Incidental Takes of Marine Mammals During Specified Activities; Marine Geophysical Survey in the Northeast Pacific Ocean, August - October 2009, 21631-21648 [E9-10821]
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[FR Doc. E9–10674 Filed 5–7–09; 8:45 am]
BILLING CODE 3510–22–S
DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric
Administration
RIN 0648–XI63
Incidental Takes of Marine Mammals
During Specified Activities; Marine
Geophysical Survey in the Northeast
Pacific Ocean, August – October 2009
AGENCY: National Marine Fisheries
Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA),
Commerce.
ACTION: Notice; proposed incidental
take authorization; request for
comments.
SUMMARY: NMFS has received an
application from the Lamont-Doherty
Earth Observatory (L-DEO), a part of
Columbia University, for an Incidental
Harassment Authorization (IHA) to take
small numbers of marine mammals, by
harassment, incidental to conducting a
seismic survey in the northeast Pacific
Ocean. Pursuant to the Marine Mammal
Protection Act (MMPA), NMFS requests
comments on its proposal to authorize
L-DEO to take, by Level B harassment
only, small numbers of marine
mammals incidental to conducting a
marine seismic survey during August
through October, 2009.
DATES: Comments and information must
be received no later than June 8, 2009.
ADDRESSES: Comments on the
application should be addressed to
Michael Payne, Chief, Permits,
Conservation and Education Division,
Office of Protected Resources, National
Marine Fisheries Service, 1315 EastWest Highway, Silver Spring, MD
20910–3225. The mailbox address for
providing email comments is PR1.0648–
XI63@noaa.gov. Comments sent via email, including all attachments, must
not exceed a 10–megabyte file size.
All comments received are a part of
the public record and will generally be
posted to https://www.nmfs.noaa.gov/pr/
permits/incidental.htm#applications
without change. All Personal Identifying
Information (for example, name,
address, etc.) voluntarily submitted by
the commenter may be publicly
accessible. Do not submit confidential
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21631
business information or otherwise
sensitive or protected information.
A copy of the application containing
a list of the references used in this
document may be obtained by writing to
the address specified above, telephoning
the contact listed below (see FOR
FURTHER INFORMATION CONTACT), or
visiting the internet at: https://
www.nmfs.noaa.gov/pr/permits/
incidental.htm#applications.
Documents cited in this notice may be
viewed, by appointment, during regular
business hours, at the aforementioned
address.
FOR FURTHER INFORMATION CONTACT:
Jeannine Cody or Howard Goldstein,
Office of Protected Resources, NMFS,
(301) 713–2289.
SUPPLEMENTARY INFORMATION:
Background
Sections 101(a)(5)(A) and (D) of the
MMPA (16 U.S.C. 1361 et seq.) direct
the Secretary of Commerce (Secretary)
to allow, upon request, the incidental,
but not intentional, taking of marine
mammals by United States citizens who
engage in a specified activity (other than
commercial fishing) within a specified
geographical region if certain findings
are made and either regulations are
issued or, if the taking is limited to
harassment, a notice of a proposed
authorization is provided to the public
for review.
Authorization for incidental taking
shall be granted if NMFS finds that the
taking will have a negligible impact on
the species or stock(s), will not have an
unmitigable adverse impact on the
availability of the species or stock(s) for
subsistence uses, 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.’’
Section 101(a)(5)(D) of the MMPA
established an expedited process by
which citizens of the United States can
apply for an authorization to
incidentally take small numbers of
marine mammals by harassment. 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
[ALevel A harassment@]; or (ii) has the
potential to disturb a marine mammal or
marine mammal stock in the wild by causing
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disruption of behavioral patterns, including,
but not limited to, migration, breathing,
nursing, breeding, feeding, or sheltering
[ALevel B harassment@].
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Section 101(a)(5)(D) establishes a 45–
day time limit for NMFS= review of an
application followed by a 30–day public
notice and comment period on any
proposed authorizations for the
incidental harassment of small numbers
of marine mammals. Not later than 45
days after the close of the public
comment period, if the Secretary makes
the findings set forth in Section
101(a)(5)(D)(i), the Secretary shall issue
or deny issuance of the authorization
with appropriate conditions to meet the
requirements of clause 101(a)(5)(D)(ii).
Summary of Request
On February 11, 2009, NMFS received
an application from L-DEO for the
taking by Level B harassment only, of
small numbers of 33 species of marine
mammals incidental to conducting a
marine seismic survey within the
Exclusive Economic Zone (EEZ) of
Canada in the northeast Pacific Ocean
during August through October 2009. LDEO, with research funding from the
NSF, is conducting the geophysical data
acquisition activities with onboard
assistance by Drs. Toomey and Hooft
from the University of Oregon, and Dr.
Wilcock from the University of
Washington.
This survey, also known as the
Endeavor Tomography (ETOMO) Study,
will take place approximately 250
kilometers (km) (155 miles (mi))
southwest of Vancouver Island, British
Columbia, within the Canadian
Endeavour Marine Protected Area
(MPA) along an 80–km- (50- mi-) long
section of the Endeavour segment of the
Juan de Fuca Ridge. The Endeavor MPA
is a unique ecosystem consisting of
hydrothermal vents and associated
fauna. Canada officially designated the
area as an MPA in March 2003.
However, scientific research for the
conservation, protection and
understanding of the area is permissible
under the Canadian Oceans Act of 1996.
Regulations regarding this MPA can be
found on the Department of Justice
Canada website at: https://
laws.justice.gc.ca/en/ShowFullDoc/cr/
SOR–2003–87///en.
The survey will obtain information on
the sub-seafloor structure of volcanic
and hydrothermal features that form as
a result of movements of the Earth’s
plates; will obtain information on the
three-dimensional (3–D) seismic
structure of the crust and top-most
mantle along an the Endeavour segment;
and will define the distribution of
magma beneath active volcanoes. Past
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studies using manned submersibles and
remotely piloted vehicles have mapped
the locations and characteristics of vent
fields along this ridge segment. The
ETOMO Study will extend that mapping
beneath the seafloor and allow
researchers to understand the dynamics
of these systems.
Description of the Specified Activity
The planned survey will involve one
source vessel, the R/V Marcus
G.Langseth (Langseth), a seismic
research vessel owned by the NSF and
operated by L-DEO. The proposed
project is scheduled to commence on
August 17, 2009, and scheduled to end
on October 13, 2009. The vessel will
depart Astoria, Oregon on August 17,
2009 for transit to the Endeavor MPA,
between 47–48° N. and 128–130° W.
To obtain high-resolution, 3–D
structures of the area’s magmatic
systems and thermal structures, the
Langseth will deploy a towed array of
36 airguns. The Langseth will also
deploy 64 Ocean Bottom Seismometers
(OBS). As the airgun array is towed
along the survey lines, the OBSs will
receive the returning acoustic signals
and record them internally for later
analysis. For the ETOMO study, the
Langseth will not use a hydrophone
streamer to receive geophysical data
from the airgun array.
