and review of
public comments, meet the least
practicable adverse impact (LPAI)
standard.
We base our conclusions, relating to
the potential effects of the specified
activity on the affected species and
stocks, on reasonable interpretation of
the available science, which we
summarize in this preamble and
described in detail in our notice of
proposed rulemaking. While we
acknowledge the lack of conclusive
evidence for population-level
consequences, this is an artifact of the
extreme difficulty of empirically
demonstrating such effects (as
concluded by the National Academies of
Science, stated above). The best
available scientific information provides
considerable evidence that the activities
evaluated in this ITR have the potential
to adversely affect the fitness of
individual animals. The best available
science clearly demonstrates that, given
adverse impacts to an animal’s fitness,
population-level effects are plausible.
The Associations’ comments on this
topic treat the lack of empirical
evidence as evidence that such effects
do not occur. However, NMFS does not
agree that absence of evidence is
evidence of absence of effects. The
comments further incorrectly frame our
decision-making as being premised on
the idea that such effects could occur in
the future, when they are actually based
on a reasonable interpretation of the
best available scientific information
regarding what the effects of the
specified activity are likely to be in the
absence of prescribed mitigation.
Despite the paucity of empirical
research on population effects, the best
available information demonstrates
impacts at the individual level that, at
a high enough level of take, have
reasonably foreseeable population-level
impacts.
Similarly, the Associations imply that
our interpretation of the existing
scientific information reflects
speculation about what future research
might demonstrate. The Associations’
statements that NMFS dismissed current
scientific findings and premised
decisions on hypothesized future
impacts are inaccurate, and their
assertion that NMFS ‘‘has effectively
required conclusive scientific proof that
seismic surveys do not impact marine
mammal populations’’ misunderstands
NMFS’ use of the scientific literature.
The best available information
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demonstrates that the effects of seismic
surveys on marine mammals may
include adverse impacts on behavior in
ways that can also have energetic
consequences. To draw different
conclusions regarding the need for the
strong suite of mitigation requirements
included in this final ITR, NMFS would
require scientific evidence that
demonstrates that seismic surveys do
not have energetic consequences or,
alternatively, do not reach a point where
there are population-level
consequences. NMFS is not aware of
such evidence. NMFS’ final rule is
based on the best available scientific
information and the requirements of the
MMPA.
Chevron states that we do not account
for ‘‘real-world’’ protected species
observer (PSO) observations, calling this
‘‘arbitrary and capricious,’’ and seems to
imply that these ‘‘ignored’’ PSO
observations of marine mammals are
evidence that seismic activities produce
no more than ‘‘negligible effects on
species.’’ Chevron does not provide
evidence to support its comment or
otherwise develop the suggestion to
enable a specific response. However, we
incorporated the best available scientific
information for our analysis, as
evidenced (for example) by our
references in the notice of proposed
rulemaking to BOEM’s synthesis study
of PSO data from 2002–08 (Barkaszi et
al., 2012) (as well as other similar
syntheses from other locations). In this
final rulemaking, we have incorporated
analysis of a newly available study of
PSO data from 2009–15 (Barkaszi and
Kelly, 2018). These data are also key to
the evaluation of direct costs found in
our RIA. We disagree with Chevron’s
apparent contention that we ‘‘ignore[d]’’
BOEM’s earlier ‘‘admissions that no
scientific evidence exists contradicting
the real-world observations of negligible
impact’’ (citing to BOEM’s ‘‘Science
Notes’’). NMFS addressed BOEM’s
‘‘Science Notes’’ in some detail in our
notice of proposed rulemaking (83 FR
29264–65). Chevron misinterprets a
statement from BOEM regarding the
absence of evidence (‘‘no documented
evidence of noise from air guns . . .
adversely affecting animal populations)
as evidence itself of no adverse effects.
According to Chevron, our ‘‘failure to
account for’’ this is ‘‘arbitrary and
capricious.’’ These issues have been
addressed both above and in the notice
of proposed rulemaking.
Comment: NRDC referenced studies
showing that noise from airgun surveys
can travel great distances underwater,
suggesting that due to the scale of this
propagation, marine mammals in the
GOM are consistently compromised in
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their ability to perform important life
functions.
Response: NMFS acknowledges that
relatively loud, low-frequency noise (as
is produced by airgun arrays) has the
potential to propagate across large
distances. However, propagation and
received sound levels are highly
variable based on many biological and
environmental factors. For example,
while one commonly cited study
(Nieukirk et al., 2012) described
detection of airgun sounds almost 4,000
km from the acoustic source, the sensors
were located within the deep sound
channel (SOFAR), where low-frequency
signals may travel great distances due to
the advantageous propagation
environment. While sounds within this
channel are unlikely to be heard by
most marine mammals due to the depth
of the SOFAR channel—which is
dependent primarily on temperature
and water pressure and therefore
variable with latitude—it is arguable
whether sounds that travel such
distances may be heard by whales as a
result of refraction to shallower depths
(Nieukirk et al., 2012; McDonald et al.,
1995). Regardless, while the extreme
propagation distances cited in some
comments may not be realistic, we
acknowledge that contraction of
effective communication space for
Bryde’s whales, which vocalize and
hear at frequencies overlapping those
emitted by airgun arrays, can occur at
distances on the order of tens to
hundreds of kilometers (e.g., Hatch et
al., 2012). However, attenuation to
levels below which more acute effects
are likely to occur is expected over
much shorter distances (Zeddies et al.,
2015, 2017a) and, therefore, we do not
agree with the contention that the GOM
would be ensonified to a degree that
marine mammals would find it an
unsuitable habitat or would be
consistently compromised in their
ability to perform important life
functions. Rather, it is likely that
displacement would occur within a
much smaller region in the vicinity of
the acoustic source (e.g., within 10–20
km of the source, depending on season
and location). Overall, the specific
geographic region and marine mammal
use of the area is sufficiently large that,
although some displacement may occur
(i.e., Level B harassment as a result of
acoustic exposure beyond the exclusion
zone), the GOM offers enough habitat
for marine mammals to seek temporary
viable habitat elsewhere, if necessary.
Many of the affected species occupy a
wide portion of the GOM, and it is
expected that individuals of these
species can reasonably find temporary
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foraging grounds or other suitable
habitat areas consistent with their
natural use of the region. Further,
although the surveys are expected to
occur over large portions of the GOM,
they will only be transitory in any given
area. Therefore, NMFS does not expect
displacement to occur frequently or for
long durations. Please see Negligible
Impact Analysis and Determinations for
additional analysis.
Comment: NRDC states that airgun
surveys have been linked to significant
reductions in the probability of calf
survival in western Pacific gray whales
(an endangered baleen whale
population), implying that these
findings indicate that such surveys
would similarly have significant
negative effects on whales in the GOM.
Response: Commenters cite a
preliminary report (Cooke et al., 2015)
that documented a reduction in calf
survival that the authors suggested may
be related to disruption of foraging from
airgun survey activity and pile driving
in Russia due to presumed avoidance of
foraging areas. However, a more recent
analysis (Cooke et al., 2017) invalidated
these findings, showing that this was a
sampling effect, as those calves that
were assumed dead in the 2015 study
have since been observed alive
elsewhere. The new study found no
significant annual variation in calf
survival. Johnson et al. (2007) had
previously reported that foraging gray
whales exposed to airgun sounds during
surveys in Russia did not experience
any biologically significant or
population-level effects.
Comment: NRDC asserts that we have
not adequately accounted for vessel
collision risk, stating that the surveys
will drive marine mammals into
shipping lanes, thereby increasing their
risk of ship strike. Relatedly, NRDC
noted that NMFS’ conclusion that ship
strikes will not occur indicates an
assumption that required ship-strike
avoidance procedures will be effective.
NRDC disagrees that the ship-strike
avoidance measures will be effective.
Response: NMFS is not aware of any
scientific information suggesting that
the surveys would drive marine
mammals into shipping lanes and
disagrees that this would be a
reasonably anticipated effect of the
specified activities. While the primary
stressor to marine mammals from the
specified activities is acoustic exposure
to the sound source, NMFS takes
seriously the risk of vessel strike and
has prescribed measures sufficient to
avoid the potential for ship strike to the
extent practicable (see Mitigation).
NMFS has required these measures
despite a very low likelihood of vessel
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strike; vessels associated with the
surveys will add a discountable amount
of vessel traffic to the specific
geographic region and, furthermore,
vessels towing survey gear travel at very
slow speeds (i.e., roughly 4–5 kn).
Comment: The MMC criticizes one
aspect of the methodology for the
analysis of chronic effects to Bryde’s
and sperm whales conducted by NMFS
with the support of JASCO Applied
Sciences (JASCO), i.e., removing the top
ten percent of the greatest pulse
exposures. (JASCO is a consulting
company contracted by NMFS and
BOEM to model acoustic exposures of
marine mammals to noise produced by
industry survey activity.) The MMC
recommends re-estimation of the
various lost listening and
communication space parameters
without removing the greatest ten
percent of pulse exposures.
Response: The goal of this modeling
exercise was to create a tool that could
help evaluate loss of ability to detect
signals of biological importance over
spatial scales relevant to the sources and
hearing capabilities of a wide variety of
regional animals. In order to do so, we
attempt to examine the portion of lowfrequency acoustic energy lost from
seismic surveys that has been
empirically measured in many contexts
around the world to generate higher
chronic, longer-term average noise
levels. Masking experienced by
individual calling and receiving animals
due to noise at relatively close
proximity to a single intermittent source
is an important but limited aspect of the
real-world contexts within which
populations of marine mammals are
exposed to noise from multiple seismic
surveys in a region like the GOM. This
modeling sought to account for the
known attributes of airgun noise, by
which low-frequency energy lost
laterally attenuates over large spatial
scales with loss of impulsive features,
leading to elevated background noise
conditions, particularly when multiple
surveys are concurrent within an
acoustic region. Close range pulse
energy would entirely drown out such
evaluation, and would not account for
the different acoustic characteristics of
the signal and potential masking at such
scales. Thus, while masking of specific
signals relative to the near-field of
operating airgun arrays is an impact that
may occur, for the purposes of the
analysis conducted for this rule, nearfield impacts have been addressed
through the modeling of acoustic
exposures. The chronic and cumulative
impacts analysis that is the subject of
this comment addresses far-field
chronic impacts. Additionally, there are
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technical concerns with modifying the
analysis specifically as recommended
and, accordingly, we disagree with the
recommendation for purposes of this
analysis of potential chronic effects.
The purpose of this modeling exercise
was not to evaluate exposure
implications for animals close to the
modeling locations (i.e., ‘‘acute’’
effects). Evaluation of acute effects, such
as injury and behavioral disruption, was
achieved through the primary acoustic
exposure modeling effort (Zeddies et al.,
2015, 2017a). These evaluated effects
(evaluated through the primary acoustic
modeling effort) are separate and
separable from loss of hearing
opportunities experienced by animals
farther from source locations, which are
evaluated through the chronic and
cumulative effects modeling discussed
here.
Marine Mammal Impacts—Habitat
Comment: NRDC expressed concern
regarding potential impacts to marine
mammal prey and/or food webs from
the planned surveys. NRDC provided
numerous citations in claiming that the
surveys could impact marine mammal
prey through the following: (1) Cause
severe physical injury and mortality; (2)
damage hearing and sensory abilities of
fish and marine invertebrates; (3)
impede development of early life
history stages; (4) induce stress that
physically damages marine
invertebrates and compromises fish
health; (5) cause startle and alarm
responses that interrupt vital behaviors;
(6) alter predator avoidance behavior
that may reduce probability of survival;
(7) affect catchability of prey species; (8)
mask important biological sounds
essential to survival; (9) reduce
reproductive success, potentially
jeopardizing long-term sustainability of
fish populations; (10) interrupt feeding
behaviors and induce other speciesspecific effects that may increase risk of
starvation, reduce reproduction, and
alter community structure; and (11)
compromise orientation of fish larvae
with potential ecosystem-level effects.
Additionally, NRDC cited a publication
by McCauley et al. (2017) as evidence
that the surveys could potentially
impact zooplankton and consequently
marine mammal food webs.
Response: NMFS strongly disagrees
with the suggestion that we ignored
effects to prey species. In fact, we
considered relevant literature (including
that cited by NRDC) in finding that the
most likely impact of survey activity to
prey species such as fish and
invertebrates would be temporary
avoidance of an area, with a rapid return
to pre-survey distribution and behavior,
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and minimal impacts to recruitment or
survival anticipated. While there is a
lack of specific scientific information to
allow an assessment of the duration,
intensity, or distribution of effects to
prey in specific locations at specific
times and in response to specific
surveys, NMFS’ review of the available
information does not indicate that such
effects could be significant enough to
impact marine mammal prey to the
extent that marine mammal fitness
would be affected. We agree that seismic
surveys could affect certain marine
mammal prey species, and addressed
these potential effects, as well as the
potential for those effects to impact
marine mammal populations, in our
notice of proposed rulemaking (83 FR
29241–29242). As stated in that notice,
our review of the available information
and the specific nature of the activities
considered herein suggest that the
activities evaluated in this ITR are not
likely to have more than short-term
adverse effects on any prey habitat or
populations of prey species. Further,
any impacts to prey species are not
expected to result in significant or longterm consequences for individual
marine mammals, or to contribute to
adverse impacts on their populations. In
support of this conclusion, we refer the
commenter to discussion provided in
our notice of proposed rulemaking.
Additional information is summarized
below.
In summary, fish react to sounds
which are especially strong and/or
intermittent low-frequency sounds, and
behavioral responses such as flight or
avoidance are the most likely effects.
However, the reaction of fish to airguns
depends on the physiological state of
the fish, past exposures, motivation
(e.g., feeding, spawning, migration), and
other environmental factors. While we
agree that some studies have
demonstrated that airgun sounds might
affect the distribution and behavior of
some fishes, potentially impacting
foraging opportunities or increasing
energetic costs (e.g., Fewtrell and
McCauley, 2012; Pearson et al., 1992;
Skalski et al., 1992; Santulli et al., 1999;
Paxton et al., 2017), our review shows
that the weight of evidence indicates
either no or only a slight reaction to
noise (e.g., Miller and Cripps, 2013;
Dalen and Knutsen, 1987; Pena et al.,
2013; Chapman and Hawkins, 1969;
Wardle et al., 2001; Sara et al., 2007;
Jorgenson and Gyselman, 2009; Blaxter
et al., 1981; Cott et al., 2012; Boeger et
al., 2006), and that, most commonly,
while there may be impacts to fish as a
result of noise from nearby airguns, any
effects will be temporary. For example,
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investigators reported significant, shortterm declines in commercial fishing
catch rate of gadid fishes during and for
up to five days after seismic survey
operations, but the catch rate
subsequently returned to normal (Engas
et al., 1996; Engas and Lokkeborg,
2002). Other studies have reported
similar findings (e.g., Hassel et al.,
2004). Skalski et al. (1992) also found a
reduction in catch rates—for rockfish
(Sebastes spp.) in response to controlled
airgun exposure—but suggested that the
mechanism underlying the decline was
not dispersal but rather decreased
responsiveness to baited hooks
associated with an alarm behavioral
response. A companion study showed
that alarm and startle responses were
not sustained following the removal of
the sound source (Pearson et al., 1992).
Therefore, Skalski et al. (1992)
suggested that the effects on fish
abundance may be transitory, primarily
occurring during the sound exposure
itself. In some cases, effects on catch
rates are variable within a study, which
may be more broadly representative of
temporary displacement of fish in
response to airgun noise (i.e., catch rates
may increase in some locations and
decrease in others) than any long-term
damage to the fish themselves (Streever
et al., 2016).
SPLs of sufficient strength have been
known to cause injury to fish and fish
mortality and, in some studies, fish
auditory systems have been damaged by
airgun noise (McCauley et al., 2003;
Popper et al., 2005; Song et al., 2008).
However, in most fish species, hair cells
in the ear continuously regenerate and
loss of auditory function likely is
restored when damaged cells are
replaced with new cells. Halvorsen et al.
(2012b) showed that a temporary
threshold shift (TTS) of 4–6 dB was
recoverable within 24 hours for one
species. Impacts would be most severe
when the individual fish is close to the
source and when the duration of
exposure is long—both of which are
conditions unlikely to occur for surveys
that are necessarily transient in any
given location and likely result in brief,
infrequent noise exposure to prey
species in any given area. For these
surveys, the sound source is constantly
moving, and most fish would likely
avoid the sound source prior to
receiving sound of sufficient intensity to
cause physiological or anatomical
damage. In addition, ramp-up may
allow certain fish species the
opportunity to move further away from
the sound source.
NMFS considered the research
provided by NRDC and disagrees with
its interpretation of the literature. A
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recent comprehensive review (Carroll et
al., 2017) found that results are mixed
as to the effects of airgun noise on the
prey of marine mammals. While some
studies suggest a change in prey
distribution and/or a reduction in prey
abundance following the use of seismic
airguns, others suggest no effects or
even positive effects in prey abundance.
As one specific example—regarding
Paxton et al. (2017), which describes
findings related to the effects of a 2014
seismic survey on a reef off of North
Carolina—NRDC asserts that the study
supports a conclusion that seismic
surveys ‘‘cause significant shifts in
distribution that may compromise life
history behaviors.’’ However, our own
review of this work shows that a
reasonable interpretation leads to a
more moderate conclusion. While the
study did show a 78 percent decrease in
observed nighttime abundance for
certain species—which NRDC interprets
as a significant shift in distribution that
could compromise life history
behaviors—it is important to note that
the evening hours during which the
decline in fish habitat use was recorded
(via video recording) occurred on the
same day that the seismic survey
passed, and no subsequent data is
presented to support an inference that
the response was long-lasting.
Additionally, given that the finding is
based on video images, the lack of
recorded fish presence does not support
a conclusion that the fish actually
moved away from the site or suffered
any serious impairment because fish
may remain present yet not be recorded
on video. In summary, this particular
study corroborates prior studies
demonstrating a startle response or
short-term displacement.
Available data suggest that
cephalopods are capable of sensing the
particle motion of sounds and detect
low frequencies up to 1–1.5 kHz,
depending on the species, and so are
likely to detect airgun noise (Kaifu et al.,
2008; Hu et al., 2009; Mooney et al.,
2010; Samson et al., 2014). Auditory
injuries (lesions occurring on the
statocyst sensory hair cells) have been
reported upon controlled exposure to
low-frequency sounds, suggesting that
cephalopods are particularly sensitive to
low-frequency sound (Andre et al.,
2011; Sole et al., 2013). Behavioral
responses, such as inking and jetting,
have also been reported upon exposure
to low-frequency sound (McCauley et
al., 2000b; Samson et al., 2014). Similar
to fish, however, the transient nature of
the surveys leads to an expectation that
effects will be largely limited to
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behavioral reactions and would occur as
a result of brief, infrequent exposures.
We discussed impacts to benthic
communities from impulsive sound
generated by active acoustic sound
sources in our notice of proposed
rulemaking, including one study
showing that exposure to airgun signals
was found to significantly increase
mortality in scallops, in addition to
causing significant changes in
behavioral patterns and disruption of
hemolymph chemistry during exposure
(although the authors state that the
observed levels of mortality were not
beyond naturally occurring rates) (Day
et al., 2017). In addition, Fitzgibbon et
al. (2017) found significant changes to
hemolymph cell counts in spiny
lobsters subjected to repeated airgun
signals, with the effects lasting up to a
year post-exposure. However, despite
the high levels of exposure, direct
mortality was not observed. Further, in
reference to the study, Day et al. (2016)
stated that ‘‘[s]eismic surveys appear to
be unlikely to result in immediate large
scale mortality [. . .] and, on their own,
do not appear to result in any degree of
mortality’’ and that ‘‘[e]arly stage lobster
embryos showed no effect from air gun
exposure, indicating that at this point in
life history, they are resilient to
exposure and subsequent recruitment
should be unaffected.’’ A majority of the
studies reviewed by NMFS have
observed no increased mortality in
invertebrates exposed to airgun noise
(e.g., Wardle et al., 2001; Parry et al.,
2002; Christian et al., 2003;
Andriguetto-Filho et al., 2005; Parry and
Gason, 2006; Payne et al., 2007;
Harrington et al., 2010; Przeslawski et
al., 2018).
With regard to potential impacts on
zooplankton, McCauley et al. (2017)
found that exposure to airgun noise
resulted in significant depletion for
more than half the taxa present and that
there were two to three times more dead
zooplankton after airgun exposure
compared with controls for all taxa,
within 1 km of the airguns. However,
the authors also stated that in order to
have significant impacts on r-selected
species (i.e., those with high growth
rates and that produce many offspring)
such as plankton, the spatial or
temporal scale of impact must be large
in comparison with the ecosystem
concerned, and it is possible that the
findings reflect avoidance by
zooplankton rather than mortality
(McCauley et al., 2017). In addition, the
results of this study are inconsistent
with a large body of research that
generally finds limited spatial and
temporal impacts to zooplankton as a
result of exposure to airgun noise (e.g.,
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Dalen and Knutsen, 1987; Payne, 2004;
Stanley et al., 2011). Most prior research
on this topic, which has focused on
relatively small spatial scales, has
showed minimal effects (e.g.,
Kostyuchenko, 1973; Booman et al.,
1996; S#tre and Ona, 1996; Pearson et
al., 1994; Bolle et al., 2012).
A modeling exercise was conducted
as a follow-up to the McCauley et al.
(2017) study (as recommended by
McCauley et al.), in order to assess the
potential for impacts on ocean
ecosystem dynamics and zooplankton
population dynamics (Richardson et al.,
2017). Richardson et al. (2017) found
that a full-scale airgun survey would
impact copepod abundance within the
survey area, but that effects at a regional
scale were minimal (2 percent decline
in abundance within 150 km of the
survey area and effects not discernible
over the full region). The authors also
found that recovery within the survey
area would be relatively quick (3 days
following survey completion), and
suggest that the quick recovery was due
to the fast growth rates of zooplankton,
and the dispersal and mixing of
zooplankton from both inside and
outside of the impacted region. The
authors also suggest that surveys in
areas with more dynamic ocean
circulation in comparison with the
study region and/or with deeper waters
(i.e., typical GOM survey locations)
would have less net impact on
zooplankton.
Notably, a recently described study
produced results inconsistent with
those of McCauley et al. (2017).
Researchers conducted a field and
laboratory study to assess if exposure to
airgun noise affects mortality, predator
escape response, or gene expression of
the copepod Calanus finmarchicus
(Fields et al., 2019). Immediate
mortality of copepods was significantly
higher, relative to controls, at distances
of 5 m or less from the airguns.
Mortality one week after the airgun blast
was significantly higher in the copepods
placed 10 m from the airgun but was not
significantly different from the controls
at a distance of 20 m from the airgun.
The increase in mortality, relative to
controls, did not exceed 30 percent at
any distance from the airgun. Moreover,
the authors caution that even this higher
mortality in the immediate vicinity of
the airguns may be more pronounced
than what would be observed in freeswimming animals due to increased
flow speed of fluid inside bags
containing the experimental animals.
There were no sublethal effects on the
escape performance or the sensory
threshold needed to initiate an escape
response at any of the distances from
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the airgun that were tested. Whereas
McCauley et al. (2017) reported an SEL
of 156 dB at a range of 509–658 m, with
zooplankton mortality observed at that
range, Fields et al. (2019) reported an
SEL of 186 dB at a range of 25 m, with
no reported mortality at that distance.
Regardless, if we assume a worst-case
likelihood of severe impacts to
zooplankton within approximately 1 km
of the acoustic source, the typically
wide dispersal of survey vessels and
brief time to regeneration of the
potentially affected zooplankton
populations does not lead us to expect
any meaningful follow-on effects to the
prey base for odontocete predators (the
region considered in this rule is not an
important feeding area for taxa that feed
directly on zooplankton, i.e.,
mysticetes).
Given the inconsistency of the
McCauley et al. (2017) results with prior
research on impacts to zooplankton as a
result of exposure to airgun noise and
with the research of Fields et al. (2019),
further validation of those findings
would be necessary for NMFS to reach
a determination that these impacts are
likely to occur. Moreover, a single study
is not sufficient to evaluate the potential
impacts, and further study in additional
locations must be conducted. Therefore,
BOEM proposed to fund such a study as
part of their 2019–21 Studies
Development Plan (www.boem.gov/FY2019-2021-SDP/).
A recent review article concluded
that, while laboratory results provide
scientific evidence for high-intensity
and low-frequency sound-induced
physical trauma and other negative
effects on some fish and invertebrates,
the sound exposure scenarios in some
cases are not realistic to those
encountered by marine organisms
during routine seismic operations
(Carroll et al., 2017). The review finds
that there has been no evidence of
reduced catch or abundance following
seismic activities for invertebrates, and
that there is conflicting evidence for fish
with catch observed to increase,
decrease, or remain the same. Further,
where there is evidence for decreased
catch rates in response to airgun noise,
these findings provide no information
about the underlying biological cause of
catch rate reduction (Carroll et al.,
2017).
NRDC’s assertions regarding the likely
effects of airgun survey noise on marine
mammal prey include, for example, the
assertion that the specified activity
would harm fish and invertebrate
species over the long-term, cause
reductions in recruitment and effects to
behavior that may reduce reproductive
potential and foraging success and
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increase the risk of predation, and
induce changes in community
composition via such population-level
impacts. We have addressed these
claims both in this response and in our
review of the available literature. We
also reviewed available information
regarding populations of representative
prey stocks in the northern GOM, i.e.,
the only U.S. location where marine
seismic surveys are a routinely
occurring activity. While we recognize
the need for caution in assuming
correlation between the ongoing survey
activity in the GOM and the health of
assessed stocks there, we also believe
this information has some value in
informing the likelihood of populationlevel effects to prey species and,
therefore, the likelihood that the
specified activity would negatively
impact marine mammal populations via
effects to prey. We note that the
information reported below is in context
of managed commercial and recreational
fishery exploitation, in addition to any
other impacts (e.g., noise) on the stocks.
The species listed below are known
prey species for marine mammals and
represent groups with different life
histories and patterns of habitat use.
Numerous other managed stocks are
similarly healthy.
• Red snapper (Lutjanus
campechanus): Red snapper are bottomdwelling fish generally found at
approximately 10–190 m deep that
typically live near hard structures on
the continental shelf that have moderate
to high relief (for example, coral reefs,
artificial reefs, rocks, ledges, and caves),
sloping soft-bottom areas, and limestone
deposits. Larval snapper swim freely
within the water column. Increases in
total and spawning stock biomass are
predicted beginning in about 1990
(Cass-Calay et al., 2015). Regional
estimates suggest that recruitment in the
west has generally increased since the
1980s, and has recently been above
average, while recruitment in the east
peaked in the mid-2000s, and has since
declined. However, the most recent
assessment suggests a less significant
decline (to moderate levels) (Cass-Calay
et al., 2015).
• Yellowfin tuna (Thunnus
albacares): Yellowfin tuna are highly
migratory, living in deep pelagic waters,
and spawn in the GOM from May to
August. However, we note that a single
stock is currently assumed for the entire
Atlantic, with additional spawning
grounds in the Gulf of Guinea,
Caribbean Sea, and off Cabo Verde. The
most recent assessment indicates that
spawning stock biomass for yellowfin
tuna is stable or increasing somewhat
and that, overall, the stock is near levels
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that produce the maximum sustainable
yield (ICCAT, 2016).
• King mackerel (Scomberomorus
cavalla): King mackerel are a coastal
pelagic species, found in open waters
near the coast in waters from
approximately 35–180 m deep. King
mackerel migrate in response to changes
in water temperature, and spawn in
shelf waters from May through October.
Estimates of recruitment demonstrate
normal cyclical patterns over the past 50
years, with a period of higher
recruitment most recently (1990–2007)
(SEDAR, 2014). Long-term spawning
stock biomass patterns indicate that the
spawning stock has been either
rebuilding or remained relatively
consistent over the last 20 years, with
nothing indicating that the stock has
declined in these recent decades
(SEDAR, 2014).
In summary, the scientific literature
demonstrates that impacts of seismic
surveys on marine mammal prey species
will likely be limited to behavioral
responses, the majority of prey species
will be capable of moving out of the area
during surveys, a rapid return to normal
recruitment, distribution, and behavior
for prey species is anticipated, and,
overall, impacts to prey species, if any,
will be minor and temporary. Prey
species exposed to sound might move
away from the sound source, experience
TTS, experience masking of biologically
relevant sounds, or show no obvious
direct effects. Mortality from
decompression injuries is possible in
close proximity to a sound, but only
limited data on mortality in response to
airgun noise exposure are available
(Hawkins et al., 2014). The most likely
impacts for most prey species in a given
survey area would be temporary
avoidance of the area. Surveys using
towed airgun arrays move through an
area relatively quickly, limiting
exposure to multiple impulsive sounds.
In all cases, sound levels would return
to ambient once a survey moves out of
the area or ends and the noise source is
shut down and, when exposure to
sound ends, behavioral and/or
physiological responses are expected to
end relatively quickly (McCauley et al.,
2000b). The duration of fish avoidance
of a given area after survey effort stops
is unknown, but a rapid return to
normal recruitment, distribution, and
behavior is anticipated. While the
potential for disruption of spawning
aggregations or schools of important
prey species can be meaningful on a
local scale, the mobile and temporary
nature of most surveys and the
likelihood of temporary avoidance
behavior suggest that impacts would be
minor.
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Finally, and relevant to NMFS’
findings under the MMPA, NRDC does
not demonstrate that even the asserted
worst-case effects on prey species would
have any meaningful impact on marine
mammals or their respective
populations. Referencing a single study
on zooplankton effects (i.e., McCauley et
al., 2017), NRDC implies that airgun
surveys will definitively reduce ‘‘the
abundance and diversity of zooplankton
over vast areas and induc[e] changes in
community composition due to the
aggregation of individual- and
population-level impacts across
multiple fish and invertebrate species,’’
thereby leading to ecosystem-level
effects that would harm marine mammal
populations. NMFS disagrees with this
interpretation of the scientific literature
and notes the presence of healthy stocks
of marine mammal prey species
currently found in the GOM, despite
decades of routine geophysical survey
operations, but also a devastating oil
spill (discussed in detail in the notice of
proposed rulemaking). NMFS believes
that no evidence is presented to
contradict our conclusions regarding
likely impacts to marine mammals due
to effects on prey species, i.e., that
impacts of the specified activity are not
likely to have more than short-term
adverse effects on any prey habitat or
populations of prey species, and that
any effects that do occur are not
expected to result in significant or longterm consequences for individual
marine mammals, or to contribute to
adverse impacts on their populations.
Comment: The Associations object to
NMFS’ use of an analysis of chronic and
cumulative impacts of noise on marine
mammals in the GOM (i.e., the CCE
report), which was described in detail in
our notice of proposed rulemaking. The
Associations state that ‘‘[c]oncepts such
as ‘‘soundscape,’’ ‘‘communication
space,’’ or ‘‘acoustic footprint’’ have no
basis in any existing statutory or
regulatory authorities, and are therefore
inapplicable to this rulemaking.’’
Response: The purpose of the analysis
was to evaluate the more cumulative
nature of low-frequency, long-distance
propagation of relatively low-intensity
energy from multiple seismic surveys
operating concurrently in a region, and
to evaluate potential loss of ability to
detect signals of biological importance
over spatial scales relevant to the
sources and hearing capabilities of
representative species. NMFS is
required to evaluate the effects of the
specified activity on the potentially
impacted marine mammal stocks and
their habitat. Noise can disrupt marine
mammals’ behavioral patterns through
the contraction of their communication
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space, among other impacts. Moreover,
NMFS is required to mitigate impacts on
marine mammal species or stocks and
their habitat. Concepts such as listening
area and communication space are not
novel, having been published in peerreviewed literature and previously
applied in impact assessment contexts.
NMFS is required to consider these
effects.
Comment: NRDC argues that NMFS
fails to consider chronic harm,
including masking effects and impacts
on acoustic habitat. For example, NRDC
asserts that the consideration of masking
in NMFS’ negligible impact analysis
was cursory in that it only came through
the vulnerability ratings and ‘‘seems to
misapprehend the spatial and temporal
scope of the effects’’ of masking.
Similarly, in addition to citing general
concerns about chronic effects to
Bryde’s whales and other species, NRDC
asserts that acoustic habitat is
discussed, but not factored into the
negligible impact analysis.
Response: The potential impacts of
masking were properly considered.
NRDC significantly understates the
consideration given to masking effects
in the Expert Working Group (EWG) risk
assessment framework (see Negligible
Impact Analysis and Determinations).
Broadly, the results of the EWG analysis
for any given species are based on the
integration of two components: The
severity of the impacts (which reflects
the extent of the activities overlaid with
the presence and distribution of the
given species) and the vulnerability of
that species based on multiple
biological and environmental risk
factors, including explicit consideration
of masking. The maximum possible
vulnerability score any species can
attain under the assessment across all of
these factors is 30. The masking
component of the vulnerability score
considers communication masking,
foraging masking, and navigation/
orientation masking—for a total of seven
points. The minimum score that any
species assessed in the context of these
survey activities could (and did) attain
is 1, while the Bryde’s whale was given
the maximum scores across all types of
masking for a score of 7. The differential
across the highest and lowest possible
masking scores is 6, out of a maximum
possible total of 30 for the overall
vulnerability score, which means that
masking accounts for twenty percent of
a species’ vulnerability rating. Twenty
percent is an appropriate and not
insubstantial proportion of the
vulnerability score, given that the total
score (with its 30-point maximum) also
accounts for behavioral impacts,
whether there are biologically important
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areas or times overlaying the activities,
whether there are additional chronic
anthropogenic (e.g., other anthropogenic
noise) or chronic biological factors (e.g.,
disease), and the status and trends of the
population.
NMFS recognizes that masking is not
necessarily co-extensive with
harassment and explicitly recognizes
this in our discussion of effects,
although we also note that the distances
at which behavioral harassment is
quantified for this rule are farther than
those contemplated in the past, due to
the behavioral harassment thresholds
used (see the Estimated Take section
and comment responses later in this
section for further discussion of acoustic
thresholds). As discussed elsewhere,
NMFS designed and supported the
implementation of a chronic and
cumulative effects analysis (the CCE
report, discussed later in this preamble)
for the specific purpose of addressing
the effects of these activities on the
listening space of all species and the
communication space of Bryde’s whales
specifically. This modeling effort
explicitly considered the effects of
masking over realistic spatial scales. In
their 2017 public comments on
incidental harassment authorizations
NMFS had proposed for seismic survey
activities in the Atlantic Ocean, NRDC
specifically recommended that NMFS
conduct a modeling exercise like the
effort conducted here for the GOM rule
to better support those findings (see 83
FR 63268; December 7, 2018), yet they
now suggest that this analysis is
inadequate, even paired with the
quantitative analysis included in the
EWG analysis as it is here. See Potential
Effects of the Specified Activities on
Marine Mammals and Their Habitat in
the notice of proposed rulemaking for
additional discussion.
Comment: A private citizen offers
commentary and clarifications regarding
the discussions of acoustic masking and
acoustic habitat provided in our notice
of proposed rulemaking.
Response: We appreciate the
discussion provided by the commenter,
but note that no specific
recommendations are provided towards
an improved assessment of the effects of
chronic aggregate noise from survey
activity, as the commenter suggests is
needed.
Cumulative Impacts and Related Issues
Comment: NRDC expressed concern
regarding cumulative impacts, claiming
that NMFS’ negligible impact
determination underestimates impacts
to marine mammal species and
populations because it fails to consider
the effects of other anticipated activities
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5339
on the same marine mammal
populations. NRDC also stated that
NMFS must include geophysical
surveys occurring within state waters
within the scope of the ITR.
Response: Neither the MMPA nor
NMFS’ codified implementing
regulations address consideration of
other unrelated activities and their
impacts on populations. However, the
preamble for NMFS’ implementing
regulations (54 FR 40338; September 29,
1989) states in response to comments
that the impacts from other past and
ongoing anthropogenic activities are to
be incorporated into the negligible
impact analysis via their impacts on the
baseline. Consistent with that direction,
NMFS has factored into its negligible
impact analysis the impacts of other
past and ongoing anthropogenic
activities via their impacts on the
baseline, e.g., as reflected in the density/
distribution and status of the species,
population size and growth rate, the
chronic and cumulative effects analysis
(the ‘‘CCE report’’ discussed later in this
preamble), and other relevant stressors.
Some of these are addressed explicitly
through the environmental risk factor
scoring in the population vulnerability
analysis of the Expert Working Group
Assessment (including consideration of
Deepwater Horizon (DWH) oil spill
effects and risk from other
anthropogenic activities). In addition,
we consider these factors as relevant
contextual elements of the analysis. See
the Negligible Impact Analysis and
Determinations section of this notice for
full detail.
Our 1989 final rule for the MMPA
implementing regulations also
addressed public comments regarding
cumulative effects from future,
unrelated activities. There we stated
that such effects are not considered in
making findings under section 101(a)(5)
concerning negligible impact. We
indicated (1) that NMFS would consider
cumulative effects that are reasonably
foreseeable when preparing a NEPA
analysis, and (2) that reasonably
foreseeable cumulative effects would
also be considered under section 7 of
the ESA for ESA-listed species.
Here, we recognize the potential for
cumulative impacts, as analyzed
through BOEM’s PEIS, which addressed
the impacts of an extended time period
of survey activity that may be permitted
by BOEM (ten years versus the five
years that the ITR is limited to), and
which NMFS adopted as the basis for its
Record of Decision. In that analysis, the
assessment was focused on whether the
predicted level of take from the
forecasted level of survey effort, when
considered in context, would have a
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meaningful biological consequence at a
species or population level. NMFS,
therefore, assessed and integrated other
contextual factors (e.g., species’ life
history and biology, distribution,
abundance, and status of the stock;
mitigation and monitoring;
characteristics of the surveys and sound
sources) in determining the overall
impact of issuance of the ITR and
subsequent LOAs on the human
environment. Key considerations
included the nature of the surveys and
the required mitigation. In all cases, it
is expected that sound levels will return
to previous background levels once the
acoustic source moves a certain distance
from the area, or the surveys cease. The
proposed rule also identified several
time-area restrictions to minimize risk
or severity of impacts to the extent
practicable, consistent with the MMPA’s
least practicable adverse impact
standard. In the final rule, two of those
areas were removed from consideration
based on the reduction in the scope of
the rule per BOEM’s request. The other
proposed mitigation area remains (as
modified; see Mitigation). Although
those two areas have been removed from
consideration as mitigation due to the
reduction in scope of the rule, the
practical effect on GOM stocks is
similar, in that no survey activity within
those areas may be considered for take
authorization pursuant to the rule. The
similar result is a reduction in the
overall numbers of take but also,
importantly, elimination or
minimization of impacts to marine
mammal species or stocks in the areas
most important to them for feeding,
breeding, and other important functions.
Therefore, the severity of takes that may
occur pursuant to the rule is expected
to be meaningfully lower due to the
reduction in impacts that could reduce
reproductive success or survivorship.
In summary, NMFS does not expect
aggregate impacts from the forecast level
of survey effort to affect rates of
recruitment or survival for marine
mammals, either alone or in
combination with other past, present, or
ongoing activities. The cumulative
impacts of these surveys (i.e., the
incremental impact of the action when
added to other past, present, and
reasonably foreseeable future actions)
were addressed as required through the
NEPA documents cited above. These
documents, as well as the relevant Stock
Assessment Reports, are part of NMFS’
Administrative Record for this action,
and provided the decision-maker with
information regarding other activities in
the action area that affect marine
mammals, an analysis of cumulative
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impacts, and other information relevant
to the determinations made under the
MMPA.
Separately, cumulative effects were
analyzed as required through NMFS’
required intra-agency consultation
under section 7 of the ESA, which
concluded that NMFS’ action of issuing
the ITR and subsequent LOAs was not
likely to jeopardize the continued
existence of listed marine mammals.
We disagree with NRDC’s suggestion
that we include geophysical surveys in
state waters within the scope of this
rulemaking. Section 101(a)(5)(A) of the
MMPA requires NMFS to make a
determination that the take incidental to
a ‘‘specified activity’’ will have a
negligible impact on the affected species
or stocks of marine mammals, and will
not result in an unmitigable adverse
impact on the availability of marine
mammals for taking for subsistence
uses. NMFS’ implementing regulations
require applicants to include in their
request a detailed description of the
specified activity or class of activities
that can be expected to result in
incidental taking of marine mammals.
50 CFR 216.104(a)(1). Thus, the
‘‘specified activity’’ for which incidental
take coverage is being sought under
section 101(a)(5)(A) is generally defined
and described by the applicant. Here,
BOEM is the applicant for the ITR in
support of industry operators, and we
are responding to the specified activity
as described in that petition (and
making the necessary findings on that
basis). As BOEM’s PEIS makes clear,
BOEM does not have a regulatory role
regarding surveys occurring in state
waters. (See, e.g., BOEM’s PEIS, Chapter
1.1.3)
NRDC’s representation of our action—
‘‘The agency’s decision to evaluate the
impacts of state water surveys
separately as if they would occur in
isolation’’—also ignores the fact that we
have no information about the possible
extent of potential future geophysical
survey activity in state waters, including
type, amount, duration, timing, location,
etc., even if such activity were to occur.
Although it may be reasonable to
assume that such activity occurs, we
have no specific knowledge of any past,
present, or reasonably foreseeable future
survey activity in state waters. No
prospective applicant has contacted
NMFS to request incidental take
authorization for any such survey
activity planned or expected within
state waters, on either a programmatic
or specific basis. NRDC did not provide
any information about the expected
future extent of survey activity in state
waters.
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Acoustic Thresholds
Comment: NRDC expressed concerns
regarding NMFS’ proposed use of the
probabilistic response function
described by Wood et al. (2012), in
which 10 percent, 50 percent, and 90
percent of individuals exposed are
assumed to produce a behavioral
response (of a sufficient degree of
severity to constitute Level B
harassment) at exposures of 140, 160,
and 180 dB root mean square (rms),
respectively. (The function is shifted for
the more behaviorally sensitive beaked
whales such that 50 percent and 90
percent response probabilities are
assumed to occur at 120 and 140 dB
rms, respectively.) NRDC stated that the
function is inconsistent with the best
available science, asserting that
behavioral disruptions occur at higher
percentages at lower noise exposure
levels than those suggested by Wood et
al. (2012). NRDC’s criticism of the
function also focused on the use of
horizontal displacement studies as the
supposed basis of analysis for Wood et
al. (2012), as well as on the function’s
nature as a series of step functions. In
addition, NRDC expressed concerns that
the use of frequency weighting in the
Wood et al. (2012) approach is
inappropriate. NRDC requested that
NMFS revise the threshold as suggested
in Nowacek et al. (2015), which
recommended a similar function (but
centered on 140 dB rms rather than 160
dB rms), while simultaneously stating
that the use of such step-based risk
functions is ‘‘biologically irrational.’’
Overall, NRDC claims that reliance on
this function results in underestimation
of impacts. A private citizen echoed
some of NRDC’s comments on this topic
while CRE supports use of the Wood et
al. approach.
Response: NMFS has been criticized
in the past for the use of the single-step
160-dB rms approach. Those criticisms
are based on the idea that an approach
reflecting a more complex multi-step
probabilistic function would more
effectively represent the known
variation in responses at different levels
due to differences in the receivers, the
context of the exposure, and other
factors, as well as the science indicating
that animals may react in ways
constituting Level B harassment when
exposed to lower received levels. In
developing the acoustic exposure
analysis for the proposed rulemaking,
we reviewed relevant past public
comments as well as the best available
science, determining that a more
complex probabilistic function is indeed
better reflective of available scientific
information, and that it was appropriate
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to take the fundamental step of
recognizing the potential for Level B
harassment occurring at exposures to
received levels below 160 dB rms (as
well as the potential for no Level B
harassment occurring at exposures
above 160 dB rms). This approach
necessarily also accounts for differential
hearing sensitivity by incorporating
frequency-weighting functions, as
behavioral responses in cetaceans are
best explained by the interaction
between sound source type and
functional hearing group (Gomez et al.,
2016). NMFS has determined that the
general approach used for this rule—a
probabilistic risk function that allows
for the likelihood of differential
response probability at given received
levels on the basis of multiple factors,
including behavioral context and
distance from the source, and that
addresses particularly sensitive
species—is appropriate in light of the
best available scientific information.
However, because behavioral
responses to sound depend on the
context in which an animal receives the
sound, including the animal’s
behavioral mode when it hears sounds,
prior experience, additional biological
factors, and other contextual factors,
defining sound levels that disrupt
behavioral patterns is extremely
difficult. Even experts have not
previously been able to suggest specific
new criteria due to these difficulties
(e.g., Southall et al. 2007; Gomez et al.,
2016). Agency expertise is appropriate
in defining the particular steps at which
specific response probabilities are
assumed to occur, and while we
acknowledge our approach reduces a
complex suite of interactions to make
reasonable inferences, it is consistent
with the best available science.
NRDC expressed concerns regarding
our approach by noting the size
discrepancy between the area ensonified
to 140 dB versus that ensonified to 160
dB, implying that we ignore potential
responses at the lower received level. To
clarify, the difference between our
approach and NRDC’s recommendation
is solely in the proportion of a
population assumed to be taken upon
exposure to the specified received level
which, as stated above, is determined on
the basis of expert judgement based on
the best available science. We believe
that the Wood et al. (2012) function is
consistent with the best available
science, and is therefore an appropriate
approach. Below, we address NRDC’s
concerns in greater detail.
NRDC referenced ‘‘recent’’ research
they claim is not consistent with the
recommendations of Wood et al. (2012).
We note that, of the nine studies cited
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by NRDC, five were published prior to
the Wood et al. (2012) study, and were
therefore available for those authors’
consideration (and some were
specifically referenced by those authors
in discussion of their
recommendations). Further, we disagree
that the referenced findings are
inconsistent with Wood et al. (2012).
First, a mere reaction to noise exposure
does not mean that a take by Level B
harassment, as defined by the MMPA,
has occurred. For a take to occur
requires that an act have ‘‘the potential
to disturb by causing disruption of
behavioral patterns,’’ not simply result
in a detectable change in motion or
vocalization. NRDC also suggests that
some of these studies were not
incorporated into Wood et al.’s
recommendations, or our consideration
of those and other potential approaches
in context of the available science, and
criticize what they view as an overreliance on horizontal displacement
studies as the supposed basis of
analysis. While it is true that the
majority of available behavioral data
focus on avoidance responses, Wood et
al. (2012) does not mention excluding
behavioral studies involving vocal
changes, and the precedent Southall et
al. (2007) specifically incorporates
numerous studies that do mention
changes in vocalization associated with
sound exposure. Thus, these datasets
were not excluded and, as discussed in
our notice of proposed rulemaking, we
adequately considered all studies
addressed by NRDC.
Regarding baleen whales, we
acknowledge that changes in
vocalization have been observed in
association with exposure to airgun
surveys within migratory and nonmigratory contexts (e.g., Castellote et al.,
2012; Blackwell et al., 2013; Cerchio et
al., 2014). The potential for such effects
to occur over relatively large spatial
scales is not surprising for species with
large communication spaces (e.g., Clark
et al., 2009), but we reiterate our
disagreement with NRDC’s apparent
contention that every detected change to
vocalizations rises to the level of a take.
NRDC cites reports of changes in
vocalization, typically for baleen
whales, as evidence in support of lower
thresholds, claiming these reactions
result in biological consequences
indicating that the reaction was indeed
a take. However, NMFS is not aware of
research that provides a well-supported
link between the reported reactions at
lower received levels and the putative
consequences. In conflict with NRDC’s
interpretation of the literature are
documented instances of marine
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5341
mammal exposure to greater received
levels that did not elicit any response
(e.g., Malme et al., 1983, 1984, 1985,
1988; McCauley et al., 1998, 2000a,
2000b; Barkaszi et al., 2012; Stone,
2015a; Gailey et al., 2016; Barkaszi and
Kelly, 2018).
The received level associated with
stoppage of calling for bowhead whales
(Balaena mysticetus) observed by
Blackwell et al. (2013, 2015)—a
response that may arguably rise to the
level of harassment—is consistent with
the Wood et al. (2012) scheme, in which
the potential for take upon exposure to
received levels as low as 140 dB is
accounted for. Similarly, the findings of
Pirotta et al. (2014) for harbor porpoise
(Phocoena phocoena) are consistent
with the treatment of behaviorally
sensitive species by Wood et al., in
which the potential for take at even
lower received levels is accounted for
(though irrelevant here, as harbor
porpoise are not found in the GOM).
The response levels reported by
McDonald et al. (1995) and Di Iorio and
Clark (2009) for blue whales
(Balaenoptera musculus) also comport
with the Wood et al. function, if we
assume that the observed responses
equate to harassment (though it is not
clear that they do). With regard to
NRDC’s citation of Clark and Gagnon
(2006), a non-peer reviewed white
paper, NRDC incorrectly overestimated
the area over which the effect was
observed by an order of magnitude (the
paper discusses an area of 100 x 100
nmi, which equates to 10,000 nmi2—not
100,000 nmi2).
In regard to Cerchio et al. (2014), it is
important to note that received levels
provided in this study are those
recorded at locations of their
underwater recording devices. The
authors indicated ‘‘we did not have the
ability to locate the singers or the
seismic survey vessel, estimate the
source level of the pulses, the distance
between the source and potentially
impacted singers, or the received level
of the pulses at the singers.’’ The same
situation, i.e., actual received levels at
the location of the animals are
unknown, is true for Castellote et al.
(2012) and Clark and Gagnon (2006),
which provide average background
sound levels with and without the
presence of airgun surveys. Thus, not
having the location of the animals at the
time of exposure makes it difficult to
draw conclusions based strictly on
received level. NMFS has evaluated the
papers and determined they are not
informative about appropriate Level B
harassment thresholds.
Regarding sperm whales, NMFS
disagrees that assuming a 100 percent
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probability of take of sperm whales
upon exposure to survey noise at 135
dB—as suggested by NRDC—is an
accurate reflection of the results of the
Miller et al. (2009) study. While we
agree that the work of Miller et al.
(2009) suggests that sperm whales in the
GOM may be susceptible to disruption
of foraging behavior upon exposure to
relatively moderate sound levels, NRDC
incorrectly interprets results of the
study in claiming that sperm whale
‘‘foraging success’’ was found to
‘‘decline significantly.’’ Instead, the
authors report that buzz rates (a proxy
for attempts to capture prey) were
approximately 20 percent lower,
meaning that the appropriate
interpretation would be that foraging
activity (versus foraging success) was
reduced by 20 percent (Jochens et al.,
2008). Of the eight whales tagged in that
study, only one was observed to actually
cease foraging.
Moreover, while we do believe that
these results support a conclusion that
exposure to survey noise can impact
foraging activity, other commenters
have interpreted them differently, e.g.,
by focusing on the finding that exposed
whales did not change behavioral state
during exposure or show horizontal
avoidance (a finding replicated in other
studies, e.g., Madsen et al., 2002a;
Winsor et al., 2017). Importantly, the
observed effect was not statistically
significant and, as reported by the
authors, constituted ‘‘subtle effects on
their foraging behavior.’’ Furthermore,
the authors of the Wood et al. (2012)
study explicitly described their
consideration of Miller et al. (2009) in
the development of their recommended
criteria. Therefore, the Wood et al.
(2012) recommendation is indeed
consistent with the Miller et al. (2009)
study.
In referencing Bowles et al. (1994),
NRDC fails to state that the observed
cessation of vocalization was likely in
response to a low-frequency tone
(dissimilar to airgun signals), though a
distant airgun survey was noted as
producing signals that were detectable
above existing background noise. NRDC
recommends that NMFS base a sperm
whale threshold on the findings of a
separate study of exposure of sperm
whales and other species to sonar
signals (Miller et al., 2012). NMFS
disagrees that behavioral response data
for sperm whales exposed to midfrequency active sonar (Miller et al.,
2012) is more appropriate than using
data from the airgun exposures
described by Miller et al. (2009) and
already considered within the Wood et
al. function. Furthermore, the
alternative recommendation of Nowacek
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et al. (2015), which is repeatedly
mentioned by NRDC as a more
appropriate alternative to Wood et al.
(2012), does not make a distinction
between sperm whales and other
odontocetes and instead advocates for a
criteria that treats all marine mammal
species the same (we address this in
greater detail below).
Regarding other odontocetes, NRDC’s
representation of the available scientific
information is also inaccurate. Miller et
al. (2005) specifically state that
‘‘[s]ighting rates at distances of 10–20
km from the airgun array were
significantly lower than those in areas
20–30 km from the airgun array, where
sighting rates were unexpectedly high’’
(i.e., the study indicates sighting rates of
beluga whales (Delphinapterus leucas)
were lower, not ‘‘100% avoidance’’ as
claimed by NRDC). Miller et al. (2005)
reported seven aerial beluga whale
sightings from 8 to 18 km from the
survey vessel and two vessel-based
beluga whale sightings at 1.5 and 2.5 km
from the survey vessel. Furthermore,
Southall et al. (2007) described the
findings of the Miller et al. (2005) study
as temporary avoidance behaviors at
these lower received levels, while
Gomez et al. (2016) (which NRDC agrees
reflects the best available science)
evaluated Miller et al. (2005) based on
a received level of 150 dB. Thus, the
Wood et al. (2012) approach does
capture responses associated with this
study.
Additionally, Wood et al. (2012) has
the advantage of accounting for
sensitive species such as beaked whales,
meaning that a response of a beaked
whale at 140 dB (as cited by NRDC) is
covered within the Wood et al. (2012)
recommended criteria (e.g., Wood et al.
assumes 90 percent of an exposed
beaked whale population will respond
at 140 dB). If Nowacek et al. (2015) was
instead used, as advocated by NRDC,
the probability of response would only
be 50 percent at 140 dB.
It should be noted that the systematic
review by Gomez et al. (2016), cited by
NRDC in support of their position,
found that received level was not
appropriate as the sole indicator of
behavioral response. For example, this
review shows that ‘‘low’’ effects were
actually found to reach peak probability
at a higher received level than
‘‘moderate’’ effects for baleen whales.
As we discussed in our notice of
proposed rulemaking, the results of the
Gomez et al. (2016) review are not
inconsistent with Wood et al. (2012).
With regard to NRDC’s comment that
the authors consider their results ‘‘nonconservative,’’ Gomez et al. (2016) only
indicates that they may have scored the
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severity of vocal responses higher if
they had more information on the
ecological significance of these types of
responses. There is no indication
elsewhere in Gomez et al. (2016) that
their overall results and analysis are
‘‘non-conservative.’’
NRDC repeatedly cites Nowacek et al.
(2015) in public comments. We note
first that while NRDC repeatedly refers
to this paper as a ‘‘study’’ (implying that
it presents new scientific data or the
results of new analyses of existing
scientific data), the paper (which is coauthored by the author of NRDC’s
comment letter) in fact makes policy
recommendations rather than presenting
any new science. The more substantive
reviews presented by Southall et al.
(2007) and Gomez et al. (2016) were
unable to present any firm
recommendations, as noted above. We
addressed the Nowacek et al. (2015)
approach relative to the Wood et al.
(2012) approach, in context of the best
available scientific information, in
detail in our notice of proposed
rulemaking. Then, as now, we found
that those recommendations are not
justified by the available scientific
evidence.
Other than suggesting a 50 percent
midpoint for a probabilistic function,
Nowacek et al. (2015) offer minimal
detail on how their recommended
probabilistic function should be
derived/implemented or exactly how
this midpoint value (i.e., 140 dB rms)
was derived (i.e., what studies support
this point). In contrast with elements of
a Level B harassment function that
NRDC indicates as important, Nowacek
et al. (2015) does not make distinctions
between any species or species groups
and provides no quantitative
recommendations for acknowledging
that behavioral responses can vary by
species group and/or behavioral context.
In summary, little substantive support is
provided by Nowacek et al. (2015) for
the proposal favored by NRDC. Few
studies are offered in support of the
recommended midpoint and the
proposal is offered only in a one-page
supplementary document. The Nowacek
et al. (2015) approach is not wellsupported scientific consensus, as
NRDC’s comment suggests.
Additionally, the application of the
Nowacek et al. (2015) approach
disregards the important role that
distance from a source plays in the
likelihood that an animal will respond
to a given received level from that
source type in a particular manner. By
assuming, for example, a 50 percent
midpoint at 140 dB rms, the approach
implies an unrealistically high
probability of marine mammal response
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to signals received at very far distances
from a source (e.g., greater than 50 km).
DeRuiter et al. (2013) found that beaked
whales exposed to similar received
levels responded when the sound was
coming from a closer source and did not
respond to the same level received from
a distant source. Although the Wood et
al. (2012) approach does not specifically
include a distance cut-off, the distances
at which marine mammals are predicted
to respond better comport with the
distances at which behavioral responses
have been detected and reported in the
literature.
NRDC also criticizes the use of
weighting functions in evaluating
potential Level B harassment, and
specifically criticizes use of the Mweighting scheme of Southall et al.
(2007). Gomez et al. (2016) suggest that
incorporation of frequency-weighting is
necessary to account for differential
hearing sensitivity, as behavioral
responses in cetaceans are best
explained by the interaction between
sound source type and functional
hearing group. That is, implementing
weighting functions allows for
consideration that different marine
mammal groups do not hear varying
frequencies of sound equally well. Thus,
it is appropriate to account for sounds
below a group’s best hearing range
having a lower likelihood of resulting in
a behavioral response (let alone that
animals are likely unable to effectively
detect sounds at frequencies completely
outside their hearing range).
The M-weighting functions are
described in Southall et al. (2007) as
‘‘intentionally precautionary (wide)’’ (as
opposed to the weighting functions used
in NMFS’ 2018 Revised Technical
Guidance 2 to account for noise-induced
hearing loss) and are used to account for
5343
the functional hearing ranges of
different marine mammal hearing
groups. This frequency weighting
scheme was intentionally selected
because it is more conservative in
accounting for hearing sensitivity (as is
appropriate in evaluating potential
Level B harassment) than are more
recently developed filters designed to
better assess potential noise-induced
hearing loss.
NRDC asserts that because Mweighting assumes that mid- and highfrequency (MF and HF) cetaceans are
relatively insensitive to noise below 1
kHz, it is likely that the incorporation of
M-weighting has a significant
downwards effect on take estimates.
This is incorrect. The table below
illustrates the impact of M-weighting
functions on frequencies ranging from
100 Hz to 1 kHz.
TABLE 3—IMPACT OF M-WEIGHTING FUNCTIONS ON FREQUENCIES RANGING FROM 100 Hz TO 1 kHz
Weighting (¥dB)
Hearing group
1 kHz
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Mid-frequency Cetaceans ................................................................................
High-frequency Cetaceans ..............................................................................
¥0.186 dB
¥0.034 dB
500 Hz
¥0.76 dB
¥1.33 dB
250 Hz
¥2.77 dB
¥4.45 dB
100 Hz
¥10 dB.
¥13.6 dB.
We see that, at 250 Hz and above, the
M-weighting functions do not result in
a significant reduction (less than 3 dB
for MF cetaceans and less than 5 dB for
HF cetaceans). Furthermore, the lower
bound of the functional hearing range of
these groups is 150 Hz for MF cetaceans
and 275 Hz for HF cetaceans (i.e.,
sounds below 100 Hz, where most
energy in airgun noise is found and
where M-weighting results in the
greatest reductions, are outside
functional hearing range). At 1 kHz,
where these species are most likely to be
able to detect and respond to airgun
noise, there is very little assumed
reduction in sensitivity.
Finally, NRDC advocates for the use
of a linear risk function as opposed to
the multiple step function of Wood et al.
(2012), stating that linear risk functions
are scientifically accepted methodology
that better acknowledge individuals
may vary in responsiveness. Although
NRDC does not specifically define what
they mean by ‘‘linear risk function,’’
NMFS assumes a linear risk function is
a smooth, continuous function, as
opposed to a function defined by
multiple steps, as is the case of Wood
et al. (2012) (and Nowacek et al. (2015),
which NRDC recommends as an
alternative to Wood et al.). NRDC states
that Wood et al. (2012) ‘‘has a
significant negative bias on take
estimates’’ where ‘‘all exposures from
140 dB to 159.9 dB are considered to
produce the same risk.’’ While it is true
that relying upon Wood et al. (2012)
results in all exposures within a
particular step (e.g., 140 dB and 159.9
dB) having the same risk, and future risk
functions may be further refined by
incorporating more steps, Wood et al.
(2012) better represents known variation
in behavioral responses at different
received levels than Nowacek et al.
(2015), which provides only a suggested
midpoint for a risk function without any
guidance on what should be done above
or below this midpoint, much less the
linear risk function NRDC states should
be used. Wood et al. (2012) does
acknowledge that responsiveness varies
with received levels, while relying on
broad steps, rather than a continuous
function. These broad steps allow for
easier implementation of a risk function
and are more practical for most users,
which is an important consideration,
especially in the context of users that
may not have the ability or access to
more sophisticated modeling (i.e., nonNavy users). Therefore, if new linear
risk functions become available, NMFS
may still provide a more simplistic
function broken down in broad steps, so
that it can be applied by all users.
In referencing NMFS’ proposal to use
the recommendations of Wood et al.,
and prior to even attempting to
characterize the scientific evidence,
NRDC states, ‘‘Incredibly [NMFS’]
approach produces take estimates that
are substantially lower than the muchcriticized, non-conservative, 160 dB
threshold [. . .].’’ NRDC (1)
mischaracterizes criticism of the historic
160-dB threshold as being about the
results of its use, rather than being about
whether it adequately represents the
best available science; (2) introduces an
MMPA standard that does not exist in
the statute (implying that NMFS is being
unlawfully or improperly ‘‘nonconservative’’); and (3) suggests that
NRDC favors whichever method of
evaluating potential Level B harassment
returns the highest estimate. This is
repeated later in their comment when
they assert that use of the Wood et al.
recommendations are ‘‘arbitrary and
capricious’’ because use of the
recommendations ‘‘appears, in its
results, even less conservative than the
outdated 160 dB threshold.’’ However,
2 NMFS. 2018. 2018 revision to: Technical
guidance for assessing the effects of anthropogenic
sound on marine mammal hearing (Version 2.0).
NOAA Technical Memorandum NMFS–OPR–59,
National Marine Fisheries Service: 178.
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selection of an evaluation scheme on the
basis of the results it returns, rather than
on how well the scheme reflects the
available scientific literature, would be
truly arbitrary and capricious and run
counter to our mandates.
Overall, we reiterate the lack of
scientific consensus regarding what
criteria might be most appropriate for
evaluating Level B harassment. Defining
sound levels that disrupt behavioral
patterns is difficult because responses
depend on complex, difficult to predict
contextual factors much more so than
received level. Therefore, levels at
which responses occur are not
necessarily consistent and can be
difficult to predict. However, although
better methods of assessing likely
behavioral response to acoustic stimuli
than the relatively simple multi-step
function used here may be forthcoming
from the scientific community, NMFS is
compelled to move forward with the
best available information. We believe
the recommendations of Wood et al.
(2012) reflect the best available science.
Comment: NRDC notes NMFS’
reference to a ‘‘preliminary analysis’’ in
the discussion of acoustic thresholds for
Level B harassment and asserts that
NMFS must make the analysis publicly
available and allow opportunity for
public comment before finalizing the
rule.
Response: Our use of the phrase
‘‘preliminary analysis’’ in the notice of
proposed rulemaking merits some
clarification. The particular analysis we
referred to is not in and of itself predecisional or preliminary. Rather, it is a
discrete analytical product with a result
that will not change—it is one way
(non-parametric regression method) of
looking at one subset (Malme et al.,
1984, 1988; Houser et al., 2013; Antunes
et al., 2014; Moretti et al., 2014) of the
data related to marine mammal
behavioral responses to intermittent
sound. NMFS conducted an analysis of
relevant data starting with the premise
of deriving a generic exposure-response
curve using previously published
exposure-response curves. This exercise
was conducted as part of an ongoing
separate and broader agency effort to
evaluate behavioral response data. We
also clarify that the Level B harassment
criteria for this rule did not
substantively rely upon that analysis.
Comment: NRDC claims that NMFS
misapplies the MMPA’s statutory
definition of harassment by adopting a
probability standard other than
‘‘potential’’ in setting thresholds for
auditory injury, stating that a take
estimate based on ‘‘potential’’ should
either count take from the lowest
exposure level at which hearing loss can
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occur or establish a probability function
that accounts for variability in the
acoustic sensitivity of individual marine
mammals. NRDC states that NMFS
instead derived auditory injury
thresholds from average exposure levels
at which tested marine mammals
experience hearing loss, which
discounts instances of hearing loss at
lower levels of exposure. The comment
further states that for purposes of take
estimation, thresholds based on mean or
median values will lead to roughly half
of an exposed cohort experiencing the
impacts that the threshold is designed to
avoid, at levels that are considered
‘‘safe,’’ therefore resulting in substantial
underestimates of auditory injury.
NRDC makes similar statements with
regard to the criteria for Level B
harassment.
Response: The 2018 Revised
Technical Guidance’s (NMFS, 2018)
onset thresholds for TTS for nonimpulsive sounds encompass more than
90 percent of available TTS data (i.e., for
mid-frequency cetaceans, only two data
points are below the onset threshold,
with maximum point only 2 dB below),
and in some situations 100 percent of
TTS data (e.g., high-frequency
cetaceans; although this group is datalimited). Thus, the 2018 Revised
Technical Guidance thresholds provide
realistic predictions, based on currently
available data, of noise-induced hearing
loss in marine mammals. For impulsive
sounds, data are limited to two studies,
and NMFS directly adopted the TTS
onset levels from these two studies for
the applicable hearing groups.
Our Federal Register notice
announcing the availability of the
original 2016 Technical Guidance (81
FR 51694; August 4, 2016; NMFS, 2016),
indicated that onset of auditory injury
(i.e., permanent threshold shift (PTS))
equates to Level A harassment under the
MMPA. We explained in that notice that
because the acoustic thresholds for PTS
conservatively predict the onset of PTS,
they are inclusive of the ‘‘potential’’
language contained in the definition of
Level A harassment. See 81 FR 51697,
51721.
Regarding Level B harassment, based
on the language and structure of the
definition of Level B harassment, we
interpret the concept of ‘‘potential to
disturb’’ as embedded in the assessment
of the behavioral response that results
from an act of pursuit, torment, or
annoyance (collectively referred to
hereafter as an ‘‘annoyance’’). The
definition refers to a ‘‘potential to
disturb’’ by causing disruption of
behavioral patterns. Thus, an analysis
that indicates a disruption in behavioral
patterns establishes the ‘‘potential to
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disturb.’’ A separate analysis of
‘‘potential to disturb’’ is not needed. In
the context of an ITR such as this, our
analysis is forward-looking. The inquiry
is whether we would reasonably expect
a disruption of behavioral patterns; if so,
we would conclude a potential to
disturb and therefore expect Level B
harassment. We addressed NRDC’s
concerns regarding the scientific
support for the Level B harassment
criteria in a previous comment
response.
Comment: NRDC raised concerns
regarding use of NMFS’ 2018 Revised
Technical Guidance (NMFS, 2018),
claiming that the guidance is not based
on the best available science and
underestimates potential auditory
injury. We also note that NRDC’s
comment references an attachment that
was not provided.
Response: The 2018 Revised
Technical Guidance (NMFS, 2018) is a
compilation, interpretation, and
synthesis of the scientific literature that
provides the best available information
regarding the effects of anthropogenic
sound on marine mammals’ hearing.
The 2016 Technical Guidance was
classified as a Highly Influential
Scientific Assessment and, as such,
underwent three independent peer
reviews, at three different stages in its
development, including a follow-up to
one of the peer reviews, prior to its
dissemination by NMFS. In addition,
there were three separate public
comment periods, during which time
NMFS received and responded to
similar comments on the guidance (81
FR 51694), and more recent public and
interagency review under Executive
Order 13795. While new information
may help to improve the guidance in the
future, and NMFS will review the
available literature to determine when
revisions are appropriate, the final
guidance reflects the best available
science and all information received
through peer review and public
comment. The concerns raised by NRDC
have been addressed by NMFS in
responses associated with the guidance
(see www.fisheries.noaa.gov/national/
marine-mammal-protection/marinemammal-acoustic-technical-guidance).
In light of these considerations, NRDC’s
argument that use of the guidance is
‘‘arbitrary and capricious’’ is
unpersuasive. As was stated in our
notice of proposed rulemaking, NMFS
considers the 2018 Revised Technical
Guidance to represent the best scientific
information currently available and,
given the incorporation of multiple peer
reviews and public comment
opportunities during its development,
we did not solicit and are not
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responding in detail to comments
concerning the contents of the
Technical Guidance (NMFS, 2016,
2018), as such comments are outside the
scope of this rulemaking.
NRDC also referenced information
related to occupational noise standards
established by the National Institute of
Occupational Safety and Health
(NIOSH). Human noise risk assessments
(NIOSH, 1998) are not equivalent (or
applicable) to thresholds provided in
the guidance, because they are used to
predict hearing loss based on a daily 8h exposure over 40 years (i.e., current
marine mammal TTS data are only
available to predict exposure periods of
24-h or less and cannot be used to assess
or predict risk associated with a lifetime
of exposure) and are based on larger
sample sizes of human listeners (e.g.,
NIOSH 1972 and 1997 risk assessments
were based on a sample size of 1,172
people). As pointed out in Wright
(2015), NIOSH criteria provide a 95
percent confidence interval for their
human noise standards but also allow
for an excess risk of material hearing
impairment, defined as an average
threshold elevation for both ears that
exceeds 25 dB, of eight percent (i.e.,
human noise standards limits do allow
for some risk; risk is not zero percent
and specifically that eight percent of the
population is still capable of developing
noise-induced hearing loss exceeding 25
dB when exposed to the 85 dB NIOSH
level).
Finally, we note that a group of
scientists recently published an update
to their original, seminal publication
concerning noise exposure criteria to
predict the onset of auditory effects in
marine mammals (Southall et al., 2007,
2019a), the topic of this comment. The
newer publication evaluates the
recommendations of the original
publication in light of subsequent
scientific findings, including those
findings that form the basis for the
recommendations of NMFS (2018).
While Southall et al. (2019a) provide
recommendations for future research
that could lead to revisions, the
fundamental aspects of an evaluation of
the onset of auditory effects for the
marine mammals considered in this ITR
(i.e., auditory weighting functions and
noise exposure criteria) are identical to
those presented by NMFS (2018) and
incorporated into the modeling process
developed for this ITR.
Sound Field Modeling
Comment: NRDC asserts that NMFS
has not appropriately accounted for
hard-bottom habitat in our propagation
analysis, stating that there are areas of
hard bottom in the GOM and that we
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cannot assume that proposed surveys
will take place entirely in areas with
soft or sandy bottoms.
Response: Sound propagation
modeling performed in support of
BOEM’s PEIS and this ITR was
developed to adequately represent a
wide range of conditions for a variety of
parameters, including bottom
composition. NMFS does not assume
that hard bottom does not exist in the
GOM, but rather that it is not
sufficiently predominant to warrant
specific representation in a propagation
modeling exercise covering the whole
GOM. As shown in Figure 50 of the
modeling report—depicting a
compilation of surficial sediment
composition available through a
hydrographic survey database from
NOAA’s National Ocean Service and its
predecessor, the U.S. Coast and
Geodetic Survey—muds and sands are
the dominant substrate types throughout
the GOM (as stated in our notice of
proposed rulemaking), with only small,
scattered areas of hard bottom. The
Minerals Management Service (MMS)
report cited by NRDC, which concerns
conversion of seafloor maps existing at
the time to MMS-approved GIS format
for use in geohazards evaluations, does
not contradict this.
Substrate types for propagation
modeling are based on grain size,
porosity, and shear velocity, etc., and do
not include ‘‘hard’’ or ‘‘coral’’ bottom. It
is also important to note that, while
some hard bottom habitats would
increase propagation due to increased
reflectivity, NRDC’s statement that coral
bottom can ‘‘significantly increase
propagation of airgun noise’’ is
erroneous. In fact, the roughness of the
coral habitat would cause severe bottom
loss due to scattering. As noted above,
bottom composition in the region is
mostly mud and sand and, therefore,
selection of parameter values associated
with these bottom types for propagation
modeling is appropriate. We also note
that, for the shelf region of the eastern
GOM, where sand is predominant, a
larger grain size value was selected to
account for this. The acoustic modeling
provided by Zeddies et al. (2015, 2017a)
appropriately and reasonably accounts
for variability in bottom composition
throughout the region.
The modeling process requires the use
of simplifying assumptions about
oceanographic and seabed parameters,
and these assumptions carry some
uncertainty, which may lead to
uncertainty in the form of variance or
error in individual model outputs and
in the final estimates of marine mammal
acoustic exposures. It is for this reason
that parametric uncertainty analysis was
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performed to evaluate the effects of this
uncertainty ‘‘envelope.’’ (This analysis
was summarized in our notice of
proposed rulemaking and described in
detail in the modeling report. NRDC
does not reference this assessment.)
Uncertainties in the results of acoustic
propagation modeling were estimated
by examining the variation in model
outputs when model inputs were offset
by realistic errors. The environmental
properties were selected so that the
median, or expected, value could be
compared to a worst-case outcome (e.g.,
assuming an extreme case of a more
reflective bottom), which was generated
by selecting extreme values for several
input parameters. These comparisons
represent the maximum errors in the
predicted sound fields that result from
incorrect specification of the parameters
tested. As described in the modeling
report, the greatest uncertainty due to
geoacoustic parameters of the sea
bottom is 4 dB (in the deep zone). The
effect of the geoacoustic uncertainty
increased when the sound speed profile
was downwardly refracting. In the case
of a surface channel (slope zone, winter
season), the average difference between
the median and worst-case was only 0.5
dB, i.e., in this case the geoacoustic
parameters had virtually no effect on the
sound levels at the top of the water
column (where marine mammals are
likely to be present).
Marine Mammal Densities
Comment: NRDC criticized NMFS’
use of the Roberts et al. (2016) model
outputs for purposes of deriving
abundance estimates, as used for
comparison to exposure estimates
herein. NRDC states that we should use
the NMFS Stock Assessment Report
(SAR) abundance estimates for this
purpose, while allowing that modelpredicted abundance estimates may be
used for ‘‘data-deficient’’ stocks. NRDC
implies that use of model-predicted
abundances would overestimate actual
abundances, apparently based on the
fact that the density models are
informed by many years of data rather
than only the most recent year of data.
Where model-predicted abundance
estimates are used, NRDC recommends
that we adjust the averaged model
outputs to the lower bound of the
standard deviation estimated by the
model for each grid cell.
Response: The approach
recommended by NRDC is
inappropriate. Comparing take estimates
generated through use of the outputs of
a density model to an unrelated
abundance estimate provides a
meaningless comparison. As explained
in our notice of proposed rulemaking,
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we compare the take estimates
generated through use of the density
outputs to the abundance predicted
through use of the model precisely to
provide a meaningful comparison of
predicted takes to predicted population.
The two potential sources of
abundance data—the output of cetacean
density models (Roberts et al., 2016)
and the available SARs data—provide
different results, with the SARs
estimates typically much lower.
Differences between the two separate
sets of abundance estimates result from
key methodological differences. In order
to produce sufficiently reliable and
detailed density surfaces (maps),
Roberts et al. (2016) combined multiple
NMFS cetacean surveys and modeled
density using a habitat-based approach
(Miller et al., 2013), while the SARs
estimates utilized only the most recent
NMFS survey and estimated density
using traditional distance sampling
(Buckland et al., 2001). The two
approaches, while compatible and based
on a common statistical framework
(distance sampling), can yield different
results, depending on complex factors
such as whether population sizes have
changed, or species habitat preferences
have shifted over time. Neither
approach will necessarily yield a higher
abundance estimate than the other, but
use of multiple years of data in
developing an abundance estimate
minimizes the influence of interannual
variation in over- or underestimating
actual abundance. By linking sightings
with environmental conditions, habitatbased density layers represent smoothed
surfaces that are not biased by
anomalous conditions. This makes them
particularly appropriate for the five-year
timeframe of this ITR, which will span
varying environmental conditions.
To illustrate why this smoothing of
interannual variation helps to create a
meaningful comparison to take
estimates, we provide the extreme
example of the GOM Clymene dolphin.
NMFS’ three most recent SAR
abundance estimates for this stock have
fluctuated between 129 and 17,355
animals, i.e., varying by a maximum
factor of more than 100. For most
species, such fluctuations across these
‘‘snapshot’’ abundance estimates (i.e.,
that are based on only the most recent
year of survey data) reflect interannual
variations in dynamic oceanographic
characteristics that influence whether
animals will be seen when surveying in
predetermined locations, rather than
any true increase or decline in
population abundance. In fact, NMFS’
SARs typically caution that trends
should not be inferred from multiple
such estimates, that differences in
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temporal abundance estimates are
difficult to interpret without an
understanding of range-wide stock
abundance, and that temporal shifts in
abundance or distribution cannot be
effectively detected by surveys that only
cover portions of a stock’s range (i.e.,
U.S. waters). The corresponding density
model for Clymene dolphins predicts a
mean abundance of 11,000 dolphins.
Therefore, in this example, NRDC
would have us compare takes predicted
by a model in which 11,000 dolphins
are assumed to exist against an
abundance estimate of 129 dolphins.
Our goal in assessing predicted takes is
to generate a meaningful comparison,
which is accomplished through use of
the model-predicted abundance.
A second key methodological
difference explains the tendency for the
model-predicted abundance estimates to
be higher than the SARs estimates. SAR
abundance estimates are typically
underestimates of actual abundance
because they do not account for bias on
the ability of observers to detect
animals—in contrast, Roberts et al.
(2016) do account for availability bias
and perception bias on the probability
of sighting an animal. Availability bias
occurs when a model assumes that
animals are always available to be
observed by the survey team when, in
fact, they are not. Cetaceans are diving
animals; while submerged, they are
unavailable. Assuming diving animals
are always available results in an
underestimation of abundance, because
while they are diving they are present
but not counted by the survey team.
Perception bias occurs when a model
assumes that animals will always be
detected when they are on the survey
trackline, when, in fact, detection is not
certain.
With regard to bias correction, NRDC
suggests that such corrections are
incorporated into NMFS’ GOM SARs.
However, some correction has been
performed only for the more-recently
surveyed shelf and coastal stocks of
bottlenose dolphin, i.e., four out of the
25 stocks of GOM marine mammals
considered herein. NRDC also strangely
suggests that ‘‘NMFS doesn’t show that
applying trackline correction factors
consistent with Barlow (2015), who
reported trackline detection
probabilities for marine mammals in the
Pacific, would result in population
estimates consistent with the ones the
agency has derived from Roberts et al.
(2016).’’ We can safely assume that
these would be consistent, given that
the models developed by Roberts et al.
(2016) considered, and in some cases
directly incorporated, the correction
factors of Barlow (1999) and Barlow and
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Forney (2007) (the original work upon
which Barlow (2015) builds).
These issues, which are typical for
NMFS’ SAR abundance estimates, are
particularly exacerbated for GOM
stocks. For the majority of stocks, the
most recent abundance estimates are
derived from the results of vessel-based
surveys in 2009, i.e., even if one
believes that such ‘‘snapshot’’ estimates
are most appropriate, the GOM
estimates are out of date and NMFS’
guidelines state that data greater than
eight years old should not be used for
abundance estimates. (We note that
more recent survey effort has been
conducted, but corresponding
abundance estimates have only recently
been made available via unpublished
draft SARs for most stocks that have yet
to be available for public comment or
finalized at the time the analyses were
completed for these regulations.) More
important for cryptic species, i.e., those
species that spend little time at the
surface and/or are difficult to detect
when at the surface, is the lack of any
bias correction. For example, the
Cuvier’s beaked whale—a cosmopolitan
species and perhaps the most
widespread and most commonly
observed species of beaked whale—is
officially estimated by NMFS to number
74 individuals in the GOM, a clear
underestimate. For purposes of
reference, current abundance estimates
for the U.S. Pacific and Atlantic
stocks—for which some bias corrections
have been made—are 3,274 and 5,744
individuals, respectively. Marine
mammal scientists working in the GOM
have acknowledged that the likely
abundance of beaked whales (and other
cryptic species, such as Kogia spp.)
should be expected to be closer to the
values predicted by Roberts et al. (2016)
than those given in the SARs. For
example, Dias and Garrison (2016) state
that current abundance estimates for
Kogia spp. may be considerably
underestimated due to the cryptic
behavior of these species and difficulty
of detection in Beaufort sea state greater
than one, while density estimates for
certain species derived from long-term
passive acoustic monitoring are much
higher than are estimates derived from
visual observations (e.g., Hildebrand et
al., 2015). Separately, NMFS’
announcement of a negative 90-day
finding on a petition to list the GOM
Cuvier’s beaked whale as endangered
(84 FR 11058) included adoption of the
abundance estimate of Roberts et al.
(2016) as being most appropriate.
Roberts et al. (2015b) summarize this
situation: ‘‘Because [NMFS’ SAR]
estimates are very low relative to the
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abundance we estimated, it is likely that
if our [density] results are used to
estimate population-level impacts from
potentially harmful human activities
(i.e. ‘‘takes’’, as defined by the Marine
Mammal Protection Act), the estimated
impacts will be very high [. . .].’’
NRDC suggests that the SARs are an
appropriate representation of ‘‘actual’’
abundance, whereas the Roberts et al.
(2016) predictions are not. NRDC also
appears to claim, without
substantiation, that an abundance
estimate derived from multiple years of
data would typically overestimate actual
abundance. However, these estimates
are not directly comparable—not
because one represents a ‘‘snapshot,’’
while one represents multiple years of
data—but because one does not correct
for one or more known biases against
the probability of observing animals
during survey effort, while the other
does. Because of this important caveat,
NMFS’ SAR abundance estimates
should not be considered ‘‘actual’’
abundance more than any other
accepted estimate. Therefore, when
multiple estimates of a stock’s
abundance are available, they should be
evaluated based on quality, e.g., does
the estimate account for relevant biases,
does it minimize the effect of
interannual variability, and,
importantly, should provide a
meaningful comparison. In this light,
our use of the Roberts et al. (2016)
abundance estimates are not a ‘‘radical
departure from past practice,’’ as
claimed by NRDC. Our practice, as
mandated by our implementing
regulations, is to use the best scientific
evidence available. NRDC states that
‘‘NMFS cannot simply discard this
Congressionally mandated estimate in
favor of the larger population estimates
derived from its misapplication of the
[. . .] model.’’ The statute does not
mandate use of the SARs for comparison
with take estimates.
Aside from their failure to explain the
claim of ‘‘misapplication,’’ and the
unwarranted implication that we must
make use of the model-generated
abundance estimates simply because
they are larger (and not because they are
the best available scientific
information), NRDC errs in asserting
that the MMPA requires that we use
SAR abundance estimates. Section 117
of the MMPA requires the development
of SARs, and dictates certain
information that SARs must provide.
However, there is no part of the MMPA
that requires the population abundance
estimates given in a SAR to be used in
any specific application and,
importantly, the MMPA does not even
require that the SAR include a best
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population estimate. The MMPA
requires only that SARs provide a
minimum population estimate, which is
used in the formulation of a potential
biological removal (PBR) level, which is
then required by section 118 of the
MMPA for certain uses in the
management of marine mammal take
incidental to commercial fisheries. In
summary, NRDC’s comment reflects an
inaccurate interpretation of the available
information, and NMFS disagrees with
the approach recommended by the
comment.
Take Estimates
Comment: The Associations state that
‘‘NMFS substantially overestimates the
number of incidental takes predicted to
result’’ from the specified activity. The
comment goes on to discuss the
modeling that is ‘‘intentionally designed
to overestimate takes,’’ and discusses
the findings of the Acoustic Exposure
Model Variable Analysis (Zeddies et al.,
2017b) (which was provided for public
review in association with the proposed
rule). Other industry commenters and
the CRE echo these points.
Response: The commenters’
statements that NMFS has substantially
overestimated takes are incorrect. We
used current scientific information and
state-of-the-art acoustic propagation and
animal movement modeling to
reasonably estimate potential exposures
to noise. Chevron stated that the
modeling used ‘‘admittedly erroneous
models’’ but provides no supporting
information or citation. Chevron further
describes ‘‘errors in methodology’’ and
‘‘admissions’’ that the modeling
methodology and the data used are not
‘‘rigorous science,’’ while asserting that
NMFS ‘‘repeatedly rejects and omits
science that is available.’’ Chevron’s
comments do not provide any
illumination as to what specifically
these errors may be, what data it
believes is flawed, or what ‘‘science’’
NMFS has rejected or omitted. NMFS
has considered all relevant available
scientific information.
To summarize in a basic way, it is
foreseeable that a large amount of noiseproducing activity, such as BOEM’s
application and PEIS describe, results in
a substantial number of predicted
acoustic exposures. Despite
recommending that ‘‘a better approach
would be to use the best and most likely
values for all of the input variables to
the model,’’ the Associations’ comments
do not include substantive
recommendations for improvement.
They do not specify which of the many
data inputs are ‘‘conservative’’ or to
what degree, nor do they recommend
alternatives to the choices that were
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painstakingly documented in
developing the modeling.
As was noted in the notice of
proposed rulemaking, NMFS disagrees
with the Associations’ characterization
of the modeling and with certain
statements in BOEM’s draft PEIS
regarding the modeling that are
frequently cited by the Associations. As
we stated in the notice, BOEM’s draft
PEIS included unsupported and
erroneous statements that characterized
the modeling results—which BOEM and
NMFS developed collaboratively—as
‘‘unrealistically high,’’ ‘‘overly
conservative,’’ and representative of a
‘‘worst-case scenario,’’ among other
things. These statements were included
in that document without NMFS’ prior
knowledge. Importantly, as a result of
NOAA’s public comments on that draft
PEIS in its role as a cooperating agency,
the statements referenced by the
commenters were properly removed
from the final PEIS, which more
accurately characterizes the modeling
process and results.
The Associations take out of context
a number of statements from the
discussion in NMFS’ notice of proposed
rulemaking of the modeling process,
data inputs, and user selections. We
address these in turn:
• The Associations quote NMFS as
stating that our modeling likely ‘‘leads
to substantial overestimates of the
numbers of individuals potentially
disturbed [and] . . . to an
overestimation of the population-level
consequences of the estimated
exposures’’ and that, even with the
application of a correction factor, the
modeling still represents an
‘‘overestimate.’’ (83 FR 29261, 29291).
But the full statement in our notice is as
follows: ‘‘While the modeling provides
reasonable estimates of the total number
of instances of exposure exceeding
Level B harassment criteria, it is likely
that it leads to substantial overestimates
of the numbers of individuals
potentially disturbed, given that all
animals within the areas modeled are
unlikely to be completely replaced on a
daily basis. Therefore, in assuming an
increased number of individuals
impacted, these results would lead to an
overestimation of the potential
population-level consequences of the
estimated exposures.’’ Our point was
that, although the modeling provides
reasonable estimates of the total amount
of acoustic exposures, it would be an
overestimate to interpret this total as
representative of the number of
individuals impacted. We then
discussed our development of a
correction factor to address this issue
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(see Table 12 of the notice of proposed
rulemaking).
• The Associations highlight our
‘‘admission’’ that the modeling is
purposely conservative. We address this
below by explaining why, in some
cases, it is appropriate to make
reasonably conservative choices.
• The Associations mischaracterize
the Wood et al. (2012) Level B
harassment criteria as ‘‘expressly
rejecting the best available science.’’ In
discussing different versions of
frequency weighting functions, we
stated that ‘‘Type III filters’’ are better
designed to predict the onset of auditory
injury, while explaining why use of
‘‘Type I filters’’ (or M-weighting) was
appropriate for use in evaluation of
Level B harassment (83 FR 29248). The
Type III filters, as adopted by NMFS
(2018), were appropriately used for
evaluation of Level A harassment
(which includes auditory injury).
• Although characterized as
‘‘conservative’’ NMFS has made
reasonable choices through the
application of professional judgment by
subject matter experts. For example,
using single airgun modeling results in
lieu of boomer results was a choice
made for computational efficiency
precisely because it was not
significantly influential on the results.
(83 FR 29251). And selecting an
estimate for standard deviation in an
investigation of model sensitivity to
source level variance was in response to
a concern of the commenters—overall
sensitivity of the model to uncertainty
in input parameters and the resulting
uncertainty in model results—and had
no bearing on the model results (83 FR
29257).
• The Associations also highlight our
statement that ‘‘the lack of aversion
within the animal movement modeling
process results in overestimates of
potential injurious exposure,’’ without
noting that we corrected this issue
through a post-hoc correction to
reasonably account for aversion.
The modeling required that a number
of assumptions and choices be made by
subject matter experts and, in most
cases, the most representative data or
methods were used. As we
acknowledged, in some cases, some
assumptions or choices are purposely
conservative (where the conservative
choice is reasonable) to minimize the
likelihood of underestimating the
potential impacts on marine mammals
represented by a specified level of
survey effort. These are reasonable,
scientifically acceptable choices that do
not create, as the Associations state,
‘‘multiplicatively accumulating bias as
the conservative assumptions interact
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with each other to multiply
uncertainty’’). To the extent that the
results of the modeling may be
conservative, they are the most credible,
science-based information available at
this time (assuming the notional 8,000
in3 array and activity level projections
specified by BOEM in the petition).
These comments provide no
reasonable justification as to why the
modeling results in overestimates of
take. The Associations instead seem to
rely on the incorrect premise that realtime mitigation would somehow reduce
actual levels of acoustic exposure
(versus reducing the duration and/or
intensity of exposure). NMFS disagrees
that ‘‘each of the inputs is purposely
developed to be conservative’’—again,
the Associations do not provide any
support for this assertion, and none is
to be found in the administrative record
for this action. Although it may be
correct that some conservativeness
accumulates throughout the analysis,
the Associations do not adequately
describe the nature of conservativeness
associated with model inputs or the
degree to which such conservativeness
‘‘accumulates’’ (either quantitatively or
qualitatively), nor do they offer more
appropriate alternatives.
The modeling effort incorporated
representative sound sources and
projected survey scenarios (both based
on the best available information
obtained by BOEM), physical and
geological oceanographic parameters at
multiple locations within the GOM and
during different seasons, the best
available information regarding marine
mammal distribution and density, and
available information regarding known
behavioral patterns of the affected
species. Current scientific information
and state-of-the-art acoustic propagation
and animal movement modeling were
used to reasonably estimate potential
exposures to noise. The notice of
proposed rulemaking described all
aspects of the modeling effort in
significant detail, including numerous
investigations (test scenarios) designed
by the agencies to understand various
model sensitivities and the effects of
certain choices on model results. The
modeling report itself was provided for
public review, in association with both
BOEM’s PEIS and NMFS’ notice of
proposed rulemaking.
We quote the Marine Mammal
Commission’s public comment on this
topic: ‘‘Complex sound propagation and
animat modeling was used to estimate
the numbers of potential takes from
various types of geophysical surveys in
the Gulf. NMFS received comments
from industry operators suggesting that
the modeling results were overly
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conservative and that the take estimates
were ‘higher than BOEM expects would
actually occur in a real world
environment.’ However, the
Commission has reviewed the modeling
approach and parameters used to
estimate takes and believes they
represent the best available information
regarding survey scenarios, sound
sources, physical and oceanographic
conditions in the Gulf, and marine
mammal densities and behavior. As
such, the Commission agrees with
NMFS and BOEM that the resulting take
estimates were conservative but
reasonable, thereby minimizing the
likelihood that actual takes would be
underestimated.’’
The CRE says, absent citation or
reference, that ‘‘everyone agrees’’ that
takes are overestimated. Their assertion
that we ‘‘greatly overestimate both
exposures and takes’’ is based on their
view that we relied on ‘‘flawed models
and on Risk Assessment Frameworks
that are unfinished and have not been
peer reviewed.’’ While the Associations
focus on supposed conservatism built
into the modeling process, the CRE
appears to believe that there is some
unknown process by which modeled
exposures are ‘‘converted’’ to takes.
(‘‘These take overestimates stem
primarily from [NMFS’] use of various
models to convert exposures to takes
[. . .]. They have no credible framework
for converting exposure to takes.’’) We
believe the CRE is likely referring to the
EWG risk assessment framework, which
is a systematic analysis used as an aid
to understanding the significance of the
modeled takes to the affected stocks.
However, this framework plays no role
in the estimation of takes (takes are an
input to the EWG framework) and is not
itself a ‘‘model.’’ CRE also makes the
claim, addressed elsewhere in this
response, that the take estimates ‘‘do not
include the impact of mitigation
measures.’’
Regarding the modeling variable
analysis submitted by the Associations
(Zeddies et al., 2017b), we have fully
considered the results in developing
this final ITR,3 but do not find that the
3 The Associations misunderstand the timeline
relating to the availability of the report for NMFS’
consideration for developing the proposed rule.
(‘‘NMFS inexplicably dismisses [the report] as being
provided too late despite the fact that it was
provided to NMFS 11 months ago’’). We must
correct the record on this point. The analysis was
submitted by IAGC for NMFS’ consideration on
September 6, 2017, well after the total 45-day
comment period on the petition had closed (81 FR
88664 (December 8, 2016, notice of receipt of
petition providing for 30-day comment period); 81
FR 92788 (extending comment period an additional
15 days to January 23, 2017)). The final PEIS was
then issued in August 2017. Subsequent materials
could no longer be considered as NMFS prepared
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analysis supports any changes to the
modeling. IAGC and API contracted
with JASCO Applied Sciences, which
performed the original modeling effort,
to conduct additional analysis regarding
the effect that various acoustic model
parameters or inputs have on the
outputs used to estimate numbers of
animals exposed to threshold levels of
sound from geophysical sources used in
the GOM. The analysis investigated five
factors:
• Airgun array size (including total
volume, number of array elements,
element air pressure, array geometry
and spacing) used in source and
propagation models;
• Acoustic threshold criteria and
associated weighting used to calculate
exposures;
• Animal densities used for adjusting
simulated computer model exposures to
potential real-world animal exposures;
• Natural aversive behaviors of
marine mammals; and
• The addition of mitigative measures
that lessen the potential for animals’
exposure to threshold levels of seismic
sound.