The ETOMO study (e.g., equipment
testing, startup, line changes, repeat
coverage of any areas, and equipment
recovery) will take place in deep
(between 1200 and 3000 m, 3,280 feet
(ft) and 1.8 mi) water and will require
approximately 10 days to complete 12
transects of variable lengths totaling
1800 km of survey lines. Data
acquisition will include approximately
240 hours of airgun operation. Please
see L-DEO’s application for more
detailed information. The exact dates of
the activities will depend on logistics,
weather conditions, and the need to
repeat some lines if data quality is
substandard.
Vessel Specifications
The Langseth is a seismic research
vessel with a propulsion system
designed to be as quiet as possible to
avoid interference with the seismic
signals. The vessel, which has a length
of 71.5 m (235 feet (ft); a beam of 17.0
m (56 ft); a maximum draft of 5.9 m (19
ft); and a gross tonnage of 2925, can
accommodate up to 55 people. The ship
is powered by two Bergen BRG–6 diesel
engines, each producing 3550
horsepower (hp), which drive the two
propellers directly. Each propeller has
four blades, and the shaft typically
rotates at 750 revolutions per minute.
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The vessel also has an 800 hp
bowthruster, which is not used during
seismic acquisition. The operation
speed during seismic acquisition is
typically 7.4B9.3 km/hour (h) (4–5
knots). When not towing seismic survey
gear, the Langseth can cruise at 20B24
km/h (11–13 knots). The Langseth has a
range of 25,000 km (13,499 nautical
miles). The Langseth will also serve as
the platform from which vessel-based
marine mammal (and sea turtle)
observers will watch for animals before
and during airgun operations.
Acoustic Source Specifications
Seismic Airguns
The full airgun array for the survey
consists of 36 airguns (a mixture of Bolt
1500LL and Bolt 1900LLX airguns
ranging in size from 40 to 360 cubic
inches (in3)), with a total volume of
approximately 6,600 in3 and a firing
pressure of 1900 pounds per square inch
(psi). The dominant frequency
components range from two to 188
Hertz (Hz).
The array configuration consists of
four identical linear arrays or strings,
with 10 airguns on each string; the first
and last airguns will be spaced 16 m (52
ft) apart. For each operating string, nine
airguns will be fired simultaneously,
whereas the tenth is kept in reserve as
a spare, to be turned on in case of failure
of another airgun. The four airgun
strings will be distributed across an
approximate area of 24H16 m (79 x 52
ft) behind the Langseth and will be
towed approximately 50 to 100 m (164–
328 ft) behind the vessel at a tow-depth
of 15 m (49.2 ft). The airgun array will
fire every 250 m (105 seconds (s)) or 500
m (210 s) depending on which grid or
line the Langseth surveys. During firing,
a brief (approximately 0.1 s) pulse of
sound is emitted. The airguns will be
silent during the intervening periods.
Multibeam Echosounder
The Langseth will operate a Simrad
EM120 multibeam echosounder (MBES)
simultaneously during airgun
operations to map characteristics of the
ocean floor. The hull-mounted MBES
emits brief pulses of mid- or highfrequency (11.25–12.6 kHz) sound in a
fanshaped beam that extends downward
and to the sides of the ship. The
beamwidth is 1 degree (°) fore-aft and
150° athwartship. The maximum source
level is 242 dB re 1 μPa• m (root mean
square (rms)). For deep-water operation,
each Aping@ consists of nine successive
fan-shaped transmissions, each 15
millisecond (ms) in duration and each
ensonifying a sector that extends 1°
foreBaft. The nine successive
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transmissions span an overall crosstrack angular extent of about 150°, with
16 ms gaps between the pulses for
successive sectors. A receiver in the
overlap area between two sectors would
receive two 15–ms pulses separated by
a 16–ms gap. In shallower water, the
pulse duration is reduced to 5 or 2 ms,
and the number of transmit beams is
also reduced. The ping interval varies
with water depth, from approximately 5
s at 1000 m (3,281 ft) to 20 s at 4000 m
(13,124 ft).
Sub-bottom Profiler
The Langseth will operate a subbottom profiler (SBP) continuously
throughout the cruise with the MBES.
An SBP operates at mid- to high
frequencies and is generally used
simultaneously with an MBES to
provide information about the
sedimentary features and bottom
topography. SBP pulses are directed
downward at typical frequencies of
approximately 3 18 kHz. However, the
dominant frequency component of the
SBP is 3.5 kHz which is directed
downward in a narrow beam by a hullmounted transducer on the vessel. The
SBP output varies with water depth
from 50 watts in shallow water to 800
watts in deep water and has a normal
source output (downward) of 200 dB re
1 μPa m and a maximum source level
output (downward) of 204 dB re 1 μPa
m.
The SBP used aboard the Langseth
uses seven beams simultaneously, with
a beam spacing of up to 15° and a fan
width up to 30°. Pulse duration is 0.4
100 ms at intervals of 1 s; a common
mode of operation is to broadcast five
pulses at 1–s intervals followed by a 5–
s pause.
Characteristics of Airgun Pulses
Discussion of the characteristics of
airgun pulses has been provided in
Appendix B of L-DEO=s application and
in previous Federal Register notices
(see 69 FR 31792, June 7, 2004; 71 FR
58790, October 5, 2006; 72 FR 71625,
December 18, 2007; 73 FR 52950,
September 12, 2008, or 73 FR 71606,
November 25, 2008). Reviewers are
referred to those documents for
additional information.
Safety Radii
Safety zones are areas defined by the
radius of received sound levels believed
to have the potential for at least
temporary hearing impairment (HESS,
1999). The distance from the sound
source at which an animal would be
exposed to these different received
sound levels may be estimated and is
typically referred to as safety radii.
These safety radii are specifically used
to help NMFS estimate the number of
marine mammals likely to be harassed
by the proposed activity and in deciding
how close a marine mammal may
approach an operating sound source
before the applicant will be required to
power-down or shut down the sound
source.
During this study, all survey efforts
will take place in deep (greater than
1000 m, 3820 ft) water. L-DEO has
summarized the modeled safety radii for
the planned airgun configuration in
Table 1 which shows the predicted
distances at which sound levels (190
decibels (dB), 180 dB, and 160 dB) are
expected to be received from the 36–
airgun array and a single airgun
operating in water greater than 1000 m
(3,820 ft) in depth.
TABLE 1. PREDICTED DISTANCES TO WHICH SOUND LEVELS ≥190, 180, AND 160 DB RE 1 μPA MIGHT BE RECEIVED IN
DEEP (>1000 M; 3280 FT) WATER FROM THE 36–AIRGUN ARRAY DURING THE SEISMIC SURVEY, AUGUST SEPTEMBER,
2009 (BASED ON L-DEO MODELING).
Predicted RMS Distances (m)
Source and Volume
Tow Depth (m)
190 dB
Single Bolt airgun 40 in3
4 strings 36 airguns 6600 in3
160 dB
12
220
300
340
380
6–15*
6
9
12
15
180 dB
40
710
950
1120
1220
385
4670
6000
6850
7690
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*The tow depth has minimal effect on the maximum near-field output and the shape of the frequency spectrum for the single 40 in3 airgun;
thus the predicted safety radii are essentially the same at each tow depth.
The L-DEO model applied to airgun
configuration does not allow for bottom
interactions, and thus is most directly
applicable to deep water and to
relatively short ranges. The calculated
distances are expected to overestimate
the actual distances to the
corresponding Sound Pressure Levels
(SPL), given the deep-water results of
Tolstoy et al. (2004a,b). Additional
information regarding how the safety
radii were calculated and how the
empirical measurements were used to
correct the modeled numbers may be
found in Appendix A of L-DEO=s
Environmental Assessment (EA). The
conclusion that the model predictions
in Table 1 are precautionary, relative to
actual 180- and 190–dB (rms) radii, is
based on empirical data from the
acoustic calibration of different airgun
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configurations used by the R/V Maurice
Ewing (Ewing) in the northern Gulf of
Mexico. (Tolstoy et al., 2004a,b).
L-DEO conducted a more extensive
acoustic calibration study of the
Langseth=s 36–airgun array in late
2007/early 2008 in the northern Gulf of
Mexico (LGL Ltd., 2006; Holst and
Beland, 2008). L-DEO is currently
modeling the distances to the
corresponding Sound Pressure Levels
(SPL) (e.g., 190, 180, and 160 dB re 1
μPa (rms)) for various airgun
configurations and water depths. Those
results are not yet available. However,
the empirical data from the 2007/2008
calibration study will be used to refine
the exclusion zones proposed above for
use during survey, if the data are
appropriate and available at the time of
the survey.
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Description of Marine Mammals in the
Activity Area
Thirty-three marine mammal species
may occur off the coast of British
Columbia, Canada, including 20
odontocetes (toothed cetaceans), 7
mysticetes (baleen whales), 5 pinnipeds,
and the sea otter (Enhydra sp.). In the
United States, sea otters are managed by
the U.S. Fish and Wildlife Service
(USFWS) and are unlikely to be
encountered in or near the Endeavor
Marine Protected Area where seismic
operations will occur, and are, therefore,
not addressed further in this document.
Eight of these species are listed as
endangered under the U.S. Endangered
Species Act of 1973 (ESA), including
the Steller sea lion (Eumetopias
jubatus), the humpback (Megaptera
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novaeanliae), sei (Balaenoptera
borealis), fin (Balenoptera physalus),
blue (Balenoptera musculus), North
Pacific right (Eubalena japonica), sperm
(Physeter macrocephalus), and Southern
Resident killer (Orcinus orca) whales.
This proposed IHA will only address
requested take authorizations for
cetaceans and pinnipeds. Table 2 below
outlines the species, their habitat and
abundance in the proposed survey area,
the estimated number of exposures
(based on average density) to sound
levels greater than or equal to 160 dB
during the seismic survey if no animals
moved away from the survey vessel.
Estimated
Number of Individuals Exposed to
Sound Levels
≥160 dB
Approx. Percent of Regional Population
Habitat
Abundance in the
NE Pacific
Occurrence in the
Survey Area
Estimated
Number of Exposures to
Sound Levels ≥
160 dB
North Pacific right
whale*
Coastal and shelf waters
100–200
Rare and unlikely
0
0
0
Humpback whale*
Coastal waters
>6000
Uncommon
29
6
0.10
Coastal and shelf waters
9000
Uncommon
26
26
0.06
Sei whale
Pelagic
7260 - 12,620
Uncommon
5
1
0.01
Fin whale*
Pelagic, shelf and
coastal waters
13,620–18,680
Uncommon
39
8
0.05
Blue whale*
Pelagic, shelf and
inshore waters
1186
Uncommon
8
2
0.14
Pelagic
24,000
Uncommon
52
10
0.04
Pygmy sperm whale
Deep waters off the
shelf
Not available
Common
47
9
Not available
Dwarf Sperm whale
Deep waters off the
shelf
Not available
Uncommon
0
0
0.0
Baird’s beaked
whale
Deep waters and
cont. slopes
6000
Common
62
13
0.21
Blainville’s beaked
whale
Deep waters and
cont. slopes
603
Uncommon
8
2
0.28
Cuvier’s beaked
whale
Pelagic
20,000
Uncommon
0
0
0.0
Hubb’s beaked
whale
Deep waters and
cont. slopes
421
Uncommon
8
2
0.40
Stejneger’s beaked
whale
Deep waters
421
Uncommon
8
2
0.40
Bottlenose dolphin
Coastal and offshore
waters
3257
Rare
0
0
0.0
Pelagic
23,883
rare
2
0
0.0
Short-beaked common dolphin
Coastal and offshore
waters
487,622
Common
511
104
0.02
Pacific white-sided
dolphin
Pelagic, shelf and
slope waters
931,000
Common
895
181
0.02
Northern right-whale
dolphin
Pelagic, shelf and
slope waters
15,305
Common
699
142
0.93
Risso’s dolphin
Pelagic
12,093
Common
467
95
0.78
False killer whale
Pelagic
Not available
Rare
0
0
0.0
Widely distributed
8500
Uncommon
61
12
0.15
Pelagic
160,200
Uncommon
0
0
00.0
Species
Minke whale
Sperm whale*
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Striped dolphin
Killer whale
Short-finned pilot
whale
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Estimated
Number of Individuals Exposed to
Sound Levels
≥160 dB
Approx. Percent of Regional Population
Habitat
Abundance in the
NE Pacific
Occurrence in the
Survey Area
Estimated
Number of Exposures to
Sound Levels ≥
160 dB
Offshore and nearshore waters
57,549
Common
5337
1081
1.88
Coastal
721,935
Common
360
73
0.01
8,624
1,748
Species
Dall’s porpoise
Northern fur seal
Total
Table 2. Abundance, preferred habitat, and commonness of the marine mammal species that may be encountered during the proposed survey
within the ETOMO survey area. The far right columns indicate the estimated number of each species that will be exposed to ≥160 dB based on
average density estimates. NMFS believes that, when mitigation measures are taken into consideration, the activity is likely to result in take of
numbers of animals less than those indicated by the column titled NUmber of Individuals Exposed ≥160 dB.
* Federally listed endangered species.
Detailed information regarding the
status and distribution of these marine
mammals may be found in sections III
and IV of L-DEO’s application.
Potential Effects of the Proposed
Activity on Marine Mammals
Summary of Potential Effects of Airgun
Sounds on Marine Mammals
The effects of sounds from airguns
might include one or more of the
following: tolerance, masking of natural
sounds, behavioral disturbance,
temporary or permanent hearing
impairment, or non-auditory physical or
physiological effects (Richardson et al.,
1995; Gordon et al., 2004; Nowacek et
al., 2007; Southall et al., 2007).