The primary finding of the Acoustic
Exposure Model Variable Analysis is
that use of appropriate acoustic injury
criteria (i.e., NMFS, 2016, 2018)
decreased predictions of injurious
exposure. At the time the Associations
submitted this report, they were
apparently unaware that, as described
herein, NMFS had already made the
change that the Associations’ analysis
indicates is most significant: The
appropriate acoustic injury criteria (i.e.,
NMFS, 2016, 2018), representing the
best available science, were used in
NMFS’ analysis in the proposed rule.
Other significant investigations in the
Associations’ modeling variable analysis
included an alternative array size and
quantitative consideration of animal
aversion and mitigation effectiveness.
We address these below.
The Associations state that the
selected array (8,000 in3) is
unrealistically large, resulting in an
overestimation of likely source levels
and, therefore, size of the sound field
with which marine mammals would
interact. Zeddies et al. (2017b)
the draft proposed rule for interagency review. The
rule was submitted to OMB on October 3, 2017.
Upon submission, no further changes could be
made to the rule other than those arising pursuant
to the interagency review. The Office of Information
and Regulatory Affairs cleared the proposed rule on
June 11, 2018, whereupon it was submitted to the
Federal Register on June 12 and published on June
22. Therefore, the analysis was not able to be
considered by NMFS in the notice of proposed
rulemaking despite the length of time between
submission of the report to NMFS and publication
of the proposed rule.
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evaluated the use of a substitute 4,130
in3 array, finding that reduction in array
volume reduces the number of predicted
exposures. Use of a smaller airgun array
volume with lower source level
unsurprisingly creates a smaller
ensonified area resulting in fewer
numbers of animals expected to exceed
exposure thresholds. However, selection
of the representative array to be used in
the modeling was directed by the ITR
applicant (i.e., BOEM). Given that the
array used was selected by the applicant
and included in the petition for the ITR
(which was available for public
comment in our Federal Register notice
of receipt of BOEM’s application), any
complaint regarding this or other
aspects of the specified activity,
including activity level projections and
representative source characteristics or
survey geometry, should be addressed to
BOEM. According to BOEM, the
particular array was selected as a
realistic representative proxy after
BOEM’s discussions with individual
geophysical companies. An 8,000-in3
array was considered reasonable, as it
falls within the range of typical airgun
arrays currently used in the GOM,
which are roughly 4,000–8,475 in3
(BOEM, 2017). According to BOEM’s
permitting records, approximately onethird of arrays used in a recent year
were 8,000 in3 or greater. Also, as noted
previously, regardless of the
representative airgun array size used to
model the number of takes of marine
mammals for the purposes of the
analysis conducted in this rule, the
analysis of the take and the associated
findings are applicable to take incurred
from the use of other sizes of airgun
arrays, including smaller ones such as
those modeled in the Acoustic Exposure
Model Variable Analysis report.
The Associations’ comments also
focus significantly on the need to
incorporate quantitative adjustments to
account for aversion and mitigation. As
discussed in the notice of proposed
rulemaking, the effects of mitigation and
aversion on exposure estimates were
investigated via test scenarios, and
NMFS acknowledges that both of these
factors would lead to a reduction in
likely injurious exposure to some
degree. (As noted above, the issue of
aversion was addressed via post-hoc
quantitative adjustment). Ultimately
these factors were not quantified in the
modeling because, in summary, there is
too much inherent uncertainty regarding
the effectiveness of detection-based
mitigation for these activities to support
any reasonable quantification of its
effect in reducing injurious exposure,
and there is too little information
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regarding the likely level of onset and
degree of aversion to justify its use in
the modeling via precise quantitative
control of animat movements (as
compared to post-hoc adjustment of the
modeling results, as is done here).
Zeddies et al. (2017b) found that
incorporation of aversion into the
modeling process appears to reduce the
number of predicted injurious
exposures, though the magnitude of the
effect was variable. The authors state
that this variability is likely because
there are few samples of injurious
exposure exceedance, meaning that the
statistical variability of re-running
simulations is evident.
While aversion and mitigation
implementation are expected to reduce
somewhat the modeled levels of
injurious exposure, it is important to
note that they would not be expected to
result in any meaningful reduction in
assumed exposures resulting in Level B
harassment, nor in total takes by
harassment, as any averted injurious
(Level A harassment) takes would not be
alleviated, but rather would be
appropriately changed to behavioral
disturbance (Level B harassment) takes.
The Associations, acknowledging the
analysis we have done to produce more
realistic estimates of potential Level A
harassment, are focused on the
supposed overestimation of Level B
harassment. Yet their focal areas of
complaint are limited to array size,
which is a decision made by BOEM, and
mitigation effectiveness, a factor that
would have no effect on the amount of
predicted Level B harassment. With
regard to the large number of other data
inputs and/or choices made in the
modeling, the Associations conclude
that ‘‘NMFS has admittedly chosen
conservative numerical values to assess
allegedly uncertain variables to
overestimate adverse effects,’’ without
specifically identifying a single issue
where they feel a meaningful data or
process error was made.
Comment: The CRE recommends a
different method of estimating potential
take of marine mammals, stating that
NMFS ‘‘should continue to use Line
Transect to estimate exposures and
takes.’’
Response: Although CRE does not
actually describe the method they
recommend, we infer that they are
referencing a relatively simplistic
method historically used in estimating
acoustic exposures, typically on a
survey-specific basis. Essentially, this
methodology consists of: (1)
Determination of estimated isopleth
ranges from the source for a specified
acoustic threshold (nominally this
threshold was historically the 160 dB
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rms received level for Level B
harassment); (2) assumption that a
cylinder whose radius matched the
range to these isopleths and
encompassed the entire water column
was ensonified to that threshold; (3)
calculating the surface area ensonified
by this water column as the source
moved along its track; and (4)
multiplying that resultant ensonified
surface area by the density of each
marine mammal species present to
estimate potential harassment takes.
(Note that this process is somewhat
more complicated for evaluation of 3D
surveys.) In this case, following a
modeling workshop held in 2014 as a
collaborative effort between the
American Petroleum Institute (API) and
the International Association of
Geophysical Contractors (IAGC), NMFS,
and BOEM, the agencies determined
that it would be most appropriate to
collaborate on a more sophisticated
approach, in which more detailed
modeling of the source and its
properties, the acoustic propagation
field in three dimensions, and three
dimensional animal placement and
movement is used to better calculate the
potential impacts to marine mammals.
To summarize aspects of the process:
• Operational Scenario Development:
According to BOEM, the source and
operations scenarios presented in the
petition and which underlie the
modeling effort were based on historical
permit information. BOEM sought
industry input and used historical data
to develop the specification of the
nominal airgun array. The array
specifications and level of survey effort
were intended to be representative of
future activity, not a conservative overestimate.
• Acoustic Modeling: The
propagation model output has been
compared with measured data and been
shown to be reliable. The physical
inputs to the model are the best
available data. The full sound field was
used to predict exposures, not a
‘maximum over depth’ simplification.
• Animal Modeling: The animal
movement model used is one of the few
models available that incorporates full
four-dimensional movement. Properly
applied, such models provide the most
accurate predictions of acoustic
exposure.
• Animal Density: The density and
distribution data used were the best
available and represent the latest
synthesis and analysis.
• Effects Criteria: The historical Level
B harassment threshold of 160 dB has
been criticized for multiple reasons, and
the use of the Wood et al. (2012) criteria
in this analysis allows for the
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application of current scientific
information to address some of the
issues raised. The best available science
relating to potential auditory injury, as
synthesized in NMFS (2018) and more
recently described by Southall et al.
(2019a), was used in the modeling
effort.
Taking advantage of these more
sophisticated tools allows for a more
accurate and detailed model of the
exposures of a population of marine
animals in the three dimensions and
time, and also provides: (1) Statistical
data on each individually modeled
animal and the population as a whole;
(2) rate of exposure (threshold
exceedance per unit time) over the
duration of a survey; and (3) the data
necessary to determine effects based on
more sophisticated thresholds, such as
cumulative sound exposure level. A
comparison of these methods—animat
method involving three-dimensional
animal movement modeling and static
distribution, in which a static twodimensional density is overlaid on a
simplified representation of the sound
field—found that differences
consistently arise between the two
methods. The static distribution method
was found to consistently underestimate
the number of takes by Level B
harassment compared with the animat
method. In addition, repeating many
simulations with the animat method
provides a more robust risk assessment
and provides a better measure of
variability (Schecklman et al., 2011).
We agree with CRE (and our own
statements, as cited by CRE) that
sophisticated modeling is not a
requirement of the MMPA process.
However, all take estimation requires
the use of modeling; the difference
between various approaches to
estimating take is the degree of
sophistication of the modeling approach
employed. We note that the National
Science Foundation (NSF) typically
utilizes the method espoused by CRE in
take authorization requests for specific
surveys. In order to derive the necessary
estimated isopleth distance, NSF
applications typically use Nucleus (a
source model) in conjunction with ray
trace modeling to approximate
propagation of the acoustic signatures.
The modeling developed by BOEM and
NMFS supports both BOEM’s 2017 PEIS
and the analyses conducted for this
rulemaking, and additionally is
available for use in supporting LOA
applications to maximize efficiency of
the LOA process for disparate
applicants. However, we have made
clear that LOA applicants are free to
pursue a different method of estimating
takes than the modeling effort
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developed collaboratively by NMFS and
BOEM. Use of a different analytical
method in support of an LOA
application will necessarily require
additional review.
CRE compares ‘‘Line Transect’’
modeling performed in support of a
2004 Minerals Management Service
Environmental Assessment to that
developed in support of this effort,
stating that the take estimates generated
in that effort are ‘‘orders of magnitude
smaller than the take estimates’’
evaluated here. CRE’s erroneous
implication is that the only difference
between the two efforts is the modeling
approach. (‘‘The great difference
between GOM takes as estimated by
Line Transect, and as estimated by
[NMFS]’s current models, demonstrates
just how inaccurate and exaggerated the
model take estimates are.’’) However,
the inputs to the two efforts are
significantly different. Most notably, the
assumptions relating to projected effort,
animal occurrence, and sound source
output are not comparable. Effort
projections for the 2004 modeling were
roughly 53 percent of those given by
BOEM for the high effort scenario in the
PEIS, and included only relatively
archaic 3D survey geometries, versus the
more complex azimuth designs and coil
surveys considered herein. Advances in
cetacean density modeling provide
estimates for use here that are, in some
cases, multiple orders of magnitude
greater than the poor estimates used in
the 2004 effort. The 15-year old
modeling held up by CRE as a good
example assumed a 4,550 in3 acoustic
source with a uniform 3 km isopleth
distance to the 160-dB rms threshold.
BOEM specified use of an 8,000 in3
acoustic source for the modeling effort
here, with a mean distance to the 160
dB isopleths of 12.7 km, but even more
recent modeling of a more comparable
source (4,130 in3) shows that the
isopleth distance may be as large as 8.4
km, depending on the season (Zeddies
et al., 2017b). Moreover, the 2004
modeling reduced even that ensonified
area by an arbitrary 50 percent to
account for an ‘‘elliptical zone of
ensonification.’’ It is clear that the two
modeling efforts are in no way
comparable.
Comment: NRDC asserts that NMFS
fails to account for forms of injury that
are reasonably anticipated, stating that
permanent hearing loss (i.e., Level A
harassment) may occur through
mechanisms other than PTS, and that
behaviorally-mediated injury may occur
as a result of exposure to airgun noise.
NRDC states that NMFS must account
for these mechanisms in its assessment
of potential injury.
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Response: NMFS is aware of the work
by Kujawa and Liberman (2009), which
is cited by NRDC. The authors report
that in mice, despite completely
reversible threshold shifts that leave
cochlear sensory cells intact, there were
synaptic level changes and delayed
cochlear nerve degeneration. However,
the large threshold shifts measured (i.e.,
maximum 40 dB) that led to the
synaptic changes shown in this study
are within the range of the large shifts
used by Southall et al. (2007, 2019a) and
in NMFS’ 2018 Revised Technical
Guidance to define PTS onset (i.e., 40
dB). It is unknown whether smaller
levels of TTS would lead to similar
changes or what may be the long-term
implications of irreversible neural
degeneration. The effects of sound
exposure on the nervous system are
complex, and this will be re-examined
as more data become available. It is
important to note that NMFS’ 2018
Revised Technical Guidance
incorporated various conservative
factors, such as a 6-dB threshold shift to
represent TTS onset (i.e., minimum
amount of threshold shift that can be
differentiated in most experimental
conditions); the incorporation of
exposures only with measured levels of
TTS (i.e., did not incorporate exposures
where TTS did not occur); and assumed
no potential of recovery between
intermittent exposures. NMFS disagrees
that consideration of likely PTS is not
sufficient to account for reasonably
expected incidents of auditory injury.
There is no conclusive evidence that
exposure to airgun noise results in
behaviorally-mediated forms of injury.
Behaviorally-mediated injury (i.e., mass
stranding events) has been primarily
associated with beaked whales exposed
to mid-frequency active (MFA) navy
sonar. Military tactical sonar and the
alerting stimulus used in Nowacek et al.
(2004) are very different from the noise
produced by airguns. One should
therefore not expect the same reaction to
airgun noise as to these other sources.
Yet NRDC infers that because strandings
of beaked whales have been correlated
with navy MFA sonar use, strandings
are also likely to occur due to seismic
surveys. As explained below, navy MFA
sonar is very different from airguns, and
it is not reasonable to assume that
airguns will cause the same effects as
navy MFA sonar (including strandings).
To understand why navy MFA sonar
affects beaked whales differently than
airguns do, it is important to note the
distinction between behavioral
sensitivity and susceptibility to auditory
injury. To understand the potential for
auditory injury in a particular marine
mammal species in relation to a given
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acoustic signal, the frequency range the
species is able to hear is critical, as well
as the species’ auditory sensitivity to
frequencies within that range. Current
data indicate that not all marine
mammal species have equal hearing
capabilities across all frequencies and,
therefore, species are grouped into
hearing groups with generalized hearing
ranges assigned on the basis of available
data (Southall et al., 2007, 2019a).
Hearing ranges as well as auditory
sensitivity/susceptibility to frequencies
within those ranges vary across the
different groups. For example, in terms
of hearing range, the high-frequency
cetaceans (e.g., Kogia spp.) have a
generalized hearing range of frequencies
between 275 Hz and 160 kHz, while
mid-frequency cetaceans—such as
dolphins and beaked whales—have a
generalized hearing range between 150
Hz to 160 kHz. Regarding auditory
susceptibility within the hearing range,
while mid-frequency cetaceans and
high-frequency cetaceans have roughly
similar hearing ranges, the highfrequency group is much more
susceptible to noise-induced hearing
loss during sound exposure, i.e., these
species have lower thresholds for these
effects than other hearing groups
(NMFS, 2018). Referring to a species as
behaviorally sensitive to noise simply
means that an animal of that species is
more likely to respond to lower received
levels of sound than an animal of
another species that is considered less
behaviorally sensitive. So, while
dolphin species and beaked whale
species—both in the mid-frequency
cetacean hearing group—are assumed to
(generally) hear the same sounds
equally well and be equally susceptible
to noise-induced hearing loss (auditory
injury), the best available information
indicates that a beaked whale is more
likely to behaviorally respond to that
sound at a lower received level
compared to an animal from other midfrequency cetacean species that is less
behaviorally sensitive. This distinction
is important because, while beaked
whales are more likely to respond
behaviorally to sounds than are many
other species (even at lower levels), they
cannot hear the predominant, lower
frequency sounds from seismic airguns
as well as sounds that have more energy
at frequencies that beaked whales can
hear better (such as navy MFA sonar).
Navy MFA sonar affects beaked
whales differently than airguns do
because it produces energy at different
frequencies than airguns. Mid-frequency
cetacean hearing is generically thought
to be best between 8.8 to 110 kHz, i.e.,
these cutoff values define the range
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above and below which a species in the
group is assumed to have declining
auditory sensitivity, until reaching
frequencies that cannot be heard
(NMFS, 2018). However, beaked whale
hearing is likely best within a higher,
narrower range (20–80 kHz, with best
sensitivity around 40 kHz), based on a
few measurements of hearing in
stranded beaked whales (Cook et al.,
2006; Finneran et al., 2009; Pacini et al.,
2011) and several studies of acoustic
signals produced by beaked whales (e.g.,
Frantzis et al., 2002; Johnson et al.,
2004, 2006; Zimmer et al., 2005). While
precaution requires that the full range of
audibility be considered when assessing
risks associated with noise exposure
(Southall et al., 2007, 2019a), animals
typically produce sound at frequencies
where they hear best. More recently,
Southall et al. (2019a) suggested that
certain species amongst the historical
mid-frequency hearing group (beaked
whales, sperm whales, and killer
whales) are likely more sensitive to
lower frequencies within the group’s
generalized hearing range than are other
species within the group and state that
the data for beaked whales suggest
sensitivity to approximately 5 kHz.
However, this information is consistent
with the general conclusion that beaked
whales (and other mid-frequency
cetaceans) are relatively insensitive to
the frequencies where most energy of an
airgun signal is found. Navy MFA sonar
is typically considered to operate in the
frequency range of approximately 3–14
kHz (D’Amico et al., 2009), i.e., outside
the range of likely best hearing for
beaked whales but within or close to the
lower bounds, whereas most energy in
an airgun signal is radiated at much
lower frequencies, below 500 Hz
(Dragoset, 1990).
It is important to distinguish between
energy (loudness, measured in dB) and
frequency (pitch, measured in Hz). In
considering the potential impacts of
mid-frequency components of airgun
noise (1–10 kHz, where beaked whales
can be expected to hear) on marine
mammal hearing, one needs to account
for the energy associated with these
higher frequencies and determine what
energy is truly ‘‘significant.’’ Although
there is mid-frequency energy
associated with airgun noise (as
expected from a broadband source and
as we acknowledged in the notice of
proposed rulemaking), airgun sound is
predominantly below 1 kHz (Breitzke et
al., 2008; Tashmukhambetov et al.,
2008; Tolstoy et al., 2009). As stated by
Richardson et al. (1995), ‘‘[. . .] most
emitted [seismic airgun] energy is at 10–
120 Hz, but the pulses contain some
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energy up to 500–1,000 Hz.’’ Tolstoy et
al. (2009) conducted empirical
measurements, demonstrating that
sound energy levels associated with
airguns were at least 20 decibels (dB)
lower at 1 kHz (considered ‘‘midfrequency’’) compared to higher energy
levels associated with lower frequencies
(below 300 Hz) (‘‘all but a small fraction
of the total energy being concentrated in
the 10–300 Hz range’’ [Tolstoy et al.,
2009]), and at higher frequencies (e.g.,
2.6–4 kHz), power might be less than 10
percent of the peak power at 10 Hz
(Yoder, 2002). Energy levels measured
by Tolstoy et al. (2009) were even lower
at frequencies above 1 kHz. In addition,
as sound propagates away from the
source, it tends to lose higher-frequency
components faster than low-frequency
components (i.e., low-frequency sounds
typically propagate longer distances
than high-frequency sounds) (Diebold et
al., 2010). Although higher-frequency
components of airgun signals have been
recorded, it is typically in surfaceducting conditions (e.g., DeRuiter et al.,
2006; Madsen et al., 2006) or in shallow
water, where there are advantageous
propagation conditions for the higher
frequency (but low-energy) components
of the airgun signal (Hermannsen et al.,
2015). This should not be of concern
because the likely behavioral reactions
of beaked whales that can result in acute
physical injury would result from noise
exposure at depth (because of the
potentially greater consequences of
severe behavioral reactions) and
because, even if near-surface exposure
to such higher-frequency components
were of concern, oceanographic
conditions in the GOM do not
consistently support such ducting
conditions. In summary, the frequency
content of airgun signals is such that
beaked whales will not be able to hear
the signals well (compared to MFA
sonar), especially at depth where we
expect the consequences of noise
exposure could be more severe.
Aside from frequency content, there
are other significant differences between
MFA sonar signals and the sounds
produced by airguns that minimize the
risk of severe behavioral reactions that
could lead to strandings or deaths at sea,
e.g., significantly longer signal duration,
horizontal sound direction, typical fast
and unpredictable source movement.
All of these characteristics of MFA
sonar tend towards greater potential to
cause severe behavioral or physiological
reactions in exposed beaked whales that
may contribute to stranding. Although
both sources are powerful, MFA sonar
contains significantly greater energy in
the mid-frequency range, where beaked
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whales hear better. Short-duration, high
energy pulses—such as those produced
by airguns—have greater potential to
cause damage to auditory structures
(though this is unlikely for midfrequency cetaceans, as explained later
in this document), but it is longer
duration signals that have been
implicated in the vast majority of
beaked whale strandings. Faster, less
predictable movements in combination
with multiple source vessels are more
likely to elicit a severe, potentially antipredator response. Of additional interest
in assessing the divergent characteristics
of MFA sonar and airgun signals and
their relative potential to cause
stranding events or deaths at sea is the
similarity between the MFA sonar
signals and stereotyped calls of beaked
whales’ primary predator: The killer
whale (Zimmer and Tyack, 2007).
Although generic disturbance stimuli—
as airgun noise may be considered in
this case for beaked whales—may also
trigger antipredator responses, stronger
responses should generally be expected
when perceived risk is greater, as when
the stimulus is confused for a known
predator (Frid and Dill, 2002). In
addition, because the source of the
perceived predator (i.e., MFA sonar)
will likely be closer to the whales
(because attenuation limits the range of
detection of mid-frequencies) and
moving faster (because it will be on
faster-moving vessels), any antipredator
response would be more likely to be
severe (with greater perceived predation
risk, an animal is more likely to
disregard the cost of the response; Frid
and Dill, 2002). Indeed, when analyzing
movements of a beaked whale exposed
to playback of killer whale predation
calls, Allen et al. (2014) found that the
whale engaged in a prolonged, directed
avoidance response, suggesting a
behavioral reaction that could pose a
risk factor for stranding. Overall, these
significant differences between sound
from MFA sonar and the mid-frequency
sound component from airguns and the
likelihood that MFA sonar signals will
be interpreted in error as a predator are
critical to understanding the likely risk
of behaviorally-mediated injury due to
seismic surveys.
The available scientific literature also
provides a useful contrast between
airgun noise and MFA sonar regarding
the likely risk of behaviorally-mediated
injury. There is strong evidence for the
association of beaked whale stranding
events with MFA sonar use, and
particularly detailed accounting of
several events is available (e.g., a 2000
Bahamas stranding event for which
investigators concluded that MFA sonar
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use was responsible; Evans and
England, 2001). D’Amico et al. (2009)
reviewed 126 beaked whale mass
stranding events over the period from
1950 (i.e., from the development of
modern MFA sonar systems) through
2004. Of these, there were two events
where detailed information was
available on both the timing and
location of the stranding and the
concurrent nearby naval activity,
including verification of active MFA
sonar usage, with no evidence for an
alternative cause of stranding. An
additional ten events were at minimum
spatially and temporally coincident
with naval activity likely to have
included MFA sonar use and, despite
incomplete knowledge of timing and
location of the stranding or the naval
activity in some cases, there was no
evidence for an alternative cause of
stranding.4 Separately, the International
Council for the Exploration of the Sea
reported in 2005 that, worldwide, there
have been about 50 known strandings,
consisting mostly of beaked whales,
with a potential causal link to MFA
sonar (ICES, 2005). In contrast, very few
such associations have been made to
seismic surveys, despite widespread use
of airguns as a geophysical sound source
in numerous locations around the
world.
A more recent review of possible
stranding associations with seismic
surveys (Castellote and Llorens, 2016)
states plainly that, ‘‘[s]peculation
concerning possible links between
seismic survey noise and cetacean
strandings is available for a dozen
events but without convincing causal
evidence.’’ The authors’ ‘‘exhaustive’’
search of available information found
ten events worth further investigation
via a ranking system representing a
rough metric of the relative level of
confidence offered by the data for
inferences about the possible role of the
seismic survey in a given stranding
event. Only three of these events
involved beaked whales. Whereas
D’Amico et al. (2009) used a 1–5
ranking system, in which ‘‘1’’
represented the most robust evidence
connecting the event to MFA sonar use,
Castellote and Llorens (2016) used a 1–
6 ranking system, in which ‘‘6’’
represented the most robust evidence
4 The U.S. Navy has publicly stated its agreement
that five such events since 1996 were associated in
time and space with MFA sonar use, either by the
U.S. Navy alone or in joint training exercises with
the North Atlantic Treaty Organization. The U.S.
Navy additionally noted that, as of 2017, a 2014
beaked whale stranding event in Crete coincident
with naval exercises was under review and had not
yet been determined to be linked to sonar activities
(DoN, 2017).
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connecting the event to the seismic
survey. As described above, D’Amico et
al. (2009) found that two events were
ranked ‘‘1’’ and ten events were ranked
‘‘2’’ (i.e., 12 beaked whale stranding
events were found to be associated with
MFA sonar use). In contrast, Castellote
and Llorens (2016) found that none of
the three beaked whale stranding events
achieved their highest ranks of 5 or 6.5
However, we acknowledged in the
notice of proposed rulemaking that one
of these stranding events, involving two
Cuvier’s beaked whales, was
contemporaneous with and reasonably
associated spatially with a 2002 seismic
survey in the Gulf of California, and
here acknowledge the same for the 2007
Gulf of Cadiz seismic survey discussed
by Castellote and Llorens (also
involving two Cuvier’s beaked whales).
However, neither event was considered
a ‘‘true atypical mass stranding’’
(according to Frantzis [1998]) as used in
the analysis of Castellote and Llorens
(2016). While we agree with the authors
that this lack of evidence should not be
considered conclusive, it is clear that
there is very little evidence that seismic
surveys should be considered as posing
a significant risk of acute harm to
marine mammals.
Comment: NRDC asserts that NMFS
has failed to account adequately for the
effects of stress on marine mammals.
Response: As NRDC acknowledges,
we addressed the available literature
regarding potential impacts of stress
resulting from noise exposure in marine
mammals. As described in that
discussion, stress responses are
complicated and may or may not have
meaningful impacts on marine
mammals. NRDC implies that NMFS
must (1) enumerate takes resulting from
stress alone and (2) specifically address
stress in its negligible impact analysis.
The effects of stress are not
straightforward, and there is no
information available to inform an
understanding of whether it is
reasonably likely that an animal may
5 Of the ten total events, none achieved the
highest rank of 6. Two events were ranked as 5: One
stranding in Peru involving dolphins and porpoises
and a 2008 stranding in Madagascar. This latter
ranking can only broadly be associated with the
survey itself, as opposed to use of seismic airguns.
An exhaustive investigation of this stranding event,
which did not involve beaked whales, concluded
that use of a high-frequency mapping system (12kHz multibeam echosounder) was the most
plausible and likely initial behavioral trigger of the
event, which was likely exacerbated by several siteand situation-specific secondary factors. The review
panel found that seismic airguns were used after the
initial strandings and animals entering a lagoon
system, that airgun use clearly had no role as an
initial trigger, and that there was no evidence that
airgun use dissuaded animals from leaving
(Southall et al., 2013).
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experience a stress response upon noise
exposure that would not be accounted
for in NMFS’ existing enumeration of
takes via exposure to noise, which
includes an accounting for exposures
above received levels as low as 140 dB
rms (and as low as 120 dB rms for
beaked whales). NRDC provides nothing
informative regarding how such an
analysis might be carried out. With
regard to NMFS’ negligible impact
analysis, we believe that the potential
effects of stress are addressed and
subsumed within NMFS’ considerations
of severity of effect and vulnerability of
affected populations. Similarly, NRDC
provides no justification as to why
stress would appropriately be
considered separately in this analysis,
and no useful recommendation as to
how to do so, if appropriate. We believe
we have appropriately acknowledged
the potential effects of stress, and that
these potential effects are accounted for
within our overall assessment of
potential effects on marine mammals.
Comment: NRDC states that masking
results in take of marine mammals and
that NMFS must account for this in its
take estimates.
Response: We addressed our
consideration of masking in greater
detail in a previous response. We
acknowledge that masking may impact
marine mammals, particularly baleen
whales such as the Bryde’s whale, and
particularly when considered in the
context of the full suite of regulated and
unregulated anthropogenic sound
contributions overlaying an animal’s
acoustic habitat. We acknowledge that
masking can constitute a take,
depending on the particular
circumstances, but do not agree that
masking effects from the incremental
noise contributions of individual
activities or sound sources always rise
to the level of take. Further, not all takes
are readily quantifiable. In this case,
while masking is considered in the
analysis, we do not believe it will result
in take of marine mammals beyond
those that have already been quantified
as taken by behavioral harassment.
Specifically, in the case of these
proposed activities, in the event that
some masking incidents rise to the level
of a take, we would expect them to be
accounted for in the quantified
exposures above the harassment
thresholds. Given the short duration of
expected noise exposures, any take by
masking in the case of these surveys
would be most likely to be incurred by
individuals either exposed briefly to
notably higher levels or those that are
generally in the wider vicinity of the
source for comparatively longer times.
Both of these situations would be
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captured in the enumeration of takes by
Level B harassment, which accounts for
takes that may occur upon exposure at
relatively low levels of received sound
(e.g., 140 dB).
Comment: MMC commented that the
aversion adjustment applied to
estimates of Level A harassment
proposed by NMFS for low- and highfrequency cetaceans is not supported.
NRDC provided similar comments.
Response: NMFS disagrees with these
comments, and clarifies our position
given the misunderstanding evident in
the comments. The MMC cites NMFS’
statements that ‘‘too little is known
about the factors that lead to avoidance
of sounds to quantify aversive behavior
for survey activities when modeling
marine mammal exposure to sound’’
and that ‘‘aversion is a contextdependent behavioral response affected
by biological factors, including energetic
and reproductive state, sociality, and
health status of individual animals’’ in
characterizing our subsequent use of a
post-hoc correction factor to account for
aversion as an ‘‘apparent contradiction.’’
Similarly, NRDC cites NMFS’ statement
that aversion was not quantified in the
modeling process due to lack of
information regarding species-specific
degree of aversion and level of onset in
criticizing the adjustment that was later
made.
Aversion is a known real-world
phenomenon. It is well-known that
animals will avoid unpleasant stimuli,
such as very high received levels of
sound. A large and growing literature
has demonstrated behavioral aversion in
a number of contexts for many marine
mammal species in increasingly
controlled and well-documented
contexts. While considerable species,
individual, and context-dependencies
exist in terms of received noise levels
associated with behavioral aversion,
clear patterns of behavioral aversion
have been demonstrated empirically
within odontocetes and mysticetes (e.g.,
Miller et al., 2012, 2014; DeRuiter et al.,
2013; Southall et al., 2019b). This is
particularly true for exposure scenarios
in which animals occur relatively close
to sources and at the high levels that
would be required for even TTS (much
less PTS) to occur. In some instances, in
these and other studies, behavioral
avoidance has been measured at
received levels many orders of
magnitude below those required for
predicted PTS onset and even below the
nominal, 50 percent behavioral response
probability at 160 dB rms that NMFS
has applied historically.
However, accounting for aversion
quantitatively in an acoustic exposure
modeling process is a significantly data-
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heavy endeavor and, as we noted,
despite the growing body of evidence
there is at this time still not sufficient
data regarding the specific degree of
aversion and level of onset on a speciesspecific basis. That is, in order to
account for aversion within the
modeling process, one must program
individual animats representing
different species to respond at a specific
received level by changing their
direction of travel by a specific degree
and assuming a specific rate of speed.
Through a test scenario evaluation
(discussed in the notice of proposed
rulemaking), we determined that while
this is possible to do, the specific values
that must be used in programming the
animat response could not be
adequately derived. Instead, a nominal
offset factor was applied to the modeled
injurious exposures based on published
model result evaluation to account for
aversion.
Ellison et al. (2016) modeled
scenarios using animal movement
models to evaluate predicted PTS in
which no aversion was assumed relative
to scenarios where reasonable
assumptions were made about aversion,
in line with historical response
probability assumptions and that
existing scientific literature suggest are
appropriate. Scenarios where no
aversion probability was used
overestimated the potential for high
levels of exposure required for PTS by
about five times. Accordingly, total
modeled injurious exposures calculated
without accounting for behavioral
aversion (for low- and high-frequency
species) were multiplied by 0.2 as part
of the EWG risk analysis. NMFS
consulted the EWG in selecting the
specific offset factor, and discussed that
selection again in context of the public
comments received. The EWG—which
is composed of some of the foremost
scientists in the field of marine mammal
behavioral response study, and includes
the lead author of the Ellison et al.
(2016) study—agreed that the approach
and specific offset factor was a
reasonable and likely conservative
approach to addressing the issue of
aversion.
The commenters do not dispute that
aversion is a meaningful real-world
phenomenon that is significantly
influential on actual occurrence of Level
A harassment. As NRDC acknowledges,
‘‘it is certainly true that some marine
mammals will flee the sound.’’ Yet the
commenters would have us ignore this
phenomenon and assume unrealistically
high amounts of auditory injury for
marine mammals in the GOM. NMFS
does not agree that this would be
appropriate. As described above, there
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is extensive information supporting the
aversion concept in marine mammals,
but limited quantitative data with which
to develop precise, species-specific
offset factors. Accordingly, utilizing the
available data and expert input, NMFS
applied its professional judgement in
order to account for this meaningful
phenomenon.
Comment: NRDC disagrees with
NMFS’ conclusion that Level A
harassment is not likely to occur for
mid-frequency (MF) cetaceans and
states that this ‘‘problem [. . .] must be
addressed.’’
Response: As was explained in the
notice of proposed rulemaking, the
number of modeled incidents of Level A
harassment for MF cetacean species is
not realistic. The modeled isopleth
distance to the relevant Level A
harassment threshold, i.e., the
predominant MF peak pressure
threshold, is only 18 m. As we
explained in the notice of proposed
rulemaking, it is understandable that
even such a small assumed area could
lead to the results given when a realworld density value is sufficiently high
to lead to non-zero scaled 24-hr
modeled exposure results, which are
then multiplied by large numbers of
notional survey days. We explain in
greater detail below why relatively
small zones, i.e., zones contained within
the near-field of an airgun array, should
not be expected to result in actual
injurious exposure. NRDC also appears
to be under the impression that the
conclusion was based on what they refer
to as ‘‘shorter injurious take distances
assumed in the Gulf of Mexico modeling
than in modeling for seismic in other
regions, such as the Atlantic,’’ an
apparent misunderstanding on the part
of the commenter that they refer to as
a ‘‘discrepancy’’ that is ‘‘never
explained’’ and ‘‘appears arbitrary.’’
Given the lack of detail provided, NMFS
cannot be sure what NRDC is referring
to. However, we do know that state-ofscience propagation modeling
performed for a notional array here
provided the 18 m result described
above. For five different, real-world
arrays evaluated for use in the Atlantic
Ocean (83 FR 63268; December 7, 2018),
the calculated isopleth distance to the
230 dB peak sound pressure level (SPL)
MF Level A harassment threshold was
an average 27 m (range 14–63 m), in
keeping with the value calculated here.
For MF cetaceans, the only potential
injury zones will be based on the peak
pressure metric, as such zones will be
larger than those calculated on the basis
of the cumulative sound exposure level
(SEL) metric (which are essentially nonexistent for MF and HF cetaceans). As
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noted, the estimated zone size for the
230 dB peak threshold for MF cetaceans
is only 18 m. In a theoretical modeling
scenario, it is possible for animats to
engage with such a small assumed zone
around a notional point source and,
subsequently, for these interactions to
scale to predictions of real-world
exposures given a sufficient number of
predicted 24-hr survey days in
confluence with sufficiently high
predicted real-world animal densities—
i.e., the modeling process that resulted
in the predicted exposure estimates for
MF cetaceans in the modeling report.
However, this is not a realistic outcome.
The source level of the array is a
theoretical definition assuming a point
source and measurement in the far-field
of the source (MacGillivray, 2006). As
described by Caldwell and Dragoset
(2000), an array is not a point source,
but one that spans a small area. In the
far-field, individual elements in arrays
will effectively work as one source
because individual pressure peaks will
have coalesced into one relatively broad
pulse. The array can then be considered
a ‘‘point source.’’ For distances within
the near-field, i.e., approximately 2–3
times the array dimensions, pressure
peaks from individual elements do not
arrive simultaneously because the
observation point is not equidistant
from each element. The effect is
destructive interference of the outputs
of each element, so that peak pressures
in the near-field will be significantly
lower than the output of the largest
individual element. Here, the 230 dB
peak isopleth distances would be
expected to be within the near-field of
the arrays where the definition of source
level breaks down. Therefore, actual
locations within this distance (i.e.,
within 18 m) of the array center where
the sound level exceeds 230 dB peak
SPL would not necessarily exist. In
general, Caldwell and Dragoset (2000)
suggest that the near-field for airgun
arrays is considered to extend out to
approximately 250 m.
In order to provide quantitative
support for this theoretical argument,
we calculated expected maximum
distances at which the near-field would
transition to the far-field for five
specific, real-world arrays proposed for
use in the Atlantic Ocean (83 FR 63268).
The average distance to the near-field
calculated for the five arrays, following
the process described below, was 203 m
(range 80–417 m).
For a specific array one can estimate
the distance at which the near-field
transitions to the far-field by:
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wavelength of the signal (Lurton, 2002).
Given that l can be defined by:
where f is the frequency of the sound
signal and v is the speed of the sound
in the medium of interest, one can
rewrite the equation for D as:
and calculate D directly given a
particular frequency and known speed
of sound (here assumed to be 1,500
meters per second in water, although
this varies with environmental
conditions).
To determine the closest distance to
the array at which the modeled source
level prediction is valid (i.e., maximum
extent of the near-field), we calculated
D based on an assumed frequency of 1
kHz. A frequency of 1 kHz is commonly
used in near-field/far-field calculations
for airgun arrays (Zykov and Carr, 2014;
MacGillivray, 2006; NSF and USGS,
2011), and based on representative
airgun spectrum data and field
measurements of an airgun array used
on the R/V Marcus G. Langseth, nearly
all (greater than 95 percent) of the
energy from airgun arrays is below 1
kHz (Tolstoy et al., 2009). Thus, using
1 kHz as the upper cut-off for
calculating the maximum extent of the
near-field should reasonably represent
the near-field extent in field conditions.
If the largest distance to the peak
sound pressure level threshold was
equal to or less than the longest
dimension of the array (i.e., under the
array), or within the near-field, then
received levels that meet or exceed the
threshold in most cases are not expected
to occur. This is because within the
near-field and within the dimensions of
the array, the specified source level is
overestimated and not applicable. In
fact, until one reaches a distance of
approximately three or four times the
near-field distance, the average intensity
of sound at any given distance from the
array is still less than that based on
calculations that assume a directional
point source (Lurton, 2002). For
example, an airgun array used on the R/
V Marcus G. Langseth has an
approximate diagonal of 29 m, resulting
in a near-field distance of 140 m at 1
kHz (NSF and USGS, 2011). Field
measurements of this array indicate that
the source behaves like multiple
discrete sources, rather than a
directional point source, beginning at
approximately 400 m (deep site) to 1 km
(shallow site) from the center of the
array (Tolstoy et al., 2009), distances
that are actually greater than four times
the calculated 140-m near-field
distance. Within these distances, the
recorded received levels were always
lower than would be predicted based on
calculations that assume a directional
point source, and increasingly so as one
moves closer towards the array (Tolstoy
et al., 2009). Given this, relying on the
calculated distances as the distances at
which we expect to be in the near-field
is a conservative approach because even
beyond this distance the acoustic
modeling still overestimates the actual
received level.
Within the near-field, in order to
explicitly evaluate the likelihood of
exceeding any particular acoustic
threshold, one would need to consider
the exact position of the animal, its
relationship to individual array
elements, and how the individual
acoustic sources propagate and their
acoustic fields interact. Given that
within the near-field and dimensions of
the array source levels would be below
the modeled notional source level, we
believe exceedance of the peak pressure
threshold would only be possible under
highly unlikely circumstances.
Therefore, we expect the potential for
Level A harassment of MF cetaceans to
be de minimis, even before the likely
moderating effects of aversion and/or
other compensatory behaviors (e.g.,
Nachtigall et al., 2018) are considered.
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We do not believe that Level A
harassment is a likely outcome for any
MF cetacean.
Comment: The MMC comments that
the estimated numbers of Level B
harassment must be increased to
account for the incidents of acoustic
exposure that were modeled as injurious
but subsequently discounted due to
aversion. NRDC commented similarly.
Response: NMFS agrees that animals
that avoid Level A harassment through
aversive behavior should be considered
as having been subject to Level B
harassment and increased the Level B
harassment estimates accordingly.
However, these estimates have been
superseded by the revised estimates
submitted by BOEM in support of their
revised scope of activity.
Marine Mammal Protection Act—
General
Comment: The MMC recommended
that any ‘‘formal interpretation’’ by
NMFS of MMPA standards, such as the
least practicable adverse impact
standard and small numbers standard,
be issued in stand-alone, generally
applicable rulemakings (e.g., in
amendments to 50 CFR 216.103 or
216.105) or in a separate policy
directive, rather than in the preambles
to individual proposed rules.
Response: We appreciate the
recommendation and may consider the
recommended approaches in the future.
However, providing directly relevant
explanations of programmatic
approaches or interpretations related to
the incidental take provisions of the
MMPA in a proposed incidental take
authorization is an effective and
efficient way to provide information to
and solicit focused input from the
public. Further, this approach
ultimately affords the same
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opportunities for public comment as a
stand-alone rulemaking would.
Regarding the least practicable
adverse impact standard, NMFS has
provided similar explanations in other
recent section 101(a)(5)(A) rules. See,
e.g., 83 FR 66846 (December 27, 2018)
(U.S. Navy Training and Testing
Activities for Hawaii-Southern
California Study Area).
Least Practicable Adverse Impact
Comment: NRDC believes NMFS
relies on a ‘‘flawed interpretation’’ of
the least practicable adverse impact
standard. They state that NMFS (1)
wrongly imports a population-level
focus into the standard, contrary to the
‘‘clear’’ holding of the Ninth Circuit in
NRDC v. Pritzker, 828 F.3d 1125 (9th
Cir. 2016); and (2) inappropriately
‘‘balances’’ or weighs effectiveness
against practicability without sufficient
analysis, counter to Pritzker.
Response: NMFS carefully evaluated
the Ninth Circuit’s opinion in Pritzker
and believe we have fully addressed the
court’s concerns. NMFS’ discussion of
the least practicable adverse impact
standard in the Mitigation section
explains why we believe a population
focus is a reasonable interpretation of
the standard.
With regard to the second point,
NMFS disagrees that the analysis is
insufficient. NMFS’ interpretation of the
LPAI standard is a reasonable
interpretation that gives effect to the
language in the statute and the
underlying legislative intent. Congress
intended the agencies administering
section 101(a)(5)(A) to consider
practicability when determining
appropriate mitigation, and we do not
believe the analysis must be conducted
in a rigid sequential fashion. There is a
tension inherent in the phrase ‘‘least
practicable adverse impact’’ in that
‘‘least [. . .] adverse impact’’ pulls in
favor of one direction (i.e., expanding
mitigation) while ‘‘practicable’’ pulls in
favor of the other direction (i.e., limiting
mitigation), and weighing the relative
costs and benefits is, in NMFS’ view, a
meaningful way to address and resolve
this tension. Further, as described in the
proposed rule and augmented in this
final rule in both the Mitigation section
and the response to comments, NMFS
considered all recommended mitigation
in the context of both the reduction of
impacts on marine mammal species and
stocks and their habitat and the
practicability of such mitigation in
reaching the required set of measures
that we believe satisfy the least
practicable adverse impact standard.
Comment: The Associations assert
that NMFS failed to provide sufficient
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practicability analyses for the proposed
mitigation requirements.
Response: No guidance is provided by
the MMPA or NMFS’ implementing
regulations as to what constitutes
‘‘practicability’’ for the non-military
readiness activities considered here, or
how to ascertain whether a proposed
measure is practicable. Neither the term
‘‘practicable’’ nor the phrase ‘‘least
practicable adverse impact’’ is defined
by the MMPA or in NMFS’
implementing regulations. (See
Mitigation, later in this document, for
extensive discussion on NMFS’
interpretation of the meaning of ‘‘least
practicable adverse impact.’’) Therefore,
while the MMPA’s requirement to
prescribe mitigation achieving the ‘‘least
practicable adverse impact’’ demands
consideration of practicability, the need
for additional ‘‘analysis’’ of unspecified
scope, detail, or methodology, as
demanded by the Associations, cannot
be found in the statute, legislative
history, regulations, or case law.
However, NMFS does not start from
scratch. Our implementing regulations
at 50 CFR 216.104(a)(11) require
applications for incidental take
authorizations to include information
about the availability and feasibility
(economic and technological) of
equipment, methods, and manner of
conducting such activity or other means
of effecting the least practicable adverse
impact upon the affected species or
stocks, their habitat, and on their
availability for subsistence uses, paying
particular attention to rookeries, mating
grounds, and areas of similar
significance. This often provides the
foundation of NMFS’ proposed
mitigation, after consideration of the
objectives of those and other possible
measures and how they may achieve
those objectives as well as, when
possible, what we know about the
practicability of the proposed measures.
As a general matter, where an
applicant proposes measures that are
likely to reduce impacts to marine
mammals, the fact that they are
included in the proposal and
application indicates that the measures
are practicable, and it is not necessary
for NMFS to conduct a detailed analysis
of the measures the applicant proposed
(rather, they are simply included).
However, it is incumbent on NMFS to
consider whether there are other
practicable measures that would
contribute to the reduction of risk or
severity of adverse effects on the species
or stocks.
We then seek public comment on the
proposal and, if contradictory
information is presented by members of
the public (including prospective
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applicants), the information is
considered in making a decision
regarding whether to retain, modify, or
eliminate a proposed measure.
Our notice of proposed rulemaking
presented specific discussion of
practicability considerations, including
both the monetized direct costs of
proposed measures as well as what we
understand about potential indirect
costs, and provided detailed discussion
relating to certain measures. While
much of this analysis was conducted
under a regulatory impact analysis (RIA)
conducted pursuant to Executive Order
12866, as stated by the Associations, the
utility of the analysis is not limited to
use there. For example, while the
Associations claim that NMFS fails to
‘‘consider impacts beyond immediate
operational impacts,’’ the RIA provides
a detailed analysis of the sort of
speculative indirect costs of concern to
industry, and the RIA’s analysis is
incorporated into NMFS’ consideration
of practicability. Overall, we note that
the Associations’ comments are
peppered with reference to cost
increases, both vague (‘‘resulting in
millions of dollars of added cost’’) and
specific (‘‘increase costs an estimated
5% to 20%’’), but without sufficient
supporting data.
NMFS interprets ‘‘practicable’’ simply
as capable of being put into practice or
of being done or accomplished.
Practicability of the standard
operational protocols was reasonably
assumed in consideration of the fact that
they are included in many incidental
take authorizations and that we did not
receive any specific public comments to
the contrary. Moreover, many of these
measures were proposed by the
applicant (BOEM) in their petition for
regulations, including ramp-up and
shutdown requirements and a
requirement to observe a time-area
restriction in coastal waters to protect
bottlenose dolphins during the time of
their reproductive activity peak. The
Associations claim that our proposal
applies these standard measures in such
a way as to extend their ‘‘geographic
and temporal scope or to circumstances
where they are unnecessary or
impossible to implement,’’ but provide
no specific information as to what
measures they specifically refer to, in
what circumstances they believe
specific measures are unnecessary, or in
what circumstances specific measures
are impossible to implement. The
Associations assert that NMFS’
considerations of practicability ‘‘fail to
adequately estimate levels of current
and future geophysical work or consider
costs and impacts beyond the
immediate survey work,’’ but their
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comments provide no specific
information to enable NMFS to assess
its consideration of practicability.
NMFS’ consideration of practicability
was sufficient and in accordance with
law, and the Associations provided no
specific contradictory information for
NMFS’ evaluation.
Comment: The MMC recommended
that NMFS rework its evaluation criteria
for applying the least practicable
adverse impact standard to separate the
factors used to determine whether a
potential impact on marine mammal
species or stocks or their habitat is
adverse and whether possible mitigation
measures would be effective. In this
regard, the MMC asserted that it seems
as though the proposed ‘‘effectiveness’’
criterion more appropriately fits as an
element of practicability and should be
addressed under that prong of the
analysis. In other words, a measure not
expected to be effective should not be
considered a practicable means of
reducing impacts.
Response: In the Mitigation section,
NMFS has explained in detail its
interpretation of the least practicable
adverse impact standard, the rationale
for the interpretation, and our approach
for implementing the interpretation. The
ability of a measure to reduce effects on
marine mammals is entirely related to
its ‘‘effectiveness’’ as a measure,
whereas the effectiveness of a measure
is not connected to its practicability.
The MMC did not support its argument
with scientific information, and NMFS
has not implemented the suggestion.
Comment: The MMC recommended
that NMFS address the habitat
component of the least practicable
adverse impact provision in greater
detail. It asserted that NMFS’ discussion
of critical habitat, marine sanctuaries,
and biologically important areas (BIA)
in the proposed rule is not integrated
with the discussion of the least
practicable adverse impact standard. As
stated by the MMC, it would seem that,
under the least practicable adverse
impact provision, adverse impacts on
important habitat should be avoided
whenever practicable. Therefore, to the
extent that activities would be allowed
to proceed in these areas, NMFS should
explain why it is not practicable to
constrain them further. The MMC also
suggests that NMFS intends to defer
consideration of measures to protect
habitat to individual LOAs, rather than
addressing such measures in the
regulations, as the MMC contends is
required.
Response: Marine mammal habitat
value is informed by marine mammal
presence and use and, in some cases,
there may be overlap in mitigation
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measures for the species or stock
directly and for use of habitat. In this
rule, NMFS has identified one time-area
restriction (carried forward from the
proposed rule) based on a combination
of factors that include higher densities
and observations of specific important
behaviors of marine mammals
themselves, but also that clearly reflect
preferred habitat. In addition to being
delineated based on physical features
that drive habitat function (e.g.,
bathymetric features, among others for
some BIAs), the high densities and
concentration of certain important
behaviors (e.g., feeding) in these
particular areas indicate the presence of
preferred habitat. The MMC seems to
suggest that NMFS must always
consider separate measures aimed at
marine mammal habitat. However, the
MMPA does not specify that effects to
habitat must be mitigated in separate
measures, and NMFS has identified
measures that provide significant
reduction of impacts to both ‘‘marine
mammal species and stocks and their
habitat,’’ as required by the statute.
Finally, we clarify here that all
measures to reduce impacts to both
marine mammal species and stocks and
their habitat are included in the
regulations and then implemented
through activity-specific LOAs.
Negligible Impact
Comment: The Associations and
Chevron concur with NMFS’ finding
that the incidental taking that may be
authorized under the ITR will have a
negligible impact on the affected marine
mammal stocks. The Associations
additionally specify their agreement
with NMFS’ conclusions that Level A
harassment will not play a meaningful
role in the overall degree of impact
experienced by marine mammal
populations as a result of the projected
survey activity and that mid-frequency
cetaceans are unlikely to incur Level A
harassment, as well as with NMFS’ use
of the Wood et al. (2012) probabilistic
risk function.
Response: NMFS appreciates the
comments.
Comment: NRDC claims that NMFS
did not define the total amount of take
it evaluated in making the negligible
impact determination and asserts that
the proposed rule is unclear about the
data and calculations that informed the
basis of the negligible impact finding.
Response: NMFS disagrees with these
comments. NMFS explicitly defined the
basis, as well as the process, for the
negligible impact analysis. Although the
negligible impact analysis was built
upon relatively sophisticated acoustic
exposure modeling, and incorporated
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advances in the science of risk
assessment, the informational inputs to
the analysis and the analytical
framework were clearly elucidated and
the supporting documentation
identified and provided as companion
documents to the public for review in
association with our negligible impact
analysis. The notice of proposed
rulemaking identified a point of contact
available to provide further information
or answer questions if necessary.
NMFS stated that the ‘‘specified
activity’’ for the proposed regulations is
a broad program of geophysical survey
activity that could occur at any time of
year in U.S. waters of the GOM. This
conceptual program, as defined by
BOEM through projected levels of
survey effort, was described and shown
in Table 1 of the notice of proposed
rulemaking. These annual survey
projections aligned generally with
‘‘low,’’ ‘‘moderate,’’ and ‘‘high’’ effort
years (83 FR 29224). These projected
levels of survey effort informed the
acoustic modeling report (Zeddies et al.
2015, 2017a), which was extensively
and clearly summarized in the notice of
proposed rulemaking, while the report
itself was made available for public
review concurrently with the notice of
proposed rulemaking. In order to
reasonably estimate the actual effort that
might occur over the five-year
timeframe of the proposed ITR, NMFS
determined for the proposed rule
analysis that it would be appropriate to
assume that one high-effort year, two
moderate-effort years, and two loweffort years (and, therefore, associated
acoustic exposure estimates) would
occur. NMFS then selected and
identified the specific effort scenarios
that formed the basis for the analysis in
association with Table 9 of the notice of
proposed rulemaking, titled ‘‘ScenarioSpecific Expected Take Numbers and
Mean Annual Take Level.’’ Table 9 of
the notice identified the annual and
total amounts of take that NMFS
expected to occur under the ITR. The
preliminary negligible impact analysis
then referred back to Table 9 as the basis
for the analytical process and discussion
provided therein (See 83 FR 29290–
29291).
NRDC complains that ‘‘NMFS never
defines the total amount of take it
proposes to authorize.’’ However, as is
typical for a programmatic analysis, the
ITR and its associated analysis
(including negligible impact) do not
propose to authorize take per se, but
rather to provide a description of the
upper bound within which take may be
authorized via LOAs. The upper bounds
of the instances of take that may be
authorized under this rule are indicated
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in Table 9 in this final rule. The actual
amount of take authorized through
LOAs under the ITR will be determined
by applicant interest (subject to the
upper bound).
NMFS also identified the Expert
Working Group (EWG) report (Southall
et al., 2017) as an essential companion
to the notice of proposed rulemaking
and, similar to the acoustic modeling
report, provided the document for
concurrent public review. The EWG
report describes the systematic risk
assessment framework that, in part,
forms the basis for the negligible impact
analysis. We concisely described the
analytical framework in the notice and
provided the results of that analysis.
Ultimately, the EWG report provides
overall evaluated relative risk for each
of the three effort scenarios (low,
moderate, high) for each species in each
of seven different zones. As stated in the
notice, the severity and vulnerability
ratings (facets of the analytical
framework that are also clearly
explained both in the EWG report and
the notice) are integrated to provide
relative impact ratings of overall risk.
These zone-specific relative impact
ratings for each species were then
integrated using basic calculations to
produce species-specific, GOM-wide
overall evaluated relative risk ratings for
each of the three effort scenarios.
Overall vulnerability scores for each
species were produced by summing the
zone-specific vulnerability scores, as
scaled to the zone-specific population.
For example, the Zone 1 vulnerability
score is multiplied by the ratio of the
Zone 1 population to the total
population. These zone-specific
products are then summed. Overall
severity scoring is calculated as the
proportion of the sum of scenariospecific takes to the total population.
These two factors are then integrated as
described in the EWG report.
NRDC also states that the ‘‘actual
percentages of populations affected by
takes’’ are not provided. NMFS
disagrees, as this information can be
replicated using information that was
provided to the public via the acoustic
modeling report. Additional underlying
data are necessary to replicate zonespecific findings. Excel workbooks
containing these data were made
publicly available by BOEM during
review of their PEIS. NMFS did not
view these additional data as essential
to understanding the modeling report or
the proposed ITR and did not publish
these data on its website. Members of
the public interested in further
exploration of the information provided
in the modeling report, or in need of
assistance regarding their independent
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analysis of the modeling report, could
have contacted the NMFS point of
contact identified in the notice of
proposed rulemaking.
In sum, NMFS provided sufficient
information in support of its negligible
impact analysis affording the public
meaningful opportunity to comment.
Further, consistent with a potential
alternative scope identified in the
proposed rule that would remove the
Eastern Planning Area (EPA), the scope
of this final rule has been modified to
remove the GOMESA area, which
includes most of the EPA (and a small
portion of the Central Planning Area),
based on BOEM’s update to its action.
This has resulted in a reduction in the
upper bounds of the instances of take
that may be authorized for all species
pursuant to this final rule (see Tables 8
and 9).
Comment: The MMC commented
similarly to NRDC, expressing some
concern regarding the risk assessment
framework and asserting ‘‘apparent
inconsistencies,’’ while recommending
that NMFS (1) provide the final risk
assessment framework, underlying
results, and its interpretation of those
results to the public and (2) allow for an
additional 30-day comment period to
review the findings sufficiently in
advance of issuing the final rule.
Response: NMFS disagrees with the
MMC comments. They state that the
EWG report and analysis ‘‘has some
apparent inconsistencies’’ as compared
against the preamble to the proposed
rule because the scenario-specific high,
moderate, and low values presented in
Table 3 of the EWG report do not align
with the summary minimum,
maximum, and mean values given in
Table 2 of the notice of proposed
rulemaking. We note that the MMC
provided clarifying questions to NMFS
during the public comment period in
advance of submitting a formal
comment letter and expressed some
confusion regarding Table 2 of that
notice at that time. As was explained to
the MMC then, Table 2 of the preamble
was provided for illustrative purposes
only, as a way of providing a more
concise look at the information given in
Table 1 of the preamble. As was
explained, the values given in Table 2
were not consequential with regard to
anything that followed in the preamble.
NMFS regrets any confusion caused by
inclusion of Table 2 in the notice of
proposed rulemaking but explained
clearly to the MMC that the table was
not related to the analysis. It has been
removed from this final rule.
Separately, the MMC states that
‘‘neither NMFS nor BOEM stipulated
why only certain years were selected for
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analysis,’’ claiming that NMFS
indicated that years 1, 4, and 9 were
used in the analysis ‘‘upon further
inquiry.’’ This is incorrect. In the notice
of proposed rulemaking, we stated that
‘‘Year 1 provides an example of what
might be a high-effort year in the GOM,
while Year 9 is representative of a loweffort year. A moderate level of effort in
the GOM, according to these
projections, would be similar to the
level of effort projected for Year 4.’’ (83
FR 29224.) NMFS provided explanation
of its choices in the notice of proposed
rulemaking (see, e.g., 83 FR 29261–
29262, 29290).
This portion of the MMC’s
recommendation regarding
representative years is no longer
relevant to this final rule. As discussed
previously, BOEM revised the scope of
the activity and provided revised effort
projections and resulting take estimates
accordingly. The revised take estimates
provided by BOEM reflect years 1–5 of
their original level of effort projections
and, therefore, the question of rationale
behind the selection of years 1, 4, and
9 is no longer relevant.
Regarding the notice of proposed
rulemaking, the MMC also states that
supposed discrepancies between zonespecific risk ratings and risk derived per
year across the GOM are
‘‘inconsistencies.’’ Zone-specific risk
ratings for any given effort scenario are
driven by the actual effort within that
zone for that scenario, while the overall
level of effort GOM-wide underlies the
labeling of scenarios as ‘‘high,’’
‘‘moderate,’’ and ‘‘low.’’ For example,
although year 1 was designated as the
‘‘high’’ effort scenario and year 4 the
‘‘moderate’’ effort scenario on the basis
of the total projected GOM-wide survey
days (2,286 and 1,902, respectively), the
‘‘high’’ effort scenario actually includes
significantly less projected effort in
zones 2 and 4 than does the ‘‘moderate’’
effort scenario. Therefore, risk ratings
for certain species were higher in those
specific zones for the ‘‘moderate’’ effort
scenario than they were for the ‘‘high’’
effort scenario. This was explained in
our notice of proposed rulemaking:
‘‘[P]er-zone ranges can provide a
different outlook than does an
assessment of total year projected effort
across zones. For example, in the ‘‘high’’
effort annual scenario (Year 1;
considering total projected survey days
across zones), there are 263 projected
survey days in Zone 2, while the
‘‘moderate’’ effort annual scenario (Year
4) projects 446 survey days in Zone 2.’’
This was explained directly to the MMC
upon its informal inquiry during the
public comment period. The MMC also
stated to NMFS at that time that ‘‘the
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relative risk scores for certain species
[. . .] do not make sense, presumably
because they are based on the incorrect
number of estimated survey days,’’
giving as an example that ‘‘roughtoothed dolphins in Zone 5 have an
overall Moderate risk in the High and
Low scenario years, but a Low risk in
the Moderate scenario year.’’ We
reiterated to the MMC at that time that
what the MMC viewed as illogical and
erroneous did not in fact reflect errors,
but rather the confluence of zonespecific activity levels and species
presence for a given year. The effort
scenarios used as the basis for the
analysis were clearly identified, and
there were no inconsistencies in terms
of risk ratings in consideration of the
zone-specific information underlying
those ratings (which was explained in
the notice of proposed rulemaking).
Separately, the MMC stated its view
that ‘‘the basis for determining the
relative risk thresholds, relative rating
thresholds, species-specific biological
risk factors, and environmental risk
factors was not provided’’ and that
‘‘many of the quantitative aspects have
not been substantiated.’’ While NMFS
disagrees with this statement and refers
the reader to the EWG report (Southall
et al., 2017), we also point out that, in
the absence of precise quantitative
information on these aspects of the risk
assessment framework (on a speciesand zone-specific basis), the application
of the framework necessarily requires
the application of professional
judgment. As NMFS acknowledged,
‘‘[e]lements of this approach are
subjective and relative within the
context of this program of projected
actions and, overall, the analysis
necessarily requires the application of
professional judgment.’’ (83 FR 29290.)
The MMC comments do not find fault
with any specific element or attribute of
the framework or with any specific
value chosen to represent a particular
risk threshold or a particular species’
vulnerability. NMFS does not agree that
the MMC’s recommendation to allow for
an additional 30-day comment period
for the public to review the risk
assessment framework findings in
advance of issuing the final rule is
warranted and has not implemented the
suggestion.
Comment: NRDC asserts that NMFS
has erroneously used the relativistic
assessment presented in the EWG report
as the basis for the negligible impact
determination, incorrectly applying it as
though it evaluated absolute risk. A
private citizen offers similar comments.
Response: NMFS disagrees with the
comment. The EWG analysis is an
important component of the negligible
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impact analysis, but is not the sole basis
for our determination. While the EWG
analysis comprehensively considered
the spatial and temporal overlay of the
activities and the marine mammals in
the GOM, as well as the number of takes
predicted by the described modeling,
there are details about the nature of any
‘‘take’’ anticipated to result from these
activities that were not considered
directly in the EWG analysis and which
warrant explicit consideration in the
negligible impact analysis. Accordingly,
NMFS’ analysis considers the results of
the EWG analysis, the effects of the
required mitigation, and the nature and
context of the takes that are predicted to
occur. NMFS’ analysis also explicitly
considers the effects of predicted Level
A harassment and impacts to marine
mammal habitat, which were,
respectively, not integrated into or
included in the EWG risk ratings. These
components of the full analysis, along
with any germane species or stockspecific information, are integrated and
summarized for each species or stock in
the Species and Stock-specific
Negligible Impact Analysis Summaries
section of the negligible impact analysis.
In addition, while the EWG
framework comprehensively considers
the aggregate impacts to marine
mammal populations from the activities
addressed in this rule in the context of
both the severity of the impacts and the
vulnerability of the affected species, it
does not fully consider the absence of
survey activity in the eastern GOM
(within the GOMESA moratorium area),
following BOEM’s update to the scope
of activity. While this is to some degree
reflected in the updated take estimates,
and thereby incorporated into the EWG
framework’s risk ratings, the absence of
survey activities within areas of
increased biological importance for
certain species benefits those species
GOM-wide beyond what is simply
reflected in the updated take numbers.
The negligible impact analysis considers
the reduction of both acute and chronic
effects afforded through the revised
scope of the rule.
Also, we note that while the EWG
framework produces relativistic risk
ratings, its components consist of
absolute concepts, some of which are
also absolutely quantified (e.g., whether
the specified activity area contains
greater than 30 percent of total regionwide estimated population, between 30
and 15 percent, between 15 and 5
percent, or less than 5 percent). Further,
NMFS provided substantive input into
the scoring used in implementing the
EWG framework for the GOM, to ensure
that the categories associated with
different scores, the scores themselves,
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and the weight of the scores within the
overall risk rating all reflected
meaningful biological, activity, or
environmental distinctions that would
appropriately inform the negligible
impact analysis. Accordingly, and as
intended, we used our understanding of
the framework and best professional
judgment to interpret the relativistic
results of the EWG analysis
appropriately into the larger negligible
impact analysis, with the other factors
discussed above, to make the necessary
findings specific to the effects of the
total taking on the affected species and
stocks.
Comment: NRDC asserts that the
vulnerability ratings used in the EWG
framework fail to account for several
factors appropriately, which undermine
the framework’s ability to contribute
accurately to the overall evaluation of
relative risk. NRDC cites the following
as problematic factors: Application of
vulnerability ratings on a zone-by-zone
basis, which they state negatively biases
the habitat use and temporal overlap
factors; unaccountably low ratings for
non-seismic stressors (specifically citing
the DWH oil spill); relatedly, failure to
account appropriately for all other
stressors; and failure to fully account for
stock structure and status.
Response: NMFS first notes that the
application of the EWG framework, and
specifically the development of
appropriate vulnerability ratings,
necessarily involves the use of
professional judgment, here on the part
of a group of experts in the fields of
marine mammal biology, ocean
acoustics, and the effects of noise on
marine mammals, among other things
(and in consultation with NMFS and
BOEM). Reasonable people may
disagree about the specific numerical
values assigned to any one of the 11
different factors contributing to the
overall species-specific vulnerability
score generated for each of the seven
zones (with seven factors that are static
GOM-wide and four that vary spatially,
scoring for 18 taxa and seven zones
means that 630 individual numerical
value selections underlie the
vulnerability scores); but this does not
imply that any of the specific values
selected are unreasonable. All relevant
factors were considered in generating
the species- and zone-specific
vulnerability scores.
NRDC misapprehends one of the
fundamental values of the analytical
framework, in that it is structured in a
spatially explicit way that can be
applied at multiple scales, based on the
scope of the action and the information
available to inform an assessment of the
risk associated with the activity (or suite
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of activities). This allows one to
generate overall risk ratings while also
evaluating risk on finer scales. In this
case, severity ratings were generated on
the basis of seven different GOM zones,
allowing an understanding not only of
the relative scenario-specific risk across
the entire GOM, as is demanded for this
analysis, but also to better understand
the particular zones where risk may be
high (depending on actual future survey
effort) and what part of the stock’s range
may be subject to relatively high risk.
The framework recognizes,
fundamentally, that the spatial,
temporal, and spectral overlaps between
noise-generating activities and animal
distribution are the primary factors that
drive the type, magnitude, and overall
evaluated risk of potential noise effects
on marine mammals. These
considerations are inherent and
fundamental in both the severity and
vulnerability ratings and are
deliberately integrated into both the
vulnerability and severity assessments;
in fact, key features of the analytical
framework include explicit recognition
of the importance of species distribution
relative to activity spatial distribution
and temporal and contextual differences
in exposure scenarios. If the spatially
explicit nature of the framework were
removed, as it seems NRDC is
suggesting, there would be no value in
generating a ‘‘habitat use’’ factor (i.e.,
the spatial scale would be the GOM, and
it would necessarily contain 100 percent
of the estimated population). Spatial
overlap is a central consideration for the
extent of physical overlap between
species and other environmental
stressors, with consideration of species
distribution across all zones, as well as
the extent of population concentration
and habitat specialization (as expressed
through zone-specific vulnerability
assessment). Regarding the temporal
overlap factor referenced by NRDC,
overall activity duration is a limited
consideration within the vulnerability
assessment rating but is expressed as a
central consideration within magnitudeduration functions used to evaluate
severity.
Despite the explanations provided in
the EWG report, NRDC characterizes
certain aspects of the vulnerability
scoring as ‘‘unaccountably low.’’
However, NRDC does not provide
specific recommendations for revisions
to the assigned numerical values, or
justification for their contention that
scoring is too low. All relevant stressors
were accounted for in the vulnerability
scoring and specific scores were
reasonably made on the basis of expert
professional judgment. Contrary to
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NRDC’s assertion, the effects of the
DWH oil spill were considered in the
vulnerability scoring (as well as in our
development of mitigation in
consideration of the MMPA’s least
practicable adverse impact standard).
Overall, NRDC seems to provide a
blanket suggestion, without adequate
justification or evidence, that for all
species, impacts should be considered
to be higher than we have determined.
We believe that we have satisfied the
statutory standards after careful
consideration of the available science.
Regarding stock structure, NRDC
criticizes the treatment of bottlenose
dolphins in the vulnerability scoring.
Overall, species-level take and
abundance estimates are used to support
findings for bottlenose dolphins out of
necessity. The best available
information (Roberts et al., 2016) was
used to inform combined species values
and did not support further quantitative
apportionment of estimated take or
abundances to stocks. However, NRDC’s
specific criticism of the ‘‘population’’
vulnerability scoring for bottlenose
dolphins is unwarranted. The
population score comprises three
components: Status, i.e., is the stock
listed under the ESA and/or designated
as depleted under the MMPA; trend, i.e.,
does information over the available time
series of abundance estimates indicate a
trend; and size, i.e., is the population
defined as small (less than 2,500). None
of the five designated stocks of
bottlenose dolphin in Federal waters of
the GOM are listed under the ESA or
designated as depleted under the
MMPA, and none would be classed as
small. Regarding trend, multiple SAR
abundance estimates are available for
three of the five stocks (oceanic stock
and northern and western coastal
stocks); and available information does
show an increasing trend for these
stocks. We recognize that the effects of
the DWH oil spill included likely
population reductions for all GOM
marine mammal stocks (other than the
eastern coastal stock of bottlenose
dolphins, which was not impacted by
the spill); however, the best available
information indicates that these
reductions were likely modest for all
bottlenose dolphin stocks other than the
northern coastal stock (Table 5), and no
more recent population abundance
estimates that might reflect any
potential reduction are yet available.
While the likely decline in population
abundance for northern coastal
bottlenose dolphins is subsumed within
the population score assigned for
bottlenose dolphins at the species level,
vulnerability scoring is necessarily
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performed at the species level such that
it may appropriately be integrated with
the take-based severity scoring and used
to generate an overall risk rating. As
mentioned above, the best available
scientific information does not allow for
stock-specific parsing of take for
bottlenose dolphins. Moreover, the
trend component of the population
score is a relatively small contribution
to the overall vulnerability scoring,
accounting for a maximum of two out of
30 potential points. The likely decline
in population abundance for northern
coastal bottlenose dolphins, although
not reflected in the existing
vulnerability scoring, is insignificant as
a contribution to the overall
vulnerability score for bottlenose
dolphins as a species. As noted above,
the effects of the DWH oil spill are
separately accounted for in the
vulnerability scoring. Importantly, and
also not accounted for in the EWG
framework, we include significant
mitigation (time-area restriction)
intended to alleviate impacts to
northern coastal bottlenose dolphins
during periods of greatest importance
for their reproductive behavior.
Comment: NRDC states that NMFS’
use of daily exposure durations ‘‘to
justify its negligible impact
determination’’ is arbitrary and
capricious. They state that we
incorrectly used exposure times above
the 160-dB threshold (rather than the
lower threshold associated with the
multi-step probabilistic risk function);
assumed low severity for certain
exposure durations; and disregarded
repeated exposures. A private citizen
offers similar comments.
Response: As an initial matter, while
it is true that NMFS evaluated exposure
durations for the negligible impact
analysis, it is not the only factor that we
considered ‘‘to justify’’ the
determination, as described fully in the
Negligible Impact Analysis and
Determinations section. Moreover, the
consideration of exposure duration is
entirely appropriate in assessing the
severity of a likely exposure, which is
critical to understanding how the
authorized takes are likely to impact
individual marine mammals. This was
not addressed in the EWG assessment
but was incorporated into the negligible
impact analysis.
NMFS appreciates NRDC’s comments
regarding use of exposure times above
the 160-dB threshold, and we have reevaluated the exposure duration
information and better integrated
discussion of this information into the
negligible impact analysis (see
Negligible Impact Analysis and
Determinations and Table 16 for more
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information). However, it is incorrect
that ‘‘NMFS’ time-exposure analysis is
predicated on its use of 160 dB as the
operative threshold of harm’’ and that
our use of exposure information above
the 160-dB threshold is a ‘‘back-door
return’’ of the ‘‘outdated 160 dB
threshold.’’ Inherent in the concept of a
multi-step probabilistic risk function is
the assumption that varying proportions
of an exposed population will be
harassed upon exposure at the different
steps of the function. We presented the
160-dB exposure durations in the notice
of proposed rulemaking because
exposure above this step represents the
50 percent midpoint of the function (for
all species other than beaked whales)
and, therefore, was deemed an
appropriate representation of durations
where a significant proportion of
exposed animals would be expected to
experience harassment (versus 10
percent of the population exposed to
received sound levels between 140 and
160 dB). In Table 16 of this final rule,
we present these durations for both the
160-dB and 140-dB steps of the
function. It is important to keep in mind
that, of the animals exposed above the
160-dB threshold for the indicated
species-specific durations, not all are
considered harassed. The risk function
assumes 50 percent of animals exposed
between 160-dB and 180-dB will be
harassed. For the longer exposure
durations associated with the 140-dB
threshold, only 10 percent are expected
to be harassed.
As we indicate in the Negligible
Impact Analysis and Determinations
discussion of this final rule, to put the
predicted amount of take into
meaningful context, it is useful to
understand the duration of exposure at
or above a given level of received sound
(as well as the likely number of repeated
exposures across days). While a
momentary exposure above the criteria
for Level B harassment counts as an
instance of take, that accounting does
not make any distinction between
fleeting exposures and more severe
encounters in which an animal may be
exposed to that received level of sound
for a longer period of time. This
information is meaningful to an
understanding of the likely severity of
the exposure, which is relevant to the
negligible impact evaluation. For
example, for bottlenose dolphin
exposed to noise from 3D WAZ surveys
in Zone 6, the modeling report shows
that approximately 72 takes (Level B
harassment) would be expected to occur
in a 24-hr period. However, each animat
modeled has a record or time history of
received levels of sound over the course
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of the modeled 24-hr period. The 50th
percentile of the cumulative distribution
function indicates that the time spent
exposed to levels of sound above 160 dB
rms SPL (i.e., the 50 percent midpoint
for Level B harassment) would be only
1.8 minutes—a minimal amount of
exposure carrying little potential for
significant disruption of behavioral
activity.
The Species and Stock-specific
Negligible Impact Analysis Summaries
discussion considers the relative impact
ratings in conjunction with required
mitigation and other relevant contextual
information—including exposure
durations at the various thresholds—to
produce an assessment of impact to the
stock or species, i.e., the negligible
impact determinations. For beaked
whales, take is estimated on the basis of
a risk function shifted down such that
90 percent of the animals exposed to
received levels above 140 dB and 50
percent exposed to received levels
above 120 dB are expected to be
harassed. We used this approach based
on the documented behavioral
sensitivity of beaked whales. However,
as NRDC acknowledges, context is
important when assessing behavioral
responses to sound. The exposures
above 120 dB here occur at significant
distance from the source (i.e., greater
than 50 km). It is generally accepted that
an animal’s distance from the sound
source plays an important role in the
animal’s behavioral response to a
received sound level (e.g., Gomez et al.,
2016). NMFS believes that exposures to
the relevant harassment thresholds at
significant modeled distances from the
actual sound source, although included
in the take estimates based on the risk
function, will not carry significant
consequences for the potentially
exposed animals. Rather, these
exposures are likely to result in
significantly less severe responses (if
any). Examples provided by NRDC
purporting to demonstrate greater
severity of response than we have
assumed include irrelevant examples—
beaked whales are known to respond
with greater severity to mid-frequency
active military sonar than to other
sources, as discussed in greater detail in
a previous comment response—and
examples of ‘‘responses’’ entailing
changes to vocalization patterns over
longer durations, but these responses do
not necessarily rise to the level of a take,
much less a take event of significant
severity.
Regarding repeated exposures, despite
the figures cited by NRDC concerning
potential days of activity, it is unlikely
that any given individual animal would
in fact experience repeated take events
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of the magnitude suggested. Each of the
seven GOM zones is an extremely large
area (average zone size approximately
100,000 km2), and the likely harassment
‘‘footprint’’ of any given survey would
be relatively small. Modeled isopleth
distances to the 160-dB threshold are
approximately 12 km for low-frequency
cetaceans (i.e., the Bryde’s whale), 7 km
for mid-frequency cetaceans (i.e., sperm
whales, beaked whales, dolphins), and 6
km for high-frequency cetaceans (i.e.,
Kogia spp.). Distances to the 140-dB
isopleths are substantially larger, but we
again emphasize that only ten percent of
the animals exposed at that level would
be expected to incur harassment, while
50 percent of the animals exposed at the
160-dB level would be expected to incur
harassment. It is clear that, in reality,
there is a relatively low chance of any
given individual marine mammal being
repeatedly taken within relatively short
timeframes, much less that such events
would result in fitness consequences for
those individuals. Additionally, NRDC
suggests that NMFS fails to consider
repeated takes at all, when in fact this
likelihood is inherently addressed
through the severity rating of the EWG
assessment.
NRDC concludes their comment by
claiming that NMFS failed to undertake
sufficient analysis in support of the
negligible impact determinations. We
disagree with this assertion, and refer to
the Negligible Impact Analysis and
Determinations section in support of
this final rule. NRDC focuses in
particular on sperm whales, implying
that they are likely to incur impacts to
reproductive fitness and stating that
NMFS cannot make a negligible impact
finding for sperm whales without
additional mitigation requirements.
NMFS agrees that the bioenergetics
simulations of Farmer et al. (2018a)—
cited by NRDC in support of their
argument—show that frequent
disruptions in foraging can have
potentially severe fitness consequences
for individual sperm whales. However,
a follow-up study (Farmer et al., 2018b),
which additionally accounted for the
population-level effects of the DWH oil
spill on GOM sperm whales, modeled
the potential population level
consequences of the specific
disturbance events underlying this
analysis (i.e., the acoustic exposure
modeling of Zeddies et al., 2015, 2017a).
This follow-up study found that, under
realistic modeled scenarios, no sperm
whales were projected to reach terminal
starvation and no fetal abortions were
predicted as a result of long-term
disturbance effects (i.e., over ten years
of projected survey activity). Similarly,
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predicted declines in relative body
condition (expressed as the percentage
of available reserves for a disturbed
individual whale relative to an
undisturbed whale with identical
characteristics) as a result of long-term
disturbance effects were not significant
under realistic modeled scenarios.
When evaluating the additional effects
of modeled disturbance on the DWH oil
spill-impacted trajectory, the modeling
did not predict any significant
additional stock declines (Farmer et al.,
2018b). We believe the administrative
record for this final rule amply
demonstrates that NMFS used the best
available science during our
administrative process to inform our
analyses and satisfy the standards under
section 101(a)(5)(A). Of note, and as
indicated in Changes from the Proposed
Rule, as a result of BOEM’s updated
scope of the activities and the associated
revisions to the levels of effort, both the
maximum allowable amount of take and
the maximum annual take under the
rule have decreased (significantly in
some cases, including for Bryde’s
whales and sperm whales) for all except
two species/stocks. For the two
exceptions these figures increased only
slightly, and the severity of many of the
impacts has been lessened via the
removal and/or reduction of take in
areas of greater biological importance
previously considered as mitigation
areas.
Comment: Chevron comments that
NMFS should make the final version of
the EWG report available to the public
for review and suggests expanding the
description of the inputs of the analysis.
Chevron states that the ‘‘vulnerability’’
assessment, in particular, would benefit
from additional discussion to explain
how professional judgments led to
specific rankings for each species.
Chevron also comments that NMFS
should provide an additional plain
language discussion of the risk analysis
process, including background on the
development of the risk analysis
framework, including any relevant
analogues in other ecosystems or
regulatory contexts, the ways in which
species may be considered
‘‘vulnerable,’’ and the meaning of the
‘‘risk’’ discussed.
Response: NMFS appreciates the
comment. The final report is available to
the public online at:
www.fisheries.noaa.gov/action/
incidental-take-authorization-oil-andgas-industry-geophysical-surveyactivity-gulf-mexico. The content of the
final report was determined by NMFS
and BOEM in conjunction with the
EWG. We believe that we have provided
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sufficient plain language discussion of
the EWG framework.
Comment: NRDC claims that NMFS’
negligible impact analysis is
inappropriately reliant upon the
prescribed mitigation and, further, that
the mitigation will be ineffective.
Response: First, NMFS did not rely
solely on the mitigation in order to
reach its findings under the negligible
impact standard. As is stated in the
analysis, consideration of the
implementation of prescribed mitigation
is one factor in the analysis but is not
determinative in any case. In certain
circumstances, mitigation is more
important in reaching the negligible
impact determination, e.g., when
mitigation helps to alleviate the likely
significance of taking by avoiding or
reducing impacts in important areas.
Second, while NRDC dismisses the
importance of the prescribed mitigation
by stating (mistakenly) that it is
‘‘unsupported by evidence,’’ NRDC
offers no support for their conclusions.
NRDC misunderstands the degree to
which NMFS relies on shutdowns for
sensitive or vulnerable species,
including beaked whales, at extended
distances. We agree that these measures
in and of themselves will have limited
benefit for cryptic species such as
beaked whales that are unlikely to be
observed. However, we believe that it
makes sense to minimize the duration
and intensity of disturbance for these
species when they are observed, and
because they are practicable we include
them in the suite of prescribed measures
and discuss them where appropriate.
For more readily detected species, such
as the sperm whale, which is easily
detected when at the surface and which
vocalizes frequently while underwater,
the extended distance shutdowns (for
both visual and acoustic detections)
should appropriately be considered
influential in our assessment of impacts
to affected individuals and, therefore,
ultimately on the stock. Despite NRDC’s
dismissal of these requirements, we
presume they would agree that the
duration and intensity of disturbance of
sensitive species should be minimized
where practicable.
In summary, we consider these
measures appropriately as mitigating
factors when considering context as part
of our negligible impact analysis.
Comment: The Associations state that
the Expert Working Group framework
was applied without following all of the
recommended steps, such as conducting
expert elicitation to derive risk
functions for species that do not have
parameterized Population Consequences
of Disturbance (PCOD) models. The
Associations recommend that NMFS
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seek input and advice on the framework
and its conclusions from independent
experts.
Response: There is extensive
scientific interest in forecasting how
short-term behavioral responses by
individual animals may aggregate and
result in population-level consequences.
The concept was introduced by the
National Research Council (2005) as
Population Consequences of Acoustic
Disturbance. However, given the lack of
data on acoustic responses, research
studies have generalized the issue to
look at environmental and
anthropogenic stressors in general and
renamed the concept Population
Consequences of Disturbance. New et al.
(2014) presented a modified conceptual
framework to help forecast long-term
impacts. Conceptually, a series of
transfer functions connect increasingly
broader impacts from the initial
disturbance to effects on individual
health, individual vital rates, and finally
population dynamics. The concept has
been demonstrated with a few species
for which there are extensive data from
tagged or photo-identified animals so
that effects on individuals can be
quantified. Northern elephant seals
were the first study species for which
the data from time-depth recorders were
able to be linked to an individual
animal’s body fat condition (Aoki et al.,
2011; Adachi et al., 2014), which
provided insight into foraging success
and ultimately individual health and
vital rates (Robinson et al., 2010).
Rolland et al. (2016) used photographic
data of North Atlantic right whales to
evaluate individual health and link it to
demographic groups and population
status. Additional studies exploring
population consequences are ongoing,
but a common theme is that extensive
data documenting individual health and
population vital rates are necessary for
such analyses. These are considered the
gold standards for future studies, but, at
present, studies within the GOM have
not occurred in sufficient detail for such
analyses.
For purposes of the analysis
contained herein, the disturbance
severity rating facet of the EWG
framework involves a relativistic
framework relating Level B harassment
to the zone-specific population size and
then evaluating this proportion to
specified severity criteria common
across species. In the idealized
framework discussed by the EWG
(Southall et al., 2017), the severity rating
involves consideration of the magnitude
of population affected and the duration
of disturbance, i.e., by deriving
magnitude-duration risk functions that
describe the potential effects of
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exposure to noise on affected
populations. The EWG considered that
a better approach would apply values
obtained using software developed to
implement the Interim PCOD approach
(Harwood et al., 2014; King et al., 2015).
While various models have been
developed implementing the PCOD
approach (e.g., New et al., 2013), the
approach is problematic for general
application because it is very dataheavy, and sufficient data specific to a
taxon and/or disturbance context is not
typically available. Few marine
mammal populations have been as
intensively studied as the PCOD case
study populations, and the lack of
appropriate datasets that link exposure
to disturbance with behavioral change,
and behavioral change with health,
currently limits the general applicability
of the full PCOD model. This difficulty
led to development of the Interim PCOD
approach, which uses results from an
expert elicitation process, rather than
empirical data, to predict the effects that
a specific amount of disturbance will
have on the vital rates of an individual
marine mammal. In evaluating potential
use of the Interim PCOD approach for
developing magnitude-duration curves
suitable for use in assessing risk
associated with the projected survey
activity considered here, the EWG used
the results of an expert elicitation
process that considered potential effects
of pile driving noise associated with the
construction of offshore wind farms on
bottlenose dolphins, harbor porpoises,
and minke whales in the North Sea.
While this evaluation provided proof-ofconcept and highlighted areas for future
improvement of the process, such
evaluations are not appropriately
extrapolated to a risk assessment
involving dissimilar species, stressors,
and locations. For example,
demographic rates and population
growth rates specific to those species in
U.K. waters of the North Sea were used
and, further, even in that expert
elicitation the authors warned that the
results for the minke whale were likely
not reliable due to a lack of available
data. The EWG recommended that the
available elicitation results not be used
towards the current analysis, and NMFS
and BOEM concurred. Currently, results
of these expert elicitation processes are
additionally viewed as potentially
unreliable because experts may
misinterpret the questions they are
asked (Booth et al., 2016).
Overall, while we agree with the
Associations that it would be ideal to
evaluate the effects of the specified
activity on the affected populations by
incorporating a PCOD or Interim PCOD
approach to the EWG framework,
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sufficient data are not available to
conduct a PCOD approach, and
sufficient resources were not available
to NMFS to develop and implement an
expert elicitation process specific to
seismic and the affected GOM
populations on a timeline amenable to
this ITR. With regard to the
Associations’ suggestion that outside
experts review the EWG framework, we
note that the EWG comprises experts
outside NMFS and BOEM who were
contracted for the express purpose of
developing the framework. We do not
believe it necessary to engage outside
experts to review the work of other
experts outside NMFS and BOEM,
which is itself subject to review by
experts within both NMFS and BOEM.
Comment: The Associations object to
the terminology used for the relative
severity ratings in the EWG framework
approach, stating their disagreement
with the implications of rating
descriptors such as ‘‘severe,’’ and
reiterating their belief that the modeled
exposure levels are incompatible with
the available data. Relatedly, the
Associations assert that there is ‘‘little
scientific support’’ for the relative risk
ratings for sperm and beaked whales.
Response: Respectfully, NMFS
believes this comment involves a
semantic issue. The Associations do not
suggest alternative terminology for the
relative risk ratings. Regarding the risk
ratings for sperm whales and beaked
whales, these ratings are a product of a
relatively straightforward analysis of
severity (i.e., amount of predicted
disturbance relative to population size)
and vulnerability (i.e., consideration of
factors inherent to the population that
make it more or less vulnerable to the
disturbance considered via the severity
rating). The Associations provide no
specific critique of any of these aspects
of the analysis. We have addressed the
Associations’ criticism of the acoustic
exposure modeling elsewhere in these
comment responses.
Comment: The Associations object to
use of the potential biological removal
(PBR) metric as the basis for evaluating
severity of Level A harassment within
the EWG framework, stating that its use
in evaluating non-serious injury is
inappropriate because the metric was
developed for evaluation of the
significance of serious injury and
mortality.
Response: We acknowledge that the
PBR metric defines a level of removals
from a population (i.e., mortality) that
would allow that population to remain
at its optimum sustainable population
level or, if depleted, would not increase
the population’s time to recovery by
more than 10 percent, and therefore that
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it is inappropriate to make comparisons
between Level B harassment takes and
the PBR value for any stock. However,
as discussed in the EWG report and in
the notice of proposed rulemaking,
while NMFS does not expect PTS (Level
A harassment) that might be accrued
through noise exposure to result in
mortality of marine mammals, PBR can
serve as a good surrogate for population
vulnerability/health. Accordingly, PBR
or a related metric can be used
appropriately as a value against which
to evaluate the potential severity to the
population of a permanent impact such
as PTS on a given number of
individuals, and it is only in this sense
that we use the PBR value. The
Associations do not provide an
alternative recommendation.
Small Numbers
Comment: The Associations and other
industry commenters express agreement
with NMFS’ interpretation of the small
numbers requirement as allowing that
the finding may be made at the
individual LOA level.
Response: We thank the Associations
for their comment in support of the
small numbers approach. NMFS’
analysis generally comports with many
of the points they raise, as discussed in
this preamble.
Comment: NRDC states that the
interpretation of ‘‘small numbers’’
presented by NMFS in the notice of
proposed rulemaking is contrary to the
plain meaning and purpose of the
MMPA, in part because NMFS allegedly
did not provide a reasoned basis for the
take limit proposed (i.e., one-third of the
best available species or stock
abundance estimate). NRDC makes four
specific claims. First, NRDC states that
one-third cannot be considered a ‘‘small
number.’’ Second, NRDC states that
Congress intended that takes be limited
to ‘‘infrequent, unavoidable’’
occurrences, and that NMFS has not
explained why the taking would be
infrequent or unavoidable. Third, NRDC
contends that NMFS should define
different small numbers thresholds on
the basis of the conservation status of
individual species. Finally, NRDC
believes that NMFS must account for
‘‘additive and adverse synergistic
effects’’ that may occur due to multiple
concurrent surveys in conducting a
small numbers analysis. Industry
commenters suggest that additional
detail is necessary regarding the basis
for NMFS’ small numbers threshold.
Response: NMFS disagrees with
NRDC’s arguments on this topic.
Although there is limited legislative
history available to guide NMFS and an
apparent lack of biological
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underpinning to the concept, we have
worked to develop a reasoned approach
to small numbers. As discussed in the
section of the notice of proposed
rulemaking entitled Small Numbers,
NMFS explains the concept of ‘‘small
numbers’’ in recognition that there
could also be quantities of individuals
taken that would correspond with
‘‘medium’’ and ‘‘large’’ numbers. As
such, NMFS has established that onethird of the most appropriate population
abundance number—as compared with
the assumed number of individuals
taken—is an appropriate limit with
regard to ‘‘small numbers.’’ This relative
approach is consistent with the
statement from the legislative history
that ‘‘[small numbers] is not capable of
being expressed in absolute numerical
limits’’ (H.R. Rep. No. 97–228, at 19
(September 16, 1981)), and relevant case
law (Center for Biological Diversity v.
Salazar, 695 F.3d 893, 907 (9th Cir.
2012) (holding that the U.S. Fish and
Wildlife Service reasonably interpreted
‘‘small numbers’’ by analyzing take in
relative or proportional terms)).
NRDC claims that a number may be
considered small only if it is ‘‘little or
close to zero’’ or ‘‘limited in degree.’’
We note that the comment selectively
picks a definition in support of NRDC’s
favored position. For example, the
definition of ‘‘small’’ in Webster’s New
Collegiate Dictionary (1981) included
‘‘having little size, esp. as compared
with other similar things.’’ See also
www.merriam-webster.com/dictionary/
small (defining ‘‘small’’ as ‘‘having
comparatively little size’’). These
definitions comport with the small
numbers interpretation developed by
NMFS, which utilizes a proportionality
approach. The comment also selectively
quotes the relevant legislative history
language, stating that Congress
‘‘intended that the agency limit takes to
‘infrequent, unavoidable’ occurrences.’’
The actual statement from the legislative
history is that taking of marine
mammals should be ‘‘infrequent,
unavoidable, or accidental.’’ H.R. Rep.
No. 97–228, at 19 (September 16, 1981)
(emphasis added). This language
suggests that taking that is unavoidable
(or accidental) may qualify as small
numbers, even if not infrequent.
The argument to establish a small
numbers threshold on the basis of stockspecific context is unnecessarily
duplicative of the required negligible
impact finding, in which relevant
biological and contextual factors are
considered in conjunction with the
amount of take. Similarly, NRDC’s
assertion that NMFS’ proposed
approach fails to account for ‘‘additive
and adverse synergistic effects’’ from
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multiple surveys is not required by
section 101(a)(5)(A) of the MMPA, and
it is unclear how NRDC defines this
concept or how it may be related to the
‘‘small numbers’’ concept. These
suggestions are not founded in any
relevant requirement of statute or
regulation, discussed in relevant
legislative history, or supported by
relevant case law.
A private citizen echoed certain of
NRDC’s comments on this topic, adding
that NMFS’ approach is ‘‘embarrassing
and scientifically indefensible.’’
However, the commenter does not
provide a more scientifically defensible
interpretation of small numbers,
suggesting only that ‘‘[o]ne could
approach this in many ways.’’
Regarding the comment that
additional explanation is needed for
NMFS’ interpretation of the small
numbers standard, we believe the
proposed and final rule provide
sufficient explanation for setting onethird as the upper limit for small
numbers where reasonably reliable
quantified take estimates are available.
See the Small Numbers section later in
this preamble.
Comment: Several commenters
suggest that the small numbers finding
need not be based on a quantitative
threshold.
Response: NMFS agrees that a more
qualitative small numbers finding may
be permissible. See, e.g., Center for
Biological Diversity v. Salazar, 695 F.3d
at 906–908. However, in this case,
where take estimates can be predicted
with relative confidence, we have
elected to set a quantitative threshold.
Moreover, the commenters do not
provide any specific recommendations
for an appropriate qualitative approach
in this case.
Comment: The MMC recommended
that any ‘‘formal interpretation’’ of the
small numbers standard by NMFS be
issued in a stand-alone, generally
applicable rulemaking (e.g., in
amendments to 50 CFR 216.103 or
216.105) or in a separate policy
directive, rather than in the preambles
to individual proposed rules.
Response: We appreciate the MMC’s
recommendation and may consider the
recommended approaches in the future.