Permanent hearing impairment, in the
unlikely event that it occurred, would
constitute injury, but temporary
threshold shift (TTS) is not an injury
(Southall et al., 2007). Although the
possibility cannot be entirely excluded,
it is unlikely that the project would
result in any cases of temporary or
permanent hearing impairment, or any
significant non-auditory physical or
physiological effects. Some behavioral
disturbance is expected, but is expected
to be localized and short-term.
hsrobinson on PROD1PC76 with NOTICES
Tolerance
Numerous studies have shown that
pulsed sounds from airguns are often
readily detectable in the water at
distances of many kilometers. For a brief
summary of the characteristics of airgun
pulses, see Appendix B of L-DEO’s
application. Several studies have also
shown that marine mammals at
distances more than a few kilometers
from operating seismic vessels often
show no apparent response (tolerance)
(see Appendix B (5) of L-DEO’s EA).
That is often true even in cases when
the pulsed sounds must be readily
audible to the animals based on
measured received levels and the
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hearing sensitivity of that mammal
group. Although various baleen whales,
toothed whales, and (less frequently)
pinnipeds have been shown to react
behaviorally to airgun pulses under
some conditions, at other times
mammals of all three types have shown
no overt reactions. In general, pinnipeds
usually seem to be more tolerant of
exposure to airgun pulses than
cetaceans, with the relative
responsiveness of baleen and toothed
whales being variable.
Masking
Introduced underwater sound may,
through masking, reduce the effective
communication distance of a marine
mammal species if the frequency of the
source is close to that used as a signal
by the marine mammal, and if the
anthropogenic sound is present for a
significant fraction of the time
(Richardson et al., 1995).
Masking effects of pulsed sounds
(even from large arrays of airguns) on
marine mammal calls and other natural
sounds are expected to be limited,
although there are very few specific data
on this. Because of the intermittent
nature and low duty cycle of seismic
pulses, animals can emit and receive
sounds in the relatively quiet intervals
between pulses. However, in some
situations, multi-path arrivals and
reverberation cause airgun sound to
arrive for much or all of the interval
between pulses (e.g., Simard et al.,
2005; Clark and Gagnon, 2006) which
could mask calls. Some baleen and
toothed whales are known to continue
calling in the presence of seismic
pulses, and their calls can usually be
heard between the seismic pulses (e.g.,
Richardson et al., 1986; McDonald et al.,
1995; Greene et al., 1999; Nieukirk et
al., 2004; Smultea et al., 2004; Holst et
al., 2005a,b, 2006). In the northeast
Pacific Ocean, blue whale calls have
been recorded during a seismic survey
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off Oregon (McDonald et al., 1995).
Among odontocetes, there has been one
report that sperm whales ceased calling
when exposed to pulses from a very
distant seismic ship (Bowles et al.,
1994). However, more recent studies
found that this species continued
calling in the presence of seismic pulses
(Madsen et al., 2002; Tyack et al., 2003;
Smultea et al., 2004; Holst et al., 2006;
Jochens et al., 2006, 2008). Dolphins
and porpoises commonly are heard
calling while airguns are operating (e.g.,
Gordon et al., 2004; Smultea et al., 2004;
Holst et al., 2005a,b; Potter et al., 2007).
The sounds important to small
odontocetes are predominantly at much
higher frequencies than are the
dominant components of airgun sounds,
thus limiting the potential for masking.
In general, masking effects of seismic
pulses are expected to be negligible,
given the normally intermittent nature
of seismic pulses. Masking effects on
marine mammals are discussed further
in Appendix B (4) of L-DEO’s EA.
Disturbance Reactions
Disturbance includes a variety of
effects, including subtle to conspicuous
changes in behavior, movement, and
displacement. Based on NMFS (2001, p.
9293), NRC (2005), and Southall et al.
(2007), L-DEO assumes that simple
exposure to sound, or brief reactions
that do not disrupt behavioral patterns
in a potentially significant manner, do
not constitute harassment or ‘‘taking’’.
By potentially significant, L-DEO means
‘‘in a manner that might have
deleterious effects to the well-being of
individual marine mammals or their
populations’’.
Reactions to sound, if any, depend on
species, state of maturity, experience,
current activity, reproductive state, time
of day, and many other factors
(Richardson et al., 1995; Wartzok et al.,
2004; Southall et al., 2007). If a marine
mammal does react briefly to an
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underwater sound by changing its
behavior or moving a small distance, the
impacts of the change are unlikely to be
significant to the individual, let alone
the stock or population. However, if a
sound source displaces marine
mammals from an important feeding or
breeding area for a prolonged period,
impacts on individuals and populations
could be significant (e.g., Lusseau and
Bejder, 2007; Weilgart, 2007). Given the
many uncertainties in predicting the
quantity and types of impacts of noise
on marine mammals, it is common
practice to estimate how many
mammals would be present within a
particular distance of industrial
activities and exposed to a particular
level of industrial sound. In most cases,
this approach likely overestimates the
numbers of marine mammals that would
be affected in some biologicallyimportant manner.
The sound criteria used to estimate
how many marine mammals might be
disturbed to some biologicallyimportant degree by a seismic program
are based primarily on behavioral
observations of a few species. Detailed
studies have been done on humpback,
gray (Eshrichtius robustus), bowhead
(Balena mysticetes), and sperm whales,
and on ringed seals (Pusa hispida). Less
detailed data are available for some
other species of baleen whales, and
small toothed whales, but for many
species there are no data on responses
to marine seismic surveys.
Baleen Whales
Baleen whales generally tend to avoid
operating airguns, but avoidance radii
are quite variable. Whales are often
reported to show no overt reactions to
pulses from large arrays of airguns at
distances beyond a few kilometers, even
though the airgun pulses remain well
above ambient noise levels out to much
longer distances. However, as reviewed
in Appendix B (5) of L-DEO’s EA,
baleen whales exposed to strong noise
pulses from airguns often react by
deviating from their normal migration
route and/or interrupting their feeding
and moving away. In the cases of
migrating gray and bowhead whales, the
observed changes in behavior appeared
to be of little or no biological
consequence to the animals. They
simply avoided the sound source by
displacing their migration route to
varying degrees, but within the natural
boundaries of the migration corridors.
Studies of gray, bowhead, and
humpback whales have shown that
seismic pulses with received levels of
160 170 dB re 1 μPa (rms) seem to cause
obvious avoidance behavior in a
substantial fraction of the animals
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exposed (Richardson et al., 1995). In
many areas, seismic pulses from large
arrays of airguns diminish to those
levels at distances ranging from 4–15
km (2.5–9.3 mi) from the source. A
substantial proportion of the baleen
whales within those distances may
show avoidance or other strong
behavioral reactions to the airgun array.