We note, however, that providing
relevant explanations in a proposed ITR
is an effective and efficient way to
provide information to the reader and
solicit focused input from the public,
and ultimately affords the same
opportunities for public comment as a
stand-alone rulemaking would.
Comment: NRDC asserts that NMFS’
interpretation of the MMPA’s small
numbers requirement is contrary to law,
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stating their belief that NMFS must
make a small numbers determination in
the rule, rather than for issuance of
individual LOAs; that NMFS must
evaluate the same amount of take in
order to separately determine that the
total take will both meet the small
numbers standard and have a negligible
impact; and that NMFS’ approach
impermissibly cuts the public out of the
agency’s findings.
Response: Based on NMFS’ analysis
of the language and structure of section
101(a)(5)(A) and the implementing
regulations for that provision, NMFS
disagrees that the small numbers finding
must be based on the total of all take
over the five-year (or less) period from
all potential survey activity. The MMPA
does not define small numbers or
explain how to apply the term in either
section 101(a)(5)(A) or the similar
provision for incidental harassment
authorizations (IHAs) in section
101(a)(5)(D),6 including how to apply
the term in a way that allows for
consistency across those two provisions
that are similar but allow for potentially
different time and activity scales. (See
Small Numbers below.) Especially when
taken together with NMFS’
implementing regulations, our approach
is consistent with the structure of
section 101(a)(5)(A), which provides:
(i) Upon request therefor by citizens
of the United States who engage in a
specified activity (other than
commercial fishing) within a specified
geographical region, the Secretary shall
allow, during periods of not more than
five consecutive years each, the
incidental, but not intentional, taking by
citizens while engaging in that activity
within that region of small numbers of
marine mammals of a species or
population stock if the Secretary, after
notice (in the Federal Register and in
newspapers of general circulation, and
through appropriate electronic media, in
the coastal areas that may be affected by
such activity) and opportunity for
public comment—
(I) finds that the total of such taking
during each five-year (or less) period
6 Section
101(a)(5)(D) states in relevant part:
(i) Upon request therefor by citizens of the United
States who engage in a specified activity (other than
commercial fishing) within a specific geographic
region, the Secretary shall authorize, for periods of
not more than 1 year, subject to such conditions as
the Secretary may specify, the incidental, but not
intentional, taking by harassment of small numbers
of marine mammals of a species or population stock
by such citizens while engaging in that activity
within that region if the Secretary finds that such
harassment during each period concerned—
(I) will have a negligible impact on such species
or stock, and
(II) will not have an unmitigable adverse impact
on the availability of such species or stock for
taking for subsistence uses[.]
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concerned will have a negligible impact
on such species or stock and will not
have an unmitigable adverse impact on
the availability of such species or stock
for taking for subsistence uses [. . .].
(emphasis added).
Section 101(a)(5)(A)(i)(I) is explicit
that the ‘‘negligible impact’’
determination for a specified activity
must take into account the ‘‘total of such
taking’’ (i.e., all of the taking that the
Secretary may conceivably allow (or
authorize) under individual LOAs
during the five year (or less) period
considered for the rule). In contrast, the
‘‘small numbers’’ language in
101(a)(5)(A) is not subject to the same
time period requirement of five years (or
less in cases where the period being
considered for a rule is less than five
years).
In our view, the statutory language for
small numbers and the negligible
impact finding indicates that the
negligible impact finding is made based
on consideration of an aggregation of
potential authorizations (LOAs) for
taking small numbers of marine
mammals, and allows for different
temporal periods in applying the two
different standards. The statute
contemplates that the Secretary shall
allow taking during the five year (or
less) period, which in our view also
implies that there could be multiple
allowances or authorizations (i.e.,
LOAs), so long as the maximum
allowable total taking from all of those
authorizations combined is considered
in the upfront assessment of whether
the negligible impact standard is met.
As we have noted, the regulatory
vehicle for authorizing (i.e., allowing)
the take of marine mammals is the LOA,
a creature of NMFS’ long-standing
implementing regulations that is not in
the statute. See 50 CFR 216.106. Those
1989 implementing regulations
requiring an LOA to effectuate an
authorization were in effect when
Congress amended the MMPA in 1994
to add section 101(a)(5)(D) for issuance
of one-year IHAs, and over the years
when Congress amended section
101(a)(5)(A) for various reasons
(including most recently in 2018, to
extend the maximum authorization
period to seven years for military
readiness activities, Pub. L. 115–232
(John S. McCain National Defense
Authorization Act for Fiscal Year 2019)
(Aug. 13, 2018)). Presumably Congress
was aware of these implementing
regulations and the framework they
created for authorizing take under
section 101(a)(5)(A) and could have
invalidated those regulations had it so
desired.
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Under NMFS’ approach, the
negligible impact analysis for the
rulemaking is conducted for the time
period covered by the rule (five years in
this case, the maximum under the
statute for a non-military readiness
activity), but the small numbers analysis
attaches to the instrument that actually
‘‘allows’’ or authorizes taking, i.e., the
LOA. The statute does not preclude
NMFS from issuing an LOA that
comports with the small numbers level
set forth in the relevant rule for the
specified activity. Consistent with the
MMPA requirement, here the Secretary
(through NMFS) has prescribed the
necessary specified activity regulations
after notice and comment. At that point,
once the regulations are effective, NMFS
thereafter may authorize incidental take
through the issuance of LOAs, provided
that they satisfy the requirements set
forth in the rule and regulations,
including the small numbers standard
articulated in the rule.
NRDC cites Conservation Council for
Hawaii v. NMFS, 97 F. Supp. 3d 1210
(D. Hawaii 2015), in stating that the
MMPA ‘‘plainly requires that the agency
evaluate both whether there will be
small numbers of take and whether
there will be a negligible impact’’ before
issuing regulations, and that these
determinations ‘‘must be based on the
same amount of take.’’ We disagree. In
NMFS’ view, Conservation Council for
Hawaii stands for the proposition that
NMFS cannot authorize more take than
it has analyzed under the negligible
impact standard. 97 F. Supp. 3d at 1221.
There the court found that there were
substantial differences between the
anticipated take numbers, which were
the basis for the negligible impact
finding, and the amount of take that
NMFS was prepared to authorize
incidental to U.S. Navy military
readiness activities. That case did not
even involve the small numbers
provision, which does not apply in the
case of military readiness activities. 16
U.S.C. 1371(a)(5)(F)(i). The court in
Conservation Council for Hawaii did not
consider or make any pronouncements
about whether the small numbers
provision must be applied to the total
annual taking under the rule or whether
it could be applied at the LOA stage.
NRDC repeatedly states that the
negligible impact and small numbers
provisions must have separate meaning.
NMFS agrees that the two provisions do
have separate meanings, and this rule
satisfies that requirement. Each LOA
must meet the small numbers
requirement as NMFS has interpreted it
in this rule. In other words, it is not
sufficient for the survey activity
described in an LOA application to fall
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within the scope of the activity analyzed
for the rule and NMFS’ negligible
impact determination. The small
numbers limitation also must be
satisfied. For example, NMFS may
receive an application for an LOA where
the take estimates exceed the small
numbers standard identified in the rule.
In that case, the request would be
denied, even if the amount of taking was
considered in the negligible impact
evaluation. Thus the negligible impact
and small numbers inquiries are
separate and have different meanings.
To summarize, the MMPA is silent on
how to apply ‘‘small numbers’’ in either
section 101(a)(5)(A) or (D), including in
a way that allows for consistency across
those two very similar provisions.
Moreover, NMFS’ implementing
regulations for section 101(a)(5)(A)
make it clear that LOAs are the
instrument for authorizing take. Thus,
the mere existence of regulations under
101(a)(5)(A) for a specified activity is
not sufficient to authorize take under
that provision. An LOA is required.
As we have previously stated, the
small numbers standard has limited
biological relevance (i.e., there is a lack
of a biological underpinning for the
concept), but NMFS’ application of the
small numbers standard at the LOA
stage does not rely on that view for the
approach taken here (and moreover,
NMFS did not receive any public
comments offering an alternative
definition that is rooted in biological
concepts or is not conflated with
negligible impact considerations). As
the notice of proposed rulemaking
explained, NMFS’ interpretation and
approach are based on analysis of the
governing section 101(a)(5)(A) and
limited legislative history, as well as
consideration of section 101(a)(5)(D),
and our long-standing approach to
implementing section 101(a)(5)(A)
through separate LOAs. NMFS has
determined that the statute is
ambiguous in terms of what small
numbers means and how ‘‘small
numbers’’ must be applied, which
affords the agency reasonable discretion
in how to do so. After weighing various
policy considerations, NMFS exercised
its discretion to define small numbers
and apply small numbers
determinations at the LOA level.
Importantly, the final rule, which was
subject to notice and comment, sets the
small numbers standard for future LOAs
issued under the rule. Moreover,
contrary to NRDC’s assertions, NMFS
has set the total taking allowable for all
LOAs issued under the rule for this
specified activity—i.e., the taking that
was analyzed for the negligible impact
determination. If an LOA application for
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a survey provides take estimates that are
within the small numbers threshold set
in this rule, then the LOA for that
survey will be deemed to satisfy the
small numbers requirement.
As NRDC correctly points out, NMFS’
implementing regulations require
issuance of LOAs to be consistent with
the ‘‘total taking allowable’’ under the
activity-specific regulations. The
regulations for the specified activity also
reflect this. The rulemaking for these
regulations evaluated the level of
activity projected in BOEM’s update for
its petition, and NMFS’ negligible
impact determination is based on
consideration of that level (as are the
corresponding take estimates). Any LOA
must be within the amount analyzed for
the scope of the rule, and the total
amount of take under all issued LOAs
combined cannot exceed the amount
analyzed and ‘‘allowable’’ under the
rule for this activity.
Regarding the differences between the
processes under sections 101(a)(5)(A)
and (D), we did not mean to suggest that
section 101(a)(5)(A) is necessarily or
always more protective than and
preferable to 101(a)(5)(D). Rather,
section 101(a)(5)(A), which can span a
longer period of time and cover multiple
applicants through issuance of LOAs,
allows for a more comprehensive/
holistic analysis by the agency (one
negligible impact analysis for all
activities over the five-year (or less)
period and consideration of mitigation
appropriate for the full suite of
activities). Such an approach has the
potential to be more protective because
it allows for a more comprehensive
understanding of impacts, as well as a
mechanism to include holistic
mitigation that can more effectively
address both acute and chronic effects
resulting from multiple activities
covered under a rule. Section
101(a)(5)(A) also focuses public
attention on one rulemaking (rather
than—as would be the case for these
survey activities—potentially dozens of
IHA actions per year, each with separate
notice and comment), and allows for
other administrative efficiencies. We
note that BOEM applied for the
regulations in support of the oil and gas
industry, and prepared an EIS in
support of its own program related to
the permitting of the survey activities
that are the subject of this MMPA
application and rulemaking.
NRDC claims that the approach ‘‘is a
novel interpretation of the MMPA.’’
However, the rule cited in support of
their argument (81 FR 47240; July 20,
2016) is consistent with one aspect of
our approach here, in that the small
numbers determinations in both
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contexts are based on annual take
estimates, not total take over the fiveyear period of the regulations.7 We
acknowledge that we have not
previously determined that small
numbers could be applied at the
individual LOA stage where more than
one LOA applicant may apply under the
activity-specific regulations. However,
that is simply because the issue had not
previously presented itself. In nearly all
cases to date,8 there has been a single
operator who is the sole applicant for
both the LOA (or LOAs if they cover less
than the five-year period) and the
governing specified activity regulations.
As a result, in such a scenario, the small
numbers determination by default
corresponds to the maximum annual
taking covered by the regulation (and
the LOA). But even when there is only
one applicant for LOAs under a
regulation, NMFS does not tally take
across the five-year period for purposes
of assessing small numbers. Rather,
NMFS assesses annual levels of take.
(This also promotes consistency
between 101(a)(5)(A) and 101(a)(5)(D) to
avoid incentivizing IHAs at the expense
of LOAs issued under more
comprehensive rules.)
Finally, NRDC’s statement that the
public is impermissibly cut out of the
agency’s findings is incorrect. The
7 We further note that population biology often
focuses on annual cycles. See, e.g., 50 CFR 216.103
(negligible impact defined in terms of impacts on
annual rates of recruitment or survival); 16 U.S.C.
1386(a), (c) (requiring stock assessment reports to
estimate the annual human-caused mortality and
serious injury of the stock, and annual review of
stock assessments when significant new
information is available that may indicate the stock
assessment should be revised); 16 U.S.C. 1362(26)
(defining ‘‘net productivity rate’’ as the annual per
capita rate of increase in a stock resulting from
additions due to reproduction, less losses due to
mortality); 16 U.S.C. 1383a(l)(ii) (requiring MMC’s
recommended guidelines to govern the incidental
taking of marine mammals in the course of
commercial fishing operations, to the maximum
extent practicable, to include as a factor to be
considered and utilized in determining permissible
levels of taking ‘‘the abundance and annual net
recruitment of such stocks’’).
8 The one exception to date is NMFS’ regulation
governing the incidental take from explosive
removal of offshore structures in the GOM (EROS),
promulgated at the request of the Minerals
Management Service on behalf of multiple private
removal companies that individually submitted
LOA requests. NMFS’ rulemaking for the EROS
regulations evaluated the estimated annual take
based on MMS’ projections for the specified activity
as a whole, i.e., for all operators combined. Our rule
here is consistent with the EROS rulemaking as it
relates to the approach for the negligible impact
evaluation. However, the EROS rule also concluded
the total annual taking (by species) for all operators
combined met the small numbers requirement.
Thus NMFS did not have occasion before now to
consider whether it could apply the small numbers
provision at an individual LOA level where there
are multiple concurrent LOA holders. Having now
considered the question, NMFS believes the MMPA
affords the discretion to do so.
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proposed rule set forth the maximum
total taking and annual taking that
would be allowable (via the issuance of
LOAs) for the five-year period that the
regulations will be effective, which was
based on information contained in
BOEM’s publicly available application
and PEIS. Those figures decreased for
all but two species. For the two species
where the figures increased, we
evaluated those changes and determined
they do not represent a meaningful
change for our analyses. See Changes
From the Proposed Rule.
The proposed rule included a 60-day
public comment period. We also believe
that our rulemaking afforded a full and
focused opportunity for public review of
and comment on the full scope of
survey activities and proposed
mitigation, rather than through dozens
of individual IHAs, each with 30-day
public comment periods and shorter
timeframes for NMFS to consider the
public comments. Thus the public had
a meaningful opportunity to comment.
Comment: Citing their interpretation
of the statute and multiple judicial
decisions, the MMC suggests that
NMFS’ interpretation and
implementation of the small numbers
standard is contrary to law and further
recommends that NMFS adopt a policy
interpreting the small numbers
requirement of section 101(a)(5)(A) such
that it:
• Requires determinations be made
when issuing incidental take regulations
(as opposed to when LOAs are issued);
• makes such determinations based
on the total take authorized incidental
to the specified activity and for the full
duration covered by those regulations
(as opposed to for each LOA and on an
annual basis); and
• provides an opportunity for public
notice and comment on all small
numbers determinations.
Response: As explained in the
responses above and discussion under
the Small Numbers section of this
preamble, NMFS disagrees, based on
our analysis of the statute, the
legislative history, the implementing
regulations, and relevant case law.
NMFS issues incidental take
authorizations under section
101(a)(5)(A) through LOAs, provided
that we satisfy the relevant statutory
standards. Analysis of that statutory
provision and relevant legislative
history, including when read in
conjunction with section 101(a)(5)(D),
leads NMFS to conclude that the small
numbers limitation may be applied at
the LOA stage, provided that we make
the negligible impact finding for the
total taking allowable under the
regulations for the specified activity and
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set the small numbers standard for
future LOAs in the notice and comment
rulemaking.
As noted above, the term ‘‘small
numbers’’ is not defined in the statute.
Over the years NMFS has grappled with
how to define the term, particularly
given the limited legislative history (i.e.,
‘‘accidental, infrequent, or
unavoidable’’; ‘‘not capable of being
expressed in absolute numerical
terms’’). Recent court decisions lend
support for NMFS’ proportional
approach to the concept. See Center for
Biological Diversity v. Salazar, 695 F.3d
893 (9th Cir. 2012). In terms of what
proportion may constitute ‘‘small
numbers’’ for purposes of what the
Secretary may authorize, NMFS has
determined that small numbers means
up to one-third of a species or stock.
NMFS has further determined that this
limit can be applied at the LOA level,
subject to a finding that the total taking
allowable (through any and all LOAs
issued under the activity-specific rule
and corresponding regulations) satisfies
the negligible impact standard.
The MMC inaccurately states that the
‘‘interpretation of the small numbers
requirement proposed by NMFS in
many ways seeks to maximize the
numbers of takes of marine mammals
that may be authorized under a single
rulemaking.’’ With one exception, the
points raised by the MMC reflect NMFS’
existing practice. The decision to make
small numbers findings on an LOAspecific basis is the only new
development and, as explained in the
response to the previous comment,
came about only when the issue arose
for the first time in the context of this
rulemaking. NMFS considered the
specific issue, determined that section
101(a)(5)(A) does not unambiguously
speak to it, and reasonably exercised its
discretion in determining that small
numbers findings could apply at the
LOA stage, provided that the standard is
set forth in the rule itself, which it is.
We acknowledge that section
101(a)(5)(A) does not expressly
contemplate the issuance of LOAs,
which are a creature of NMFS and U.S.
Fish and Wildlife Service (FWS) joint
implementing regulations for section
101(a)(5)(A). (See 50 CFR 216 subpart I
(NMFS regulations); 50 CFR 18.27 (FWS
regulations)). Those implementing
regulations, in effect since 1989,
established LOAs as the regulatory
instrument to authorize lawful
incidental take under section
101(a)(5)(A), after the promulgation of
activity-specific regulations that
undergo notice and comment
rulemaking.
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Although not the typical scenario,
NMFS’ implementing regulations allow
for the issuance of LOAs to more than
one ‘‘U.S. citizen’’ taking marine
mammals under a specified activity
regulation, see, e.g., 50 CFR 216.105(a);
216.106(e); (54 FR 40338 (September 29,
1989)), provided that the negligible
impact finding is made for the total
taking for the specified activity as a
whole, by all entities conducting that
activity.
NMFS also administers section
101(a)(5)(D), a very similar provision
enacted in 1994 that established an
expedited process for the issuance of
one-year incidental take authorizations
for the taking of small numbers of
marine mammals by harassment only
when the taking from the specified
activity is found to have a negligible
impact on the affected species or stocks
of marine mammals (referred to as
incidental harassment authorizations, or
‘‘IHAs’’). See the Small Numbers section
later in this Notice. The small numbers
standard in section 101(a)(5)(D) applies
to each individual one-year IHA, yet the
same small numbers language also
appears in section 101(a)(5)(A). In
NMFS’ view, the statute is silent on how
to apply the same small numbers
limitation in these two provisions across
potentially different scales and
timeframes. In the case such as here,
where serious injury or mortality is not
expected from the activity (and would
not be authorized in any LOA), each
prospective LOA applicant could
instead opt to apply for an IHA under
section 101(a)(5)(D). It would be an
absurd result to deny an LOA for a
single geophysical survey on the sole
basis that small numbers is not satisfied
because the take numbers from that
survey must be aggregated with the
takes from other surveys occurring
under the same regulations, only to turn
around and issue an IHA for the same
survey, simply because the applicant
has decided to avail itself of section
101(a)(5)(D) instead. But that would be
the result under the MMC’s approach.
Given NMFS’ implementing regulations
for section 101(a)(5)(A), which are
authorized under 16 U.S.C. 1382(a), and
when viewed in light of section
101(a)(5)(D) and applying our
administrative experience, NMFS has
determined our approach is a reasonable
interpretation of how to carry out
section 101(a)(5)(A) and the
implementing regulations in the context
of these two statutory provisions. This
is a reasoned approach that draws on
NMFS’ expertise.
Further, authorization of take
incidental to geophysical survey activity
within the covered regions of the GOM
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under this ITR allows for the more
comprehensive evaluation and
management of take of marine mammals
than if NMFS were to authorize take for
those same activities under IHAs. NMFS
worked with BOEM and its predecessor
agency over many years to ensure a
process that holistically analyzed the
impacts from expected geophysical
surveys in the GOM. This is preferable
first and foremost for its greater
likelihood of achieving the best
substantive impact analysis and
comprehensive management (including
mitigation and monitoring) scheme, but
the process is also efficient for
stakeholders (regulated industry and
interested members of the public) and
results in more efficient use of
administrative agency resources.
The MMC argues that NMFS’
implementing regulations support the
MMC’s view of the application of small
numbers, because ‘‘whereas the
regulatory section governing the
issuance of incidental take regulations
(50 CFR 216.105) includes a reference to
the small numbers requirement, the
section governing LOAs (50 CFR
216.106) omits any reference to that
requirement.’’ However, the
implementing regulations originally
defined small numbers as synonymous
with negligible impact. NMFS no longer
interprets small numbers in that way,
but as a result of that original approach,
the MMC’s particular citations do not
shed light on the permissible approach
for making a small numbers
determination as that term is now
interpreted.
NMFS agrees with the MMC that
workload alone would not be a
sufficient basis for our interpretation,
and it is not what we rely on. Rather,
the analysis we presented leads us to
conclude that NMFS has discretion to
apply small numbers at the LOA level
and, in this case, policy considerations
supported that approach.
Comment: NRDC states that NMFS’
interpretation of small numbers ‘‘leads
to absurd results and permits excessive
take.’’
Response: NMFS’ negligible impact
assessment evaluated the risk to the
affected species and stocks of marine
mammals, taking into account the
amount and severity of anticipated take
(and take the agency is prepared to
authorize) as well as the status of the
species and mitigation/monitoring. Of
note, and as indicated in Changes from
the Proposed Rule, as a result of
BOEM’s updated scope of the activities
and the associated revisions to the
levels of effort, both the maximum
allowable amount of take under the rule,
as well as the maximum annual take,
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has decreased (significantly in some
cases) for all species and stocks except
two, for which maximum allowable take
and/or maximum annual take increased
slightly, and the severity of many of the
impacts has been lessened via the
elimination and/or reduction of take in
areas of greater biological importance
previously considered as mitigation
areas.
The numbers of potential incidents of
take or animals taken are only part of an
assessment and are not, alone,
decisively indicative of the degree of
impact. In order to adequately evaluate
the effects of noise exposure at the
population level, the total number of
take incidents must be further
interpreted in context of relevant
biological and population parameters
and other biological, environmental,
and anthropogenic factors and in a
spatially and temporally explicit
manner. The effects to individuals of a
‘‘take’’ are not necessarily equal. Some
take events represent exposures that
only just exceed a Level B harassment
threshold, which would be expected to
result in lower-level impacts, while
other exposures (fewer, as the exposure
modeling effort illustrates) occur at
higher received levels and would
typically be expected to have
comparatively greater potential impacts
on an individual. Further, responses to
similar received levels may result in
significantly different impacts on an
individual dependent upon the context
of the exposure or the status of the
individuals (e.g., if it occurred in an
area and time where concentrated
feeding was occurring, or to individuals
weakened by other effects). Last,
impacts of a similar degree on a
proportion of the individuals in a stock
may have differing impacts to the stock
based on its status, i.e., smaller stocks
may be less able to absorb deaths or
reproductive suppression and maintain
similar growth rates as larger stocks.
Comment: The MMC recommended
that if such determinations are made
based on a proportion of a species’ or
stock’s abundance, NMFS adopt a
policy interpreting the small numbers
requirement of section 101(a)(5)(A) such
that it: (1) Include a sliding scale, such
that a lower proportion is allowed as
stock size increases, and (2) include an
evaluation of the relative risk that the
established threshold would be
exceeded if the best available
population estimate or some other
metric, such as a minimum or
intermediate population, is used.
Response: NMFS disagrees with these
recommendations. Under the ‘‘onethird’’ interpretation offered here, and
on which we will base our small
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numbers analyses when evaluating LOA
applications under this rule, take
equating to greater than one-third of the
predicted individuals in the population
would generally not be considered small
numbers. The MMC presents an
example from a very large population,
asserting that an amount of take that
would meet NMFS’ proportional small
numbers standard would not
appropriately be considered ‘‘small’’
because it is large in terms of absolute
magnitude. The MMC does not present
a rationale for why its proposed sliding
scale approach is more appropriate, nor
does it provide an explanation of what
the drawbacks are (biological or
otherwise) of authorizing takes of large
numbers of marine mammals (in the
absolute sense) from a significantly large
(and arguably healthier and more
robust) population (even where still less
than one-third of the population under
NMFS’ proportional approach). We have
determined that a proportional
approach is the appropriate way to
interpret small numbers, not an absolute
‘‘on its face’’ numeric standard.
Accordingly, absolute numbers would
not be relevant to our small numbers
determinations. There is no meaningful
way to define what should be
considered as a ‘‘small’’ number on the
basis of absolute magnitude, and the
MMC offers no such recommendation.
Mitigation, Monitoring, and Reporting
Comment: NRDC states that NMFS
should include a year-round area
closure for Bryde’s whales. Specifically,
NRDC states that this should include the
following: (1) Excluding airgun surveys
year-round from the whales’ occupied
habitat; (2) excluding airgun surveys
from areas identified, through modeling,
as most likely to propagate lowfrequency sound into the Bryde’s
whales’ habitat; and (3) establishing
mitigation to reduce noise in the
whales’ unoccupied habitat, i.e., areas
they are likely to have inhabited
according to the whaling records and
have habitat characteristics similar to
those of the De Soto canyon. The MMC
also recommends that NMFS include a
year-round area closure for Bryde’s
whales, while agreeing that the area
defined by NMFS in the proposed rule
is appropriate. In addition, a private
citizen commented that a year-round
closure is more appropriate than a
seasonal closure, because Bryde’s
whales use the area year-round. The
Associations and other industry
commenters argue to the contrary,
stating that there should be no
restriction within the Bryde’s whale
area and that, if a restriction is required,
it should be seasonal rather than year-
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round. The Associations also state that
if implemented, the restriction area
should be smaller. With regard to the
other alternative offered by NMFS for
comment—no restriction but a
requirement to conduct real-time whale
detection through use of a moored
listening array—the Associations state,
‘‘the final ITR should not impose a
moored array requirement because the
limits inherent in such data are
outweighed by the impracticability of
such arrays.’’ The CRE also comments,
with no supporting information, that
there should be no restriction on survey
effort in the Bryde’s whale core habitat
area.
Response: As described in the
proposed rule, NMFS agrees with NRDC
and the MMC that the status (e.g., small
population size, restricted distribution,
anthropogenic effects, small population
effects) of the recently ESA-listed GOM
Bryde’s whale warranted the
consideration of a year-round closure to
airgun surveys within the area described
as core habitat for the whale (Area #3).
We disagree with the Associations’
arguments that no requirement is
warranted. However, the comments
specifically relating to the need (or lack
thereof) to impose a restriction on
survey effort in Bryde’s whale core
habitat, the duration of any such
restriction, or any additional
requirements in the core habitat area,
are no longer relevant following BOEM’s
updated scope of activity. This update
means that no survey effort within
Bryde’s whale core habitat is considered
through this rulemaking and the vast
majority of any anticipated or
authorized impacts to this species have
been eliminated. Please see Table 1 and
Figure 2, earlier in this notice.
Regarding NRDC’s recommendations
for establishing Bryde’s whale
mitigation measures beyond the core
habitat area identified in the notice of
proposed rulemaking, NMFS does not
believe these are warranted. We initially
note that the comment uses the terms
‘‘occupied and ‘‘unoccupied’’ to
describe habitat. These are terms of art
in the Endangered Species Act and
implementing regulations for
designation of ‘‘critical habitat.’’ For this
MMPA rulemaking, the correct standard
is measures to effect the ‘‘least
practicable adverse impact’’ on the
affected species or stocks and their
habitat. NMFS has now determined that
additional geographic-based mitigation
for Bryde’s whales is not warranted.
Following BOEM’s update to the scope
of their specified activity, expected
takes of Bryde’s whales are significantly
reduced in the remaining area where the
specified activity will occur under this
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rule (i.e., there are now no more than 10
anticipated instances of take annually;
see Table 9).
Regarding NRDC’s comments that
additional protections are needed in
areas that are ‘‘unoccupied’’ by the
Bryde’s whale, we disagree. NMFS’
objective in requiring a closure would
be to minimize the effects of airgun
surveys on Bryde’s whales while in
important habitat. In areas where
modeling and/or observational data
show a species or stock is unlikely to
occur during the period of the rule, it is
generally unlikely that a geographic or
other mitigative restriction would
reduce impacts from the specified
activities on the species or stock and its
habitat, and therefore is not justifiable
absent some other compelling basis.
Finally, we are unsure of what NRDC
might mean in recommending exclusion
of surveys from areas identified as most
likely to propagate low-frequency sound
into Bryde’s whale habitat, or whether
such areas are still covered by the rule
given BOEM’s updated scope, and
NRDC provides no meaningful
justification for the recommendation,
nor any useful recommendations for
how such areas could be identified.
Comment: In reference to NMFS’
statement that the agency does not
consider towed passive acoustic
monitoring (PAM) to be a useful tool
with regard to detection of Bryde’s
whales, the Associations state that they
do believe more typical real-time
detection-based mitigation, such as use
of towed PAM, should provide
sufficient protection for Bryde’s whales,
and assert that we did not provide
sufficient information to meaningfully
comment on the conclusion.
Response: It is generally wellaccepted fact that, even in the absence
of a firing airgun, using a towed passive
acoustic sensor to detect baleen whales
(including Bryde’s whales) is not
typically effective because the noise
from the vessel, the flow noise, and the
cable noise are in the same frequency
band and will mask the vast majority of
baleen whale calls. Further, Bryde’s
whales have relatively short calls,
further exacerbating the problem. As
background, airguns produce loud,
broadband, impulsive signals at low
frequencies (e.g., Hildebrand, 2004).
Source characteristics are variable but
typically peak pressures are in the 5–
300 Hz frequency range, with source
levels as high as 260 dB peak re 1 mPa
at 1 m output pressure (Hildebrand,
2009). Pulse rates are typically one per
10–20 s (Hildebrand, 2009). Seismic
survey noise can raise background noise
levels by 20 dB or more over large areas
while present. Because the seismic
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pulse and the whale’s call are within the
same frequency range, and the seismic
pulse is much louder than the whale’s
call (see below), it is extremely unlikely
that a baleen whale can be detected
during the pulse. In addition to the
actual seismic pulse (approximately
every 10–20 s), the background noise
level is expected to be significantly
increased as a result of the reverberant
field generated from seismic pulses
(Guerra et al., 2011; Guan et al., 2015),
i.e., during the inter-pulse interval. The
level of elevated inter-pulse noise levels
can be as high as 30–45 dB within 1 km
of an active 3,147 in3 airgun array
(Guerra et al., 2011). Given that towing
hydrophones for PAM used for marine
mammal monitoring would be within 1
km from the airgun source, the received
noise spectral density during the interpulse interval is expected to be very
high.
Vessels also produce low-frequency
noise, primarily through propeller
cavitation, with main energy also in the
5–300 Hz frequency range. Source levels
range from about 140 to 195 dB re 1 mPa
at 1 m (NRC, 2003; Hildebrand, 2009),
depending on factors such as ship type,
load, and speed, and ship hull and
propeller design. Studies of vessel noise
show that it appears to increase
background noise levels in the 71–224
Hz range by 10–13 dB (Hatch et al.,
2012; McKenna et al., 2012; Rolland et
al., 2012). PAM systems employ
hydrophones towed in streamer cables
approximately 500 m behind a vessel.
Noise from water flow around the cables
and from strumming of the cables
themselves is also low-frequency and
typically masks signals in the same
range.
GOM Bryde’s whale calls have
relatively low source levels (155 dB re
1mPa) and frequency ranges (78–110 Hz;
Sˇirovic´ et al., 2014) that overlap the
sounds described above. In addition,
GOM Bryde’s whales call only
infrequently (i.e., a 3.5 hour research
encounter with 4 whales resulted in
detections of 14 calls). The chances of
acoustically detecting these whales is
low under ideal research circumstances,
is much lower with elevated
background noise from the ship and
towing cable, and essentially impossible
with an airgun array shooting. Whales
are routinely detected acoustically using
moored systems and sonobuoys, or
using autonomous gliders. However,
these platforms are all quiet. A leading
provider of observer services for the
seismic industry, including PAM,
reports that they have never detected a
baleen whale (other than rare detections
of humpback whales, which have
significantly higher frequency content
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in their call) using PAM aboard a
working seismic vessel (S. Milne, RPS
Group, pers. comm.). Experienced PAM
operators participating in a recent
workshop (Thode et al., 2017)
emphasized that a PAM operation could
easily report no acoustic encounters,
depending on species present, simply
because background noise levels
rendered any acoustic detection
impossible. The same workshop report
stated that a typical eight-element array
towed 500 m behind a seismic vessel
could be expected to detect delphinids,
sperm whales, and beaked whales at the
required range, but not baleen whales,
due to expected background noise levels
(including seismic noise, vessel noise,
and flow noise).
Comment: The Associations provided
comments regarding NMFS’ proposed
power-down exception to the general
shutdown requirements for certain
species of dolphin, as well as the related
alternative of no shutdown or powerdown requirement. The Associations
stated that no shutdowns for dolphins
are warranted, and added that an
exception should not be limited to small
dolphins but rather should be expanded
to all delphinid species. The MMC
recommended that NMFS not require a
shutdown or power-down when small
delphinids enter the exclusion zone,
and relatedly suggested that NMFS
should provide clarification as to the
basis for exempting only small
delphinids from shutdowns. The MMC
stated their agreement with NMFS that
shutting down when small delphinids
enter the exclusion zone is not
warranted and may result in additional
survey activity. Furthermore, as
indicated in the MMC comments,
power-down may not be effective. The
MMC stated that, given the variation in
array characteristics and configuration,
a requirement to ‘‘power-down’’ does
not provide sufficient assurance that the
resulting received levels would be
below the Level B harassment threshold.
CGG provided a detailed analysis of the
potential operational costs associated
with dolphin shutdowns or powerdowns, supporting their comment that
these costs would be substantial and
that shutdown or power-down should
not be required. NRDC provided
multiple objections to NMFS’ proposals,
stating that of the two proposals they
favor power-down.
Response: Following review of the
available information and public
comments, NMFS agrees that a general
exception to the standard shutdown
requirement is warranted for small
delphinids, and that the alternative
power-down requirement may not be
effective and yet could impose costs on
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operators. (Here we refer to ‘‘large
delphinids’’ and ‘‘small delphinids’’ as
shorthand for generally deep-diving
versus surface-dwelling/bow-riding
groups, respectively, as the important
distinction is their dive behavior rather
than their size.) As NMFS discussed in
the notice of proposed rulemaking, midand high-frequency cetaceans are
relatively insensitive to the frequencies
where the most energy in an airgun
signal is found. In order to demonstrate
this quantitatively, a ‘‘spectral ratio’’
may be calculated for each hearing
group. This ratio essentially compares
the energy in a group-specific weighted
airgun source spectrum with the energy
in an unweighted airgun source
spectrum, providing a representation of
the proportion of total energy from the
unweighted airgun spectrum that is
available for animals to hear based on
their group-specific general auditory
filter shapes, which presumably
influences the probability of behavioral
response. Using M-weighting (i.e., Type
I filters), spectral ratios for the three
hearing groups are as follows: LF, 0.71;
MF, 0.03; HF, 0.02.
However, NMFS does not agree that
the available evidence supports certain
commenters’ assertions that seismic
surveys do not have any adverse effects
on dolphin species. As discussed in
Mitigation, auditory injury is not
expected for dolphins, but the reason for
dolphin behavior around vessels (when
they are attracted) is not understood and
cannot be assumed to be harmless. In
fact, the analyses of Barkaszi et al.
(2012), Stone (2015a), Stone et al.
(2017), and Barkaszi and Kelly (2018)
show that dolphins do avoid working
vessels. That said, the available
information does not suggest that such
reactions are likely to have meaningful
energetic effects to individuals such that
the effectiveness of such measures
outweighs the practicability concerns
raised by commenters, in terms of the
operational costs as well as the
difficulty of implementation.
As noted above, the proposed rule
included an alternative in which a
power-down requirement would be
required. However, following review of
public comments, NMFS believes that a
power-down requirement would
potentially lead to the need for
termination of survey lines and infill of
the line where data were not acquired
if a power-down was performed
according to accepted practice, in which
the power-down condition would last
until the dolphin(s) are no longer
observed within the exclusion zone. The
need to revisit missed track line to
reacquire data is likely to result in an
overall increase in the total sound
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energy input to the marine environment
and an increase in the total duration
over which the survey is active in a
given area.
NMFS disagrees with comments that
no shutdown requirements should
apply to any delphinid species
regardless of behavior. As noted above,
industry commenters have asserted that
no shutdown requirements are
warranted for any delphinid species,
stating that the best available science
does not support imposing such
requirements. The industry comments
acknowledge that small delphinids are
more likely to approach survey vessels
than large delphinids, but claim without
supporting data that there is no
evidence that large delphinids will
benefit from a shutdown requirement. In
contrast to the typical behaviors of (and
observed effects on) the small delphinid
species group, the typical deep diving
behavior of the relatively rarely
occurring large delphinid group of
species makes these animals potentially
susceptible to interrupted/delayed
feeding dives, which can cause
energetic losses that can accrue to affect
fitness. As described in greater detail in
the notice of proposed rulemaking, there
are ample data illustrating the responses
of deeper diving odontocetes (including
large delphinids) to loud sound sources
(including seismic) to include
interrupted foraging dives, as well as
avoidance with increased speed and
stroke rate, both of which may
contribute to energetic costs through
lost feeding opportunities and/or
increased energy demands. Significant
advances in study of the population
consequences of disturbance are
informing our understanding of how
disturbances accrue to effects on
individual fitness (reproduction and
survival) and ultimately to populations
via the use of energetic models, where
data are available for a species, and
expert elicitation when data are still
limited. The link between behavioral
disturbance, reduced energy budgets,
and impacts on reproduction and
survival is clear, as is the value in
reducing the probability or severity of
these behavioral disturbances where
possible. Therefore, NMFS finds that
there is support for the effectiveness of
the standard shutdown requirement as
applied to the large delphinid species
group.
Further, the claim that shutdowns for
these deep-diving species would be
impracticable was not accompanied by
supporting data. The data available to
NMFS demonstrates that this
requirement is practicable. For example,
recent synthesis of observer data in the
GOM shows that large delphinids were
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sighted only rarely, and that of these
sightings, almost half were not within
the 500-meter exclusion zone. We note
that the Associations provided a
quantitative analysis of ‘‘historical PSO
and PAM data from over 32,000 survey
activity hours conducted in the GOM
between 2007 and 2017,’’ but provide
no citation for these data (nor the data
itself). Therefore, we cannot verify or
meaningfully evaluate the industrysupplied analysis. Nevertheless, as
detailed herein, NMFS agrees in
substantial part with the comments
received and accordingly do not require
shutdown or power-down for small
delphinids detected within the
exclusion zone.
Comment: Several commenters
criticized our proposal to require
shutdowns upon detection of certain
species or circumstances (e.g., beaked
whales, Bryde’s whales) at any distance.
The Associations suggest that such
requirements are ‘‘arbitrary and
unlawful’’ because they require
shutdowns in ‘‘circumstances in which
no disturbance or harassment will
occur.’’ The Associations contend that
PSOs are likely to make frequent
‘‘precautionary’’ shutdown calls for
uncertain observations ‘‘at any
distance,’’ and that these measures will
have negative impacts on the
effectiveness of visual PSOs. CGG makes
similar claims, stating that ‘‘there is no
proven or likely efficacy to initiate a
shutdown for cetaceans that are well
outside of incidental take range’’ and
concluding that the standard 500-m
exclusion zone should be applied in
these circumstances. The MMC
commented that, in reference to the two
proposals of ‘‘at any distance’’ or
‘‘within 1 km,’’ they support the
implementation of shutdowns for
detections at any distance (rather than
within 1 km of the airgun array), based
on the status of the applicable species,
their small population sizes, and their
sensitivity to seismic sound.
Response: As discussed below and in
Mitigation, an extended shutdown
distance of 1.5 km is included in the
final rule, in lieu of the ‘‘at any
distance’’ shutdown included in the
proposed rule. We first note that the
industry comments against proposed
shutdowns for certain species, in their
view beyond the range at which
harassment may occur, appears to
reflect an assumption that the singlestep 160-dB threshold is the relevant
metric for harassment. Even if this were
the case, the minimum distance to the
160-dB isopleth, based on 60 different
propagation modeling scenarios, would
be beyond the likely detection distance
for visual observers. The smallest
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threshold radius to the 160-dB isopleth
is more than 7 km. However, the multistep probabilistic risk function used
here assumes that 10 percent of the
population exposed above 140 dB
would experience harassment; isopleth
distances to 140 dB, based on the same
modeling exercise, are typically greater
than 50 km (minimum of approximately
29 km). Even the 90 percent harassment
isopleth (i.e., 180 dB) has a mean
distance of 1.6 km. Therefore, the claims
that shutdowns upon detection ‘‘at any
distance’’ would occur in circumstances
where there is no harassment are
incorrect. The Associations’ comments
are also inconsistent in that they imply
both that marine mammals are likely to
be detected at ranges significantly
distant from the vessel, where
shutdowns would be effected on
detection of animals not subject to
harassment, and that marine mammals
cannot be adequately identified beyond
close distances, resulting in unnecessary
‘‘precautionary’’ shutdowns. NMFS
agrees that visual monitoring under
typical circumstances is unlikely to be
effective at ranges much beyond the
extended distance shutdown of 1.5 km,
while under ideal circumstances
acoustic detectability will also be
limited to within the exclusion zone
distance. (NMFS presented a detailed
analysis in the notice of proposed
rulemaking demonstrating that acoustic
detections of sperm whales during
active firing of an airgun array are not
likely beyond approximately 500 m).
Moreover, we specify in these
regulations that shutdowns are required
on positive identification of relevant
species (as determined through
professional judgment), meaning that
there is no real likelihood that there
would be numerous shutdowns based
on false positive detections. Overall, it
is unlikely that there will be
‘‘unnecessary’’ shutdowns to any
significant degree.
The MMC provided the following
supporting rationale to their comment:
‘‘Bryde’s whales are LF cetaceans with
particular sensitivity to the
predominantly low-frequency energy
output of airguns. Beaked whales are
well-documented to react behaviorally
to sound levels well below those
thought to cause injury, and larger
exclusion zones have been
recommended for beaked whales and
other deep-diving whales (such as Kogia
spp. and sperm whales) as they are more
likely to exhibit a stress response when
disturbed (Wright et al., 2011).’’ NMFS
agrees with these comments. In these
cases, we have identified species or
circumstances with particular
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sensitivities for which we determined it
appropriate to minimize the duration
and intensity of the behavioral
disruption, as well as to minimize the
potential for auditory injury (for lowand high-frequency cetaceans).
NMFS disagrees with industry
comments regarding the likelihood that
trained, experienced professional PSOs
would misunderstand the intent of a
requirement to shut down upon
detection ‘‘at any distance’’ and would
therefore spend undue time focusing
observational effort at distances beyond
approximately 1,000 m from the
acoustic source (i.e., the zone within
which we assume that monitoring is
typically focused, though not
necessarily exclusively). Nevertheless,
in order to ensure that this potential is
minimized, and to address commenters’
concerns regarding the potential costs
associated with shutdowns at any
distance, especially in light of the
diminished benefits of the measure
beyond 1.5 km, we limit these
shutdowns to within 1.5 km (versus at
any distance). The rationale for this
distance is explained later in this
document in Mitigation.
Comment: NRDC states that NMFS
should require that ramp-up occur over
several stages in order to minimize
exposure.
Response: NMFS agrees with NRDC
on this point, which appears to restate
the ramp-up procedures described by
NMFS in the notice of proposed
rulemaking. NMFS believes this
approach is consistent with the
Australian study referenced by NRDC.
Comment: NRDC states that the
standard 500-m exclusion zone is ‘‘not
conservative,’’ asserting that NMFS did
not explain why the proposed zone
achieves the least practicable adverse
impact and stating that NMFS must
consider other exclusion zone distances.
Response: NMFS has acknowledged
that some limited occurrence of
auditory injury is likely, for low- and
high-frequency cetaceans. However, we
disagree that a larger standard exclusion
zone is warranted. As explained in the
notice of proposed rulemaking, NMFS’
intent in prescribing a standard
exclusion zone distance is to (1)
encompass zones for most species
within which auditory injury could
occur on the basis of instantaneous
exposure; (2) provide additional
protection from the potential for more
severe behavioral reactions (e.g., panic,
antipredator response) for marine
mammals at relatively close range to the
acoustic source; (3) provide consistency
and ease of implementation for PSOs,
who need to monitor and implement the
exclusion zone; and (4) to define a
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distance within which detection
probabilities are reasonably high for
most species under typical conditions.
The use of 500 m as the zone is not
based directly on any quantitative
understanding of the range at which
auditory injury would be entirely
precluded or any range specifically
related to disruption of behavioral
patterns. Rather, NMFS believes it is
based on a reasonable combination of
factors. In summary, a practicable
criterion such as this has the advantage
of familiarity and simplicity while still
providing in most cases a zone larger
than relevant auditory injury zones,
given realistic movement of source and
receiver. Increased shutdowns, without
a firm idea of the outcome the measure
seeks to avoid, simply displace survey
activity in time and increase the total
duration of acoustic influence as well as
total sound energy in the water, which
NMFS seeks to avoid.
NMFS agrees that, when practicable,
the exclusion zone should encompass
distances within which auditory injury
is expected to occur on the basis of
instantaneous exposure. For highfrequency cetaceans, this distance was
modeled as 457 m (though we
acknowledged that the actual distance
would be dependent on the specific
airgun array and could be larger).
However, we require an extended
exclusion zone of 1.5 km for certain
sensitive species, including Kogia spp.
Potential auditory injury for lowfrequency cetaceans is based on the
accumulation of energy, and is therefore
not a straightforward consideration.
However, the extended exclusion zone
is required for the only low-frequency
cetacean in the GOM (Bryde’s whale). In
keeping with the four broad goals
outlined above, and in context of the
information given here, the standard
500-m exclusion zone is appropriate.
NRDC does not provide any substantive
reasoning for a larger zone.
Comment: Several industry
commenters criticized the requirement
for use of buffer zones in addition to the
standard exclusion zones, claiming in
part that there is no scientific basis for
monitoring a zone larger than the
exclusion zones.
Response: NMFS disagrees with the
suggestion that there is no scientific
basis for this requirement. It is
important to implement a larger zone
during pre-clearance, when naı¨ve
animals may be present and potentially
subject to severe behavioral reactions if
airguns begin firing at close range.
While the delineation of zones is
typically associated with shutdown, the
period during which use of the acoustic
source is being initiated is critical, and
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in order to avoid more severe behavioral
reactions it is important to be cautionary
regarding marine mammal presence in
the vicinity when the source is turned
on. This requirement has broad
acceptance in other required protocols:
The Brazilian Institute of the
Environment and Natural Resources
previously required a 1,000-m preclearance zone before recently
extending the exclusion zone to
encompass the entire 1,000-m zone
(IBAMA, 2005, 2018), the New Zealand
Department of Conservation requires
that a 1,000-m zone be monitored as
both a pre-clearance and a shutdown
zone for most species (DOC, 2013), and
the Australian Department of the
Environment, Water, Heritage and the
Arts requires an even more protective
scheme, in which a 2,000-m ‘‘power
down’’ zone is maintained for higherpower surveys (DEWHA, 2008). Broker
et al. (2015) describe the use of a
precautionary 2-km exclusion zone in
the absence of sound source verification
(SSV), with a minimum zone radius of
1 km (regardless of SSV results). We
believe that the simple doubling of the
exclusion zone required here is
appropriate for use as a pre-clearance
zone.
Comment: CGG comments that
shutdowns based on acoustic detections
should be required only when the
acoustic PSO is confident that the
vocalization is from a non-delphinid
species within the exclusion zone, as
opposed to when the PSO is confident
that the animal is outside of the
exclusion zone.
Response: We are unclear as to the
practical impact of what appears to be
a fairly nuanced difference, but clarify
that shutdown upon acoustic detection
of non-delphinids within the exclusion
zone is required when the animal is
detected acoustically and localized
within the exclusion zone. However, we
also note that PSO decision-making
regarding shutdown implementation
shall be informed to a reasonable extent
by professional judgment.
Comment: NRDC suggests that NMFS
is remiss in not limiting the amount of
activity that can occur overall (to a
lesser amount than analyzed in the
rule). Relatedly, NRDC suggests that
NMFS must consider ‘‘placing a cap on
the amount of allowable seismic
activity.’’
Response: Such a requirement is not
within NMFS’ authority under the
MMPA, assuming that the requisite
findings are made. NMFS’ responsibility
is to evaluate the potential effects of the
specified activity as presented by the
applicant (BOEM in this case, acting on
behalf of future industry applicants) and
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to determine whether the total taking
will have a negligible impact on the
affected species or stocks (among other
things). If NMFS is unable to make the
necessary finding, the applicant may
then consider a revision to the specified
activity that could lead to NMFS being
able to make the necessary finding of
negligible impact (or in some cases
additional mitigation may enable a
negligible impact finding). However, in
this case, NMFS has made a finding of
negligible impact, and it is not within
NMFS’ authority to unilaterally impose
a reduction in activity levels to some
degree (NRDC does not specify the
degree or distribution of reduction in
time or space that they would find
acceptable).
Comment: NRDC expressed concern
regarding the efficacy of the prescribed
visual and acoustic monitoring
methods, stating that species could go
undetected.
Response: While NMFS disagrees
with some specific comments regarding
efficacy, we generally agree with the
overall point that there are limitations
on what may reasonably be expected of
either visual or acoustic monitoring.
While visual and acoustic monitoring
effectively complement each other, and
acoustic monitoring is the more
effective monitoring method (for certain
species) during periods of impaired
visibility, there is no expectation that
these methods will detect all marine
mammals present. In general, NRDC
appears to misunderstand what NMFS
claims with regard to what such
monitoring may reasonably be expected
to accomplish and/or the extent to
which we rely on assumptions regarding
the efficacy of monitoring in reaching
the necessary findings. We acknowledge
these limitations in prescribing these
monitoring requirements, while stating
why NMFS believes that visual and
acoustic monitoring, and the related
protocols we have prescribed, are an
appropriate part of the suite of
mitigation measures here that satisfy the
MMPA’s least practicable adverse
impact standard. However, the
negligible impact finding is not
conditioned on the presumption of a
specific degree of monitoring efficacy.
Comment: The MMC recommends
that NMFS expand its shutdown
requirement for sperm whales to
include both visual and acoustic
detections at extended distance, stating
that vital functions of sperm whales,
including both foraging and resting,
should be afforded the additional
protection of the extended shutdown
zone. NRDC asserts that acoustic
shutdowns for sperm whales, which
they believe are not required under the
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ITR, would not be effective. The CRE
comments that they ‘‘agree with [NMFS]
that sperm whale shutdowns are not
warranted.’’
Response: NMFS agrees with the
MMC’s recommendation and has made
the recommended change (albeit within
a revised extended distance shutdown
zone of 1.5 km; see Mitigation).
However, we note the MMC’s statement
that ‘‘[t]he requirement for
implementing shut-down procedures
upon acoustic detection of a sperm
whale was inadvertently omitted from
the proposed regulatory text.’’ NMFS
disagrees with this statement. The
proper interpretation of the proposed
regulatory text was that such shutdowns
would be required. Nevertheless, the
revised, final regulatory text makes this
requirement clearer, in addition to
making the change to be inclusive of
visual detections at the greater distance.
Regarding the CRE’s comment, NMFS
did not determine that ‘‘sperm whale
shutdowns are not warranted.’’
Shutdowns for sperm whales have been
required in the GOM for over a decade,
and NMFS does not make any findings
that this should change.
With regard to NRDC, we reference
this comment only to provide necessary
clarification. Because NRDC mistakenly
claims that ‘‘NMFS hasn’t included an
acoustic shutdown requirement for
sperm whales in its proposed
regulation,’’ we refer the reader to the
notice of proposed rulemaking, in
which we state that shutdown of the
acoustic source is required upon
acoustic detection of a sperm whale
(29274–29275). (‘‘We are proposing that
shutdown of the acoustic source should
also be required in the event of certain
other observations [. . .]. Circumstances
[. . .] include [. . .] acoustic detection
of a sperm whale.’’) This requirement is
carried forward in this final ITR, as
modified (see Mitigation).
With regard to the efficacy of the
measure, we are confused as to NRDC’s
comments. NRDC first asserts that
sperm whales are the only species for
which acoustic detection may
reasonably be assumed, but then
seemingly states that implementation of
the measure is not sufficiently effective
as to be considered in context of
reducing impacts to sperm whales. As
discussed in greater detail elsewhere,
NMFS believes that shutdowns for
sperm whales at an extended distance,
on the basis of both acoustic and visual
detections (the latter added in this final
ITR), will meaningfully reduce impacts
to the species.
Comment: NRDC asserts that NMFS
does not fulfill the MMPA’s requirement
to prescribe mitigation achieving the
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‘‘least practicable adverse impact’’ to
marine mammal habitat, and
specifically notes that NMFS does not
separately consider mitigation aimed at
reducing impacts to marine mammal
habitat, as the MMPA requires.
Response: NMFS disagrees with this
comment. Our discussion of least
practicable adverse impact points out
that because habitat value is informed
by marine mammal presence and use, in
some cases there may be overlap in
measures for the species or stock and for
use of habitat. In the notice of proposed
rulemaking, NMFS identified time-area
restrictions based on a combination of
factors that include higher densities and
observations of specific important
behaviors of the animals themselves, but
also clearly reflect preferred habitat. In
addition to being delineated based on
physical features that drive habitat
function (e.g., bathymetric features,
among others), the high densities and
concentration of certain important
behaviors (e.g., feeding) in these
particular areas clearly indicates the
presence of preferred habitat. Also,
NRDC asserts that NMFS must
‘‘separately’’ consider measures aimed
at marine mammal habitat. The MMPA
does not specify that effects to habitat
must be mitigated in separate measures,
and the notice of proposed rulemaking
clearly identified measures that provide
significant reduction of impacts to both
‘‘marine mammal species and stocks
and their habitat,’’ as required by the
statute. Last, we note that NRDC
acknowledges that the measures
identified in the notice of proposed
rulemaking measures would reduce
impacts on ‘‘acoustic habitat.’’
Following BOEM’s update to the scope
of activity, two of the three time-area
restrictions identified and proposed by
NMFS now fall outside the area in
which survey activity may be
considered under this rule.
Comment: NRDC recommends that
NMFS should consider a year-round
restriction on geophysical survey
activity within coastal waters in the
footprint of the DWH oil spill, and that
NMFS must expand its proposed GOMwide coastal restriction temporally to
include the month of January.
Conversely, the Associations state that
no coastal restriction should be
required. The MMC recommends that
the proposed coastal closure be
expanded temporally such that the
timeframe is from January through
August.
Response: NMFS finds aspects of both
NRDC’s and the Associations’
statements with which we agree and
disagree and, as discussed in Mitigation,
have revised the time-area restriction.
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This restriction on airgun survey
activity (‘‘Area 1’’) was proposed as
including all GOM waters inside the 20m isobath, from February through May.
The revised restriction is limited to
those waters inside the 20-m isobath
from 90 ° to 84 ° W. Temporally, the
restriction is expanded to be in effect
from January through May.
The Associations provide extensive
comments relating to the impacts on
practicability presented by the proposed
restriction. The potential economic
consequences of the measure are
addressed in greater detail in the
regulatory impact analysis (RIA), which
analysis we adopt as a portion of our
practicability assessment for the revised
measure. NMFS agrees that there will
likely be negative economic and
operational consequences of the
restriction, though these consequences
are difficult to assess (and cannot
reasonably be assessed quantitatively)
(see the RIA for full analysis). While the
Associations express concerns regarding
the practicability analysis as being too
vague, they fail to provide additional
specific information that would help to
improve the analysis. For example, the
Associations state that data from the
area contained within the restriction are
outdated and that the restriction will
impede industry’s ability to identify
prospects in coastal areas, but provide
no specific information to support these
claims, such as information about the
data that do exist or the areas where
industry anticipates having interest in
identifying prospects. Despite the lack
of information provided in support of
the practicability concerns, NMFS takes
seriously the Associations’ concerns,
and therefore did consider eliminating
the restriction.
The Associations also assert that the
restriction would not result in any
meaningful benefit to coastal bottlenose
dolphin populations. NMFS disagrees
that this is the case. Although dolphins
are less sensitive to the frequencies at
which the greatest energy in an airgun
signal is found, we have described the
large body of evidence of adverse or
aversive behavior by various dolphin
species during airgun firing (e.g., Goold
and Fish, 1998; Stone and Tasker, 2006;
Barkaszi et al., 2012; Stone, 2015a;
Barkaszi and Kelly, 2018). Considered
in context of a generic dolphin
population with no notable issues
affecting the population as part of the
environmental baseline, it may be
reasonable to assume that such effects
are not indicative of any response of a
severity such that the need to avoid it
outweighs the impact on practicability
for the industry and operators. However,
as was described in the notice of
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proposed rulemaking, and as discussed
in NRDC’s comment, coastal bottlenose
dolphins in the GOM—particularly the
northern coastal stock of bottlenose
dolphins—were severely impacted by
the DWH oil spill.
As explained in the notice of
proposed rulemaking, while none of the
dolphin strandings or deaths have been
attributed to airgun survey activities,
stocks in the area are stressed and the
northern coastal stock in particular is in
extremely poor health. The
Associations’ discussion of NMFS’
analysis—claiming that our justification
for the restriction was premised merely
on ‘‘the broad understanding that
‘marine mammals react to underwater
noise’ ’’—is factually mistaken. As we
stated, behavioral disturbance or stress
may reduce fitness for individual
animals and/or may exacerbate existing
declines in reproductive health and
survivorship. For example, stressors
such as noise and pollutants may be
expected to induce responses involving
the neuroendocrine system, which
controls reactions to stress and regulates
many body processes (NAS, 2017), and
there is strong evidence that petroleumassociated chemicals can adversely
affect the endocrine system, providing a
potential pathway for interactions with
other stressors (Mohr et al., 2008, 2010).
Romano et al. (2004) found that upon
exposure to noise from a seismic
watergun, bottlenose dolphins had
significantly elevated levels of a stressrelated hormone and, correspondingly, a
decrease in immune cells. As we stated,
the restriction is intended specifically to
avoid additional stressors to these
coastal bottlenose dolphin populations
during the time period believed to be of
greatest importance as a reproductive
period. The Associations do not
contradict this information, instead
weakly relating the concern to the
potential for dolphins to experience
damage to auditory structures (which
NMFS agrees is unlikely) or to the idea
that ‘‘reactions’’ to noise are
innocuous.9
Population-level impacts related to
energetic effects or other impacts of
noise are difficult to determine, but the
addition of other stressors can add
9 The Associations also apparently misunderstand
some discussion of stranding events (which have
occurred primarily as a result of military use of
mid-frequency active sonar) provided in the notice
of proposed rulemaking, interpreting this
discussion as NMFS’ ‘‘suggestion that seismic
surveys are similar to mid-frequency sonar (which
has been implicated in strandings) simply because
seismic signatures include a mid-frequency
component.’’ We suggested no such thing and agree
with the Associations that airguns and sonar are
very different sound sources with very different
potential to cause strandings.
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considerable complexity due to the
potential for interaction between the
stressors or their effects (NAS, 2017).
When a population is at risk, NAS
(2017) recommends identifying those
stressors that may feasibly be mitigated.
We cannot undo the effects of the DWH
oil spill, but the potentially synergistic
effects of noise due to the activities that
are the subject of this rule may be
mitigated. However, NMFS does
acknowledge that the two populations
of greatest concern—the western and
northern coastal stocks of bottlenose
dolphin—do not have the same status.
As identified in the notice of proposed
rulemaking, while both stocks were
impacted by the DWH oil spill, the
northern coastal stock in particular was
perhaps the single most heavily
impacted stock, with 82 percent of
animals belonging to the stock expected
to have been exposed to oil, resulting in
a possible population reduction of 50
percent (this latter figure was only five
percent for the western stock). The
northern coastal stock was also subject
to a recent Unusual Mortality Event
(UME), described later in this notice
(see Description of Marine Mammals in
the Area of the Specified Activity).
NMFS acknowledges the uncertainty
associated with predicting the ways in
which different stressors may interact,
or how the effects of a stressor might be
exacerbated in an unhealthy population.
However, as an example, Schwacke et
al. (2014a) described findings indicating
that a significant proportion of the
population is expected to exhibit
adrenal insufficiency as a result of oil
exposure. Adrenal insufficiency can
lead to adrenal crisis and death in
animals that are challenged with other
stressors (Venn-Watson et al., 2015b).
NMFS agrees that the potential
practicability concerns warrant
consideration and, in light of the
differential baselines for the potentially
affected coastal stocks, has determined
it appropriate to contract the restriction.
However, the post-DWH oil spill
baseline condition of the northern
coastal stock, as exacerbated by the
recent UME, requires caution. This
restriction may reasonably be
anticipated to provide additional
protection to these populations during
their peak reproductive activity. We
note that NRDC’s proposed focus area
for heightened restriction aligns
generally with this area of concern, but
that in aligning with the footprint of the
spill rather than with the stock
boundaries, this recommendation would
not necessarily encompass the animals
of greatest concern and which we
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assume are the population targeted by
the proposal.
With regard to the timing of the
closure, there is no definitive definition
of the ‘‘peak reproductive activity’’
associated with the stock and,
additionally, there is some uncertainty
as to whether the more important focus
is on effects to pregnant mothers or on
the post-partum period when energetic
or stress effects would lead to greater
risk for lactating mothers and/or
disruption of mother-calf bonding and
ultimate effects on rates of neonate and/
or calf survivorship. We acknowledged
this uncertainty in discussing the
recommendations of NMFS’ subject
matter experts and describing the
proposed temporal extent of February
through May in the notice of proposed
rulemaking. Upon review of the
information presented in the comments
of NRDC (e.g., reference to the data
presented by, e.g., Carmichael et al.,
2012; Mattson et al., 2006; Urian et al.,
1996), which supported NRDC’s
assertion that, in summary, inclusion of
January would cover the remainder of
the dolphins’ peak calving and late
gestation periods as well as the
beginning of the period of highest
reproductive failure, NMFS agrees that
this temporal expansion is appropriate
(within the contracted region of our
revised restriction area). In contrast, the
MMC does not provide compelling
information in support of the
recommendation to expand the
restriction by an additional three
months (through August), stating only
that ‘‘calves can be born at any time of
the year’’ and referencing a bimodal
peak in neonate strandings from the
Sarasota Bay area. Given the
exacerbation of practicability concerns
that this expansion would entail and the
lack of information to support it, NMFS
does not believe it appropriate to
expand the restriction through August.
We do note that one concern of the
Associations, which is that the
restriction may result in an inability to
complete surveys within one year, may
be alleviated to some degree by the
ability under this ITR to issue LOAs for
any term up to five years. The
Associations recommend that, if the
restriction is included in the ITR, NMFS
allow for multi-year LOAs, which we
have done.
Comment: The Associations state that
the proposed time-area restriction in the
Dry Tortugas region of the eastern GOM
should not be required. However, the
MMC concurs with NMFS’ proposal,
stating that the imposition of this
restriction is appropriate.
Response: NMFS appreciates the
comments. The proposed time-area
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restriction referenced here is no longer
relevant following BOEM’s update to
the geographic scope of activity, as no
survey activity within this area can be
considered through this rule.
Comment: NRDC comments that
NMFS must consider restrictions and
limitations on survey activity in the
Central Planning Area (CPA) restriction
area analyzed in the proposed rule.
NRDC states that NMFS’ practicability
analysis must focus on (1) how much oil
and gas development is projected to
occur within the proposed areas over
the next five years; (2) what effect the
proposed mitigation area would have on
that projected development; and (3)
whether that projected development
would be offset by exploration in other
parts of the GOM.
Response: NRDC accurately
characterizes the area as being
important for sperm whales 10 and
beaked whales, as was described by
NMFS in the notice of proposed
rulemaking, and accurately describes
that this area is projected to be subject
to significant survey effort. NMFS
acknowledges these issues. However,
NRDC provides no serious rebuttal of
NMFS’ practicability analysis, which
includes incorporation by reference of
the findings of the RIA for this rule,
instead providing only a cursory
rejection of the analysis as inadequate.
We also note that the third prong of
NRDC’s suggested analysis is not
reasonable: Development foregone due
to a lack of survey data in the closure
areas cannot be ‘‘offset by exploration’’
elsewhere.
As discussed in detail in the RIA,
there are significant uncertainties
associated with assessing the indirect
costs of restricting survey effort within
the described area. Notable areas of
uncertainty include the demand for and
timing of oil and gas production in the
GOM over the next five years, the
suitability of existing data to direct oil
and gas production in the closure areas,
and the most likely substitute sites for
oil and gas production. These
uncertainties foreclose the possibility of
the analysis demanded by NRDC.
However, what information is available
strongly suggests that the economic
impacts of the evaluated CPA
restrictions would be significant. A
mitigation requirement that could lead
10 However, we note that NRDC mischaracterizes
sperm whale buzz rates as ‘‘a measure of foraging
success,’’ as opposed to a measure of foraging effort.
The study referenced by NRDC did not find that
sperm whale foraging success ‘‘declined
substantially’’ on exposure to airgun noise.
Moreover, the measured decline in foraging effort
was not a statistically significant result and,
therefore, cannot appropriately be referred to as a
substantial decline. See Miller et al. (2009).
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to regional- to national-scale economic
impacts is not practicable.
The impacts of year-round area
closures are highly dependent on
volatile oil and gas market conditions
over the next five years, which dictate
the demand for activities in the GOM.
The greater the demand for oil and gas,
the greater the expected impacts of the
restrictions. The extent to which oil and
gas production is delayed because of the
need for newer, better data is a key
source of uncertainty. Some sites may
be able to employ existing data from
recent surveys. However, even for
relatively recent data, the inability to
collect new seismic data could affect oil
and gas development given that oil
companies typically use targeted
seismic data to refine their geologic
analysis before drilling a well.
It is possible that some fraction of
reductions in production from the
closure areas may be made up for with
production in other areas in the GOM,
mitigating potential regional economic
impacts. However, uncertainty with
regard to the location of ‘‘substitute’’
production has potentially critical
impacts on the ultimate economic
impacts of the closure. If a closure
requirement reduces exploration and
development activity in the GOM, the
displaced capital expenditures would
likely shift to the next-lowest-cost
opportunities promising the greatest
development potential. Given that oil is
produced and sold in a global market,
the next-lowest-cost areas may be
elsewhere within the GOM, but also
may be international locations. To the
extent that substitute areas are outside
of the GOM but within the United
States, national-level impacts of the
closure areas would likely be limited.
However, to the extent that industry
moves displaced activities outside of the
United States, national-level impacts
associated with industry income and
employment could be substantial.
Recent levels of leasing and drilling
activity in the CPA indicate that the
closure areas considered are among the
most productive in the entire GOM.11
Given this, it is less likely that other
GOM areas will offer equivalent
alternative opportunities. As a result,
the analyzed area closures have greater
potential to reduce domestic oil and gas
production, industry income, and
11 Leases within the closure areas considered
within the Central Planning Area accounted for
approximately 50 percent of total oil production in
the GOM between 2012 and 2016 and 24 percent
of total gas production. Existing reserves within the
closure areas represent 57 percent of estimated oil
reserves and 37 percent of estimated gas reserves in
the GOM.
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related regional employment
opportunities.
NRDC asks NMFS to conduct analyses
that cannot be supported by existing
data. Further, NRDC asks NMFS to
speculate as to the impacts of restricting
exploration activity outside the
development of existing leases.
However, such a restriction, while less
impactful than a complete area-wide
restriction, would necessarily foreclose
the ability of both the government and
industry to assess fair market value of
leases already planned for sale. While
NMFS believes that the evaluated
restriction area would be beneficial for
sperm whales and beaked whales, such
restrictions are at this time not
practicable. NRDC does not provide any
information contradicting this
conclusion, and provides no specific,
viable alternatives for NMFS’
evaluation.
Comment: NRDC states that NMFS
should consider time-area closures for
additional species.
Response: NMFS did consider habitatbased protections for species additional
to those discussed in the time-area
restrictions section of Mitigation. For all
affected species, NMFS evaluated the
environmental baseline (i.e., other
population-level stressors), the nature
and degree of effects likely to be the
result of the specified activities, and the
information available to support the
development of appropriate time-area
restrictions. NMFS determined that the
available information supported
development of the measures described
in the notice of proposed rulemaking for
the Bryde’s whale, sperm whales, and
beaked whales. For other species,
context does not justify additional
protections and/or the available
information does not support the
designation of any specific area for
protection, when considered in
combination with practicability
concerns.
NRDC asserts that ‘‘marine mammal
populations in the northern Gulf of
Mexico can no longer be considered by
the agency to be too ‘data poor’ or
broadly distributed to justify specific
mitigation measures for their protection,
including time-area closures.’’ This is
not a representation NMFS made in the
notice of proposed rulemaking. NRDC
then erroneously claims that NMFS
‘‘limits its analysis to two deep-diving
species, sperm whales and beaked
whales [. . .]. In doing so, however, it
omitted other populations whose
conservation status or modeled impacts
pose particular concern.’’ First, NMFS
did conduct core abundance analyses
for all GOM stocks. Second, NRDC
declines to elaborate on which stocks
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they believe ‘‘pose particular concern,’’
other than noting that Kogia spp. may be
subject to Level A harassment. However,
despite NRDC’s statement that species
can no longer be considered to be too
broadly distributed to justify specific
time-area mitigation measures, our core
abundance analysis for Kogia spp.
shows exactly that. Based on the Roberts
et al. (2016) models, the two species are
broadly distributed in shelf-break waters
essentially throughout the GOM, and
there is no identified biologically
important area or specific bathymetric
feature that would allow us a more
refined understanding of an area
suitable for protection (if it were
warranted). NRDC does not suggest any
specific area for protection of Kogia spp.
NRDC also suggests that NMFS
should prohibit seismic activity in the
Flower Garden Banks National Marine
Sanctuary (FGBNMS) but offers no
strong justification other than stating
that marine mammals occur there. In
addition, BOEM and/or BSEE will
consult with NOAA’s Office of National
Marine Sanctuaries when they receive
an application that indicates that survey
activity may occur within or near the
FGBNMS.
Overall, NRDC offers no useful
recommendation as to the designation of
protections for additional species.
NMFS’ consideration of habitat-based
protections was conducted
appropriately in light of relevant
information regarding the
environmental baseline, expected effects
of the specified activities, and
information regarding species use of the
GOM.
Comment: Several commenters
recommended establishing wider buffer
zones around the proposed time-area
closures. The Associations state that no
buffers should be required around any
time-area restriction (if required; the
Associations also disagree that any
restrictions should be required, as
discussed previously).
Response: NRDC indicates that
NMFS’ stated objective in establishing
the proposed buffer zones around timearea restrictions was unclear in terms of
evaluating the proposed buffer zone
relative to the objective. The stated
objective was to exclude noise that is
likely to result in harassment, which
NMFS interpreted to mean site-specific
modeled distances to the 160-dB
isopleth (i.e., 50 percent midpoint of the
Level B harassment risk probability
function). Following review of public
comments, NMFS provides further
context here regarding the multi-step
Level B harassment risk function
employed for purposes of evaluating
modeled noise exposures.
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With regard to the establishment of a
buffer zone, NMFS agrees with certain
commenters that it is generally
appropriate to buffer an area to be
avoided by some degree, as discussed in
the notice of proposed rulemaking.
However, we disagree that a buffer must
be developed to fully eliminate the
potential for Level B harassment, as
some commenters may have inferred
from our use of the distance to the 160dB isopleth (i.e., historically used as a
100 percent single-step function for
evaluation of Level B harassment; here
the 50 percent midpoint of the Level B
harassment risk function). Rather, the
buffer concept, as described in the
notice of proposed rulemaking, serves to
reasonably minimize the extent and
severity of what limited harassment may
occur as a result of acoustic exposure to
relatively low received levels of noise.
The Associations asserted that NMFS
did not consider the use of buffer areas
in the practicability analyses and
provides no biological basis for
including buffers. We disagree. As noted
earlier, the RIA analysis (which forms a
substantial part of the practicability
analysis for these measures) includes
analysis of the economic impacts of the
time-area restrictions inclusive of the
buffer. As noted above, the logical
biological rationale is to provide a buffer
around an area determined to be of
particular biological importance such
that the effects of noise from outside the
restriction area intruding within the
area is minimized.
However, BOEM’s update of the
geographic scope for this rule eliminates
the need for proposed time-area
restrictions #3 and 4 (i.e., the Bryde’s
whale core habitat area and the ‘‘Dry
Tortugas area’’ designed for protection
of beaked whales and sperm whales).
Therefore, comments addressing the
proposed buffers for those areas are no
longer relevant. Regarding the coastal
bottlenose dolphin restriction (Area #1),
NMFS has determined that the addition
of a buffer to this area is not warranted,
based on the objectives of the restriction
(described in detail in a previous
response to comment) and on the
manner in which the area was
delineated. Areas #3 and 4 were
delineated based on NMFS’ review of
the available scientific information and
expert opinion and in order to denote
areas expected to be of particular
biological importance for particular
species. In contrast, the coastal dolphin
restriction area was based simply on the
stock boundaries for coastal bottlenose
dolphins (i.e., the seaward extent of the
area is set at the 20-m isobath). As this
boundary does not mark an area of
specific biological importance or high
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density for the stock, but is rather an
approximation of stock presence, NMFS
has determined following review of
public comments, in which valid
practicability concerns were raised, that
the inclusion of a buffer to this area is
not warranted.
Comment: Noting that the proposed
ITR included requirements to conduct
visual monitoring following conclusion
of active shooting, the MMC
recommends that NMFS require
operators to also continue conducting
acoustic monitoring following
conclusion of active shooting.
Response: The proposed ITR stated
that acoustic monitoring must occur for
30 minutes prior to and during all active
firing of airguns for deep penetration
surveys, but was silent on the issue of
acoustic monitoring following the
survey. However, visual monitoring is
required to continue for 60 minutes
following cessation of survey activity
during good visibility. NMFS agrees
with the MMC that ‘‘both visual and
acoustic monitoring should occur
concurrently, as acoustic detections can
provide additional information not
readily available via visual detections
alone regarding changes in foraging and
social behavior during survey activities
and after activities cease.’’ Accordingly,
acoustic monitoring is also required to
continue following cessation of survey
activity for a period of 60 minutes.
Comment: BP comments that they
welcome use of industry standard PAM/
operator software such as PAMGuard.
Noting the operational challenges
associated with accommodating
increased numbers of PSOs on survey
vessels, BP also comments that they
would welcome the inclusion of an
option to implement PAM during
survey activities using remote shorebased operators.
Response: NMFS agrees that this may
be appropriate, depending on various
factors. While we are not currently
aware of the state of existing technology
towards achieving this end, NMFS
would consider the use of remote PAM
monitoring, assuming reliability and the
ability to achieve the same performance
as shipboard PAM monitoring. NMFS
believes the adaptive management
process will be an appropriate venue for
further consideration of this approach.
Comment: BP comments that, while
they recognize the value of prospective
formal standards for PAM operations
(e.g., hardware, software, training), the
standards have not yet been finalized.
BP requests that the standards be
considered for use only after an initial
draft has been circulated via relevant
standards development and issuance
processes.
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Response: NMFS may adopt elements
of the prospective standards, as it deems
appropriate (as discussed in Monitoring
and Reporting). However, we agree that
wholesale adoption of the standards
would not be appropriate until
appropriate review and other necessary
processes are complete.
Comment: Industry commenters state
that non-airgun high-resolution
geophysical (HRG) surveys should not
be subject to pre-clearance and
shutdown requirements. Relatedly, BP
and Chevron comment that exclusion
zones should not be required for HRG
surveys, as these surveys typically
operate using acoustic sources deployed
on an automated underwater vehicle
(AUV) running 40 m above the seafloor.
Therefore, they state that there is no
environmental benefit to a requirement
for a surface exclusion zone.
Response: The Associations note that
the acoustic footprint of sources
typically used in non-airgun HRG
surveys are too small to warrant the
proposed exclusion and buffer zone
distances and that, more importantly,
due to the typically highly directional
nature of these acoustic sources,
animals observed at the surface will
generally not be exposed to the signal.
NMFS agrees with these comments, and
notes that the proposed shutdown and
exclusion zone requirements were
offered in accordance with BOEM’s
HRG survey protocols (Appendix B of
BOEM, 2017). Following review of these
comments, as well as the available
scientific information regarding the
typical interaction of these signals with
the environment and likely lack of
efficacy of typical standard operational
protocols developed for omnidirectional
sources, NMFS has eliminated these
requirements. However, we also clarify
that certain electromechanical sources
may be subject to the pre-clearance and
shutdown requirements associated with
shallow penetration surveys. In
addition, the exclusion and buffer zone
distances for shallow penetration
surveys have been reduced (while
adding an extended distance shutdown
zone for certain circumstances) in
recognition of the typically smaller
harassment zones associated with use of
the acoustic sources considered here to
be used in shallow penetration surveys.
As noted here, NMFS has eliminated
the requirement for implementation of
an exclusion zone during HRG surveys.
We also agree with BP’s comment that
exclusion zones should not be required
for surveys using an AUV-deployed
acoustic source running at short
distances above the seafloor.
Comment: NRDC states that NMFS
fails to prescribe adequate mitigation for
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HRG surveys and, relatedly, that NMFS
must not issue LOAs for use of lowerfrequency multibeam echosounders
(MBES).
Response: As evidenced by the
previous comment response, in which
describing elimination of certain
mitigation measures that were proposed
for HRG surveys, NMFS disagrees with
NRDC. NRDC provides no reasonable
justification for the recommendation to
consider additional mitigation
requirements. They reference the 2008
Madagascar stranding of melon-headed
whales, implying that a similar
occurrence may be a reasonably
anticipated outcome of HRG survey
work in the GOM. Although it is correct
that an investigation of the event
indicated that use of a high-frequency
mapping system (12-kHz MBES) was the
most plausible and likely initial
behavioral trigger of the event (with the
caveat that there was no unequivocal
and easily identifiable single cause), the
panel also noted several site- and
situation-specific secondary factors that
may have contributed to the avoidance
responses that led to the eventual
entrapment and mortality of the whales
(Southall et al., 2013). Specifically,
regarding survey patterns prior to the
event and in relation to bathymetry, the
vessel transited in a north-south
direction on the shelf break parallel to
the shore, ensonifying deep-water
habitat prior to operating intermittently
in a concentrated area offshore from the
stranding site. This may have trapped
the animals between the sound source
and the shore, thus driving them
towards the lagoon system. Shorewarddirected surface currents and elevated
chlorophyll levels in the area preceding
the event may also have played a role.
The relatively lower output
frequency, higher output power, and
complex nature of the system
implicated in this event, in context of
the other factors noted here, likely
produced a fairly unusual set of
circumstances that indicate that such
events would likely remain rare and are
not necessarily relevant to use of more
commonly used lower-power, higherfrequency systems such as those
evaluated for this analysis. The risk of
similar events recurring is expected to
be very low, given the extensive use of
active acoustic systems used for
scientific and navigational purposes
worldwide on a daily basis and the lack
of direct evidence of such responses
previously reported. The only report of
a stranding that may be associated with
this type of sound source is the one
reported in Madagascar.
NRDC also references Cholewiak et al.
(2017), stating that virtually no beaked
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whale vocalizations were detected
acoustically during the time that the
shipboard echosounder was operational.
NRDC mischaracterizes the literature,
including a speculative description of
what they imagine the beaked whales
were doing while not vocalizing
(‘‘suggesting that the whales broke off
their foraging behavior and engaged in
[. . .] silent flight’’). Cholewiak et al.
(2017) do describe finding that beaked
whales were significantly less likely to
be detected acoustically while
echosounders were active. However, it
is not clear that this response should be
considered as Level B harassment when
considered in the context of what is
likely a brief, transient effect, given the
mobile nature of the surveys and the
fact that some beaked whale
populations are known to have high site
fidelity. In support of this conclusion,
Quick et al. (2017) describe an
experimental approach to assess
potential changes in short-finned pilot
whale behavior during exposure to an
echosounder. Tags attached to the
animals recorded both received levels of
noise as well as orientation of the
animal. Results did not show an overt
response to the echosounder or a change
to foraging behavior of tagged whales,
but the whales did increase heading
variance during exposure. The authors
suggest that this response was not a
directed avoidance response but was
more likely a vigilance response, with
animals maintaining awareness of the
location of the echosounder through
increased changes in heading variance
(Quick et al., 2017). Visual observations
of behavior did not indicate any
dramatic response, unusual behaviors,
or changes in heading, and cessation of
biologically important behavior such as
feeding was not observed. More
recently, Varghese et al. (2020) reported
the results of an investigation of the
effects of a 12-kHz MBES system on
beaked whale foraging behavior off of
California. Echolocation clicks from
Cuvier’s beaked whales were detected
and classified into foraging events
called group vocal periods (GVP), and
compared across exposure periods
before, during, and after MBES activity.
Of the metrics used to assess beaked
whale foraging behavior, only the
number of GVPs per hour was
statistically different during MBES
activity versus a non-MBES period.
GVPs per hour increased during MBES
activity compared with before MBES
activity, demonstrating that beaked
whales did not stop foraging and were
not displaced by the activity. These
results suggest that there was not a
negative impact of MBES activity on
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foraging behavior of this sensitive
species (Varghese et al., 2020).
Finally, NRDC references the work of
Deng et al. (2014) and Hastie et al.
(2014) in describing ‘‘leakage’’ of
‘‘substantial noise’’ at frequencies
within marine mammal hearing range
during use of active acoustic systems
that are operated at higher frequencies.
The referenced studies reported some
behavioral reaction by marine mammals
to acoustic systems operating at userselected frequencies above 200 kHz.
This work was discussed in the notice
of proposed rulemaking. In general, the
referenced literature indicates only that
sub-harmonics could be detectable by
certain species at distances up to several
hundred meters. As NMFS has noted
elsewhere, behavioral response to a
stimulus does not necessarily indicate
that Level B harassment, as defined by
the MMPA, has occurred. Source levels
of the secondary peaks considered in
these studies—those within the hearing
range of some marine mammals—mean
that these sub-harmonics would either
be below the threshold for Level B
harassment or would attenuate to such
a level within a few meters. The work
cited by the commenters is consistent
with previously observed occurrences of
sub-harmonics. Essentially, the first subharmonic’s source level (e.g., if the
primary frequency is 200 kHz, the first
sub-harmonic is 200/2 or 100 kHz, the
second is 200/3 or 66.7 kHz) is at least
20–30 dB less than the primary
frequency’s source level, with each
subsequent sub-harmonic’s source level
decreasing rapidly from there. These
sub-harmonics are typically so reduced
in source level that, for most side-scan
and multi-beam sonar systems, they are
not strong enough to produce impacts
beyond tens of meters from the source
(distances at which reactions to the
vessel itself are likely to supersede
reactions to an acoustic signal).
Additionally, for any potential impacts
to occur, an animal must be within this
range and within the very narrow beams
produced by the systems (for these subharmonic frequencies).
In addition, recent sound source
verification testing of these and other
similar systems did not observe any subharmonics in any of the systems tested
under controlled conditions (Crocker
and Fratantonio, 2016). While this can
occur during actual operations, the
phenomenon may be the result of issues
with the system or its installation on a
vessel rather than an issue that is
inherent to the output of the system. As
concluded in the notice of proposed
rulemaking, there is no evidence to
suggest that Level B harassment of
marine mammals should be expected in
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relation to use of active acoustic sources
at frequencies exceeding 180 kHz.
NRDC’s comments did not address
NMFS’ prior statements regarding this
topic.
NRDC fails to adequately support the
claims of harm to marine mammals that
are reasonably likely to occur as a result
of HRG surveys and, thus, fails to justify
their recommendation for enhanced
mitigation. The recommended measures
include ‘‘extended safety zone and
monitoring requirements’’ and a ‘‘bar on
nighttime operations.’’ Even when
animals are receiving echosounder
signals, they may not be harassed, as
described above. However, given the
directional nature of these sources,
animals observed at the surface will
almost certainly not be within the
acoustic beam, thus negating the benefit
of detection-based measures such as
shutdowns. Any exposure to the
echosounder would likely be only in the
ensonified cone below the vessel, and
responses to the vessel itself at such
close ranges would influence likelihood
of acoustic exposure. The package of
active acoustic systems modeled as
representative of a typical HRG survey
included a 200-kHz echosounder.
Regarding the suggestion that this bars
use of any system with a lower
frequency output, NMFS disagrees.
NMFS’ analysis also includes use of
different lower-frequency sources (i.e.,
single airguns and boomers). Moreover,
the specific sources selected for analysis
do not limit the actual sources that may
be used, assuming the actual sources are
reasonably similar to the full suite of
analyzed sources, as is the case here.
Comment: The Associations and other
industry commenters claim that the
proposed PSO staffing requirements
compromise personnel safety, cannot be
effectively implemented, and are
unnecessary and unsupported.
Response: In the notice of proposed
rulemaking, NMFS described in detail
the importance of detection-based
mitigation as a component of standard
operational mitigation protocols.
Detection-based mitigation cannot occur
effectively without both visual and
acoustic monitoring, with the latter
being the only effective method of
detection during periods of poor
visibility or at any time for cryptic
species (e.g., beaked whales) or species
with high availability bias (e.g., sperm
whales). Therefore, visual monitoring is
required during daylight hours and
acoustic monitoring is required
throughout the period of survey
operations. When these monitoring
techniques are required, two visual
PSOs must be on duty in order to
effectively monitor 360 degrees around
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the vessel, communicate with the
operator as necessary, and record data,
and an acoustic PSO must be on duty to
monitor the PAM system. In order to
effectively carry out monitoring duties,
PSOs must have sufficient periods of
rest to minimize fatigue that would
compromise their performance. Based
on these considerations, and in
consideration of the literature relating to
mitigation and monitoring requirements
and standard practice for scientific
surveys, NMFS proposed minimum
duty requirements.
While NMFS agrees that there is
likely to be some increased logistical
burden associated with these
requirements, which are expanded to
some degree from current practice in the
GOM in the absence of compliance with
the MMPA, the Associations do not
demonstrate that this burden is so large
as to be impracticable. Similarly, they
do not provide information supporting
claims that these requirements would
compromise personnel safety (and
certainly do not support the claim that
the requirements are ‘‘unnecessary and
unsupported’’). The Associations’
comment states that survey vessels are
typically at maximum capacity. NMFS
acknowledges that in some cases,
increased PSO staffing may result in a
need for operators to balance staffing in
other areas, such as in the seismic crew
(25 to 30) or the three to seven client
representatives that the Associations
state are typically aboard a survey
vessel, in order to accommodate
necessary PSO staffing while not
exceeding a vessel’s maximum capacity.
However, assuming that a vessel’s
maximum capacity is not exceeded, the
claim that increasing the number of
people aboard necessarily increases ‘‘the
risk of injuries, illnesses, and
evacuation for medical reasons’’ is
unsupported. The comment is
inconsistent regarding the number of
PSO staff that the requirements would
add, at various places stating that the
requirements would result in the
addition of six to eight or three to five
PSO staff. Overall, the Associations state
that only three (and possibly up to four)
PSOs should be allowed, without
explaining how this may achieve the
objective of the proposed detectionbased mitigation requirements.
However, in recognition of the likely
increase in logistical burden and the
possibility that individual LOA
applicants may be able to demonstrate
legitimate practicability issues, NMFS
allows for the potential that an
exception may be obtained specifically
for the requirement that PSOs may be on
duty for a maximum period of two
hours, followed by a minimum period of
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one hour off. If an exception is granted
based on practicability, the historical
practice of a maximum on-duty period
of four hours, followed by a minimum
period of two hours off, would be
substituted.
Comment: The Associations and other
industry commenters comment that the
proposed requirement for visual
observation before and during nighttime
ramp-ups would be ineffective and
potentially present safety concerns.
Response: NMFS agrees that reduced
efficacy should be expected for visual
monitoring at night and, in
consideration of comments asserting
that this may present a safety concern,
we have eliminated this requirement
(noting that passive acoustic monitoring
is still required for all nighttime
operations of large airgun arrays). NMFS
also agrees with the Associations’
comment that employment of a PSO for
the dedicated purpose of documenting
entanglements with ocean-bottom node
(OBN) cables is unnecessary and has
eliminated this requirement.
Elimination of these requirements is
expected to help somewhat in
alleviating the logistical concerns
expressed by the Associations.
Comment: The Associations suggest
that entanglement avoidance
requirements should be removed from
the ITR. The MMC comments that they
support these requirements, and that the
requirements are consistent with best
management practices developed for
avoiding entanglements.
Response: The Associations’
comment, offered only in a footnote, is
unclear as to whether the Associations’
suggestion is to remove all entanglement
avoidance requirements or only the
requirement to use negatively buoyant
coated wire-core tether cable. (Note that
NMFS does agree with the suggested
elimination of a requirement for use of
a dedicated PSO for purposes of
documenting entanglement.) Regardless,
the Associations’ suggestion that this
requirement should be removed is
keyed only to concern regarding
practicability. NMFS disagrees that this
requirement is impracticable, and the
Associations offer no information to the
contrary. Moreover, this measure is
designed to prevent serious injury or
mortality, which cannot be authorized
under this rule.
Here, no mortality was requested or
proposed for authorization and,
therefore, potential for death by
entanglement must be avoided. There is
demonstrated potential for
entanglement of protected species in
association with OBN survey
operations. As described in the notice of
proposed rulemaking, a GOM OBN
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operator remarkably entangled three
different protected species within a
year—including an Atlantic spotted
dolphin, as well as an ESA-listed turtle
and a manta ray. BSEE subsequently
issued two enforcement actions against
the operator for incidents of noncompliance, indicating that it is
appropriate to be stringent regarding
requirements relating to entanglement
avoidance. Specific appropriate
measures were determined in
consultation between NMFS, BOEM,
and BSEE, including consultation with
NMFS’ gear engineering experts, and
were subsequently included in permits
issued by BOEM (e.g., OCS Permit L17–
009, issued July 11, 2017). NMFS
proposed these specific measures for
this ITR and no comments offering
useful suggestions regarding potential
modifications to the measures were
received. A generic suggestion that no
entanglement avoidance requirements
are necessary is not credible.
Comment: NRDC claims that NMFS
fails to consider mitigation to reduce
ship strike, particularly within Bryde’s
whale habitat. Separately, NRDC states
that NMFS should consider extending
ship-speed requirements to all project
vessels. The Associations state that
vessel strike avoidance measures should
not be required, or that there should be
modifications and/or exemptions to the
measures.
Response: NMFS disagrees with
NRDC’s contention. NMFS’ required
vessel strike avoidance protocol is
expected to further minimize any
potential interactions between marine
mammals and survey vessels, relative to
the already low likelihood of vessel
strike in relation to the activities
considered herein. Please see ‘‘Vessel
Strike Avoidance’’ for a full description
of requirements, which include: Vessel
operators and crews must maintain a
vigilant watch for all marine mammals
and must take necessary actions to
avoid striking a marine mammal; vessels
must reduce speeds to 10 kn or less
when mother/calf pairs, pods, or large
assemblages of cetaceans are observed
near a vessel; and vessels must maintain
minimum separation distances.
We also note that NRDC’s comment
that ‘‘vessels supporting the seismic
operation are not similarly constrained’’
is in error. All project vessels are
required to adhere to vessel strike
avoidance requirements, including
speed requirements in certain
circumstances. As stated clearly in the
proposed and final regulatory text,
‘‘[v]essel operators and crews must
maintain a vigilant watch for all marine
mammals and slow down or stop their
vessel or alter course, as appropriate
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and regardless of vessel size, to avoid
striking any marine mammal [. . .].’’
Regarding whether ship speed
requirements are warranted for all
project vessels in the Bryde’s whale core
habitat area to minimize risk of strike
for Bryde’s whales, the consideration is
no longer relevant to this rule, as
activity within the Bryde’s whale core
habitat area referenced by NRDC can no
longer be considered through this rule
following BOEM’s update to the scope
of action. Further, we disagree that
similar risk exists for sperm whales and
beaked whales, as would be necessary to
warrant vessel speed restrictions in the
Mississippi Canyon area. There are very
few records of vessel strikes for sperm
whales, as compared with mysticete
whales in general, and Bryde’s whales’
dive behavior in particular makes them
potentially more susceptible to vessel
strike.
The Associations’ comments state that
they are not aware of any incidence of
ship strike associated with a
geophysical survey, implying that no
strike avoidance measures are
necessary. The lack of recorded
incidents of strike does not mean that
none have occurred and, more
importantly, does not mean that none
will occur. Therefore, it is NMFS’
responsibility to prescribe measures that
will achieve the least practicable
adverse impact via avoidance of vessel
strike. The comments go on to assert
that there is ‘‘no evidence’’ that strike
avoidance measures benefit marine
mammals, despite the wealth of
scientific evidence described in the
notice of proposed rulemaking that
slower vessel speeds result in fewer
strikes and, if a strike does occur, a
significantly lower likelihood of
mortality. Separation requirements are
common sense—a moving vessel should
maintain some minimum distance from
a whale to avoid striking it—and are
similar to generic strike avoidance
guidelines found elsewhere. The
comments implying that these
requirements are unwarranted and
burdensome are unpersuasive,
particularly given that BOEM has
required essentially identical strike
avoidance measures in the GOM via
notices to lessees for many years
(currently, via BOEM NTL No. 2016–
G01).
Nevertheless, NMFS recognizes that
there are legitimate concerns regarding
vessels towing gear and human safety
issues. We have clarified in the strike
avoidance measures that vessel strike
avoidance requirements do not apply in
any case where compliance would
create an imminent and serious threat to
a person or vessel or to the extent that
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a vessel is restricted in its ability to
maneuver and, because of the
restriction, cannot comply.
Comment: The Associations and other
industry commenters raise concerns
regarding the PSO requirements,
including that NMFS’ requirements for
PSOs will result in labor shortages, and
make an accompanying
recommendation that these be
‘‘preferred’’ training requirements that
LOA-holders would not have to meet.
Response: NMFS disagrees with the
comments. The Associations’ statement
that requirements for PSOs to have
bachelor’s degrees or to satisfy a
positive experience requirement are
‘‘difficult, if not impossible, to achieve’’
is not persuasive. As explained in the
notice of proposed rulemaking, NMFS
discussed these PSO requirements with
BSEE and with third-party observer
providers. Both parties indicated that
the requirements should not be
expected to result in any labor shortage.
We pointed out that during a period
when a significantly greater amount of
survey activity was occurring in the
GOM than at present (i.e., with as many
as 30 source vessels), requirements
similar to those proposed did not result
in any labor shortage. Moreover, NMFS
specifically requested comment on the
assumption that the requirements would
not result in any labor shortage. The
Associations’ expressed concern
regarding the potential for a labor
shortage, but do not provide any
specific information to support the
claims. We also clarify that not all PSOs
must have a minimum of 90 days at-sea
experience, with no more than 18
months elapsed since the conclusion of
the most recent relevant experience. As
described in the notice of proposed
rulemaking and herein, a minimum of
one visual PSO and two acoustic PSOs
must have such experience (rather than
all PSOs).
Comment: The Associations provide a
list of specific proposed monitoring and
reporting requirements that they assert
are unreasonable or otherwise
problematic. Some of these comments
are echoed by other industry
commenters.
Response: We address the specific
issues raised by the Associations in
turn.
1. The Associations state that bigeye
binoculars should not be required,
because they are expensive, require
installation on the vessel, and are not
appropriate for monitoring of the
exclusion zone.
NMFS disagrees with this comment.
While it is correct that procurement of
bigeye binoculars will incur costs, these
costs were analyzed in NMFS’ RIA.
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While bigeye binoculars may not be an
individual PSO’s tool of choice for
observing marine mammals at close
range to the vessel, they are an
indispensable tool for observing marine
mammals at greater distance upon
initial detection, are a standard
component of marine mammal
observation (for scientific purposes, but
also as a part of standard mitigation
monitoring conducted aboard surveys
for which incidental take authorizations
are issued), and will be helpful in more
accurately identifying animals at greater
distances, such that the precautionary
shutdowns of concern to the
Associations are avoided.
2. The Associations state that PSOs
should not report on factors that may be
contributing to impaired observations,
as such reporting may be speculative,
unverifiable, and/or incorrect.
NMFS disagrees with this comment.
Reporting on such conditions is not
connected to any requirement for action,
but it is important to understand
whether visual observation is able to be
conducted in an effective fashion,
whether it be due to weather conditions
or to conditions on the vessel.
3. The Associations suggest that the
reporting requirement to estimate
numbers of animals observed by cohort
is overly complicated, and that the rule
should require only recording of
juveniles and adults.
NMFS agrees with this comment and
has made corresponding edits to the
regulatory text.
4. The Associations express some
confusion regarding language
addressing the information that visual
PSOs should be compiling on a daily
basis and whether these daily ‘‘reports’’
include estimates of actual animals
taken.
NMFS clarifies that the language cited
by the Associations was not intended to
mean that PSOs should be estimating
‘‘takes’’ on a daily basis, and confirm
that the Associations’ statement that
such information should be included
only in annual reporting is correct.
5. Regarding NMFS’ consideration of
an approach recommended by the MMC
to produce estimates of actual take from
observations of animals during survey
effort, the Associations express concern
about the appropriate application of this
process, and suggest that the protocol be
applied at the end of a period long
enough to accumulate sufficient data to
adequately evaluate the appropriateness
and proper application of the process as
part of the adaptive management
process.
NMFS shares many of the
Associations’ concerns on this subject
and regarding the specific methodology
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proposed by the MMC. NMFS looks
forward to working with the
Associations (as well as BOEM and
BSEE) towards the development of
appropriate methods through the
adaptive management process.
6. In reference to the requirement for
the lead PSO to submit to NMFS a
statement concerning mitigation and
monitoring implementation and
effectiveness, CGG adds that, because
there is a lead PSO on each offshore
rotation, the LOA-holder should submit
collated statements.
NMFS agrees that this may be a more
practical approach.
Comment: The MMC recommends
that NMFS require LOA-holders to
implement electronic reporting systems
for field-based PSO data entry and
expedited reporting.
Response: NMFS agrees that this
would be appropriate and would better
ensure expedited field entry and quality
control checking of PSO data, as well as
facilitate data transfer, quality control,
data analysis, and automated report
generation. Overall, such a requirement
is helpful to ensure the efficient
synthesis of data, as required by the
comprehensive reporting process.
Comment: The Associations express
support for NMFS’ proposed approach
to comprehensive monitoring and
development of a structured adaptive
management process, and highlight
their support for efforts that improve the
quantity and quality of information
related to determining the nature and
magnitude of the potential effects of
offshore geophysical activities on
marine mammals, including industrysupported independent third-party
research.
Response: NMFS appreciates the
comments and looks forward to
continued engagement with the
regulated community, as well as BOEM
and BSEE, to improve the collection and
use of the best available science
consistent with the requirements and
limits of the MMPA.
Comment: The MMC comments that
they support an annual adaptive
management process for the issuance of
LOAs in the GOM and recommend that
they be included in the process along
with representatives from BOEM, BSEE,
and industry.
Response: NMFS appreciates the
comments and will ensure that the
adaptive management process includes
participation of the parties noted, where
appropriate.
Comment: NRDC asserts that NMFS
fails to prescribe requirements sufficient
to monitor and report takings of marine
mammals. The MMC recommends that
NMFS and BOEM work together to
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develop a coordinated long-term
monitoring and research plan, and
further recommends that, to facilitate
the completion of the plan, NMFS and
BOEM establish a GOM scientific
advisory group, composed of agency
and industry representatives and
independent scientists, to assist in the
identification and prioritization of
monitoring needs and hypothesis-driven
research projects to better understand
the short- and long-term effects of
geophysical surveys on marine
mammals in the GOM. Commenters also
noted that there are many research gaps
that need to be filled and suggested that
NMFS should include monitoring
requirements that fill those gaps.
Response: Section 101(a)(5)(A) of the
MMPA indicates that any regulations
NMFS issues shall include
‘‘requirements pertaining to the
monitoring and reporting of such
taking.’’ This broad requirement allows
for a high degree of flexibility in what
NMFS may accept or include as a
monitoring requirement, but is not
specific in identifying a threshold of
what should be considered adequate
monitoring. Contrary to NRDC’s
comments, except for IHAs in Arctic
waters, NMFS’ implementing
regulations do not provide a specific
standard regarding what required
monitoring and reporting measures
‘‘must’’ accomplish. However, NMFS’
implementing regulations require
incidental take applications to include
suggested means of accomplishing the
necessary monitoring and reporting that
will result in increased knowledge of
the species, the level of taking, or
impacts on populations of marine
mammals that are expected to be
present while conducting activities, as
well as suggested means of minimizing
burdens by coordinating such reporting
requirements with other schemes
already applicable to persons
conducting such activity. 50 CFR
216.104(a)(13). The comment extracts
pieces of this language to suggest that
future LOA applicants are required to
coordinate with each other’s monitoring
efforts, ignoring the fact that the
relevant regulation points to this
coordination only in support of
minimizing the burden on the applicant
and that it refers to coordination with
‘‘schemes already applicable to persons
conducting such activity.’’ 50 CFR
216.104(a)(13). NRDC attempts to
further the argument that coordination
across projects is required by statute by
referencing a monitoring plan that they
state is in development by BOEM. The
MMC also references development of a
‘‘long-term monitoring plan’’ that they
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attribute to BOEM. NMFS is not aware
that any such monitoring plan has been
developed and, therefore, such a plan is
not ‘‘already applicable to persons
conducting such activity.’’
NRDC discusses a litigation
settlement agreement related to the
activities that are the subject of this rule,
stating that ‘‘BOEM must analyze ‘the
development of a long-term adaptive
monitoring plan that addresse[s]
cumulative and chronic impacts from
seismic surveys on marine mammal
populations in the Gulf of Mexico.’ ’’
NRDC et al. v. Bernhardt et al., 2:10–cv–
1882, ECF No. 118 (E.D. La. June 18,
2013). NRDC also cites BOEM’s PEIS in
discussing this plan. That requirement
in the settlement agreement does not
pertain to NMFS’ statutory authority
under the MMPA, which does not
provide authority for NMFS to require
the development of a ‘‘long-term
monitoring plan’’ via the promulgation
of ITRs or as a condition of an
incidental take authorization. As noted
above, NMFS’ statutory authority is to
prescribe ‘‘requirements pertaining to
the monitoring and reporting of such
taking.’’ Although applicants that
anticipate the need for consecutive
periods of five-year regulations to cover
ongoing activities may develop
monitoring and reporting plans that
extend past the five-year effectiveness
period of a rule, section 101(a)(5)(A)
requires only monitoring and reporting
to cover the specified activities
undertaken during the period of the
rule. Were a long-term monitoring plan
to be developed by BOEM, it would
therefore be a voluntary undertaking on
the part of participants, rather than a
requirement under the MMPA. While
certainly an exemplar of what a strong
comprehensive monitoring plan can
look like, the U.S. Navy’s Integrated
Comprehensive Monitoring Program
(ICMP), which NRDC references as a
relevant analogue to the monitoring
plan that they assert is required in the
GOM to satisfy the requirements of the
MMPA, should not be hailed as a model
that should always be copied or a
standard that must be achieved for all
MMPA ITRs. The Navy’s ICMP was
developed in close coordination with
NMFS and reflects several factors that
are not present for all ITRs (including
these regulations) and that lay the
groundwork for what is an exceptionally
comprehensive program. Specifically, as
the single entity for which take is
authorized and that has the
responsibility for implementing a
monitoring program, the Navy has an
existing organizational and funding
structure that can support a truly
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integrated and comprehensive plan that
would be far more difficult under a rule
allowing for authorization of take by
disparate applicants with varying
activity levels, resource availability, and
familiarity with regulatory requirements
and marine mammal issues. Also, the
Navy has an independent
environmental stewardship mandate
that influences their monitoring
approach and supports a robust program
intended to work in concert with the
work funded through their Office of
Naval Research and Living Marine
Resources programs to create essentially
full coverage of the science necessary to
support vigorous environmental
assessment and compliance across all
Navy actions. Last, Navy training and
testing utilize a large variety and
number of platforms and sound sources,
many of which can result in the take of
marine mammals but cannot be
monitored at the source. Accordingly,
the Navy employs the robust, problembased, often off-site monitoring program
currently in place in order to answer
targeted questions with controlled
studies.
Although NMFS’ authority with
regard to the prescription of monitoring
requirements does not include
mandating long term monitoring, the
MMPA does require an assessment of
impacts from the total taking by all
persons conducting the activity. Thus,
meaningful monitoring and reporting for
a specified activity under section
101(a)(5)(A) should be designed to help
us better understand the total taking that
is considered for authorization under
the regulations for all persons
conducting the specified activities
under the five-year regulations. This
necessitates coordination across
applicants with regard to
comprehensive analysis and reporting of
information collected in relation to ‘‘the
level of taking or impacts on
populations of marine mammals that are
expected to be present while conducting
activities.’’ 50 CFR 216.104(a)(13). We
discuss these comprehensive reporting
requirements in greater detail in
Monitoring and Reporting. These
requirements are appropriate to the
necessary function of informing the
assessment of the overall impact of the
incidental take allowable under the
regulations and acknowledge the need
to conduct aggregation and analysis of
the data in a manner that directly
informs the question of whether and the
degree to which marine mammal
populations addressed may be affected
by the incidental take authorized by
LOAs.
We appreciate the MMC’s
acknowledgement of the investments
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5381
made by BOEM and industry (via the
E&P Sound and Marine Life Joint
Industry Program) towards better
understanding of marine mammal
abundance and distribution, the
characterization of anthropogenic sound
sources in the GOM, and the effects of
sound on marine mammal hearing and
behavior, among other initiatives. We
also note that much of the research
recommended by NRDC has been
conducted via the BOEM-sponsored
Gulf of Mexico Marine Assessment
Program for Protected Species initiative.
However, while these voluntary efforts
are commendable, section 101(a)(5)(A)
does not require hypothesis-driven,
focused research pertaining to the
impact and mitigation of chronic noise
exposure on populations of special
concern, nor does it require a
‘‘coordinated long-term monitoring and
research plan,’’ as expressed by the
commenters.
Regarding the MMC’s
recommendation that NMFS establish a
GOM ‘‘scientific advisory group,
composed of agency and industry
representatives and independent
scientists, to assist in the identification
and prioritization of monitoring needs
and hypothesis-driven research
projects,’’ NMFS would be willing to
explore with the MMC the appropriate
mechanisms for convening such a
group, including consideration of the
MMC’s authorities under the MMPA.
The monitoring approach described in
this preamble includes LOA-specific
monitoring and reporting set forth in the
regulations and, separately, outlines a
framework for potential data collection,
analysis, research, or collaborative
efforts that are not specified in these
regulations but which work towards
satisfying the information elements
identified in our implementing
regulations. NMFS is committed to
working with industry and BOEM
through the adaptive management
process to ensure that LOA-specific
monitoring and reporting will be used
appropriately to help better understand
the impacts of the total taking from the
specified activity contemplated in this
ITR on the affected populations, as well
as how the more overarching voluntary
efforts will be identified and carried out.
Comment: The Associations reiterate
their belief that NMFS, as the regulating
agency, has the responsibility to collect,
organize, and assess all of the data
reported to NMFS under the terms of
issued LOAs.
Response: NMFS disagrees with this
comment. The MMPA requires NMFS to
prescribe regulations setting forth
requirements pertaining to the
monitoring and reporting of ‘‘such
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taking.’’ 16 U.S.C.
1371(a)(5)(A)(i)(II)(bb). (In contrast, the
other required component of activityspecific regulations, relating to
mitigation requirements, refers to
‘‘taking pursuant to such activity.’’ 16
U.S.C. 1371(a)(5)(A)(i)(II)(aa). In NMFS’
view, these monitoring and reporting
requirements in our activity-specific
regulations refer to the total taking from
the specified activity as a whole, and
they are requirements that can be
imposed on those entities availing
themselves of LOAs issued under the
activity specific regulations. Therefore,
it is incumbent upon LOA-holders,
collectively, to provide this information
to NMFS in a reasonably synthesized
form such that NMFS may adequately
assess the effects of the specified
activity on an ongoing basis. This
information may in some cases be
essential to NMFS’ ability to carry out
50 CFR 216.105(e) (‘‘Letters of
Authorization shall be withdrawn or
suspended, either on an individual or
class basis, as appropriate, if, after
notice and opportunity for public
comment, the Assistant Administrator
determines that: (1) The regulations
prescribed are not being substantially
complied with; or (2) The taking
allowed is having, or may have, more
than a negligible impact on the species
or stock or, where relevant, an
unmitigable adverse impact on the
availability of the species or stock for
subsistence uses’’ (emphasis added).)
While NMFS recognizes that the
Associations are not subject to the ITR
(including any reporting requirements
in the ITR or related LOAs), LOAholders (many of which are likely to be
Association members) will collectively
be responsible for the comprehensive
reporting requirements described
herein. The Associations in their
comment commit to participate in the
annual assessment process, and NMFS
welcomes that participation.
Comment: The MMC recommends
that NMFS require industry operators to
measure and report the horizontal
leakage of their various airgun arrays
and investigate options to minimize
horizontal sound leakage from those
array configurations.
Response: As stated in the notice of
proposed rulemaking, NMFS encourages
the minimization of unnecessary
horizontal propagation. However, while
the MMC’s recommendation would
likely lead to a better understanding of
actual horizontal propagation (or
‘‘leakage’’) that does occur, it is not clear
that the product of such measurements
(termed ‘‘waste ratios’’ by the MMC)
would necessarily lead to a viable path
to reducing such leakage. In addition,
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the MMC does not specify what it
recommends as a sufficient amount of
data concerning waste ratios to allow
consideration of a potential threshold.
Thus, the comment implies that all
operators would be required to conduct
field measurements of the acoustic
output of airgun arrays under this
recommendation, which NMFS believes
would not be practicable. NMFS
appreciates the comment and will
further consider the utility of the
recommendation, and methods of
implementation, through the adaptive
management process.
We do note that BOEM currently
requires operators to confirm through
the permitting process that the airgun
arrays used have been calibrated or
tuned to maximize subsurface
illumination and to minimize, to the
extent practicable, horizontal
propagation of noise.
Comment: NRDC suggests that NMFS
should consider requiring use of
thermal detection as a supplement to
visual monitoring.
Response: NMFS appreciates the
suggestion and agrees that relatively
new thermal detection platforms have
shown promising results. Following
review of NRDC’s letter, we considered
these and other supplemental platforms
as suggested. However, to our
knowledge, there is no clear guidance
available for operators regarding
characteristics of effective systems, and
the detection systems cited by NRDC are
typically extremely expensive, and are
therefore considered impracticable for
use in most surveys. For example, one
system cited by NRDC (Zitterbart et al.,
2013)—a spinning infrared camera and
an algorithm that detects whale blows
on the basis of their thermal signature—
was tested through funding provided by
the German government and, according
to the author at a 2015 workshop
concerning mitigation and monitoring
for seismic surveys, the system costs
hundreds of thousands of dollars. We
are not aware of its use in any
commercial application. Further, these
systems have limitations, as
performance may be limited by
conditions such as fog, precipitation,
sea state, glare, water- and airtemperatures and ambient brightness,
and the successful results obtained to
date reflect a limited range of
environmental conditions and species.
NRDC acknowledges certain of these
limitations in their comment, including
that the systems have lesser utility in
warmer temperatures. The GOM,
however, is a warm environment. NRDC
does not provide specific suggestions
with regard to recommended systems or
characteristics of systems. NMFS does
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not consider requirements to use
systems such as those recommended by
NRDC to currently be practicable.
Comment: NRDC states that NMFS
should prescribe requirements for use of
‘‘noise-quieting’’ technology. NRDC
elaborates that in addition to requiring
noise-quieting technology (or setting a
standard for ‘‘noise output’’), NMFS
should ‘‘prescribe targets to drive
research, development, and adoption of
alternatives to conventional airguns.’’
Response: NMFS agrees with NRDC
that development and use of quieting
technologies, or technologies that
otherwise reduce the environmental
impact of geophysical surveys, is a
laudable objective and may be
warranted in some cases. However, here
the recommended requirements either
are not practicable or are not within
NMFS’ authority to require. To some
degree, NRDC misunderstands the
discussion of this issue as presented in
the notice of proposed rulemaking.
NMFS recognizes, for example, that
certain technologies, including the Bolt
eSource airgun, are commercially
available, and that certain techniques
such as operation of the array in
‘‘popcorn’’ mode may reduce impacts
when viable, depending on survey
design and objectives. However, a
requirement to use different technology
from that planned or specified by an
applicant—for example, a requirement
to use the Bolt eSource airgun—would
require an impracticable expenditure to
replace the airguns planned for use.
NRDC offers no explanation for why
such a large cost imposition (in the
millions of dollars) should be
considered practicable.
Separately, NRDC appears to suggest
that NMFS must require or otherwise
incentivize the development of wholly
new or currently experimental
technologies. We note that BOEM’s PEIS
concluded that alternative technologies
are in various stages of development,
and that none of the systems with the
potential to replace airguns as a seismic
source are currently commercially
available for use on a scale of activity
such as that considered herein.
Although some alternative technologies
are available now, or will be in the next
several years, for select uses, none are,
or will likely be in the next five years,
at a stage where they can replace airgun
arrays outright. However, some may be
used in select environments when
commercially available. According to
BOEM, the suggestion in this comment
would not provide the oil and gas
industry or the government with
sufficiently accurate data on the
location, extent, and properties of
hydrocarbon resources or the character
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of formation fluids or gases, or
information on shallow geologic hazards
and seafloor geotechnical properties, in
order to explore, develop, produce, and
transport hydrocarbons safely and
economically. Such technologies may be
evaluated in the future as they become
commercially available and on a scale
commensurate to the need. In summary,
while NMFS agrees that noise quieting
technology is beneficial, the suggestions
put forward by NRDC are either
impracticable or outside the authority
provided to NMFS by the MMPA.
However, NMFS would consider
participating in or learning about related
efforts by parties interested in
investigating these technologies. We
note that NMFS has described a process
by which new and unusual technologies
may be considered for use under this
rule (see Letters of Authorization).
Comment: NRDC recommended that
NMFS consider compensatory
mitigation for the adverse impacts of the
specified activity on marine mammals
and their habitat that cannot be
prevented or mitigated.
Response: NMFS has prescribed a
robust comprehensive suite of measures
that are expected to reduce the amount
of Level A and Level B harassment take,
as well as the severity of any incurred
impacts on the species or stock and
their habitat. Compensatory mitigation
is not required under the MMPA.
Importantly, NRDC did not recommend
any specific measure(s), rendering it
impossible to evaluate their
recommendation. In addition, many of
the methods of compensatory mitigation
that have proven successful in terrestrial
settings (e.g., purchasing or preserving
land with important habitat, improving
habitat through plantings) are not
applicable in a marine setting with such
far-ranging species. NMFS concludes
that the concept is too speculative at
this time to warrant specific action.
Letters of Authorization
Comment: The Associations assert
that it is ‘‘arbitrary and inappropriate’’
for NMFS to provide an opportunity for
public notice and comment in the event
that an LOA applicant wishes to deviate
from the modeling approach used
herein (which was subject to public
review and comment). The Associations
state that such a requirement is contrary
to the legal requirement to base the
authorization of incidental take under
the MMPA on the best available science,
as better information may become
available during the period of
effectiveness for the ITR.
Response: LOAs issued under the
authority of section 101(a)(5)(A) and
NMFS’ implementing regulations must
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be preceded by both substantive
findings (including a negligible impact
finding) and a process that includes
rulemaking after notice and comment.
In the case of LOA applications whose
take estimates are not based on the
modeling used for the rulemaking,
NMFS has determined that it may be
appropriate to subject those to notice
and comment in certain circumstances.
Such a process requirement does not
impede or contradict the requirement to
use the best available information.
Comment: The Associations and other
industry commenters assert that there is
no legal justification for NMFS to use
the ITR as a mechanism to limit the
number of activities that may occur in
the GOM, stating that authorization of
the activities themselves are subject to
BOEM’s jurisdiction.
Response: NMFS clarifies that we do
not intend to use the ITR in the manner
suggested by the Associations, and that
the language cited in the Associations’
comment (‘‘cap on the number of
authorizations that could be issued’’)
was inartful. We also acknowledge
BOEM’s jurisdiction regarding the
authorization of the subject activities
themselves. However, the total taking
analyzed in the negligible impact
analysis necessarily bounds the taking
that may be authorized under these
activity-specific regulations, as
described in the Estimated Take section.
Comment: Referencing a cap on the
number of authorizations that could be
issued, the MMC recommends that
NMFS (1) provide details to the public
on how NMFS plans to implement the
proposed cap and the basis for it; and
(2) allow for an additional 30-day
comment period to review such details
sufficiently in advance of issuing the
final rule.
Response: As discussed in the
preceding comment response, the
language referenced by the MMC was
meant only to affirm what is inherent in
the regulations, i.e., that the amount of
take analyzed for making a finding of
negligible impact necessarily bounds
the amount of take that may be
authorized through LOAs issued under
this rule (provided they also satisfy the
small numbers requirement). The MMC
places undue emphasis on this aspect of
rule implementation. In claiming a
‘‘lack of transparency,’’ the MMC
assigns complexity that does not exist,
and no additional details exist to give.
Therefore, we do not implement the
MMC’s recommendation for additional
public comment.
Comment: The Associations and other
industry commenters express concern
regarding the implementation of the
ITR, including the evaluation and
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processing of LOA requests. The
Associations recommend that the final
ITR clearly address how NMFS plans to
process LOA applications in a timely
and efficient manner, and encourage
NMFS to retain flexibility in the final
ITR for the development of efficient and
effective LOA processes through
workshops or other engagement with
BOEM and the regulated community.
Response: NMFS appreciates the
concerns expressed by the commenters.
We believe we have addressed these
issues in the updated preamble to this
ITR (see Letters of Authorization) and
are committed to ongoing, proactive
engagement with BOEM, BSEE, and the
regulated community towards efficient
implementation of the ITR.
Comment: BP comments that a lowfrequency geophysical survey source
they refer to as ‘‘Wolfspar’’ should be
considered to be within the range of
potential impacts modeled in the ITR
and, therefore, able to be used under an
LOA issued pursuant to the ITR.
Response: NMFS will look forward to
evaluating the Wolfspar source
according to the ‘‘New and Unusual
Technology’’ review process detailed in
the Letters of Authorization section of
this preamble. Only upon review of
additional information regarding the
source can NMFS make a determination
in this regard.
Regulatory Impact Analysis
Comment: The Associations provide a
bulleted list of criticisms of the RIA. We
summarize these here and provide brief
responses below. For full detail, we
refer the reader to the final RIA,
available online at:
www.fisheries.noaa.gov/action/
incidental-take-authorization-oil-andgas-industry-geophysical-surveyactivity-gulf-mexico. The Associations’
critiques of the RIA are not
accompanied by any specific
recommendations regarding potential
changes to the analysis or additional
data.
• The Associations assert that the RIA
assumes that the only indirect costs of
closures are delays, and state that such
measures ‘‘may render some survey
proposals economically unattractive to
the point at which prospects will not be
explored.’’ The Associations also state
that closures may be assumed to be
permanent, thereby having an
additional dampening impact on
exploration activity.
Response: The RIA accompanying the
proposed rule did not assume that the
costs of closures are simply delays. The
RIA stated that the ‘‘closures have the
potential to affect the overall levels of
G&G [geological and geophysical]
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activities that occur in the GOM over
the five-year timeframe of the analysis.
In the case that the closures delay or
reduce the ability of industry to collect
the necessary data to identify and
recover oil and gas resources, the overall
level of oil and gas production in the
GOM may in turn be delayed or
reduced.’’ The RIA for the proposed rule
discussed the possibility of both delays
and reductions in activity due to the
uncertainty surrounding rule impacts.
In addition, NMFS reiterates that
closures and any other measures are in
effect only during the five-year period of
effectiveness of the ITR. It is unclear
why closures may be ‘‘assumed to be
permanent’’ if the regulations requiring
them are effective only for five years.
We note here that two of the closure
areas included in the proposed rule and
evaluated in the RIA are no longer in the
final rule because they fall outside the
area considered for this rule, following
BOEM’s update of the rule’s scope.
• The Associations assert that the RIA
‘‘incorrectly assumes that the costs of
closures are highly uncertain or even
low because geologic potential of some
areas is low,’’ stating that geophysical
surveys are essential to understanding
the geologic potential of the areas.
Response: There is significant
uncertainty regarding the development
potential of the areas considered for
closure, and the RIA did not simply
assume that it is ‘‘low.’’ The RIA
accompanying the proposed rule
provided the best available information
regarding lease activity and reserves in
the proposed closure areas and
characterized the associated
uncertainty.
• The Associations assert that the RIA
‘‘wrongly assumes that the GOMESA
moratorium prevents exploration of the
Eastern GOM,’’ when in fact the
moratorium is currently set to expire in
2022. The Associations go on to state
that ‘‘the RIA seriously misleads readers
about the costs of closure and increased
restrictions in the Eastern GOM,’’ and
that the potential cost of the closure
should be considered equivalent to that
of the closure considered for the Central
GOM because ‘‘high-potential resources
may underlie’’ the Eastern GOM closure.
Response: The RIA made no such
assumption, and in fact acknowledged
that the moratorium does not restrict
exploration per se. However, the Eastern
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GOM closure referenced by the
commenter is no longer part of the rule,
as BOEM’s update to the scope of the
rule has removed the area from
consideration.
• The Associations state that the RIA
fails to account for the environmental
benefit associated with avoiding
unnecessary drilling via use of
geophysical surveys. Chevron echoes
this comment. Neither commenter
provides any specific recommendation
as to how they believe it should be
considered.
Response: The RIA does acknowledge
the benefit of geophysical technology.
However, we note that the magnitude of
this benefit depends on the extent to
which exploration and development
companies move forward with drilling
in cases where they have less seismic
data than they otherwise would because
of the requirements of the ITR.
• The Associations assert that the RIA
for the proposed rule incorrectly
assumes current geophysical data in the
Eastern GOM is suitable, stating that
‘‘there is high demand for state-of-theart new data for Eastern GOM frontier
areas where older data is considered
unsuitable to support new investment.’’
Response: The RIA did not state that
current geophysical data for the Eastern
GOM is ‘‘suitable.’’ Rather, the RIA
stated that ‘‘the suitability of existing
G&G data to direct oil and gas
production in the closure areas is
unknown.’’ As noted herein, the area of
concern to the commenter is no longer
considered through this rule.
• The Associations assert that the RIA
‘‘fails to account for possible increased
industry interest in Eastern GOM
geophysical surveys’’ and, therefore,
that the RIA inappropriately relies on
old statistics on survey interest for
estimating costs.
Response: The RIA acknowledged that
industry interest in Eastern GOM
geophysical surveys is likely to increase
leading up to the expiration of the
moratorium. As noted herein, the area of
concern to the commenter is no longer
considered through this rule.
Comment: Chevron comments that
NMFS should ensure in the final ITRs
that all costs are evaluated, including
the cost of reduced environmental
benefits from effective geophysical
surveys. The Associations echo these
concerns.
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Response: NMFS has appropriately
evaluated the regulatory impacts of the
ITR according to the requirements of
E.O. 12866. See section 5.3 of the Final
RIA, which describes this benefit of
geophysical technology. The magnitude
of this benefit depends on the extent to
which exploration and development
companies move forward with drilling
in cases where they have less seismic
data than they otherwise would because
of the rule.
National Environmental Policy Act
Comment: NRDC reiterates (and
resubmitted) comments that it
submitted on BOEM’s draft PEIS, stating
that as it relates to marine mammals, the
PEIS is deficient on its face due to the
range of alternatives and mitigation
considered, significance criteria, take
and impact estimates, and cumulative
impacts analysis.
Response: As a cooperating agency,
NMFS reviewed all responses to
comments on the draft PEIS that were
relevant to its management authorities
and provided input where we deemed it
appropriate. See Appendix M of the
Final PEIS.
Comment: NRDC also states that
NMFS cannot rely on the PEIS because
it ‘‘does not adequately address NMFS’
own actions and responsibilities under
the MMPA,’’ given that BOEM’s PEIS is
‘‘framed around a fundamentally
different purpose and need’’ relating to
its mandates under the Outer
Continental Shelf Lands Act (OCSLA)
that is ‘‘incongruent with NMFS
obligations under the MMPA.’’
Response: The proposed action at
issue is BOEM’s issuance of permits or
authorizations for G&G activities in the
GOM. PEIS Chapter 1.1.1. The PEIS also
recognizes that NMFS’ proposed action
is a decision on whether to approve
BOEM’s petition for incidental take
regulations. NOAA is a cooperating
agency on BOEM’s PEIS, as NOAA has
jurisdiction by law and special expertise
over marine resources impacted by the
proposed action, including marine
mammals and federally listed
threatened and endangered species. The
PEIS explicitly recognizes that the PEIS
would be used in support of NMFS’
decision on BOEM’s petition for
incidental take regulations. See PEIS
Appendix B.
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Consistent with the Council on
Environmental Quality’s (CEQ’s)
regulations, it is accepted NEPA
practice for NOAA to adopt a lead
agency’s NEPA analysis when, after
independent review, NOAA determines
the document to be sufficient in
accordance with 40 CFR 1506.3.
Specifically here, NOAA is satisfied that
BOEM’s PEIS adequately addresses the
impacts of issuing the MMPA incidental
take authorization and that NOAA’s
comments and concerns have been
adequately addressed. There is no
requirement in CEQ regulations that
NMFS, as a cooperating agency, issue a
separate purpose and need statement in
order to ensure adequacy and
sufficiency for adoption. Nevertheless,
the statement of Purpose and Need in
the PEIS explicitly acknowledges
NMFS’ own separate action of issuing
an MMPA incidental take authorization,
and the PEIS is replete with discussion
of issues relating to the issuance of an
MMPA authorization, including
discussion of marine mammal impacts,
mitigation, and take estimates. NMFS’
early participation in the NEPA process
and the agency’s continuing role in
shaping and informing analyses using
its special expertise ensured that the
analysis in the PEIS is sufficient for
purposes of NMFS’ own NEPA
obligations related to its issuance of an
incidental take authorization under the
MMPA.
Regarding the alternatives, NMFS’
early involvement in the development
of the PEIS and role in evaluating the
effects of incidental take under the
MMPA ensured that the PEIS would
include adequate analysis of a
reasonable range of alternatives. The
PEIS includes a no action alternative
specifically to address what could
happen if NMFS did not issue an
MMPA authorization. Some of the
alternatives explicitly reference marine
mammals or mitigation designed for
marine mammals in their title. More
importantly, these alternatives fully
analyze a comprehensive variety of
mitigation measures for marine
mammals. This mitigation analysis
supported NMFS’ evaluation of our
options in potentially issuing an MMPA
authorization. This approach to
evaluating a reasonable range of
alternatives is consistent with NMFS’
policy and practice for issuing MMPA
incidental take authorizations. NOAA
independently reviewed and evaluated
the PEIS, including the purpose and
need statement and range of
alternatives, and determined that the
PEIS fully satisfies NMFS’ NEPA
obligations related to its decision to
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issue the MMPA final rule and
associated Letters of Authorization.
Accordingly, NMFS has adopted the
PEIS.
Finally, we disagree with the notion
that the district court’s decision in
Conservation Council for Hawaii v.
NMFS somehow would preclude NMFS
from adopting the PEIS here. In
Conservation Council, the court
concluded that the FEIS NMFS adopted
was deficient because it did not
consider a true ‘‘no action’’ alternative
from NMFS’ perspective, in that the ‘‘no
action’’ alternative assumed
continuation of Navy’s baseline
activities, and therefore avoided the task
facing NMFS, i.e., whether to authorize
the requested take. 97 F. Supp. 3d at
1236. In contrast, the PEIS here for
NMFS’ rule for GOM geophysical
surveys includes a ‘‘no action’’
alternative from the perspectives of both
NMFS and BOEM. See PEIS, Chapter
2.9.1, pp. 2–20 to 2–22.
Information Quality Act
Comment: The CRE states that NMFS’
Technical Guidance violates
Information Quality Act (IQA)
requirements, because it (1) does not
include an IQA Pre-dissemination
Review Certification; (2) relies heavily
on models that have not been peer
reviewed to determine whether they are
validated and comply with the
Environmental Protection Agency’s
Council for Regulatory Environmental
Modeling (CREM) guidance; and (3)
relies heavily on models that were not
peer reviewed in compliance with the
Office of Management and Budget’s
(OMB) Final Information Quality
Bulletin for Peer Review (70 FR 2664;
January 14, 2005).
Response: The CRE is incorrect.
NMFS performed appropriate predissemination review and
documentation according to relevant
agency guidance (NMFS Policy
Directive PD 04–108, Policy on the Data
Quality Act; NMFS Instruction 04–108–
03, Section 515 Pre-Dissemination
Review and Documentation Guidelines).
All aspects of development of the 2016
Technical Guidance were peer reviewed
(www.cio.noaa.gov/services_programs/
prplans/ID43.html). Also of note, the
same information and methodology that
supported development of NMFS’
Technical Guidance (NMFS, 2016, 2018)
were more recently published in a peerreviewed journal (Southall et al.,
2019a).
Comment: CRE states that NMFS’ use
of models in the acoustic exposure
modeling process for this rule violates
the IQA because ‘‘they are incomplete,
unfinished, inaccurate, unreliable, have
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5385
never been validated, and have never
been peer reviewed.’’ CRE also asserts
that NMFS has not conducted predissemination review and
documentation as required by the IQA
and implies that, because NMFS did not
address the IQA in the notice of
proposed rulemaking, we must be in
violation of it.
Response: CRE is incorrect; NMFS is
in compliance with the requirements of
the IQA. NMFS conducted the required
pre-dissemination review at both the
proposed and final stages of this
rulemaking and appropriate
documentation is included in the
administrative record for this action.
CRE asserts that the models used in
NMFS’ rulemaking process are not
properly evaluated or validated. CRE
asserts that as a result, NMFS ‘‘grossly
overestimate[s] exposures and takes.’’
According to the CRE, the supposed
failings of the modeling necessarily lead
to the overestimation of takes, as
opposed to error in potentially different
directions and of different magnitude in
association with the various
components of the modeling process.
CRE comments at length that NMFS
should use only the relatively simple
approach of ‘‘Line Transect,’’ which
they believe will result in lower
numbers of estimated takes (see more
detailed response to these suggestions
earlier in Comments and Responses).
In asserting that the models used in
support of this rule have not been
adequately validated or peer reviewed,
CRE refers to a similarly sophisticated,
proprietary modeling package (Marine
Acoustics, Inc.’s Acoustic Integration
Model (‘‘AIM’’)) that underwent a
dedicated external peer review, stating
that AIM is ‘‘therefore properly
validated and acceptable for regulatory
use.’’ However, the AIM package
functions virtually the same as the
models used for this analysis, and was
used for an essentially identical
modeling process developed in support
of BOEM’s 2014 PEIS for geological and
geophysical survey activities on the
Mid- and South Atlantic Outer
Continental Shelf.
The IQA concerns expressed in the
comment are unfounded. As stated in
the NOAA Information Quality
Guidelines, information quality is
composed of three elements: Utility,
integrity, and objectivity.
Utility means that disseminated
information is useful to its intended
users. The disseminated information at
issue here—modeled exposures of
marine mammals to underwater noise—
is useful to NMFS in that it forms the
basis for subsequent analysis allowing
NMFS to make determinations
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necessary under the MMPA. It is useful
to the public in that it enables
appropriate review of NMFS’ action and
supporting determinations. It is useful
to the regulated entities in that it will
allow for an efficient regulatory regime,
in which potential LOA applicants may
make use of the existing modeling effort
(while being afforded the opportunity to
engage in different modeling if desired)
in service of a streamlined LOA
application process.
Integrity refers to security, i.e., the
protection of information from
unauthorized access or revision, to
ensure that the information is not
compromised through corruption or
falsification. The integrity of the
information disseminated herein was
not questioned, but it meets all relevant
standards for integrity (as demonstrated
in the administrative record for this
action).
Finally, objectivity ensures that
information is accurate, reliable, and
unbiased, and that information products
are presented in an accurate, clear,
complete, and unbiased manner.
Objectivity consists of two distinct
elements: Presentation and substance.
The presentation element includes
whether disseminated information is
presented in an accurate, clear,
complete, and unbiased manner and in
a proper context. NMFS has
appropriately presented the
disseminated information, and CRE
does not assert otherwise. The substance
element involves a focus on ensuring
accurate, reliable, and unbiased
information. Disseminated information
reflects the inherent uncertainty of the
scientific process, which is inseparable
from the concept of statistical variation.
In assessing information for accuracy,
the information is considered accurate if
it is within an acceptable degree of
imprecision or error appropriate to the
particular kind of information at issue
and otherwise meets commonly
accepted scientific and statistical
standards, as applicable. This concept is
inherent in the definition of
‘‘reproducibility,’’ as used in the OMB
IQA Guidelines and adopted by NOAA.
Therefore, original and supporting data
that are within an acceptable degree of
imprecision, or an analytic result that is
within an acceptable degree of
imprecision or error, are by definition
within the agency standard and are
therefore considered correct. CRE does
not assert that the modeling results
disseminated by NMFS are outside the
bounds of an acceptable degree of
imprecision or error.
The modeling report goes into great
detail regarding potential error
associated with different facets of the
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modeling process, and provides specific
analysis of uncertainty in both the
acoustic and animal phases of the
modeling process (discussed in detail in
the notice of proposed rulemaking and
in the modeling report). Uncertainty
associated with all aspects of the
modeling was clearly identified and
evaluated as to the effect on the overall
modeling results. In order to best
represent the overall uncertainty
associated with the modeling, the report
presents the exposure estimates as a
distribution. The exposure estimate
distribution provides the public with an
understanding of the probability of
certain events occurring, including the
probability that an operation would not
result in any animals being exposed
above a defined threshold.
Regarding reproducibility and
transparency, the NOAA Information
Quality guidelines state that
‘‘reproducibility means that the
information is capable of being
substantially reproduced, subject to an
acceptable degree of imprecision [. . .]
With respect to analytic results, ‘capable
of being substantially reproduced’
means that independent analysis of the
original or supporting data using
identical methods would generate
similar analytic results, subject to an
acceptable degree of imprecision or
error.’’ We have no reason to believe
that similar modeling (for example,
using the AIM modeling package) using
the same data inputs would not return
similar analytic results, and CRE
provides none. Transparency is not
defined in the OMB Guidelines, but is
at the heart of the reproducibility
standard. At its most basic,
transparency—and ultimately
reproducibility—is a matter of showing
how you got the results you got. NMFS
has produced a painstakingly detailed
accounting of the modeling process and
decisions made, such that an
independent party using a different set
of models would be able to perform a
similar modeling effort in order to
evaluate the similarity of the results.
The modeling report includes a full
description of all assumptions and
reference material used for both sound
sources and species of interest. CRE
provides no meaningful argument to the
contrary.
The NOAA Information Quality
guidelines expressly address and allow
for the use of proprietary models and
other supporting information which
cannot be disclosed. In such cases, the
guidelines call for ‘‘especially rigorous
robustness checks.’’ As summarized
below and described in detail in the
notice of proposed rulemaking and
modeling report, NMFS has conducted
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rigorous robustness checks of the
proprietary models used in support of
this rule.
The models used in estimating the
acoustic exposures described herein
have been appropriately validated and
reviewed. As described in detail in the
notice of proposed rulemaking and in
the modeling report, the acoustic
exposure modeling effort requires the
use of a package of models. Acoustic
exposure modeling in general is not
novel, controversial, or precedentsetting, and similar modeling has been
performed for various applications for
over 15 years. This type of modeling
requires modeling of the acoustic output
of a source, in this case a specified
airgun array (as well as a single airgun
and certain electromechanical sources
that were modeled separately). The
output of the source model is an input
to a model or models used to model
underwater sound propagation as a
function of range from the source. The
output of this process is a 3D sound
field. Subsequently, an animal
movement model is used to simulate the
behavior of virtual animats in relation to
the modeled sound field. Each animat
acts as a virtual dosimeter, producing
individual records of exposure history.
There were many animats in the
simulations, and together their received
levels represent the probability, or risk,
of exposure for each survey.
In this case, the source model used
was JASCO Applied Sciences’
proprietary Airgun Array Source Model
(AASM). The AASM accepts airgun
volume, pressure, and depth and has
internal parameters that must be fit to
real signature data. The model was
originally fit to a large library of
empirical airgun data spanning a range
of airgun volumes and operating depths.
Subsequently, the model was improved
to better predict airgun radiation at
frequencies above 1 kHz. Development
and validation of this improved version
were made possible by high quality
airgun source signature data from field
studies conducted under the industrysponsored Joint Industry Program on
Sound and Marine Life. Desktop
evaluation and validation of AASM
have been conducted against
commercial geophysical source models
such as Gundalf and Nucleus.
JASCO’s proprietary Marine
Operations Noise Model (MONM) was
used to generate the 3D sound fields
necessary for sound exposure estimates.
MONM is based on standard and proven
acoustic propagation models. In this
case, propagation at frequencies less
than 2 kHz was computed using a
version of the U.S. Naval Research
Laboratory’s Range-dependent Acoustic
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Model (RAM), which is based on a
parabolic equation (PE) solution to the
wave equation and extensively verified
and validated under the Navy Ocean
and Atmospheric Master Library
process. The PE method has been
extensively benchmarked and is widely
employed in the underwater acoustics
community (Collins et al., 1996), and
RAM’s predictions (as generated within
the MONM infrastructure) have been
validated against experimental data in
several underwater acoustic
measurement programs conducted by
JASCO (e.g., Aerts et al., 2008; Funk et
al., 2008; Ireland et al., 2009; Blees et
al., 2010; Warner et al., 2010). At
frequencies greater than 2 kHz,
increased sound attenuation due to
volume absorption at higher frequencies
is accounted for with the widely-used
BELLHOP Gaussian beam ray-trace
propagation model (Porter and Liu,
1994). Both of these complementary,
non-proprietary propagation models
(RAM and BELLHOP) have been
extensively tested over many years and
are accepted by the acoustics
community. Implementation of these
codes within the MONM infrastructure
has been evaluated and validated
against other PE codes including RAMS,
RAM-Geo and original RAM, and
against normal mode or wavenumber
integration (fast field) methods in
standard codes. Finally, JASCO has
conducted end-to-end validation of
source and propagation modeling
against field data collected in sound
source verification experiments,
demonstrating that the results of the
acoustic field modeling are in agreement
with field data. The comparison of
model results and measurements show
that MONM can produce reliable results
in challenging acoustic propagation
conditions (Hannay and Racca, 2005).
The non-proprietary, peer-reviewed
Marine Mammal Movement and
Behavior (3MB) model (Houser, 2006)
was used to generate realistic paths of
simulated animals (animats) in the
modeled area. JASCO’s Exposure
Modeling System (JEMS) was used to
combine animal movement data (i.e.,
the output from 3MB), with precomputed acoustic fields (i.e., the
output from MONM described above).
The JEMS is a relatively simple piece of
software that acts as an indexer that
finds the sound level from the
computed fields for the location of each
animat through time. The numerous,
rigorous robustness checks described for
the multiple modeling components are
sufficient to comply with the IQA
requirements, and no additional peer
review is required.
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While certain components of the
modeling process (AASM, MONM, and
JEMS) are proprietary in the sense that
JASCO does not make the code publicly
available, they are all based on standard
physics or mathematical models
generally accepted in the field and
based on peer-reviewed models (e.g.,
3MB). In addition, ample opportunity
has been provided for public input and
review of the underlying scientific
information and modeling efforts
contained herein (including by
scientists, peer experts at other agencies,
and non-governmental organizations).
Relevant data is provided such that an
entity using similar models could
reproduce or challenge the results.
While the modeling results
disseminated here may reasonably be
considered to be influential for purposes
of the OMB Peer Review Bulletin—
meaning that the information may
reasonably be considered to have a clear
and substantial impact on important
public policies, such as this ITR—the
modeling is not a ‘‘highly influential
scientific assessment,’’ (HISA) which is
defined as a scientific assessment that:
(i) Could have a potential impact of
more than $500 million in any year, or
(ii) is novel, controversial, or precedentsetting or has significant interagency
interest. As described above, similar
approaches to acoustic exposure
modeling have been performed by
numerous disparate entities for multiple
applications. In 2014, during the
aforementioned modeling workshop cosponsored by the American Petroleum
Institute and International Association
of Geophysical Contractors, at least a
half-dozen expert presenters
(representing private and governmental
entities from both the United States and
Europe) discussed various available
packages that function much the same
way as what is described here. There is
nothing novel, controversial, or
precedent-setting about the modeling
described here, and the additional peer
review requirements associated with
HISAs are not applicable.
Miscellaneous
Comment: NRDC contends that NMFS
must consider a standard requiring
analysis and selection of minimum
source levels. In furtherance of this
overall quieting goal, NRDC also states
that NMFS should consider requiring
that all vessels employed in the survey
activities undergo regular maintenance
to minimize propeller cavitation and be
required to employ the best shipquieting designs and technologies
available for their class of ship, and that
NMFS should require these vessels to
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5387
undergo measurement for their
underwater noise output.
Response: An expert panel, convened
by BOEM to determine whether it
would be feasible to develop standards
to determine a lowest practicable source
level, determined that it would not be
reasonable or practicable to develop
such metrics (see Appendix L in BOEM,
2017). NMFS does not believe it
appropriate to address disagreements
with these conclusions to us. NRDC
further claims that NMFS’ deference to
the findings of an expert panel
convened specifically to consider this
issue is ‘‘arbitrary under the MMPA.’’
The bulk of NRDC’s comment appears to
be addressed to BOEM, and NMFS
encourages NRDC to engage with BOEM
regarding these alleged shortcomings of
the panel’s findings. The subject matter
is outside NMFS’ expertise, and we
have no basis upon which to doubt the
panel’s published findings.
With regard to the recommended
requirements to measure or control
vessel noise, or to make some minimum
requirements regarding the design of
vessels used in the surveys, NMFS
disagrees that these requirements would
be practicable. While NMFS agrees that
vessel noise is of concern in a
cumulative and chronic sense, it is not
of substantial concern in relation to the
MMPA’s least practicable adverse
impact standard for this specified
activity, given the few vessels used in
any given survey and relative to
commercial shipping. NMFS looks
forward to continued collaboration with
NRDC and others towards ship quieting.
Comment: NRDC states that NMFS
must consider mitigation that limits and
reduces the amount of survey activity,
including ‘‘prohibit[ing]’’ duplicative
surveys, and should consider
‘‘consolidating’’ surveys. Similarly, the
MMC recommends that NMFS ‘‘work
with BOEM’’ to require industry
operators to increase collaboration on
seismic surveys whenever possible.
Response: NRDC states that NMFS
should ‘‘require and enforce a cap’’ on
surveys, without explaining how they
believe this is within NMFS’ statutory
authority or suggesting ways to
appropriately apportion the amount of
effort that might be allowed. NMFS
cannot arbitrarily limit planned effort
and has no legitimate means of changing
the specified activity absent a
conclusion that the activity would have
more than a negligible impact. However,
NMFS has made the necessary findings
under the MMPA for issuance of this
rule. NRDC goes on to state that NMFS
should ‘‘require BOEM to eliminate
unnecessary duplication of survey
effort’’ but does not explain how they
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believe that this suggestion is within
NMFS’ statutory authority. As the
permitting agency, BOEM has the
authority to require permit applicants to
submit statements indicating that
existing data are not available to meet
the data needs identified for the
applicant’s survey (i.e., non-duplicative
survey statement), but such
requirements are not within NMFS’
purview. NMFS may not demand that
BOEM discharge its authority under
OCSLA in any particular manner. As
stated previously, NMFS considers the
specified activity described by an
applicant in reviewing a request for an
incidental take authorization. Nothing
in the statute provides authority to
direct consolidation or removal of
activities based on some presumption of
duplication that NMFS is not qualified
to judge. NRDC claims erroneously that
NMFS ‘‘has authority under the
mitigation provision of the MMPA to
consider directing the companies to
consolidate their surveys,’’ placing such
a requirement under the auspices of
practicability. Leaving aside that
directing any given applicant to
abandon their survey plans would not
in fact be practicable, it is inappropriate
to consider this suggested requirement
through that lens.
The MMC specifically cites a number
of collaborative surveys conducted in
foreign waters and recommends that
NMFS ‘‘work with BOEM’’ to require
such collaboration. However, the MMC
provides no useful recommendations as
to how such collaboration might be
achieved. Given the absence of
appropriate statutory authority, NMFS
is willing to explore with the MMC
possible mechanisms for fostering such
collaboration between geophysical data
acquisition companies and relevant
Federal agencies, within the context of
our respective authorities.
NMFS also notes that, although
surveys may be perceived as
‘‘duplicative’’ simply because other
surveys have also occurred in the same
location, they are in fact designed
specifically to produce proprietary data
that satisfies the needs of survey
funders. As noted by NRDC, BOEM
convened an expert panel to study the
issue of duplicative surveys (see
Appendix L in BOEM, 2017) and
developed standards for consideration
of what surveys are duplicative. NRDC
provides extensive discussion of their
thoughts regarding the insufficiency of
BOEM’s duplicative survey standard
and its implementation. We respectfully
suggest that these comments are more
appropriately directed at BOEM.
Comment: Chevron states that NMFS
‘‘must be mindful of the mandates
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under OCSLA to assess and then
balance the costs and benefits of
alternative restrictions on geophysical
activities against a requirement for
‘expeditious and orderly development’
of GOM resources.’’
Response: NMFS’ statutory
obligations arise under the Marine
Mammal Protection Act (with associated
requirements under the Endangered
Species Act, National Environmental
Policy Act, and Administrative
Procedure Act, among others). NMFS
has no statutory obligation relative to
OCSLA.
Comment: CRE provides several
comments relating to E.O. 12866. CRE
reiterates their view that there is ‘‘no
harm from seismic,’’ and therefore, that
it is not surprising that NMFS has not
produced a quantitative statement of
benefits. They also conclude that
‘‘[s]ince the benefits of the proposed
rule are minimal at best, the resultant
benefit-cost ratio is less than one,
making the proposed rule noncompliant’’ with E.O. 12866.
Response: NMFS disagrees with the
commenter’s premise that there is no
potential for harm, and accordingly
evaluated the impacts of the specified
activity and prescribed appropriate
mitigation in the ITR, as required under
the MMPA. With respect to E.O. 12866,
the RIA provides a qualitative
description of potential ecological
benefits and their economic
implications due to uncertainty
preventing quantification. Similar to the
qualitative evaluation of costs
associated with the proposed area
closures, the qualitative treatment of
benefits does not indicate a lesser
magnitude, but rather more data
limitations or uncertainty.
Comment: Regarding E.O. 13211,
Chevron comments that NMFS has
provided inconsistent statements that
should be resolved.
Response: NMFS has clarified its
discussion regarding E.O. 13211.
Overall, within the five-year timeframe
of the analysis, the ITR is not expected
to constitute a significant adverse effect
on energy supply, distribution or use,
according to the thresholds described by
E.O. 13211, given that the direct
compliance costs represent a small
fraction (on the order of less than one
percent) of the total costs of exploration
and development in the GOM.
Comment: Chevron notes that E.O.
13795 required evaluation of NMFS’
2016 Technical Guidance (review of
which was ongoing at the time of
publication of the notice of proposed
rulemaking). Chevron also asserts that
assumptions of the 2016 Technical
Guidance ‘‘are multiplied with those in
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other elements of the modeling to reach
‘unrealistic’ conclusions.’’ Because the
2016 Technical Guidance was used in
the modeling, Chevron asserts that the
modeling is inconsistent with the
requirements of E.O. 13795. The CRE
also claims that use of the 2016
Technical Guidance is in violation of
E.O. 13795 and that the guidance should
be rescinded or substantially revised.
CRE also states that NMFS must
emphasize that use of the Technical
Guidance is not required.
Response: Review of the Technical
Guidance under E.O. 13795 was
completed in 2018. In response to the
feedback received during the public
comment period and the Interagency
Consultation meeting, the Secretary of
Commerce approved NMFS to issue a
2018 Revised Technical Guidance for
Assessing the Effects of Anthropogenic
Sound on Marine Mammal Hearing:
Acoustic Thresholds for Onset of
Permanent and Temporary Threshold
Shifts (2018 Revised Technical
Guidance) (NOAA Technical
Memorandum NMFS–OPR–59) (June 21,
2018). NMFS’ use of the guidance is,
therefore, in compliance with E.O.
13795.
The 2018 Revised Technical Guidance
retains the thresholds and weighting
functions presented in the original 2016
Technical Guidance. Chevron’s
comment that the Technical Guidance
somehow contributes to what they
characterize as ‘‘unrealistic’’
conclusions is, in context of industry’s
overall comments on the modeling
effort, unpersuasive. The industryfunded supplementary modeling
variable analysis (Zeddies et al., 2017b)
found that use of the Technical
Guidance was the single most
influential factor in reducing the
modeled exposures (for Level A
harassment).
We acknowledge that the Technical
Guidance is indeed guidance, and its
use is voluntary (as stated in the
Executive Summary of the Technical
Guidance). The Technical Guidance
provides more detail on if/when an
alternative approach may be used.
Description of Marine Mammals in the
Area of the Specified Activities
Sections 3 and 4 of the petition
summarize available information
regarding status and trends, distribution
and habitat preferences, and behavior
and life history of the potentially
affected species. NMFS refers the reader
to those descriptions, descriptions of the
affected environment in Appendix E of
BOEM’s PEIS, as well as NMFS’ Stock
Assessment Reports (SAR;
www.fisheries.noaa.gov/national/
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marine-mammal-protection/marinemammal-stock-assessments),
incorporated here by reference, instead
of reprinting the information.
Additional general information about
these species (e.g., physical and
behavioral descriptions) may be found
on NMFS’ website
(www.fisheries.noaa.gov/find-species).
Table 4 lists all species with expected
potential for occurrence in the GOM and
summarizes information related to the
population or stock, including potential
biological removal (PBR). For taxonomy,
we follow Committee on Taxonomy
(2020). PBR, defined by the MMPA as
the maximum number of animals, not
including natural mortalities, that may
be removed from a marine mammal
stock while allowing that stock to reach
or maintain its optimum sustainable
population, is considered in concert
with known sources of ongoing
anthropogenic mortality (as described in
NMFS’ SARs). For status of species, we
provide information regarding U.S.
regulatory status under the MMPA and
ESA.
Marine mammal abundance estimates
presented in this document represent
the total number of individuals that
make up a given stock or the total
number estimated within a particular
study area. NMFS’ stock abundance
estimates for most species represent the
total estimate of individuals within the
geographic area, if known, that
comprises that stock. For some species,
this geographic area may extend beyond
U.S. waters. Survey abundance (as
compared to stock or species
abundance) is the total number of
individuals estimated within the survey
area, which may or may not align
completely with a stock’s geographic
range as defined in the SARs. These
surveys may also extend beyond U.S.
waters. For many GOM stocks,
information regarding distribution and
range-wide abundance is limited, as
available data are generally limited to
U.S. waters of the northern GOM.
Abundance and distribution for GOM
stocks occurring in the Mexican EEZ or
the high seas are poorly understood. As
discussed in additional detail below,
U.S. waters only comprise about 40
percent of the entire GOM, and 65
percent of GOM oceanic waters are
south of the U.S. EEZ. Studies based on
abundance and distribution surveys
restricted to U.S. waters are unable to
detect temporal shifts in distribution
beyond U.S. waters that might account
for any changes in abundance within
U.S. waters.
In some cases, species are treated as
guilds. In general ecological terms, a
guild is a group of species that have
similar requirements and play a similar
role within a community. However, for
purposes of stock assessment or
abundance prediction, certain species
may be treated together as a guild
because they are difficult to distinguish
visually and many observations are
ambiguous. For example, NMFS’ GOM
SARs assess stocks of Mesoplodon spp.
and Kogia spp. as guilds. Here, we
consider beaked whales and Kogia spp.
as guilds. In the following discussion,
reference to ‘‘beaked whales’’ includes
the Cuvier’s, Blainville’s, and Gervais
beaked whales, and reference to ‘‘Kogia
spp.’’ includes both the dwarf and
pygmy sperm whale.
Twenty-one species (with 24 managed
stocks) have the potential to co-occur
with the prospective survey activities.
Extralimital species or stocks unlikely to
co-occur with survey activity include 31
estuarine bottlenose dolphin stocks, the
blue whale (Balaenoptera musculus), fin
whale (B. physalus), sei whale (B.
borealis), minke whale (B.
acutorostrata), humpback whale
(Megaptera novaeangliae), North
Atlantic right whale (Eubalaena
glacialis), and the Sowerby’s beaked
whale (Mesoplodon bidens). All
mysticete species listed here (as well as
Sowerby’s beaked whale) are considered
only of accidental occurrence in GOM
and are generally historically known
only from a very small number of
strandings and/or sightings (Wu¨rsig et
al., 2000; Wu¨rsig, 2017). In addition,
following BOEM’s update to the scope
of activity considered through this rule,
the eastern coastal stock of bottlenose
dolphin, which was considered in the
notice of proposed rulemaking, would
no longer be potentially impacted by
activities that may be authorized under
this rule. For detailed discussion of
these species, please see the notice of
proposed rulemaking (83 FR 29212;
June 22, 2018). In addition, the West
Indian manatee (Trichechus manatus
latirostris) may be found in coastal
waters of the GOM. However, manatees
are managed by the U.S. Fish and
Wildlife Service and are not considered
further in this document. All managed
stocks in this region are assessed in
NMFS’ U.S. Atlantic SARs.
All values presented in Table 4,
which are available in the most recent
final SARs (Hayes et al., 2020) and have
not changed since the proposed rule
was published, are the most recent
available at the time the analyses for
this final rule were completed. We also
reviewed new information for many
GOM stocks in unpublished draft 2020
SARs. The unpublished draft SARs
include updates to most GOM stocks,
including to abundance estimates, PBR
values, and annual mortality and
serious injury (M/SI) estimates. The
most notable change is that, through the
introduction of M/SI estimates related to
the Deepwater Horizon (DWH) oil spill,
M/SI values are generally larger than in
past SARs and in some cases are larger
than the PBR values. NMFS has
considered this information and
determined that it is previously
accounted for as part of the baseline,
through our existing analysis of the
effects of the DWH oil spill. We have
fully considered the underlying
information in our analysis and have
determined that the unpublished draft
SAR updates do not impact our
conclusions.
TABLE 4—MARINE MAMMALS POTENTIALLY PRESENT IN THE SPECIFIED GEOGRAPHICAL REGION
Common name
Scientific name
ESA/
MMPA
status;
Strategic
(Y/N) 1
Stock
NMFS stock abundance
(CV, Nmin, most recent
abundance survey)2,7
Predicted
mean (CV)/
maximum
abundance 3
PBR
Annual
M/SI
(CV) 4
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Order Cetartiodactyla—Cetacea—Superfamily Mysticeti (baleen whales)
Family Balaenopteridae
(rorquals):
Bryde’s whale ...........
Balaenoptera edeni .........
Gulf of Mexico .................
E/D; Y
33 (1.07; 16; 2009) .........
44 (0.27)/n/a ...
0.03
0.8
1.1
0
Superfamily Odontoceti (toothed whales, dolphins, and porpoises)
Family Physeteridae:
Sperm whale .............
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GOM ................................
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E/D; Y
Sfmt 4700
763 (0.38; 560; 2009) .....
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TABLE 4—MARINE MAMMALS POTENTIALLY PRESENT IN THE SPECIFIED GEOGRAPHICAL REGION—Continued
Common name
Family Kogiidae:
Pygmy sperm whale
Dwarf sperm whale ...
Family Ziphiidae (beaked
whales):
Cuvier’s beaked
whale:.
Gervais beaked
whale.
Blainville’s beaked
whale.
Family Delphinidae:
Rough-toothed dolphin.
Common bottlenose
dolphin.
ESA/
MMPA
status;
Strategic
(Y/N) 1
Scientific name
Stock
Kogia breviceps ..............
GOM ................................
-; N
K. sima ............................
GOM ................................
-; N
Ziphius cavirostris ...........
GOM ................................
-; N
NMFS stock abundance
(CV, Nmin, most recent
abundance survey)2,7
Predicted
mean (CV)/
maximum
abundance 3
Annual
M/SI
(CV) 4
PBR
186 (1.04; 90; 2009) 5 .....
2,234 (0.19)/
6,117 5.
0.9
0.3 (1.0)
74 (1.04; 36; 2009) .........
2,910 (0.16)/
3,958 5.
.........................
0.4
0
0.8
0
4,853 (0.19)/n/
a.
138,602 (0.06)/
192,176 5.
2.5
0.8 (1.0)
42
469
6.5 (0.65)
0.8
60
0.4
175
0.6
0.6
0
Undet.
42 (0.45)
407
4.4
62
0
10
0
Undet.
0
16
7.9 (0.85)
13
0
0.8
0
Undet.
0
0.1
15
0
0.5 (1.0)
149 (0.91; 77;
2009) 5
Mesoplodon europaeus ..
GOM ................................
-; N
.....
M. densirostris .................
GOM ................................
-; N
Steno bredanensis ..........
GOM ................................
-; N
624 (0.99; 311; 2009) .....
Tursiops truncatus
truncatus.
GOM Oceanic .................
GOM Continental Shelf ...
-; N
-; N
GOM Coastal, Northern ..
-; N
GOM Coastal, Western ...
-; N
5,806 (0.39; 4,230; 2009)
51,192 (0.10; 46,926;
2011–12).
7,185 (0.21; 6,044; 2011–
12).
20,161 (0.17; 17,491;
2011–12).
129 (1.00; 64; 2009) .......
Clymene dolphin ..............
Stenella clymene .............
GOM ................................
-; N
Atlantic spotted dolphin ....
S. frontalis .......................
GOM ................................
-; N
Pantropical spotted dolphin.
Spinner dolphin ................
S. attenuata attenuata ....
GOM ................................
-; N
S. longirostris longirostris
GOM ................................
-; N
Striped dolphin .................
S. coeruleoalba ...............
GOM ................................
-; N
Fraser’s dolphin ...............
Lagenodelphis hosei .......
GOM ................................
-; N
Risso’s dolphin .................
Grampus griseus .............
GOM ................................
-; N
726 (0.7; 427; 1996–
2001)6.
2,442 (0.57; 1,563; 2009)
Melon-headed whale .......
Peponocephala electra ...
GOM ................................
-; N
2,235 (0.75; 1,274; 2009)
Pygmy killer whale ...........
Feresa attenuata .............
GOM ................................
-; N
152 (1.02; 75; 2009) .......
False killer whale .............
Pseudorca crassidens .....
GOM ................................
-; N
Killer whale ......................
Short-finned pilot whale ...
Orcinus orca ....................
Globicephala
macrorhynchus.
GOM ................................
GOM ................................
-; N
-; N
777 (0.56; 501; 2003–
04)6.
28 (1.02; 14; 2009) .........
2,415 (0.66; 1,456; 2009)
37,611 (0.28; 29,844;
2000–01)6.
50,880 (0.27; 40,699;
2009).
11,441 (0.83; 6,221;
2009).
1,849 (0.77; 1,041; 2009)
11,000 (0.16)/
12,115.
47,488 (0.13)/
85,108.
84,014 (0.06)/
108,764.
13,485 (0.24)/
31,341.
4,914 (0.17)/
5,323.
1,665 (0.73)/n/
a.
3,137 (0.10)/
4,153.
6,733 (0.30)/
7,105.
2,126 (0.30)/n/
a.
3,204 (0.36)/n/
a.
185 (0.41)/n/a
1,981 (0.18)/n/
a.
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1 ESA status: Endangered (E)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed under the ESA or designated as depleted under the
MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality exceeds PBR or which is determined to be declining and likely
to be listed under the ESA within the foreseeable future. Any species or stock listed under the ESA is automatically designated under the MMPA as depleted and as
a strategic stock.
2 NMFS marine mammal stock assessment reports online at: www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments. CV is
coefficient of variation; Nmin is the minimum estimate of stock abundance.
3This information represents species- or guild-specific abundance predicted by habitat-based cetacean density models (Roberts et al., 2016). These models provide
the best available scientific information regarding predicted density patterns of cetaceans in the U.S. Gulf of Mexico, and we provide the corresponding abundance
predictions as a point of reference. Total abundance estimates were produced by computing the mean density of all pixels in the modeled area and multiplying by its
area.
4 These values, found in NMFS’ SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (e.g., commercial fisheries,
ship strike). A CV associated with estimated mortality due to commercial fisheries is presented in some cases.
5 Abundance estimates are in some cases reported for a guild or group of species when those species are difficult to differentiate at sea. Similarly, the habitatbased cetacean density models produced by Roberts et al. (2016) are based in part on available observational data which, in some cases, is limited to genus or guild
in terms of taxonomic definition. NMFS’ SARs present pooled abundance estimates for Kogia spp. and Mesoplodon spp., while Roberts et al. (2016) produced density
models to genus level for Kogia spp. and as a guild for beaked whales (Ziphius cavirostris and Mesoplodon spp.). Finally, Roberts et al. (2016) produced a density
model for bottlenose dolphins that does not differentiate between oceanic, shelf, and coastal stocks. The modeled abundance estimate provided here for all
bottlenose dolphins includes abundance that may be attributed to the eastern coastal stock.
6 NMFS’ abundance estimates for these species are not considered current. PBR is therefore considered undetermined, as there is no current minimum abundance
estimate for use in calculation. We nevertheless present the most recent abundance estimate.
7 We note that Dias and Garrison (2016) present abundance estimates for oceanic stocks that were calculated for use in DWH oil spill injury quantification. For
most stocks, these estimates are based on pooled observations from shipboard surveys conducted in 2003, 2004, and 2009 and corrected for detection bias. Estimates for beaked whales and Kogia spp. were based on density estimates derived from passive acoustic data collection (Hildebrand et al., 2012). The abundance estimate for Bryde’s whales incorporated the results of additional shipboard surveys conducted in 2007, 2010, and 2012. Here we retain NMFS’ official SAR information
for comparison with model-predicted abundance (Roberts et al., 2016).
For the majority of species potentially
present in the specified geographical
region, NMFS has designated only a
single generic stock (i.e., ‘‘Gulf of
Mexico’’) for management purposes,
although there is currently no
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information to differentiate the stock
from the Atlantic Ocean stock of the
same species, nor information on
whether more than one stock may exist
in the GOM (Hayes et al., 2020).
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For the bottlenose dolphin, NMFS
defines an oceanic stock, a continental
shelf stock, and three coastal stocks. As
in the northwestern Atlantic Ocean,
there are two general bottlenose dolphin
ecotypes: ‘‘coastal’’ and ‘‘offshore.’’
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These ecotypes are genetically and
morphologically distinct (Hoelzel et al.,
1998; Waring et al., 2016), though
ecotype distribution is not clearly
defined and the stocks are delineated
primarily on the basis of management
rather than ecological boundaries. The
offshore ecotype is assumed to
correspond to the oceanic stock, with
the stock boundary (and thus the de
facto delineation of offshore and coastal
ecotypes) defined as the 200-m isobath.
The continental shelf stock is defined as
between two typical survey strata: The
20- and 200-m isobaths. While the shelf
stock is assumed to consist primarily of
coastal ecotype dolphins, offshore
ecotype dolphins may also be present.
There is expected to be some overlap
with the three coastal stocks as well,
though the degree is unknown and it is
not thought that significant mixing or
interbreeding occurs between them
(Waring et al., 2016). The coastal stocks
are defined as being in waters between
the shore, barrier islands, or presumed
outer bay boundaries out to the 20-m
isobath and, as a working hypothesis,
NMFS has assumed that dolphins
occupying habitats with dissimilar
climatic, coastal, and oceanographic
characteristics might be restricted in
their movements between habitats, thus
constituting separate stocks (Waring et
al., 2016). Shoreward of the 20-m
isobath, the eastern coastal stock
extends from Key West, FL to 84° W
longitude; the northern coastal stock
from 84° W longitude to the Mississippi
River delta; and the western coastal
stock from the Mississippi River delta to
the Mexican border. The latter is
assumed to be a trans-boundary stock,
though no information is available
regarding abundance in Mexican waters.
As noted above, the eastern coastal
stock will not be affected by activities
considered through this rule.
At the time of publication of the
notice of proposed rulemaking, the
GOM Bryde’s whale was proposed for
listing as an endangered species under
the ESA (81 FR 88639; December 8,
2016). Since that time, NMFS has listed
the GOM Bryde’s whale as endangered
under the ESA, effective on May 15,
2019 (84 FR 15446; April 15, 2019). The
proposed listing was based largely on
NMFS’ status review of Bryde’s whales
in the GOM (Rosel et al., 2016), and no
significant new information has become
available since that time. No critical
habitat has yet been designated for the
species, and no recovery plan has yet
been developed. NMFS’ analysis related
to the GOM Bryde’s whale in the notice
of proposed rulemaking was conducted
in context of the same information that
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informed the proposal to list the GOM
Bryde’s whale and, therefore, the final
listing decision itself does not introduce
new information for consideration in
the analysis for this final rulemaking.
In Table 4 above, NMFS reports two
sets of abundance estimates: Those from
NMFS’ SARs and those predicted by
Roberts et al. (2016)—for the latter, we
provide both the annual mean and the
monthly maximum (where applicable).
Please see footnotes 2–3 of Table 4 for
more detail. NMFS’ SAR estimates are
typically generated from the most recent
shipboard and/or aerial surveys
conducted. GOM oceanography is
dynamic, and the spatial scale of the
GOM is small relative to the ability of
most cetacean species to travel. As an
example, no groups of Fraser’s dolphins
were observed during dedicated
cetacean abundance surveys during
2003–2004 or 2009, yet the SAR states
that it is probable that Fraser’s dolphins
were present in the northern GOM but
simply not encountered, and therefore
declines to present an abundance
estimate of zero (Waring et al., 2013).
U.S. waters only comprise about 40
percent of the entire GOM, and 65
percent of GOM oceanic waters are
south of the U.S. EEZ. Studies based on
abundance and distribution surveys
restricted to U.S. waters are unable to
detect temporal shifts in distribution
beyond U.S. waters that might account
for any changes in abundance within
U.S. waters. NMFS’ SAR estimates also
typically do not incorporate correction
for detection bias. Therefore, they
should generally be considered
underestimates, especially for cryptic or
long-diving species (e.g., beaked whales,
Kogia spp., sperm whales). Dias and
Garrison (2016) state, for example, that
current abundance estimates for Kogia
spp. may be considerably
underestimated due to the cryptic
behavior of these species and difficulty
of detection in Beaufort sea state greater
than one, and density estimates for
certain species derived from long-term
passive acoustic monitoring are much
higher than are estimates derived from
visual observations (Mullin and Fulling,
2004; Mullin, 2007; Hildebrand et al.,
2012).
The Roberts et al. (2016) abundance
estimates represent the output of
predictive models derived from multiyear observations and associated
environmental parameters and which
incorporate corrections for detection
bias. Incorporating more data over
multiple years of observation can yield
different results in either direction, as
the result is not as readily influenced by
fine-scale shifts in species habitat
preferences or by the absence of a
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5391
species in the study area during a given
year. NMFS’ abundance estimates show
substantial year-to-year variability in
some cases. For example, NMFSreported estimates for the Clymene
dolphin vary by a maximum factor of
more than 100 (2009 estimate of 129
versus 1996–2001 estimate of 17,355),
indicating that it may be more
appropriate to use the model prediction
versus a point estimate, as the model
incorporates all available data (from
1992–2009). The latter factor—
incorporation of correction for detection
bias—should systematically result in
greater abundance predictions. For these
reasons, the Roberts et al. (2016)
estimates are generally more realistic
and, for these purposes, represent the
best available information. For purposes
of assessing estimated exposures
relative to abundance—used in this case
to understand the scale of the predicted
takes compared to the population—
NMFS generally believes that the
Roberts et al. (2016) abundance
predictions are most appropriate
because they were used to generate the
exposure estimates and therefore
provide the most relevant comparison.
Roberts et al. (2016) represents the best
available scientific information
regarding marine mammal occurrence
and distribution in the Gulf of Mexico.
As a further illustration of the
distinction between the SARs and
model-predicted abundance estimates,
the current NMFS stock abundance
estimates for most GOM species are
based on direct observations from
shipboard surveys conducted in 2009
(from the 200-m isobath to the edge of
the U.S. EEZ) and not corrected for
detection bias, whereas the exposure
estimates presented herein for those
species are based on the abundance
predicted by a density surface model
informed by observations from surveys
conducted over approximately 20 years
and covariates associated at the
observation level. To directly compare
the estimated exposures predicted by
the outputs of the Roberts et al. (2016)
model to NMFS’ SAR abundance would
therefore not be meaningful.
Biologically Important Areas (BIA)—
As part of our description of the
environmental baseline, we discuss any
known areas of importance as marine
mammal habitat. These areas may
include designated critical habitat for
ESA-listed species (as defined by
section 3 of the ESA) or other known
areas not formally designated pursuant
to any statute or other law. Important
areas may include areas of known
importance for reproduction, feeding, or
migration, or areas where small and
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resident populations are known to
occur.
Although there is no designated
critical habitat for marine mammal
species in the specified geographical
region, BIAs for marine mammals are
recognized. For example, the GOM
Bryde’s whale is a very small
population that is genetically distinct
from other Bryde’s whales and not
genetically diverse within the GOM
(Rosel and Wilcox, 2014). Further, the
species is typically observed only
within a narrowly circumscribed area
within the eastern GOM. Therefore, this
area is described as a year-round BIA by
LaBrecque et al. (2015). Although
survey effort has covered all oceanic
waters of the U.S. GOM, whales were
observed only between approximately
the 100- and 300-m isobaths in the
eastern GOM from the head of the De
Soto Canyon (south of Pensacola,
Florida) to northwest of Tampa Bay,
Florida (Maze-Foley and Mullin, 2006;
Waring et al., 2016; Rosel and Wilcox,
2014; Rosel et al., 2016). NOAA
subsequently conducted a status review
of the GOM Bryde’s whale (Rosel et al.,
2016). The review expanded this
description by stating that, due to the
depth of some sightings, the area is
more appropriately defined to the 400m isobath and westward to Mobile Bay,
Alabama, in order to provide some
buffer around the deeper sightings and
to include all sightings in the
northeastern GOM. However, the
recorded Bryde’s whale shipboard and
aerial survey sightings between 1989
and 2015 have mainly fallen within the
BIA described by LaBreque et al. (2015).
The entirety of this area is now
excluded from the scope of this rule
following BOEM’s update to that scope.
LaBrecque et al. (2015) also described
eleven year-round BIAs for small and
resident BSE bottlenose dolphin
populations in the GOM. Additional
study would likely allow for
identification of additional BIAs
associated with other GOM BSE dolphin
stocks.
Deepwater Horizon Oil Spill—In 2010
the Macondo well blowout and
explosion aboard the Deepwater
Horizon drilling rig (also known as the
Deepwater Horizon explosion, oil spill,
and response; hereafter referred to as the
DWH oil spill) caused oil, natural gas,
and other substances to flow into the
GOM for 87 days before the well was
sealed. Total oil discharge was
estimated at 3.19 million barrels (134
million gallons), resulting in the largest
marine oil spill in history (DWH NRDA
Trustees, 2016). In addition, the
response effort involved extensive
application of dispersants at the seafloor
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and at the surface, and controlled
burning of oil at the surface was also
used extensively as a response
technique. The oil, dispersant, and burn
residue compounds present ecological
challenges in the region. NMFS
discussed the impacts of the DWH oil
spill on marine mammals in detail in
the notice of proposed rulemaking (83
FR 29212; June 22, 2018) and we refer
the reader to that document for
additional detail.
At its maximum extent, oil covered
over 40,000 km2 of ocean. Cumulatively,
over the course of the spill, oil was
detected on over 112,000 km2 of ocean.
Currents, winds, and tides carried these
surface oil slicks to shore, fouling more
than 2,100 km of shoreline, including
beaches, bays, estuaries, and marshes
from eastern Texas to the Florida
Panhandle. In addition, some lighter oil
compounds evaporated from the slicks,
exposing air-breathing organisms like
marine mammals to noxious fumes at
the sea surface.
The Oil Pollution Act requires that a
natural resource damage assessment
(NRDA) be conducted following oil
pollution incidents. An injury
assessment undertaken as part of the
NRDA first requires a determination of
whether an incident injured natural
resources. Trustees assessing natural
resource injuries must establish that a
pathway existed from the oil discharge
to the resource, confirm that resources
were exposed to the discharge, and
evaluate the adverse effects that
occurred as a result of the exposure (or
response activities). Subsequently, the
assessment requires injury
quantification (including degree and
spatiotemporal extent), essentially by
comparing the post-event conditions
with the pre-event baseline. For a fuller
overview of the injury assessment
process in this case, please see
Takeshita et al. (2017). Critical
pathways of exposure for marine
mammals included the contaminated
water column, where they swim and
capture prey; the surface slick at the air
to water interface, where they breathe,
rest, and swim; and contaminated
sediment, where they forage and capture
prey.
DWH oil was found to cause problems
with the regulation of stress hormone
secretion from adrenal cells and kidney
cells, which will affect an animal’s
ability to regulate body functions and
respond appropriately to stressful
situations, thus leading to reduced
fitness. Bottlenose dolphins living in
habitats contaminated with DWH oil
showed signs of adrenal dysfunction,
and dead, stranded dolphins from areas
contaminated with DWH oil had smaller
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adrenal glands (Schwacke et al., 2014a;
Venn-Watson et al., 2015b). Other
factors were ruled out as a primary
cause for the high prevalence of adverse
health effects, reproductive failures, and
disease in stranded animals. When all of
the data were considered together, the
DWH oil spill was determined to be the
only reasonable cause for the full suite
of observed adverse health effects.
Due to the difficulty of investigating
marine mammals in pelagic
environments and across the entire
region impacted by the event, the injury
assessment focused on health
assessments conducted on bottlenose
dolphins in nearshore habitats and used
these populations as case studies for
extrapolating to coastal and oceanic
populations that received similar or
worse exposure to DWH oil, with
appropriate adjustments made for
differences in behavior, anatomy,
physiology, life histories, and
population dynamics among species.
Investigators then used a population
modeling approach to capture the
overlapping and synergistic
relationships among the metrics for
injury, and to quantify the entire scope
of DWH marine mammal injury to
populations into the future, expressed
as ‘‘lost cetacean years’’ due to the DWH
oil spill (which represents years lost due
to premature mortality as well as the
resultant loss of reproductive output).
This approach allowed for consideration
of long-term impacts resulting from
immediate losses and reproductive
failures in the few years following the
spill, as well as expected persistent
impacts on survival and reproduction
for exposed animals well into the future
(Takeshita et al., 2017). For a more
detailed overview of the injury
quantification for these stocks and their
post-DWH population trajectory, please
see Schwacke et al. (2017), and for full
details of the overall injury
quantification, see DWH MMIQT (2015).
The results of the quantification
exercise for each affected shelf and
oceanic stock, and for northern and
western coastal stocks of bottlenose
dolphin, are presented in Table 5. This
is likely a conservative estimate of
impacts, because: (1) Shelf and oceanic
species experienced long exposures (up
to 90 days) to very high concentrations
of fresh oil and a diverse suite of
response activities, while estuarine
dolphins were not exposed until later in
the spill period and to weathered oil
products at lower water concentrations;
(2) oceanic cetaceans dive longer and to
deeper depths, and it is possible that the
types of lung injuries observed in
estuarine dolphins may be more severe
for oceanic cetaceans; and (3) cetaceans
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in deeper waters were exposed to very
high concentrations of volatile gas
compounds at the water’s surface near
the wellhead. No analysis was
performed for Fraser’s dolphins or killer
whales; although they are present in the
GOM, sightings are rare and there were
no historical sightings in the oil spill
footprint during the surveys used in the
quantification process. These stocks
5393
were likely injured, but no information
is available on which to base a
quantification effort.
TABLE 5—SUMMARY OF MODELED EFFECTS OF DWH OIL SPILL
% Population
exposed to
oil (95% CI)
Common name
Bryde’s whale ...........................................
Sperm whale ............................................
Kogia spp. ................................................
Beaked whales .........................................
Rough-toothed dolphin .............................
Bottlenose dolphin, oceanic .....................
Bottlenose dolphin, northern coastal .......
Bottlenose dolphin, western coastal ........
Shelf dolphins a ........................................
Clymene dolphin ......................................
Pantropical spotted dolphin .....................
Spinner dolphin ........................................
Striped dolphin .........................................
Risso’s dolphin .........................................
Melon-headed whale ................................
Pygmy killer whale ...................................
False killer whale .....................................
Short-finned pilot whale ...........................
% Population
killed
(95% CI)
48 (23¥100)
16 (11¥23)
15 (8¥29)
12 (7¥22)
41 (16¥100)
10 (5¥10)
82 (55¥100)
23 (16¥32)
13 (9¥19)
7 (3¥15)
20 (15¥26)
47 (24¥91)
13 (8¥22)
8 (5¥13)
15 (6¥36)
15 (7¥33)
18 (7¥48)
6 (4¥9)
17 (7¥24)
6 (2¥8)
5 (2¥7)
4 (2¥6)
14 (6¥20)
3 (1¥5)
38 (26¥58)
1 (1¥2)
4 (2¥6)
2 (1¥4)
7 (3¥10)
16 (7¥23)
5 (2¥7)
3 (1¥4)
5 (2¥7)
5 (2¥8)
6 (3¥9)
2 (1¥3)
% Females
with
reproductive
failure
(95% CI)
22 (10¥31)
7 (3¥10)
7 (3¥10)
5 (3¥8)
19 (9¥26)
5 (2¥6)
37 (17¥53)
10 (5¥15)
6 (3¥8)
3 (2¥5)
9 (4¥13)
21 (10¥30)
6 (3¥9)
3 (2¥5)
7 (3¥10)
7 (3¥10)
8 (4¥12)
3 (1¥4)
% Population
with adverse
health effects
(95% CI)
18 (7¥28)
6 (2¥9)
6 (2¥9)
4 (2¥7)
15 (6¥23)
4 (1¥6)
30 (11¥47)
8 (3¥13)
5 (2¥7)
3 (1¥4)
7 (3¥11)
17 (6¥27)
5 (2¥8)
3 (1¥4)
6 (2¥9)
6 (2¥9)
7 (3¥11)
2 (1¥3)
% Maximum
population
reduction
(95% CI)
¥22
¥7
¥6
¥6
¥17
¥4
¥50 (32¥73)
¥5 (3¥9)
¥3
¥3
¥9
¥23
¥6
¥3
¥7
¥7
¥9
¥3
Years to
recovery
(95% CI) b
69
21
11
10
54
n/a
39 (23¥76)
n/a
n/a
n/a
39
105
14
n/a
29
29
42
n/a
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Modified from DWH NRDA Trustees (2016).
CI = confidence interval. No CI was calculated for population reduction or years to recovery for shelf or oceanic stocks.
a ‘‘Shelf dolphins’’ includes Atlantic spotted dolphins and the shelf stock of bottlenose dolphins (20–200 m water depth). These two species
were combined because the abundance estimate used in population modeling was derived from aerial surveys and the species could not generally be distinguished from the air.
b It is not possible to calculate YTR for stocks with maximum population reductions of less than or equal to 5 percent.
Coastal and oceanic marine mammals
were injured by exposure to oil from the
DWH spill. Nearly all of the stocks that
overlap with the oil spill footprint have
demonstrable, quantifiable injuries, and
the remaining stocks (for which there is
no quantifiable injury) were also likely
injured, though there is not currently
enough information to make a
determination. Injuries included
elevated mortality rates, reduced
reproduction, and disease. Due to these
effects, affected populations may require
decades to recover absent successful
efforts at restoration (e.g., DWH NRDA
Trustees, 2017). The ability of the stocks
to recover and the length of time
required for that recovery are tied to the
carrying capacity of the habitat, and to
the degree of other population
pressures. NMFS treats the effects of the
DWH oil spill as part of the baseline in
considering the likely resilience of these
populations to the effects of the
activities considered in this regulatory
framework.
Unusual Mortality Events (UME)—A
UME is defined under Section 410(6) of
the MMPA as ‘‘a stranding that is
unexpected; involves a significant dieoff of any marine mammal population;
and demands immediate response.’’
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From 1991 to the present, there have
been fourteen formally recognized
UMEs affecting marine mammals in the
region and involving species under
NMFS’ jurisdiction. These have
primarily impacted coastal bottlenose
dolphins, with multiple UMEs
determined to have resulted from
biotoxins and one from infectious
disease. One relevant UME was declared
since publication of the notice of
proposed rulemaking and is discussed
below.
Most significantly, a UME affecting
multiple cetacean species in the
northern GOM occurred from 2010–
2014. NMFS discussed this UME in the
notice of proposed rulemaking (83 FR
29212; June 22, 2018). Please see that
document for additional information
regarding the 2010–2014 UME.
Additional information on the UME is
also available online at:
www.fisheries.noaa.gov/national/
marine-life-distress/2010-2014cetacean-unusual-mortality-eventnorthern-gulf-mexico. In summary, the
event included all cetaceans stranded
during this time in Alabama,
Mississippi, and Louisiana and all
cetaceans other than bottlenose
dolphins stranded in the Florida
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Panhandle (Franklin County through
Escambia County), with a total of 1,141
cetaceans stranded or reported dead
offshore. For reference, the same area
experienced a normal average of 75
strandings per year from 2002–09 (Litz
et al., 2014). The majority of stranded
animals were bottlenose dolphins,
though at least ten additional species
were reported as well. Since not all
cetaceans that die wash ashore where
they may be found, the number reported
stranded is likely a fraction of the total
number of cetaceans that died during
the UME. There was also an increase in
strandings of stillborn and newborn
dolphins (Colegrove et al., 2016). The
UME investigation and the Deepwater
Horizon Natural Resource Damage
Assessment determined that the DWH
oil spill (discussed above) is the most
likely explanation of the persistent,
elevated stranding numbers in the
northern GOM after the 2010 spill. The
evidence to date supports that exposure
to hydrocarbons released during the
DWH oil spill was the most likely
explanation of adrenal and lung disease
in dolphins, which has contributed to
increased deaths of dolphins living
within the oil spill footprint and
increased fetal loss. The longest and
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most prolonged stranding cluster was in
Barataria Bay, Louisiana in 2010–11,
followed by Mississippi and Alabama in
2011, consistent with timing and spatial
distribution of oil, while the number of
deaths was not elevated for areas that
were not as heavily oiled. Subsequent
health assessments of live dolphins
from Barataria Bay and comparison to a
reference population found significantly
increased adrenal disease, lung disease,
and poor health, while histological
evaluations of samples from dead
stranded animals from within and
outside the UME area found that UME
animals were more likely to have lung
and adrenal lesions and to have primary
bacterial pneumonia, which caused or
contributed significantly to death
(Schwacke et al., 2014a, 2014b; VennWatson et al., 2015b). The chronic
adrenal gland and lung diseases
identified in stranded UME dolphins are
consistent with exposure to petroleum
compounds (Venn-Watson et al.,
2015b). Colegrove et al. (2016) found
that the increase in perinatal strandings
resulted from late-term pregnancy
failures and development of in utero
infections likely caused by chronic
illnesses in mothers who were exposed
to oil.
While the number of dolphin
mortalities in the area decreased after
the peak from March 2010-July 2014, it
does not indicate that the effects of the
oil spill on these populations have
ended. Researchers still saw evidence of
chronic lung disease and adrenal
impairment four years after the spill (in
July 2014) and saw evidence of failed
pregnancies in 2015 (Smith et al., 2017).
These follow-up studies found a yearly
mortality rate for Barataria Bay dolphins
of roughly 13 percent (as compared to
annual mortality rates of 5 percent or
less that have been previously reported
for other dolphin populations) and
found that only 20 percent of pregnant
dolphins produced viable calves
(compared with 83 percent in a
reference population) (Lane et al., 2015;
McDonald et al., 2017). In addition,
compromised health may make
dolphins more susceptible to additional
environmental stressors.
Since the publication of the proposed
rule, another UME involving bottlenose
dolphins in the northern GOM was
declared. Elevated bottlenose dolphin
strandings occurred in Louisiana,
Mississippi, Alabama, and the
panhandle of Florida (Alabama border
through Taylor County) from February
1, 2019, through November 30, 2019. A
total of 337 confirmed strandings were
documented, with a majority occurring
from February through May. Excluding
prior UMEs, the annual average for
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February through May in the affected
area is 57 dolphins; at least 260
standings were documented during this
period in 2019. The cause of the UME
was determined to be environmentally
driven by exposure to low salinity
waters resulting from extreme
freshwater discharge from watersheds
that drain into the GOM, including
rivers in Florida, Alabama, Mississippi
and Louisiana. This unprecedented
amount of freshwater discharge during
the winter, spring, and summer months
of 2019 resulted in a drop in salinity
levels across the coastally associated
waters in the region. Prolonged
exposure to low salinity water has been
documented to have harmful health
impacts on bottlenose dolphins, ranging
from skin lesions and serum electrolyte
abnormalities to acute mortality. The
location of the UME and the dolphin
stocks affected, including the western
and northern coastal stocks of
bottlenose dolphin, are the same as
those impacted by the 2010–2014 UME.
For additional information, please visit
www.fisheries.noaa.gov/national/
marine-life-distress/2019-bottlenosedolphin-unusual-mortality-event-alongnorthern-gulf.
Marine Mammal Hearing
Hearing is the most important sensory
modality for marine mammals
underwater, and exposure to
anthropogenic sound can have
deleterious effects. To appropriately
assess the potential effects of exposure
to sound, it is necessary to understand
the frequency ranges that marine
mammals are able to hear. Current data
indicate that not all marine mammal
species have equal hearing capabilities
(e.g., Richardson et al., 1995; Wartzok
and Ketten, 1999; Au and Hastings,
2008). To reflect this, Southall et al.
(2007) recommended that marine
mammals be divided into functional
hearing groups based on directly
measured or estimated hearing ranges
on the basis of available behavioral
response data, audiograms derived
using auditory evoked potential
techniques, anatomical modeling, and
other data. Note that no direct
measurements of hearing ability have
been successfully completed for
mysticetes (i.e., low-frequency
cetaceans). NMFS (2018) describes
generalized hearing ranges for these
marine mammal hearing groups.
Generalized hearing ranges were chosen
based on the approximately 65 dB
threshold from the normalized
composite audiograms, with the
exception for lower limits for lowfrequency cetaceans where the lower
bound was deemed to be biologically
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implausible and the lower bound from
Southall et al. (2007) retained. The
functional groups and the associated
frequencies are indicated below (note
that these frequency ranges correspond
to the range for the composite group,
with the entire range not necessarily
reflecting the capabilities of every
species within that group):
• Low-frequency cetaceans
(mysticetes): Generalized hearing is
estimated to occur between
approximately 7 Hz and 35 kHz;
• Mid-frequency cetaceans (larger
toothed whales, beaked whales, and
most delphinids): Generalized hearing is
estimated to occur between
approximately 150 Hz and 160 kHz;
• High-frequency cetaceans
(porpoises, river dolphins, and members
of the genera Kogia and
Cephalorhynchus; including two
members of the genus Lagenorhynchus,
on the basis of recent echolocation data
and genetic data): Generalized hearing is
estimated to occur between
approximately 275 Hz and 160 kHz.
For more detail concerning these
groups and associated frequency ranges,
please see NMFS (2018) for a review of
available information. Twenty-one
species of cetacean have the reasonable
potential to co-occur with the proposed
survey activities. Please refer to Table 4.
Of the cetacean species that may be
present, one is classified as a lowfrequency cetacean (i.e., the Bryde’s
whale), 18 are classified as midfrequency cetaceans (i.e., all delphinid
and ziphiid species and the sperm
whale), and two are classified as highfrequency cetaceans (i.e., Kogia spp.).