Subtle behavioral changes sometimes
become evident at somewhat lower
received levels, and studies summarized
in Appendix B of L-DEO’s EA have
shown that some species of baleen
whales, notably bowhead and
humpback whales, at times show strong
avoidance at received levels lower than
160 170 dB re 1 μPa (rms).
Responses of humpback whales to
seismic surveys have been studied
during migration, on summer feeding
grounds, and on Angolan winter
breeding grounds; there has also been
discussion of effects on the Brazilian
wintering grounds. McCauley et al.
(1998, 2000a) studied the responses of
humpback whales off Western Australia
to a full-scale seismic survey with a 16–
airgun, 2678–in3 array, and to a single
20–in3 airgun with source level of 227
dB re 1 μPa m (peak to peak). McCauley
et al. (1998) documented that avoidance
reactions began at 5–8 km (3–5 mi) from
the array, and that those reactions kept
most pods approximately 3–4 km (1.8–
2.5 mi) from the operating seismic boat.
McCauley et al. (2000a) noted localized
displacement during migration of 4–5
km (2.5–3.1 mi) by traveling pods and
7–12 km (4.3–7.5 mi) by more sensitive
resting pods of cow-calf pairs.
Avoidance distances with respect to the
single airgun were smaller but
consistent with the results from the full
array in terms of the received sound
levels. The mean received level for
initial avoidance of an approaching
airgun was 140 dB re 1 μPa (rms) for
humpback pods containing females, and
at the mean closest point of approach
distance the received level was 143 dB
re 1 μPa (rms). The initial avoidance
response generally occurred at distances
of 5–8 km (3.1–4.9 mi) from the airgun
array and 2 km (1.2 mi) from the single
airgun. However, some individual
humpback whales, especially males,
approached within distances of 100–400
m (328–1312 ft), where the maximum
received level was 179 dB re 1 μPa
(rms).
Humpback whales on their summer
feeding grounds in southeast Alaska did
not exhibit persistent avoidance when
exposed to seismic pulses from a 1.64–
L (100–in3) airgun (Malme et al., 1985).
Malme et al. reported that some of the
humpbacks seemed startled at received
levels of 150 169 dB re 1 μPa and
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concluded that there was no clear
evidence of avoidance, despite the
possibility of subtle effects, at received
levels up to 172 re 1 FPa on an
approximate rms basis.
It has been suggested that South
Atlantic humpback whales wintering off
Brazil may be displaced or even strand
upon exposure to seismic surveys (Engel
et al., 2004). The evidence for this was
circumstantial and subject to alternative
explanations (IAGC, 2004). Also, the
evidence was not consistent with
subsequent results from the same area of
Brazil (Parente et al., 2006), or with
direct studies of humpbacks exposed to
seismic surveys in other areas and
seasons. After allowance for data from
subsequent years, there was ‘‘no
observable direct correlation’’ between
strandings and seismic surveys (IWC,
2007:236).
There are no data on reactions of right
whales to seismic surveys, but results
from the closely-related bowhead whale
show that their responsiveness can be
quite variable depending on their
activity (migrating vs. feeding).
Bowhead whales migrating west across
the Alaskan Beaufort Sea in autumn, in
particular, are unusually responsive,
with substantial avoidance occurring
out to distances of 20 - 30 km (12.4 18.6 mi) from a medium-sized airgun
source at received sound levels of
around 120 130 dB re 1 μPa (rms)
(Miller et al., 1999; Richardson et al.,
1999; see Appendix B (5) of the EA.
However, more recent research on
bowhead whales (Miller et al., 2005;
Harris et al., 2007) corroborates earlier
evidence that, during the summer
feeding season, bowheads are not as
sensitive to seismic sources.
Nonetheless, subtle but statistically
significant changes in surfacing
respiration dive cycles were evident
upon statistical analysis (Richardson et
al., 1986). In summer, bowheads
typically begin to show avoidance
reactions at received levels of about 152
178 dB re 1 μPa (rms) (Richardson et al.,
1986, 1995; Ljungblad et al., 1988;
Miller et al., 2005).
Reactions of migrating and feeding
(but not wintering) gray whales to
seismic surveys have been studied.
Malme et al. (1986, 1988) studied the
responses of feeding eastern Pacific gray
whales to pulses from a single 100–in3
airgun off St. Lawrence Island in the
northern Bering Sea. They estimated,
based on small sample sizes, that 50
percent of feeding gray whales stopped
feeding at an average received pressure
level of 173 dB re 1 μPa on an
(approximate) rms basis, and that 10
percent of feeding whales interrupted
feeding at received levels of 163 dB re
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1 μPa (rms). Those findings were
generally consistent with the results of
experiments conducted on larger
numbers of gray whales that were
migrating along the California coast
(Malme et al., 1984; Malme and Miles,
1985), and western Pacific gray whales
feeding off Sakhalin Island, Russia
(Wursig et al., 1999; Gailey et al., 2007;
Johnson et al., 2007; Yazvenko et al.,
2007a,b), along with data on gray
whales off British Columbia (Bain and
Williams, 2006).
Various species of Balaenoptera (blue,
sei, fin, and minke whales) have
occasionally been reported in areas
ensonified by airgun pulses (Stone,
2003; MacLean and Haley, 2004; Stone
and Tasker, 2006). Sightings by
observers on seismic vessels off the
United Kingdom from 1997 to 2000
suggest that, during times of good
sightability, sighting rates for mysticetes
(mainly fin and sei whales) were similar
when large arrays of airguns were
shooting vs. silent (Stone, 2003; Stone
and Tasker, 2006). However, these
whales tended to exhibit localized
avoidance, remaining significantly
further (on average) from the airgun
array during seismic operations
compared with non-seismic periods
(Stone and Tasker, 2006). In a study off
Nova Scotia, Moulton and Miller (2005)
found little difference in sighting rates
(after accounting for water depth) and
initial sighting distances of
balaenopterid whales when airguns
were operating versus silent. However,
there were indications that these whales
were more likely to be moving away
when seen during airgun operations.
Similarly, ship-based monitoring
studies of blue, fin, sei and minke
whales offshore of Newfoundland
(Orphan Basin and Laurentian Subbasin) found no more than small
differences in sighting rates and swim
directions during seismic vs. nonseismic periods Moulton et al., 2005,
2006a,b).
Data on short-term reactions by
cetaceans to impulsive noises are not
necessarily indicative of long-term or
biologically significant effects. It is not
known whether impulsive sounds affect
reproductive rate or distribution and
habitat use in subsequent days or years.
However, gray whales have continued to
migrate annually along the west coast of
North America with substantial
increases in the population over recent
years, despite intermittent seismic
exploration (and much ship traffic) in
that area for decades (Appendix A in
Malme et al., 1984; Richardson et al.,
1995; Angliss and Outlaw, 2008). The
western Pacific gray whale population
did not seem affected by a seismic
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17:51 May 07, 2009
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survey in its feeding ground during a
previous year (Johnson et al., 2007).