Potential Effects of the Specified
Activities on Marine Mammals and
Their Habitat
In NMFS’ notice of proposed
rulemaking (83 FR 29212; June 22,
2018), this section included a
comprehensive summary and
discussion of the ways that components
of the specified activity may impact
marine mammals and their habitat,
including general background
information on sound and specific
discussion of potential effects to marine
mammals from noise produced through
use of airgun arrays. We incorporate by
reference that information and do not
repeat that discussion here, instead
referring the reader to the notice of
proposed rulemaking.
The Estimated Take section later in
this document includes a quantitative
analysis of the number of individuals
that are expected to be taken by the
specified activity. The Negligible Impact
Analysis and Determinations section
includes an analysis of how these
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activities will impact marine mammals
and considers the content of this
section, the Estimated Take section, and
the Mitigation section, to draw
conclusions regarding the likely impacts
of these activities on the reproductive
success or survivorship of individuals
and from that on the affected marine
mammal populations.
Description of Active Acoustic Sound
Sources
In the notice of proposed rulemaking,
this section contained a brief technical
background on sound, the
characteristics of certain sound types,
and on metrics used in the proposal
inasmuch as the information is relevant
to the specified activity and to a
discussion of the potential effects of the
specified activity on marine mammals
found later in this document. Here, we
summarize key information relating to
terminology used in this notice.
Amplitude (or ‘‘loudness’’) of sound
is typically described using the relative
unit of the decibel (dB). A sound
pressure level (SPL) in dB is described
as the ratio between a measured
pressure and a reference pressure (for
underwater sound, this is 1 microPascal
(mPa)). The source level (SL) represents
the SPL referenced at a distance of 1 m
from the source (referenced to 1 mPa),
while the received level is the SPL at
the listener’s position (referenced to 1
mPa).
Root mean square (rms) is the
quadratic mean sound pressure over the
duration of an impulse. This
measurement is often used in the
context of discussing behavioral effects,
in part because behavioral effects,
which often result from auditory cues,
may be better expressed through
averaged units than by peak pressures.
Sound exposure level (SEL; represented
as dB re 1 mPa2¥s) represents the total
energy contained within a pulse, and
considers both intensity and duration of
exposure. Peak sound pressure (also
referred to as zero-to-peak sound
pressure or 0–p) is the maximum
instantaneous sound pressure
measurable in the water at a specified
distance from the source, and is
represented in the same units as the rms
sound pressure. Another common
metric is peak-to-peak sound pressure
(pk-pk), which is the algebraic
difference between the peak positive
and peak negative sound pressures.
Peak-to-peak pressure is typically
approximately 6 dB higher than peak
pressure (Southall et al., 2007).
As described in more detail in the
notice of proposed rulemaking, airgun
arrays are in a general sense considered
to be omnidirectional sources of pulsed
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noise. Pulsed sound sources (as
compared with non-pulsed sources)
produce signals that are brief (typically
considered to be less than one second),
broadband, atonal transients (ANSI,
1986, 2005; Harris, 1998; NIOSH, 1998;
ISO, 2003) and occur either as isolated
events or repeated in some succession.
Pulsed sounds are all characterized by
a relatively rapid rise from ambient
pressure to a maximal pressure value
followed by a rapid decay period that
may include a period of diminishing,
oscillating maximal and minimal
pressures, and generally have an
increased capacity to induce physical
injury as compared with sounds that
lack these features. Airguns produce
sound with energy in a frequency range
from about 10–2,000 Hz, with most
energy radiated at frequencies below
200 Hz. Although the amplitude of the
acoustic wave emitted from the source
is equal in all directions (i.e.,
omnidirectional), airgun arrays do
possess some directionality due to
different phase delays between guns in
different directions. Airgun arrays are
typically tuned to maximize
functionality for data acquisition
purposes, meaning that sound
transmitted in horizontal directions and
at higher frequencies is minimized to
the extent possible.
Acoustic sources used for highresolution geophysical (HRG) surveys
generally produce higher frequency
signals with highly directional beam
patterns. These sources are generally
considered to be intermittent, with
typically brief signal durations.
Boomers, considered to be impulsive
sources, generate a high-amplitude
broadband (100 Hz-10 kHz) acoustic
pulse with high downward directivity,
though may be considered
omnidirectional at frequencies below 1
kHz. Other typical HRG sources are
considered non-impulsive. Sub-bottom
profiler systems generally project a
chirp pulse spanning an operatorselectable frequency band, usually
between 1 to 20 kHz, with a single beam
directed vertically down. Multibeam
echosounders use an array of
transducers that project a highfrequency, fan-shaped beam under the
hull of a survey ship and perpendicular
to the direction of motion. Side-scan
sonars use two transducers to project
high-frequency beams that are usually
wide in the vertical plane (50°–70°) and
very narrow in the horizontal plane (less
than a few degrees). Other, similar
impulsive or non-impulsive sources
may be used in conducting shallow
penetration or HRG surveys.
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Acoustic Habitat
NMFS also included a detailed
discussion and analysis of potential
impacts to acoustic habitat. Acoustic
habitat is the soundscape—which
encompasses all of the sound present in
a particular location and time, as a
whole—when considered from the
perspective of the animals experiencing
it. Animals listen for sounds produced
by conspecifics (communication during
feeding, mating, and other social
activities), other animals (finding prey
or avoiding predators), and the physical
environment (finding suitable habitats,
navigating). Together, sounds made by
animals and the geophysical
environment (e.g., produced by
earthquakes, lightning, wind, rain,
waves) make up the natural
contributions to the total acoustics of a
place. These acoustic conditions,
termed acoustic habitat, are one
attribute of an animal’s total habitat.
That discussion summarized a report
titled ‘‘Cumulative and Chronic Effects
in the Gulf of Mexico: Estimating
Reduction of Listening Area and
Communication Space due to Seismic
Activities,’’ (‘‘Cumulative and Chronic
Effects report’’) as well as a subsequent
addendum to the report presenting
additional analysis relating to sperm
whales. The initial report (originally
presented as Appendix K in BOEM
(2017)) as well as the addendum
((hereafter, ‘‘the CCE report’’), are
available online at
www.fisheries.noaa.gov/action/
incidental-take-authorization-oil-andgas-industry-geophysical-surveyactivity-gulf-mexico. The CCE report
presented a first-order cumulative and
chronic effects assessment for noise
produced by oil and gas exploration
activities in the U.S. GOM.
The term ‘‘listening area’’ refers to the
region of ocean over which sources of
sound can be detected by an animal at
the center of the space. Loss of
communication space concerns the area
over which a specific animal signal,
used to communicate with conspecifics
in biologically-important contexts (e.g.,
foraging, mating), can be heard, in
noisier relative to quieter conditions
(Clark et al., 2009). Lost listening area
concerns the more generalized
contraction of the range over which
animals would be able to detect a
variety of signals of biological
importance, including eavesdropping on
predators and prey (Barber et al., 2009).
Implications for acoustic masking (i.e.,
when a sound interferes with or masks
the ability of an animal to detect a signal
of interest that is above the absolute
hearing threshold; see notice of
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proposed rulemaking at 29239 for
explanation of masking) and reduced
communication space resulting from
noise produced by airgun surveys in the
GOM are expected to be particularly
heightened for animals that actively
produce low-frequency sounds or whose
hearing is attuned to lower frequencies
(i.e., Bryde’s whales).
Acoustic modeling was conducted for
ten locations (‘‘receiver sites’’) within
the study area to examine aggregate
noise produced over a full, generic year.
The locations of the receiver sites were
chosen to reflect areas of biological
importance to cetaceans, areas of high
densities of cetaceans, and areas of key
biological diversity. The CCE report
analyzed multiple scenarios, including a
baseline scenario in which no
geophysical surveys are conducted and
noise consists of natural sounds and a
minimum estimate of commercial vessel
noise; a survey activity scenario in
which projected activities were
uniformly distributed throughout the
study area, with the exception of coastal
waters from February to May; and a
closure scenario in which no activities
are conducted in certain restriction
areas, 25 percent of the activity that
would have occurred in the restriction
areas is redistributed into nonrestriction areas of the same activity
zone, and 75 percent of the activities
that would have occurred in the
restriction areas are not conducted at
all. For additional methodological
details, see discussion in the notice of
proposed rulemaking or the CCE report.
Regarding sperm whales, the analysis
shows that the survey activities do not
significantly contribute to the
soundscape in the frequency band
relevant for their lower-frequency slowclicks, and that there will be no
significant change in communication
space for sperm whales. Because other
sperm whale calls are higher-frequency,
they would not be expected to be
affected. Please see the CCE report for
further discussion of the findings for
sperm whales. The remaining
discussion that follows is in reference to
the findings for Bryde’s whales and to
general findings for other hearing
groups.
The methods used in the CCE report
were meant to average the conditions
generated by low-frequency dominant
noise sources throughout a full year,
during which animals of key
management interest rely on habitats
within the study area. Considered as a
complement to assessments of the acute
effects of the same types of noise
sources in the same region (discussed
below in the Estimated Take section),
the CCE assessment estimates noise
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produced by the same sources over
much larger spatial scales, and
considers how the summation of noise
from these sources relates to levels
without the proposed activity (ambient).
The lost listening area method
calculates a fractional reduction in
listening area due to the addition of
anthropogenic noise to ambient noise.
Results are presented as a percentage of
the original listening area remaining due
to the increase in noise levels relative to
no activity and between activity
scenarios. The communication space
assessment provides relative losses of
communication space (in both areas and
percentages) between the activity
scenarios.
At most sites, lost listening area was
greater for deeper waters than for
shallower waters, which is attributed to
the downward-refracting sound speed
profile near the surface, caused by the
thermocline, which steers sound to
deeper depths. Shallow water noise
levels were reduced due to surface
interactions that increase transmission
loss, particularly for low frequencies.
Listening area reductions were also
generally most severe when weighted
for low-frequency hearing cetaceans.
Both low- and mid-frequency weighted
losses were high in the Mississippi
Canyon, while only low-frequency
weighted values were high for the De
Soto Canyon. Both of these sites are
considered important to sperm whales
as well as other deep-diving
odontocetes. These modeling results
suggest that accumulations of noise
from survey activities below 5 kHz and
often heightened at depth could be
degrading the ability of animals that
forage at great depths in the GOM to use
acoustic cues to find prey as well as to
maintain conspecific contact.
Comparison between results provided
for the two metrics applied in the CCE
report highlights important interpretive
differences for evaluating the biological
implications of background noise. The
strength of the communication space
approach is that it evaluates potential
contractions in the availability of a
signal of documented importance to a
population of animals of key
management interest in the region. In
this case, losses of communication
space for Bryde’s whales were estimated
to be higher in eastern and central GOM
canyons and shelf break areas. In
contrast, relative maintenance of
listening area and communication space
was seen within the Bryde’s whale core
habitat area in the eastern GOM (an area
that has since been removed from
consideration through this rule). In
areas where larger amounts of survey
activity were projected, significant loss
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of low-frequency listening area and
communication space for Bryde’s whale
calls was estimated, though we
emphasize that these are not areas
where Bryde’s whales are expected to
occur.
The CCE report is described here in
order to summarize information
presented in the proposed rule
regarding potential longer-term and
wider-range noise effects from sources
such as airguns. Please see the notice of
proposed rulemaking, as well as the
CCE report and addendum, for
additional information.
Estimated Take
This section provides an estimate of
the number and type of incidental takes
that may be expected to occur under the
specified activity (as it has been revised
in scope), which informed NMFS’
negligible impact determination.
Realized incidental takes would be
determined by the actual levels of
activity at specific times and places that
occur under any issued LOAs.
Except with respect to certain
activities not pertinent here, section
3(18) of the MMPA defines
‘‘harassment’’ as: Any act of pursuit,
torment, or annoyance which (i) has the
potential to injure a marine mammal or
marine mammal stock in the wild (Level
A harassment); or (ii) has the potential
to disturb a marine mammal or marine
mammal stock in the wild by causing
disruption of behavioral patterns,
including, but not limited to, migration,
breathing, nursing, breeding, feeding, or
sheltering (Level B harassment).
Harassment is the only type of take
expected to result from these activities.
Anticipated takes would primarily be
by Level B harassment, as use of the
described acoustic sources, particularly
airgun arrays, is likely to disrupt
behavioral patterns of marine mammals.
There is also some potential for auditory
injury (Level A harassment) to result for
low- and high-frequency species due to
the size of the predicted auditory injury
zones for those species. NMFS does not
expect auditory injury to occur for midfrequency species, as discussed in
greater detail on the notice of proposed
rulemaking (83 FR 29212; June 22, 2018)
and in responses to public comments.
The required mitigation and monitoring
measures are expected to minimize the
severity of such taking to the extent
practicable. It is unlikely that lethal
takes would occur even in the absence
of the mitigation and monitoring
measures, and no such takes are
anticipated or will be authorized. Below
we summarize how the take that may be
authorized was estimated using acoustic
thresholds, sound field modeling, and
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marine mammal density data. Detailed
discussion of all facets of the take
estimation process was provided in the
notice of proposed rulemaking (83 FR
29212; June 22, 2018), and nothing has
changed since that time. Therefore, that
full discussion is not repeated. Please
see that notice, and associated
companion documents available online,
for additional detail.
Acoustic Thresholds
NMFS uses acoustic thresholds that
identify the received level of
underwater sound above which exposed
marine mammals generally would be
reasonably expected to exhibit
disruption of behavioral patterns (Level
B harassment) or to incur permanent
threshold shift (PTS) of some degree
(Level A harassment).
Level B Harassment—Although
available data are consistent with the
basic concept that louder sounds evoke
more significant behavioral responses
than softer sounds, defining precise
sound levels that will potentially
disrupt behavioral patterns is difficult
because responses depend on the
context in which the animal receives the
sound, including an animal’s behavioral
mode when it hears sounds (e.g.,
feeding, resting, or migrating), prior
experience, and biological factors (e.g.,
age and sex). Some species, such as
beaked whales, are known to be more
highly sensitive to certain
anthropogenic sounds than other
species. Other contextual factors, such
as signal characteristics, distance from
the source, duration of exposure, and
signal to noise ratio, may also help
determine response to a given received
level of sound. Therefore, levels at
which responses occur are not
necessarily consistent and can be
difficult to predict (Southall et al., 2007;
Ellison et al., 2012; Bain and Williams,
2006). Typically, and especially in cases
where PTS is predicted, NMFS
anticipates that some number of
individuals may incur temporary
threshold shift (TTS) (considered Level
B harassment). However, it is not
necessary to separately quantify those
takes, as it is unlikely that an individual
marine mammal would be exposed at
the levels and duration necessary to
incur TTS without also being exposed to
the levels associated with behavioral
harassment and, therefore, NMFS
expects any potential TTS takes to be
captured by the estimated takes by
behavioral harassment.
Based on the practical need to use a
relatively simple threshold based on
available information that is both
predictable and measurable for most
activities, NMFS has historically used a
generalized acoustic threshold based on
received level to estimate the onset of
Level B harassment. These thresholds
are 160 dB rms (intermittent sources,
which include impulsive sources) and
120 dB rms (continuous sources).
Airguns are impulsive sound sources
and electromechanical sources used for
HRG surveys are intermittent sources.
Therefore, the 160 dB rms threshold has
typically been used in evaluating effects
from the sources planned for use in the
specified activities. However, in the
notice of proposed rulemaking, NMFS
identified a more complex probabilistic
risk function for use in evaluating the
potential effects of the specified activity
considered herein. That function,
described in Wood et al. (2012), is better
reflective of available scientific
information (as discussed in detail in
the notice of proposed rulemaking, as
well as in comment responses provided
earlier in this preamble). Such an
approach takes the fundamental step of
5397
acknowledging the potential for Level B
harassment at exposures to received
levels below 160 dB rms (as well as the
potential that animals exposed to
received levels above 160 dB rms will
not respond in ways constituting Level
B harassment). The approach described
by Wood et al. (2012) also accounts for
differential hearing sensitivity by
incorporating frequency-weighting
functions. The analysis of Gomez et al.
(2016) indicates that behavioral
responses in cetaceans are best
explained by the interaction between
sound source type and functional
hearing group. Southall et al. (2007)
proposed auditory weighting functions
for species groups based on known and
assumed hearing ranges (Type I).
Although newer filters are better
designed to predict the onset of auditory
injury (as discussed below and used for
evaluation of potential Level A
harassment), the broader Type I filters
were retained for use in evaluating
potential behavioral disturbance in
conjunction with the Wood et al. (2012)
probabilistic response function.
NMFS received public comments on
this topic, including some criticizing the
proposed use of the Wood et al. (2012)
risk function. We responded to all
comments received on this topic and, in
addition to the more detailed discussion
provided in the Estimated Take section
of the notice of proposed rulemaking,
we provide detailed discussion of these
concerns in the responses to comments,
provided earlier in this preamble. NMFS
retains use of the Wood et al. (2012)
approach as the basis for estimating take
and considering the effects of the
specified activity on marine mammal
behavior. The Level B harassment
criteria upon which the analysis
presented herein is based are presented
in Table 6.
TABLE 6—BEHAVIORAL EXPOSURE CRITERIA
Probability of response to frequency-weighted rms SPL
Group
120
(%)
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Beaked whales ................................................................................................
All other species ..............................................................................................
Level A Harassment—NMFS’
Technical Guidance for Assessing the
Effects of Anthropogenic Sound on
Marine Mammal Hearing (NMFS, 2018)
(2018 Revised Technical Guidance)
identifies dual criteria to assess the
potential for auditory injury (Level A
harassment) to occur for different
marine mammal groups (based on
hearing sensitivity) as a result of
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140
(%)
50
n/a
exposure to noise. The 2018 Revised
Technical Guidance identifies the
received levels, or thresholds, above
which individual marine mammals are
predicted to experience changes in their
hearing sensitivity for all underwater
anthropogenic sound sources and
reflects the best available science on the
potential for noise to affect auditory
sensitivity by:
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160
(%)
90
10
180
(%)
n/a
50
n/a
90
• Dividing sound sources into two
groups (i.e., impulsive and nonimpulsive) based on their potential to
affect hearing sensitivity;
• Choosing metrics that best address
the impacts of noise on hearing
sensitivity, i.e., peak sound pressure
level (peak SPL) (reflects the physical
properties of impulsive sound sources
to affect hearing sensitivity) and
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cumulative sound exposure level (cSEL)
(accounts for not only level of exposure
but also duration of exposure); and
• Dividing marine mammals into
hearing groups and developing auditory
weighting functions based on the
science that indicates that not all marine
mammals hear and use sound in the
same manner.
The premise of the dual criteria
approach is that, while there is no
definitive answer to the question of
which acoustic metric is most
appropriate for assessing the potential
for injury, both the received level and
duration of received signals are
important to an understanding of the
potential for auditory injury. Therefore,
peak SPL is used to define a pressure
criterion above which auditory injury is
predicted to occur, regardless of
exposure duration (i.e., any single
exposure at or above this level is
considered to cause auditory injury),
and cSEL is used to account for the total
energy received over the duration of
sound exposure (i.e., both received level
and duration of exposure) (Southall et
al., 2007, 2019a; NMFS, 2018). As a
general principle, whichever criterion is
exceeded first (i.e., results in the largest
isopleth) would be used as the effective
injury criterion (i.e., the more
precautionary of the criteria). Note that
cSEL acoustic threshold levels
incorporate marine mammal auditory
weighting functions, while peak
pressure thresholds do not (i.e., flat or
unweighted). Weighting functions for
each hearing group (e.g., low-, mid-, and
high-frequency cetaceans) are described
in NMFS (2018).
The 2018 Revised Technical Guidance
recommends 24 hours as a maximum
accumulation period relative to cSEL
thresholds. These thresholds were
developed by compiling and
synthesizing the best available science,
and are provided in Table 7 below. The
references, analysis, and methodology
used in the development of the
thresholds are described in NMFS
(2018), and more information is
available online at:
www.fisheries.noaa.gov/national/
marine-mammal-protection/marinemammal-acoustic-technical-guidance.
TABLE 7—EXPOSURE CRITERIA FOR AUDITORY INJURY
Peak
pressure 1
(dB)
Hearing group
Low-frequency cetaceans ............................................................................................................
Mid-frequency cetaceans .............................................................................................................
High-frequency cetaceans ...........................................................................................................
219
230
202
Cumulative sound exposure
level 2
Impulsive
(dB)
183
185
155
Non-impulsive
(dB)
199
198
173
to 1 μPa; unweighted within generalized hearing range.
to 1 μPa2-s; weighted according to appropriate auditory weighting function. Airguns and the boomer are treated as impulsive
sources; other HRG sources are treated as non-impulsive.
1 Referenced
2 Referenced
NMFS considers these updated
thresholds and associated weighting
functions to be the best available
information for assessing whether
exposure to specific activities is likely
to result in changes in marine mammal
hearing sensitivity.
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Modeling Overview
Zeddies et al. (2015, 2017a) (i.e., ‘‘the
modeling report’’) provides estimates of
the annual marine mammal acoustic
exposure caused by sounds from
geophysical survey activity in the GOM
for ten years of notional activity levels.
Here we provide a brief overview of key
modeling elements, with more detail
provided in the notice of proposed
rulemaking (83 FR 29212; June 22,
2018). For full details of the modeling
effort, the interested reader should see
the report (available online at:
www.fisheries.noaa.gov/action/
incidental-take-authorization-oil-andgas-industry-geophysical-surveyactivity-gulf-mexico).
Initial phases of the modeling effort
involved preliminary modeling of a
typical 3D WAZ survey, which was
simulated at two locations in order to
establish the basic methodological
approach and to provide results used to
evaluate test scenarios that could
influence exposure estimates. We
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discussed each of the six evaluated test
scenarios in the notice of proposed
rulemaking. Please see that discussion
and the modeling report for full details.
The modeling effort produced
exposure estimates computed from
modeled sound levels as received by
simulated animals (animats) in a
specific modeling area. The GOM was
divided into seven modeling zones with
six survey types simulated within each
zone to estimate the potential effects of
each survey. The zones were designed
as described previously (Description of
the Specified Activity; Figure 3)—shelf
and slope waters were divided into
eastern, central, and western zones, plus
a single deep-water zone—to account for
both the geospatial dependence of
acoustic fields and the geographic
variations of animal distributions. The
selected boundaries considered sound
propagation conditions and species
distribution to create regions of
optimized uniformity in both acoustic
environment and animal density.
Survey types included deep penetration
surveys using a large airgun array (2D,
3D NAZ, 3D WAZ, and coil survey
types), shallow penetration surveys
using a single airgun (which were
assumed to be a reasonable proxy for
surveys conducted using a boomer), and
high resolution surveys concurrently
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using a CHIRP sub-bottom profiler, sidescan sonar, and multibeam
echosounder. The results from each
zone were summed to provide GOMwide estimates of take for each marine
mammal species for each survey type
for each notional year. To get these
annual aggregate exposure estimates, 24hr average exposure estimates from each
survey type were multiplied by the
number of expected survey days from
BOEM’s effort projections. Because
these projections are not seasonspecific, surveys were assumed to be
equally likely to occur at any time of the
year and at any location within a given
zone.
Acoustic source emission levels and
directivity of a single airgun and an
airgun array were modeled using JASCO
Applied Sciences’ Airgun Array Source
Model (AASM). AASM is capable of
predicting airgun source levels at
frequencies up to 25 kHz, and produces
a set of notional signatures for each
array element based on array layout;
volume, tow depth, and firing pressure
for each element; and interactions
between different elements in the array.
The signatures are summed to obtain the
far-field source signature of the entire
array in the horizontal plane, which is
then filtered into one third-octave
frequency bands to compute the source
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levels of the array as a function of
frequency band and azimuthal angle in
the horizontal plane (at the source
depth), after which it is considered to be
an azimuth-dependent directional point
source in the far field. Source levels for
high-resolution sources were obtained
from manufacturer’s specifications for
representative sources.
Electromechanical sources were
modeled on the basis of transducer
beam theory, which is often used to
estimate beam pattern of the source in
the absence of field measurements, and
which is described in detail in the
modeling report.
Underwater sound propagation (i.e.,
transmission loss) as a function of range
from each source was modeled using
JASCO’s Marine Operations Noise
Model (MONM) for multiple
propagation radials centered at the
source to yield 3D transmission loss
fields in the surrounding area. The
MONM computes received per-pulse
SEL for directional sources at specified
depths. MONM uses two separate
models to estimate transmission loss. At
frequencies less than 2 kHz, MONM
computes acoustic propagation via a
wide-angle parabolic equation (PE)
solution to the acoustic wave equation
(Collins, 1993), based on a version of the
U.S. Naval Research Laboratory’s Rangedependent Acoustic Model (RAM)
modified to account for an elastic
seabed (Zhang and Tindle, 1995).
MONM–RAM incorporates bathymetry,
underwater sound speed as a function of
depth, and a geoacoustic profile based
on seafloor composition, and accounts
for source horizontal directivity. At
frequencies greater than 2 kHz, MONM
accounts for increased sound
attenuation due to volume absorption at
higher frequencies (Fisher and
Simmons, 1977) with the widely-used
BELLHOP Gaussian beam ray-trace
propagation model (Porter and Liu,
1994). This component incorporates
bathymetry and underwater sound
speed as a function of depth with a
simplified representation of the sea
bottom, as sub-bottom layers have a
negligible influence on the propagation
of acoustic waves with frequencies
above 1 kHz. MONM–BELLHOP
accounts for horizontal directivity of the
source and vertical variation of the
source beam pattern. Both propagation
models account for full exposure from a
direct acoustic wave, as well as
exposure from acoustic wave reflections
and refractions (i.e., multi-path arrivals
at the receiver).
In order to accurately estimate
exposure, a simulation must adequately
cover the various location- and seasonspecific environments. The surveys may
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be conducted at any location within the
planning area and occur at any time of
the year, so simulations must
adequately cover each area and time
period. The seven zones within which
potential exposures were modeled,
corresponding with shelf and slope
environments subdivided into western,
central, and eastern areas, as well as a
single deep zone, were previously
introduced (Figure 3). The subdivision
depth definitions are: Shelf, 0–200 m;
slope, 200–2,000 m; and deep, greater
than 2,000 m. Within each of the seven
zones, a set of representative surveysimulation rectangles for each of the
survey types was defined, with larger
areas for the ‘‘large-area’’ surveys (i.e.,
deep penetration airgun) and smaller
areas for the ‘‘small-area’’ surveys (i.e.,
shallow penetration airgun and HRG). In
Figure 3, the smaller numbered boxes
represent the survey area extents for the
different survey types. The stars
represent acoustic modeling sites along
western, central, and eastern transects
(Figure 3).
A set of 30 sites was selected to
calculate acoustic propagation loss grids
as functions of source, range from the
source, azimuth from the source, and
receiver depth. These were then used as
inputs to the acoustic exposure model.
The environmental parameters and
acoustic propagation conditions
represented by these 30 modeling sites
were chosen to be representative of the
prevalent acoustic propagation
conditions within the survey extents. To
account for seasonal variation in
propagation, winter (most conservative)
and summer (least conservative) were
both used to calculate exposure
estimates. Propagation during spring
and fall was found to be almost
identical to the results for summer, so
those seasons were represented with the
summer results. The primary seasonal
influence on transmission loss is the
presence of a sound channel, or duct,
near the surface in winter.
Marine Mammal Density Information
The best available scientific
information was considered in
conducting marine mammal exposure
estimates (the basis for estimating take).
Roberts et al. (2016) provided several
key improvements over information
previously available for the GOM, by
incorporating NMFS aerial and
shipboard survey data collected over the
period 1992–2009; controlling for the
influence of sea state, group size,
availability bias, and perception bias on
the probability of making a sighting; and
modeling density from an expanded set
of eight physiographic and 16 dynamic
oceanographic and biological covariates.
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There are multiple reasons why marine
mammals may be undetected by
observers. Animals are missed because
they are underwater (availability bias) or
because they are available to be seen,
but are missed by observers (perception
and detection biases) (e.g., Marsh and
Sinclair, 1989). Negative bias on
perception or detection of an available
animal may result from environmental
conditions, limitations inherent to the
observation platform, or observer
ability. Therefore, failure to correct for
these biases may lead to underestimates
of cetacean abundance (as is the case for
NMFS’ SAR abundance estimates for the
GOM). Additional data was used to
improve detection functions for taxa
that were rarely sighted in specific
survey platform configurations. The
degree of underestimation would likely
be particularly high for species that
exhibit long dive times or are cryptic,
such as sperm whales, beaked whales,
or Kogia spp. In summary, consideration
of additional survey data and an
improved modeling strategy allowed for
an increased number of taxa modeled
and better spatiotemporal resolutions of
the resulting predictions. More
information concerning the Roberts et
al. (2016) models, including the model
results and supplementary information
for each model, is available online at
seamap.env.duke.edu/models/Duke-ECGOM-2015/.
Description of Exposure Estimates
The sound received by an animal
when near a sound source is a function
of the animal’s position relative to the
source, and both source and animals
may be moving. To a reasonable
approximation, we know, predict, or
specify the location of the sound source,
a 3D sound field around the source, and
the expected occurrence of animals
within 100 km2 grid cells (Roberts et al.,
2016). However, because the specific
location of animals within the modeled
sound field is unknown, agent-based
animal movement modeling is necessary
to complete the assessment of potential
acoustic exposure. Realistic animal
movement within the sound field can be
simulated, and repeated random
sampling (Monte Carlo)—achieved by
simulating many animals within the
operations area—used to estimate the
sound exposure history of animals
during the operation. Animats are
randomly placed, or seeded, within the
simulation boundary at a specified
density, and the probability of an
event’s occurrence is determined by the
frequency with which it occurs in the
simulation. Higher densities provide a
finer resolution for an estimate of the
probability distribution function (PDF),
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but require greater computational
resources. To ensure good
representation of the PDF, the animat
density is set as high as is practical,
with the resulting PDF then scaled using
the real-world animal density (Roberts
et al., 2016) to obtain the real-world
number of modeled acoustic exposures.
Several models for marine mammal
movement have been developed (e.g.,
Frankel et al., 2002, Gisiner et al., 2006;
Donovan et al., 2013). Animats
transition from one state to another,
with user-specified parameters
representing simple states, such as the
speed or heading of the animal, or
complex states, such as likelihood of an
animal foraging, playing, resting, or
traveling. This analysis uses the Marine
Mammal Movement and Behavior
(3MB) model (Houser, 2006). Parameter
values to control animat movement are
typically determined using available
species-specific behavioral studies, but
the amount and quality of available data
varies by species. While available data
often provides a detailed description of
the proximate behavior expected for real
individual animals, species with more
available information must be used as
surrogates for those without sufficient
available information. In this study,
pantropical spotted dolphins are used as
a surrogate for Clymene, spinner, and
striped dolphins; short-finned pilot
whales are surrogates for Fraser’s
dolphins, Kogia spp., and melon-headed
whales; and rough-toothed dolphins are
surrogates for false killer whales and
pygmy killer whales. Observational data
for all remaining species in the study
were sufficient to determine animat
movement.
Species-specific animats were created
with programmed behavioral parameters
describing dive depth, surfacing and
dive durations, swimming speed, course
change, and behavioral aversions (e.g.,
water too shallow). The programmed
animats were then randomly distributed
over a given bounded simulation area.
Because the exact positions of sound
sources and animals are not known in
advance for proposed activities,
multiple runs of realistic predictions are
used to provide statistical validity to the
simulated scenarios. Each speciesspecific simulation was seeded with
approximately 0.1 animats/km2 which,
in most cases, represents a higher
density of animats in the simulation
than occurs in the real environment. A
separate simulation was created and run
for each combination of location, survey
movement pattern, and marine mammal
species. Animats were only allowed to
be ‘taken’ once during a 24-hour
evaluation period. That is, an animat
whose received level exceeds the peak
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SPL threshold more than once during an
evaluation period was only counted
once. Energy accumulation for SEL
occurred throughout the 24-hour
integration period and was reset at the
beginning of each period. Similarly, the
maximum received rms SPL was
determined for the entirety of the
evaluation period and reset at the
beginning of each period.
The JASCO Exposure Modeling
System (JEMS) combined animal
movement data (i.e., the output from
3MB), with pre-computed acoustic
fields. The JEMS output was the timehistory of received levels and slant
ranges (the three-dimensional distance
between the animat and the source) for
all animats of the 3MB simulation.
Animat received levels and slant ranges
are used to determine the risk of
acoustic exposure. There were many
animats in the simulations and together
their received levels represent the
probability, or risk, of exposure for each
survey.
All survey simulations were for 7
days and a sliding 4-hr window
approach was used to get the average
24-hr exposure. In this sliding-window
approach, 42 exposure estimate samples
are obtained for each seven-day
simulation, with the mean value then
used as the 24-hr exposure estimate for
that survey. The 24-hr exposure levels
were then scaled by the projected level
of effort for each survey type (i.e.,
multiplied by the number of days) to
calculate associated annual exposure
levels. The number of individual
animals expected to exceed threshold
during the 24-hr window is the number
of animats exposed to levels exceeding
threshold multiplied by the ratio of realworld animal density to model animat
density.
Injury—To evaluate the likelihood an
animal might experience auditory injury
as a result of accumulated sound energy,
the cSEL for each animat in the
simulation was calculated. To obtain
that animat’s cSEL, the SEL an animat
received from each source over the 24hr integration window was summed,
and the number of animats whose cSEL
exceeded the specified thresholds
(Table 7) during the integration window
was counted. To evaluate the likelihood
an animal might be injured via exposure
to peak SPL, the range at which the
specific peak SPL threshold (Table 7)
occurs for each source based on the
broadband peak SPL source level was
estimated. For each 24-hr integration
window, the number of animats that
came within this range of the source
was counted.
Behavior—To evaluate the likelihood
an animal might experience disruption
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of behavioral patterns (i.e., a ‘‘take’’), the
number of animats that received a
maximum rms SPL exposure within the
specified step ranges (Table 6) was
calculated. The number of animats with
a maximum rms SPL received level
categorized into each bin of the step
function was multiplied by the
probability of the behavioral response
specific to that range (Table 6).
Specifically, 10 percent of animals
exposed to received levels from 140–159
dB rms would be assumed as ‘‘takes,’’
while 50 percent exposed to levels
between 160–179 dB rms and 90 percent
exposed to levels of 180 dB rms and
above would be. The totals within each
bin were then summed as the total
estimated number of exposures above
Level B harassment thresholds. This
process was repeated for each 24-hr
integration window. For beaked whales,
for which lower behavioral harassment
thresholds are designated, 50 percent of
animals exposed to received levels from
120–149 dB rms would be assumed as
‘‘takes,’’ while 90 percent exposed to
levels of 140 dB rms and above would
be.
Take Estimates
In summary, BOEM provided
estimated levels of effort for geophysical
survey activity in the GOM for a
notional ten-year period. Exposure
estimates were then computed from
modeled sound levels received by
animats for several representative types
of geophysical surveying. Because
animals and acoustic sources move
relative to the environment and each
other, and the sound fields generated by
the sources are shaped by various
physical parameters, the sound levels
received by an animal are a complex
function of location and time. The basic
modeling approach was to use acoustic
models to compute the 3D sound fields
and their variations in time. Animats
were modeled moving through these
fields to sample the sound levels in a
manner similar to how real animals
would experience these sounds. From
the time histories of the received sound
levels of all animats, the numbers of
animals exposed to levels exceeding
effects threshold criteria were
determined and then adjusted by the
number of animals expected in the area,
based on density information, to
estimate the potential number of realworld marine mammal exposures to
levels above the defined criteria. The
acoustic exposure history of many
simulated animals (animats) allows for
the estimation of potential exposures
due to operations. These modeled
exposures are summed and represent
the aggregate exposures that may result
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from future surveys given the specified
levels of effort for each survey type in
each year and may vary according to the
statistical distribution associated with
these mean annual exposures.
Exposure estimates above Level A and
Level B harassment criteria, developed
by Zeddies et al. (2015, 2017a) in
association with the activity projections
for the various annual effort scenarios,
were generated based on the specific
modeling scenarios (including source
and survey geometry), i.e., 2D survey (1
× 8,000 in3 array), 3D NAZ survey (2 ×
8,000 in3 array), 3D WAZ survey (4 ×
8,000 in3 array), coil survey (4 × 8,000
in3 array), shallow penetration survey
(either single 90 in3 airgun or boomer),
and HRG surveys (side-scan sonar,
multibeam echosounder, and subbottom profiler). Annual effort scenariobased pooled exposure estimates are
therefore available by species.
NMFS presented BOEM’s original 10year activity projections in Table 1 of
the notice of proposed rulemaking
under ‘‘Detailed Description of
Activities.’’ For purposes of analysis in
the notice of proposed rulemaking,
NMFS identified representative ‘‘high,’’
‘‘moderate,’’ and ‘‘low’’ effort years.
Because the duration of these
regulations are limited to five years,
NMFS needed to determine a reasonable
basis for evaluating acoustic exposures
that might occur during that timeframe
(rather than ten years). Therefore, for the
proposed rule, in recognition of
relatively low recent levels of
geophysical survey activity, from the ten
notional years of projected survey effort
provided by BOEM, NMFS selected five
representative years representing three
different potential levels of survey effort
as the basis for the assessment. These
included one ‘‘high-activity’’ year, two
separate ‘‘moderate-activity’’ years, and
two separate ‘‘low-activity’’ years.
Because the first 5 years of BOEM’s
original effort projections were
relatively high-effort years, NMFS’
level-of-effort selections for the
proposed rule corresponded with the
detailed per-survey type effort
projections given for Years 1, 4, 5, 8,
and 9, respectively. Exposure estimates
resulting from the process summarized
here and corresponding with those
activity scenarios were shown in Table
8 of the notice of proposed rulemaking.
These exposure estimates were then
further evaluated to provide an estimate
of takes of marine mammals that could
occur as a result of a reasonably
expected level of geophysical survey
activity in the GOM over the course of
five years. Take estimates associated
with those scenarios, which informed
the analysis in the proposed rule, are
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shown in Table 8 of this document for
reference. These values have been
updated from those shown in Table 8 of
the notice of proposed rulemaking by
correctly incorporating discounted
estimates of Level A harassment into the
estimates of Level B harassment (as
pointed out by public commenters).
Level A Harassment
As we explain here, the modeled
exposure estimates for onset of
permanent threshold shift (i.e., Level A
harassment), are not expected to
represent realistic results for any
species. Overall, there is a low
likelihood of take by Level A
harassment for any species, though the
degree of this low likelihood is
primarily influenced by the specific
hearing group. For mid- and highfrequency cetaceans, potential auditory
injury would be expected to occur on
the basis of instantaneous exposure to
peak pressure output from an airgun
array while, for low-frequency
cetaceans, potential auditory injury
would occur on the basis of the
accumulation of energy output over
time by an airgun array. Importantly, the
modeled exposure estimates do not
account for either aversion or the
beneficial impacts of the required
mitigation measures.
Of even greater import for midfrequency cetaceans is that the small
calculated Level A harassment zone size
in conjunction with the properties of
sound fields produced by arrays in the
near field versus far field leads to a
logical conclusion that Level A
harassment is so unlikely for species in
this hearing group as to be discountable.
As stated in the notice of proposed
rulemaking, for all mid-frequency
cetaceans, following evaluation of the
available scientific literature regarding
the auditory sensitivity of midfrequency cetaceans and the properties
of airgun array sound fields, NMFS does
not expect any reasonable potential for
Level A harassment to occur. We
discussed this issue in detail earlier in
the response to public comments. NMFS
expects the potential for Level A
harassment of mid-frequency cetaceans
to be discountable, even before the
likely moderating effects of aversion are
considered. When considering potential
for aversion, NMFS does not believe
that Level A harassment is a likely
outcome for any mid-frequency cetacean
(as reflected in Table 9).
As discussed in greater detail in the
notice of proposed rulemaking, NMFS
and BOEM considered the possibility of
incorporating quantitative adjustments
within the modeling process to account
for the effects of mitigation and/or
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aversion, as both of these factors would
lead to a reduction in likely injurious
exposure. However, these factors were
ultimately not quantified in the
modeling because, in summary, there is
too much inherent uncertainty regarding
the effectiveness of detection-based
mitigation to support any reasonable
quantification of its effect in reducing
injurious exposure and there is too little
information regarding the likely level of
onset and degree of aversion to quantify
this behavior in the modeling process.
This does not mean that mitigation is
not effective (to some degree) in
avoiding incidents of Level A
harassment, nor does it mean that
aversion is not a meaningful real-world
effect of noise exposure that should be
expected to reduce the number of
incidents of Level A harassment.
However, certain public commenters
misconstrued statements in the notice of
proposed rulemaking regarding the
strictly modeling-related investigations
of aversion (i.e., that there is not
sufficient quantitative data to inform
decisions regarding the programming of
animats as far as received levels of noise
that provoke aversive response, and the
degree of response, for relevant species)
as meaning that there is not sufficient
information to support that aversion
happens at all. To the contrary, there is
ample evidence in the literature that
aversion is one of the most common
responses to noise exposure across
varied species, though the onset and
degree may be expected to vary across
individuals and in different contexts.
Therefore, NMFS proposed to
incorporate a reasonable adjustment to
modeled Level A harassment exposure
estimates to account for aversion for
low- and high-frequency species. That
adjustment is retained here, as
discussed in greater detail in the
responses to public comments.
Specifically, NMFS assumes here that
an eighty percent reduction in modeled
exposure estimates for Level A
harassment for low- and high-frequency
cetaceans is reasonable and likely
conservative in terms of the overall
numbers of actual incidents of Level A
harassment for these species, as the
adjustment does not explicitly account
for the effects of mitigation.
As discussed previously, BOEM
provided an update to the scope of their
proposed action through removal of the
area subject to leasing moratorium
under GOMESA from consideration in
the rule. In support of this revision,
BOEM provided revised 5-year level of
effort predictions and associated
acoustic exposure estimates. BOEM’s
process for developing this information,
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described in detail in ‘‘Revised Modeled
Exposure Estimates,’’ available online,
was straightforward. Rather than using
the PEIS’s 10-year period, BOEM
provided revised levels of effort for a 5year period, using Years 1–5 of the
original level of effort projections.
BOEM stated that the first five years
were selected to be carried forward
‘‘because they were contiguous, they
included the three years with the most
activity, and they were the best
understood in relation to the historical
data upon which they are based.’’ NMFS
concurs with this choice. Levels of effort
were revised based on the basic
assumption that if portions of areas are
removed from consideration, then the
corresponding effort previously
presumed to occur in those areas also is
removed from consideration. The
revised levels of effort are shown in
Table 2. Associated revised take
estimates, which were generated
utilizing the methods described above
and in the proposed rule and inform the
analysis in this final rule, are shown in
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Table 9. These estimates have been
modified from the values provided by
BOEM (available online; ‘‘Revised
Modeled Exposure Estimates’’) in that
we have correctly accounted for the type
of taking expected, i.e., for midfrequency cetaceans, Level A
harassment is not expected to occur and
the calculated takes have been shifted
into the totals for Level B harassment.
No incidents of Level A harassment for
Bryde’s whales were predicted under
the revised effort scenarios, which
exclude the area where most Bryde’s
whales would be expected to be found.
For Kogia spp., estimates of Level A
harassment were adjusted as discussed
previously to account for likely
aversion, and the portion of estimated
Level A harassment events not expected
to occur were shifted into the totals for
Level B harassment for these species.
Estimated instances of take, i.e.,
scenario-specific acoustic exposure
estimates incorporating the adjustments
to Level A harassment exposure
estimates discussed here, are shown in
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Table 9. This information regarding total
number of takes (with Level A
harassment takes based on assumptions
relating to mid-frequency cetaceans in
general as well as aversion), on an
annual basis for five years, provides the
bounds within which incidental take
authorizations may be issued in
association with this regulatory
framework.
Typically, and especially in cases
where PTS is predicted, NMFS
anticipates that some number of
individuals may incur TTS. However, it
is not necessary to separately quantify
those takes, as it is unlikely that an
individual marine mammal would be
exposed at the levels and duration
necessary to incur TTS without also
being exposed to the levels associated
with behavioral disruption and,
therefore, NMFS expects any potential
TTS takes to be captured by the
estimated takes by behavioral disruption
(discussed below).
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3
0
728
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
A
High
572
43,549
19,101
235,667
37,816
655,345
111,211
133,758
609,653
83,041
44,232
13,910
27,165
69,152
18,112
25,622
1,498
19,326
B
422
27,300
13,328
162,172
30,306
979,905
73,225
175,128
421,786
59,818
30,069
9,690
18,197
47,719
12,335
17,708
1,034
12,198
B
Moderate #1
2
0
475
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
A
510
33,378
16,188
190,824
31,231
598,607
87,995
116,988
513,572
73,259
36,431
11,438
22,005
57,004
14,859
20,922
1,262
14,214
B
Moderate #2
2
0
636
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
A
2
0
472
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
A
Low #1
395
26,681
12,629
151,745
28,775
941,001
69,913
165,221
401,568
56,735
28,652
9,162
17,380
45,011
11,733
16,849
987
11,565
B
2
0
562
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
A
Low #2
411
27,689
13,414
156,622
26,420
581,121
73,051
110,126
421,856
59,448
30,023
9,426
18,166
46,801
12,198
17,239
1,039
11,942
B
2
0
575
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
A
462
31,719
14,932
179,406
30,910
751,196
83,079
140,244
473,687
66,460
33,881
10,725
20,583
53,137
13,847
19,668
1,164
13,849
B
Mean annual take
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0
0
371
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
A
Year 1
10
16,405
10,383
191,566
30,640
603,649
85,828
128,299
478,490
75,953
33,573
4,522
21,859
55,813
8,079
16,165
60
15,045
B
0
0
337
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
A
Year 2
8
14,205
9,313
162,301
27,024
973,371
67,915
183,717
436,047
71,873
29,275
3,843
18,767
47,784
6,964
13,710
56
9,824
B
0
0
310
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
A
Year 3
8
13,603
8,542
158,328
25,880
567,962
73,522
112,120
391,363
61,098
27,837
3,792
18,218
46,584
6,764
13,604
50
13,645
B
0
0
209
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
A
B
6
9,496
6,238
111,415
19,620
1,001,256
47,332
191,495
311,316
48,775
20,136
2,726
12,738
32,581
4,970
9,664
42
7,459
Year 4
0
0
314
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
A
Year 5
7
12,388
8,318
142,929
23,219
567,446
60,379
111,305
395,987
64,357
26,056
3,455
16,634
42,224
6,277
12,269
52
8,959
B
0
0
308
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
A
8
13,219
8,559
153,308
25,277
742,737
66,995
145,387
402,641
64,411
27,375
3,668
17,643
44,997
6,611
13,082
52
10,986
B
Mean annual take
1 A and B refer to expected instances of take by Level A and Level B harassment, respectively, for Years 1–5. For Kogia spp., expected takes by Level A harassment represent modeled exposures adjusted to account for aversion. For the Bryde’s whale, no takes by Level A harassment are predicted to occur. Therefore, no adjustment to modeled exposures to account for aversion was necessary. For Kogia spp., exposures
above Level A harassment criteria were predicted by the peak SPL metric. For the Bryde’s whale, the cSEL metric is used to evaluate the potential for Level A harassment.
Bryde’s whale .............................................................
Sperm whale ...............................................................
Kogia spp. ...................................................................
Beaked whale .............................................................
Rough-toothed dolphin ...............................................
Bottlenose dolphin ......................................................
Clymene dolphin .........................................................
Atlantic spotted dolphin ..............................................
Pantropical spotted dolphin ........................................
Spinner dolphin ...........................................................
Striped dolphin ............................................................
Fraser’s dolphin ..........................................................
Risso’s dolphin ............................................................
Melon-headed whale ..................................................
Pygmy killer whale ......................................................
False killer whale ........................................................
Killer whale .................................................................
Short-finned pilot whale ..............................................
Species
TABLE 9—REVISED INSTANCES OF TAKE (BY LEVEL A AND LEVEL B HARASSMENT) (YEARS 1–5) AND MEAN ANNUAL TAKE LEVELS 1
1 A and B refer to expected scenario-based instances of take by Level A and Level B harassment, respectively. For the Bryde’s whale and Kogia spp., expected takes by Level A harassment represent modeled exposures adjusted to account for aversion. For Kogia spp., exposures above Level A harassment criteria were predicted by the peak SPL metric. For the Bryde’s whale, exposures above Level A harassment criteria
were predicted by the cSEL metric.
2 High survey effort scenario corresponds with level of effort projections given previously for Year 1 (see Table 1 of the notice of proposed rulemaking). Moderate #1 and #2 and Low #1 and #2 correspond with
Years 4, 5, 8, and 9, respectively.
Bryde’s whale .............................................................
Sperm whale ...............................................................
Kogia spp. ...................................................................
Beaked whale .............................................................
Rough-toothed dolphin ...............................................
Bottlenose dolphin ......................................................
Clymene dolphin .........................................................
Atlantic spotted dolphin ..............................................
Pantropical spotted dolphin ........................................
Spinner dolphin ...........................................................
Striped dolphin ............................................................
Fraser’s dolphin ..........................................................
Risso’s dolphin ............................................................
Melon-headed whale ..................................................
Pygmy killer whale ......................................................
False killer whale ........................................................
Killer whale .................................................................
Short-finned pilot whale ..............................................
Species
Survey effort scenario 2
TABLE 8—SCENARIO-SPECIFIC INSTANCES OF TAKE (BY LEVEL A AND LEVEL B HARASSMENT) AND MEAN ANNUAL TAKE LEVELS EVALUATED IN THE PROPOSED
RULE 1
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Level B Harassment
NMFS has determined the estimated
values shown in Table 9 are a
reasonable representation of the
potential instances of take that may
occur (more specifically, each of these
‘‘takes’’ representing a day in which one
individual is exposed above the Level B
harassment criteria, even if only for
seconds). However, these take numbers
do not represent the number of
individuals expected to be taken, given
they are higher than the estimated
abundance for all species. Accordingly,
as described in the notice of proposed
rulemaking, NMFS references Test
Scenario 1 in the modeling report
(‘‘Long-Duration Surveys and Scaling
Methods’’) to inform two important
parts of the analyses. Comparing the
results of modeling simulations that
more closely match longer survey
durations (30 days) to the results of 24hour take estimates scaled up to 30 days
(as the instances of take in Table 9 were
calculated) provides the comparative
ratios of number of individuals taken/
calculated (within a 30-day survey) and
instances of take, in order to better
understand the comparative distribution
of exposures across individuals of
different species. First, in NMFS’
analyses in this rule, the ratio and its
inverse are used to inform a better
understanding of the nature in which
individuals are taken across the
multiple days of a longer duration
survey given the different behaviors that
are represented in the animat modeling,
i.e., looking at the ratio of (number of
individuals taken in 30-day modeling
scenario)/(number of instances of take
when 1-day average multiplied by 30
days), if all else is equal within one
survey, for the species with a smaller
ratio (larger inverse), fewer individuals
will be taken but each will be exposed
above the threshold on a higher number
of days (see Table 16). Second, this ratio
may be appropriately be used in
combination with the calculated
instances of take to predict the number
of individuals taken for surveys of
similar duration (noting that for surveys
of notably longer than 30-day duration,
it will still likely result in some degree
of overestimate of individuals), in order
to support evaluation of take estimates
in requests for Letters of Authorization,
given the need to meet the ‘‘small
numbers of marine mammals’’ standard,
which is based on the number of
individuals taken. A summary of this,
which was included in the notice of
proposed rulemaking along with a
description of the other Test Scenarios
and how they inform this analysis, is
included below.
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Although some survey operations may
continue for months, survey simulations
were conducted for seven days in order
to derive mean 24-hr exposure averages,
with these averages then used to scale
according to the total number of survey
days projected by BOEM. This approach
was necessary due to the more
computationally-intensive modeling
required to model more realistic
durations (i.e., 30 days). As summarized
above and discussed in detail in the
notice of proposed rulemaking, a test
scenario was used to evaluate methods
for scaling results from shorter-duration
simulations to longer duration
operations. Results from test modeling
conducted for a suite of six
representative species over 30-day
simulations of a hypothetical 3D WAZ
survey were compared to the results of
a shorter 5-day simulation, i.e., the
number of animats exposed to levels
exceeding threshold for 24-hr time
periods multiplied by the number of
days in the simulations was compared
to the number of animats exposed to
levels exceeding threshold for the entire
duration of the simulations. The results
of the test scenario indicated that
undesired systematic biases in the
modeling procedure, if present, were
small relative to the survey design and
would not affect scaling up the results
in time (i.e., the shorter 7-day
simulations ultimately used in the
modeling would provide unbiased
results). However, the results also
indicated that scaling up the 24-hr
average SPL exposure estimates to 30
days greatly overestimates the number
of notional marine mammals (i.e.,
animats) exposed to levels exceeding
threshold when determined over the
entire simulation (although the
estimated instances of exposure are
reasonably accurate). This occurs
because animats were commonly
exposed to levels exceeding these
thresholds, and the relatively short reset
period of 24 hours means that
individual animats were, in effect,
counted several times during the scaleup (i.e., on multiple days) whereas they
would only have been counted once
when evaluating over the entire
simulation. When a real-world survey
extends over longer durations within
the same region, it is most likely that the
same individuals are repeatedly
exposed to survey noise. However, the
modeling assumption that populations
of animals were reset for each 24-hr
period is equivalent to an assumption
that each survey day is a completely
independent event, i.e., that new
individuals are impacted on each
subsequent day.
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In order to determine more realistic
exposure probabilities for individuals
across multiple days, modeled results
were compared for a 30-day period
versus the aggregation of 24-hr
population reset intervals (the
investigation described above) to
determine a species-typical offset of
modeled daily exposures. When
conducting computationally-intensive
modeling over the full assumed 30-day
survey period (versus aggregating the
smaller 24-hr periods for 30 days),
results showed about 10–45 percent of
the total number of takes calculated
using a 24-hr reset of the population,
with differences relating to speciestypical movement and residency
patterns. Given that many of the
evaluated survey activities occur for 30day or longer periods, particularly some
of the larger surveys for which the
majority of the modeled exposures
occur, using such a scaling process is
appropriate in order to evaluate the
likely severity of the predicted
exposures. This approach is also
discussed in more detail in the EWG
report (Southall et al., 2017), available
online at: www.fisheries.noaa.gov/
action/incidental-take-authorization-oiland-gas-industry-geophysical-surveyactivity-gulf-mexico.
The test scenario modeled six
representative GOM species/guilds:
Bryde’s whale, sperm whale, beaked
whales, bottlenose dolphin, Kogia spp.,
and short-finned pilot whale. For
purposes of this analysis, bottlenose
dolphin was used as a proxy for other
small dolphin species, and short-finned
pilot whale was used as a proxy for
other large delphinids. Tables 22–23 in
the modeling report provide information
regarding the number of modeled
animals receiving exposure above
criteria for average 24-hr sliding
windows scaled to the full 30-day
duration and percent change in
comparison to the same number
evaluated when modeling the full 30day duration. This information was
used to derive 30-day scalar ratios
which, when applied to the total
instances of take given in Table 9,
captures repeated takes of individuals at
a 30-day sampling level. Scalar ratios
are as follows: Bryde’s whale, 0.189;
sperm whale, 0.423; beaked whales,
0.101; bottlenose dolphin, 0.287; Kogia
spp., 0.321; and short-finned pilot
whale, 0.295. Application of the rescaling method reduced the overall
magnitude of modeled takes for all
species by slightly more than double to
up to ten-fold (Table 10).
These adjusted take numbers (shown
in Table 10) provide a more realistic
basis upon which to evaluate severity of
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the expected taking. Please see the
Negligible Impact Analysis and
Determinations section, later in this
document, for additional detail. It is
important to recognize that while these
scaled numbers better reflect the
number of individuals likely to be taken
within a single 30-day survey than the
number of instances in Table 9, they
will still overestimate the number of
individuals taken across the aggregated
GOM activities, because they do not
correct for (i.e., further reduce take to
account for) individuals exposed to
multiple surveys or fully correct for
individuals exposed to surveys
significantly longer than 30 days.
As noted in the beginning of this
section and in the Small Numbers
section, using modeled instances of take
(Table 9) and the method described here
to scale those numbers (based on Test
Scenario 1) allows one to more
accurately predict the number of
individuals that will be taken as a result
of exposure to one survey and,
therefore, these scaled predictions
should be considered in requests for
LOAs to assess whether a resulting LOA
would meet the small numbers
standard. However, for the purposes of
ensuring that the take authorized
pursuant to all issued LOAs is within
the scope of the analysis conducted to
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support the negligible impact finding in
this rule, authorized instances of take
(which are the building blocks of the
analysis) also must be assessed.
Specifically, reflecting Table 9 and what
has been analyzed, the total take
authorized for any given species or
stock over the course of the five years
covered under these regulations should
not exceed the sum of the five years of
take indicated for the five scenarios in
that table, and in any given year, the
take of any species should not exceed
the highest annual take listed for any of
the five scenarios.
TABLE 10—EXPECTED TOTAL TAKE NUMBERS, SCALED 1
Species
Year 1
Bryde’s whale .......................................................................
Sperm whale ........................................................................
Kogia spp. ............................................................................
Beaked whale ......................................................................
Rough-toothed dolphin .........................................................
Bottlenose dolphin ...............................................................
Clymene dolphin ..................................................................
Atlantic spotted dolphin ........................................................
Pantropical spotted dolphin .................................................
Spinner dolphin ....................................................................
Striped dolphin .....................................................................
Fraser’s dolphin ...................................................................
Risso’s dolphin .....................................................................
Melon-headed whale ............................................................
Pygmy killer whale ...............................................................
False killer whale .................................................................
Killer whale ...........................................................................
Short-finned pilot whale .......................................................
1 Scalar
2
6,939
3,452
19,348
8,794
173,247
24,633
36,822
137,327
21,799
9,635
1,298
6,448
16,465
2,383
4,769
18
4,438
2
6,009
3,098
16,392
7,756
279,357
19,492
52,727
125,145
20,628
8,402
1,103
5,536
14,096
2,054
4,044
17
2,898
Year 3
2
5,754
2,841
15,991
7,428
163,005
21,101
32,178
112,321
17,535
7,989
1,088
5,374
13,742
1,995
4,013
15
4,025
Year 4
1
4,017
2,069
11,253
5,631
287,360
13,584
54,959
89,348
13,998
5,779
782
3,758
9,611
1,466
2,851
12
2,200
Year 5
1
5,240
2,771
14,436
6,664
162,857
17,329
31,945
113,648
18,470
7,478
992
4,907
12,456
1,852
3,619
15
2,643
ratios were applied to values in Table 9 as described in preceding text to derive scaled take numbers shown here.
Mitigation
‘‘Least Practicable Adverse Impact’’
Standard
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Year 2
Under section 101(a)(5)(A) of the
MMPA, NMFS must set forth the
permissible methods of taking pursuant
to such activity, and other means of
effecting the least practicable adverse
impact on such species or stock and its
habitat, paying particular attention to
rookeries, mating grounds, and areas of
similar significance, and on the
availability of such species or stock for
subsistence uses (hereinafter referred to
as ‘‘LPAI’’ or ‘‘least practicable adverse
impact’’). NMFS does not have a
regulatory definition for least
practicable adverse impact. However,
NMFS’ implementing regulations
require applicants for incidental take
authorizations to include information
about the availability and feasibility
(economic and technological) of
equipment, methods, and manner of
conducting such activity or other means
of effecting the least practicable adverse
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impact upon the affected species or
stocks and their habitat (50 CFR
216.104(a)(11)). We note that in some
cases, certain mitigation may be
necessary in order to make a ‘‘negligible
impact’’ finding for an affected species
or stock, which is a fundamental
requirement of issuing an
authorization—in these cases,
consideration of practicability may be a
lower priority for decision-making if
impacts to marine mammal species or
stocks would not be negligible in the
measure’s absence.
In Conservation Council for Hawaii v.
NMFS, 97 F. Supp. 3d 1210, 1229 (D.
Haw. 2015), the district court stated that
NMFS ‘‘appear[s] to think [it satisfies]
the statutory ‘least practicable adverse
impact’ requirement with a ‘negligible
impact’ finding.’’ Later, expressing
similar concerns in a challenge to an
incidental take rule for U.S. Navy
Operation of Surveillance Towed Array
Sensor System Low Frequency Active
(SURTASS LFA) Sonar (77 FR 50290,
August 20, 2012), the Ninth Circuit in
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Natural Resources Defense Council
(NRDC) v. Pritzker, 828 F.3d 1125, 1134
(9th Cir. 2016), stated, ‘‘[c]ompliance
with the ‘negligible impact’ requirement
does not mean there [is] compliance
with the ‘least practicable adverse
impact’ standard.’’ NMFS is in full
agreement that the ‘‘negligible impact’’
and ‘‘least practicable adverse impact’’
requirements are distinct, even though
both statutory standards refer to species
and stocks. With that in mind, we
provide further explanation of NMFS’
interpretation of least practicable
adverse impact and explain what
distinguishes it from the negligible
impact standard. This discussion is
consistent with, and expands upon,
previous rules issued by NMFS, such as
the Navy Gulf of Alaska rule (82 FR
19530; April 27, 2017); the Navy
Atlantic Fleet Testing and Training rule
(83 FR 57076; November 14, 2018); the
Navy Hawaii-Southern California
Training and Testing rule (83 FR 66846;
December 27, 2018); and the SURTASS
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LFA sonar rule (84 FR 40132; August
13, 2019).
Before NMFS can issue incidental
take regulations under section
101(a)(5)(A) of the MMPA, it must make
a finding that the total taking will have
a ‘‘negligible impact’’ on the affected
‘‘species or stocks’’ of marine mammals.
NMFS’ and the U.S. Fish and Wildlife
Service’s implementing regulations for
section 101(a)(5) both define ‘‘negligible
impact’’ as an impact resulting from the
specified activity that cannot be
reasonably expected to, and is not
reasonably likely to, adversely affect the
species or stock through effects on
annual rates of recruitment or survival
(50 CFR 216.103 and 50 CFR 18.27(c)).
Recruitment (i.e., reproduction) and
survival rates are used to determine
population growth rates 12 and,
therefore, are considered in evaluating
population level impacts.
As NMFS stated in the preamble to
the final rule for the incidental take
implementing regulations, not every
population-level impact violates the
negligible impact requirement. The
negligible impact standard does not
require a finding that the anticipated
take will have ‘‘no effect’’ on population
numbers or growth rates: ‘‘The statutory
standard does not require that the same
recovery rate be maintained, rather that
no significant effect on annual rates of
recruitment or survival occurs. [T]he
key factor is the significance of the level
of impact on rates of recruitment or
survival.’’ (54 FR 40338, 40341–42;
September 29, 1989).
While some level of impact on
population numbers or growth rates of
a species or stock may occur and may
still satisfy the negligible impact
requirement—even without
consideration of mitigation—the least
practicable adverse impact provision
separately requires NMFS to prescribe
means of effecting the least practicable
adverse impact on such species or stock
and its habitat, paying particular
attention to rookeries, mating grounds,
and areas of similar significance, 50 CFR
216.102(b), which are typically
identified as mitigation measures.13
The negligible impact and least
practicable adverse impact standards in
the MMPA both call for evaluation at
the level of the ‘‘species or stock.’’ The
MMPA does not define the term
‘‘species.’’ However, Webster’s New
Collegiate Dictionary (1981) defines
‘‘species’’ to include ‘‘a group of
12 A
growth rate can be positive, negative, or flat.
purposes of this discussion, we omit
reference to the language in the standard for least
practicable adverse impact that says that NMFS also
must mitigate for subsistence impacts, because
subsistence impacts are not at issue in this action.
13 For
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intimately related and physically
similar organisms that actually or
potentially interbreed [. . .], that
ordinarily comprise differentiated
populations limited geographically
[. . .] or ecologically [. . .]’’ (emphasis
added). See also Merriam-Webster
Dictionary, which defines ‘‘species’’ to
include ‘‘related organisms or
populations potentially capable of
interbreeding.’’ www.merriamwebster.com/dictionary/species
(emphasis added). The MMPA defines
‘‘stock’’ as a group of marine mammals
of the same species or smaller taxa in a
common spatial arrangement that
interbreed when mature (16 U.S.C.
1362(11)). The definition of
‘‘population’’ includes ‘‘a group of
interbreeding biotypes that represents
the level of organization at which
speciation begins.’’ Webster’s New
Collegiate Dictionary (1981). See also
www.merriam-webster.com/dictionary/
population, which defines population as
‘‘a group of interbreeding organisms that
represents the level of organization at
which speciation begins.’’ The
definition of ‘‘population’’ is strikingly
similar to the MMPA’s definition of
‘‘stock,’’ with both involving groups of
individuals that belong to the same
species and are located in a manner that
allows for interbreeding. In fact, the
term ‘‘stock’’ in the MMPA is
interchangeable with the statutory term
‘‘population stock.’’ (16 U.S.C.
1362(11)). Both the negligible impact
standard and the least practicable
adverse impact standard call for
evaluation at the level of the species or
stock, and the terms ‘‘species’’ and
‘‘stock’’ both relate to populations.
Therefore, it is appropriate to view both
the negligible impact standard and the
least practicable adverse impact
standard as having a population-level
focus.
This interpretation is consistent with
Congress’s statutory findings for
enacting the MMPA, nearly all of which
are most applicable at the species or
stock (i.e., population) level. See 16
U.S.C. 1361 (finding that it is species
and population stocks that are or may be
in danger of extinction or depletion; that
it is species and population stocks that
should not diminish beyond being
significant functioning elements of their
ecosystems; and that it is species and
population stocks that should not be
permitted to diminish below their
optimum sustainable population level).
Annual rates of recruitment (i.e.,
reproduction) and survival are the key
biological metrics used in the evaluation
of population-level impacts, and
accordingly these same metrics are also
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used in the evaluation of populationlevel impacts for the least practicable
adverse impact standard.
Recognizing this common focus of the
least practicable adverse impact and
negligible impact provisions on the
‘‘species or stock’’ does not mean that
NMFS conflates the two standards;
despite some common statutory
language, we recognize the two
provisions are different and have
different functions.
First, a negligible impact finding is
required before NMFS can issue an
incidental take authorization. Although
it is acceptable to use mitigation
measures to reach a negligible impact
finding (see 50 CFR 216.104(c)), no
amount of mitigation can enable NMFS
to issue an incidental take authorization
for an activity that would not meet the
negligible impact standard.
Second, even where NMFS can reach
a negligible impact finding—which we
emphasize does allow for the possibility
of some ‘‘negligible’’ population-level
impact—the agency must still prescribe
measures that will effect the least
practicable amount of adverse impact
upon the affected species or stock.
Section 101(a)(5)(A)(i)(II) requires
NMFS to issue, in conjunction with its
authorization, binding—and
enforceable—restrictions (in the form of
regulations) setting forth how the
activity must be conducted, thus
ensuring the activity has the ‘‘least
practicable adverse impact’’ on the
affected species or stocks and their
habitat. In situations where mitigation is
specifically needed to reach a negligible
impact determination, section
101(a)(5)(A)(i)(II) also provides a
mechanism for ensuring compliance
with the ‘‘negligible impact’’
requirement.
Finally, as noted above, the least
practicable adverse impact standard
requires consideration of measures for
marine mammal habitat, with particular
attention to rookeries; mating grounds;
and other areas of similar significance,
and for subsistence impacts. By
contrast, the negligible impact standard
is concerned solely with conclusions
about the impact of an activity on
annual rates of recruitment and
survival.14
In NRDC v. Pritzker, the Ninth Circuit
stated, ‘‘[t]he statute is properly read to
mean that even if population levels are
not threatened significantly, still the
agency must adopt mitigation measures
aimed at protecting marine mammals to
14 Mitigation may also be appropriate to ensure
separate compliance with the ‘‘small numbers’’
language and negligible impact standard in MMPA
sections 101(a)(5)(A) and (D).
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the greatest extent practicable in light of
military readiness needs.’’ Pritzker, 828
F.3d at 1134 (emphases added). This
statement is consistent with our
understanding stated above that even
when the effects of an action satisfy the
negligible impact standard (i.e., in the
court’s words, ‘‘population levels are
not threatened significantly’’), still the
agency must prescribe mitigation under
the least practicable adverse impact
standard. However, as the statute
indicates, the focus of both standards is
ultimately the impact on the affected
‘‘species or stock’’; the standards are not
solely focused on or directed at the
impact on individual marine mammals.
NMFS has carefully considered the
Ninth Circuit’s opinion in NRDC v.
Pritzker in its entirety. While the court’s
reference to ‘‘marine mammals’’ rather
than ‘‘marine mammal species or
stocks’’ in the italicized language above
might be construed as a holding that the
least practicable adverse impact
standard applies at the individual
‘‘marine mammal’’ level, i.e., that NMFS
must require mitigation to minimize
impacts to each individual marine
mammal unless impracticable, we
believe that such an interpretation
reflects an incomplete appreciation of
the court’s decision. In NMFS’ view, the
decision as a whole turned on the
court’s determination that the agency
had not given separate and independent
meaning to the least practicable adverse
impact standard apart from the
negligible impact standard. NMFS
further believes that the court’s use of
the term ‘‘marine mammals’’ was not
addressing the question of whether the
standard applies to individual animals
as opposed to the species or stock as a
whole. We recognize that while
consideration of mitigation can play a
role in a negligible impact
determination, consideration of
mitigation measures extends beyond
that analysis. In evaluating what
mitigation measures are appropriate,
NMFS considers the potential impacts
of the specified activity, the availability
of measures to minimize those potential
impacts, and the practicability of
implementing those measures, as
described below.
Implementation of Least Practicable
Adverse Impact Standard
In light of the NRDC v. Pritzker
decision, we discuss here how NMFS
determines whether a measure or set of
measures meets the ‘‘least practicable
adverse impact’’ standard. Our separate
analysis of whether the take anticipated
to result from the specified activities
meets the ‘‘negligible impact’’ standard
appears in the Negligible Impact
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Analysis and Determinations section
below.
NMFS’ evaluation of potential
mitigation measures includes
consideration of two primary factors:
(1) The manner in which, and the
degree to which, implementation of the
potential measure(s) is expected to
reduce adverse impacts to marine
mammal species or stocks, their habitat,
and their availability for subsistence
uses (where relevant). This analysis
considers such things as the nature of
the potential adverse impact (such as
likelihood, scope, and range), the
likelihood that the measure will be
effective if implemented, and the
likelihood of successful
implementation.
(2) The practicability of the measures
for applicant implementation.
Practicability of implementation may
consider such things as cost, impact on
activities, personnel safety, and
practicality of implementation.
While the language of the least
practicable adverse impact standard
calls for minimizing impacts to affected
species or stocks and their habitat,
NMFS recognizes that the reduction of
impacts to those species or stocks
accrues through the application of
mitigation measures that limit impacts
to individual animals. Accordingly,
NMFS’ analysis focuses on measures
that are designed to avoid or minimize
impacts on individual marine mammals
that are likely to increase the probability
or severity of population-level effects.
While direct evidence of impacts to
species or stocks from a specified
activity is rarely available, and
additional study is still needed to
understand how specific disturbance
events affect the fitness of individuals of
certain species, there have been
improvements in understanding the
process by which disturbance effects are
translated to the population. With
recent scientific advancements (both
marine mammal energetic research and
the development of energetic
frameworks), the relative likelihood or
degree of impacts on species or stocks
may often be inferred given a detailed
understanding of the activity, the
environment, and the affected species or
stocks. This same information is used in
the development of mitigation measures
and helps us understand how mitigation
measures contribute to lessening effects
(or the risk thereof) to species or stocks.
NMFS also acknowledges that there is
always the potential that new
information, or a new recommendation
that had not previously been
considered, becomes available and
necessitates re-evaluation of mitigation
measures (which may be addressed
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through adaptive management) to see if
further reductions of population
impacts are possible and practicable.
In the evaluation of specific measures,
the details of the specified activity will
necessarily inform each of the two
primary factors discussed above
(expected reduction of impacts and
practicability) and are carefully
considered to determine the types of
mitigation that are appropriate under
the least practicable adverse impact
standard. Analysis of how a potential
mitigation measure may reduce adverse
impacts on a marine mammal stock or
species and practicability of
implementation are not issues that can
be meaningfully evaluated through a
yes/no lens. The manner in which, and
the degree to which, implementation of
a measure is expected to reduce
impacts, as well as its practicability, can
vary widely. For example, a time-area
restriction could be of very high value
for reducing the potential for, or severity
of, population-level impacts (e.g.,
avoiding disturbance of feeding females
in an area of established biological
importance) or it could be of lower
value (e.g., decreased disturbance in an
area of high productivity but of less
firmly established biological
importance). Regarding practicability, a
measure might involve restrictions in an
area or time that impede the operator’s
ability to acquire necessary data (higher
impact), or it could mean incremental
delays that increase operational costs
but still allow the activity to be
conducted (lower impact). A
responsible evaluation of ‘‘least
practicable adverse impact’’ will
consider the factors along these realistic
scales. Expected effects of the activity
and of the mitigation as well as status
of the stock all weigh into these
considerations. Accordingly, the greater
the likelihood that a measure will
contribute to reducing the probability or
severity of adverse impacts to the
species or stock or their habitat, the
greater the weight that measure is given
when considered in combination with
practicability to determine the
appropriateness of the mitigation
measure, and vice versa. Consideration
of these factors is discussed in greater
detail below.
1. Reduction of adverse impacts to
marine mammal species or stocks and
their habitat.15
15 NMFS recognizes the least practicable adverse
impact standard requires consideration of measures
that will address minimizing impacts on the
availability of the species or stocks for subsistence
uses where relevant. Because subsistence uses are
not implicated for this action, we do not discuss
them. However, a similar framework would apply
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The emphasis given to a measure’s
ability to reduce the impacts on a
species or stock considers the degree,
likelihood, and context of the
anticipated reduction of impacts to
individuals (and how many individuals)
as well as the status of the species or
stock.
The ultimate impact on any
individual from a disturbance event
(which informs the likelihood of
adverse species- or stock-level effects) is
dependent on the circumstances and
associated contextual factors, such as
duration of exposure to stressors.
Though any proposed mitigation needs
to be evaluated in the context of the
specific activity and the species or
stocks affected, measures with the
following types of effects have greater
value in reducing the likelihood or
severity of adverse species- or stocklevel impacts: Avoiding or minimizing
injury or mortality; limiting interruption
of known feeding, breeding, mother/
young, or resting behaviors; minimizing
the abandonment of important habitat
(temporally and spatially); minimizing
the number of individuals subjected to
these types of disruptions; and limiting
degradation of habitat. Mitigating these
types of effects is intended to reduce the
likelihood that the activity will result in
energetic or other types of impacts that
are more likely to result in reduced
reproductive success or survivorship. It
is also important to consider the degree
of impacts that are expected in the
absence of mitigation in order to assess
the added value of any potential
measures. Finally, because the least
practicable adverse impact standard
gives NMFS discretion to weigh a
variety of factors when determining
appropriate mitigation measures and
because the focus of the standard is on
reducing impacts at the species or stock
level, the least practicable adverse
impact standard does not compel
mitigation for every kind of take, or
every individual taken, if that mitigation
is unlikely to meaningfully contribute to
the reduction of adverse impacts on the
species or stock and its habitat, even
when practicable for implementation by
the applicant.
The status of the species or stock is
also relevant in evaluating the
appropriateness of potential mitigation
measures in the context of least
practicable adverse impact. The
following are examples of factors that
may (either alone, or in combination)
result in greater emphasis on the
for evaluating those measures, taking into account
both the MMPA’s directive that we make a finding
of no unmitigable adverse impact on the availability
of the species or stocks for taking for subsistence,
and the relevant implementing regulations.
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importance of a mitigation measure in
reducing impacts on a species or stock:
the stock is known to be decreasing or
status is unknown, but believed to be
declining; the known annual mortality
(from any source) is approaching or
exceeding the PBR level; the affected
species or stock is a small, resident
population; or the stock is involved in
a UME or has other known
vulnerabilities, such as recovering from
an oil spill.
Habitat mitigation, particularly as it
relates to rookeries, mating grounds, and
areas of similar significance, is also
relevant to achieving the standard and
can include measures such as reducing
impacts of the activity on known prey
utilized in the activity area or reducing
impacts on physical habitat. As with
species- or stock-related mitigation, the
emphasis given to a measure’s ability to
reduce impacts on a species or stock’s
habitat considers the degree, likelihood,
and context of the anticipated reduction
of impacts to habitat. Because habitat
value is informed by marine mammal
presence and use, in some cases there
may be overlap in measures for the
species or stock and for use of habitat.
NMFS considers available
information indicating the likelihood of
any measure to accomplish its objective.
If evidence shows that a measure has
not typically been effective nor
successful, then either that measure
should be modified or the potential
value of the measure to reduce effects
should be lowered.
2. Practicability.
Factors considered may include those
costs, impact on activities, personnel
safety, and practicality of
implementation.
In carrying out the MMPA’s mandate
for this action, NMFS applies the
previously described context-specific
balance between the manner in which
and the degree to which measures are
expected to reduce impacts to the
affected species or stocks and their
habitat and practicability for operators.
The effects of concern (i.e., those with
the potential to adversely impact
species or stocks and their habitat),
addressed previously in the Potential
Effects of the Specified Activity on
Marine Mammals and Their Habitat
section of the notice of proposed
rulemaking, include auditory injury,
severe behavioral reactions, disruptions
of critical behaviors, and to a lesser
degree, masking and impacts on
acoustic habitat (see discussion of this
concept in the ‘‘Anticipated Effects on
Marine Mammal Habitat’’ section in the
notice of proposed rulemaking). Here,
we focus on measures with proven or
reasonably presumed ability to avoid or
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reduce the intensity of acute exposures
that have potential to result in these
anticipated effects with an
understanding of the drawbacks or costs
of these requirements, as well as timearea restrictions that would avoid or
reduce both acute and chronic impacts.
To the extent of the information
available to NMFS, we considered
practicability concerns, as well as
potential undesired consequences of the
measures, e.g., extended periods using
the acoustic source due to the need to
reshoot lines. NMFS also recognizes that
instantaneous protocols, such as
shutdown requirements, are not capable
of avoiding all acute effects, and are not
suitable for avoiding many cumulative
or chronic effects and do not provide
targeted protection in areas of greatest
importance for marine mammals.
Therefore, in addition to a basic suite of
seismic mitigation protocols, we also
consider measures that may or may not
be appropriate for other activities (e.g.,
time-area restrictions specific to the
surveys discussed herein), but that are
warranted here given the spatial scope
of these specified activities, potential for
population-level effects and/or high
magnitude of take for certain species in
the absence of such mitigation (see
Negligible Impact Analysis and
Determinations), and the information
we have regarding habitat for certain
species.
In order to satisfy the MMPA’s least
practicable adverse impact standard,
NMFS evaluated a suite of basic
mitigation protocols that are required
regardless of the status of a stock.
Additional or enhanced protections are
required for species whose stocks are in
particularly poor health and/or are
subject to some significant additional
stressor that lessens that stock’s ability
to weather the effects of the specified
activities without worsening its status.
NMFS reviewed the mitigation
measures proposed in the petition, the
requirements specified in BOEM’s PEIS,
seismic mitigation protocols required or
recommended elsewhere (e.g., HESS,
1999; DOC, 2013; IBAMA, 2018; Kyhn
et al., 2011; JNCC, 2017; DEWHA, 2008;
BOEM, 2016; DFO, 2008; GHFS, 2015;
MMOA, 2016; Nowacek et al., 2013;
Nowacek and Southall, 2016),
recommendations received during the
public comment period, and the
available scientific literature. NMFS
also considered recommendations given
in a number of review articles (e.g., Weir
and Dolman, 2007; Compton et al.,
2008; Parsons et al., 2009; Wright and
Cosentino, 2015; Stone, 2015b). Certain
changes from the mitigation measures
described in the notice of proposed
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rulemaking were made on the basis of
additional information and following
review of public comments. The
required suite of mitigation measures
differs in some cases from the measures
proposed in the petition and/or those
specified by BOEM in the preferred
alternative identified in their PEIS in
order to reflect what NMFS believes to
be the most appropriate suite of
measures to satisfy the requirements of
the MMPA. Additionally, two
geographic mitigation measures
discussed in the proposed rule are no
longer applicable because of the change
in the scope of the rule.
For purposes of defining mitigation
requirements, we differentiate here
between requirements for two classes of
airgun survey activity: Deep penetration
and shallow penetration, with surveys
using arrays greater than 1,500 in3 total
airgun volume considered deep
penetration. This delineation is
discussed further below, under
‘‘Changes from the Proposed
Regulations.’’ Shallow penetration
surveys also include those using single
airguns, boomers, or equivalent sources.
A third general class of surveys is also
considered, referred to here as highresolution geophysical (HRG) surveys
and including those surveys using the
other electromechanical sources
described previously. HRG surveys are
treated differentially on the basis of
water depth, with 200 m as the divider
between shallow and deep HRG. Water
depth is used as an indicator for surveys
(shallow) that should be expected to
have less potential for impacts to marine
mammals, because HRG sources used in
shallow waters are typically higherfrequency, lower power, and/or having
some significant directionality to the
beam pattern. Finally, HRG surveys
using only sources operating at
frequencies greater than or equal to 180
kHz are exempt from the mitigation
requirements described herein, with the
exception of adherence to vessel strike
avoidance protocols. (Note that this has
been changed from 200 kHz to reflect
the best available scientific information
regarding generalized hearing ranges for
affected marine mammal hearing groups
(NMFS, 2018).) No distinction in
standard required mitigations is made
on the basis of BOEM’s planning areas
(i.e., Western Planning Area (WPA),
Central Planning Area (CPA), Eastern
Planning Area (EPA)).
First, we summarize notable changes
made to the mitigation requirements as
a result of review of public comments
and/or new information and then
describe mitigation prescribed in the
regulations. For additional detail
regarding mitigation considerations,
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including expected efficacy and/or
practicability, or descriptions of
mitigation considered but not required,
please see the notice of proposed
rulemaking. Where the practicability
analysis was described in the notice of
proposed rulemaking and nothing has
changed, we do not repeat the
description.
Changes to Mitigation From the
Proposed Regulations
Here we summarize substantive
changes to mitigation requirements from
the proposed regulations. All changes
were made on the basis of review of
public comments received and/or
review of new information.
Delineation of Airgun Activity Tiers
In the notice of proposed rulemaking,
for purposes of prescribing mitigation,
NMFS proposed to define ‘‘deep
penetration’’ surveys as those using
arrays greater than 400 in3 total volume.
As stated in that notice, NMFS had little
information upon which to base such a
delineation for purposes of defining
appropriate mitigation, but considered
400 in3 as a reasonable cutoff based on
descriptions of airgun surveys provided
in BOEM’s petition. We also noted that
the Associations stated in their
comments on the petition that deep
penetration array volumes used in the
GOM range from approximately 2,000 to
8,400 in3. BOEM has subsequently
provided information to NMFS
supporting a cutoff at 1,500 in3. In
support of section 3(c) of E.O. 13795,
BOEM analyzed available data for single
airguns and airgun arrays, including
arrays with known characteristics used
by the National Science Foundation and
U.S. Geological Survey and arrays
evaluated through BOEM NEPA
analyses. See e.g., Richardson et al.
(1995); NSF and USGS (2011). These
data suggest that the output of an array,
in terms of peak source level, increases
at a greater rate at volumes above
approximately 1,500 in3. No public
comments addressing this issue were
received. Therefore, NMFS has elected
to redefine the transition from ‘‘shallow
penetration’’ to ‘‘deep penetration’’ from
400 to 1,500 in3 total volume of the
array.
Time-Area Restrictions
Bryde’s Whale Core Habitat Area: The
proposed regulatory text included a
seasonal restriction within an area we
termed Bryde’s whale core habitat, and
the preamble for the proposed rule
presented several alternatives to the
seasonal restriction for consideration by
the public (83 FR 29281; 29302)
including a year-round closure for this
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5409
area, which was considered in the
analysis for the preliminary
determination of negligible impact. See
83 FR 29280–29281; 83 FR 29297.
However, the entirety of this area is
now excluded from consideration
through this rule following BOEM’s
update to the scope of activity (i.e.,
removal of the GOMESA moratorium
area from the geographic scope of the
rulemaking). Therefore, consideration of
a time-area restriction for the Bryde’s
whale core habitat area (including the
alternatives described above) is moot,
and no restriction is included in this
final rule.
Dry Tortugas Area: As with the
Bryde’s whale core habitat area, the
entirety of the Dry Tortugas area is now
excluded from consideration through
this rule following BOEM’s update to
the scope of activity (i.e., removal of the
GOMESA moratorium area from the
geographic scope of the rulemaking).
Therefore, consideration of a time-area
restriction for the biologically important
area for sperm whales and beaked
whales in the EPA is moot, and no
restriction is included in this final rule.
Coastal Restriction: NMFS proposed a
GOM-wide restriction within coastal
waters inside the 20-m isobath, to be in
effect from February through May. For
this final rule, NMFS contracted the
proposed coastal time-area restriction
spatially and expanded it temporally.
The restriction has been reduced to
cover the same coastal waters (20-m
isobath) but between 90° W and the
eastern extent of the coastal waters
portion of BOEM’s updated specified
geographic region, while expanding
temporally to include the month of
January. NMFS received informative
public comment on both sides of this
issue. Some commenters provided
information indicating practicability
concerns regarding the proposed
restriction, while other commenters
supported the importance of the
restriction and provided information
supporting the temporal expansion of
the restriction to include January. As
described in the notice of proposed
rulemaking, the stock most heavily
impacted by the DWH oil spill (of those
that may be affected by the specified
activities) was the northern coastal stock
of bottlenose dolphin. Since publication
of the proposed regulations, an
additional UME occurred in the area
largely overlapping the range of this
stock. Therefore, while NMFS
appreciates the practicability concerns
raised by commenters, we contracted
the restriction spatially but did not
eliminate the restriction, while
expanding it temporally to encompass
January through May. The change is
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described in more detail under
Comments and Responses as well as
later in this section where the details of
the specific closure area is discussed.
Restriction Area Buffer Zones: The
proposed regulations included buffer
zones specific to each time-area
restriction that corresponded with
modeled distances to the 160-dB
isopleth (i.e., the midpoint of the Level
B harassment risk function). These
distances were 6 km around the EPA
Bryde’s whale core habitat area (Area
#2), 13 km around the coastal waters
restriction (Area #1), and 9 km around
the southern EPA area (Area #3).
Following BOEM’s update to the
geographic scope of activity considered
through this rule, Areas 2 and 3 are
excluded from consideration. Therefore,
consideration of buffer zone size around
these areas is not relevant. Upon review
of public comment, in which
commenters raised concerns about
practicability among others, and reevaluation of the nature and extent of
mitigation Area #1 as it relates to the
necessity of an additional buffer area,
NMFS determined it appropriate to not
include a buffer for this area. The
rationale for the change is described in
more detail under Comments and
Responses.
Shutdown Requirements
Delphinid Exception: NMFS does not
require shutdown or power-down for
certain delphinid species. In the notice
of proposed rulemaking, we proposed
an exception to the general shutdown
requirements for certain species of
dolphins in relation to airgun surveys,
in which the acoustic source would be
powered down to the smallest single
element of the array. Power-down
conditions would be maintained until
the animal(s) is observed exiting the
exclusion zone or for 15 minutes
beyond the last observation of the
animal, following which full-power
operations may be resumed without
ramp-up. NMFS also provided an
alternative proposal for consideration by
the public, in which no shutdown or
power-down would be required upon
observation of the same species of
dolphins. While we are careful to note
that the reasons for and potential effects
of dolphin interaction with vessels,
including working survey vessels, are
not fully understood, we also
understand that dolphins are unlikely to
incur any degree of threshold shift due
to their relative lack of sensitivity to the
frequency content in an airgun signal (as
well as because of potential coping
mechanisms). NMFS also recognizes
that, although dolphins do in fact react
to airgun noise in ways that may be
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considered take (Barkaszi et al., 2012;
Barkaszi and Kelly, 2018), there is a lack
of notable adverse dolphin reactions to
airgun noise despite a large body of
observational data. Therefore, the
removal of the power-down measure for
small delphinids, in favor of the noshutdown or power-down alternative, is
warranted in consideration of the
available information regarding the
effectiveness of such measures in
mitigating impacts to small delphinids
and the practicability of such measures.
No shutdown or power-down is
required for these species.
Distance of Extended Shutdowns:
NMFS limits extended distance
shutdowns to within 1,500 m. We
proposed a number of shutdown
requirements on the basis of detections
of certain species deemed particularly
sensitive (e.g., beaked whales) or of
particular circumstances deemed to
warrant particular caution (e.g., whales
with calves). These were all conditioned
upon observation or detection of these
species or circumstances at any distance
from the vessel. However, NMFS also
included as an alternative proposal for
public consideration a distance limit of
1,000 m for these extended distance
shutdown requirements. We received
several comments challenging the value
of extended distance shutdown
requirements at all and, while NMFS
disagrees with these comments, we
agree that some reasonable distance
limit should be placed on these
requirements in order to better focus the
observational effort of protected species
observers (PSO) and to avoid the
potential for numerous shutdowns
based on uncertain detections at great
distance. Therefore, as described in
greater detail later in this section, NMFS
determined that a limit on such
extended distance shutdown zones for
relevant species or circumstances was
appropriate. However, upon
consideration of additional information
(discussed later in this section), NMFS
determined it appropriate to limit
extended distance shutdown zones to
1,500 m, rather than 1,000 m.
Sperm Whale Shutdowns: The
proposed regulatory text included an
extended distance shutdown upon
acoustic detection of sperm whales, and
this final ITR explicitly expands that
requirement to include any detection of
sperm whales (i.e., including visual
detection) at extended distance (i.e.,
within 1,500 m). As discussed in
Comments and Responses, NMFS
received some comments showing that
there was a lack of clarity regarding the
extended distance shutdowns for
acoustic detections of sperm whales.
NMFS also received comments
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indicating that the proposed division
(i.e., extended distance shutdown upon
acoustic detection of sperm whales but
not visual detection) did not make sense
given the available information
regarding both the status of the GOM
sperm whale population and the
potential impacts of airgun noise on
sperm whale foraging activity. While
this measure does not avoid such
impacts—the observed impacts on
foraging behavior were at even greater
distances (Miller et al., 2009)—it may be
expected to practicably reduce the
occurrence and severity of impacts on
foraging behavior.
Shallow Penetration Surveys: NMFS
has reduced the standard exclusion
zone from 200 m to 100 m, and included
an extended distance shutdown
requirement that mirrors the
requirements for deep penetration
surveys but out to a distance of 500 m.
The 200-m shutdown distance was
proposed on the basis of BOEM’s HRG
survey protocol (Appendix B of BOEM,
2017). However, practicability concerns
were raised by public commenters and
100-m shutdown zones have been
effectively applied in the past to afford
protection from potential Level A
harassment and more severe behavioral
responses from these types of activities.
Therefore, rather than defer to BOEM’s
HRG survey protocol, NMFS reevaluated the same information
informing development of the proposed
rule, as well as public comment, and
determined that the 200-m shutdown
distance is not warranted and we reduce
the distance accordingly. Regarding the
extended distance shutdown in special
circumstances, NMFS proposed this
mitigation concept in context of deep
penetration surveys in the notice of
proposed rulemaking. Airgun (and
equivalent) surveys are considered to
have similar effects on exposed marine
mammals, and the sensitive species for
which the extended distance shutdown
measure was proposed are similarly
susceptible to disturbance from shallow
penetration surveys, if exposed.
Therefore, NMFS expands the extended
distance shutdown measure to shallow
penetration surveys in addition to deep
penetration surveys.
HRG Surveys: NMFS eliminates
shutdown requirements for HRG
surveys (defined here as surveys using
electromechanical sources such as
multi-beam echosounders, side-scan
sonars, and chirp sub-bottom profilers).
The proposed regulations required
shutdown for marine mammals within
the proposed exclusion zone for surveys
operating in water depths greater than
200 m. As discussed above for shallow
penetration surveys, this proposal was
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modeled after BOEM’s HRG survey
protocol. However, NMFS re-evaluated
the available information, as well as
public comment, and has determined
the requirement to not be warranted.
These sources are typically higherfrequency and lower-power, and have
highly directional beam patterns. Effects
to marine mammals due to use of these
sources, if any, are expected to be of
very low severity and, therefore, the
benefits of the proposed shutdown
requirement would be minimal
(especially given that animals observed
at the surface are necessarily not
ensonified by the downward-directed
beams from the source at the time they
are observed).
Monitoring
Nighttime Ramp-Up: NMFS
eliminates the requirement for visual
observation during nighttime ramp-up
and pre-clearance. Public commenters
indicated that this measure is not likely
to be effective, and that there are safety
concerns associated with PSOs working
on deck at night. NMFS concurs with
this assessment, as described in detail in
Comments and Responses.
PSOs for Node Retrieval: The
proposed requirement for third-party
PSOs aboard node retrieval vessels is
eliminated due to practicability
concerns expressed through public
comment. NMFS concurs with this
assessment, as described in detail in
Comments and Responses.
Below, mitigation requirements are
described in detail.
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Mitigation-Related Monitoring
Monitoring by dedicated, trained
marine mammal observers is required in
all water depths and, for certain
surveys, observers must be independent.
Additionally, for some surveys, NMFS
requires that some PSOs 16 have prior
experience in the role. Independent
observers are employed by a third-party
observer provider; vessel crew may not
serve as PSOs when independent
observers are required. Dedicated
observers are those who have no tasks
other than to conduct observational
effort, record observational data, and
communicate with and instruct the
survey operator (i.e., vessel captain and
crew) with regard to the presence of
marine mammals and mitigation
requirements. Communication with the
operator may include brief alerts
regarding maritime hazards. Trained
PSOs have successfully completed an
approved PSO training course (see
16 Note that, although we discuss requirements
related only to observation of marine mammals, we
use the generic term ‘‘protected species observer.’’
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Monitoring and Reporting), and
experienced PSOs have additionally
gained a minimum of 90 days at-sea
experience working as a PSO during a
deep penetration seismic survey, with
no more than 18 months having elapsed
since the conclusion of the relevant atsea experience. Training and experience
is specific to either visual or acoustic
PSO duties (where required). An
experienced visual PSO must have
completed approved, relevant training
and must have gained the requisite
experience working as a visual PSO. An
experienced acoustic PSO must have
completed a passive acoustic
monitoring (PAM) operator training
course and must have gained the
requisite experience working as an
acoustic PSO. Hereafter, we also refer to
acoustic PSOs as PAM operators,
whereas when we use ‘‘PSO’’ without a
qualifier, the term refers to either visual
PSOs or PAM operators (acoustic PSOs).
NMFS does not formally administer
any PSO training program or endorse
specific providers but will approve
PSOs that have successfully completed
courses that meet the curriculum and
trainer requirements specified herein
(see Monitoring and Reporting). NMFS
will provide PSO approvals in the
context of the need to ensure that PSOs
have the necessary training to carry out
their duties competently while also
approving applicant staffing plans
quickly. In order for PSOs to be
approved, NMFS must review and
approve PSO resumes indicating
successful completion of an acceptable
training course. Although PSOs must be
approved by NMFS, third-party observer
providers and/or companies seeking
PSO staffing should expect that
observers having satisfactorily
completed acceptable training and with
the requisite experience (if required)
will be quickly approved and, if NMFS
does not respond within one week of
having received the required
information, such PSOs shall be
considered to have received de facto
approval. A PSO may be trained and/or
experienced as both a visual PSO and
PAM operator and may perform either
duty, pursuant to scheduling
requirements. Where multiple PSOs are
required and/or PAM operators are
required, PSO watch schedules shall be
devised in consideration of the
following restrictions: (1) A maximum
of two consecutive hours on watch
followed by a break of at least one hour
between watches for visual PSOs
(periods typical of observation for
research purposes and as used for
airgun surveys in certain circumstances
(Broker et al., 2015)); (2) a maximum of
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5411
four consecutive hours on watch
followed by a break of at least two
consecutive hours between watches for
PAM operators; and (3) a maximum of
12 hours observation per 24-hour
period. NMFS may grant an exception
for the requirement that visual PSOs be
limited to a maximum of two
consecutive hours on watch followed by
a break of at least one hour between
watches if requested on the basis of
practicability concerns by LOA
applicants. If an exception is granted,
visual PSOs would instead be limited to
a maximum of four consecutive hours
on watch followed by a break of at least
two hours between watches. Further
information regarding PSO requirements
may be found in the Monitoring and
Reporting section, later in this
document.
Deep Penetration Surveys—During
deep penetration survey 17 operations
(e.g., any day on which use of the
acoustic source is planned to occur;
whenever the acoustic source is in the
water, whether activated or not), a
minimum of two independent PSOs
must be on duty and conducting visual
observations at all times during daylight
hours (i.e., from 30 minutes prior to
sunrise through 30 minutes following
sunset). PSOs should use NOAA’s solar
calculator (www.esrl.noaa.gov/gmd/
grad/solcalc/) to determine sunrise and
sunset times at their specific location.
NMFS recognizes that certain daytime
conditions (e.g., fog, heavy rain) may
reduce or eliminate effectiveness of
visual observations. However, on-duty
PSOs shall remain alert for marine
mammal observational cues and/or a
change in conditions.
All source vessels must carry a
minimum of one experienced visual
PSO, who shall be designated as the
lead PSO, coordinate duty schedules
and roles,18 and serve as the primary
point of contact for the operator.
However, while it is desirable for all
PSOs to be qualified through
experience, NMFS is also mindful of the
need to expand the workforce by
allowing opportunity for newly trained
PSOs to gain experience. Therefore, the
lead PSO shall devise the duty schedule
such that experienced PSOs are on duty
with trained PSOs (i.e., those PSOs with
appropriate training but who have not
yet gained relevant experience) to the
maximum extent practicable in order to
provide necessary mentorship.
17 Deep penetration surveys are defined as those
surveys using airgun arrays with total volume
greater than 1,500 in3.
18 The coordination of PSO duty schedules and
roles may alternatively be performed by a thirdparty, shore-based Monitoring Coordinator.
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With regard to specific observational
protocols, NMFS largely follows those
described in Appendix B of BOEM’s
PEIS (BOEM, 2017). The lead PSO shall
determine the most appropriate
observation posts that will not interfere
with navigation or operation of the
vessel while affording an optimal,
elevated view of the sea surface. These
should be the highest elevation
available on each vessel, with the
maximum viewable range from the bow
to 90 degrees to port or starboard of the
vessel. PSOs shall coordinate to ensure
360° visual coverage around the vessel,
and shall conduct visual observations
using binoculars and the naked eye
while free from distractions and in a
consistent, systematic, and diligent
manner. All source vessels must be
equipped with pedestal-mounted
‘‘bigeye’’ binoculars that will be
available for PSO use. Within these
broad outlines, the lead PSO and PSO
team will have discretion to determine
the most appropriate vessel- and surveyspecific system for implementing
effective marine mammal observational
effort. Any observations of marine
mammals by crew members aboard any
vessel associated with the survey,
including receiver or chase vessels,
should be relayed to the source vessel(s)
and to the PSO team.
All source vessels must use a towed
PAM system for potential detection of
marine mammals at all times when
operating the sound source in waters
deeper than 100 m. The term ‘‘towed
PAM system’’ refers to any combination
of hardware and software that uses a
towed array for operations. The array
can be physically separate from other
in-water hardware, or embedded into
other equipment, such as seismic
streamers. The system must be
monitored at all times during use of the
acoustic source, and acoustic
monitoring must begin at least 30
minutes prior to ramp-up. PAM
operators must be independent, and all
source vessels shall carry a minimum of
two experienced PAM operators. PAM
operators shall communicate all
detections to visual PSOs, when visual
PSOs are on duty, including any
determination by the PSO regarding
species identification, distance and
bearing, and the degree of confidence in
the determination. Further detail
regarding PAM system requirements
may be found in the Monitoring and
Reporting section, later in this
document. The effectiveness of PAM
depends to a certain extent on the
equipment and methods used and
competency of the PAM operator, but no
formal standards are currently in place
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regarding PAM system hardware/
software requirements, or regarding
PAM operator training.
Visual monitoring must begin at least
30 minutes prior to ramp-up (described
below) and must continue until one
hour after use of the acoustic source
ceases or until 30 minutes past sunset.
If any marine mammal is observed at
any distance from the vessel, a PSO
would record the observation and
monitor the animal’s position (including
latitude/longitude of the vessel and
relative bearing and estimated distance
to the animal) until the animal dives or
moves out of visual range of the
observer. A PSO would continue to
observe the area to watch for the animal
to resurface or for additional animals
that may surface in the area. Visual
PSOs shall communicate all
observations to PAM operators,
including any determination by the PSO
regarding species identification,
distance, and bearing and the degree of
confidence in the determination.
As noted previously, all source
vessels must carry a minimum of one
experienced visual PSO and two
experienced PAM operators. The
observer designated as lead PSO
(including the full team of visual PSOs
and PAM operators) must have
experience as a visual PSO. The
applicant may determine how many
additional PSOs are required to
adequately fulfill the requirements
specified here. To summarize, these
requirements are: (1) 24-hour acoustic
monitoring during use of the acoustic
source in waters deeper than 100 m; (2)
visual monitoring during use of the
acoustic source by two PSOs during all
daylight hours; (3) maximum of two
consecutive hours on watch followed by
a minimum of one hour off watch for
visual PSOs and a maximum of four
consecutive hours on watch followed by
a minimum of two consecutive hours off
watch for PAM operators; and (4)
maximum of 12 hours of observational
effort per 24-hour period for any PSO,
regardless of duties.
Shallow Penetration Surveys—During
shallow penetration surveys,19 operators
must follow the same requirements
described above for deep penetration
surveys, with one notable exception.
The use of PAM is not required.
HRG Surveys—HRG survey protocols
differ from the previously described
protocols for deep and shallow
penetration surveys, and we
differentiate between deep-water
19 Shallow penetration surveys are defined as
those using airgun arrays with total volume less
than or equal to 1,500 in3, single airguns, boomers,
or equivalent sources.
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(greater than 100 m) and shallow-water
HRG surveys. Water depth in the GOM
provides a reliable indicator of the
marine mammal fauna that may be
encountered and, therefore, the
complexity of likely observations and
concern related to potential effects on
deep-diving and/or sensitive species.
Deep-water HRG surveys are required
to employ a minimum of one
independent visual PSO during all
daylight operations, in the same manner
as was described for deep and shallow
penetration surveys. Shallow-water
HRG surveys are required to employ a
minimum of one visual PSO, which may
be a crew member. PSOs employed
during shallow-water HRG surveys are
only required during a pre-clearance
period. PAM is not required for any
HRG survey.
PAM Malfunction—Emulating
sensible protocols described by the New
Zealand Department of Conservation for
airgun surveys conducted in New
Zealand waters (DOC, 2013), survey
activity may continue for brief periods
of time when the PAM system
malfunctions or is damaged. Activity
may continue for 30 minutes without
PAM while the PAM operator diagnoses
the issue. If the diagnosis indicates that
the PAM system must be repaired to
solve the problem, operations may
continue for an additional two hours
without acoustic monitoring under the
following conditions:
• Daylight hours and sea state is less
than or equal to Beaufort sea state (BSS)
4;
• No marine mammals (excluding
delphinids; see below) detected solely
by PAM in the exclusion zone (see
below) in the previous two hours;
• NMFS is notified via email as soon
as practicable with the time and
location in which operations began
without an active PAM system; and
• Operations with an active acoustic
source, but without an operating PAM
system, do not exceed a cumulative total
of four hours in any 24-hour period.
Exclusion Zone and Buffer Zone
An exclusion zone is a defined area
within which occurrence of a marine
mammal triggers mitigation action
intended to reduce the potential for
certain outcomes such as auditory
injury or more severe disruption of
behavioral patterns. For deep
penetration surveys, the PSOs shall
establish and monitor a 500-m exclusion
zone and additional 500-m buffer zone
(total 1,000 m) during the pre-clearance
period (see below) and a 500-m
exclusion zone during the ramp-up and
operational periods (see below for
description of extended 1,500-m zone in
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special circumstances). PSOs should
generally focus their observational effort
within a 1.5-km zone, to the extent
possible, with animals observed at
greater distances recorded and
mitigation action taken as necessary (see
below). For shallow penetration
surveys, the PSOs shall establish and
monitor a 100-m exclusion zone with
additional 100-m buffer (total 200-m
zone) during the pre-clearance period
and a 100-m exclusion zone during the
ramp-up (for small arrays only, versus
single airguns) and operational periods
(see below for description of extended
500-m zone in special circumstances).
PSOs should generally focus their
observational effort within a 500-m
zone, to the extent possible, with
animals observed at greater distances
recorded and mitigation action taken as
necessary (see below). These zones shall
be based upon radial distance from any
element of the airgun array (rather than
being based on the center of the array
or around the vessel itself). During use
of the acoustic source, occurrence of
marine mammals within the buffer zone
(but outside the exclusion zone) should
be communicated to the operator to
prepare for the potential shutdown of
the acoustic source. Use of the buffer
zone in relation to ramp-up is discussed
below under ‘‘Ramp-up.’’ Further detail
regarding the exclusion zone and
shutdown requirements is given under
‘‘Exclusion Zone and Shutdown
Requirements.’’
Ramp-Up
Ramp-up of an acoustic source is
intended to provide a gradual increase
in sound levels, enabling animals to
move away from the source if the signal
is sufficiently aversive prior to its
reaching full intensity. We infer on the
basis of behavioral avoidance studies
and observations that this measure
results in some reduced potential for
auditory injury and/or more severe
behavioral reactions. Although this
measure is not proven and some
arguments have been made that use of
ramp-up may not have the desired effect
of aversion (which is itself a potentially
negative impact but assumed to be
better than the alternative), ramp-up
remains a relatively low-cost, commonsense component of standard mitigation
for surveys using airgun arrays. Rampup is most likely to be effective for more
sensitive species (e.g., beaked whales)
with known behavioral responses at
greater distances from an acoustic
source (e.g., Tyack et al., 2011; DeRuiter
et al., 2013; Miller et al., 2015). Rampup is required for all surveys using
airgun arrays. While non-airgun
acoustic sources are not typically
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amenable to ‘‘ramping up’’ the acoustic
output in the way that multi-element
airgun arrays are, power to these sources
should be increased as feasible in order
to effect a ramp-up.
The ramp-up procedure involves a
step-wise increase in the number of
airguns firing and total array volume
until all operational airguns are
activated and the full volume is
achieved. Ramp-up is required at all
times as part of the activation of the
acoustic source (including source tests;
see ‘‘Miscellaneous Protocols’’ for more
detail) and may occur at times of poor
visibility, assuming appropriate acoustic
monitoring with no detections in the 30
minutes prior to beginning ramp-up.
Acoustic source activation may only
occur at night where operational
planning cannot reasonably avoid such
circumstances. For example, a nighttime
initial ramp-up following port departure
is reasonably avoidable and may not
occur. Ramp-up must occur at night
following acoustic source deactivation
due to line turn or mechanical
difficulty. The operator must notify a
designated PSO of the planned start of
ramp-up as agreed-upon with the lead
PSO; the notification time should be at
least 60 minutes prior to the planned
ramp-up. A designated PSO must be
notified again immediately prior to
initiating ramp-up procedures and the
operator must receive confirmation from
the PSO to proceed.
Ramp-up procedures follow the
recommendations of IAGC (2015).
Ramp-up begins by activating a single
airgun (i.e., array element) of the
smallest volume in the array. Ramp-up
continues in stages by doubling the
number of active elements at the
commencement of each stage, with each
stage of approximately the same
duration. Total duration should not be
less than approximately 20 minutes but
maximum duration is not prescribed
and will vary depending on the total
number of stages. Von Benda-Beckmann
et al. (2013), in a study of the
effectiveness of ramp-up for sonar,
found that extending the duration of
ramp-up did not have a corresponding
effect on mitigation benefit. There will
generally be one stage in which
doubling the number of elements is not
possible because the total number is not
even. This should be the last stage of the
ramp-up sequence. The operator must
provide information to the PSO
documenting that appropriate
procedures were followed. Ramp-ups
should be scheduled so as to minimize
the time spent with the source activated
prior to reaching the designated run-in.
This approach is intended to ensure a
perceptible increase in sound output per
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increment while employing increments
that produce similar degrees of increase
at each step.
For deep penetration surveys, PSOs
must monitor a 1,000-m zone (or to the
distance visible if less than 1,000 m) for
a minimum of 30 minutes prior to rampup (i.e., pre-clearance). For shallow
penetration surveys, PSOs must monitor
a 200-m zone (or to the distance visible
if less than 200 m) for a minimum of 30
minutes prior to ramp-up or start-up (for
single airgun or non-airgun surveys).
(Note that extended distance
shutdowns, discussed below, may be
required if certain species or
circumstances are detected within
greater distances: 1.5 km for deep
penetration surveys and 500 m for
shallow penetration surveys). The preclearance period may occur during any
vessel activity (i.e., transit, line turn).
Ramp-up must be planned to occur
during periods of good visibility when
possible; operators may not target the
period just after visual PSOs have gone
off duty. Following deactivation of the
source for reasons other than mitigation,
the operator must communicate the
near-term operational plan to the lead
PSO with justification for any planned
nighttime ramp-up. Any suspected
patterns of abuse by the operator must
be reported by the lead PSO to be
investigated by NMFS. Ramp-up may
not be initiated if any marine mammal
is within the designated zone. If a
marine mammal is observed within the
zone during the pre-clearance period,
ramp-up may not begin until the
animal(s) has been observed exiting the
zone or until an additional time period
has elapsed with no further sightings
(i.e., 15 minutes for small delphinids
and 30 minutes for all other species).
PSOs will monitor the exclusion zone
during ramp-up, and ramp-up must
cease and the source shut down upon
observation of marine mammals within
or approaching the zone.
Exclusion Zone and Shutdown
Requirements
Deep Penetration Surveys—The PSOs
must establish a minimum exclusion
zone with a 500-m radius as a perimeter
around the outer extent of the airgun
array (rather than being delineated
around the center of the array or the
vessel itself). If a marine mammal (other
than the small delphinid species
discussed below) appears within or
enters this zone, the acoustic source
must be shut down (i.e., power to the
acoustic source must be immediately
turned off). If a marine mammal is
detected acoustically, the acoustic
source must be shut down, unless the
PAM operator is confident that the
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animal detected is outside the exclusion
zone or that the detected species is not
subject to the shutdown requirement
(see below).
The 500-m radial distance of the
standard exclusion zone is expected to
contain sound levels exceeding peak
pressure injury criteria for all hearing
groups other than, potentially, highfrequency cetaceans, while also
providing a consistent, reasonably
observable zone within which PSOs
would typically be able to conduct
effective observational effort. Although
significantly greater distances may be
observed from an elevated platform
under good conditions, NMFS believes
that 500 m is likely regularly attainable
for PSOs using the naked eye during
typical conditions. In addition, an
exclusion zone is expected to be helpful
in avoiding more severe behavioral
responses. Behavioral response to an
acoustic stimulus is determined not
only by received level but by context
(e.g., activity state) including,
importantly, proximity to the source
(e.g., Southall et al., 2007; Ellison et al.,
2012; DeRuiter et al., 2013). In
prescribing an exclusion zone, NMFS
seeks not only to avoid most potential
auditory injury but also to reduce the
likely severity of the behavioral
response at a given received level of
sound.
As discussed in the notice of
proposed rulemaking, use of monitoring
and shutdown measures within defined
exclusion zone distances is inherently
an essentially instantaneous
proposition—a rule or set of rules that
requires mitigation action upon
detection of an animal. This indicates
that defining an exclusion zone on the
basis of thresholds related to the
accumulation of energy (i.e., cumulative
SEL), which require that an animal
accumulate some level of sound energy
exposure over some period of time (e.g.,
24 hours), has questionable relevance as
a standard protocol for mobile sources,
given the relative motion of the source
and the animals. A PSO aboard a mobile
source will typically have no ability to
monitor an animal’s position relative to
the acoustic source over relevant time
periods for purposes of understanding
whether auditory injury is likely to
occur on the basis of cumulative sound
exposure and, therefore, whether action
should be taken to avoid such potential.
Cumulative SEL (cSEL) thresholds are
more relevant for purposes of modeling
the potential for auditory injury than
they are for dictating real-time
mitigation, though they can be
informative (especially in a relative
sense). NMFS recognizes the importance
of the accumulation of sound energy to
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an understanding of the potential for
auditory injury and that it is likely that,
at least for low-frequency cetaceans,
some potential auditory injury may be
impossible to fully avoid, depending on
survey location in relation to the areas
where these species occur, and should
be considered for authorization.
Considering both the dual-metric
thresholds described previously (and
shown in Table 7) and hearing groupspecific marine mammal auditory
weighting functions in the context of
airgun sources, auditory injury zones
indicated by the peak pressure metric
are expected to be predominant for both
mid- and high-frequency cetaceans,
while zones indicated by cSEL criteria
are expected to be predominant for lowfrequency cetaceans. Assuming a source
level of 255.2 dB 0-pk SPL for the
notional 8,000 in3 array and spherical
spreading propagation, distances for
exceedance of group-specific peak
injury thresholds are as follows: 65 m
(LF), 18 m (MF), and 457 m (HF) (for
high-frequency cetaceans, although the
notional source parameters indicate a
zone less than 500 m, we recognize that
actual isopleth distances will vary based
on specific array characteristics and
site-specific propagation characteristics,
and that it is therefore possible that a
real-world distance to the injury
threshold could exceed 500 m).
Assuming a source level of 227.7 dB
0-pk SPL for the notional 90 in3 single
airgun and spherical spreading
propagation, these distances would be
3 m (LF) and 19 m (HF) (the source level
is lower than the threshold criterion
value for mid-frequency cetaceans).
These specific modeled source level
values were discussed in the notice of
proposed rulemaking, and additional
information may be found in the
modeling report.
Consideration of auditory injury
zones based on cSEL criteria is
dependent on the animal’s generalized
hearing range and how it overlaps with
the frequencies produced by the sound
source of interest in relation to marine
mammal auditory weighting functions
(NMFS, 2018). As noted above, zones
based on the cSEL threshold are
expected to be predominant for lowfrequency cetaceans because their most
susceptible hearing range overlaps the
low frequencies produced by airguns,
while the modeling indicates that zones
based on peak pressure criteria
dominate for mid- and high-frequency
cetaceans. As described in detail in the
notice of proposed rulemaking, NMFS
obtained unweighted spectrum data
(modeled in 1 Hz bands) for a
reasonably equivalent acoustic source
(i.e., a 36-airgun array with total volume
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of 6,600 in3) in order to evaluate
notional zone sizes and to incorporate
NMFS’ Technical Guidance weighting
functions over an airgun array’s full
acoustic band. Using NMFS’ associated
User Spreadsheet with hearing groupspecific weighted source levels, and
inputs assuming a 231.8 dB SEL source
level for the notional 8,000 in3 array,
spherical spreading propagation, a
source velocity of 4.5 kn, pulse duration
of 100 ms, and a 25-m shot interval
(shot intervals may vary, with longer
shot intervals resulting in smaller
calculated zones), distances for groupspecific threshold criteria are as follows:
574 m (LF), 0 m (MF), and 1 m (HF).
NMFS also assessed the potential for
injury based on the accumulation of
energy resulting from use of the single
airgun and, assuming a source level of
207.8 dB SEL, there would be no
realistic zone within which injury
would occur.
Therefore, the 500-m exclusion zone
contains the entirety of any potential
injury zone for mid-frequency cetaceans
(realistically, there is no such zone, as
discussed above in Estimated Take and
in Comments and Responses), while the
zones within which injury could occur
may be larger for high-frequency
cetaceans (on the basis of peak pressure
and depending on the specific array)
and for low-frequency cetaceans (on the
basis of cumulative sound exposure).
In summary, NMFS’ goal in
prescribing a standard exclusion zone
distance is to (1) encompass zones for
most species within which auditory
injury could occur on the basis of
instantaneous exposure; (2) provide
protection from the potential for more
severe behavioral reactions (e.g., panic,
antipredator response) for marine
mammals at relatively close range to the
acoustic source; (3) enable more
effective implementation of required
mitigation by providing consistency and
ease of implementation for PSOs, who
need to monitor and implement the
exclusion zone; and (4) define a
distance within which detection
probabilities are reasonably high for
most species under typical conditions.
NMFS’ use of 500 m as the zone is not
based directly on any quantitative
understanding of the range at which
auditory injury would be entirely
precluded or any range specifically
related to disruption of behavioral
patterns. Rather, we believe it is a
reasonable combination of factors. This
zone has been proven as a feasible
measure through past implementation
by operators in the GOM. In summary,
a practicable criterion such as this has
the advantage of familiarity and
simplicity while still providing in most
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cases a zone larger than relevant
auditory injury zones, given realistic
movement of source and receiver.
Increased shutdowns, without a firm
idea of the outcome the measure seeks
to avoid, simply displace survey activity
in time and increase the total duration
of acoustic influence as well as total
sound energy in the water (due to
additional ramp-up and overlap where
data acquisition was interrupted). The
shutdown requirement described here
would be required for most marine
mammals, with certain differences.
Small delphinids are excepted from the
shutdown requirement, as described in
the following section. Certain species
are subject to an extended distance
shutdown zone, as described in the
subsequent section entitled ‘‘Other
Shutdown Requirements.’’
Dolphin Exception—The shutdown
requirement described above is in place
for all marine mammals, with the
exception of small delphinids. As
defined here, the small delphinid group
is intended to encompass those
members of the Family Delphinidae
most likely to voluntarily approach the
source vessel for purposes of interacting
with the vessel and/or airgun array (e.g.,
bow-riding). (Here we refer to ‘‘large
delphinids’’ and ‘‘small delphinids’’ as
shorthand for generally deep-diving
versus surface-dwelling/bow-riding
groups, respectively, as the important
distinction is their dive behavior rather
than their size.) This exception to the
shutdown requirement applies solely to
specific genera of dolphins—Steno,
Tursiops, Stenella, and Lagenodelphis
(see Table 4)—and applies under all
circumstances, regardless of what the
perception of the animal(s) behavior or
intent may be. The proposed regulations
included a requirement to conduct a
power-down upon detection of these
species within the exclusion zone.
However, in the preamble to the
proposed regulations, NMFS also
included an alternative proposal for
public review and comment in which
no shutdown or power-down would be
required. We requested comment on
both proposals and other variations of
those proposals, including NMFS’
interpretation of the data and any other
data that support the necessary findings
regarding dolphins for no shutdown and
no power-down or no shutdown but a
power-down. Upon review of the public
comments received, as well as the
scientific information summarized
below, NMFS has determined that the
alternative proposal of no shutdown or
power-down is appropriate, and
satisfies the least practicable adverse
impact requirement.
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Variations of this measure that
include exceptions based on animal
behavior—e.g., ‘‘bow-riding’’ dolphins,
or only ‘‘traveling’’ dolphins, meaning
that the intersection of the animal and
exclusion zone may be due to the
animal rather than the vessel—have
been proposed by both NMFS and
BOEM and have been criticized, in part
due to the subjective on-the-spot
decision-making this scheme would
require of PSOs. If the mitigation
requirements are not sufficiently clear
and objective, the outcome may be
differential implementation across
surveys as informed by individual
PSOs’ experience, background, and/or
training. The exception described here
is based on several factors: The lack of
evidence of or presumed potential for
the types of effects to these species of
small delphinid that our shutdown
requirement for other species seeks to
avoid, the uncertainty and subjectivity
introduced by such a decision
framework, and the practicability
concern presented by the operational
impacts. Despite a large volume of
observational effort during airgun
surveys, including in locations where
dolphin shutdowns have not previously
been required (i.e., the U.S. GOM and
United Kingdom (UK) waters), we are
not aware of accounts of notable adverse
dolphin reactions to airgun noise
(Stone, 2015a; Barkaszi et al., 2012;
Barkaszi and Kelly, 2018) other than one
isolated incident (Gray and Van
Waerebeek, 2011). Dolphins have a
relatively high threshold for the onset of
auditory injury (i.e., PTS) and more
severe adverse behavioral responses
seem less likely given the evidence of
purposeful approach and/or
maintenance of proximity to vessels
with operating airguns.
The best available scientific evidence
indicates that auditory injury as a result
of airgun sources is extremely unlikely
for mid-frequency cetaceans, primarily
due to a relative lack of sensitivity and
susceptibility to noise-induced hearing
loss at the frequency range output by
airguns (i.e., most sound below 500 Hz)
as shown by the mid-frequency cetacean
auditory weighting function (NMFS,
2018). Criteria for TTS in mid-frequency
cetaceans for impulsive sounds were
derived by experimental measurement
of TTS in beluga whales exposed to
pulses from a seismic watergun.
Dolphins exposed to the same stimuli in
this study did not display TTS
(Finneran et al., 2002). Moreover, when
the experimental watergun signal was
weighted appropriately for midfrequency cetaceans, less energy was
filtered than would be the case for an
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airgun signal. More recently, Finneran
et al. (2015) exposed bottlenose
dolphins to repeated pulses from an
airgun and measured no TTS.
NMFS cautions that, while dolphins
are observed voluntarily approaching
source vessels (e.g., bow-riding or
interacting with towed gear), the reasons
for the behavior are unknown. In
context of an active airgun array, the
behavior cannot be assumed to be
harmless. Although bow-riding
comprises approximately 30 percent of
behavioral observations in the GOM,
there is a much lower incidence of the
behavior when the acoustic source is
active (Barkaszi et al., 2012), and this
finding was replicated by Stone (2015a)
for surveys occurring in UK waters.
Some studies have found evidence of
aversive behavior by dolphins during
firing of airguns. Barkaszi et al. (2012)
found that the median closest distance
of approach to the acoustic source was
at significantly greater distances during
times of full-power source operation
when compared to silence, while Stone
(2015a) and Stone and Tasker (2006)
reported that behavioral responses,
including avoidance and changes in
swimming or surfacing behavior, were
evident for dolphins during firing of
large arrays. Goold and Fish (1998)
described a ‘‘general pattern of localized
disturbance’’ for dolphins in the vicinity
of an airgun survey. However, while
these general findings—typically,
dolphins will display increased distance
from the acoustic source, decreased
prevalence of ‘‘bow-riding’’ activities,
and increases in surface-active
behaviors—are indicative of adverse or
aversive responses that may rise to the
level of ‘‘take’’ (as defined by the
MMPA), they are not indicative of any
response of a severity such that the need
to avoid it outweighs the impact on
practicability for the industry and
operators.
Additionally, increased shutdowns
resulting from such a measure would
require source vessels to revisit the
missed track line to reacquire data,
resulting in an overall increase in the
total sound energy input to the marine
environment and an increase in the total
duration over which the survey is active
in a given area. Therefore, the removal
of such measures for small delphinids is
warranted in consideration of the
available information regarding the
effectiveness of such measures in
mitigating impacts to small delphinids
and the practicability of such measures.
Although other mid-frequency
hearing specialists (e.g., large
delphinids) are considered no more
likely to incur auditory injury than are
small delphinids, they are more
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typically deep divers, meaning that
there is some increased potential for
more severe effects from a behavioral
reaction, as discussed in greater detail
in Comments and Responses. Therefore,
NMFS anticipates benefit from a
shutdown requirement for large
delphinids, in that it is likely to
preclude more severe behavioral
reactions for any such animals in close
proximity to the source vessel as well as
any potential for physiological effects.
At the same time, large delphinids are
much less likely to approach vessels.
Therefore, a shutdown requirement for
large delphinids would not have similar
impacts as a small delphinid shutdown
in terms of either practicability for the
applicant or corollary increase in sound
energy output and time on the water.
Other Surveys—Shutdown protocols
for shallow penetration surveys are
similar to those described for deep
penetration surveys, except that the
exclusion zone is defined as a 100-m
radial distance around the perimeter of
the acoustic source. The dolphin
exception described above for deep
penetration surveys would apply. As
described previously, no shutdowns
would be required for HRG surveys.
Extended Shutdown Requirements for
Special Circumstances—Shutdown of
the acoustic source is also required in
the event of certain other detections
beyond the standard exclusion zones. In
the proposed regulatory text, NMFS
conditioned these shutdowns upon
detection of the relevant species or
circumstances at any distance. However,
in the preamble to the proposed
regulations, we also included an
alternative proposal for public review
and comment in which shutdown of the
acoustic source would occur in the
circumstances listed below, but only
within 1 km of the source (for deep
penetration surveys). We requested
comment on both proposals and other
variations of those proposals, including
NMFS’ interpretation of the data and
any other data that support the
necessary findings regarding initiating
shutdown for certain circumstances at
any distance or within 1 km. Following
review of public comments and the
relevant scientific information, NMFS
determined that it is appropriate to limit
such shutdown requirements. However,
as discussed in the next paragraph, we
also determined that the relevant
scientific information better supports
1.5 km as a reasonable detection radius
(versus 1 km). Placement of a distance
limit on these requirements maintains
the intent of the measures as originally
proposed, i.e., to provide for additional
real-time protection by limiting the
intensity and duration of acoustic
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exposures for certain species or in
certain circumstances, while reducing
the area over which PSOs must
maintain observational effort. As for
normal shutdowns within the standard
exclusion zone, shutdowns at extended
distance should be made on the basis of
confirmed detections (visual or
acoustic) within the zone.
For deep penetration surveys, NMFS
determined an appropriate distance on
the basis of available information
regarding detection functions for
relevant species, but notes that, while
based on quantitative data, the distance
is an approximate limit that is merely
intended to encompass the region
within which we would expect a
relatively high degree of success in
sighting certain species while also
improving PSO efficacy by removing the
potential that a PSO might interpret
these requirements as demanding a
focus on areas further from the vessel.
The appropriate distance limit may vary
for different regions, depending on the
species to which it may apply. For each
modeled taxon, Roberts et al. (2016)
fitted detection functions that modeled
the detectability of the taxon according
to distance from the trackline and other
covariates (i.e., the probability of
detecting an animal given its distance
from the transect). These functions were
based on nearly 1.1 million linear km of
line-transect survey effort conducted
from 1992–2014, with surveys arranged
in aerial and shipboard hierarchies and
further grouped according to similarity
of observation protocol and platform.
Where a taxon was sighted infrequently,
a detection function was fit to pooled
sightings of suitable proxy species. For
example, for the Bryde’s whale and
shipboard binocular surveys (i.e., the
relevant combination of platform and
protocol), a detection function was fit
using pooled sightings of Bryde’s
whales and other mysticete species
(Roberts et al., 2015c). The resulting
detection function shows a slightly
more than 20 percent probability of
detecting whales at 2 km, with a mean
effective strip half-width (ESHW)
(which provides a measure of how far
animals are seen from the transect line;
Buckland et al., 2001) of 1,309 m
(Roberts et al., 2015c). Similarly, Barlow
et al. (2011) reported mean ESHWs for
various mysticete species ranging from
approximately 1.5–2 km. The detection
function used in modeling density for
beaked whales provided mean ESHWs
of 1,462 m and 2,258 m for two NOAA
vessels on which visual surveys have
historically been conducted (Roberts et
al., 2015b). Therefore, NMFS set the
shutdown radius for special
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circumstances (described below) at 1.5
km for deep penetration surveys. The
shutdown radius for special
circumstances is set at 500 m for
shallow penetration surveys.
Comments disagreeing with the
proposal to require shutdowns upon
certain detections at any distance also
suggested that the measures did not
have commensurate benefit for the
relevant species. However, it must be
noted that any such observations would
still be within range of where behavioral
disturbance of some form and degree
would be likely to occur. While visual
PSOs should focus observational effort
within the vicinity of the acoustic
source and vessel, this does not
preclude them from periodic scanning
of the remainder of the visible area or
from noting observations at greater
distances, and there is no reason to
believe that such periodic scans by
professional PSOs would hamper the
ability to maintain observation of areas
closer to the source and vessel.
Circumstances justifying shutdown at
extended distance (e.g., within 1.5 km)
include:
• Upon detection of a Bryde’s whale.
On the basis of the findings of NMFS’
status review (Rosel et al., 2016), NMFS
has listed the GOM Bryde’s whale as an
endangered species pursuant to the ESA
(April 15, 2019; 84 FR 15446). These
whales form a small and resident
population in the northeastern GOM,
with a highly restricted geographic
range and a very small population
abundance (fewer than 100)—recently
determined by a status review team to
be ‘‘at or below the near-extinction
population level’’ (Rosel et al., 2016).
The review team stated that, aside from
the restricted distribution and small
population, the whales face a significant
suite of anthropogenic threats, one of
which is noise produced by geophysical
surveys. NMFS believes it appropriate
to eliminate potential effects to
individual Bryde’s whales to the extent
practicable. There may be rare sightings
of vagrant baleen whales of other
species in the GOM, and the PSO may
order a shutdown when observed in the
applicable exclusion zone.
• Upon detection of a sperm whale.
NMFS provided an expanded
discussion of the available evidence that
supports this measure in the notice of
proposed rulemaking. In summary, the
sperm whale’s primary means of
locating prey is echolocation (Miller et
al., 2004), and multiple studies have
shown that noise can disrupt feeding
behavior and/or significantly reduce
foraging success for sperm whales at
relatively low levels of exposure (e.g.,
Miller et al., 2009, 2012; Isojunno et al.,
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2016; Sivle et al., 2012; Cure et al.,
2016). Effects on energy intake with no
immediate compensation, as is
suggested by disruption of foraging
behavior without corollary movements
to new locations, would be expected to
result in bioenergetics consequences to
individual whales. Farmer et al. (2018a)
developed a stochastic life-stage
structured bioenergetic model to
evaluate the consequences of reduced
foraging efficiency in sperm whales,
finding that individual resilience to
foraging disruptions is primarily a
function of size (i.e., reserve capacity)
and daily energetic demands, and that
the ultimate effects on reproductive
success and individual fitness are
largely dependent on the duration and
frequency of disturbance. The
bioenergetic simulations of Farmer et al.
(2018a) show that frequent disruptions
in foraging, as might be expected when
large amounts of survey activity overlap
with areas of importance for sperm
whales, can have potentially severe
fitness consequences. In addition, the
GOM sperm whale population was
heavily impacted by the DWH oil spill.
Therefore, in consideration of the
potential energetic impacts of survey
activity on individual sperm whales and
the environmental baseline for the GOM
sperm whale population, NMFS
determined that meaningful measures
must be taken to minimize disruption of
foraging behavior. As described earlier
in this section, the proposed regulations
limited this extended distance
shutdown requirement to acoustic
detections of sperm whales. However,
while stating that NMFS preliminarily
did not believe the addition of
shutdowns for sperm whales based on
visual detections at any distance were
warranted, we also requested any
information from the public that would
be relevant to that determination.
NMFS’ review of the comments and
information provided by the public
indicates that expansion of this
requirement to include all sperm whale
detections, rather than only acoustic
detections (as was proposed), is
warranted. Please see Comments and
Responses for further discussion.
• Upon detection of a beaked whale
or Kogia spp. These species are
behaviorally sensitive deep divers and it
is possible that disturbance could
provoke a severe behavioral response
leading to fitness consequences (e.g.,
Wursig et al., 1998; Cox et al., 2006).
NMFS recognizes that there are
generally low detection probabilities for
beaked whales and Kogia spp., meaning
that many animals of these species may
go undetected. Barlow (1999) estimates
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such probabilities at 0.23 to 0.45 for
Cuvier’s and Mesoplodont beaked
whales, respectively. However, Barlow
and Gisiner (2006) predict a roughly 24–
48 percent reduction in the probability
of detecting beaked whales during
seismic mitigation monitoring efforts as
compared with typical research survey
efforts, and Moore and Barlow (2013)
noted a decrease in g(0) for Cuvier’s
beaked whales from 0.23 at BSS 0 (calm)
to 0.024 at BSS 5. Similar detection
probabilities have been noted for Kogia
spp., though they typically travel in
smaller groups and are less vocal, thus
making detection more difficult (Barlow
and Forney, 2007). As discussed
previously in this document (see the
Estimated Take section), there are high
levels of predicted exposures for beaked
whales in particular. Because it is likely
that only a small proportion of beaked
whales and Kogia spp. potentially
affected by the proposed surveys would
actually be detected, it is important to
avoid potential impacts when
practicable. Additionally for Kogia
spp.—the one species of high-frequency
cetacean likely to be encountered—
auditory injury zones relative to peak
pressure thresholds are significantly
greater than for other cetaceans—
approximately 500 m from the acoustic
source, depending on the specific real
world array characteristics (NMFS,
2018).
Shutdown Implementation
Protocols—Any PSO on duty has the
authority to delay the start of survey
operations or to call for shutdown of the
acoustic source. When shutdown is
called for by a PSO, the acoustic source
must be immediately deactivated and
any dispute resolved only following
deactivation. The operator must
establish and maintain clear lines of
communication directly between PSOs
on duty and crew controlling the
acoustic source to ensure that shutdown
commands are conveyed swiftly while
allowing PSOs to maintain watch; handheld UHF radios are recommended.
When both visual PSOs and PAM
operators are on duty, all detections
must be immediately communicated to
the remainder of the on-duty team for
potential verification of visual
observations by the PAM operator or of
acoustic detections by visual PSOs and
initiation of dialogue as necessary.
When there is certainty regarding the
need for mitigation action on the basis
of either visual or acoustic detection
alone, the relevant PSO(s) must call for
such action immediately.
Upon implementation of shutdown,
the source may be reactivated after the
animal(s) has been observed exiting the
exclusion zone or following a 30-minute
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clearance period with no further
detection of the animal(s).
If the acoustic source is shut down for
reasons other than mitigation (e.g.,
mechanical difficulty) for brief periods
(i.e., less than 30 minutes), it may be
activated again without ramp-up if PSOs
have maintained constant observation
(including acoustic observation, where
required) and no visual detections of
any marine mammal have occurred
within the exclusion zone and no
acoustic detections have occurred
(when required). NMFS defines ‘‘brief
periods’’ in keeping with other
clearance watch periods and to avoid
unnecessary complexity in protocols for
PSOs. For any longer shutdown (e.g.,
during line turns), pre-clearance watch
and ramp-up are required. For any
shutdown at night or in periods of poor
visibility (e.g., BSS 4 or greater), rampup is required but if the shutdown
period was brief and constant
observation maintained, pre-clearance
watch is not required.
Miscellaneous Protocols
The acoustic source must be
deactivated when not acquiring data or
preparing to acquire data, except as
necessary for testing. Unnecessary use
of the acoustic source should be
avoided. Firing of the acoustic source at
any volume above the stated production
volume would not be authorized. The
operator must provide information to
the lead PSO at regular intervals
confirming the firing volume. Notified
operational capacity (not including
redundant backup airguns) must not be
exceeded during the survey, except
where unavoidable for source testing
and calibration purposes. All occasions
where activated source volume exceeds
notified operational capacity must be
noticed to the PSO(s) on duty and fully
documented for reporting. The lead PSO
must be granted access to relevant
instrumentation documenting acoustic
source power and/or operational
volume.
Testing of the acoustic source
involving all elements requires normal
mitigation protocols (e.g., ramp-up).
Testing limited to individual source
elements or strings does not require
ramp-up but does require pre-clearance.
Restriction Areas
Discussion of various time-area
restrictions was provided in the notice
of proposed rulemaking. NMFS
proposed two time-area restrictions
located within the area covered by the
current GOMESA moratorium. As
discussed previously, BOEM
subsequently updated the scope of the
specified activity that was the subject of
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the petition for the ITR, removing the
area subject to the current GOMESA
moratorium from consideration through
this rule. Therefore, consideration of
those two proposed restrictions (Areas
2–3 in Figure 4 below), and any
alternatives, is no longer relevant.
Figure 4 depicts the time-area
restrictions, absent consideration of
BOEM’s removal of the GOMESA
moratorium area. Areas 2 and 3 are
entirely within that area, and the eastern
BILLING CODE 3510–22–C
to the northern coastal stock of
bottlenose dolphins during the time
period believed to be of greatest
importance as a reproductive period. As
described previously, NOAA estimates
that potentially 82 percent of northern
coastal dolphins were exposed to DWH
oil, resulting in an array of long-term
health impacts (including reproductive
failure) and possible population
reductions of 50 percent for the stock
(DWH MMIQT, 2015). The same
analysis estimated that these
population-level impacts could require
39 years to recovery, in the absence of
other additional stressors. More
recently, the stock has been subject to
another declared UME; further
discussion of this UME is provided
under Description of Marine Mammals
in the Area of the Specified Activity.
The January–May timeframe is
intended to best encompass the most
important reproductive period for
bottlenose dolphins in these coastal
waters, when additional stress is most
Coastal Restriction—No airgun
surveys may occur from 90–84° W (as
truncated through removal of the
GOMESA moratorium area) and
shoreward of a line indicated by the
20-m isobath, during the months of
January through May (Area 1; Figure 4).
Waters shoreward of the
20-m isobath, where coastal dolphin
stocks occur, represent the areas of
greatest abundance for bottlenose
dolphins (Roberts et al., 2016). As
discussed above, and in greater detail in
Comments and Responses, this
requirement was modified from the
proposed regulations by contracting the
area spatially while expanding the
restriction temporally by one month, in
order to more practicably minimize
potential impacts on the potentially
affected stock most heavily impacted by
the DWH oil spill (i.e., the northern
coastal stock of bottlenose dolphins).
The restriction is intended
specifically to avoid additional stressors
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extent of Area 1 is functionally reduced
through the removal of the GOMESA
moratorium area.
BILLING CODE 3510–22–P
likely to have serious impacts on
pregnancy and/or survival of neonates.
Expert interpretation of the long-term
data for neonate strandings is that
February–April are the primary months
that animals are born in the northern
GOM, and that fewer but similar
numbers are born in January and May.
This refers to long-term averages and in
any particular year the peak
reproductive period can shift earlier or
later.
Bryde’s Whale—The ‘‘Bryde’s whale
core habitat area’’ considered in the
notice of proposed rulemaking was
designated as between the 100- and
400-m isobaths, from 87.5° W to 27.5° N
(Area 2; Figure 4). As summarized at the
beginning of this section, and discussed
in greater detail in Comments and
Responses, the proposed regulatory text
included a seasonal restriction within
the same area. The preamble to the
proposed regulations also included
alternative proposals for public review
and comment. This area is entirely
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located in the GOMESA moratorium
area, which is now removed from
consideration through this rule.
As described previously, NOAA’s
status review team determined the
status of the GOM Bryde’s whale to be
precarious (Rosel et al., 2016). These
findings formed, in part, the basis for
the analysis presented in the preamble
to the proposed regulations and
subsequently supported NMFS’ listing
of the GOM Bryde’s whale as an
endangered species pursuant to the ESA
(84 FR 15446; April 15, 2019). These
whales form a small and resident
population in the northeastern GOM,
with a highly restricted geographic
range and a very small population
abundance—determined by the status
review team to be ‘‘at or below the nearextinction population level’’ (Rosel et
al., 2016). Aside from the restricted
distribution and small population, the
whales face a significant suite of
anthropogenic threats, one of which is
noise produced by airgun surveys.
While various population abundance
estimates are available (e.g., Waring et
al., 2016; Roberts et al., 2016; Dias and
Garrison, 2016), the population
abundance was almost certainly less
than 100 prior to the DWH oil spill.
NOAA estimated that, as a result of that
event, 48 percent of the population may
have been exposed to DWH oil, with 17
percent killed and 22 percent of females
experiencing reproductive failure. The
best estimate for maximum population
reduction was 22 percent, with an
estimated 69 years to recovery (to the
precarious status prior to the DWH oil
spill) (DWH MMIQT, 2015). It is
considered likely that Bryde’s whale
habitat previously extended to shelf and
slope areas of the western and central
GOM similar to where they are found
now in the eastern GOM, and that
anthropogenic activity—largely energy
exploration and production—
concentrated in those areas could have
resulted in habitat abandonment
(Reeves et al., 2011; Rosel and Wilcox,
2014). Further, the population exhibits
very low levels of genetic diversity and
significant genetic mitochondrial DNA
divergence from other Bryde’s whales
worldwide (Rosel and Wilcox, 2014).
The small population size, restricted
range, and low genetic diversity alone
place these whales at significant risk of
extinction (IWC, 2017), which has been
exacerbated by the effects of the DWH
oil spill. Additionally, Bryde’s whale
dive and foraging behavior places them
at heightened risk of being struck by
vessels and/or entangled in fishing gear
(Soldevilla et al., 2017). NMFS
considered a restriction in this core
habitat area to protect Bryde’s whales
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because of their hearing sensitivity in
the lower frequency range (which makes
them generally more susceptible to
incurring effects from airgun noise than
other taxa in the GOM); the potential
impacts to important behavioral
functions such as feeding, breeding, and
raising young; their dangerously low
population size; and other issues
discussed previously. The absence of
survey activity in the area would be
expected to protect Bryde’s whales and
their habitat through the alleviation or
minimization of a range of airgun
effects, both acute and chronic, that
could otherwise accrue to impact the
reproduction or survival of individuals
in the core habitat area. The absence of
survey activity in the area would not
only largely avoid Level B harassment of
Bryde’s whales, but also very
importantly minimize other acoustic
effects such as masking and loss of
communication space. Based on Roberts
et al., 2016, this core habitat area is
expected to encompass approximately
92 percent of Bryde’s whales in the Gulf
of Mexico. The update of the scope of
the rule eliminates this core area and
the corresponding impacts of concern
from consideration in the analysis.
Although this area is no longer
relevant under the updated geographic
scope of the specified activity and this
rule, the discussion above is still
important to provide a picture of the
species’ distribution in the GOM and
NMFS’ work to identify appropriate
mitigation in this rulemaking. Because
NMFS acknowledges that some whales
may be present at locations other than
within this core habitat area, we
considered additional information in
order to evaluate whether a different
closure area may be warranted. For
example, a NOAA survey reported
observation of a Bryde’s whale in the
western GOM in 2017 (NMFS, 2018).
There had not previously been a verified
sighting of a Bryde’s whale in the
western GOM and, given the importance
of this observation, additional survey
effort was conducted in an attempt to
increase effort in the area. However, no
additional sightings were recorded.
Overall, Bryde’s whales observations
have been consistently located within
the eastern GOM core habitat area, with
few whales sighted elsewhere despite a
large amount of dedicated cetacean
survey effort that covered both
continental shelf and oceanic waters.
Whales have been sighted in the core
habitat area in all seasons, and all
indications are that the whales inhabit
this area year-round as a resident
population. A tagged whale remained
within the area for 38 days, the entire
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time the tag was active. Therefore, while
it is possible that Bryde’s whales occur
outside the core habitat area, or that
whales from the eastern GOM
occasionally travel outside the area, the
few existing observations outside the
eastern GOM do not affect NMFS’
determination that the area considered
in the proposed rule represents core
habitat, or identify any additional
important habitat that may
appropriately be subject to a restriction
on survey activity.
Entanglement Avoidance
The use of ocean-bottom nodes (OBN)
or similar equipment requiring the use
of tethers or connecting lines poses an
entanglement risk. In order to avoid
incidents of entanglement, NMFS
requires the same measures included for
the same purpose in permits issued by
BOEM. These measures apply to
operators conducting OBN surveys (or
surveys using similar equipment), and
include: (1) Use negatively buoyant
coated wire-core tether cable (e.g., 3⁄4’’
polyurethane-coated cable with 1⁄2’’
wire core); (2) retrieve all lines
immediately following completion of
the survey; and (3) attach acoustic
pingers directly to the coated tether
cable. Acoustic releases should not be
used. No unnecessary release lines or
lanyards may be used and nylon rope
may not be used for any component of
the system. Pingers must be attached
directly to the nodal tether cable via
shackle, with cables retrieved via
grapnel. If a lanyard is required it must
be as short as possible and made as stiff
as possible, e.g., by placing inside a
hose sleeve. The notice of proposed
rulemaking also included a proposed
requirement to require operators to
employ a third-party PSO aboard the
node retrieval vessel in order to
document any unexpected marine
mammal entanglement. In consideration
of the information provided by public
commenters, NMFS has determined that
this measure is unnecessary and
eliminates it from the final ITR. Use of
a third-party PSO in this capacity would
not help to avoid entanglement events,
and operators would be required to
report any such events to BSEE.
Therefore, the requirement provides
little benefit while imposing costs on
operators.
Vessel Strike Avoidance
These measures apply to all vessels
associated with any survey activity (e.g.,
source vessels, streamer vessels, chase
vessels, supply vessels). However,
NMFS notes that these requirements do
not apply in any case where compliance
would create an imminent and serious
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threat to a person or vessel or to the
extent that a vessel is restricted in its
ability to maneuver and, because of the
restriction, cannot comply. These
measures include the following:
1. Vessel operators and crews must
maintain a vigilant watch for all marine
mammals and must slow down, stop
their vessel, or alter course, as
appropriate and regardless of vessel
size, to avoid striking any marine
mammal. A visual observer aboard the
vessel must monitor a vessel strike
avoidance zone around the vessel
(distances stated below). Visual
observers monitoring the vessel strike
avoidance zone may be third-party
observers (i.e., PSOs) or crew members,
but crew members responsible for these
duties must be provided sufficient
training to (1) distinguish protected
species from other phenomena and (2)
broadly to identify a marine mammal as
a baleen whale, sperm whale, or other
marine mammal;
2. Vessel speeds must be reduced to
10 kn or less when mother/calf pairs,
pods, or large assemblages of any
marine mammal are observed near a
vessel;
3. All vessels must maintain a
minimum separation distance of 500 m
from baleen whales;
4. All vessels must maintain a
minimum separation distance of 100 m
from sperm whales;
5. All vessels must, to the maximum
extent practicable, attempt to maintain a
minimum separation distance of 50 m
from all other marine mammals, with an
understanding that at times this may not
be possible (e.g., for animals that
approach the vessel); and
6. When marine mammals are sighted
while a vessel is underway, the vessel
shall take action as necessary to avoid
violating the relevant separation
distance (e.g., attempt to remain parallel
to the animal’s course, avoid excessive
speed or abrupt changes in direction
until the animal has left the area). If
marine mammals are sighted within the
relevant separation distance, the vessel
must reduce speed and shift the engine
to neutral, not engaging the engines
until animals are clear of the area. This
does not apply to any vessel towing gear
or any vessel that is navigationally
constrained.
NMFS has carefully evaluated the
suite of mitigation measures described
here and considered a range of other
measures in the context of ensuring that
we prescribe the means of effecting the
least practicable adverse impact on the
affected marine mammal species and
stocks and their habitat. Based on our
evaluation of these measures, we have
determined that the required mitigation
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measures provide the means of effecting
the least practicable adverse impact on
marine mammal species or stocks and
their habitat, paying particular attention
to rookeries, mating grounds, and areas
of similar significance.
Monitoring and Reporting
In order to issue an LOA for an
activity, Section 101(a)(5)(A) of the
MMPA states that NMFS must set forth
requirements pertaining to the
monitoring and reporting of the
authorized taking. NMFS’ MMPA
implementing regulations further
describe the information that an
applicant should provide when
requesting an authorization (50 CFR
216.104(a)(13)), including the means of
accomplishing the necessary monitoring
and reporting that will result in
increased knowledge of the species and
the level of taking or impacts on
populations of marine mammals.
Effective reporting is critical both to
compliance as well as ensuring that the
most value is obtained from the required
monitoring.
Section 101(a)(5)(A) allows that
incidental taking may be authorized
only if the total of such taking
contemplated over the course of five
years will have a negligible impact on
affected species or stocks (a finding
based on impacts to annual rates of
recruitment and survival) and, further,
section 101(a)(5)(B) requires that
authorizations issued pursuant to
101(a)(5)(A) be withdrawn or suspended
if the total taking is having, or may
have, more than a negligible impact (or
such information may inform decisions
on requests for LOAs under the specific
regulations). Therefore, the necessary
requirements pertaining to monitoring
and reporting must address the total
annual impacts to marine mammal
species or stocks. Effective reporting is
critical both to compliance as well as
ensuring that the most value is obtained
from the required monitoring.
These requirements are described
below under ‘‘Data Collection’’ and
‘‘LOA Reporting.’’ Additional
comprehensive reporting, across LOAholders on an annual basis, is also
required and is described below under
‘‘Comprehensive Reporting.’’
More specifically, monitoring and
reporting requirements prescribed by
NMFS should contribute to improved
understanding of one or more of the
following:
• Occurrence of marine mammal
species in action area (e.g., presence,
abundance, distribution, density);
• Nature, scope, or context of likely
marine mammal exposure to potential
stressors/impacts (individual or
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cumulative, acute or chronic), through
better understanding of: (1) Action or
environment (e.g., source
characterization, propagation, ambient
noise); (2) affected species (e.g., life
history, dive patterns); (3) co-occurrence
of marine mammal species with the
action; or (4) biological or behavioral
context of exposure (e.g., age, calving or
feeding areas);
• Individual marine mammal
responses (behavioral or physiological)
to acoustic stressors (acute, chronic, or
cumulative), other stressors, or
cumulative impacts from multiple
stressors;
• How anticipated responses to
stressors impact either: (1) Long-term
fitness and survival of individual
marine mammals; or (2) populations,
species, or stocks;
• Effects on marine mammal habitat
(e.g., marine mammal prey species,
acoustic habitat, or important physical
components of marine mammal habitat);
and
• Mitigation and monitoring
effectiveness.
Changes To Monitoring and Reporting
From the Notice of Proposed
Rulemaking
Here we summarize substantive
changes to monitoring and reporting
requirements from the notice of
proposed rulemaking. All changes were
made on the basis of review of public
comments received and/or review of
new information.
• Although NMFS recognizes the
importance of producing the most
accurate estimates of actual take
possible, we agree that the specific
approach described in the proposed rule
for correcting observations to produce
estimates of actual takes is novel in that
it has not been previously required of
applicants conducting similar activities
and, therefore, its appropriateness for
application to observations conducted
from working source vessels (versus
research vessels) is unknown. As
suggested through public comment,
NMFS will continue to evaluate the best
method for producing accurate
estimates of actual take, based on
marine mammal detections, through the
adaptive management process,
including consideration of the Marine
Mammal Commission-recommended
method included in the proposed
regulations.
• NMFS has revised requirements
relating to reporting of injured or dead
marine mammals and has added newly
crafted requirements relating to actions
that should be taken in response to
notification of live stranding events in
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certain circumstances, in order to reflect
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PSO Eligibility and Qualifications
All PSO resumes must be submitted
to NMFS and PSOs must be approved
by NMFS after a review of their
qualifications. These qualifications
include whether the individual has
successfully completed the necessary
training (see ‘‘Training,’’ below) and, if
relevant, whether the individual has the
requisite experience (and is in good
standing). PSOs should provide a
current resume and information
indicating successful completion of an
acceptable PSO training course;
submitted resumes should not include
superfluous information. In order for a
PSO training course to be deemed
acceptable by NMFS (in consultation
with BOEM/BSEE), the agencies must,
at minimum, review a course
information packet that includes the
name and qualifications (e.g.,
experience, training, or education) of
the instructor(s), the course outline or
syllabus, and course reference material.
Absent a waiver (discussed below),
PSOs must be trained biologists, with
the following minimum qualifications:
• A bachelor’s degree from an
accredited college or university with a
major in one of the natural sciences and
a minimum of 30 semester hours or
equivalent in the biological sciences and
at least one undergraduate course in
math or statistics; and
• Successful completion of relevant
training (described below), including
completion of all required coursework
and passing (80 percent or greater) a
written and/or oral examination
developed for the training program.
In addition, it is recommended that
PSOs meet the following requirements:
• Experience and ability to conduct
field observations and collect data
according to assigned protocols (may
include academic experience) and
experience with data entry on
computers;
• Visual acuity in both eyes (vision
correction is permissible) sufficient for
discernment of moving targets at the
water’s surface with ability to estimate
target size and distance; use of
binoculars may be necessary to correctly
identify the target (required for visual
PSOs only);
• Experience or training in the field
identification of marine mammals,
including the identification of behaviors
(required for visual PSOs only);
• Sufficient training, orientation, or
experience with the survey operation to
ensure personal safety during
observations;
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• Writing skills sufficient to prepare a
report of observations (e.g., description,
summary, interpretation, analysis)
including but not limited to the number
and species of marine mammals
observed; marine mammal behavior;
and descriptions of activity conducted
and implementation of mitigation; and
• Ability to communicate orally, by
radio or in person, with survey
personnel to provide real-time
information on marine mammals
detected in the area as necessary.
The educational requirements may be
waived if the PSO has acquired the
relevant skills through alternate
experience. Requests for such a waiver
must include written justification, and
prospective PSOs granted waivers must
satisfy training requirements described
below. Alternate experience that may be
considered includes, but is not limited
to, the following:
• Secondary education and/or
experience comparable to PSO duties;
• Previous work experience
conducting academic, commercial, or
government-sponsored marine mammal
surveys; and
• Previous work experience as a PSO;
the PSO should demonstrate good
standing and consistently good
performance of PSO duties.
Training—NMFS does not formally
administer any PSO training program or
endorse specific providers but will
approve PSOs that have successfully
completed courses that meet the
curriculum and trainer requirements
specified herein and, therefore, are
deemed acceptable. To be deemed
acceptable, training should adhere
generally to the recommendations
provided by ‘‘National Standards for a
Protected Species Observer and Data
Management Program: A Model Using
Geological and Geophysical Surveys’’
(Baker et al., 2013). Those
recommendations include the following
topics for training programs:
• Life at sea, duties, and authorities;
• Ethics, conflicts of interest,
standards of conduct, and data
confidentiality;
• Offshore survival and safety
training;
• Overview of oil and gas activities
(including geophysical data acquisition
operations, theory, and principles) and
types of relevant sound source
technology and equipment;
• Overview of the MMPA and ESA as
they relate to protection of marine
mammals;
• Mitigation, monitoring, and
reporting requirements as they pertain
to geophysical surveys;
• Marine mammal identification,
biology and behavior;
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• Background on underwater sound;
• Visual surveying protocols, distance
calculations and determination, cues,
and search methods for locating and
tracking different marine mammal
species (visual PSOs only);
• Optimized deployment and
configuration of PAM equipment to
ensure effective detections of cetaceans
for mitigation purposes (PAM operators
only);
• Detection and identification of
vocalizing species or cetacean groups
(PAM operators only);
• Measuring distance and bearing of
vocalizing cetaceans while accounting
for vessel movement (PAM operators
only);
• Data recording and protocols,
including standard forms and reports,
determining range, distance, direction,
and bearing of marine mammals and
vessels; recording GPS location
coordinates, weather conditions,
Beaufort wind force and sea state, etc.;
• Proficiency with relevant software
tools;
• Field communication/support with
appropriate personnel, and using
communication devices (e.g., two-way
radios, satellite phones, internet, email,
facsimile);
• Reporting of violations,
noncompliance, and coercion; and
• Conflict resolution.
PAM operators should regularly
refresh their detection skills through
practice with simulation-modeling
software and should keep up to date
with training on the latest software/
hardware advances.
Visual Monitoring
The lead PSO is responsible for
establishing and maintaining clear lines
of communication with vessel crew. The
vessel operator shall work with the lead
PSO to accomplish this and shall ensure
any necessary briefings are provided for
vessel crew to understand mitigation
requirements and protocols. While on
duty, PSOs will continually scan the
water surface in all directions around
the acoustic source and vessel for
presence of marine mammals, using a
combination of the naked eye and highquality binoculars, from optimum
vantage points for unimpaired visual
observations with minimum
distractions. PSOs will collect
observational data for all marine
mammals observed, regardless of
distance from the vessel, including
species, group size, presence of calves,
distance from vessel and direction of
travel, and any observed behavior
(including an assessment of behavioral
responses to survey activity). Upon
observation of marine mammal(s), a
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PSO will record the observation and
monitor the animal’s position (including
latitude/longitude of the vessel and
relative bearing and estimated distance
to the animal) until the animal dives or
moves out of visual range of the
observer, and a PSO will continue to
observe the area to watch for the animal
to resurface or for additional animals
that may surface in the area. PSOs will
also record environmental conditions at
the beginning and end of the
observation period and at the time of
any observations, as well as whenever
conditions change significantly in the
judgment of the PSO on duty.
For all deep penetration surveys, the
vessel operator must provide bigeye
binoculars of appropriate quality (e.g.,
25 x 150; 2.7 view angle; individual
ocular focus; height control) solely for
PSO use. These should be pedestalmounted on the deck at the most
appropriate vantage point that provides
for optimal sea surface observation, PSO
safety, and safe operation of the vessel.
Other required equipment, which
should be made available to PSOs by the
third-party observer provider, includes
reticle binoculars of appropriate quality
(e.g., 7 x 50), GPS, digital camera with
a telephoto lens (the camera or lens
should also have an image stabilization
system) that is at least 300 mm or
equivalent on a full-frame single-lens
reflex, compass, and any other tools
necessary to adequately perform the
tasks described above, including
accurate determination of distance and
bearing to observed marine mammals.
Individuals implementing the
monitoring protocol will assess its
effectiveness using an adaptive
approach. Monitoring biologists will use
their best professional judgment
throughout implementation and seek
improvements to these methods when
deemed appropriate. Specifically,
implementation of shutdown
requirements will be made on the basis
of the PSO’s best professional judgment.
While PSOs should not insert undue
precaution into decision-making, it is
expected that PSOs may call for
mitigation action on the basis of
reasonable certainty regarding the need
for such action, as informed by
professional judgment. Any
modifications to protocol will be
coordinated between NMFS and the
applicant.
Acoustic Monitoring
Use of towed PAM is required for
deep penetration surveys. Monitoring of
a towed PAM system is required at all
times for these surveys, from 30 minutes
prior to ramp-up, throughout all use of
the acoustic source, and for 60 minutes
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following cessation of survey activity.
Towed PAM systems should consist of
hardware (e.g., hydrophone array,
recorder, cables) and software (e.g., data
processing program and algorithm).
Some type of automated detection
software must be used. Acoustic signals
are processed for output to the PAM
operator with software designed to
detect marine mammal vocalizations.
Current PAM technology has some
limitations (e.g., limited directional
capabilities and detection range,
detection of signals due to vessel and
flow noise, low accuracy in localization)
and there are no formal guidelines
currently in place regarding
specifications for hardware, software, or
operator training requirements.
NMFS’ requirement to use PAM refers
to the use of calibrated hydrophone
arrays with full system redundancy to
detect, identify, and estimate distance
and bearing to vocalizing cetaceans, to
the extent possible. With regard to
calibration, the PAM system should
have at least one calibrated hydrophone,
sufficient for determining whether
background noise levels on the towed
PAM system are sufficiently low to meet
performance expectations. Additionally,
if multiple hydrophone types occur in a
system (i.e., monitor different
bandwidths), then one hydrophone from
each such type shall be calibrated, and
whenever sets of hydrophones (of the
same type) are sufficiently spatially
separated such that they would be
expected to experience ambient noise
environments that differ by 6 dB or
more across any integrated species
cluster bandwidth, then at least one
hydrophone from each set should be
calibrated. In terms of calibrating the
rest of the system, the signal route to the
data recorder and monitoring software
shall be calibrated so that the binary
amplitude data written to hard disk can
be converted into units of acoustic
pressure. The configuration of hardware
should be coupled with appropriate
software to aid monitoring and listening
by a PAM operator skilled in
bioacoustics analysis and computer
system specifications capable of running
appropriate software. GPS data
acquisition is recommended for all PAM
operations. If the PAM plan (see below)
claims an ability to localize, every
localization estimate obtained from a
PAM system must be accompanied by
some estimate of uncertainty and
ambiguity.
In the absence of formal standards
addressing any of these three facets of
PAM technology, all applicants must
provide a PAM plan including
description of the hardware and
software proposed for use prior to
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proceeding with any survey where PAM
is required. Following the survey, a
validation document must be submitted
as part of required reporting (see below).
The purpose of the PAM plan is to
demonstrate that the PAM system being
proposed for use is adequate for
addressing the mitigation goals. The
plan shall include methodology and
documentation requirements for all
stages of the project. As recommended
by Thode et al. (2017), PAM plans
should, at minimum, adequately
address and describe (1) the hardware
and software planned for use, including
a hardware performance diagram
demonstrating that the sensitivity and
dynamic range of the hardware is
appropriate for the operation; (2)
deployment methodology, including
target depth/tow distance; (3)
definitions of expected operational
conditions, used to summarize
background noise statistics; (4)
proposed detection-classificationlocalization methodology, including
anticipated species clusters (using a
cluster definition table), target
minimum detection range for each
cluster, and the proposed localization
method for each cluster; (5) operation
plans, including the background noise
sampling schedule; (6) array design
considerations for noise abatement; and
(7) cluster-specific details regarding
which real-time displays and automated
detectors the operator would monitor.
Where relevant, the plan should address
the potential for PAM deployment on a
receiver vessel or other associated vessel
separate from the acoustic source.
Species clusters—The plan shall list
the species of concern during the
upcoming operation. While some
species may be listed individually for
special attention, in many
circumstances it is expected that for the
purposes of a PAM operation multiple
species can be grouped together in a
‘‘cluster’’ that shares similar acoustic
and behavioral characteristics (e.g.,
sperm whale, beaked whales). The plan
must specify a target minimum
detection (and possibly localization)
range for each species cluster used in
the document. Different ranges can be
defined for different operational
conditions. The PAM system may
exceed this detection range, but shall
always be capable of achieving this
minimum detection range.
Hardware and software
specifications—The plan shall have a
section dedicated to demonstrating that
the PAM hardware is sensitive enough
to detect signals from the species
clusters of concern at the target
minimum detection ranges specified.
The plan should include a hardware
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specification table and hardware
performance diagram. The diagram will
show the sensitivity and bandwidth of
the combined array hardware and
recording system, as well as the
received levels required for a given
species cluster to be detectable at the
target minimum detection range. The
overall goal of the diagram is to visually
demonstrate that the planned PAM
array/recording system would have the
capability of detecting various species
clusters at required target ranges,
provided that background noise levels
are not an issue.
Operational conditions—The
validation document should
demonstrate whether the PAM system
has been compromised by excessive
background noise, whether that noise is
electronic interference, flow, platform,
or environmental noise. Therefore, the
plan shall define a set of ‘‘operational
conditions’’ under which detection
statistics (background noise profiles)
will be categorized during the project.
Operational conditions consist of three
categories: Platform activity and status,
mitigation (activity) status, and
environmental status.
Operating procedures—The plan shall
describe the level of effort that is
reasonably expected to occur for the
monitoring requirements. For every
species cluster, the plan should detail
which part of the PAM display would
be used for detecting that cluster. For
example, if a scrolling spectrogram
display is being used for a species
cluster, then the spectrogram’s fast
Fourier transform sample size,
frequency bandwidth, and their refresh
rate shall be specified. Similar details
would be provided for other software
tools, such as click detectors and other
automated detectors and classifiers. The
plan shall also provide a screenshot of
the expected monitor display.
In coordination with vessel crew, the
lead PAM operator will be responsible
for deployment, retrieval, and testing
and optimization of the hydrophone
array. While on duty, the PAM operator
must diligently listen to received signals
and/or monitoring display screens in
order to detect vocalizing cetaceans,
except as required to attend to PAM
equipment. The PAM operator must use
appropriate sample analysis and
filtering techniques and must report all
cetacean detections. While not required
prior to development of formal
standards for PAM use, NMFS
recommends that vessel self-noise
assessments be undertaken during
mobilization in order to optimize PAM
array configuration according to the
specific noise characteristics of the
vessel and equipment involved, and to
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refine expectations for distance/bearing
estimations for cetacean species during
the survey. Copies of any vessel selfnoise assessment reports must be
included with the summary trip report.
Data Collection
PSOs must use standardized
electronic data forms. PSOs will record
detailed information about any
implementation of mitigation
requirements, including the distance of
animals to the acoustic source and
description of specific actions that
ensued, the behavior of the animal(s),
any observed changes in behavior before
and after implementation of mitigation,
and if shutdown was implemented, the
length of time before any subsequent
ramp-up of the acoustic source to
resume survey. If required mitigation
was not implemented, PSOs should
submit a description of the
circumstances. NMFS requires that, at a
minimum, the following information be
reported:
• Vessel names (source vessel and
other vessels associated with survey),
vessel size and type, maximum speed
capability of vessel, port of origin, and
call signs;
• PSO names and affiliations;
• Dates of departures and returns to
port with port name;
• Dates and participants of PSO
briefings;
• Dates and times (Greenwich Mean
Time) of survey effort and times
corresponding with PSO effort;
• Vessel location (latitude/longitude)
when survey effort begins and ends and
vessel location at beginning and end of
visual PSO duty shifts;
• Vessel location at 30 second
intervals (if software capability allows)
or 5 minute intervals (if location must
be manually recorded);
• Vessel heading and speed at
beginning and end of visual PSO duty
shifts and upon any line change;
• Environmental conditions while on
visual survey (at beginning and end of
PSO shift and whenever conditions
change significantly), including
Beaufort scale and any other relevant
weather conditions including cloud
cover, fog, sun glare, night, and overall
visibility to the horizon;
• Vessel location when
environmental conditions change
significantly;
• Factors that may have contributed
to impaired observations during each
PSO shift change or as needed as
environmental conditions change (e.g.,
vessel traffic, equipment malfunctions);
• Survey activity information, such as
acoustic source power output while in
operation, number and volume of
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airguns operating in an array, tow depth
of an acoustic source, and any other
notes of significance (i.e., pre-clearance,
ramp-up, shutdown, testing, shooting,
ramp-up completion, end of operations,
streamers, etc.);
• If a marine mammal is sighted, the
following information should be
recorded:
Æ Watch status (sighting made by
PSO on/off effort, opportunistic, crew,
alternate vessel/platform);
Æ PSO who sighted the animal and
PSO location (including height above
water) at time of sighting;
Æ Time of sighting;
Æ Vessel location at time of sighting;
Æ Water depth;
Æ Direction of vessel’s travel
(compass direction);
Æ Direction of animal’s travel relative
to the vessel;
Æ Pace of the animal;
Æ Estimated distance to the animal
(and method of estimating distance) and
its heading relative to vessel at initial
sighting;
Æ Identification of the animal (e.g.,
genus/species, lowest possible
taxonomic level, or unidentified) and
PSO confidence in identification; also
note the composition of the group if
there is a mix of species;
Æ Estimated number of animals (high/
low/best);
Æ Estimated number of animals by
cohort (adults, yearlings, juveniles,
calves, group composition, etc.);
Æ Description (as many
distinguishing features as possible of
each individual seen, including length,
shape, color, pattern, scars or markings,
shape and size of dorsal fin, shape of
head, and blow characteristics);
Æ Detailed behavior observations
(e.g., number of blows, number of
surfaces, breaching, spyhopping, diving,
feeding, traveling; as explicit and
detailed as possible; note any observed
changes in behavior);
Æ Animal’s closest point of approach
(CPA) and/or closest distance from the
acoustic source;
Æ Platform activity at time of sighting
(e.g., deploying, recovering, testing,
shooting, data acquisition, other); and
Æ Description of any actions
implemented in response to the sighting
(e.g., delays, shutdown, ramp-up); time
and location of the action should also be
recorded;
• If a marine mammal is detected
while using the PAM system, the
following information should be
recorded:
Æ An acoustic encounter
identification number, and whether the
detection was linked with a visual
sighting;
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Æ Time when first and last heard;
Æ Types and nature of sounds heard
(e.g., clicks, whistles, creaks, burst
pulses, continuous, sporadic, strength of
signal, etc.); and
Æ Any additional information
recorded such as water depth of the
hydrophone array, bearing of the animal
to the vessel (if determinable), species
or taxonomic group (if determinable),
spectrogram screenshot, and any other
notable information.
LOA Reporting
PSO effort, survey details, and
sightings data should be recorded
continuously during surveys. Reports
must include all information described
above under ‘‘Data Collection,’’
including amount and location of linekms surveyed and all marine mammal
observations with closest approach
distance. Reports must be submitted to
NMFS within 90 days of survey
completion or following expiration of an
issued LOA. In the event that an LOA
is issued for a period exceeding one
year, annual reports must be submitted
during the period of validity. The draft
report must be accompanied by a
certification from lead PSOs as to the
accuracy of the report. A final report
must be submitted within 30 days
following resolution of any comments
on the draft report.
The report must describe the
operations conducted and sightings of
marine mammals near the operations;
provide full documentation of methods,
results, and interpretation pertaining to
all monitoring; summarize the dates and
locations of survey operations, and all
marine mammal sightings (dates, times,
locations, activities, associated survey
activities); and provide information
regarding locations where the acoustic
source was used. The LOA-holder shall
provide geo-referenced time-stamped
vessel tracklines for all time periods in
which airguns (full array or single) were
operating. Tracklines should include
points recording any change in airgun
status (e.g., when the airguns began
operating, when they were turned off).
GIS files shall be provided in ESRI
shapefile format and include the UTC
date and time, latitude in decimal
degrees, and longitude in decimal
degrees. All coordinates should be
referenced to the WGS84 geographic
coordinate system. In addition to the
report, all raw observational data shall
be made available to NMFS.
This report must also include a
validation document concerning the use
of PAM (if PAM was required), which
should include necessary noise
validation diagrams (NVD) and
demonstrate whether background noise
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levels on the PAM deployment limited
achievement of the planned detection
goals. A separate diagram shall be
produced for every background noise
percentile chosen for analysis.
Background noise percentiles, rather
than a simple average of the data, are
required because the highly nonstationary characteristics of many
background noise profiles cannot be
described by a simple mean. For
example, data collected during a seismic
survey will have short periods of time
containing high-intensity pulses and
longer periods of time dominated by
lower levels of reverberation. Taking a
simple mean of these noise data would
imply background noise levels
substantially higher than what may
actually have been present between
seismic pulses. A validation report
would typically contain between three
to five diagrams, depending on the
number of percentiles analyzed. At a
minimum, the validation report should
contain three diagrams that include the
50th percentile (median), 5th percentile,
and 95th percentile. The 25th percentile
and 75th percentile may also be
included. In each percentile diagram, a
separate background noise curve shall
be drawn for each defined operational
condition. In general, the NVD should
be generated from the data stream that
is used for detecting the presence of
marine mammal signals. For example, if
beamforming or some other form of
array gain has been applied before
invoking signal detection, then the NVD
should be generated using the
beamformed data, and not
omnidirectional data. The complete set
of NVDs, one for each percentile of
interest, combined with a table that lists
the fraction of time the activity was in
each operational state, provides a means
of reviewing the background noiselimitations encountered by the PAM
system during various operational
conditions. Actual marine mammal
detections should be plotted on this
diagram for a reasonableness check on
the expected received levels. Overall,
the validation document should
reiterate all the goals and parameters
stated in the planning document and
verify that goals were/were not met,
why, changes, etc. Also, the validation
document should state whether the
planning was suited to the needs of the
survey and met the required mitigation
standards.
There are multiple reasons why
marine mammals may be present and
yet be undetected by observers. Animals
are missed because they are underwater
(availability bias) or because they are
available to be seen, but are missed by
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observers (perception and detection
biases) (e.g., Marsh and Sinclair, 1989).
Negative bias on perception or detection
of an available animal may result from
environmental conditions, limitations
inherent to the observation platform, or
observer ability. In this case, we do not
have prior knowledge of any potential
negative bias on detection probability
due to observation platform or observer
ability. Therefore, it may be appropriate
to make observational data corrections
with respect to assumed species-specific
detection probability as evaluated
through consideration of environmental
factors (e.g., f(0)). Appropriate methods
will be considered through the adaptive
management process.
The report must include a post-survey
estimate of the instances of take of each
species utilizing the line miles of survey
actually conducted and the same
methods used to initially predict the
estimated take in the LOA application.
Depending on the length and dates of
the survey, LOA-holders may be
required to segment take estimates into
specific years to support the
administration of the rule.
Comprehensive Reporting
Individual LOA-holders will be
responsible for collecting and
submitting monitoring data to NMFS, as
described above. In addition, on an
annual basis, LOA-holders will also
collectively be responsible for
compilation and analysis of those data
for inclusion in subsequent annual
synthesis reports. Individual LOAholders may collaborate to produce this
report or may elect to have their trade
associations support the production of
such a report. These reports would
summarize the data presented in the
individual LOA-holder reports, provide
analysis of these synthesized results,
discuss the implementation of required
mitigation, and present any
recommendations. This comprehensive
annual report would be the basis of an
annual adaptive management process
(described below in Adaptive
Management). The following topics will
be described in comprehensive
reporting:
• Summary of geophysical survey
activity by survey type, geographic zone
(i.e., the seven zones described in the
modeling report), month, and acoustic
source status (e.g., inactive, ramp-up,
full-power, power-down);
• Summary of monitoring effort (oneffort hours and/or distance) by acoustic
source status, location, and visibility
conditions (for both visual and acoustic
monitoring);
• Summary of mitigation measures
implemented (e.g., delayed ramp-ups,
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shutdowns, course alterations for vessel
strike avoidance) by survey type and
location;
• Sighting rates of marine mammals
during periods with and without
acoustic source activities and other
variables that could affect detectability
of marine mammals, such as:
Æ Initial sighting distances of marine
mammals relative to source status;
Æ Closest point of approach of marine
mammals relative to source status;
Æ Observed behaviors and types of
movements of marine mammals relative
to source status;
Æ Distribution/presence of marine
mammals around the survey vessel
relative to source status; and
Æ Analysis of the effects of various
factors influencing the detectability of
marine mammals (e.g., wind speed, sea
state, swell height, presence of glare or
fog).
• Estimates of total take across all
activities for which take is authorized
based on actual survey effort and
original estimation method;
• Summary and conclusions from
monitoring in previous year; and
• Recommendations for adaptive
management.
Each annual comprehensive report
should cover one full year of monitoring
effort and must be submitted for review
each year. Each report should analyze
survey and monitoring effort described
in reports submitted by individual LOAholders during a given one-year period,
beginning from the date of effectiveness
of these regulations. Each annual
comprehensive report must be
submitted for review 90 days following
conclusion of the annual reporting
period.
Reporting Injured or Dead Marine
Mammals
Discovery of Injured or Dead Marine
Mammal—In the event that personnel
involved in the survey activities covered
by the authorization discover an injured
or dead marine mammal, the LOAholder shall report the incident to the
Office of Protected Resources (OPR),
NMFS and to the regional stranding
network as soon as feasible. The report
must include the following information:
• Time, date, and location (latitude/
longitude) of the first discovery (and
updated location information if known
and applicable);
• Species identification (if known) or
description of the animal(s) involved;
• Condition of the animal(s)
(including carcass condition if the
animal is dead);
• Observed behaviors of the
animal(s), if alive;
• If available, photographs or video
footage of the animal(s); and
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• General circumstances under which
the animal was discovered.
Vessel Strike—In the event of a ship
strike of a marine mammal by any vessel
involved in the activities covered by the
authorization, the LOA-holder shall
report the incident to OPR, NMFS and
to the regional stranding network as
soon as feasible. The report must
include the following information:
• Time, date, and location (latitude/
longitude) of the incident;
• Species identification (if known) or
description of the animal(s) involved;
• Vessel’s speed during and leading
up to the incident;
• Vessel’s course/heading and what
operations were being conducted (if
applicable);
• Status of all sound sources in use;
• Description of avoidance measures/
requirements that were in place at the
time of the strike and what additional
measures were taken, if any, to avoid
strike;
• Environmental conditions (e.g.,
wind speed and direction, Beaufort sea
state, cloud cover, visibility)
immediately preceding the strike;
• Estimated size and length of animal
that was struck;
• Description of the behavior of the
marine mammal immediately preceding
and following the strike;
• If available, description of the
presence and behavior of any other
marine mammals immediately
preceding the strike;
• Estimated fate of the animal (e.g.,
dead, injured but alive, injured and
moving, blood or tissue observed in the
water, status unknown, disappeared);
and
• To the extent practicable,
photographs or video footage of the
animal(s).
Actions To Minimize Additional Harm
to Live-Stranded (or Milling) Marine
Mammals
For deep penetration surveys, in the
event of a live stranding (or near-shore
atypical milling) event within 50 km of
the survey operations, where the NMFS
stranding network is engaged in herding
or other interventions to return animals
to the water, the Director of OPR, NMFS
(or designee) will advise the LOAholder of the need to implement
shutdown procedures for all active
acoustic sources operating within 50 km
of the stranding. Shutdown procedures
for live stranding or milling marine
mammals include the following:
• If at any time, the marine mammals
die or are euthanized, or if herding/
intervention efforts are stopped, the
Director of OPR, NMFS (or designee)
will advise the LOA-holder that the
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5425
shutdown around the animals’ location
is no longer needed.
• Otherwise, shutdown procedures
will remain in effect until the Director
of OPR, NMFS (or designee) determines
and advises the LOA-holder that all live
animals involved have left the area
(either of their own volition or following
an intervention).
• If further observations of the marine
mammals indicate the potential for restranding, additional coordination with
the LOA-holder will be required to
determine what measures are necessary
to minimize that likelihood (e.g.,
extending the shutdown or moving
operations farther away) and to
implement those measures as
appropriate.
Shutdown procedures are not related
to the investigation of the cause of the
stranding and their implementation is
not intended to imply that the specified
activity is the cause of the stranding.
Rather, shutdown procedures are
intended to protect marine mammals
exhibiting indicators of distress by
minimizing their exposure to possible
additional stressors, regardless of the
factors that contributed to the stranding.
Additional Information Requests—If
NMFS determines that the
circumstances of any marine mammal
stranding found in the vicinity of the
activity suggest investigation of the
association with survey activities is
warranted (example circumstances
noted below), and an investigation into
the stranding is being pursued, NMFS
will submit a written request to the
LOA-holder indicating that the
following initial available information
must be provided as soon as possible,
but no later than 7 business days after
the request for information.
• Status of all sound source use in the
48 hours preceding the estimated time
of stranding and within 50 km of the
discovery/notification of the stranding
by NMFS; and
• If available, description of the
behavior of any marine mammal(s)
observed preceding (i.e., within 48
hours and 50 km) and immediately after
the discovery of the stranding.
Examples of circumstances that could
trigger the additional information
request include, but are not limited to,
the following:
• Atypical nearshore milling events
of live cetaceans;
• Mass strandings of cetaceans (two
or more individuals, not including cow/
calf pairs);
• Beaked whale strandings; or,
• Necropsies with findings of
pathologies that are unusual for the
species or area.
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In the event that the investigation is
still inconclusive, the investigation of
the association of the survey activities is
still warranted, and the investigation is
still being pursued, NMFS may provide
additional information requests, in
writing, regarding the nature and
location of survey operations prior to
the time period above.
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Negligible Impact Analysis and
Determinations
NMFS has defined negligible impact
as an impact resulting from the
specified activity that cannot be
reasonably expected to, and is not
reasonably likely to, adversely affect the
species or stock through effects on
annual rates of recruitment or survival
(50 CFR 216.103). A negligible impact
finding is based on the lack of likely
adverse effects on annual rates of
recruitment or survival (i.e., populationlevel effects). An estimate of the number
of takes alone is not enough information
on which to base a negligible impact
determination. In addition to
considering estimates of the number of
marine mammals that might be ‘‘taken’’
by mortality, serious injury, and Level A
or Level B harassment, we consider
other factors, such as the type of take,
the likely nature of any behavioral
responses (e.g., intensity, duration), the
context of any such responses (e.g.,
critical reproductive time or location,
migration), as well as effects on habitat,
and the likely effectiveness of
mitigation. We also assess the number,
intensity, and context of estimated takes
by evaluating this information relative
to population status. Consistent with the
1989 preamble for NMFS’ implementing
regulations (54 FR 40338; September 29,
1989), the impacts from other past and
ongoing anthropogenic activities are
incorporated into these analyses via
their impacts on the baseline (e.g., as
reflected in the regulatory status of the
species, population size and growth rate
where known, ongoing sources of
human-caused mortality).
For each potential activity-related
stressor, NMFS considers the potential
effects to marine mammals and the
likely significance of those effects to the
species or stock as a whole. Potential
risk due to vessel collision and related
mitigation measures, as well as potential
risk due to entanglement and
contaminant spills, was addressed
under Mitigation and in the Potential
Effects of the Specified Activity on
Marine Mammals section of this notice
and the notice of proposed rulemaking
and are not discussed further, as there
are minimal risks expected from these
potential stressors.
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The ‘‘specified activity’’ for these
regulations is a broad program of
geophysical survey activity that could
occur at any time of year in U.S. waters
of the GOM, within the specified
geographical region as updated by
BOEM (i.e., excluding the GOMESA
leasing moratorium area). In recognition
of the broad scale of this activity in
terms of geographic and temporal scales,
we use a new analytical methodology—
first described by Ellison et al. (2015)
and proposed for use and discussed in
detail in the notice of proposed
rulemaking—through which an explicit,
systematic risk assessment framework is
applied to evaluate potential effects of
aggregated discrete acoustic exposure
events (i.e., proposed geophysical
survey activities) on marine mammals.
This risk assessment framework is one
component of the overall negligible
impact analysis. Development of the
approach was supported collaboratively
by BOEM and NMFS, which together
provided guidance to an expert working
group (EWG) in terms of application to
relevant regulatory processes. The risk
assessment framework (or EWG
framework) is described by Southall et
al. (2017), which is available online at:
www.fisheries.noaa.gov/national/
marine-mammal-protection/incidentaltake-authorizations-oil-and-gas. That
document is a companion to this
analysis, and is referred to hereafter as
the ‘‘EWG report.’’ The risk assessment
framework is also described below. It
was developed and implemented by the
EWG in relation to the specified activity
described in the proposed rule,
provided for public review in
association with the notice of proposed
rulemaking (Southall et al., 2017), and
subsequently refined in response to
public comment and in consideration of
the updated scope of the activity. We
incorporate the framework and its
results into this analysis.
The EWG framework described below
comprehensively considers the
aggregate impacts to marine mammal
populations from the activities
addressed in this rule in the context of
both (1) the severity of the impacts and
(2) the vulnerability of the affected
species. However, it does not consider
the effects of the mitigation required
through these regulations in identifying
risk ratings for the affected species. In
addition, while the EWG framework
comprehensively considers the spatial
and temporal overlay of the activities
and the marine mammals in the GOM,
as well as the number of takes predicted
by the described modeling (both in the
proposed rule, and as updated in this
final rule), there are details about the
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nature of any ‘‘take’’ anticipated to
result from these activities that were not
considered directly in the EWG
framework analysis that warrant explicit
consideration in the negligible impact
determination. Last, the EWG
framework analysis addresses impacts
to guilds in some cases where there is
not specific information to further
support species-specific findings.
Accordingly, following the description
of the EWG framework below, NMFS
highlights a few factors regarding the
nature of the predicted ‘‘takes’’ and then
brings together the results of
implementation of the EWG framework,
these additional factors, and the
anticipated effects of the mitigation to
summarize the negligible impact
analysis for each of the affected species
or stocks.
EWG Risk Assessment
The acoustic exposure modeling
(Zeddies et al., 2015, 2017a) provided
marine mammal noise exposure
estimates based on BOEM-provided
projections of future survey effort and
best available modeling of sound
propagation, animal distribution, and
animal movement. This provided a
conservative but reasonable best
estimate of potential acute noise
exposure events that may result from
the described suite of activities, and
formed the basis for the analysis in the
proposed rule. BOEM subsequently
updated the scope of its activity, which
reduced the amount of activity overall
through removal of projected activity in
the eastern GOM (see Table 1 and Figure
2). Acoustic exposure estimates were
updated by BOEM accordingly (based
on the same modeling presented in the
proposed rule) and these revised
estimates form the basis for this updated
analysis.
The primary goal of this new
analytical effort was to develop a
systematic risk assessment framework
that would use the modeling results to
put into biologically-relevant context
the level of potential risk of injury and/
or disturbance to marine mammals. The
risk assessment framework considers
both the aggregation of acute effects and
the broad temporal and spatial scales
over which chronic effects may occur.
Previously, Wood et al. (2012)
conducted an analysis of a proposed
airgun survey, in which the authors
derived a qualitative risk assessment
method of considering the biological
significance of exposures predicted to
be consistent with the onset of physical
injury and behavioral disturbance.
Subsequently, Ellison et al. (2015)
described development of a more
systematic and (in some cases)
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quantitative basis for a risk assessment
approach to assess the biological
significance and potential population
consequences of predicted noise
exposures. The approach for this final
rule, which incorporates the revised
acoustic exposure modeling results as
an input, includes certain modifications
to and departures from the conceptual
approach described by Ellison et al.
(2015). These are described in greater
detail in the EWG report.
Generally, this approach is a
relativistic risk assessment that provides
an interpretation of the exposure
estimates within the context of key
biological and population parameters
(e.g., population size, life history
factors, compensatory ability of the
species, animal behavioral state,
aversion), as well as other biological,
environmental, and anthropogenic
factors. This analysis as updated since
BOEM revised the scope of its action
was performed on a species-specific
basis within each modeling zone (Figure
3) for a high-effort scenario (represented
by Year 1 of BOEM’s revised effort
projections) and a moderate-effort
scenario (represented by Year 4 of
BOEM’s revised effort projections). (For
most species, the maximum annual take
occurs under the Year 1 scenario. The
two exceptions are the bottlenose
dolphin and Atlantic spotted dolphin,
for which the maximum annual take
occurs under the Year 4 scenario.) The
end result provides an indication of the
biological significance of these exposure
numbers for each affected marine
mammal stock (i.e., yielding the severity
of impact and vulnerability of stock/
population information), and forecasts
the likelihood of any such impact. This
result is expressed as relative impact
ratings of overall risk that couple
potential severity of effect on a stock
and likely vulnerability of the
population to the consequences of those
effects, given biologically relevant
information (e.g., compensatory ability).
Spectral, temporal, and spatial
overlaps between survey activities and
animal distribution are the primary
factors that drive the type, magnitude,
and severity of potential effects on
marine mammals, and these
considerations are integrated into both
the severity and vulnerability
assessments. In discussion with BOEM
and NMFS, the EWG developed a
strategic approach to balance the weight
of these considerations between the two
assessments, specifying and clarifying
where and how the interactions between
potential disturbance and species
within these dimensions are evaluated.
Overall ratings are then considered in
conjunction with the required
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mitigation (and any additional relevant
contextual information) to ultimately
inform our determinations. Elements of
this approach are subjective and relative
within the context of this program of
projected actions and, overall, the
analysis necessarily requires the
application of professional judgment.
Severity of Effect
Level A Harassment—In order to
evaluate the potential severity of the
expected potential takes by Level A
harassment (accounting for aversion)
(Table 9) on the species or stock, the
EWG framework uses a potential
biological removal (PBR)-equivalent
metric. As described previously, PBR is
defined by the MMPA as the maximum
number of animals, not including
natural mortalities, that may be removed
from a marine mammal stock while
allowing that stock to reach or maintain
its optimum sustainable population. To
be clear, NMFS does not expect any of
the potential occurrences of injury (i.e.,
permanent threshold shift (PTS)) that
may be authorized under this rule to
result in mortality of marine mammals,
nor should Level A harassment be
considered a ‘‘removal’’ in the context
of PBR when used to inform a negligible
impact determination. PTS is not
appropriately considered equivalent to
serious injury. However, PBR can serve
as a gross indicator of the status of the
species and a good surrogate for
population vulnerability/health and,
accordingly, PBR or a related metric can
be used appropriately to inform a
separate analysis to evaluate the
potential relative severity to the
population of a permanent impact such
as PTS on a given number of
individuals. This analysis is used to
assess relative risks to populations as a
result of PTS; NMFS does not expect
that Level A harassment could directly
result in mortality and our use of the
PBR metric in this context should not be
interpreted as such.
However, exposure estimates
generated using habitat-based density
models (Roberts et al., 2016) cannot
appropriately be directly related to the
PBR values found in NMFS’ SARs.
Therefore, a modified PBR value was
derived on the basis of the typical
pattern for NMFS’ PBR values, where
the value varies between approximately
0.6–0.9 percent of the minimum
population abundance depending upon
population confidence limits (higher
with increasing confidence). For
endangered species, PBR values are
typically 1⁄5 of the values for nonendangered species due to assumption
of a lower recovery factor—endangered
species are typically assigned recovery
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5427
factors of 0.1, while species of unknown
status relative to the optimum
sustainable population level (i.e., most
species) are typically assigned factors of
0.5. This basic relationship of
population size relative to PBR was
used to define the following relative risk
levels due to Level A harassment.