Similarly, bowhead whales have
continued to travel to the eastern
Beaufort Sea each summer, and their
numbers have increased notably,
despite seismic exploration in their
summer and autumn range for many
years (Richardson et al., 1987; Angliss
and Outlaw, 2008).
Toothed Whales
Little systematic information is
available about reactions of toothed
whales to noise pulses. Few studies
similar to the more extensive baleen
whale/seismic pulse work summarized
above and (in more detail) in Appendix
B of L-DEO’s EA have been reported for
toothed whales. However, there are
recent systematic studies on sperm
whales (Jochens et al., 2006; Miller et
al., 2006), and there is an increasing
amount of information about responses
of various odontocetes to seismic
surveys based on monitoring studies
(e.g., Stone, 2003; Smultea et al., 2004;
Moulton and Miller, 2005; Bain and
Williams, 2006; Holst et al., 2006; Stone
and Tasker, 2006; Potter et al., 2007;
Weir, 2008).
Seismic operators and marine
mammal observers on seismic vessels
regularly see dolphins and other small
toothed whales near operating airgun
arrays, but in general there is a tendency
for most delphinids to show some
avoidance of operating seismic vessels
(e.g., Goold, 1996a,b,c; Calambokidis
and Osmek, 1998; Stone, 2003; Moulton
and Miller, 2005; Holst et al., 2006;
Stone and Tasker, 2006; Weir, 2008).
Some dolphins seem to be attracted to
the seismic vessel and floats, and some
ride the bow wave of the seismic vessel
even when large arrays of airguns are
firing (e.g., Moulton and Miller, 2005).
Nonetheless, small toothed whales more
often tend to head away, or to maintain
a somewhat greater distance from the
vessel, when a large array of airguns is
operating than when it is silent (e.g.,
Stone and Tasker, 2006; Weir, 2008). In
most cases the avoidance radii for
delphinids appear to be small, on the
order of 1 km less, and some individuals
show no apparent avoidance. The
beluga (Delphinapterus leucas) is a
species that (at times) shows longdistance avoidance of seismic vessels.
Aerial surveys conducted in the
southeastern Beaufort Sea during
summer found that sighting rates of
beluga whales were significantly lower
at distances 10–20 km (6.2–12.4 mi)
compared with 20–30 km (12.4–18.6 mi)
from an operating airgun array, and
observers on seismic boats in that area
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21637
rarely see belugas (Miller et al., 2005;
Harris et al., 2007).
Captive bottlenose dolphins (Tursiops
truncates) and beluga whales exhibited
changes in behavior when exposed to
strong pulsed sounds similar in
duration to those typically used in
seismic surveys (Finneran et al., 2000,
2002, 2005). However, the animals
tolerated high received levels of sound
before exhibiting aversive behaviors.
Results for porpoises depend on
species. The limited available data
suggest that harbor porpoises (Phocoena
phocoena) show stronger avoidance of
seismic operations than do Dall’s
porpoises (Phocoenoides dalli) (Stone,
2003; MacLean and Koski, 2005; Bain
and Williams, 2006; Stone and Tasker,
2006). Dall’s porpoises seem relatively
tolerant of airgun operations (MacLean
and Koski, 2005; Bain and Williams,
2006), although they too have been
observed to avoid large arrays of
operating airguns (Calambokidis and
Osmek, 1998; Bain and Williams, 2006).
This apparent difference in
responsiveness of these two porpoise
species is consistent with their relative
responsiveness to boat traffic and some
other acoustic sources (Richardson et
al., 1995; Southall et al., 2007).
Most studies of sperm whales exposed
to airgun sounds indicate that the sperm
whale shows considerable tolerance of
airgun pulses (e.g., Stone, 2003;
Moulton et al., 2005, 2006a; Stone and
Tasker, 2006; Weir, 2008). In most cases
the whales do not show strong
avoidance, and they continue to call
(see Appendix B of L-DEO’s EA for
review). However, controlled exposure
experiments in the Gulf of Mexico
indicate that foraging behavior was
altered upon exposure to airgun sound
(Jochens et al., 2006). In the Sperm
Whale Seismic Study (SWSS), D-tags
(Johnson and Tyack, 2003) were used to
record the movement and acoustic
exposure of eight foraging sperm whales
before, during, and after controlled
sound exposures of airgun arrays in the
Gulf of Mexico (Jochens et al., 2008).
Whales were exposed to maximum
received sound levels between 111 and
147 dB re 1 μPa rms (131 – 164 dB re
1 μPa pk-pk) at ranges of approximately
1.4 - 12.6 km (0.8 – 7.8 mi) from the
sound source. Although the tagged
whales showed no horizontal
avoidance, some whales changed
foraging behavior during full-array
exposure (Jochens et al., 2008).
There are almost no specific data on
the behavioral reactions of beaked
whales to seismic surveys. However,
northern bottlenose whales continued to
produce high-frequency clicks when
exposed to sound pulses from distant
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seismic surveys (Laurinolli and
Cochrane, 2005; Simard et al., 2005).
Most beaked whales tend to avoid
approaching vessels of other types (e.g.,
Wursig et al., 1998). They may also dive
for an extended period when
approached by a vessel (e.g., Kasuya,
1986), although it is uncertain how
much longer such dives may be as
compared to dives by undisturbed
beaked whales, which also are often
quite long (Baird et al., 2006; Tyack et
al., 2006). In any event, it is likely that
most beaked whales would also show
strong avoidance of an approaching
seismic vessel, although this has not
been documented explicitly.
There are increasing indications that
some beaked whales tend to strand
when naval exercises involving midfrequency sonar operation are ongoing
nearby (e.g., Simmonds and LopezJurado, 1991; Frantzis, 1998; NOAA and
USN, 2001; Jepson et al., 2003;
Hildebrand, 2005; Barlow and Gisiner,
2006; see also the ‘‘Strandings and
Mortality’’ subsection, later). These
strandings are apparently at least in part
a disturbance response, although
auditory or other injuries or other
physiological effects may also be
involved. Whether beaked whales
would ever react similarly to seismic
surveys is unknown (see ‘‘Strandings
and Mortality’’, below). Seismic survey
sounds are quite different from those of
the sonars in operation during the
above-cited incidents, and in particular,
the dominant frequencies in airgun
pulses are at lower frequencies than
used by mid-frequency naval sonars.
Odontocete reactions to large arrays of
airguns are variable and, at least for
delphinids and some porpoises (e.g.,
Dall’s, Phocoenoides dalli), seem to be
confined to a smaller radius than has
been observed for the more responsive
of the mysticetes, belugas, and harbor
porpoises (refer to Appendix B in LDEO’s EA).
Pinnipeds
Pinnipeds are not likely to show a
strong avoidance reaction to the airgun
array. Visual monitoring from seismic
vessels has shown only slight (if any)
avoidance of airguns by pinnipeds, and
only slight (if any) changes in behavior
see Appendix B (5) of the EA. In the
Beaufort Sea, some ringed seals avoided
an area of 100 m (328 ft) to (at most) a
few hundred meters around seismic
vessels, but many seals remained within
100 - 200 m (328 656 ft) of the trackline
as the operating airgun array passed by
(e.g., Harris et al., 2001; Moulton and
Lawson 2002; Miller et al., 2005).
Ringed seal sightings averaged
somewhat farther away from the seismic
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vessel when the airguns were operating
than when they were not, but the
difference was small (Moulton and
Lawson, 2002). Similarly, in Puget
Sound, sighting distances for harbor
seals (Phoca vitulina) and California sea
lions (Zalophus californianus) tended to
be larger when airguns were operating
(Calambokidis and Osmek, 1998).
Previous telemetry work suggests that
avoidance and other behavioral
reactions may be stronger than evident
to date from visual studies (Thompson
et al., 1998). Even if reactions of any
pinnipeds that might be encountered in
the present study area are as strong as
those evident in the telemetry study,
reactions are expected to be confined to
relatively small distances and durations,
with no long-term effects on pinniped
individuals or populations.
Hearing Impairment and Other Physical
Effects
Temporary or permanent hearing
impairment is a possibility when marine
mammals are exposed to very strong
sounds, and temporary threshold shift
(TTS) has been demonstrated and
studied in certain captive odontocetes
and pinnipeds exposed to strong sounds
(reviewed in Southall et al., 2007).
Current NMFS policy regarding
exposure of marine mammals to highlevel sounds is that cetaceans and
pinnipeds should not be exposed to
impulsive sounds with received levels
greater than or equal to 180 and 190 dB
re 1 μPa rms, respectively (NMFS 2000).
L-DEO has used those criteria to
establish the exclusion (i.e., shut-down)
zones planned for the proposed seismic
survey. However, those criteria were
established before there was any
information about minimum received
levels of sounds necessary to cause
auditory impairment in marine
mammals. As discussed in Appendix B
of the EA: (1) the 180–dB criterion for
cetaceans is probably quite
precautionary, i.e., lower than necessary
to avoid temporary auditory impairment
let alone permanent auditory injury; (2)
NMFS treats TTS as the upper bound of
Level B Harassment. Tissues are not
irreparably damaged with the onset of
TTS, the effects are temporary
(particularly for onset-TTS), and NMFS
does not believe that this effect qualifies
as an injury; (3) the minimum sound
level necessary to cause permanent
hearing impairment (‘‘Level A
harassment’’) is higher, by a variable
and generally unknown amount, than
the level that induces barely detectable
TTS; and (4) the level associated with
the onset of TTS is often considered to
be a level below which there is no
danger of permanent damage. The actual
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PTS threshold is likely to be well above
the level causing onset of TTS (Southall
et al., 2007).
Recommendations for new sciencebased noise exposure criteria for marine
mammals, frequency-weighting
procedures, and related matters were
published recently (Southall et al.,
2007). Those recommendations have
not, as of early 2009, been formally
adopted by NMFS for use in regulatory
processes and during mitigation
programs associated with seismic
surveys. However, some aspects of the
recommendations have been taken into
account in certain Environmental
Impact Statements and small-take
authorizations. NMFS has indicated that
it may issue new noise exposure criteria
for marine mammals that account for
the now available scientific data on
TTS, the expected offset between the
TTS and PTS thresholds, differences in
the acoustic frequencies to which
different marine mammal groups are
sensitive, and other relevant factors.
Preliminary information about possible
changes in the regulatory and mitigation
requirements, and about the possible
structure of new criteria, was given by
Wieting (2004) and NMFS (2005).
Several aspects of the planned
monitoring and mitigation measures for
this project are designed to detect
marine mammals occurring near the
airgun array, and to avoid exposing
them to sound pulses that might, at least
in theory, cause hearing impairment
(see section XI of L-DEO’s application).
In addition, many cetaceans and (to a
limited degree) pinnipeds and sea
turtles show some avoidance of the area
where received levels of airgun sound
are high enough such that hearing
impairment could potentially occur. In
those cases, the avoidance responses of
the animals themselves will reduce or
(most likely) avoid any possibility of
hearing impairment.
Non-auditory physical effects might
also occur in marine mammals exposed
to strong underwater pulsed sound.
Possible types of non-auditory
physiological effects or injuries that
might (in theory) occur in mammals
close to a strong sound source include
stress, neurological effects, bubble
formation, and other types of organ or
tissue damage. It is possible that some
marine mammal species (i.e., beaked
whales) may be especially susceptible to
injury and/or stranding when exposed
to strong pulsed sounds. However, as
discussed below, there is no definitive
evidence that any of these effects occur
even for marine mammals in close
proximity to large arrays of airguns. It is
unlikely that any effects of these types
would occur during the proposed
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project given the brief duration of
exposure of any given mammal, the
deep water in the survey area, and the
planned monitoring and mitigation
measures (see below). The following
subsections discuss in somewhat more
detail the possibilities of TTS, PTS, and
non-auditory physical effects.
Temporary Threshold Shift (TTS)
TTS is the mildest form of hearing
impairment that can occur during
exposure to a strong sound (Kryter,
1985). While experiencing TTS, the
hearing threshold rises and a sound
must be stronger in order to be heard.
In terrestrial mammals, TTS can last
from minutes or hours to (in cases of
strong TTS) days. For sound exposures
at or somewhat above the TTS
threshold, hearing sensitivity in both
terrestrial and marine mammals
recovers rapidly after exposure to the
noise ends. Few data on sound levels
and durations necessary to elicit mild
TTS have been obtained for marine
mammals, and none of the published
data concern TTS elicited by exposure
to multiple pulses of sound. Available
data on TTS in marine mammals are
summarized in Southall et al. (2007).
For toothed whales exposed to single
short pulses, the TTS threshold appears
to be, to a first approximation, a
function of the energy content of the
pulse (Finneran et al., 2002, 2005).
Given the available data, the received
energy level of a single seismic pulse
(with no frequency weighting) might
need to be approximately 186 dB re 1
μPa2•s (i.e., 186 dB SEL or
approximately 196 201 dB re 1 μPa rms
in order to produce brief, mild TTS.
Exposure to several strong seismic
pulses that each have received levels
near 190 dB re 1 μPa rms might result
in cumulative exposure of
approximately 186 dB SEL and thus
slight TTS in a small odontocete,
assuming the TTS threshold is (to a first
approximation) a function of the total
received pulse energy. The distances
from the Langseth’s airguns at which the
received energy level (per pulse, flatweighted) would be expected to be
greater than or equal to 190 dB re 1 μPa
rms are estimated in Table 1. Levels
greater than or equal to 190 dB re 1 μPa
rms are expected to be restricted to radii
no more than 380 m (1246 ft) (See Table
1). For an odontocete closer to the
surface, the maximum radius with
greater than or equal to 190 dB re 1 μPa
rms would be smaller.