• Very high—Level A harassment
greater than 1.5 or 0.3 percent (the latter
figure is used for endangered species) of
zone-specific estimated population
abundance.
• High—0.75–1.5 or 0.15–0.3 percent
of zone-specific population.
• Moderate—0.375–0.75 or 0.075–
0.15 percent of zone-specific
population.
• Low—0.075–0.375 or 0.015–0.075
percent of zone-specific population.
• Very low—less than 0.075 or less
than 0.015 percent of zone-specific
population.
Relative severity scores by zone
(Figure 3) and species were determined
for high and moderate annual effort
scenarios. As described previously, we
do not believe that Level A harassment
is likely to actually occur for midfrequency cetaceans and therefore do
not predict (nor will we authorize) any
take by Level A harassment for these
species (i.e., most species in the GOM).
Bryde’s whales (a low-frequency
cetacean species) are expected to be
present primarily in Zones 1 and 4
(though may be present to a lesser
extent in Zones 2 and 5). BOEM’s
update to the geographic scope of its
action removed the entirety of Zone 1
and the majority of Zone 4 from
consideration in this rule. Altogether,
no incidents of Level A harassment are
predicted for Bryde’s whales.
Kogia spp. (high-frequency cetacean
species) are primarily present in Zones
4–7. We assess the relative severity
resulting from injury for Kogia spp. to
be ‘‘very high’’ in Zones 5–7 under both
evaluated activity scenarios. In Zone 4,
relative severity is ‘‘high’’ under the
moderate effort scenario, and no activity
is projected in Zone 4 under the high
effort scenario.
In summary, we assess that there is no
risk of Level A harassment for any midfrequency cetacean species. Overall
severity associated with take by Level A
harassment is expected to be very high
for Kogia spp. and very low for Bryde’s
whales, as no incidents of Level A
harassment are predicted for the stock.
We note that regardless of the relative
risk assessed in this framework, because
of the anticipated received levels and
duration of sound exposure expected for
any marine mammals exposed above
Level A harassment criteria, no
individuals of any species or stock are
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expected to receive more than a
relatively minor degree of PTS, which
would not be expected to meaningfully
increase the likelihood or severity of
any potential population-level effects.
See ‘‘Loss of Hearing Sensitivity,’’
below, for additional discussion.
Level B Harassment—As described
above in Estimated Take, a significant
model assumption was that populations
of animals were reset for each 24-hr
period. Exposure estimates for the 24-hr
period were then aggregated across all
assumed survey days as completely
independent events, assuming
populations turn over completely
within each large zone on a daily basis.
In order to evaluate modeled daily
exposures and determine more realistic
exposure probabilities for individuals
across multiple days, we used
information on species-typical
movement behavior to determine a
species-typical offset of modeled daily
exposures, using the exploratory
analysis discussed under Estimated
Take (i.e., Test Scenario 1). In this test
scenario, modeled results were
compared for a 30-day period versus the
aggregation of 24-hr population reset
intervals. When conducting
computationally-intensive modeling
over the full assumed 30-day survey
period (versus aggregating the smaller
24-hr periods for 30 days), results
showed about 10–45 percent of the total
number of takes calculated using a 24hr reset of the population, with
differences relating to species-typical
movement and residency patterns.
Given that many of the evaluated survey
activities occur for 30-day or longer
periods, particularly some of the larger
surveys for which the majority of the
modeled exposures occur, using such a
scaling process is appropriate in order
to evaluate the likely severity of the
predicted exposures and to estimate
take for the purposes of LOA
applications and predicting the number
of individual marine mammals taken
during the course of a single survey
(although, as noted previously, for
surveys significantly longer than 30
days, the take numbers with this scaling
applied would still be expected to
overestimate the number of individuals,
given the greater degree of repeat
exposures that would be expected the
longer the survey goes on). This output
was used in a severity assessment. This
approach is also discussed in more
detail in the EWG report.
Similar to the evaluation of severity
for Level A harassment, the scaled Level
B harassment takes were rated through
a population-dependent binning system.
For each species, scaled takes were
divided by the zone-specific predicted
abundance, and these proportions were
used to evaluate the relative severity of
modeled exposures based on the
distribution of values across species to
evaluate risk associated with behavioral
disruption across species—a simple,
logical means of evaluating relative risk
across species and areas. Relative risk
ratings using percent of area population
size were defined as follows:
• Very high—Adjusted Level B
harassment takes greater than 800
percent of zone-specific population;
• High—Adjusted Level B harassment
takes 401–800 percent of zone-specific
population;
• Moderate—Adjusted Level B
harassment takes 201–400 percent of
zone-specific population;
• Low—Adjusted Level B harassment
takes 100–200 percent of zone-specific
population; and
• Very low—Adjusted Level B
harassment takes less than 100 percent
of zone-specific population.
Vulnerability of Affected Population
Vulnerability rating seeks to evaluate
the relative risk of a predicted effect
given species-typical and populationspecific parameters (e.g., speciesspecific life history, population factors)
and other relevant interacting factors
(e.g., human or other environmental
stressors). The assessment includes
consideration of four categories within
two overarching risk factors (speciesspecific biological and environmental
risk factors). These values were selected
to capture key aspects of the importance
of spatial (geographic), spectral
(frequency content of noise in relation
to species-typical hearing and sound
communications), and temporal
relationships between sound and
receivers. Explicit numerical criteria for
identifying scores were specified where
possible, but in some cases qualitative
judgments based on a reasonable
interpretation of given aspects of the
proposed activity and how it relates to
the species in question and the
environment within the specified area
were required. Factors considered in the
vulnerability assessment were detailed
in Southall et al. (2017) and are
reproduced here (Table 11). Note that
the effects of the Deepwater Horizon oil
spill are accounted for through the nonnoise chronic anthropogenic risk factor
identified below, while the effects to
acoustic habitat and on individual
animal behavior via masking
(summarized in Potential Effects of the
Specified Activity on Marine Mammals
and Their Habitat and described in
detail in that section of the notice of
proposed rulemaking) are accounted for
through the masking and chronic
anthropogenic noise risk factors.
Species-specific vulnerability scoring
according to this scheme is shown in
Table 12. Zone-specific vulnerability
ratings corresponding with the scores
given in Table 12 below are provided in
Tables 8–10 of the EWG report.
TABLE 11—VULNERABILITY ASSESSMENT FACTORS
khammond on DSKJM1Z7X2PROD with RULES2
Score
Masking: Degree of spectral overlap between biologically important acoustic signals
and predominant noise source of proposed activity (max: 7 out of 30):
Communication masking: Predominant noise energy directly/partially overlaps 1 species-specific signals utilized for communication.
Foraging masking: Predominant noise energy directly/partially overlaps1 species-specific signals utilized in foraging (including echolocation and other foraging coordination signals).
Navigation/Orientation signal masking: Predominant noise energy directly/partially overlaps1 signals likely utilized in spatial orientation to which species is well capable of hearing.
Species population: Stock status, trend, and size (max: 7 out of 30):
Population status: Endangered (ESA) and/or depleted (MMPA) (Y/N) ....................................................................................
Trend rating: Decreasing/unknown or data deficient/stable (i.e., within 5 percent)/increasing (last three SARs for which
new population estimates were updated).
Population size: Small (less than 2,500) ...................................................................................................................................
Species habitat use and compensatory abilities: Degree to which activity within a specified area 2 overlaps with species habitat and distribution (max: 7 out of 30):
Habitat use: Survey area contains greater than 30/15–30/5–15/less than 5 percent of total region-wide estimated population (during defined survey period).
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+2
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TABLE 11—VULNERABILITY ASSESSMENT FACTORS—Continued
Score
Temporal sensitivity: Survey overlaps temporally with well-defined species-specific biologically-important period (e.g.,
calving).
Other (chronic) noise and non-noise stressors: Magnitude of other potential sources of disturbance or other stressors that
may influence a species response to additional noise and disturbance of the proposed activity (max: 9 out of 30):
Chronic anthropogenic noise: Species subject to high/moderate degree of current or known future (overlapping activity)
chronic anthropogenic noise.
Chronic anthropogenic risk factors (non-noise): Species subject to high/moderate degree of current or known future risk
from other chronic, non-noise anthropogenic activities (e.g., fisheries interactions, ship strike).
Chronic biological risk factors (non-noise): Known presence of disease, parasites, prey limitation, or high predation pressure.
Up to +3
+2/+1
Up to +4/+2
Up to +3
1 Direct or partial overlap means that the predominant spectral content of received noise exposure from activity specific sources is expected to
occur at identical frequencies as signals of interest, or that secondary (lower-level) spectral content of received noise exposure from activity specific sources is expected to occur at identical frequencies as signals of interest.
2 This is the area over which an activity is evaluated and a local population is determined, in this case the seven modeling zones.
TABLE 12—VULNERABILITY ASSESSMENT SCORING 1
Communication
Species
Bryde’s whale
Sperm whale
Kogia spp. .....
Beaked whale
Rough-toothed
dolphin .......
Bottlenose
dolphin .......
Clymene dolphin ............
Atlantic spotted dolphin
Pantropical
spotted dolphin ............
Spinner dolphin ............
Striped dolphin ............
Fraser’s dolphin ............
Risso’s dolphin ............
Melon-headed
whale .........
Pygmy killer
whale .........
False killer
whale .........
Killer whale ....
Short-finned
pilot whale
1 Factors
Foraging
Navigation
Status
Trend
Size
Habitat
Chronic
noise
Time
Chronic
other
Total
score
range
Biological
risk
3
1
0
0
2
1
0
0
2
2
1
1
3
3
0
0
2
2
2
1
2
2
2
0
0–4
0–4
0–4
0–4
0–1
0–1
0–1
0–1
1–2
1–2
1–2
1–2
0–3
0–3
0–3
0–3
0
0
0
1
16–23
14–18
8–13
6–13
0
0
1
0
2
0
1–4
0–1
1–2
0–3
0
6–10
1
0
1
0
¥1
0
0–4
0–1
1–2
0–3
0
2–10
0
0
1
0
2
0
0–4
0–1
1–2
0–3
0
6–10
1
0
1
0
1
0
0–4
0–1
1–2
0–3
2
6–14
0
0
1
0
2
0
0–4
0–1
1–2
0–3
0
6–10
0
0
1
0
0
0
0–4
0–1
1–2
0–3
0
3–9
0
0
1
0
2
0
0–4
0–1
1–2
0–3
0
6–10
0
0
1
0
1
2
0–4
0–1
1–2
0–3
0
7–11
0
0
1
0
¥1
0
0–4
0–1
1–2
0–3
1
4–9
0
0
1
0
2
0
0–4
0–1
1–2
0–3
0
6–10
0
0
1
0
2
2
0–4
0–1
1–2
0–3
0
8–12
0
1
0
0
1
1
0
0
¥1
2
0
2
0–4
0–4
0–1
0–1
1–2
1–2
0–3
0–3
0
0
3–7
9–12
1
0
1
0
0
2
0–4
0–1
1–2
0–3
1
7–13
with a single value presented are those that remain constant across zones; other factors vary based on zone and a range of values is presented.
TABLE 13—VULNERABILITY RATING SCHEME
Risk
probability
(% of total)
Total score
24–30 .........................................................................................................................................
18–23 .........................................................................................................................................
12–17 .........................................................................................................................................
6–11 ...........................................................................................................................................
0–5 .............................................................................................................................................
khammond on DSKJM1Z7X2PROD with RULES2
Risk
In the final step of the framework,
severity and vulnerability ratings are
integrated to provide relative impact
ratings of overall risk. Severity and
vulnerability assessments each produce
a numerical rating (1–5) corresponding
with the qualitative rating (i.e., very
low, low, moderate, high, very high). A
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matrix is then used to integrate these
two scores to provide an overall risk
assessment. The matrix is shown in
Table 2 of Southall et al. (2017).
The likely severity of effect was
assessed as the percentage of total
population affected based on scaled
modeled Level B harassment takes
relative to zone population size. There
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80–100
60–79
40–59
20–39
0–19
Vulnerability rating
Very high.
High.
Moderate.
Low.
Very low.
is no risk due to the effects of survey
activity when there is no survey activity
in a given zone for a given effort
scenario. However, a stock’s inherent
zone-specific vulnerability score drives
the risk rating in those zones (Zone 1
under any activity scenario and Zone 4
under the high effort scenario), and risk
ratings for all zones are considered
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together in generating scenario-specific
GOM-wide risk ratings for each species.
Also, zones predicted to contain
abundance of less than 0.05 percent of
the GOM-wide population for a species
were considered to have de minimis risk
and are not included in derivation of the
stock-specific GOM-wide rating.
Table 14 provides relative impact
ratings by zone, and Table 15 provides
GOM-wide relative impact ratings, for
overall risk associated with predicted
takes by Level B harassment, for
representative high and moderate effort
scenarios.
TABLE 14—OVERALL EVALUATED RISK BY ZONE AND ACTIVITY SCENARIO
Zone 1 1
Zone 2
Zone 4 1
Zone 3
Zone 5
Zone 6
Zone 7
Species
H
Bryde’s whale .......................
Sperm whale .........................
Kogia spp. .............................
Beaked whale .......................
Rough-toothed dolphin .........
Bottlenose dolphin ................
Clymene dolphin ...................
Atlantic spotted dolphin ........
Pantropical spotted dolphin ..
Spinner dolphin .....................
Striped dolphin ......................
Fraser’s dolphin ....................
Risso’s dolphin .....................
Melon-headed whale ............
Pygmy killer whale ................
False killer whale ..................
Killer whale ...........................
Short-finned pilot whale ........
L
n/a
VL
n/a
VL
VL
n/a
L
VL
VL
n/a
VL
VL
VL
VL
VL
VL
n/a
M
L
n/a
VL
n/a
VL
VL
n/a
L
VL
VL
n/a
VL
VL
VL
VL
VL
VL
n/a
H
L
n/a
n/a
n/a
L
H
n/a
H
n/a
n/a
n/a
VL
n/a
n/a
n/a
VL
VL
n/a
M
L
n/a
n/a
n/a
M
H
n/a
VH
n/a
n/a
n/a
VL
n/a
n/a
n/a
VL
VL
n/a
H
n/a
n/a
n/a
n/a
VL
VL
n/a
VL
n/a
n/a
n/a
VL
n/a
n/a
n/a
VL
VL
n/a
M
n/a
n/a
n/a
n/a
VL
VL
n/a
VL
n/a
n/a
n/a
VL
n/a
n/a
n/a
VL
VL
n/a
H
M
L
L
L
VL
VL
VL
VL
VL
VL
VL
VL
VL
VL
VL
VL
VL
VL
VL
L
L
L
VL
VL
VL
VL
VL
VL
VL
VL
VL
VL
VL
VL
VL
VL
VL
H
L
VH
H
VH
H
VL
H
M
H
H
H
M
H
H
M
H
L
M
M
L
VH
M
VH
M
VL
M
L
M
M
M
L
M
M
L
M
L
M
H
M
n/a
M
L
H
M
n/a
M
n/a
L
n/a
L
L
M
M
L
L
VL
M
n/a
L
VL
M
L
n/a
L
n/a
VL
n/a
VL
VL
VL
VL
VL
VL
VL
VL
H
n/a
L
VL
M
VL
n/a
VL
n/a
L
VL
L
VL
VL
VL
VL
VL
L
VL
M
n/a
L
VL
L
VL
n/a
VL
n/a
L
VL
VL
VL
VL
VL
VL
VL
L
VL
H = Year 1 (representative high effort scenario); M = Year 4 (representative moderate effort scenario).
n/a = less than 0.05% of GOM-wide population predicted in zone.
VL = very low; L = low; M = moderate; H = high; VH = very high.
1 No activity would occur in Zone 1, and no activity is projected in Zone 4 under the high effort scenario.
TABLE 15—OVERALL EVALUATED RISK BY ACTIVITY SCENARIO, GOM-WIDE
Species
High effort scenario
(Year 1)
Bryde’s whale ................................................................................................................
Sperm whale ..................................................................................................................
Kogia spp. ......................................................................................................................
Beaked whales ..............................................................................................................
Rough-toothed dolphin ..................................................................................................
Bottlenose dolphin (shelf/coastal) ..................................................................................
Bottlenose dolphin (oceanic) .........................................................................................
Clymene dolphin ............................................................................................................
Atlantic spotted dolphin .................................................................................................
Pantropical spotted dolphin ...........................................................................................
Spinner dolphin ..............................................................................................................
Striped dolphin ...............................................................................................................
Fraser’s dolphin .............................................................................................................
Risso’s dolphin ...............................................................................................................
Melon-headed whale .....................................................................................................
Pygmy killer whale .........................................................................................................
False killer whale ...........................................................................................................
Killer whale ....................................................................................................................
Short-finned pilot whale .................................................................................................
Low .....................................
Moderate 1 ..........................
Low .....................................
High 1 ..................................
Very low .............................
Very low .............................
Very low .............................
Low .....................................
Low .....................................
Low .....................................
Very low .............................
Low .....................................
Very low .............................
Very low .............................
Very low .............................
Very low .............................
Very low .............................
Very low .............................
Low .....................................
khammond on DSKJM1Z7X2PROD with RULES2
1 For
Moderate effort scenario
(Year 4)
Low.
Low.
Very low.
Moderate.1
Very low.
Very low.
Very low.
Low.1
Low.
Very low.
Very low.
Very low.
Very low.
Very low.
Very low.
Very low.
Very low.
Very low.
Low.1
these ratings, the median value across zones for the scenario fell between two ratings, and the higher rating is presented.
In order to characterize the relative
risk for each species across their entire
range in the GOM, the EWG analysis
used the median of the seven zonespecific risk ratings for each activity
scenario (high and moderate effort), not
counting those in which less than 0.05
percent of the GOM-wide abundance
occurred, to describe a GOM-wide risk
rating for each of the representative
activity scenarios (Table 15).
Overall, the results of the risk
assessment show that (as expected), risk
is highly correlated with effort and
density. Areas where little or no survey
activity is predicted to occur or areas
within which few or no animals of a
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particular species are believed to occur
have very low or no potential risk of
negatively affecting marine mammals, as
seen across activity scenarios in Zones
1, 3, and 4. Areas with consistently high
levels of effort (Zones 2, 5, 6, and 7) are
generally predicted to have higher
overall evaluated risk across all species.
However, fewer species of animals are
expected to be present in Zone 2, where
we primarily expect shelf species such
as bottlenose and Atlantic spotted
dolphins. In Zone 7, animals are
expected to be subject to less other
chronic noise and non-noise stressors,
which is reflected in the vulnerability
scoring for that zone. Therefore, despite
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consistently high levels of projected
effort, overall rankings for that zone are
lower than for Zones 5 and 6.
Zones 2 and 5 were the only zones
with ‘‘very high’’ levels of risk due to
behavioral disturbance, identified for
two species of particular concern in
Zone 5 (beaked and sperm whales) and
for Atlantic spotted dolphins in Zone 2
(moderate effort scenario only). As
particularly sensitive species, beaked
whales and sperm whales consistently
receive relatively high severity scores.
For sperm whales, this sensitivity is
manifest through typically higher
vulnerability scoring, whereas the
assumed sensitivity of beaked whales to
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khammond on DSKJM1Z7X2PROD with RULES2
noise exposure is expressed through the
application of behavioral harassment
criteria (Table 6) and, therefore,
relatively high assumed take numbers.
Bottlenose dolphins and Atlantic
spotted dolphin are generally the only
species expected to commonly occur in
relatively shallow waters of the
continental shelf (Zones 1–3) and
relatively high risk is assessed for these
species in Zone 2, across activity
scenarios. Relatively moderate levels of
risk were also identified for other
species in some contexts, and these are
generally explained by the interaction of
specific factors related to survey effort
concentration and areas of heightened
geographic distribution or specific
factors related to population trends or
zone-related differences in
vulnerability. Overall, following
BOEM’s update to the geographic scope
of activity (with the entirety of Zone 1,
most of Zone 4, and one-third of Zone
7 removed from consideration here; see
Table 1) the greatest relative risk across
species is generally seen in Zones 5 and
6.
When considered across both
representative activity scenarios (Table
15), only beaked whales are considered
to have relatively high risk (under the
high effort scenario only). Relatively
moderate risk is assessed for beaked
whales under the moderate effort
scenario. Relatively moderate risk is
also assessed for sperm whales under
the high effort scenario. The rest of the
species have no more than low to very
low risk under either scenario. Shelf/
coastal and oceanic bottlenose dolphin
stocks, rough-toothed dolphins, spinner
dolphins, Fraser’s dolphins, Risso’s
dolphins, melon-headed whales, pygmy
killer whales, false killer whales, and
killer whales are assessed as having no
greater than very low relative risk under
any scenario.
Although the scores generated by the
EWG framework and further aggregated
across zones (as described above) are
species-specific, additional stockspecific information can be gleaned
through the zone-specific nature of the
analysis. For example, with some
bottlenose dolphin stocks, the zones
align with stock range edges. The
oceanic stock of bottlenose dolphins
occurs within Zones 4–7, while coastal
5431
1.8 minutes—a minimal amount of
exposure carrying little potential for
significant disruption of behavioral
activity. We provide summary
information regarding the total average
time in a 24-hr period that an animal
would spend with received levels above
160 dB and between 140 and 160 dB in
Table 16.
Additionally, as we discussed in the
Estimated Take section of the notice of
proposed rulemaking for Test Scenario
1 (and summarized above), by
comparing exposure estimates generated
by multiplying 24-hr exposure estimates
by the total number of survey days
versus modeling for a full 30-day survey
duration for six representative species,
we were able to refine the exposure
estimates to better reflect the number of
individuals exposed above threshold
within a single survey. Using this same
comparison and scalar ratios described
above, we are able to predict an average
number of days each of the
representative species modeled in the
test scenario were exposed above the
Level B harassment thresholds within a
single survey. As with the duration of
exposures discussed above, the number
of repeated exposures is important to an
understanding of the severity of effects.
For example, the ratio for beaked whales
indicates that the 30-day modeling
showed that approximately 10 percent
as many individual beaked whales
(compared to the results produced by
multiplying average 24-hr exposure
results by the 30-day survey duration)
could be expected to be exposed above
harassment thresholds. However, the
approach of scaling up the 24-hour
exposure estimates appropriately
reflects the instances of exposure above
threshold (which cannot be more than 1
in 24 hours), so the inverse of the scalar
ratio suggests the average number of
days in the 30-day modeling period that
beaked whales are exposed above
threshold is approximately ten. It is
important to remember that this is an
average and that it is likely some
individuals would be exposed on fewer
days and some on more. Table 16
reflects the average days exposed above
threshold for the indicated species
having applied the scalar ratios
described previously.
and shelf stocks occur within Zones 1–
3 (sufficient information is not available
to attribute takes on a stock-specific
basis in Zones 1–3). These speciesspecific risk ratings are broadly applied
in NMFS’ negligible impact analysis to
all of the multiple stocks that are
analyzed in this rule (Table 4).
However, NMFS is also considering
additional stock-specific information in
our analysis, where appropriate, as
indicated in our Description of Marine
Mammals in the Area of the Specified
Activity, Potential Effects of the
Specified Activity on Marine Mammals
and Their Habitat, and Mitigation
sections (e.g., coastal bottlenose
dolphins were heavily impacted by the
DWH oil spill, and we have therefore
required a time/area restriction to
reduce impacts).
Duration of Level B Harassment
Exposures
In order to more fully place the
predicted amount of take into
meaningful context, it is useful to
understand the duration of exposure at
or above a given level of received sound,
as well as the likely number of repeated
exposures across days. While a
momentary exposure above the criteria
for Level B harassment counts as an
instance of take, that accounting does
not make any distinction between
fleeting exposures and more severe
encounters in which an animal may be
exposed to that received level of sound
for a longer period of time. Yet this
information is meaningful to an
understanding of the likely severity of
the exposure, which is relevant to the
negligible impact evaluation and not
directly incorporated into the risk
assessment framework described above.
For example, for bottlenose dolphins
exposed to noise from 3D WAZ surveys
in Zone 6, the modeling report shows
that approximately 72 takes (Level B
harassment) would be expected to occur
in a 24-hr period. However, each animat
modeled has a record or time history of
received levels of sound over the course
of the modeled 24-hr period. The 50th
percentile of the cumulative distribution
function indicates that the time spent
exposed to levels of sound above 160 dB
rms SPL (i.e., the 50 percent midpoint
for Level B harassment) would be only
TABLE 16—TIME IN MINUTES (PER DAY) SPENT ABOVE THRESHOLDS (50TH PERCENTILE) AND AVERAGE NUMBER OF
DAYS INDIVIDUALS TAKEN DURING 30-DAY SURVEY
Survey type and time (min/day) above
160 dB rms
(50% take)
Species
2D
Bryde’s whale ........................................................................
Sperm whale .........................................................................
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21.4
20.7
Survey type and time (min/day) above
140 dB rms
(10% take)
2D
3D NAZ
3D WAZ
163.5
31.8
55.4
10.7
61.7
12.0
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401.1
25.2
Average
number of
days ‘‘taken’’
during 30-day
survey
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2.4
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TABLE 16—TIME IN MINUTES (PER DAY) SPENT ABOVE THRESHOLDS (50TH PERCENTILE) AND AVERAGE NUMBER OF
DAYS INDIVIDUALS TAKEN DURING 30-DAY SURVEY—Continued
Survey type and time (min/day) above
160 dB rms
(50% take)
Species
2D
Kogia spp. .............................................................................
Beaked whale 1 .....................................................................
Rough-toothed dolphin ..........................................................
Bottlenose dolphin .................................................................
Clymene dolphin ...................................................................
Atlantic spotted dolphin .........................................................
Pantropical spotted dolphin ...................................................
Spinner dolphin .....................................................................
Striped dolphin ......................................................................
Fraser’s dolphin .....................................................................
Risso’s dolphin ......................................................................
Melon-headed whale .............................................................
Pygmy killer whale ................................................................
False killer whale ..................................................................
Killer whale ............................................................................
Short-finned pilot whale ........................................................
3.2
6.0
3.0
4.5
1.8
7.0
1.8
3.2
1.8
2.8
3.4
2.6
1.8
2.4
2.7
3.3
3D NAZ
3D WAZ
7.9
12.4
6.3
11.7
3.9
16.0
4.1
8.5
4.0
6.4
8.4
5.9
3.6
4.9
6.1
8.1
2.8
4.4
2.5
4.0
1.6
6.5
1.6
2.7
1.6
2.4
2.9
2.2
1.4
1.9
3.3
2.9
Coil
Survey type and time (min/day) above
140 dB rms
(10% take)
2D
15.3
24.0
11.4
16.8
8.7
25.7
8.7
16.4
8.5
13.8
15.3
13.1
7.1
9.3
12.0
17.5
3D NAZ
3D WAZ
19.0
39.7
27.6
54.6
21.1
58.1
21.0
31.0
21.0
24.2
37.7
24.2
18.5
22.0
46.1
27.4
6.7
14.1
10.2
19.7
7.2
20.9
7.1
10.8
7.2
8.4
12.2
8.3
6.6
8.0
14.9
9.8
7.6
16.2
11.2
22.0
8.0
23.4
8.1
12.4
8.0
9.4
13.8
9.3
7.3
8.8
16.8
10.9
Coil
13.9
31.1
20.9
53.2
20.4
49.3
22.2
22.8
21.3
24.0
31.5
24.0
17.3
17.8
73.6
20.8
Average
number of
days ‘‘taken’’
during 30-day
survey
3.1
9.9
3.5
3.5
3.5
3.5
3.5
3.5
3.5
3.5
3.5
3.4
3.4
3.4
3.4
3.4
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1 Beaked whales are evaluated according to a different scale where 90% of the population exposed above 140 dB rms is considered taken and 50% of the population exposed above 120 dB rms is considered taken.
Loss of Hearing Sensitivity
In general, NMFS expects that noiseinduced hearing loss, whether
temporary (temporary threshold shift,
equivalent to Level B harassment) or
permanent (PTS, the only form of Level
A harassment that may result from this
action), is only possible as a result of
airgun survey activity for low-frequency
and high-frequency cetaceans. The best
available scientific information
indicates that low-frequency cetacean
species (i.e., mysticete whales,
including the Bryde’s whale) have
heightened sensitivity to frequencies in
the range output by airguns, as shown
by their auditory weighting function,
whereas high-frequency cetacean
species (including Kogia spp.) have
heightened sensitivity to noise in
general (as shown by their lower
threshold for the onset of PTS) (NMFS,
2018). However, no instances of Level A
harassment are predicted to occur for
Bryde’s whales, and Level A harassment
of Bryde’s whales will not be authorized
under this rule.
Level A harassment is predicted to
occur for Kogia spp. (as indicated in
Table 9 and evaluated in the ‘‘Level A
harassment’’ subsection above).
However, the degree of injury (hearing
impairment) is expected to be mild. If
permanent hearing impairment occurs,
it is most likely that the affected animal
would lose a few dB in its hearing
sensitivity, which in most cases would
not be expected to affect its ability to
survive and reproduce. Hearing
impairment that occurs for these
individual animals would be limited to
at or slightly above the dominant
frequency of the noise sources. In
particular, the predicted PTS resulting
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from airgun exposure is not likely to
affect their echolocation performance or
communication, as Kogia spp. likely
produce acoustic signals at frequencies
above 100 kHz (Merkens et al., 2018),
well above the frequency range of airgun
noise. Further, modeled exceedance of
Level A harassment criteria typically
resulted from being near an individual
source once, rather than accumulating
energy from multiple sources. Overall,
the modeling indicated that exceeding
the SEL threshold is a rare event, and
having four vessels close to each other
(350 m between tracks) did not cause
appreciable accumulation of energy at
the ranges relevant for injury exposures.
Accumulation of energy from
independent surveys is expected to be
negligible. This is relevant for Kogia
spp. because based on their expected
sensitivity, we expect that aversion may
play a stronger role in avoiding
exposures above the peak pressure PTS
threshold than we have accounted for.
For both Bryde’s whales and Kogia
spp., some subset of the individual
marine mammals predicted to be taken
by Level B harassment may incur some
TTS in addition to being behaviorally
harassed. For Bryde’s whales, TTS is
more likely to occur at frequencies
important for communication. However,
any TTS incurred would be expected to
be of a relatively small degree and short
duration. This is due to the low
likelihood of sound source approaches
of the proximity or duration necessary
to cause more severe TTS, given the fact
that both sound source and marine
mammals are continuously moving, the
anticipated effectiveness of shutdowns,
and general avoidance by marine
mammals of louder sources.
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For these reasons, and in conjunction
with the required mitigation, NMFS
does not believe that Level A
harassment (here, PTS) or Level B
harassment in the form of TTS will play
a meaningful role in the overall degree
of impact experienced by marine
mammal populations as a result of the
projected survey activity. Further, the
impacts of any TTS incurred are
addressed along with behavioral
disruption through the broader analysis
of Level B harassment.
Impacts to Habitat
Potential impacts to marine mammal
habitat, including to marine mammal
prey, were discussed in detail in the
notice of proposed rulemaking and
summarized herein (see Potential Effects
of the Specified Activities on Marine
Mammals and Their Habitat as well as
responses to comments concerning
these issues).
Regarding impacts to prey species
such as fish and invertebrates, NMFS’
review of the available information
leads to a conclusion that the most
likely impact of survey activity would
be temporary avoidance of an area, with
a rapid return to pre-survey distribution
and behavior, and minimal impacts to
recruitment or survival anticipated.
Therefore, the specified activities are
not likely to have more than short-term
adverse effects on any prey habitat or
populations of prey species. Further,
any impacts to prey species are not
expected to result in significant or longterm consequences for individual
marine mammals, or to contribute to
adverse impacts on their populations.
Regarding potential impacts to
acoustic habitat, NMFS previously
summarized a detailed analysis of
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potential cumulative and chronic effects
to marine mammals (found in the CCE
report available online at
www.fisheries.noaa.gov/action/
incidental-take-authorization-oil-andgas-industry-geophysical-surveyactivity-gulf-mexico). That analysis
focused on potential effects to sperm
whales (which also provides a
conservative proxy regarding potential
effects to other mid- and high-frequency
cetacean species) and to Bryde’s whales.
Regarding sperm whales, the analysis
shows that the survey activities do not
significantly contribute to the
soundscape in the frequency band
relevant for their lower-frequency slowclicks, and that there will be no
significant change in communication
space for sperm whales. Similar
conclusions may be assumed for other
mid- and high-frequency cetacean
species.
Implications for acoustic masking and
reduced communication space resulting
from noise produced by airgun surveys
in the GOM are expected to be
particularly heightened for animals that
actively produce low-frequency sounds
or whose hearing is attuned to lower
frequencies (i.e., Bryde’s whales). The
strength of the communication space
approach used here is that it evaluates
potential contractions in the availability
of a signal of documented importance to
a population of animals of key
management interest in the region. In
this case, losses of communication
space for Bryde’s whales were estimated
to be higher in eastern and central GOM
canyons and shelf break areas. In
contrast, relative maintenance of
listening area and communication space
was seen within the Bryde’s whale core
habitat area in the eastern GOM. The
result was heavily influenced by the
projected lack of survey activity in that
region, which underscores the
importance of maintaining this
important habitat for the Bryde’s whale.
Following BOEM’s update to the scope
of activity considered herein, no survey
activity will occur under this rule
within Bryde’s whale core habitat, or
within the broader eastern GOM. In
areas where larger amounts of survey
activity were projected, significant loss
of low-frequency listening area and
communication space for Bryde’s whale
calls was estimated. However, these are
areas where Bryde’s whales are unlikely
to occur (i.e., deeper waters of the
central and western GOM).
Species and Stock-Specific Negligible
Impact Analysis Summaries
In this section, we consider the
relative impact ratings described above
in conjunction with the required
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mitigation and other relevant contextual
information in order to produce a final
assessment of impact to the stock or
species, i.e., the negligible impact
determinations. The effects of the DWH
oil spill are accounted for through the
vulnerability scoring (Table 12). NMFS
developed mitigation requirements for
consideration in the proposed rule,
including time-area restrictions,
designed specifically to provide benefit
to certain populations for which a
relatively high amount of risk is
predicted in relation to exposure to
survey noise. The required time-area
restrictions, described in detail in
Proposed Mitigation in the notice of
proposed rulemaking and depicted in
Figure 4, were designed specifically to
provide benefit to the bottlenose
dolphin, Bryde’s whale, and beaked and
sperm whales, with additional benefits
to Kogia spp., which are often found in
higher densities in the same locations of
greater abundance for beaked and sperm
whales. Two of the three time-area
restrictions in the proposed rule—the
Bryde’s whale core habitat area and the
Dry Tortugas area (Areas #2 and 3;
Figure 4)—are eliminated from
consideration as a result of BOEM’s
update to the geographic scope of
action, as these two areas are entirely
within the portion of the GOM removed
from consideration. The bottlenose
dolphin area, as revised herein (see
Mitigation), is included in this final
rule.
Although the Bryde’s whale core
habitat and Dry Tortugas areas are not
the subject of restrictions on survey
activity, as the updated scope of activity
considered here does not include those
two areas, the beneficial effect for
animals in those areas, and the stocks of
which they are a part, remains the same.
No survey activity in those areas can be
considered for LOAs issued under this
rule. In addition, we expect the lack of
survey activity in those areas to provide
some subsidiary benefit to additional
species that may be present, as
indicated in the sections below and
reflected in the updated take estimates.
The absence of survey activity in
those two areas benefits both the
primary species for which they were
designed and species that may benefit
secondarily by likely reducing the
portion of a stock likely exposed to
survey noise and avoiding impacts to
certain species in areas of importance
for them. These areas are discussed
more specifically in the context of the
species and stocks they were designed
to protect in the Proposed Mitigation
section of the notice of proposed
rulemaking, and are summarized in the
sections below.
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5433
Bryde’s Whale
First, we note that the estimated (and
allowable) take of Bryde’s whales has
been reduced as compared to the
proposed rule as a result of the change
in scope. Specifically, both the
maximum annual take and the average
annual take decreased by approximately
98 percent. The EWG analysis, which
evaluated the relative significance of the
aggregated impacts of the survey
activities across seven GOM zones in
the context of the vulnerability of each
species, concluded that the GOM-wide
risk ratings for Bryde’s whales are low,
regardless of activity scenario. We note
that, although the evaluated severity of
take for Bryde’s whales is very low in
all zones where take could occur,
vulnerability for the species is assessed
as high in all zones where the species
occurs. When integrated through the
risk framework as described above,
overall risk for the species is therefore
assessed as low for both the high and
moderate effort scenarios. Evaluated risk
is lower than what was considered in
the proposed rule, where analysis of the
prior take estimates resulted in a risk
rating of moderate for both scenarios.
We further consider the likely severity
of any predicted behavioral disruption
of Bryde’s whales in the context of the
likely duration of exposure above Level
B harassment thresholds. Specifically,
the average modeled time per day spent
at received levels above 160 dB rms
(where 50 percent of the exposed
population is considered taken) ranges
from 6.8–21.4 minutes for deep
penetration survey types. The average
time spent exposed to received levels
between 140 and 160 dB rms (where 10
percent of the exposed population is
considered taken) ranges from 55–164
minutes for 2D, 3D NAZ, and 3D WAZ
surveys, and 401 minutes for coil
surveys (which comprise approximately
10 percent of the total activity days).
Importantly, no survey activity will
occur within the Bryde’s whale core
habitat area pursuant to this rule. The
absence of survey activity in the area is
expected to benefit Bryde’s whales and
their habitat by minimizing a range of
potential effects of airgun noise, both
acute and chronic, that could otherwise
accrue to impact the reproduction or
survival of individuals in this area.
Absence of survey activity in this area
will minimize disturbance of the species
in the place most important to them for
critical behaviors such as foraging and
socialization. Based on Roberts et al.
(2016), the area encompasses
approximately 92 percent of the
predicted abundance of Bryde’s whales
in the GOM. Intensive survey effort in
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the region has not resulted in any
confirmed Bryde’s whale sightings
outside this core habitat area (aside from
a single anomalous sighting in the
western GOM). Although some sound
from airguns may still propagate into
the Bryde’s whale core habitat area from
surveys that may occur outside of the
area (in certain locations where
separation distance between the core
habitat area and the area considered for
survey activity through this rule is less;
see Figure 2), exposure of Bryde’s
whales to sound levels that may be
expected to result in Level B harassment
will be eliminated or reduced for
animals within the Bryde’s whale core
area. The absence of survey activity in
this area and significant reduction in
associated exposure of Bryde’s whales
to seismic airgun noise is expected to
eliminate the likelihood of auditory
injury of Bryde’s whales. Finally, the
absence of survey activity in the eastern
GOM will reduce chronic exposure of
Bryde’s whales to higher levels of
anthropogenic sound and the associated
effects including masking, disruption of
acoustic habitat, long-term changes in
behavior such as vocalization, and
stress.
As described in the preceding ‘‘Loss
of Hearing Sensitivity’’ section, we have
analyzed the likely impacts of potential
temporary hearing impairment and do
not expect that they would result in
impacts on reproduction or survival of
any individuals. The extended
shutdown zone for Bryde’s whales
(1,500 m)—to be implemented in the
unlikely event that a Bryde’s whale is
encountered outside of the core habitat
area—is expected to further minimize
the severity of any hearing impairment
incurred as well as reducing the
likelihood of more severe behavioral
responses. Similarly, application of this
extended distance shutdown
requirement when calves are present
will minimize the potential for and
degree of disturbance during this
sensitive life stage.
No mortality of Bryde’s whales is
anticipated or authorized. It is possible
that Bryde’s whale individuals in this
stock, if encountered in areas not
typically considered to be Bryde’s whale
habitat, will be impacted briefly on one
or more days during a year of activity
by one type of survey or another and
some subset of those exposures above
thresholds may be of comparatively long
duration within a day. However, the
significant and critical protection
afforded through the absence of survey
activity in the core habitat area and the
associated reduction in estimated take
ensures that the impacts of the expected
takes from these activities are not likely
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to adversely affect the GOM stock of
Bryde’s whales through impacts on
annual rates of recruitment or survival.
Sperm Whale
First, we note that the estimated (and
allowable) take of sperm whales has
been reduced as compared to the
proposed rule as a result of the change
in scope. Specifically, the maximum
annual take decreased by approximately
62 percent and the average annual take
decreased by approximately 58 percent.
The EWG analysis, which evaluated the
relative significance of the aggregated
impacts of the survey activities across
seven GOM zones in the context of the
vulnerability of each species, concluded
that the GOM-wide risk ratings for
sperm whales were between moderate
and low (equivalent to a 2.5 on a 5-point
scale, with a 3 equating to ‘‘moderate’’)
(for the high effort scenario) or low (for
the moderate effort scenario). Evaluated
risk is reduced from the proposed rule,
where the high effort scenario resulted
in a very high risk rating and the
moderate effort scenario resulted in a
high risk rating. We further consider the
likely severity of any predicted
behavioral disruption of sperm whales
in the context of the likely duration of
exposure above Level B harassment
thresholds. Specifically, the average
modeled time per day spent at received
levels above 160 dB rms (where 50
percent of the exposed population is
considered taken) ranges from 4–10.3
minutes for 2D, 3D NAZ, and 3D WAZ
surveys and up to 20.7 minutes for coil
surveys (which comprise less than 10
percent of the total projected activity
days) and the average time spent
between 140 and 160 dB rms (where 10
percent of the exposed population is
considered taken) is 12–31.8 minutes.
Odontocetes echolocate to find prey,
and while there are many different
strategies for hunting, one common
pattern, especially for deeper-diving
species, is to conduct multiple repeated
deep dives within a feeding bout, and
multiple bouts within a day, to find and
catch prey. While exposures of the short
durations noted above could potentially
interrupt a dive or cause an individual
to relocate to feed, such a short-duration
interruption would typically be unlikely
to have significant impacts on an
individual’s energy budget. However,
the moderate risk rating for the high
effort scenario reflects the higher
number of total days across which these
singularly more minor impacts may
occur, as well as other factors, and
points to the need for the consideration
of additional reduction of impacts
where possible. In years when less effort
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occurs, as represented by the moderate
effort scenario, risk will be less.
Importantly, no survey activity is
expected within the Dry Tortugas
Mitigation Area, which was analyzed
and proposed for implementation in the
proposed rule. The area provides
preferred habitat for comparatively high
densities of sperm whales and is
thought to be used as a calving area. The
absence of survey activity in the area is
expected to alleviate some of the
previous impacts of concern to sperm
whales (as well as beaked whales and
Kogia spp.) and their habitat by
minimizing a range of potential effects
of airgun noise, both acute and chronic,
that could otherwise accrue to impact
the reproduction or survival of
individuals in this area. Absence of
survey activity in this area will
minimize disturbance of the species in
a place of importance for critical
behaviors such as foraging and
socialization and, overall, helps to
reduce evaluated risk to the stock as a
whole.
Additionally, we note that the
extended distance shutdown zone for
sperm whales (1,500 m) is expected to
further reduce the likelihood and
minimize the severity of more severe
behavioral responses. Similarly,
application of this extended distance
shutdown requirement when calves are
present will minimize the potential for
and degree of disturbance during this
sensitive life stage.
No mortality or Level A harassment of
sperm whales is anticipated or
authorized. While it is likely that the
majority of the individual sperm whales
will be impacted briefly on one or more
days during a year of activity by one
type of survey or another, based on the
nature of the individual exposures
(shorter duration) and takes, as well as
the aggregated scale of the impacts
across the GOM in consideration of the
mitigation discussed here, the impacts
of the expected takes from these
activities are not likely to adversely
affect the GOM stock of sperm whales
through adverse impacts on annual rates
of recruitment or survival.
Beaked Whales
In consideration of the similarities in
the nature and scale of impacts, we
consider the GOM stocks of Cuvier’s,
Gervais’, and Blainville’s beaked whales
together in this section. First, we note
that the estimated (and allowable) take
of beaked whales has been reduced as
compared to the proposed rule as a
result of the change in scope.
Specifically, the maximum annual take
decreased by approximately 19 percent
and the average annual take decreased
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by approximately 15 percent. The EWG
analysis, which evaluated the relative
significance of the aggregated impacts of
the survey activities across seven GOM
zones in the context of the vulnerability
of each species, concluded that the
GOM-wide risk ratings for beaked
whales were between high and
moderate (equivalent to a 3.5 on a 5point scale, with a 4 equating to ‘‘high’’)
for the high effort scenario and between
moderate and low (equivalent to a 2.5
on a 5-point scale, with a 3 equating to
‘‘moderate’’) for the moderate effort
scenario. Evaluated risk is reduced from
the proposed rule, where the high effort
scenario resulted in a very high risk
rating and the moderate effort scenario
resulted in a high risk rating. We further
consider the likely severity of any
predicted behavioral disruption of
beaked whales in the context of the
likely duration of exposure above Level
B harassment thresholds. Beaked whales
are considered more behaviorally
sensitive to sound than most other
species, and therefore we utilize
different thresholds to predict
behavioral disturbance. However, this
means that beaked whales are evaluated
as ‘‘taken’’ upon exposure to received
sound levels as low as 120 dB (where 50
percent of the exposed beaked whale
population is considered taken). These
received levels are typically reached at
extreme distance from the acoustic
source (i.e., greater than 50 km from the
source). Behavioral responses to noise
are significantly correlated with
distance from the source (e.g., Gomez et
al., 2016); and potential responses to
these relatively low received levels at
such great distances, while
conservatively evaluated here as take
under the MMPA, are unlikely to result
in any response of such a severity as to
carry any cost to the animal.
(Additionally, in certain circumstances,
noise from the surveys at these
distances may be indistinguishable from
other low-frequency background noise).
Therefore, as for other species, we
consider only the average modeled time
per day spent at received levels above
140 dB rms (where 90 percent of the
exposed beaked whale populations are
considered taken) and 160 dB rms
(where, potentially, all exposed beaked
whales are taken). The average time
spent in a state of exposure above 160
dB rms is only 6–12.4 minutes for 2D,
3D NAZ, and 3D WAZ surveys and 24
minutes for coil surveys. The average
time spent in a state of exposure above
140 dB rms is 14.1 minutes for 3D WAZ
surveys, 16.2 minutes for 2D surveys,
31.1 minutes for coil surveys, and 39.7
minutes for 3D NAZ surveys.
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Odontocetes echolocate to find prey,
and while there are many different
strategies for hunting, one common
pattern, especially for deeper-diving
species, is to conduct multiple repeated
deep dives within a feeding bout, and
multiple bouts within a day, to find and
catch prey. As we noted, while some of
the exposures of the durations noted
above could interrupt a dive or cause an
individual to relocate to feed because of
the lower thresholds combined with the
way exposures are distributed across
received levels, a higher proportion of
the total takes (as compared to other
taxa) are at the lower end of the received
levels at which take would be expected
to occur and at great distance from the
acoustic source, where responses (if
any) should be assumed to be minor. All
else being equal, exposures to lower
received levels and, separately, at
greater distances might be expected to
result in less severe responses, even
given longer durations (e.g., DeRuiter et
al., 2013). Considered individually or
infrequently, these sorts of feeding
interruptions would be unlikely to have
significant impacts on an individual’s
energy budget, especially given the
likely availability of adequate alternate
feeding areas relatively nearby.
However, the high risk rating for the
high effort scenario reflects the higher
number of total days across which these
singularly more minor impacts may
occur, as well as other factors, and
points to the need for the consideration
of additional reduction of impacts
where possible. In years when less effort
occurs, as represented by the moderate
effort scenario, risk will be less.
Importantly, no survey activity is
expected within the Dry Tortugas
Mitigation Area, which was analyzed
and proposed for implementation in the
proposed rule. The area provides
preferred habitat for comparatively high
densities of beaked whales. The absence
of survey activity in this important area
is expected to alleviate some of the
previous impacts of concern to beaked
whales (as well as sperm whales and
Kogia spp.) and their habitat by
minimizing a range of potential effects
of airgun noise, both acute and chronic,
that could otherwise accrue to impact
the reproduction or survival of
individuals in this area. Absence of
survey activity in this area will
minimize disturbance of the species in
a place of importance for critical
behaviors such as foraging and
socialization and, overall, helps to
reduce evaluated risk to the stocks as a
whole.
Additionally, we note that the
extended distance shutdown zone for
beaked whales (1,500 m) is expected to
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5435
further reduce the likelihood of, and
minimize the severity of, more severe
behavioral responses.
Despite the nature and duration of the
exposures anticipated, which at a
smaller scale might not be expected to
meaningfully impact individual fitness,
given the high to moderate EWG risk
rating and the relatively high number of
predicted beaked whale takes
(increasing the likelihood of some
subset of individuals accruing a fair
number of repeated takes over
sequential days—albeit assuming takes
at low received levels and at distances
from the source where responses, if any,
should be expected to be minor), it is
more likely that a small number of
individuals could be interrupted during
foraging in a manner and amount such
that impacts to the energy budgets of
females (from either losing feeding
opportunities or expending energy to
find alternative feeding options) could
cause them to forego reproduction for a
year. Energetic impacts to males are
generally meaningless to population
rates unless they cause death, and
extreme energy deficits (beyond what
could be considered reasonably likely to
result from these activities) are required
to cause the death of an adult marine
mammal. As noted previously, however,
foregone reproduction (especially for
one year, which is the maximum
predicted because the relatively small
number anticipated in any one year
makes the probability that any
individual would be impacted in this
way twice in five years very low) has far
less of an impact on population rates
than mortality. And a small number of
instances of foregone reproduction
would not be expected to adversely
affect these stocks through effects on
annual rates of recruitment or survival.
It is worth noting that in similar
situations, i.e., where individual beaked
whales may be exposed to noise above
harassment thresholds regularly,
populations appear to be stable based on
multiple studies and lines of evidence
(e.g., Falcone and Schorr, 2014;
DiMarzio et al., 2018). In research done
at the Navy’s fixed tracking range in the
Bahamas, animals were observed to
leave the immediate area of an antisubmarine warfare training exercise but
return within a few days after the event
ended (Claridge and Durban, 2009;
McCarthy et al., 2011; Moretti et al.,
2009, 2010; Tyack et al., 2010, 2011). It
is important to note that in these
contexts, beaked whales were exposed
to noise stimuli to which they are
significantly more acoustically sensitive
(i.e., mid-frequency active sonar versus
low-frequency airgun noise).
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Of note, due to their pelagic
distribution, typical high availability
bias due to deep-diving behavior and
cryptic nature when at the surface,
beaked whales are rarely sighted during
at-sea surveys and difficult to
distinguish between species when
visually observed in the field.
Accordingly, abundance estimates in
NMFS SARs are recorded for
Mesoplodon spp. Available sightings
data, including often unresolved
sightings of beaked whales, must be
combined in order to develop habitatbased density models for beaked
whales, as were used to inform our
acoustic exposure modeling effort.
Therefore, density and take estimates in
this rule are similarly lumped for the
three species of beaked whales, and
there is no additional information by
which NMFS could appropriately
apportion impacts other than equally/
proportionally across the three species.
No mortality or Level A harassment of
any of these three species of beaked
whales is anticipated or authorized. It is
likely that the majority of the individual
beaked whales will be impacted on one
or more days during a year of activity
by one type of survey or another. It is
possible that some small number of
female beaked whales may experience a
year of foregone reproduction. However,
based on the nature of the majority of
the individual exposures and the overall
scale of the aggregate impacts and risk
rating in consideration of the mitigation
discussed here, and noting the
continued presence of beaked whales in
the GOM given the many years of high
activity levels and the evidence that
beaked whales maintain stable or
increasing populations in other areas
with high levels of acoustic activity, the
impacts of the expected takes from these
activities are not likely to adversely
affect the GOM stocks of Cuvier’s,
Gervais’, or Blainville’s beaked whales
through adverse impacts on annual rates
of recruitment or survival.
Kogia spp.
First, we note that the estimated (and
allowable) take of Kogia spp. has been
reduced as compared to the proposed
rule as a result of the change in scope.
Specifically, the maximum annual take
by Level B harassment decreased by
approximately 46 percent and the
average annual take decreased by
approximately 43 percent. (These
reductions are 49 and 46 percent,
respectively, for Level A harassment.)
The EWG analysis, which evaluated the
relative significance of the aggregated
impacts of the survey activities across
seven GOM zones in the context of the
vulnerability of each species, concluded
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that the GOM-wide risk ratings for Kogia
spp. were low (for the high effort
scenario) and very low (for the moderate
effort scenario). Evaluated risk is
reduced from the proposed rule, where
the high effort scenario resulted in a
moderate risk rating and the moderate
effort scenario resulted in a low risk
rating. We further consider the likely
severity of any predicted behavioral
disruption of Kogia spp. in the context
of the likely duration of exposure above
Level B harassment thresholds.
Specifically, the average modeled time
per day spent at received levels above
160 dB rms (where 50 percent of the
exposed population is considered taken)
ranges from 2.8–7.9 minutes for 2D, 3D
NAZ, and 3D WAZ surveys and up to
15.3 minutes for coil surveys (which
comprise less than 10 percent of the
total projected activity days), and the
average time spent between 140 and 160
dB rms (where 10 percent of the
exposed population is considered taken)
is 6.7–19 minutes.
Odontocetes echolocate to find prey,
and while there are many different
strategies for hunting, one common
pattern, especially for deeper diving
species, is to conduct multiple repeated
deep dives within a feeding bout, and
multiple bouts within a day, to find and
catch prey. While exposures of the short
durations noted above could potentially
interrupt a dive or cause an individual
to relocate to feed, such a short-duration
interruption would be unlikely to have
significant impacts on an individual’s
energy budget and, further, for these
species and this open-ocean area, there
are no specific known reasons (i.e.,
these species range GOM-wide beyond
the continental slope and there are no
known biologically important areas) to
expect that there would not be adequate
alternate feeding areas relatively nearby,
especially considering the anticipated
absence of survey activity in the eastern
GOM.
As described above, no survey activity
is expected within the Dry Tortugas
Mitigation Area, which was analyzed
and proposed for implementation in the
proposed rule. The absence of survey
activity in the area is expected to afford
additional reduction of impacts to Kogia
spp., in addition to sperm and beaked
whales, given their relatively high
density in that area. Importantly, the
absence of survey activity in the area
will reduce disturbance of these species
in places of importance to them for
critical behaviors such as foraging and
socialization and, overall, help to
reduce evaluated risk to the stocks as a
whole.
NMFS has analyzed the likely impacts
of potential hearing impairment,
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including the estimated upper bounds
of permanent threshold shift (Level A
harassment) that could be authorized
under the rule, and do not expect that
they would result in impacts on
reproduction or survival of any
individuals. As described in the
previous section, the degree of injury for
individuals would be expected to be
mild, and the predicted PTS resulting
from airgun exposure is not likely to
affect echolocation performance or
communication for Kogia spp.
Additionally, the extended distance
shutdown zone for Kogia spp. (1,500 m)
is expected to further minimize the
severity of any hearing impairment
incurred and also to further reduce the
likelihood of, and minimize the severity
of, more severe behavioral responses.
Of note, due to their pelagic
distribution, small size, and cryptic
behavior, pygmy sperm whales and
dwarf sperm whales are rarely sighted
during at-sea surveys and difficult to
distinguish between when visually
observed in the field. Accordingly,
abundance estimates in NMFS SARs are
recorded for Kogia spp. only, density
and take estimates in this rule are
similarly lumped for the two species,
and there is no additional information
by which NMFS could appropriately
apportion impacts other than equally/
proportionally across the two species.
No mortality of Kogia spp. is
anticipated or authorized. While it is
likely that the majority of the
individuals of these two species will be
impacted briefly on one or more days
during a year of activity by one type of
survey or another, based on the nature
of the individual exposures and takes,
as well as the aggregated scale of the
impacts across the GOM, and in
consideration of the mitigation
discussed here, the impacts of the
expected takes from these activities are
not likely to adversely impact the GOM
stocks of dwarf or pygmy sperm whales
through adverse impacts on annual rates
of recruitment or survival.
Bottlenose Dolphins
The change in scope did not result in
any appreciable change to estimated
(and allowable) take of bottlenose
dolphins compared to the proposed
rule. Specifically, the maximum annual
take increased slightly (by
approximately 2 percent), while the
average annual take decreased slightly
(by approximately 1 percent). The EWG
analysis, which evaluated the relative
significance of the aggregated impacts of
the survey activities across seven GOM
zones in the context of the vulnerability
of each species, concluded that the
GOM-wide risk ratings for both oceanic
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bottlenose dolphins and coastal/shelf
bottlenose dolphins are very low for
both scenarios. In the proposed rule,
risk was evaluated for bottlenose
dolphins GOM-wide (here we have
refined the risk evaluation to
differentiate between oceanic and
coastal/shelf stocks). Evaluated risk is
reduced from the proposed rule, where
the high effort scenario resulted in a low
risk rating and the moderate effort
scenario resulted in a moderate risk
rating. We further considered the likely
severity of any predicted behavioral
disruption of bottlenose dolphins in the
context of the likely duration of
exposure above Level B harassment
thresholds. Specifically, the average
modeled time per day spent at received
levels above 160 dB rms (where 50
percent of the exposed population is
considered taken) ranges from 4–11.7
minutes for 2D, 3D NAZ, and 3D WAZ
surveys and up to 16.8 minutes for coil
surveys (which comprise less than 10
percent of the total projected activity
days) and the average time spent
between 140 and 160 dB rms is 19.7–
54.6 minutes. While exposures of the
short durations noted above could
potentially interrupt a dive or cause an
individual to relocate to feed, among
other impacts, such a short-duration
interruption would be unlikely to have
significant impacts on an individual’s
energy budget or otherwise impact
reproduction or survival.
As described earlier in this preamble,
the northern coastal stock of bottlenose
dolphin was particularly severely
impacted by the DWH oil spill, and was
additionally affected by a recent UME.
Importantly, as described in Mitigation,
NMFS is requiring a seasonal time-area
restriction on airgun survey activity
within the coastal waters where this
stock is likely to be found. The closure
area is expected to protect coastal
bottlenose dolphins and their habitat
through the alleviation or minimization
of a range of potential effects of airgun
noise, both acute and chronic, that
could otherwise accrue to impact the
reproduction or survival of individuals
in this area. The timing of the restriction
provides protection during the times of
year thought to be most important for
bottlenose dolphin calving and nursing
of young. Although some sound from
airguns may still propagate into the area
from surveys that may occur outside of
the area, exposure of bottlenose
dolphins to sound levels that would
result in Level B harassment will be
alleviated or reduced for animals within
the closure area. Any exposure to noise
that may increase stress levels and
exacerbate health problems in
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bottlenose dolphins still recovering
from the effects of the DWH spill will
be minimized during this important
reproductive period. This important
mitigation results in a reduction in the
scale of aggregate effects (which, among
other things, suggests the comparative
number of days across which individual
bottlenose dolphins might be taken
within a year) and associated risk
assessment.
Of note, bottlenose dolphins cannot
be identified to stock when visually
observed in the field. Abundance
estimates in NMFS SARs are based
strictly on the location where animals
are observed, and available sightings
data must be combined in order to
develop habitat-based density models
for bottlenose dolphins, as were used to
inform our acoustic exposure modeling
effort. Therefore, density and take
estimates in this rule are provided for
bottlenose dolphins as a GOM-wide
species. However, based on NMFS’
stock delineations, we can reasonably
assume that dolphins occurring within
Zones 4–7 would be from the oceanic
stock, while dolphins occurring within
Zones 1–3 would be from the shelf stock
and/or coastal stocks. Therefore, for the
oceanic stock, we are able to draw stockspecific conclusions in this analysis. For
coastal/shelf stocks, there is no
additional information by which NMFS
could appropriately apportion impacts
other than equally/proportionally across
the stocks, with the exception of
predicting reduced impacts to the
northern coastal stock as described
above. We note that, as a result of
BOEM’s update to the scope of activity,
the eastern coastal stock will not
experience any impacts and is
accordingly no longer considered in this
rule.
No mortality or Level A harassment of
bottlenose dolphins is anticipated or
authorized. While it is likely that the
majority of individual dolphins may be
impacted briefly on one or more days
during a year of activity by one type of
survey or another, based on the nature
of the individual exposures (shorter
duration) and takes, as well as the
aggregated scale of the impacts across
the GOM in consideration of the
mitigation discussed here, the impacts
of the expected takes from these
activities are not likely to adversely
affect any affected GOM stock of
bottlenose dolphins through adverse
impacts on annual rates of recruitment
or survival.
All Other Stocks
In consideration of the similarities in
the nature and scale of impacts, we
consider the GOM stocks of the
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5437
following species together in this
section: Rough-toothed dolphin,
Clymene dolphin, Atlantic spotted
dolphin, pantropical spotted dolphin,
striped dolphin, spinner dolphin,
Fraser’s dolphin, Risso’s dolphin,
melon-headed whale, pygmy killer
whale, false killer whale, killer whale,
and short-finned pilot whale. Estimated
(and allowable) take of these stocks
(including both the maximum annual
take and the average annual take) has
been reduced as compared to the
proposed rule as a result of the change
in scope (with the exception of the
Atlantic spotted dolphin). For the
Atlantic spotted dolphin, the change in
scope resulted in increases compared to
the proposed rule. Specifically, the
maximum annual take increased by
approximately 9 percent, while the
average annual take increased by
approximately 4 percent. These slight
increases do not impact our analysis for
the stock.
The EWG analysis, which evaluated
the relative significance of the
aggregated impacts of the survey
activities across seven GOM zones in
the context of the vulnerability of each
species, concluded that the GOM-wide
risk ratings for high and moderate effort
scenarios ranged from very low to low
for these species. For all stocks, there
was a trend of decreased or static risk
ratings compared to the proposed rule,
where the GOM-wide risk ratings for
high and moderate effort scenarios
ranged from low to moderate.
We further considered the likely
severity of any predicted behavioral
disruption of the individuals of these
species in the context of the likely
duration of exposure above Level B
harassment thresholds. Specifically, the
average modeled time per day spent at
received levels above 160 dB rms
(where 50 percent of the exposed
population is considered taken) ranges
from 1.4–11.7 minutes for 2D, 3D NAZ,
and 3D WAZ surveys and up to 25.7
minutes for coil surveys (which
comprise less than 10 percent of the
total projected activity days). The
average time per day spent between 140
and 160 dB rms for individuals that are
taken is from 8–58.1 minutes, with the
one exception of killer whales exposed
to noise from coil surveys, which
average 73.6 minutes (though we note
that the overall risk rating for the
species is very low).
Odontocetes echolocate to find prey,
and there are many different strategies
for hunting. One common pattern for
deeper-diving species is to conduct
multiple repeated deep dives within a
feeding bout, and multiple bouts within
a day, to find and catch prey. While
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exposures of the shorter durations noted
above could potentially interrupt a dive
or cause an individual to relocate to
feed, such a short-duration interruption
would be unlikely to have significant
impacts on an individual’s energy
budget and, further, for these species
and this open-ocean area, there are no
specific known reasons (i.e., these
species range GOM-wide beyond the
continental slope and there are no
known biologically important areas) to
expect that there would not be adequate
alternate feeding areas relatively nearby,
especially considering the anticipated
absence of survey activity in the eastern
GOM. For those species that are more
shallow feeding species, it is unlikely
that the noise exposure considered
herein would result in minimal
significant disruption of foraging
behavior and, therefore, the concomitant
energetic effects would similarly be
minimal.
Of note, the Atlantic spotted dolphin
would benefit (via lessening of both
number and severity of takes) from the
coastal waters time-area restriction
developed to benefit bottlenose
dolphins and several additional species
experience notably reduced effects from
the absence of survey activity in
important eastern GOM habitat.
Specifically, multiple shelf-break
associated and pelagic species (such as
Risso’s dolphin, melon-headed whales,
and rough-toothed dolphins) experience
a reduction estimated take from the
absence of survey activity in both the
Bryde’s whale core habitat and Dry
Tortugas Areas. Maximum annual and
average annual take decreased for these
species compared with the proposed
rule by 20 and 14 percent, 19 and 15
percent, and 19 and 18 percent,
respectively. Numerous other species
would be expected to be present in
varying numbers at various times.
No mortality or Level A harassment of
these species is anticipated or
authorized. It is likely that the majority
of the individuals of these 13 species
will be impacted briefly on one or more
days during a year of activity by one
type of survey or another. Based on the
nature of the individual exposures and
takes, as well as the very low to low
aggregated scale of the impacts across
the GOM and considering the mitigation
discussed here, the impacts of the
expected takes from these activities are
not likely to adversely impact the GOM
stocks of any of these 13 GOM stocks of
these species through adverse impacts
on annual rates of recruitment or
survival.
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Determination
Based on the analysis contained
herein of the likely effects of the
specified activities on marine mammals
and their habitat, and taking into
consideration the implementation of the
monitoring and mitigation measures,
NMFS finds that the total marine
mammal take from the specified
activities will have a negligible impact
on all affected marine mammal species
and stocks.
Small Numbers
The sections below provide an
explanation of how NMFS interprets
and applies the small numbers standard
and remain substantively unchanged
from the discussion provided in the
notice of proposed rulemaking.
Additional discussion appears in
Comments and Responses to address
specific comments, questions, or
recommendations received from the
public.
What are small numbers?
The term ‘‘small numbers’’ appears in
section 101(a)(5)(A) of the MMPA as
follows:
(5)(A)(i) Upon request therefor by
citizens of the United States who engage
in a specified activity (other than
commercial fishing) within a specified
geographical region, the Secretary shall
allow, during periods of not more than
five consecutive years each, the
incidental, but not intentional, taking by
citizens while engaging in that activity
within that region of small numbers of
marine mammals of a species or
population stock if the Secretary, after
notice (in the Federal Register and in
newspapers of general circulation, and
through appropriate electronic media, in
the coastal areas that may be affected by
such activity) and opportunity for
public comment—
(I) finds that the total of such taking
during each five-year (or less) period
concerned will have a negligible impact
on such species or stock and will not
have an unmitigable adverse impact on
the availability of such species or stock
for taking for subsistence uses [ . . . ]
and
(II) prescribes regulations setting
forth—
(aa) permissible methods of taking
pursuant to such activity, and other
means of effecting the least practicable
adverse impact on such species or stock
and its habitat, paying particular
attention to rookeries, mating grounds,
and areas of similar significance, and on
the availability of such species or stock
for subsistence uses; and
(bb) requirements pertaining to the
monitoring and reporting of such taking.
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(Emphasis added.)
In addition to section 101(a)(5)(A), the
MMPA as amended in 1994 includes a
similar provision in section 101(a)(5)(D),
which provides for the issuance of
incidental take authorizations for small
numbers of marine mammals without
the need for regulations, effective for up
to one year, where the taking is limited
to harassment:
(5)(D)(i) Upon request therefor by
citizens of the United States who engage
in a specified activity (other than
commercial fishing) within a specific
geographic region, the Secretary shall
authorize, for periods of not more than
1 year, subject to such conditions as the
Secretary may specify, the incidental,
but not intentional, taking by
harassment of small numbers of marine
mammals of a species or population
stock by such citizens while engaging in
that activity within that region if the
Secretary finds that such harassment
during each period concerned—
(I) will have a negligible impact on
such species or stock, and
(II) will not have an unmitigable
adverse impact on the availability of
such species or stock for taking for
subsistence uses[.]
(Emphasis added.)
The MMPA does not define ‘‘small
numbers.’’ NMFS’ and the U.S. Fish and
Wildlife Service’s 1989 implementing
regulations defined small numbers as a
portion of a marine mammal species or
stock whose taking would have a
negligible impact on that species or
stock. This definition was invalidated in
Natural Resources Defense Council v.
Evans, 279 F.Supp.2d 1129 (2003) (N.D.
Cal. 2003), based on the court’s
determination that the regulatory
definition of small numbers was
improperly conflated with the
regulatory definition of ‘‘negligible
impact,’’ which rendered the small
numbers standard superfluous. As the
court observed, ‘‘the plain language
indicates that small numbers is a
separate requirement from negligible
impact.’’ Since that time, NMFS has not
applied the definition found in its
regulations. Rather, consistent with
Congress’ pronouncement that small
numbers is not a concept that can be
expressed in absolute terms (House
Committee on Merchant Marine and
Fisheries Report No. 97–228 (September
16, 1981)), NMFS makes its small
numbers findings based on an analysis
of whether the number of individuals
authorized to be taken annually from a
specified activity is small relative to the
stock or population size. The Ninth
Circuit has upheld a similar approach.
See Center for Biological Diversity v.
Salazar, 695 F.3d 893 (9th Cir. 2012).
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However, NMFS has not historically
indicated what the agency believes to be
the upper limit of small numbers.
To maintain an interpretation of small
numbers as a proportion of a species or
stock that does not conflate with
negligible impact, NMFS uses a simple
approach that establishes equal bins
corresponding to small, medium, and
large proportions of the population
abundance. NMFS then compares the
number of individuals estimated and
authorized to be taken against the best
available abundance estimate for that
species or stock.
It can be challenging to predict the
numbers of individual marine mammals
that will be taken by an activity. Many
models calculate instances of take but
are unable to account for repeated
exposures of individual marine
mammals, though the instances of take
necessarily represent the upper bound
of the number of individuals. In some of
those cases, such as for this rule (see
Estimated Take), we are able to generate
a more refined estimate of the numbers
of individuals predicted to be taken
utilizing a combination of quantitative
tools and qualitative information. When
an acceptable estimate of the individual
marine mammals taken is available,20
the small numbers determination is
based directly upon whether these
estimates exceed one-third of the stock
abundance. In other words, consistent
with past practice, when the estimated
number of individual animals taken
(which may or may not be assumed as
equal to the total number of takes,
depending on the available information)
is up to, but not greater than, one-third
of the most appropriate species or stock
abundance, NMFS will determine that
the numbers of marine mammals taken
of a species or stock are small.
Another circumstance in which
NMFS considers it appropriate to make
a small numbers finding is in the case
of a species or stock that may
potentially be taken but is either rarely
encountered or only expected to be
taken on rare occasions. In that
circumstance, one or two assumed
encounters with a group of animals
(meaning a group that is traveling
together or aggregated, and thus exposed
to a stressor at the same approximate
time) should reasonably be considered
small numbers, regardless of
consideration of the proportion of the
20 We note that although NMFS’ implementing
regulations require applications for incidental take
to include an estimate of the marine mammals to
be taken, there is nothing in section 101(a)(5)(A) (or
(D)) that requires NMFS to quantify or estimate
numbers of marine mammals to be taken for
purposes of evaluating whether the number is
small. (See CBD v. Salazar.)
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stock, as infrequent or rare encounters
resulting in take of one or two groups
should be considered small relative to
the range and distribution of any stock.
In summary, when quantitative take
estimates of individual marine
mammals are available or inferable
through consideration of additional
factors, and the number of animals
taken is one-third or less of the best
available abundance estimate for the
species or stock, NMFS considers it to
be of small numbers. NMFS may also
appropriately find that one or two
predicted group encounters will result
in small numbers of take relative to the
range and distribution of a species,
regardless of the estimated proportion of
the abundance.
Is the small numbers standard
evaluated based on total take under
incidental take regulations or within the
context of an individual letter of
authorization?
Neither the MMPA nor NMFS’
implementing regulations address
whether the small numbers
determination should be based upon the
total annual taking for (1) all activities
occurring under specific incidental take
regulation or (2) to individual LOAs
issued thereunder. The MMPA does not
define small numbers or explain how to
apply the term in either paragraph (A)
or (D) of section 101(a)(5), including
how to apply the term in a way that
allows for consistency between those
two very similar provisions in the
statute. Whether to apply the small
numbers finding to each individual
LOA under regulations that cover
multiple concurrent LOA holders is a
matter of first impression for NMFS.
Specifically, section 101(a)(5)(A)(i)(I)
explicitly states that the negligible
impact determination for a specified
activity must take into account the total
taking over the five-year period, but the
small numbers language is not tied
explicitly to the same language. Rather,
the small numbers provision appears in
section 101(a)(5)(A)(i) as a limitation on
what the Secretary may allow. The
regulatory vehicle for authorizing (i.e.,
‘‘allowing’’) the take of marine
mammals is the LOA.
Given NMFS’ discretion in light of the
ambiguities in the statute regarding how
to apply the small numbers standard,
we have determined that the small
numbers finding should be applied to
the annual take authorized per
individual LOA, rather than to the total
annual taking for all activities
potentially occurring under the
incidental take regulations. This perLOA approach harmonizes section
101(a)(5)(A) with the per-IHA
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5439
application in section 101(a)(5)(D) of the
MMPA.21 This per-LOA approach is not
only permissible but also preferable to
the total annual taking approach
because NMFS’ per-LOA approach to
small numbers in section 101(a)(5)(A)
affords greater regulatory flexibility to
utilize section 101(a)(5)(A) when there
are benefits to doing so for the resource
(marine mammals), the public,
prospective applicants, and
administrative efficiency:
• From a resource protection
standpoint, it is better to conduct a
comprehensive negligible impact
analysis that considers all of the
activities covered under the rule (versus
considering them independently
pursuant to individual IHAs) and
ensures that the total combined taking
from those activities will have a
negligible impact on the affected marine
mammal species or stocks and no
unmitigable adverse impact on
subsistence uses. Furthermore,
mitigation and monitoring are more
effective when considered across all
activity and years covered under
regulations.
• From an agency resource
standpoint, it ultimately will save
significant time and effort to cover
multi-year activities under a rule
instead of multiple incidental
harassment authorizations (IHAs).
While regulations require more analysis
up front, additional public comment
and internal review, and additional time
to promulgate compared to a single IHA,
they are effective for up to five years (for
non-military readiness activities) and
can cover multiple actors within a year.
The process of issuing individual LOAs
under incidental take regulations
utilizes the analysis, public comment,
and review that was conducted for the
regulations, and takes significantly less
time than it takes to issue independent
IHAs.
• From an applicant standpoint,
incidental take regulations offer more
regulatory certainty than IHAs (five
years versus one year) and significant
cost savings, both in time and
environmental compliance analysis and
documentation. This is especially true
for situations like here, where multiple
applicants will be applying for
individual LOAs under regulations. In
the case of this rule, the certainty
afforded by the promulgation of a
regulatory framework (e.g., by using
previously established take estimates,
mitigation and monitoring
21 As the court observed in Native Village of
Chickaloon v. NMFS, 947 F. Supp. 2d 1031, 1049
n.123 (D. Alaska 2013) ‘‘the same statutory
standards apply’’ to incidental take authorization
under both provisions.
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requirements, and procedures for
requesting and obtaining an LOA) is a
significant benefit for prospective
applicants.
NMFS’ evaluation of past IHAs
suggests that bundling together the
activities covered by two or three IHAs
that might be ideal subjects for a
combined incidental take regulation
(e.g., for ongoing maintenance
construction activities, or seismic
surveys in the Arctic by different
entities) may exceed the taking of small
numbers of a species if NMFS were to
apply the small numbers standard
across all taking contemplated by the
regulation in a year. In other words, if
the small numbers standard is applied
to the total annual taking under a rule,
NMFS may not be able to make the
necessary small numbers finding, which
would preclude the use of section
101(a)(5)(A) for multiple activities,
thereby eliminating the opportunity to
derive the resource and streamlining
benefits outlined above. Also,
application of the small numbers
standard across the total annual taking
covered by an incidental take
regulation, inasmuch as prospective
applicants can see that the total annual
take may exceed one-third of species or
stock abundance, would create an
incentive for applicants to pursue
individual IHAs (again, precluding the
ability to gain the benefits outlined
above).
Our conclusion is that NMFS can
appropriately elect to make a ‘‘small
numbers’’ finding based on the
estimated annual take in individual
LOAs issued under the rule. This
approach does not affect the negligible
impact analysis for a rule, which is the
biologically relevant inquiry and based
on the total annual estimated taking for
all activities the regulations will govern.
Making the small numbers finding
based on the estimated annual take in
individual LOAs allows NMFS to take
advantage of the associated
administrative and environmental
benefits of utilizing section 101(a)(5)(A)
that would be precluded in many cases
if small numbers were required to be
applied to the total annual taking under
the regulations. NMFS finds this
method of making a small numbers
determination to be a permissible
interpretation of the relevant MMPA
provisions.
Although this application of small
numbers may be argued as being less
protective of marine mammals, NMFS
disagrees. As noted previously, the
small numbers standard has less
biological significance as compared to
the substantive and contextuallyspecific analysis necessary to support
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the negligible impact determination.
The negligible impact determination is
still controlling, and the maximum total
annual taking that may be authorized
across all LOAs under an incidental take
regulation still could not exceed the
overall amount analyzed for the
negligible impact determination. Thus,
under this option, the negligible impact
analysis for the rulemaking still would
have to be conducted for the time period
explicitly specified in the statute (i.e.,
up to five years), but the small numbers
analysis would attach to the instrument
itself that authorizes the taking, i.e., the
LOA.
How will small numbers be evaluated
under this GOM rule?
In this rule, up-to-date species
information is available, and
sophisticated models have been used to
estimate take in a manner that will
allow for quantitative comparison of the
take of individuals versus the best
available abundance estimates for the
species or stocks. Specifically, while the
modeling effort utilized in the rule
enumerates the estimated instances of
takes that will occur across days as the
result of the operation of certain survey
types in certain areas, the modeling
report also includes the evaluation of a
test scenario that allows for a reasonable
modification of those generalized take
estimates to better estimate the number
of individuals that will be taken within
one survey. LOA applicants using
modeling results from the rule to inform
their applications will be able to
reasonably estimate the number of
marine mammal individuals taken by
their activities. LOA applications that
do not use the modeling provided in the
rule to estimate take for their activities
will need to be reviewed, and applicants
will be required to ensure that their
estimates adequately inform the small
numbers finding. If applicants use the
modeling provided by this rule to
estimate take, additional review will not
be deemed necessary (unless other
conditions necessitating review exist, as
described in the Letters of Authorization
section). If applicants do not use the
modeling provided by the rule,
however, NMFS may publish a notice in
the Federal Register soliciting public
comment, if the model or inputs differ
substantively from those that have been
reviewed by NMFS and the public
previously, if the model or inputs differ
substantively from those that have been
reviewed by NMFS and the public
previously. The estimated take of
marine mammals for each species will
then be compared against the best
available scientific information on
species or stock abundance estimate as
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determined by NMFS, and estimates
that do not exceed one-third of that
estimate will be considered small
numbers.
Adaptive Management
The regulations governing the take of
marine mammals incidental to
geophysical survey activities contain an
adaptive management component. The
comprehensive reporting requirements
associated with this rule (see the
Monitoring and Reporting section) are
designed to provide NMFS with
monitoring data from the previous year
to allow consideration of whether any
changes are appropriate. The use of
adaptive management allows NMFS to
consider new information from different
sources to determine (with input from
the LOA-holders regarding
practicability) on a regular (e.g., annual
or biennial) basis if mitigation or
monitoring measures should be
modified (including additions or
deletions). Mitigation measures could be
modified if new data suggests that such
modifications would have a reasonable
likelihood of reducing adverse effects to
marine mammal species or stocks or
their habitat and if the measures are
practicable. The adaptive management
process and associated reporting
requirements would serve as the basis
for evaluating performance and
compliance.
The following are some of the
possible sources of applicable data to be
considered through the adaptive
management process: (1) Results from
monitoring reports, as required by
MMPA authorizations; (2) results from
general marine mammal and sound
research; and (3) any information which
reveals that marine mammals may have
been taken in a manner, extent, or
number not authorized through these
regulations and subsequent LOAs or
that the specified activity may be having
more than a negligible impact on
affected stocks.
Under this rule, NMFS plans to
implement an annual adaptive
management process including BOEM,
BSEE, industry operators (including
geophysical companies as well as
exploration and production companies),
and others as appropriate. Industry
operators may elect to be represented in
this process by their respective trade
associations. NMFS, BOEM, and BSEE
(i.e., the regulatory agencies) and
industry operators who have conducted
or contracted for survey operations in
the GOM in the prior year (or their
representatives) will provide an agreedupon description of roles and
responsibilities, as well as points of
contact, in advance of each year’s
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adaptive management process. The
foundation of the adaptive management
process will be the annual
comprehensive reports produced by
LOA-holders (or their representatives),
as well as the results of any relevant
research activities, including research
supported voluntarily by the oil and gas
industry and research supported by the
Federal government. Please see the
Monitoring Contribution Through Other
Research section in the notice of
proposed rulemaking for a description
of representative past research efforts.
The outcome of the annual adaptive
management process would be an
assessment of effects to marine mammal
populations in the GOM relative to
NMFS’ determinations under the
MMPA and ESA, recommendations
related to mitigation, monitoring, and
reporting, and recommendations for
future research (whether supported by
industry or the regulatory agencies).
Data collection and reporting by
individual LOA-holders will occur on
an ongoing basis, per the terms of issued
LOAs. In a given annual cycle, the
comprehensive annual report will
summarize and synthesize all LOAspecific reports received, with report
development (supported through
collaboration of individual LOA-holders
or by their representatives) occurring for
90 days following the end of a given
one-year period. Review and revision of
the report, followed by a joint meeting
of the parties, will occur within 90 days
following receipt of the annual report.
Any agreed-upon modifications will
occur through the process for
modifications and/or adaptive
management described in the regulatory
text following this preamble.
Monitoring Contribution Through Other
Research
NMFS’ MMPA implementing
regulations require that applicants for
incidental take authorizations describe
the suggested means of coordinating
research opportunities, plans, and
activities relating to reducing incidental
taking and evaluating its effects (50 CFR
216.104(a)(14)). Such coordination can
serve as an effective supplement to the
monitoring and reporting required
pursuant to issued LOAs and/or
incidental take regulations. NMFS
expects that relevant research efforts
will inform the annual adaptive
management process described above,
and that levels and types of research
efforts will change from year to year in
response to identified needs and
evolutions in knowledge, emerging
trends in the economy and available
funding, and available scientific and
technological resources. In the notice of
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proposed rulemaking, NMFS described
examples of relevant research efforts (83
FR 29300–29301). We do not repeat that
information here, but refer the reader to
that notice for more information. The
described efforts may not be predictive
of any future levels and types of
research efforts. Research occurring in
locations other than the GOM may be
relevant to understanding the effects of
geophysical surveys on marine
mammals or marine mammal
populations or the effectiveness of
mitigation. NMFS also refers the reader
to the industry Joint Industry Program
(JIP) website
(www.soundandmarinelife.org), which
hosts a database of available products
funded partially or fully through the JIP,
and to BOEM’s Environmental Studies
Program (ESP), which develops, funds,
and manages scientific research to
inform policy decisions regarding outer
continental shelf resource development
(www.boem.gov/studies).
Impact on Availability of Affected
Species for Taking for Subsistence Uses
There are no relevant subsistence uses
of marine mammals implicated by these
actions. Therefore, NMFS has
determined that the total taking of
affected species or stocks will not have
an unmitigable adverse impact on the
availability of such species or stocks for
taking for subsistence purposes.
Endangered Species Act (ESA)
Section 7 of the ESA requires Federal
agencies to insure that their actions are
not likely to jeopardize the continued
existence of endangered or threatened
species or adversely modify or destroy
their designated critical habitat. Federal
agencies must consult with NMFS for
actions that may affect such species
under NMFS’ jurisdiction or critical
habitat designated for such species.
At the conclusion of consultation, the
consulting agency provides an opinion
stating whether the Federal agency’s
action is likely to jeopardize the
continued existence of ESA-listed
species or destroy or adversely modify
designated critical habitat.
NMFS’s issuance of this final rule,
and any subsequent LOAs, is subject to
the requirements of Section 7 of the
ESA. Therefore, NMFS’ Office of
Protected Resources (OPR), Permits and
Conservation Division requested
initiation of a formal consultation with
the NMFS OPR, ESA Interagency
Cooperation Division on the proposed
issuance of the rule and subsequent
LOAs on July 19, 2018. The formal
consultation concluded and a final
Biological Opinion (BiOp) was issued
on March 13, 2020. The BiOp concluded
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5441
that the Permits and Conservation
Division’s proposed action is not likely
to jeopardize the continued existence of
sperm whales or the GOM Bryde’s
whale.
National Environmental Policy Act
In 2017, BOEM produced a final
Programmatic Environmental Impact
Statement (PEIS) to evaluate the direct,
indirect, and cumulative impacts of
geological and geophysical survey
activities on the GOM OCS, pursuant to
requirements of NEPA. These activities
include geophysical surveys in support
of hydrocarbon exploration, as are
described in the MMPA petition before
NMFS. The PEIS is available online at:
www.boem.gov/Gulf-of-MexicoGeological-and-Geophysical-ActivitiesProgrammatic-EIS/. NOAA, through
NMFS, participated in preparation of
the PEIS as a cooperating agency due to
its legal jurisdiction and special
expertise in conservation and
management of marine mammals,
including its responsibility to authorize
incidental take of marine mammals
under the MMPA.
NEPA, Council on Environmental
Quality (CEQ) regulations, and NOAA’s
NEPA implementing procedures (NOAA
Administrative Order (NAO) 216–6A)
encourage the use of programmatic
NEPA documents to streamline
decision-making. NMFS reviewed the
Final PEIS and determined that it meets
the requirements of the CEQ regulations
(40 CFR part 1500–1508) and NAO 216–
6A. NMFS further determined, after
independent review, that the Final PEIS
satisfied NMFS’ comments and
suggestions in the NEPA process. In the
notice of proposed rulemaking, NMFS
stated its intention to adopt BOEM’s
analysis in order to assess the impacts
to the human environment of issuance
of the subject ITR, and that we would
review all comments submitted in
response to the notice as we completed
the NEPA process, including a final
decision of whether to adopt BOEM’s
PEIS and sign a Record of Decision
related to issuance of the ITR and
subsequent LOAs. Following review of
public comments received, NMFS
confirmed that it would be appropriate
to adopt BOEM’s analysis in order to
support assessment of the impacts to the
human environment of issuance of the
subject ITR and subsequent LOAs.
Therefore NMFS prepared a Record of
Decision for the following purposes: (1)
To adopt the Final PEIS to support
NMFS’ analysis associated with
issuance of incidental take
authorizations pursuant to section
101(a)(5)(A) or (D) of the MMPA and the
regulations governing the taking and
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importing of marine mammals (50 CFR
part 216); and (2) in accordance with 40
CFR 1505.2, to announce and explain
the basis for NMFS’ decision to review
and potentially issue incidental take
authorizations under the MMPA on a
case-by-case basis, if appropriate.
Letters of Authorization
Under these incidental take
regulations, industry operators may
apply for and obtain LOAs, as described
in NMFS’ MMPA implementing
regulations (50 CFR 216.106). LOAs may
be issued for any time period that does
not exceed the effective duration of the
final rule, provided the description of
the activity in the request includes a
sufficient degree of specificity with
which to evaluate whether the activity
falls within the scope of the rule.
Because the specified activity described
herein does not provide actual specifics
of the timing, location, and survey
design for activities that would be the
subject of issued LOAs, such requests
must include, at minimum, the
information described at 50 CFR
216.104(a)(1) and (2), and should
include an affirmation of intent to
adhere to the mitigation, monitoring,
and reporting requirements described in
the regulations. The level of effort
proposed by an operator would be used
to develop an LOA-specific take
estimate based on the results of Zeddies
et al. (2015, 2017a).
The proposed rule indicated that LOA
applications with take estimates based
on modeling other than that specifically
included in the modeling report used to
support the EIS and the proposed rule
(Zeddies et al., 2015, 2017a) would be
published for public comment prior to
the issuance of an LOA. However, upon
further consideration of the ‘‘Gulf of
Mexico Acoustic Exposure Model
Variable Analysis’’ (Zeddies et al.,
2017b; ‘‘Acoustic Exposure Model
Variable Analysis’’) provided by IAGC
and API to NMFS prior to the
publication of the proposed rule and
made available to the public with the
proposed rule and the Associations’
public comments, which extensively
referenced the Acoustic Exposure Model
Variable Analysis, the final rule more
flexibly provides that if applicants do
not use the modeling provided by the
rule, NMFS may publish a notice in the
Federal Register soliciting public
comment, if the model or inputs differ
substantively from those that have been
reviewed by NMFS and the public
previously. Specifically, the Acoustic
Exposure Model Variable Analysis
includes the results (i.e., take estimates)
of a supplemental analysis of the same
modeling effort used in Zeddies et al.
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(2015, 2017a) to support the proposed
rule, but evaluating the effects on the
modeling results of different variables.
One analyzed variable of particular
utility was the use of a smaller airgun
array that could serve as a reasonable
representative for some of the smaller
arrays that are commonly used in the
GOM. This specific applicable example,
in which the model and inputs of this
Acoustic Exposure Model Variable
Analysis have been reviewed by NMFS
and the public previously (both in that
they mirror Zeddies et al. (2015, 2017a)
and in that NMFS also explicitly made
the Acoustic Exposure Model Variable
Analysis available to the public during
the comment period), illustrates the
need to provide flexibility and make
efficient use of previous public and
agency review. NMFS has, therefore,
determined it appropriate to allow that
additional public review is not needed
unless the model or inputs differ
substantively from those that have been
reviewed by NMFS and the public
previously. Further, we explicitly note
the utility of the modeling and results
presented in the Acoustic Exposure
Model Variable Analysis report for
representing smaller airgun arrays that
are commonly used in the GOM and
affirm that further public comment on
that report should not be necessary prior
to the use of its results to support the
issuance of LOAs.
Technologies continue to evolve to
meet the technical, environmental, and
economic challenges of oil and gas
development. The use of ‘‘new and
unusual technologies’’ (NUT), i.e.,
technologies other than those described
herein, will be evaluated on a case-bycase basis and may require public
review. Some seemingly new
technologies proposed for use by
operators are often extended
applications of existing technologies
and interface with the environment in
essentially the same way as well-known
or conventional technologies. For such
evaluations, NMFS will follow the
existing process used by BOEM, by
using the following considerations:
• Has the technology or hardware
been used previously or extensively in
the U.S. GOM under operating
conditions similar to those anticipated
for the activities proposed by the
operator? If so, the technology would
not be considered a NUT;
• Does the technology function in a
manner that potentially causes different
impacts to the environment than similar
equipment or procedures did in the
past? If so, the technology would be
considered a NUT;
• Does the technology have a
significantly different interface with the
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environment than similar equipment or
procedures did in the past? If so, the
technology would be considered a NUT;
and
• Does the technology include
operating characteristics that are outside
established performance parameters? If
so, the technology would be considered
a NUT.
NMFS will consult with BOEM as
well as with NMFS’ ESA Interagency
Cooperation Division regarding the level
of review necessary for issuance of an
LOA in which a NUT is proposed for
use.
Classification
Pursuant to the procedures
established to implement Executive
Order 12866, the Office of Management
and Budget (OMB) has determined that
this rule is economically significant.
Accordingly, a regulatory impact
analysis (RIA) was prepared and made
available for review by the public.
Following review of public comments, a
final RIA has been prepared and is
available online at:
www.fisheries.noaa.gov/action/
incidental-take-authorization-oil-andgas-industry-geophysical-surveyactivity-gulf-mexico. Appendix B of the
RIA provides a final regulatory
flexibility analysis (FRFA, discussed
below), while Appendix C addresses
other compliance requirements.
The RIA evaluates the potential costs
and benefits of these incidental take
regulations against two baselines, a
baseline corresponding with regulatory
conditions in place since 2013 pursuant
to a settlement agreement, as amended
through stipulated agreement, involving
a stay of litigation (NRDC et al. v.
Bernhardt et al., Civil Action No. 2:10
cv–01882 (E.D. La.)), and a baseline
corresponding to conditions prior to the
2013 settlement agreement. Under the
settlement agreement that is in effect,
industry trade groups representing
operators agreed to include certain
mitigation requirements for geophysical
surveys in the GOM.
OMB Circular A–4 provides that
agencies may present multiple baselines
where this would provide additional
useful information to the public on the
projected effects of the regulation.
NMFS presented both baselines for
public information and comment,
consistent with the Circular A–4
provision allowing agencies to present
multiple baselines. No information or
comments regarding the economic
baselines were received.
These regulations require new
mitigation measures relative to the
settlement baseline and, thus, new costs
for survey operators. However, the rule
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also alleviates the burden of
implementing minimum separation
distance requirements for deep
penetration airgun surveys, as required
under the settlement agreement. The
rule also results in certain indirect (but
non-monetized) costs. However, the RIA
analysis demonstrates that these costs
are not likely to be significant.
Moreover, as described in the RIA, total
costs related to compliance for survey
activities are small compared with
expenditures on other aspects of oil and
gas industry operations, and direct
compliance costs of the regulatory
requirements are unlikely to result in
materially reduced oil and gas activities
in the GOM.
The rule also results in certain nonmonetized benefits. The protection of
marine mammals afforded by this rule
(pursuant to the requirements of the
MMPA) benefits the regional economic
value of marine mammals via tourism
and recreation to some extent, as
mitigation measures applied to
geophysical survey activities in the
GOM region are expected to benefit the
marine mammal populations that
support this economic activity in the
GOM. In addition, some degree of
benefits can be expected to accrue solely
via ecological benefits to marine
mammals and other wildlife as a result
of the regulatory requirements. The
published literature (described in the
RIA) is clear that healthy populations of
marine mammals and other co-existing
species benefit regional economies and
provide social welfare benefits to
people. However, the literature does not
provide a basis for quantitatively
valuing the cost of anticipated
incremental changes in environmental
disturbance and marine mammal
harassment associated with the rule.
Notably, the rule also affords
significant benefit to the regulated
industry by providing regulatory
certainty through an efficient framework
within which to achieve compliance
with the MMPA. In particular, cost
savings may be generated by the
reduced administrative effort required
to obtain an LOA under the framework
established by a rule compared to what
would be required to obtain an
incidental harassment authorization
(IHA) under section 101(a)(5)(D). Absent
the rule, to attain equivalent compliance
with the MMPA, survey operators in the
GOM would need to apply for an IHA.
Although not monetized in the RIA,
NMFS’ analysis indicates that the
upfront work associated with the rule
(e.g., analyses, modeling, process for
obtaining LOA) likely saves significant
time and money for operators. A
conservative cost savings calculation,
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based on estimates of the costs for IHA
applications relative to LOA application
costs and an assumption of the number
of likely authorizations based on total
annual survey days and survey
estimates included in the RIA, ranges
from $500,000 to $1.5 million annually.
In terms of timing, NMFS recommends
that IHA applicants contact the agency
six to nine months in advance of the
planned activity, whereas NMFS
anticipates a timeframe of three months
or less (depending upon the content of
the request and the activities covered)
for LOA applications under this rule.
Details regarding cost estimation are
available in the RIA. A qualitative
evaluation of indirect costs related to
the regulations is also provided in the
RIA. Note that these costs would be
diffused across all operators receiving
LOAs.
NMFS prepared a FRFA, as required
by Section 603 of the Regulatory
Flexibility Act (RFA), for this rule. The
FRFA describes the economic effects
this rule will have on small entities. A
description of this action, why it is
being considered, the objectives of the
action, and the legal basis for the action
are contained in the preamble of this
rule. A copy of the full analysis is
available as an appendix to the RIA. The
MMPA provides the statutory basis for
this rule. No duplicative, overlapping,
or conflicting Federal rules have been
identified. A detailed summary of the
initial regulatory flexibility analysis was
provided at the proposed rule stage. No
comments or information regarding this
analysis were received.
This final rule is expected to directly
regulate businesses that conduct
geophysical surveys in the GOM with
the potential to incidentally take marine
mammals. Some of these businesses
may be defined as small entities. The
FRFA is summarized below.
The FRFA focuses on identifying
small businesses that would bear the
incremental survey costs associated
with the rule. These may include
entities undertaking, commissioning, or
purchasing surveys. In order to estimate
the number of small entities to which
the rule will apply, permit applications
between 2006 and 2015 were analyzed
to understand what industries were
involved in permit applications for
geophysical surveys in the Gulf of
Mexico and to identify U.S.-based
permit applicants that would be
classified as small according to Small
Business Administration definitions and
the most recent revenue or employment
data available. In total, 34 U.S.-based
small businesses applied for
geophysical survey permits in the Gulf
of Mexico between 2006 and 2015. By
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5443
assuming that the same proportion of
international, large, and small
companies will undertake the surveys
over the next five years as occurred
during 2006 to 2015, the likely number
of future surveys that will include small
entity applicants may be estimated.
Accordingly, NMFS estimates that small
entities would apply for approximately
32 to 53 surveys over the next five years,
or approximately six to 11 surveys
annually. Historically, there was a ratio
of approximately 2.2 surveys applied for
per small entity. Using this ratio, NMFS
estimates that approximately 15 to 24
small companies will likely apply for
permits over the next five years, or
approximately 3 to 5 small companies
each year. The future distribution of
small survey companies by industry is
not known, but the historical pattern of
surveys suggests that companies
involved in oil and gas extraction
(NAICS 2111) and support activities for
oil and gas (213112) will account for the
majority of the survey applications by
small companies.
A review of the reported annual
revenues for the 34 small entities that
applied for survey permits between
2006 and 2015 reveals a wide range,
with the lowest revenues reported to be
$0.04 million and the highest revenues
reported to be $1.9 billion. Average
revenues for the small entities who
applied for permits were $232 million,
with median revenues of $12.26 million.
We note, however, that the revenues
and numbers of employees reported for
many of these small companies
appeared to be erroneous, in multiple
instances reporting annual revenues
significantly less than the costs of
conducting even the lowest cost
surveys. As a result, these revenue
estimates are likely to be inaccurate or,
alternatively, permit applicants must
pass survey costs on to the companies
that purchase or commission the
seismic data. Given that the oil and gas
extraction companies are generally the
entities purchasing the survey data, we
expect that it is most likely that survey
costs are ultimately borne by NAICS
2111 (oil and gas extraction), either as
the permittees for the survey permit or
because the other, smaller businesses
pass these costs along in the data
purchase price.
In summary, the FRFA finds the
following: First, in the majority of cases
(88 percent), survey permit applicants
are large businesses. Second, when the
permit applicants are small businesses,
the majority of the time (63 percent)
they are oil and gas extractors (NAICS
2111). Third, together, these permits (for
large businesses and small businesses
with high annual revenues for which
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rule costs are a small fraction) account
for 96 percent of the survey permits.
Fourth, while small entities in other
industries occasionally apply for
permits (four percent historically), these
businesses are quite small, with average
annual revenues in the millions or even
less. Given their size, it is unlikely that
these permit applicants bear survey
costs; otherwise it would be reflected in
their annual revenues (i.e., their
revenues on average would reflect that
they recover their costs). Accordingly,
NMFS expects it is most likely that
survey costs are passed on to oil and gas
extraction companies who commission
the surveys or purchase the data. And
fifth, overall, up to five small businesses
(NAICS 2111) per year may experience
increased costs of between 0.1 and 0.7
percent of average annual revenues.
The draft version of the RIA and the
Initial Regulatory Flexibility Analysis
considered effects of a more stringent
alternative than the proposed rule. The
more stringent alternative included
additional shutdown requirements and
area closures for surveys, generating
costs up to 20 percent greater than the
proposed rule. NMFS did not elect to
proceed with these elements of the more
stringent alternative in the final rule,
which reduces the potential for impacts
to small businesses. NMFS determined
that the final rule achieves the statutory
objectives with a lower regulatory
burden. As described above, a relatively
small portion of total survey activities
are undertaken by small entities and the
FRFA determines that it is unlikely that
small entities will bear the compliance
costs described in the RIA.
This final rule revises the information
collection request (ICR) requirement
associated with OMB Control Number
0648–0151 to allow for the expected
increase in applicants/respondents due
to this final action. This revision is
subject to review and approval by OMB
under the Paperwork Reduction Act
(PRA) and has been submitted to OMB.
NMFS published a 30-day Federal
Register notice (85 FR 60765; September
28, 2020) that provided for an additional
comment period. Details on the new
information collection requirements can
be found in the RIA Appendix C.2.
NMFS anticipates that 95 to 151
geophysical surveys will take place
annually on average over the five years
of the regulations in the GOM that
would be subject to potential
information collection requirements.
Due to this final rule, NMFS estimates
at least 95 new LOA applications
annually. Because the existing OMB
Control Number 0648–0151 expires less
than a year (June 30, 2021) after this
final rule publishes, there will be less
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than a year for respondents to carry out
work under these regulations before this
OMB Control Number expires. Thus,
NMFS estimates no more than onequarter of respondents (24) will
complete work to the point of
developing an annual report prior to
when 0648–0151 must be renewed.
We invite the general public and other
Federal agencies to comment on
proposed and continuing information
collections, which helps us assess the
impact of our information collection
requirements and minimize the public’s
reporting burden. Written comments
and recommendations for this
information collection should be
submitted at the following website:
www.reginfo.gov/public/do/PRAMain.
Find this particular information
collection by using the search function
and entering either the title of the
collection or the OMB Control Number
0648–0151.
Notwithstanding any other provision
of the law, no person is required to
respond to, nor shall any person be
subject to a penalty for failure to comply
with, a collection of information subject
to the requirements of the PRA, unless
that collection of information displays a
currently valid OMB Control Number.
List of Subjects in 50 CFR Part 217
Exports, Fish, Imports, Indians,
Labeling, Marine mammals, Penalties,
Reporting and recordkeeping
requirements, Seafood, Transportation.
Dated: December 7, 2020.
Samuel D. Rauch III,
Deputy Assistant Administrator for
Regulatory Programs, National Marine
Fisheries Service.
For reasons set forth in the preamble,
50 CFR part 217 is amended as follows:
PART 217—REGULATIONS
GOVERNING THE TAKING AND
IMPORTING OF MARINE MAMMALS
1. The authority citation for part 217
continues to read as follows:
■
Authority: 16 U.S.C. 1361 et seq.
2. Add Subpart S, consisting of
§§ 217.180 through 217.189, to read as
follows:
■
Subpart S—Taking Marine Mammals
Incidental to Geophysical Survey Activities
in the Gulf of Mexico
Sec.
217.180 Specified activity and specified
geographical region.
217.181 Effective dates.
217.182 Permissible methods of taking.
217.183 Prohibitions.
217.184 Mitigation requirements.
217.185 Requirements for monitoring and
reporting.
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217.186 Letters of Authorization.
217.187 Renewals and modifications of
Letters of Authorization.
217.188 [Reserved]
217.189 [Reserved]
Subpart S—Taking Marine Mammals
Incidental to Geophysical Survey
Activities in the Gulf of Mexico
§ 217.180 Specified activity and specified
geographical region.
(a) Regulations in this subpart apply
only to oil and gas industry operators
(LOA-holders), and those persons
authorized to conduct activities on their
behalf, for the taking of marine
mammals that occurs in the area
outlined in paragraph (b) of this section
and that occurs incidental to
geophysical survey activities.
(b) The taking of marine mammals by
oil and gas industry operators may be
authorized in a Letter of Authorization
(LOA) only if it occurs within U.S.
waters in the Gulf of Mexico, outside
the area subject to a Congressional
leasing moratorium under the Gulf of
Mexico Energy Security Act (GOMESA)
(Pub L. 109–432, § 104) as of the
effective date of these regulations.
§ 217.181
Effective dates.
Regulations in this subpart are
effective from April 19, 2021 through
April 19, 2026.
§ 217.182
Permissible methods of taking.
Under LOAs issued pursuant to
§§ 216.106 of this chapter and 217.186,
LOA-holders may incidentally, but not
intentionally, take marine mammals
within the area described in
§ 217.180(b) by Level A and Level B
harassment associated with geophysical
survey activities, provided the activity
is in compliance with all terms,
conditions, and requirements of the
regulations in this subpart and the
appropriate LOA.
§ 217.183
Prohibitions.
Notwithstanding takings
contemplated in §§ 217.180 and
217.182, and authorized by a LOA
issued under §§ 216.106 of this chapter
and 217.186, no person in connection
with the activities described in
§ 217.180 may:
(a) Violate, or fail to comply with, the
terms, conditions, and requirements of
this subpart or a LOA issued under
§§ 216.106 of this chapter and 217.186;
(b) Take any marine mammal not
specified in such LOAs;
(c) Take any marine mammal
specified in such LOAs in any manner
other than as specified; or
(d) Take a marine mammal specified
in such LOAs if NMFS determines such
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taking results in more than a negligible
impact on the species or stocks of such
marine mammal.
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§ 217.184
Mitigation requirements.
When conducting the activities
identified in § 217.180, the mitigation
measures contained in any LOA issued
under §§ 216.106 of this chapter and
217.186 must be implemented. These
mitigation measures shall include but
are not limited to:
(a) General conditions. (1) A copy of
any issued LOA must be in the
possession of the LOA-holder, vessel
operator, other relevant personnel, the
lead protected species observer (PSO),
and any other relevant designees
operating under the authority of the
LOA.
(2) The LOA-holder must instruct
relevant vessel personnel with regard to
the authority of the protected species
monitoring team (PSO team), and must
ensure that relevant vessel personnel
and PSO team participate in a joint
onboard briefing, led by the vessel
operator and lead PSO, prior to
beginning work to ensure that
responsibilities, communication
procedures, protected species
monitoring protocols, operational
procedures, and LOA requirements are
clearly understood. This briefing must
be repeated when relevant new
personnel join the survey operations
before work involving those personnel
commences.
(3) The acoustic source must be
deactivated when not acquiring data or
preparing to acquire data, except as
necessary for testing. Unnecessary use
of the acoustic source must be avoided.
For surveys using airgun arrays as the
acoustic source, notified operational
capacity (i.e., total array volume) (not
including redundant backup airguns)
must not be exceeded during the survey,
except where unavoidable for source
testing and calibration purposes. All
occasions where activated source
volume exceeds notified operational
capacity must be communicated to the
PSO(s) on duty and fully documented.
The lead PSO must be granted access to
relevant instrumentation documenting
acoustic source power and/or
operational volume.
(4) PSOs must be used as specified in
this paragraph (a)(4).
(i) LOA-holders must use
independent, dedicated, qualified PSOs,
meaning that the PSOs must be
employed by a third-party observer
provider, must have no tasks other than
to conduct observational effort, collect
data, and communicate with and
instruct relevant vessel crew with regard
to the presence of protected species and
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mitigation requirements (including brief
alerts regarding maritime hazards), and
must be qualified pursuant to
§ 217.185(a) (except as specified at
§ 217.184(d)(2)(iii–iv)). Acoustic PSOs
are required to complete specialized
training for operating passive acoustic
monitoring (PAM) systems and are
encouraged to have familiarity with the
vessel on which they will be working.
PSOs may act as both acoustic and
visual observers (but not
simultaneously), so long as they
demonstrate that their training and
experience are sufficient to perform
each task.
(ii) The LOA-holder must submit PSO
resumes for NMFS review and approval
prior to commencement of the survey
(except as specified at
§ 217.184(d)(2)(iii)). Resumes should
include dates of training and any prior
NMFS approval, as well as dates and
description of last experience, and must
be accompanied by information
documenting successful completion of
an acceptable training course. NMFS is
allowed one week to approve PSOs from
the time that the necessary information
is received by NMFS, after which PSOs
meeting the minimum requirements will
automatically be considered approved.
(iii) At least one visual PSO and two
acoustic PSOs (when required) aboard
each acoustic source vessel must have a
minimum of 90 days at-sea experience
working in those roles, respectively,
with no more than eighteen months
elapsed since the conclusion of the atsea experience (except as specified at
§ 217.184(d)(2)(iii)). One visual PSO
with such experience must be
designated as the lead for the entire PSO
team. The lead must coordinate duty
schedules and roles for the PSO team
and serve as the primary point of
contact for the vessel operator. (Note
that the responsibility of coordinating
duty schedules and roles may instead be
assigned to a shore-based, third-party
monitoring coordinator.) To the
maximum extent practicable, the lead
PSO must devise the duty schedule
such that experienced PSOs are on duty
with those PSOs with appropriate
training but who have not yet gained
relevant experience.
(b) Deep penetration surveys. (1) Deep
penetration surveys are defined as
surveys using airgun arrays with total
volume greater than 1,500 in3.
(2) Visual monitoring must be
conducted as specified in this paragraph
(b)(2).
(i) During survey operations (i.e., any
day on which use of the acoustic source
is planned to occur, and whenever the
acoustic source is in the water, whether
activated or not), a minimum of two
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PSOs must be on duty and conducting
visual observations at all times during
daylight hours (i.e., from 30 minutes
prior to sunrise through 30 minutes
following sunset).
(ii) Visual monitoring must begin not
less than 30 minutes prior to ramp-up
and must continue until one hour after
use of the acoustic source ceases or until
30 minutes past sunset.
(iii) Visual PSOs must coordinate to
ensure 360° visual coverage around the
vessel from the most appropriate
observation posts, and must conduct
visual observations using binoculars
and the naked eye while free from
distractions and in a consistent,
systematic, and diligent manner.
(iv) Visual PSOs must immediately
communicate all observations of marine
mammals to the on-duty acoustic PSO,
including any determination by the PSO
regarding species identification,
distance, and bearing and the degree of
confidence in the determination.
(v) Any observations of marine
mammals by crew members aboard any
vessel associated with the survey must
be relayed to the PSO team.
(vi) During good conditions (e.g.,
daylight hours; Beaufort sea state (BSS)
3 or less), visual PSOs must conduct
observations when the acoustic source
is not operating for comparison of
sighting rates and behavior with and
without use of the acoustic source and
between acquisition periods, to the
maximum extent practicable.
(vii) Visual PSOs may be on watch for
a maximum of two consecutive hours
followed by a break of at least one hour
between watches and may conduct a
maximum of 12 hours of observation per
24-hour period. NMFS may grant an
exception for LOA applications that
demonstrate such a ‘‘two hours on/one
hour off’’ duty cycle is not practicable,
in which case visual PSOs will be
subject to a maximum of four
consecutive hours on watch followed by
a break of at least two hours between
watches. Combined observational duties
(visual and acoustic but not at the same
time) must not exceed 12 hours per 24hour period for any individual PSO.
(3) Acoustic monitoring must be
conducted as specified in this paragraph
(b)(3).
(i) All source vessels must use a
towed PAM system at all times when
operating in waters deeper than 100 m,
which must be monitored by a
minimum of one acoustic PSO
beginning at least 30 minutes prior to
ramp-up, at all times during use of the
acoustic source, and until one hour after
use of the acoustic source ceases. ‘‘PAM
system’’ refers to calibrated hydrophone
arrays with full system redundancy to
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detect, identify, and estimate distance
and bearing to vocalizing cetaceans,
coupled with appropriate software to
aid monitoring and listening by a PAM
operator skilled in bioacoustics analysis
and computer system specifications
capable of running appropriate software.
The PAM system must have at least one
calibrated hydrophone (per each
deployed hydrophone type and/or set)
sufficient for determining whether
background noise levels on the towed
PAM system are sufficiently low to meet
performance expectations. Applicants
must provide a PAM plan including
description of the hardware and
software proposed for use prior to
proceeding with any survey where PAM
is required.
(ii) Acoustic PSOs must immediately
communicate all detections of marine
mammals to visual PSOs (when visual
PSOs are on duty), including any
determination by the PSO regarding
species identification, distance, and
bearing, and the degree of confidence in
the determination.
(iii) Acoustic PSOs may be on watch
for a maximum of four consecutive
hours followed by a break of at least two
hours between watches, and may
conduct a maximum of 12 hours of
observation per 24-hour period.
Combined observational duties (visual
and acoustic but not at the same time)
must not exceed 12 hours per 24-hour
period for any individual PSO.
(iv) Survey activity may continue for
30 minutes when the PAM system
malfunctions or is damaged, while the
PAM operator diagnoses the issue. If the
diagnosis indicates that the PAM system
must be repaired to solve the problem,
operations may continue for an
additional two hours without acoustic
monitoring during daylight hours only
under the following conditions:
(A) Sea state is less than or equal to
BSS 4;
(B) No marine mammals (excluding
delphinids) detected solely by PAM in
the applicable exclusion zone in the
previous two hours;
(C) NMFS is notified via email as soon
as practicable with the time and
location in which operations began
occurring without an active PAM
system; and
(D) Operations with an active acoustic
source, but without an operating PAM
system, do not exceed a cumulative total
of four hours in any 24-hour period.
(4) PSOs must establish and monitor
applicable exclusion and buffer zones.
These zones must be based upon the
radial distance from the edges of the
airgun array (rather than being based on
the center of the array or around the
vessel itself). During use of the acoustic
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source (i.e., anytime the acoustic source
is active, including ramp-up),
occurrence of marine mammals within
the relevant buffer zone (but outside the
exclusion zone) should be
communicated to the operator to
prepare for the potential shutdown of
the acoustic source.
(i) Two exclusion zones are defined,
depending on the species and context.
A standard exclusion zone
encompassing the area at and below the
sea surface out to a radius of 500 meters
from the edges of the airgun array (0–
500 m) is defined. For special
circumstances (defined at
§ 217.184(b)(9)(v)), the exclusion zone
encompasses an extended distance of
1,500 meters (0–1,500 m).
(ii) During pre-start clearance
monitoring (i.e., before ramp-up begins),
the buffer zone acts as an extension of
the exclusion zone in that observations
of marine mammals within the buffer
zone would also preclude airgun
operations from beginning (i.e., rampup). For all marine mammals (except
where superseded by the extended
1,500-m exclusion zone), the buffer zone
encompasses the area at and below the
sea surface from the edge of the 0–500
meter exclusion zone out to a radius of
1,000 meters from the edges of the
airgun array (500–1,000 m). The buffer
zone is not applicable when the
exclusion zone is greater than 500
meters, i.e., the observational focal zone
is not increased beyond 1,500 meters.
(5) A ramp-up procedure, involving a
step-wise increase in the number of
airguns firing and total active array
volume until all operational airguns are
activated and the full volume is
achieved, is required at all times as part
of the activation of the acoustic source.
A 30-minute pre-start clearance
observation period must occur prior to
the start of ramp-up. The LOA-holder
must adhere to the following pre-start
clearance and ramp-up requirements:
(i) The operator must notify a
designated PSO of the planned start of
ramp-up as agreed upon with the lead
PSO; the notification time should not be
less than 60 minutes prior to the
planned ramp-up.
(ii) Ramp-ups must be scheduled so as
to minimize the time spent with source
activated prior to reaching the
designated run-in.
(iii) A designated PSO must be
notified again immediately prior to
initiating ramp-up procedures and the
operator must receive confirmation from
the PSO to proceed.
(iv) Ramp-up must not be initiated if
any marine mammal is within the
applicable exclusion or buffer zone. If a
marine mammal is observed within the
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exclusion zone or the buffer zone during
the 30-minute pre-start clearance
period, ramp-up must not begin until
the animal(s) has been observed exiting
the zones or until an additional time
period has elapsed with no further
sightings (15 minutes for small
delphinids and 30 minutes for all other
species).
(v) Ramp-up must begin by activating
a single airgun of the smallest volume
in the array and shall continue in stages
by doubling the number of active
elements at the commencement of each
stage, with each stage of approximately
the same duration. Total duration must
not be less than 20 minutes. The
operator must provide information to
the PSO documenting that appropriate
procedures were followed.
(vi) Ramp-up must cease and the
source shut down upon observation of
marine mammals within the applicable
exclusion zone. Once ramp-up has
begun, observations of marine mammals
within the buffer zone do not require
shutdown.
(vii) Ramp-up may occur at times of
poor visibility, including nighttime, if
appropriate acoustic monitoring has
occurred with no detections of a marine
mammal other than delphinids in the 30
minutes prior to beginning ramp-up.
Acoustic source activation may only
occur at night where operational
planning cannot reasonably avoid such
circumstances.
(viii) If the acoustic source is shut
down for brief periods (i.e., less than 30
minutes) for reasons other than
implementation of prescribed mitigation
(e.g., mechanical difficulty), it may be
activated again without ramp-up if PSOs
have maintained constant visual and/or
acoustic observation and no visual or
acoustic detections of any marine
mammal have occurred within the
applicable exclusion zone. For any
longer shutdown, pre-start clearance
observation and ramp-up are required.
For any shutdown at night or in periods
of poor visibility (e.g., BSS 4 or greater),
ramp-up is required, but if the
shutdown period was brief and constant
observation maintained, pre-start
clearance watch is not required.
(ix) Testing of the acoustic source
involving all elements requires rampup. Testing limited to individual source
elements or strings does not require
ramp-up but does require the pre-start
clearance observation period.
(6) Shutdowns must be implemented
as specified in this paragraph (b)(6).
(i) Any PSO on duty has the authority
to delay the start of survey operations or
to call for shutdown of the acoustic
source pursuant to the requirements of
this subpart.
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(ii) The operator must establish and
maintain clear lines of communication
directly between PSOs on duty and
crew controlling the acoustic source to
ensure that shutdown commands are
conveyed swiftly while allowing PSOs
to maintain watch.
(iii) When both visual and acoustic
PSOs are on duty, all detections must be
immediately communicated to the
remainder of the on-duty PSO team for
potential verification of visual
observations by the acoustic PSO or of
acoustic detections by visual PSOs.
(iv) When the airgun array is active
(i.e., anytime one or more airguns is
active, including during ramp-up) and
(1) a marine mammal appears within or
enters the applicable exclusion zone
and/or (2) a marine mammal (excluding
delphinids) is detected acoustically and
localized within the applicable
exclusion zone, the acoustic source
must be shut down. When shutdown is
called for by a PSO, the acoustic source
must be immediately deactivated and
any dispute resolved only following
deactivation.
(v) The extended 1,500-m exclusion
zone must be applied upon detection
(visual or acoustic) of a baleen whale,
sperm whale, beaked whale, or Kogia
spp. within the zone.
(vi) Shutdown requirements are
waived for dolphins of the following
genera: Tursiops, Stenella, Steno, and
Lagenodelphis. If a delphinid is visually
detected within the exclusion zone, no
shutdown is required unless the PSO
confirms the individual to be of a genus
other than those listed above, in which
case a shutdown is required. Acoustic
detection of delphinids does not require
shutdown.
(vii) If there is uncertainty regarding
identification or localization, PSOs may
use best professional judgment in
making the decision to call for a
shutdown.
(viii) Upon implementation of
shutdown, the source may be
reactivated after the marine mammal(s)
has been observed exiting the applicable
exclusion zone or following a 30-minute
clearance period with no further
detection of the marine mammal(s).
(c) Shallow penetration surveys. (1)
Shallow penetration surveys are defined
as surveys using airgun arrays with total
volume equal to or less than 1,500 in3,
single airguns, boomers, or equivalent
sources.
(2) LOA-holders conducting shallow
penetration surveys must follow the
requirements defined for deep
penetration surveys at § 217.184(b), with
the following exceptions:
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(i) Acoustic monitoring is not
required for shallow penetration
surveys.
(ii) Ramp-up for small airgun arrays
must follow the procedure described
above for large airgun arrays, but may
occur over an abbreviated period of
time. Ramp-up is not required for
surveys using only a single airgun. For
non-airgun sources, power should be
increased as feasible to effect a ramp-up.
(iii) Two exclusion zones are defined,
depending on the species and context.
A standard exclusion zone
encompassing the area at and below the
sea surface out to a radius of 100 meters
from the edges of the airgun array (if
used) or from the acoustic source (0–100
m) is defined. For special circumstances
(§ 217.184(b)(6)(v)), the exclusion zone
encompasses an extended distance of
500 meters (0–500 m).
(iv) The buffer zone encompasses the
area at and below the sea surface from
the edge of the 0–100 meter exclusion
zone out to a radius of 200 meters from
the edges of the airgun array (if used) or
from the acoustic source (100–200
meters). The buffer zone is not
applicable when the exclusion zone is
greater than 100 meters.
(d) High-resolution geophysical (HRG)
surveys. (1) HRG surveys are defined as
surveys using an electromechanical
source that operates at frequencies less
than 180 kHz, other than those defined
at § 217.184(c)(1) (e.g., side-scan sonar,
multibeam echosounder, or chirp subbottom profiler).
(2) LOA-holders conducting HRG
surveys must follow the requirements
defined for shallow penetration surveys
at § 217.184(c), with the following
exceptions:
(i) No shutdowns are required for
HRG surveys. Pre-start clearance watch
is required as defined at § 217.184(c),
i.e., for a period of 30 minutes and over
a 200-m radius from the acoustic source.
(ii) During survey operations (e.g., any
day on which use of the acoustic source
is planned to occur, and whenever the
acoustic source is in the water, whether
activated or not), a minimum of one
trained and experienced independent
PSO must be on duty and conducting
visual observations at all times during
daylight hours (i.e., from 30 minutes
prior to sunrise through 30 minutes
following sunset) when operating in
waters deeper than 100 m.
(iii) When operating in waters
shallower than 100 m, LOA-holders
must employ one trained visual PSO,
who may be a crew member, only for
purposes of conducting pre-start
clearance monitoring. If PSOs are crew
members, i.e., are not independent
PSOs, the PSOs are not subject to
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NMFS’ approval. In these
circumstances, LOA requests must
describe the training that will be
provided to crew members filling the
role of PSO.
(iv) PSOs are not required during
survey operations in which the active
acoustic source(s) are deployed on an
autonomous underwater vehicle.
(e) Time-area closure. From January 1
through May 31, no use of airguns may
occur shoreward of the 20-m isobath
and between 90–84° W.
(f) Entanglement avoidance. To avoid
the risk of entanglement, LOA-holders
conducting surveys using ocean-bottom
nodes or similar gear must:
(1) Use negatively buoyant coated
wire-core tether cable;
(2) Retrieve all lines immediately
following completion of the survey; and
(3) Attach acoustic pingers directly to
the coated tether cable; acoustic releases
should not be used.
(g) Vessel strike avoidance. LOAholders must adhere to the following
requirements:
(1) Vessel operators and crews must
maintain a vigilant watch for all marine
mammals and must slow down, stop
their vessel, or alter course, as
appropriate and regardless of vessel
size, to avoid striking any marine
mammal. A visual observer aboard the
vessel must monitor a vessel strike
avoidance zone around the vessel,
which shall be defined according to the
parameters stated in this subsection.
Visual observers monitoring the vessel
strike avoidance zone may be thirdparty observers (i.e., PSOs) or crew
members, but crew members
responsible for these duties must be
provided sufficient training to
distinguish marine mammals from other
phenomena and broadly to identify a
marine mammal as a baleen whale,
sperm whale, or other marine mammal;
(2) Vessel speeds must be reduced to
10 kn or less when mother/calf pairs,
pods, or large assemblages of marine
mammals are observed near a vessel;
(3) All vessels must maintain a
minimum separation distance of 500 m
from baleen whales;
(4) All vessels must maintain a
minimum separation distance of 100 m
from sperm whales;
(5) All vessels must, to the maximum
extent practicable, attempt to maintain a
minimum separation distance of 50 m
from all other marine mammals, with an
exception made for those animals that
approach the vessel; and
(6) When marine mammals are
sighted while a vessel is underway, the
vessel must take action as necessary to
avoid violating the relevant separation
distance, e.g., attempt to remain parallel
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to the animal’s course, avoid excessive
speed or abrupt changes in direction
until the animal has left the area. If
marine mammals are sighted within the
relevant separation distance, the vessel
must reduce speed and shift the engine
to neutral, not engaging the engines
until animals are clear of the area. This
does not apply to any vessel towing gear
or any vessel that is navigationally
constrained.
(7) These requirements do not apply
in any case where compliance would
create an imminent and serious threat to
a person or vessel or to the extent that
a vessel is restricted in its ability to
maneuver and, because of the
restriction, cannot comply.
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§ 217.185 Requirements for monitoring
and reporting.
(a) PSO qualifications. (1) PSOs must
successfully complete relevant,
acceptable training, including
completion of all required coursework
and passing (80 percent or greater) a
written and/or oral examination
developed for the training program.
(2) PSOs must have successfully
attained a bachelor’s degree from an
accredited college or university with a
major in one of the natural sciences, a
minimum of 30 semester hours or
equivalent in the biological sciences,
and at least one undergraduate course in
math or statistics. The educational
requirements may be waived if the PSO
has acquired the relevant skills through
alternate experience. Requests for such
a waiver must be submitted to NMFS
and shall include written justification.
Requests will be granted or denied (with
justification) by NMFS within one week
of receipt of submitted information.
Alternate experience that may be
considered includes, but is not limited
to:
(i) Secondary education and/or
experience comparable to PSO duties;
(ii) Previous work experience
conducting academic, commercial, or
government-sponsored marine mammal
surveys; or
(iii) Previous work experience as a
PSO; the PSO should demonstrate good
standing and consistently good
performance of PSO duties.
(b) Equipment. LOA-holders are
required to:
(i) Provide PSOs with bigeye
binoculars (e.g., 25 x 150; 2.7 view
angle; individual ocular focus; height
control) of appropriate quality solely for
PSO use. These must be pedestalmounted on the deck at the most
appropriate vantage point that provides
for optimal sea surface observation, PSO
safety, and safe operation of the vessel.
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(ii) For each vessel required to use a
PAM system, provide a PAM system
that has been verified and tested by an
experienced acoustic PSO who will be
using it during the trip for which
monitoring is required;
(iii) Work with the selected thirdparty observer provider to ensure PSOs
have all equipment (including backup
equipment) needed to adequately
perform necessary tasks, including
accurate determination of distance and
bearing to observed marine mammals.
(Equipment specified in A. through G.
below may be provided by an individual
PSO, the third-party observer provider,
or the LOA-holder, but the LOA-holder
is responsible for ensuring PSOs have
the proper equipment required to
perform the duties specified herein.)
Such equipment, at a minimum, must
include:
(A) Reticle binoculars (e.g., 7 x 50) of
appropriate quality (at least one per
PSO, plus backups);
(B) Global Positioning Unit (GPS)
(plus backup);
(C) Digital camera with a telephoto
lens (the camera or lens should also
have an image stabilization system) that
is at least 300 mm or equivalent on a
full-frame single lens reflex (SLR) (plus
backup);
(D) Compass (plus backup);
(E) Radios for communication among
vessel crew and PSOs (at least one per
PSO, plus backups); and
(F) Any other tools necessary to
adequately perform necessary PSO
tasks.
(c) Data collection. PSOs must use
standardized electronic data forms.
PSOs must record detailed information
about any implementation of mitigation
requirements, including the distance of
marine mammals to the acoustic source
and description of specific actions that
ensued, the behavior of the animal(s),
any observed changes in behavior before
and after implementation of mitigation,
and if shutdown was implemented, the
length of time before any subsequent
ramp-up or activation of the acoustic
source. If required mitigation was not
implemented, PSOs must record a
description of the circumstances. At a
minimum, the following information
should be recorded:
(1) Vessel names (source vessel and
other vessels associated with survey),
vessel size and type, maximum speed
capability of vessel, port of origin, and
call signs;
(2) PSO names and affiliations;
(3) Dates of departures and returns to
port with port name;
(4) Dates of and participants in PSO
briefings;
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(5) Dates and times (Greenwich Mean
Time) of survey effort and times
corresponding with PSO effort;
(6) Vessel location (latitude/
longitude) when survey effort began and
ended and vessel location at beginning
and end of visual PSO duty shifts;
(7) Vessel location at 30-second
intervals (if software capability allows)
or 5-minute intervals (if location must
be manually recorded);
(8) Vessel heading and speed at
beginning and end of visual PSO duty
shifts and upon any line change;
(9) Environmental conditions while
on visual survey (at beginning and end
of PSO shift and whenever conditions
changed significantly), including
Beaufort sea state and any other relevant
weather conditions including cloud
cover, fog, sun glare, and overall
visibility to the horizon;
(10) Vessel location when
environmental conditions change
significantly;
(11) Factors that may have
contributed to impaired observations
during each PSO shift change or as
needed as environmental conditions
change (e.g., vessel traffic, equipment
malfunctions);
(12) Survey activity information, such
as acoustic source power output while
in operation, number and volume of
airguns operating in an array, tow depth
of an acoustic source, and any other
notes of significance (i.e., pre-start
clearance, ramp-up, shutdown, testing,
shooting, ramp-up completion, end of
operations, streamers, etc.); and
(13) Upon visual observation of a
marine mammal, the following
information:
(i) Watch status (sighting made by
PSO on/off effort, opportunistic, crew,
alternate vessel/platform);
(ii) PSO who sighted the animal and
PSO location (including height above
water) at time of sighting;
(iii) Time of sighting;
(iv) Vessel coordinates at time of
sighting;
(v) Water depth;
(vi) Direction of vessel’s travel
(compass direction);
(vii) Speed of the vessel(s) from which
the observation was made;
(viii) Direction of animal’s travel
relative to the vessel;
(ix) Pace of the animal;
(x) Estimated distance to the animal
(and method of estimating distance) and
its heading relative to vessel at initial
sighting;
(xi) Identification of the animal (e.g.,
genus/species, lowest possible
taxonomic level, or unidentified), PSO
confidence in identification, and the
composition of the group if there is a
mix of species;
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(xii) Estimated number of animals
(high/low/best);
(xiii) Estimated number of animals by
cohort (adults, juveniles, group
composition, etc.);
(xiv) Description (as many
distinguishing features as possible of
each individual seen, including length,
shape, color, pattern, scars or markings,
shape and size of dorsal fin, shape of
head, and blow characteristics);
(xv) Detailed behavior observations
(e.g., number of blows/breaths, number
of surfaces, breaching, spyhopping,
diving, feeding, traveling; as explicit
and detailed as possible; note any
observed changes in behavior),
including an assessment of behavioral
responses to survey activity;
(xvi) Animal’s closest point of
approach (CPA) and/or closest distance
from any element of the acoustic source;
(xvii) Platform activity at time of
sighting (e.g., deploying, recovering,
testing, shooting, data acquisition,
other); and
(xviii) Description of any actions
implemented in response to the sighting
(e.g., delays, shutdown, ramp-up) and
time and location of the action.
(12) Upon acoustic detection of a
marine mammal using a PAM system,
the following information:
(i) An acoustic encounter
identification number, and whether the
detection was linked with a visual
sighting;
(ii) Date and time when first and last
heard;
(iii) Types and nature of sounds heard
(e.g., clicks, whistles, creaks, burst
pulses, continuous, sporadic, strength of
signal); and
(iv) Any additional information
recorded such as water depth of the
hydrophone array, bearing of the animal
to the vessel (if determinable), species
or taxonomic group (if determinable),
spectrogram screenshot, and any other
notable information.
(d) Reporting. (1) Annual reporting
must be submitted as specified in this
paragraph.
(i) LOA-holders must submit a
summary report to NMFS on all
activities and monitoring results within
90 days of the completion of the survey
or expiration of the LOA, whichever
comes sooner, and must include all
information described above under
§ 217.185(c). If an issued LOA is valid
for greater than one year, the summary
report must be submitted on an annual
basis.
(ii) The report must describe activities
conducted and sightings of marine
mammals, must provide full
documentation of methods, results, and
interpretation pertaining to all
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monitoring, and must summarize the
dates and locations of survey operations
and all marine mammal sightings (dates,
times, locations, activities, associated
survey activities, and information
regarding locations where the acoustic
source was used). In addition to the
report, all raw observational data must
be made available to NMFS.
(iii) For operations requiring the use
of PAM, the report must include a
validation document concerning the use
of PAM, which should include
necessary noise validation diagrams and
demonstrate whether background noise
levels on the PAM deployment limited
achievement of the planned detection
goals. Copies of any vessel self-noise
assessment reports must be included
with the report.
(iv) The LOA-holder must provide
geo-referenced time-stamped vessel
tracklines for all time periods in which
airguns (full array or single) were
operating. Tracklines must include
points recording any change in airgun
status (e.g., when the airguns began
operating, when they were turned off).
GIS files must be provided in ESRI
shapefile format and include the UTC
date and time, latitude in decimal
degrees, and longitude in decimal
degrees. All coordinates must be
referenced to the WGS84 geographic
coordinate system.
(v) The draft report must be
accompanied by a certification from the
lead PSO as to the accuracy of the
report, and the lead PSO may submit
directly to NMFS a statement
concerning implementation and
effectiveness of the required mitigation
and monitoring.
(vi) A final report must be submitted
within 30 days following resolution of
any comments on the draft report.
(2) Comprehensive reporting must be
submitted as specified in this paragraph.
LOA-holders must contribute to the
compilation and analysis of data for
inclusion in an annual synthesis report
addressing all data collected and
reported through annual reporting in
each calendar year. The synthesis
period shall include all annual reports
deemed to be final by NMFS in a given
one-year reporting period. The report
must be submitted to NMFS within 90
days following the end of a given oneyear reporting period.
(e) Reporting of injured or dead
marine mammals. (1) In the event that
personnel involved in the survey
activities discover an injured or dead
marine mammal, the LOA-holder must
report the incident to the Office of
Protected Resources (OPR), NMFS and
to the Southeast Regional Stranding
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5449
Network as soon as feasible. The report
must include the following information:
(i) Time, date, and location (latitude/
longitude) of the first discovery (and
updated location information if known
and applicable);
(ii) Species identification (if known)
or description of the animal(s) involved;
(iii) Condition of the animal(s)
(including carcass condition if the
animal is dead);
(iv) Observed behaviors of the
animal(s), if alive;
(v) If available, photographs or video
footage of the animal(s); and
(vi) General circumstances under
which the animal was discovered.
(2) In the event of a ship strike of a
marine mammal by any vessel involved
in the survey activities, the LOA-holder
must report the incident to OPR, NMFS
and to the Southeast Regional Stranding
Network as soon as feasible. The report
must include the following information:
(i) Time, date, and location (latitude/
longitude) of the incident;
(ii) Species identification (if known)
or description of the animal(s) involved;
(iii) Vessel’s speed during and leading
up to the incident;
(iv) Vessel’s course/heading and what
operations were being conducted (if
applicable);
(v) Status of all sound sources in use;
(vi) Description of avoidance
measures/requirements that were in
place at the time of the strike and what
additional measures were taken, if any,
to avoid strike;
(vii) Environmental conditions (e.g.,
wind speed and direction, Beaufort sea
state, cloud cover, visibility)
immediately preceding the strike;
(viii) Estimated size and length of
animal that was struck;
(ix) Description of the behavior of the
marine mammal immediately preceding
and following the strike;
(x) If available, description of the
presence and behavior of any other
marine mammals immediately
preceding the strike;
(xi) Estimated fate of the animal (e.g.,
dead, injured but alive, injured and
moving, blood or tissue observed in the
water, status unknown, disappeared);
and
(xii) To the extent practicable,
photographs or video footage of the
animal(s).
(3) For deep penetration surveys, in
the event of a live stranding (or nearshore atypical milling) event within 50
km of the survey operations, where the
NMFS stranding network is engaged in
herding or other interventions to return
animals to the water, the Director of
OPR, NMFS (or designee) will advise
the LOA-holder of the need to
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implement shutdown procedures for all
active acoustic sources operating within
50 km of the stranding. Shutdown
procedures for live stranding or milling
marine mammals include the following:
(i) If at any time, the marine
mammal(s) die or are euthanized, or if
herding/intervention efforts are stopped,
the Director of OPR, NMFS (or designee)
will advise the LOA-holder that the
shutdown around the animals’ location
is no longer needed.
(ii) Otherwise, shutdown procedures
will remain in effect until the Director
of OPR, NMFS (or designee) determines
and advises the LOA-holder that all live
animals involved have left the area
(either of their own volition or following
an intervention).
(iii) If further observations of the
marine mammals indicate the potential
for re-stranding, additional coordination
with the LOA-holder will be required to
determine what measures are necessary
to minimize that likelihood (e.g.,
extending the shutdown or moving
operations farther away) and to
implement those measures as
appropriate.
(4) If NMFS determines that the
circumstances of any marine mammal
stranding found in the vicinity of the
activity suggest investigation of the
association with survey activities is
warranted, and an investigation into the
stranding is being pursued, NMFS will
submit a written request to the LOAholder indicating that the following
initial available information must be
provided as soon as possible, but no
later than 7 business days after the
request for information. In the event that
the investigation is still inconclusive,
the investigation of the association of
the survey activities is still warranted,
and the investigation is still being
pursued, NMFS may provide additional
information requests, in writing,
regarding the nature and location of
survey operations prior to the time
period above.
(i) Status of all sound source use in
the 48 hours preceding the estimated
time of stranding and within 50 km of
the discovery/notification of the
stranding by NMFS; and
(ii) If available, description of the
behavior of any marine mammal(s)
observed preceding (i.e., within 48
hours and 50 km) and immediately after
the discovery of the stranding.
§ 217.186
Letters of Authorization.
(a) To incidentally take marine
mammals pursuant to these regulations,
prospective LOA-holders must apply for
and obtain an LOA.
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(b) An LOA, unless suspended or
revoked, may be effective for a period
not to exceed the expiration date of
these regulations.
(c) In the event of projected changes
to the activity or to mitigation and
monitoring measures required by an
LOA, the LOA-holder must apply for
and obtain a modification of the LOA as
described in § 217.187.
(d) The LOA shall set forth:
(1) Permissible methods of incidental
taking;
(2) Means of effecting the least
practicable adverse impact (i.e.,
mitigation) on the species or stock and
its habitat; and
(3) Requirements for monitoring and
reporting.
(e) Issuance of the LOA shall be based
on a determination that the level of
taking will be consistent with the
findings made for the total taking
allowable under these regulations and a
determination that the amount of take
authorized under the LOA is of no more
than small numbers.
(f) For LOA issuance, where either (1)
the conclusions put forth in an
application (e.g., take estimates) are
based on analytical methods that differ
substantively from those used in the
development of the rule, or (2) the
proposed activity or anticipated impacts
vary substantively in scope or nature
from those analyzed for the rule, NMFS
may publish a notice of proposed LOA
in the Federal Register, including the
associated analysis of the differences,
and solicit public comment before
making a decision regarding issuance of
the LOA.
(g) Notice of issuance or denial of an
LOA shall be published in the Federal
Register within thirty days of a
determination.
§ 217.187 Renewals and modifications of
Letters of Authorization (LOA).
(a) An LOA issued under § 216.106 of
this chapter and § 217.186 for the
activity identified in § 217.180 shall be
modified upon request by the applicant,
provided that:
(1) The proposed specified activity
and mitigation, monitoring, and
reporting measures, as well as the
anticipated impacts, are the same as
those described and analyzed for these
regulations (excluding changes made
pursuant to the adaptive management
provision in paragraph (c)(1) of this
section); and
(2) NMFS determines that the
mitigation, monitoring, and reporting
measures required by the previous LOA
under these regulations were
implemented.
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(b) For LOA modification requests by
the applicant that include changes to
the activity or the mitigation,
monitoring, or reporting (excluding
changes made pursuant to the adaptive
management provision in paragraph
(c)(1) of this section) that result in more
than a minor change in the total
estimated number of takes (or
distribution by species or years), NMFS
may publish a notice of proposed LOA
in the Federal Register, including the
associated analysis of the change, and
solicit public comment before issuing
the LOA.
(c) An LOA issued under § 216.106 of
this chapter and § 217.186 for the
activity identified in § 217.180 may be
modified by NMFS under the following
circumstances:
(1) NMFS may modify (including
adding or removing measures) the
existing mitigation, monitoring, or
reporting measures (after consulting
with the LOA-holder regarding the
practicability of the modifications) if
doing so is practicable and creates a
reasonable likelihood of more
effectively accomplishing the goals of
the mitigation and monitoring set forth
in the preamble for these regulations;
(i) Possible sources of data that could
contribute to the decision to modify the
mitigation, monitoring, or reporting
measures in an LOA:
(A) Results from monitoring from
previous years;
(B) Results from other marine
mammal and/or sound research or
studies; and
(C) Any information that reveals
marine mammals may have been taken
in a manner, extent or number not
authorized by these regulations or
subsequent LOAs.
(ii) If, through adaptive management,
the modifications to the mitigation,
monitoring, or reporting measures are
substantial, NMFS will publish a notice
of proposed LOA in the Federal
Register and solicit public comment.
(2) If NMFS determines that an
emergency exists that poses a significant
risk to the well-being of the species or
stocks of marine mammals specified in
an LOA issued pursuant to § 216.106 of
this chapter and § 217.186, an LOA may
be modified without prior notice or
opportunity for public comment. Notice
would be published in the Federal
Register within thirty days of the action.
§§ 217.188–217.189
[Reserved]
[FR Doc. 2020–27252 Filed 1–15–21; 8:45 am]
BILLING CODE 3510–22–P
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]]>Agencies
[Federal Register Volume 86, Number 11 (Tuesday, January 19, 2021)]
[Rules and Regulations]
[Pages 5322-5450]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2020-27252]
[[Page 5321]]
Vol. 86
Tuesday,
No. 11
January 19, 2021
Part II
Department of Commerce
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National Oceanic and Atmospheric Administration
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50 CFR Part 217
Taking and Importing Marine Mammals; Taking Marine Mammals Incidental
to Geophysical Surveys Related to Oil and Gas Activities in the Gulf of
Mexico; Final Rule
Federal Register / Vol. 86 , No. 11 / Tuesday, January 19, 2021 /
Rules and Regulations
[[Page 5322]]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
50 CFR Part 217
[Docket No. 201204-0326]
RIN 0648-BB38
Taking and Importing Marine Mammals; Taking Marine Mammals
Incidental to Geophysical Surveys Related to Oil and Gas Activities in
the Gulf of Mexico
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Final rule.
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SUMMARY: NMFS, upon request from the Bureau of Ocean Energy Management
(BOEM), hereby issues regulations to govern the unintentional taking of
marine mammals incidental to geophysical survey activities conducted by
oil and gas industry operators, and those persons authorized to conduct
activities on their behalf (collectively ``industry operators''), in
Federal waters of the U.S. Gulf of Mexico (GOM) over the course of five
years. These regulations, which allow for the issuance of Letters of
Authorization (LOA) to industry operators for the incidental take of
marine mammals during the described activities and specified timeframe,
prescribe the permissible methods of taking and other means of
effecting the least practicable adverse impact on marine mammal species
or stocks and their habitat, as well as requirements pertaining to the
monitoring and reporting of such taking.
DATES: Effective from April 19, 2021 through April 19, 2026.
ADDRESSES: Electronic copies of the application and supporting
documents, as well as a list of the references cited in this document,
may be obtained online at: www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-gulf-mexico. In case of problems accessing these documents, please call
the contact listed below.
FOR FURTHER INFORMATION CONTACT: Ben Laws, Office of Protected
Resources, NMFS, (301) 427-8401.
SUPPLEMENTARY INFORMATION:
Purpose and Need for Regulatory Action
These incidental take regulations (ITR) establish a framework under
the authority of the MMPA (16 U.S.C. 1361 et seq.) to allow for the
authorization of take of marine mammals incidental to the conduct of
geophysical survey activities in the GOM. We received a petition from
BOEM requesting the regulations. Subsequent LOAs may be requested by
industry operators. Take is expected to occur by Level A and/or Level B
harassment incidental to use of active acoustic sound sources. Please
see the Background section below for definitions of harassment.
Legal Authority for the Action
Section 101(a)(5)(A) of the MMPA (16 U.S.C. 1371(a)(5)(A)) directs
the Secretary of Commerce to allow, upon request, the incidental, but
not intentional, taking of small numbers of marine mammals by U.S.
citizens who engage in a specified activity (other than commercial
fishing) within a specified geographical region for up to five years
if, after notice and public comment, the agency makes certain findings
and issues regulations that set forth permissible methods of taking
pursuant to that activity and other means of effecting the ``least
practicable adverse impact'' on the affected species or stocks and
their habitat (see the discussion below in the Mitigation section), as
well as monitoring and reporting requirements. Section 101(a)(5)(A) of
the MMPA and the implementing regulations at 50 CFR part 216, subpart
I, provide the legal basis for issuing this rule containing the
regulations, and for any subsequent LOAs. As directed by this legal
authority, the regulations contain mitigation, monitoring, and
reporting requirements.
Summary of Major Provisions Within the Regulations
Following is a summary of the major provisions of these regulations
regarding geophysical survey activities. These measures include:
Standard detection-based mitigation measures, including
use of visual and acoustic observation to detect marine mammals and
shut down acoustic sources in certain circumstances;
A time-area restriction designed to avoid effects to
bottlenose dolphins in times and places believed to be of particular
importance;
Vessel strike avoidance measures; and
Monitoring and reporting requirements.
These incidental take regulations govern and allow for the
subsequent issuance of letters of authorization for the take of marine
mammals incidental to the specified activity described in this Notice,
within the upper bounds of take that was evaluated for this rule, and
prescribe measures for mitigation, monitoring, and reporting. They do
not preclude a U.S. citizen from applying for an incidental take
authorization for a specified activity with different parameters or
required measures through a separate request and process.
Background
Section 101(a)(5)(A) of the MMPA (16 U.S.C. 1361 et seq.) directs
the Secretary of Commerce (as delegated to NMFS) to allow, upon
request, the incidental, but not intentional, taking of small numbers
of marine mammals by U.S. citizens who engage in a specified activity
(other than commercial fishing) within a specified geographical region
if certain findings are made, regulations are issued, and notice is
provided to the public.
An authorization for incidental taking shall be granted if NMFS
finds that the taking will have a negligible impact on the species or
stock(s) and will not have an unmitigable adverse impact on the
availability of the species or stock(s) for subsistence uses (where
relevant), and if the permissible methods of taking and requirements
pertaining to the mitigation, monitoring, and reporting of such takings
are set forth.
NMFS has defined ``negligible impact'' in 50 CFR 216.103 as an
impact resulting from the specified activity that cannot be reasonably
expected to, and is not reasonably likely to, adversely affect the
species or stock through effects on annual rates of recruitment or
survival.
The MMPA states that the term ``take'' means to harass, hunt,
capture, or kill, or attempt to harass, hunt, capture, or kill, any
marine mammal.
Except with respect to certain activities not pertinent here, the
MMPA defines ``harassment'' as: Any act of pursuit, torment, or
annoyance which (i) has the potential to injure a marine mammal or
marine mammal stock in the wild (Level A harassment); or (ii) has the
potential to disturb a marine mammal or marine mammal stock in the wild
by causing disruption of behavioral patterns, including, but not
limited to, migration, breathing, nursing, breeding, feeding, or
sheltering (Level B harassment).
Summary of Request
On October 17, 2016, BOEM submitted a revised petition \1\ to NMFS
for rulemaking under section 101(a)(5)(A) of the MMPA to authorize take
of marine mammals incidental to conducting geophysical surveys during
[[Page 5323]]
oil and gas industry exploration and development activities in the GOM.
This revised petition was deemed adequate and complete based on NMFS'
implementing regulations at 50 CFR 216.104.
---------------------------------------------------------------------------
\1\ In the notice of proposed rulemaking (83 FR 29212; June 22,
2018), NMFS provided a brief history of prior petitions received
from BOEM's predecessor agencies.
---------------------------------------------------------------------------
On December 8, 2016 (81 FR 88664), we published a notice of receipt
of the petition in the Federal Register, requesting comments and
information related to the request. This 30-day comment period was
extended to January 23, 2017 (81 FR 92788), for a total review period
of 45 days. The comments and information received during this public
review period informed development of the proposed ITR, and all
comments received are available online at www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-gulf-mexico.
In August 2017, BOEM produced a final Programmatic Environmental
Impact Statement (PEIS) to evaluate potential significant environmental
effects of geological and geophysical (G&G) activities on the Outer
Continental Shelf (OCS) of the GOM, pursuant to the National
Environmental Policy Act (NEPA). The PEIS is available online at:
www.boem.gov/Gulf-of-Mexico-Geological-and-Geophysical-Activities-Programmatic-EIS/. NOAA participated as a cooperating agency in the
development of the PEIS.
NMFS published a notice of proposed rulemaking in the Federal
Register for a 60-day public review on June 22, 2018 (83 FR 29212). The
comments and information received during this public review period
informed development of the final ITR, and NMFS has responded to all
comments received (see Comments and Responses).
On February 24, 2020, BOEM submitted a notice to NMFS of its
``updated proposed action and action area for the ongoing [ITR]
process[.]'' This update consisted of removal of the area currently
under a Congressional leasing moratorium under the Gulf of Mexico
Energy Security Act (GOMESA) (Pub. L. 109-432, Sec. 104) from
consideration in the ITR. BOEM stated in its notice to NMFS that G&G
activities are not likely to be proposed within the area subject to the
leasing moratorium during the 5-year period of effectiveness for the
ITR and, therefore, that the ``number, type, and effects of any such
proposed G&G activities are simply too speculative and uncertain for
BOEM to predict or meaningfully analyze.'' These Congressional leasing
restrictions are in place until June 30, 2022. Based on this updated
scope, BOEM on March 26, 2020, submitted revised projections of
expected activity levels and corresponding changes to modeled acoustic
exposure numbers. BOEM's notice and updated information are available
online at: www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-gulf-mexico. These
changes are addressed as appropriate throughout this final ITR. On
September 8, 2020, the President effectively extended this moratorium
through withdrawal under the Outer Continental Shelf Lands Act (OCSLA)
of the same area covered by the GOMESA moratorium from disposition by
leasing for 10 years, beginning on July 1, 2022, and ending on June 30,
2032.
Geophysical surveys are conducted in support of hydrocarbon
exploration and development in the GOM, typically by companies that
provide such services to the oil and gas industry. Broadly, these
surveys include (1) deep penetration surveys using large airgun arrays
as the acoustic source; (2) shallow penetration surveys using a small
airgun array, single airgun, or similar systems as the acoustic source;
and (3) high-resolution surveys, which may use a variety of acoustic
sources. Generally speaking, these surveys may occur within Federal
territorial waters and waters of the U.S. Exclusive Economic Zone (EEZ)
(i.e., to 200 nautical miles (nmi)) within the GOM, and corresponding
with BOEM's GOM OCS planning areas (i.e., Western Planning Area (WPA),
Central Planning Area (CPA), Eastern Planning Area (EPA)). The use of
these acoustic sources is expected to produce underwater sound at
levels that have the potential to result in harassment of marine
mammals. Cetacean species with the potential to be present in the GOM
are described below (see Table 4).
These regulations establish a framework under the authority of the
MMPA (16 U.S.C. 1361 et seq.) and NMFS' implementing regulations (50
CFR 216.101 et seq.) to allow for the authorization, through LOAs, of
take of marine mammals incidental to the conduct of geophysical surveys
for oil and gas activities in the GOM. The regulations are effective
for five years.
Description of the Specified Activity
Overview
The specified activity consists of geophysical surveys conducted by
industry operators for a variety of reasons related to hydrocarbon
exploration, development, and production. These operators are typically
companies that provide geophysical services, such as data acquisition
and processing, to the oil and gas industry, including exploration and
production companies. The petition describes a five-year period of
geophysical survey activity and provides estimates of the amount of
effort by survey type and location. BOEM's PEIS (BOEM, 2017) describes
a range of potential survey effort. The levels of effort in the
petition (which form the basis for the modeling effort described later
in the Estimated Take section) were the high-end estimates. Following
BOEM's update of the petition's geographic scope, these estimates were
revised accordingly. Actual total amounts of effort (including by
survey type and location) would not be known in advance of receiving
LOA requests from industry operators, but take in excess of what is
analyzed for this rulemaking would not be authorized. As noted above,
BOEM has updated the scope of the specified activity/specified
geographical region by removing the area currently under leasing
moratorium through GOMESA from consideration. The removed area largely
covers the EPA, including areas in which NMFS had proposed time-area
restrictions as mitigation, but also includes a portion of the CPA.
Applicants seeking authorization for take of marine mammals incidental
to survey activities within the GOMESA area during the 5-year period of
effectiveness for this rule will need to pursue a separate MMPA
incidental take authorization. See Figures 1 and 2.
Geophysical surveys are conducted to obtain information on marine
seabed and subsurface geology for a variety of reasons, including to:
(1) Obtain data for hydrocarbon and mineral exploration and production;
(2) aid in siting of oil and gas structures, facilities, and pipelines;
(3) identify possible seafloor or shallow depth geologic hazards; and
(4) locate potential archaeological resources and benthic habitats that
should be avoided. In addition, geophysical survey data inform Federal
government decisions. For example, BOEM uses such data for resource
estimation and bid evaluation to ensure that the government receives a
fair market value for OCS leases, as well as to help to evaluate worst-
case discharge for potential oil-spill analysis and to evaluate sites
for potential hazards prior to drilling.
Deep penetration seismic surveys using airgun arrays as an acoustic
source (sound sources are described in the ``Detailed Description of
Activities'' section) are a primary method of obtaining geophysical
data used to characterize subsurface structure. These surveys are
designed to illuminate
[[Page 5324]]
deeper subsurface structures and formations that may be of economic
interest as a reservoir for oil and gas exploitation. A deep
penetration survey uses an acoustic source suited to provide data on
geological formations that may be thousands of meters (m) beneath the
seafloor, as compared with a shallow penetration or high resolution
geophysical (HRG) survey that may be intended to evaluate shallow
subsurface formations or the seafloor itself (e.g., for hazards).
Deep penetration surveys may be two-dimensional (2D) or three-
dimensional (3D) (see Figure 1-2 of the petition), and there are a
variety of survey methodologies designed to provide the specific data
of interest. 2D surveys are designed to acquire data over large areas
(thousands of square miles) in order to screen for potential
hydrocarbon prospectivity, and provide a cross-sectional image of the
structure. In contrast, 3D surveys may use similar acoustic sources but
are designed to cover smaller areas with greater resolution (e.g., with
closer survey line spacing), providing a volumetric image of underlying
geological structures. Repeated 3D surveys are referred to as four-
dimensional (4D), or time-lapse, surveys that assess the depletion of a
reservoir.
Shallow penetration and high-resolution surveys are designed to
highlight seabed and near-surface potential obstructions, archaeology,
and geohazards that may have safety implications during rig
installation or well and development facility siting. Shallow
penetration surveys may use a small airgun array, single airgun, or
similar sources, while high-resolution surveys (which are limited to
imaging the seafloor itself) may use a variety of sources, such as sub-
bottom profilers, single or multibeam echosounders, or side-scan
sonars.
Dates and Duration
The specified activities may occur at any time during the five-year
period of validity of these regulations. Actual dates and duration of
individual surveys are not known. Survey activities are generally 24-
hour operations. However, BOEM estimates that a typical seismic survey
involves approximately 20 to 30 percent of non-operational downtime due
to a variety of factors, including technical or mechanical problems,
standby for weather or other interferences, and implementation of
mitigation measures.
Specified Geographical Region
The OCS planning areas are depicted in Figure 1, and the overlap of
the GOMESA moratorium area with the planning areas (as well as with the
modeling zones, see discussion of modeling zones below) is depicted in
Figure 2, showing the updated specified geographical region.
Only the northern portion of the GOM contains Federal waters. BOEM
manages development of U.S. Federal OCS energy and mineral resources
within OCS regions, which are divided into planning areas. Within
planning areas are lease blocks, on which specific production
activities may occur. Geophysical survey activities may occur on scales
ranging from entire planning areas to multiple or specific lease
blocks, or could occur at specific potential or existing facilities
within a lease block. NMFS provided a detailed discussion of the
specified geographical region in the notice of proposed rulemaking (83
FR 29212; June 22, 2018).
The prospective survey activities may occur in the U.S. waters of
the GOM, within BOEM's Western, Central, and Eastern GOM OCS planning
areas (approximately within the U.S. EEZ; Figure 1), but excluding the
GOMESA moratorium area (Figure 2). Although survey activity in the
GOMESA moratorium area is no longer being considered, the region has
not changed compared with what was described, nor has substantive new
information regarding the region become available. Therefore, we do not
reprint that discussion here and refer the reader to that notice of
proposed rulemaking for additional detail.
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Detailed Description of Activities
An airgun is a device used to emit acoustic energy pulses into the
seafloor, and generally consists of a steel cylinder that is charged
with high-pressure air. There are different types of airguns;
differences between types of airguns are generally in the mechanical
parts that release the pressurized air, and the bubble and acoustic
energy released are effectively the same. Airguns are typically
operated at a firing pressure of 2,000 pounds per square inch (psi).
Release of the compressed air into the water column generates a signal
that reflects (or refracts) off the seafloor and/or subsurface layers
having acoustic impedance contrast. Individual airguns are available in
different volumetric sizes and, for deep penetration seismic surveys,
are towed in arrays (i.e., a certain number of airguns of varying sizes
in a certain arrangement) designed according to a given company's
method of data acquisition, seismic target, and data processing
capabilities.
Airgun arrays are typically configured in subarrays of 6-12 airguns
each. Towed hydrophone streamers (described below) may follow the array
by 100-200 m and can be 5-12 kilometer (km) long. The airgun array and
streamers are typically towed at a speed of approximately 4.5 to 5
knots (kn). BOEM notes that arrays used for deep penetration surveys
typically have between 20-80 individual elements, with a total volume
of 1,500-8,460 in\3\. The output of an airgun array is directly
proportional to airgun firing pressure or to the number of airguns, and
is expressed as the cube root of the total volume of the array.
Airguns are considered to be low-frequency acoustic sources,
producing sound with energy in a frequency range from less than 10 Hz
to 2 kHz (though there may be energy at higher frequencies), with most
energy radiated at frequencies below 500 Hz. Frequencies of interest to
industry are below approximately 100 Hz. The amplitude of the acoustic
wave emitted from the source is equal in all directions (i.e.,
omnidirectional) for a single airgun, but airgun arrays do possess some
directionality due to phase delays between guns in different
directions. Airgun arrays are typically tuned to maximize functionality
for data acquisition purposes, meaning that sound transmitted in
horizontal directions and at higher frequencies is minimized to the
extent possible.
When fired, a brief (~0.1 second) pulse of sound is emitted by all
airguns in an array nearly simultaneously, in order to increase the
amplitude of the overall source pressure signal. The combined signal
amplitude and directivity is dependent on the number and sizes of
individual airguns and their geometric positions within the array. The
airguns are silent during the intervening periods, with the array
typically fired on a fixed distance (or shot point) interval. The
intervals are optimized for water depth and the distance of important
geological features below seafloor, but a typical interval in
relatively deep water might be approximately every 10-20 seconds (or
25-50 m, depending on vessel speed). The return signal is recorded by a
listening device, and later analyzed with computer interpretation and
mapping systems used to depict the subsurface. There must be enough
time between shots for the sound signals to propagate down to and
reflect from the feature of interest, and then to propagate upward to
be received on hydrophones or geophones. Reverberation of sound from
previous shots must also be given time to dissipate. The receiving
hydrophones can be towed behind or in front of the airgun array (may be
towed from the source vessel or from a separate receiver vessel), or
geophone receivers can be deployed on the seabed. Receivers may be
displaced several kilometers horizontally away from the source, so
horizontal propagation time is also
[[Page 5327]]
considered in setting the interval between shots.
Sound levels for airgun arrays are typically modeled or measured at
some distance from the source and a nominal source level then back-
calculated. Because these arrays constitute a distributed acoustic
source rather than a single point source (i.e., the ``source'' is
actually comprised of multiple sources with some predetermined spatial
arrangement), the highest sound levels measurable at any location in
the water will be less than the nominal source level. A common analogy
is to an array of light bulbs; at sufficient distance--in the far
field--the array will appear to be a single point source of light but
individual sources, each with less intensity than that of the whole,
may be discerned at closer distances (Caldwell and Dragoset (2000)
define the far field as greater than 250 m). Therefore, back-calculated
source levels are not typically considered to be accurate indicators of
the true maximum amplitude of the output in the far field, which is
what is typically of concern in assessing potential impacts to marine
mammals. In addition, the effective source level for sound propagating
in near-horizontal directions (i.e., directions likely to impact most
marine mammals in the vicinity of an array) is likely to be
substantially lower (e.g., 15-24 decibels (dB); Caldwell and Dragoset,
2000) than the nominal source level applicable to downward propagation
because of the directional nature of the sound from the airgun array.
The horizontal propagation of sound is reduced by noise cancellation
effects created when sound from neighboring airguns on the same
horizontal plane partially cancel each other out.
Survey protocols generally involve a predetermined set of survey,
or track, lines. The seismic acquisition vessel(s) (source vessel) will
travel down a linear track for some distance until a line of data is
acquired, then turn and acquire data on a different track. In some
cases, data is acquired as the source vessel(s) turns continuously
rather than moving on a linear track (i.e., coil surveys). The spacing
between track lines and the length of track lines can vary greatly,
depending on the objectives of a survey. In addition to the line over
which data acquisition is desired, full-power operation may include
run-in and run-out. Run-in is approximately 1 km of full-power source
operation before starting a new line to ensure equipment is functioning
properly, and run-out is additional full-power operation beyond the
conclusion of a trackline (e.g., half the distance of the acquisition
streamer behind the source vessel, when used) to ensure that all data
along the trackline are collected by the streamer. Line turns can
require two to six hours when towed hydrophones are used, due to the
long trailing streamers, but may be much faster when streamers are not
used. Spacing and length of tracks varies by survey. Survey operations
often involve the source vessel(s), supported by a chase vessel. Chase
vessels typically support the source vessel(s) by protecting the long
hydrophone streamer (when used) from damage (e.g., from other vessels)
and otherwise lending logistical support (e.g., returning to port for
fuel, supplies, or any necessary personnel transfers). Chase vessels do
not deploy acoustic sources for data acquisition purposes; the only
potential effects of the chase vessels are those associated with normal
vessel operations.
The general activities described here could occur pre- or post-
leasing and/or on- or off-lease. Pre-lease surveys are more likely to
involve larger-scale activity designed to explore or evaluate geologic
formations. Post-lease activities may also include deep penetration
surveys, but would be expected to be smaller in spatial and temporal
scale as they are associated with specific leased blocks. Shallow
penetration and HRG surveys are more likely to be associated with
specific leased blocks and/or facilities, with HRG surveys used along
pipeline routes and to search for archaeological resources and/or
benthic communities. Specific types of surveys, including 2D and 3D
surveys and various survey geometries typically associated with 3D
surveys (e.g., narrow- and wide-azimuth (NAZ and WAZ) and coil
surveys), were described in summary in the notice of proposed
rulemaking (83 FR 29212; June 22, 2018). We also described surveys
involving the placement of seismic sensors in a drilled well or
borehole, including various types of vertical seismic profiling and
other types of borehole seismic surveys. For full detail, please refer
to that notice or sections 1.2 and 1.3 of BOEM's petition.
Surveys may be designed as either multi-source (i.e., multiple
arrays towed by one or more source vessel(s)) or single source. Surveys
may also be differentiated by the way in which they record the return
signals using hydrophones and/or geophones. Hydrophones may be towed in
streamers behind a vessel (either the source vessel(s) or a separate
vessel) or in some cases may be placed in boreholes (called vertical
seismic profiling) or spaced at various depths on vertical cables in
the water column. Sensors may also be incorporated into ocean-bottom
cables (OBC) or autonomous ocean-bottom nodes (OBN) and placed on the
seafloor--these surveys are referred to generally as ocean-bottom
seismic (OBS). Autonomous nodes can be tethered to coated lines and
deployed from ships or remotely-operated vehicles, with current
technology allowing use in water depths to approximately 3,000 m. OBS
surveys are most useful to acquire data in shallow water and obstructed
areas, as well as for acquisition of four-component survey data (i.e.,
including pressure and 3D linear acceleration collected via geophone).
For OBS surveys, one or two vessels usually are needed to lay out and
pick up cables, one ship is needed to record data, one ship tows an
airgun array, and two smaller utility boats support survey operations.
In summary, 3D survey design involves a vessel with one or more
acoustic sources covering an area of interest with relatively tight
spatial configuration (compared with 2D surveys). In order to provide
richer, more useful data, particularly in areas with more difficult
geology, survey designs become more complicated with additional source
and/or receiver vessels operating in potentially increasingly
complicated choreographies.
As compared with 2D and 3D deep penetration surveys, shallow
penetration and HRG surveys are conducted to provide data informing
initial site evaluation, drilling rig emplacement, and platform or
pipeline design and emplacement. Identification of geohazards (e.g.,
gas hydrates, buried channels) is necessary to avoid drilling and
facilities emplacement problems, and operators are required to identify
and avoid archaeological resources and certain benthic communities.
These surveys may use single airguns or small airgun arrays, but
generally use various types of electromechanical acoustic sources.
Please see our notice of proposed rulemaking or BOEM's petition for
additional detail regarding these survey types and electromechanical
acoustic sources.
Summary of Representative Sound Sources
Because the specifics of acoustic sources to be used cannot be
known in advance of receiving LOA requests from industry operators, it
was necessary to define representative acoustic source parameters, as
well as representative survey patterns. BOEM determined realistic
representative proxy sound sources and survey patterns, which were used
in acoustic exposure
[[Page 5328]]
modeling and more broadly to support the analysis, after discussions
with individual geophysical companies. Acoustic exposure modeling is
described in detail in ``Acoustic Propagation and Marine Mammal
Exposure Modeling of Geological and Geophysical Sources in the Gulf of
Mexico'' and ``Addendum to Acoustic Propagation and Marine Mammal
Exposure Modeling of Geological and Geophysical Sources in the Gulf of
Mexico'' (Zeddies et al., 2015, 2017a), hereafter referred to
collectively as ``the modeling report,'' as well as in ``Gulf of Mexico
Acoustic Exposure Model Variable Analysis'' (Zeddies et al., 2017b),
which evaluated a smaller, alternative airgun array. The reports are
available online at: www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-gulf-mexico.
Representative sources for the modeling include a single airgun, an
airgun array, and multiple electromechanical sources. Two major survey
types were considered: Large-area seismic (including 2D, 3D NAZ, 3D
WAZ, and coil surveys) and small-area, high-resolution geotechnical
(including single airgun surveys and surveys using a CHIRP sub-bottom
profiler in combination with multibeam echosounder and side-scan sonar;
the single airgun was used as a reasonable proxy for surveys using a
boomer). The nominal airgun sources used for analysis of the proposed
action include a small single airgun (90 in\3\ airgun) and a large
airgun array (8,000 in\3\). In addition, the supplemental Model
Variable Analysis (Zeddies et al., 2017b) provides analysis of an
alternative 4,130 in\3\ array (see Letters of Authorization section).
We note that while high-resolution geophysical sources were
conservatively included for consideration in this rule to allow for
take authorization if necessary, some of these types of sources would
not necessarily be expected to cause the incidental take of marine
mammals, depending on the source type and/or the manner in which it is
operated (e.g., operational settings, mitigation measures), and Letters
of Authorization would not be necessary in those cases.
Additional characteristics of the representative acoustic sources
and representative operational parameters of the different survey types
that were used in the modeling simulations to predict the exposure of
marine mammals to different received levels of sound are described in
the modeling report and in our notice of proposed rulemaking. Please
see those documents for additional detail.
We note that while it was necessary to identify representative
sources for the purposes of modeling the number of takes to be included
in the analysis under the rule, the analysis is intended to be, and is
appropriately, applicable to takes resulting from the use of other
sizes or configurations of airguns (e.g., the alternative, smaller
airgun array modeled in the ``Gulf of Mexico Acoustic Exposure Model
Variable Analysis'' report (Zeddies et al., 2017b) referenced in the
proposed rule and available for public review as supplementary material
to the proposed rule).
While these descriptions reflect existing technologies and current
practice, new technologies and/or uses of existing technologies may
come into practice during the period of validity of these regulations.
NMFS will evaluate any such developments on a case-specific basis to
determine whether expected impacts on marine mammals are consistent
with those described or referenced in this document and, therefore,
whether any anticipated take incidental to use of those new
technologies or practices may appropriately be authorized under the
existing regulatory framework. We also note here that activities that
may result in incidental take of marine mammals, and which would
therefore appropriately require authorization under the MMPA, are not
limited to those activities requiring permits from BOEM. There may be
some activities that do not require permits from BOEM, such as certain
ancillary activities, for which an LOA under this rule may be
appropriate. Operators should consult NMFS regarding the
appropriateness of applying for an LOA under this rule prior to
conducting such activities.
Estimated Levels of Effort
As noted previously, actual total amounts of effort by survey type
and location cannot be known in advance of receiving LOA requests from
industry operators. Therefore, BOEM's PEIS provided projections of
survey level of effort for the different survey types for a 10-year
period (and BOEM's updated scope refined those projections to a five-
year period). In order to construct a realistic scenario for future
geophysical survey effort, BOEM evaluated trends in permit applications
as well as industry estimates of future survey activity. In addition,
GOMESA precludes leasing, pre-leasing, or any related activity (though
not geophysical surveys) in the GOM east of 86[deg]41' W, in BOEM's
Eastern Planning Area (EPA) and within 125 mi (201 km) of Florida, or
in BOEM's Central Planning Area (CPA) and within 100 mi of Florida (and
according to certain other detailed stipulations). These leasing
restrictions are in place until June 30, 2022. On September 8, 2020,
the President effectively extended this moratorium through withdrawal
under OCSLA of the same area covered by the GOMESA moratorium from
disposition by leasing for 10 years, beginning on July 1, 2022, and
ending on June 30, 2032. This withdrawal prevents consideration of
these areas for any leasing for purposes of exploration, development,
or production during the 10-year period beginning on July 1, 2022, and
ending on June 30, 2032. Although the withdrawal does not preclude
geophysical survey activity, similar to the moratorium under GOMESA,
the lack of leasing opportunities may be expected to curtail interest
in exploratory surveys to some degree.
In order to provide some spatial resolution to the projections of
survey effort and to provide reasonably similar areas within which
acoustic modeling might be conducted, the geographic region was divided
into seven zones, largely on the basis of water depth, seabed slope,
and defined BOEM planning area boundaries. Shelf regions typically
extend from shore to approximately 100-200 m water depths where
bathymetric relief is gradual (off Florida's west coast, the shelf
extends approximately 150 km). The slope starts where the seabed relief
is steeper and extends into deeper water. In the GOM water deepens from
100-200 m to 1,500-2,500 m over as little as a 50 km horizontal
distance. As the slope ends, water depths become more consistent,
though depths can vary from 2,000-3,300 m. Three primary bathymetric
areas were defined as shelf (0-200 m water depth), slope (200-2,000 m),
and deep (>2,000 m).
Available information regarding cetacean density in the GOM (e.g.,
Roberts et al., 2016) shows that, in addition to water depth, animal
distribution tends to vary from east to west in the GOM and appears
correlated with the width of shelf and slope areas from east to west.
The western region is characterized by a relatively narrow shelf and
moderate-width slope. The central region has a moderate-width shelf and
moderate-width slope, and the eastern region has a wide shelf and a
very narrow slope. Therefore, BOEM's western, central, and eastern
planning area divisions provide appropriate longitudinal separations
for the shelf and slope areas. Due to relative consistency in both
physical properties
[[Page 5329]]
and predicted animal distribution, the deep area was not subdivided. As
shown in Figure 3, Zones 1-3 represent the shelf area (from east to
west), Zones 4-6 represent the slope area (from east to west), and Zone
7 is the deep area.
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Table 1 in the notice of proposed rulemaking provided the 10-year
estimated levels of effort from BOEM's PEIS, estimated as 24-hr survey
days, including annual totals by survey type and by zone for deep
penetration and shallow penetration surveys, respectively. As the basis
for the analysis supporting the proposed rulemaking, NMFS selected one
high survey effort scenario and two each of moderate and low survey
effort scenarios from the ten survey effort scenarios provided by BOEM.
Of the ten ``years'' or effort scenarios, Year 1 (high), Years 4 and 5
(moderate), and Years 8 and 9 (low) were selected as representative
effort scenarios and carried forward for further evaluation.
However, as noted previously, BOEM subsequently revised its
proposed action by removing the area subject to leasing moratorium
under GOMESA from consideration in the rule. In support of this
revision, BOEM provided revised 5-year level of effort predictions and
associated acoustic exposure estimates. BOEM's process for developing
this information, described in detail in ``Revised Modeled Exposure
Estimates,'' available online, was straightforward. Rather than using
the PEIS's 10-year period, BOEM provided revised levels of effort for a
5-year period, using Years 1-5 of the original level of effort
projections. BOEM stated that the first five years were selected to be
carried forward ``because they were contiguous, they included the three
years with the most activity, and they were the best understood in
relation to the historical data upon which they are based.'' NMFS
concurs with this choice. Levels of effort were revised based on the
basic assumption that if portions of areas are removed from
consideration, then the corresponding effort previously presumed to
occur in those areas also is removed from consideration. Revised
estimates of future effort and associated acoustic exposures draw upon
the prior projections and modeling approach, which were subject to
notice and comment. Table 1 shows the percentage reduction in survey
area for each modeling zone that results from BOEM's scope revisions,
and Table 2 provides the subsequent revised level of effort projections
for the 5-year period.
Table 1--Percentage Reduction in Survey Area for Each Modeled Zone
------------------------------------------------------------------------
Percentage
Modeling zone reduction in
area
------------------------------------------------------------------------
1....................................................... 100.0
2....................................................... 2.7
3....................................................... 0.0
4....................................................... 98.2
5....................................................... 4.0
6....................................................... 0.0
7....................................................... 33.0
------------------------------------------------------------------------
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Table 2--Projected Levels of Effort in 24-hr Survey Days for Five Years, by Zone and Survey Type \1\
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Shallow Total
Year Zone \2\ 2D \3\ 3D NAZ \3\ 3D WAZ \3\ Coil \3\ VSP \3\ Total hazards Boomer \4\ HRG \4\ (shallow)
(deep) \3\ \4\ \4\
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1........................................................... 1 0 0 0 0 0 0 0 0 1 1
2 0 7 0 0 0 7 0 0 1 1
3 0 0 0 0 0 0 0 0 0 0
4 0 0 0 0 0 0 0 0 0 0
5 2 16 8 3 0 29 0 0 1 1
6 0 0 0 0 0 0 0 0 0 0
7 23 170 82 35 1 311 0 0 11 11
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Total................................................... .......... 25 193 90 38 1 347 0 0 14 14
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2........................................................... 1 0 0 0 0 0 0 0 0 1 1
2 0 10 1 0 0 11 0 0 1 1
3 0 0 0 0 0 0 0 0 0 0
4 27 0 0 0 0 27 0 0 0 0
5 0 16 8 3 0 27 0 0 1 1
6 0 0 0 0 0 0 0 0 0 0
7 10 166 79 34 1 290 0 0 11 11
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Total................................................... .......... 37 192 88 37 1 355 0 0 14 14
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3........................................................... 1 0 0 0 0 0 0 0 0 1 1
2 0 10 1 0 0 11 0 0 0 0
3 0 0 0 0 0 0 0 0 0 0
4 54 50 21 9 0 134 0 0 1 1
5 1 10 4 2 0 17 0 0 1 1
6 0 0 0 0 0 0 0 0 0 0
7 31 125 46 20 1 223 0 0 12 12
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Total................................................... .......... 86 195 72 31 1 385 0 0 12 12
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4........................................................... 1 0 0 0 0 0 0 0 0 0 0
2 0 10 1 0 0 11 0 0 0 0
3 0 0 0 0 0 0 0 0 0 0
4 54 50 21 9 0 134 0 0 1 1
5 1 10 4 2 0 17 0 0 1 1
6 0 0 0 0 0 0 0 0 0 0
7 31 125 46 20 1 223 0 0 12 12
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Total................................................... .......... 86 195 72 31 1 385 0 0 14 14
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
5........................................................... 1 0 0 0 0 0 0 0 0 0 0
2 0 7 0 0 0 7 0 0 1 1
3 0 0 0 0 0 0 0 0 0 0
4 0 75 0 0 0 75 0 0 0 0
5 0 12 8 3 0 23 0 0 1 1
6 0 0 0 0 0 0 0 0 0 0
7 0 154 79 34 1 268 1 1 11 13
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Total................................................... .......... 0 248 87 37 1 373 1 1 13 15
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\1\ Projected levels of effort in 24-hr survey days.
\2\ Zones follow the zones depicted in Figure 3.
\3\ Deep penetration survey types include 2D, which uses one source vessel with one large array (8,000 in\3\); 3D NAZ, which uses two source vessels using one large array each; 3D WAZ and
coil, each of which uses four source vessels using one large array each (but with differing survey design); and VSP, which uses one source vessel with a large array. ``Deep'' refers to
survey type, not to water depth.
\4\ Shallow penetration/HRG survey types include shallow hazards surveys, assumed to use a single 90 in\3\ airgun or boomer, and high-resolution surveys using the multibeam echosounder, side-
scan sonar, and chirp sub-bottom profiler systems concurrently. ``Shallow'' refers to survey type, not to water depth.
This description of the specified activity is a summary of critical
information. The interested reader should refer to the notice of
proposed rulemaking (83 FR 29212; June 22, 2018), as well as BOEM's
petition (with recent addenda) and PEIS, for additional detail
regarding these prospective activities and the region. Required
mitigation, monitoring, and reporting measures are described in detail
later in this document (please see Mitigation and Monitoring and
Reporting).
Changes From the Proposed Rule
This section provides a summary of changes from the proposed rule.
Each section in which changes were made (e.g., Mitigation) includes a
more detailed list of changes made and a fuller description of the
rationale. The following Comments and Responses section also provides
additional detail relating to changes, in cases where the change
resulted from a public comment.
Most notably, as described in greater detail above, BOEM updated
the scope of the specified activity/specified geographical region that
is the subject of this rule by removing from consideration the area
that is subject to the GOMESA leasing moratorium. In accordance with
this updated spatial scope, BOEM provided revised activity level
projections and revised estimated acoustic exposure numbers based on
the same modeling that informed the numbers evaluated in the proposed
rule. BOEM's revised activity level projections correspond with Years
1-5 of the original 10-year projections (see Table 1 of the notice of
proposed rulemaking), which is a conservative choice as these years
contained higher levels of effort than Years 6-10. In the proposed
rule, NMFS selected years that were representative of different levels
of effort as the basis for the total taking over five years, including
one year of relatively high effort (Year 1), two years of relatively
moderate effort (Years 4 and 5), and two years of relatively low effort
(Years 8 and 9). This selection is now in part supplanted (with the two
[[Page 5331]]
representative ``low effort'' years replaced by one relatively high
effort year and one relatively moderate effort year) by BOEM's
selection of Years 1-5 and the associated updated levels of effort.
The revised acoustic exposure numbers form the basis for our
analyses in this final rule. Of note, the maximum total taking, as well
as the annual maximum, that would be allowable under the regulations
has decreased for most species and stocks, with the exception of the
annual maximums for Atlantic spotted dolphin and bottlenose dolphins,
and the total taking over five years for the Atlantic spotted dolphin,
which have increased slightly (please see Estimated Take for additional
information). These changes (largely decreases) in the take numbers do
not have a meaningful effect on the analysis (except where impacts are
significantly reduced, e.g., for Bryde's whales) and do not change any
of the findings.
In the proposed rule, NMFS included several time-area restrictions,
including a seasonal restriction on airgun survey activity in the
``Bryde's whale core habitat'' area (as well as alternatives to this
proposal that were offered for public comment, including a year-round
restriction in the same area). Following BOEM's update to the scope of
the rule, two of these areas (the Bryde's whale area and the ``Dry
Tortugas'' area that was, in part, designed to provide protection for
sperm whales and beaked whales) were removed from consideration, as the
specified activity/specified geographical region no longer includes
surveys in the areas where these proposed restrictions are located.
A third time-area restriction--the ``Coastal Restriction,''
designed to protect bottlenose dolphins in coastal waters most heavily
impacted by the Deepwater Horizon oil spill--has been modified in
consideration of public comments. The restriction was proposed to be
GOM-wide within coastal waters inside the 20-m isobath, and to be in
effect from February through May. The area encompassed by the
restriction has been reduced to match the assumed range of the northern
coastal stock of bottlenose dolphins (i.e., between 90-84[deg] W, but
in effect only to the eastern extent of the coastal waters portion of
BOEM's updated specified geographic region) while the temporal window
has been expanded to include January. In addition, a proposed 13-km
buffer to this area has been removed.
In the proposed rule, NMFS defined ``deep penetration'' surveys as
those using arrays greater than 400 in\3\ total volume. That
delineation has been revised to include surveys using arrays greater
than 1,500 in\3\ total volume, with arrays of 1,500 in\3\ total volume
and less considered ``shallow penetration'' surveys.
In the notice of proposed rulemaking, NMFS proposed an exception to
the general shutdown requirements for certain species of dolphins in
relation to airgun surveys, in which the acoustic source would be
powered down to the smallest single element of the array. Power-down
conditions would be maintained until the animal(s) is observed exiting
the exclusion zone or for 15 minutes beyond the last observation of the
animal, following which full-power operations may be resumed without
ramp-up. NMFS also provided an alternative proposal for consideration
by the public, in which no shutdown or power-down would be required
upon observation of the same species of dolphins. Following review of
public comments, NMFS removes the power-down measure for small
delphinids, in favor of the no-shutdown and no power-down alternative.
No shutdown or power-down is required for these species.
NMFS proposed a number of extended distance shutdown requirements
on the basis of detections of certain species deemed particularly
sensitive (e.g., beaked whales) or of particular circumstances deemed
to warrant the extended distance shutdown requirement (e.g., whales
with calves). These extended distance shutdowns were all conditioned
upon observation or detection of these species or circumstances ``at
any distance'' from the vessel. However, NMFS also included as an
alternative proposal for public consideration a distance limit of 1,000
m for these shutdown requirements. Following review of public comments,
NMFS determined that a distance limit on extended shutdown zones for
relevant species or circumstances was appropriate, but determined 1,500
m was the appropriate distance (rather than 1,000 m).
The proposed rule included an extended distance shutdown for sperm
whales that was applicable upon acoustic detection, but was not
applicable to visual detection. Following review of public comments,
the shutdown requirement has been expanded to include any detection of
sperm whales within the extended distance shutdown zone, including
visual detection.
For shallow penetration surveys, NMFS reduces the standard
exclusion zone from 200 m to 100 m, while including an extended
distance shutdown requirement mirroring the requirements for deep
penetration surveys, but within a distance of 500 m. NMFS eliminates
shutdown requirements for HRG surveys (defined here as surveys using
electromechanical sources such as multi-beam echosounders, side-scan
sonars, and chirp sub-bottom profilers). The proposed regulations
required shutdown for marine mammals within the proposed exclusion zone
for surveys operating in water depths greater than 200 m.
NMFS eliminates proposed requirements for visual observation during
nighttime ramp-up and pre-clearance, and for the use of third-party
PSOs aboard node retrieval vessels.
In the proposed rule, NMFS discussed the use of an extrapolation
method recommended by the Marine Mammal Commission for use in
estimating potential unobserved takes. NMFS agrees with public
commenters that the appropriateness of the method for application to
observations conducted from working source vessels (versus research
vessels) is unknown and, as suggested through public comment, NMFS will
not require use of this method but will continue to evaluate approaches
for assessment of effects to marine mammal stocks, including those
based on extrapolation of marine mammal detections, through the
adaptive management process and subsequently apply them through LOAs as
appropriate.
NMFS has revised requirements relating to reporting of injured or
dead marine mammals and has added newly crafted requirements relating
to actions that should be taken in response to notification of live
stranding events in certain circumstances, in order to reflect current
best practice.
The proposed rule indicated that LOA applications with take
estimates based on modeling other than that specifically included in
the modeling report used to support the EIS and the proposed rule (the
modeling report; Zeddies et al., 2015, 2017a) would necessarily be
published for public comment prior to the issuance of an LOA. Upon
consideration of public comment and related supplemental materials, the
final rule more flexibly allows that if applicants do not use the
modeling provided by the rule, NMFS will publish a notice in the
Federal Register soliciting public comment, when the model or inputs
differ substantively from those that have been reviewed by NMFS and the
public previously. Please see the Letters of Authorization section for
more detail.
[[Page 5332]]
Comments and Responses
NMFS published a notice of proposed rulemaking in the Federal
Register on June 22, 2018 (83 FR 29212), beginning a 60-day comment
period. In that notice, we requested public input on the proposed rule
and regulations, including the variations of the proposed rule, two
economic baselines, and other information provided in the Regulatory
Impact Analysis and associated appendices, and requested that
interested persons submit relevant information, suggestions, and
comments. In response to BOEM's change in scope and in consideration of
public comments, we modified our action, as discussed in the following
responses to comments. Please also see the Changes from the Proposed
Rule section, above. We note that one area of significant concern for
some members of the public was potential impacts to Bryde's whales and
related mitigation measures. The reduced geographic scope eliminates
the need to consider activity in the Bryde's whale ``core habitat
area'' and eliminates the majority of the incidental take of Bryde's
whale that was evaluated in the proposed rule.
During the 60-day comment period, we received 17 comment letters. A
letter was submitted jointly by the International Association of
Geophysical Contractors, the American Petroleum Institute, the National
Ocean Industries Association, and the Offshore Operators Committee
(hereafter, the ``Associations''). A separate letter was submitted
jointly by the Natural Resources Defense Council (NRDC), Center for
Biological Diversity, Earthjustice, Gulf Restoration Network, Humane
Society Legislative Fund, The Humane Society of the United States, and
Sierra Club (hereafter, ``NRDC''). Additional letters were submitted by
the following: BP Exploration & Production Inc. (BP), Consumer Energy
Alliance, CGG, Chevron USA Inc. (Chevron), the Center for Regulatory
Effectiveness (CRE), the Florida Department of Environmental
Protection, the Marine Mammal Commission (MMC), and eight private
citizens. NMFS has reviewed all public comments received on the
proposed rulemaking. All relevant comments and our responses are
described below, with comment responses outlined by major categories.
All comments received are available online at: www.regulations.gov. A
direct link to these comments is provided at: www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-gulf-mexico.
General Comments
As an initial matter, we note that under the MMPA, NMFS generally
does not have discretion regarding issuance of requested incidental
take authorizations for small numbers of marine mammals, provided that
(1) the total taking associated with a specified activity will have a
negligible impact on the affected species or stock(s); (2) the total
taking associated with a specified activity will not have an
unmitigable adverse impact on the availability of the species or
stock(s) for subsistence uses (not relevant here); and (3) mitigation,
monitoring, and reporting of such takings are set forth, including
mitigation measures sufficient to meet the standard of least
practicable adverse impact on the affected species or stocks and their
habitat.
In addition, NMFS' proposed action--the issuance of the ITR and any
subsequent LOAs authorizing incidental take of marine mammals--
addresses only marine mammals (and their habitat). As such, effects of
the surveys on other aspects of the marine environment are not relevant
to NMFS' analyses under the MMPA.
The MMPA does require that we evaluate potential effects to marine
mammal habitat, which includes prey species (e.g., zooplankton, fish,
squid). However, consideration of potential effects to taxa other than
marine mammals and their prey, or consideration of effects to potential
prey species in a context other than the import of such effects on
marine mammals, is not relevant to our action under the MMPA. We have
appropriately considered effects to marine mammal habitat. Separately,
BOEM evaluated effects to all relevant aspects of the human environment
(including marine mammals and other taxa) through the analysis
presented in BOEM's PEIS (available online at: www.boem.gov/Gulf-of-Mexico-Geological-and-Geophysical-Activities-Programmatic-EIS/), and
effects to all potentially affected species that are listed under the
Endangered Species Act (ESA) and any critical habitat designated for
those species were addressed through consultation between BOEM and NMFS
pursuant to section 7 of the ESA. That Biological Opinion, which
evaluated NMFS' proposed action (issuance of the ITR and any subsequent
LOAs) as well as all BOEM and Bureau of Safety and Environmental
Enforcement (BSEE) approvals of activities associated with the OCS oil
and gas program in the GOM, is available online at:
www.fisheries.noaa.gov/national/endangered-species-conservation/biological-opinions-issued-noaa-fisheries-office-protected. We do not
further address taxa other than marine mammals and marine mammal prey.
Comment: The Associations comment that the proposed ITR is a well-
structured and thorough document that appropriately concludes that
geophysical activities in the GOM would have no more than a negligible
impact on marine mammal populations, and that they appreciate NMFS'
effort in preparing the proposed ITR and consideration of some of the
Associations' previous comments.
Response: NMFS appreciates the comment.
Comment: The Associations comment that geophysical surveys play a
critical role in the safe and orderly development of the oil and gas
resources of the GOM.
Response: We acknowledge the background operational information
provided by the Associations.
Comment: BP comments that the ITR is a much-needed process to
govern the authorization of incidental takes of marine mammals
associated with geophysical survey activity in the GOM. Chevron also
indicates support for promulgation of the ITRs.
Response: NMFS appreciates the comments.
Comment: BP comments that projected survey efforts are
underestimated but did not provide specific justification or
recommendations.
R 