The above TTS information for
odontocetes is derived from studies on
the bottlenose dolphin and beluga.
There is no published TTS information
for other types of cetaceans. However,
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preliminary evidence from a harbor
porpoise exposed to airgun sound
suggests that its TTS threshold may
have been lower (Lucke et al., 2007).
For baleen whales, there are no data,
direct or indirect, on levels or properties
of sound that are required to induce
TTS. The frequencies to which baleen
whales are most sensitive are assumed
to be lower than those to which
odontocetes are most sensitive, and
natural background noise levels at those
low frequencies tend to be higher. As a
result, auditory thresholds of baleen
whales within their frequency band of
best hearing are believed to be higher
(less sensitive) than are those of
odontocetes at their best frequencies
(Clark and Ellison, 2004). From this, it
is suspected that received levels causing
TTS onset may also be higher in baleen
whales (Southall et al., 2007). In any
event, no cases of TTS are expected
given three considerations: (1) the low
abundance of baleen whales in most
parts of the planned study area; (2) the
strong likelihood that baleen whales
would avoid the approaching airguns
(or vessel) before being exposed to
levels high enough for TTS to occur;
and (3) the mitigation measures that are
planned.
In pinnipeds, TTS thresholds
associated with exposure to brief pulses
(single or multiple) of underwater sound
have not been measured. Initial
evidence from more prolonged (nonpulse) exposures suggested that some
pinnipeds (harbor seals in particular)
incur TTS at somewhat lower received
levels than do small odontocetes
exposed for similar durations (Kastak et
al., 1999, 2005; Ketten et al., 2001). The
TTS threshold for pulsed sounds has
been indirectly estimated as being an
SEL of approximately 171 dB re 1
μPa2•s (Southall et al., 2007), which
would be equivalent to a single pulse
with received level of approximately
181 - 186 dB re 1 μPa (rms), or a series
of pulses for which the highest rms
values are a few dB lower.
Corresponding values for California sea
lions and northern elephant seals
(Mirounga angustirostris) are likely to be
higher (Kastak et al., 2005).
NMFS (1995, 2000) concluded that
cetaceans and pinnipeds should not be
exposed to pulsed underwater noise at
received levels exceeding 180 and 190
dB re 1 μPa rms, respectively. Those
sound levels are not considered to be
the levels above which TTS might
occur. Rather, they were the received
levels above which, in the view of a
panel of bioacoustics specialists
convened by NMFS before TTS
measurements for marine mammals
started to become available, one could
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21639
not be certain that there would be no
injurious effects, auditory or otherwise,
to marine mammals. As summarized
above and in Southall et al. (2007), data
that are now available imply that TTS
is unlikely to occur in most odontocetes
(and probably mysticetes as well) unless
they are exposed to a sequence of
several airgun pulses in which the
strongest pulse has a received level
substantially exceeding 180 dB re 1 μPa
rms. On the other hand, for the harbor
seal and any species with similarly low
TTS thresholds (possibly including the
harbor porpoise), TTS may occur upon
exposure to one or more airgun pulses
whose received level equals the NMFS
‘‘do not exceed’’ value of 190 dB re 1
μPa rms. That criterion corresponds to
a single-pulse SEL of
175 - 180 dB re 1 μPa2•s in typical
conditions, whereas TTS is suspected to
be possible (in harbor seals) with a
cumulative SEL of approximately 171
dB re 1 μPa2•s.
Permanent Threshold Shift (PTS)
When PTS occurs, there is physical
damage to the sound receptors in the
ear. In severe cases, there can be total or
partial deafness, while in other cases;
the animal has an impaired ability to
hear sounds in specific frequency ranges
(Kryter, 1985).
There is no specific evidence that
exposure to pulses of airgun sound can
cause PTS in any marine mammal, even
with large arrays of airguns. However,
given the possibility that mammals
close to an airgun array might incur at
least mild TTS, there has been further
speculation about the possibility that
some individuals occurring very close to
airguns might incur PTS (Richardson et
al., 1995, p. 372ff). Single or occasional
occurrences of mild TTS are not
indicative of permanent auditory
damage.
Relationships between TTS and PTS
thresholds have not been studied in
marine mammals, but are assumed to be
similar to those in humans and other
terrestrial mammals. PTS might occur at
a received sound level at least several
decibels above that inducing mild TTS
if the animal were exposed to strong
sound pulses with rapid rise time see
Appendix B (6) of L-DEO’s EA. Based on
data from terrestrial mammals, a
precautionary assumption is that the
PTS threshold for impulse sounds (such
as airgun pulses as received close to the
source) is at least 6 dB higher than the
TTS threshold on a peak-pressure basis,
and probably greater than 6 dB (Southall
et al., 2007). On an SEL basis, Southall
et al. (2007:441–4) estimated that
received levels would need to exceed
the TTS threshold by at least 15 dB for
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there to be risk of PTS. Thus, for
cetaceans they estimate that the PTS
threshold might be a mammal-weighted
(M-weighted) SEL (for the sequence of
received pulses) of approximately 198
dB re 1 μPa2•s (15 dB higher than the
TTS threshold for an impulse), where
the SEL value is accumulated over the
sequence of pulses. Additional
assumptions had to be made to derive
a corresponding estimate for pinnipeds,
as the only available data on TTSthresholds in pinnipeds pertain to nonimpulse sound. Southall et al. (2007)
estimate that the PTS threshold could be
a cumulative Mpw-weighted SEL of
approximately 186 dB re 1 μPa2•s in the
harbor seal exposed to impulse sound.
The PTS threshold for the California sea
lion and northern elephant seal the PTS
threshold would probably be higher,
given the higher TTS thresholds in
those species.
Southall et al. (2007) also note that,
regardless of the SEL, there is concern
about the possibility of PTS if a cetacean
or pinniped received one or more pulses
with peak pressure exceeding 230 or
218 dB re 1 μPa (peak), respectively. A
peak pressure of 230 dB re 1 FPa (3.2
bar•m, 0–peak) would only be found
within a few meters of the largest (360
in3) airgun in the planned airgun array
(Caldwell and Dragoset, 2000). A peak
pressure of 218 dB re 1 μPa could be
received somewhat farther away; to
estimate that specific distance, one
would need to apply a model that
accurately calculates peak pressures in
the nearfield around an array of airguns.
Given the higher level of sound
necessary to cause PTS as compared
with TTS, it is considerably less likely
that PTS would occur. Baleen whales
generally avoid the immediate area
around operating seismic vessels, as do
some other marine mammals and sea
turtles. The planned monitoring and
mitigation measures, including visual
monitoring, PAM, power downs, and
shut downs of the airguns when
mammals are seen within or
approaching the exclusion zones, will
further reduce the probability of
exposure of marine mammals to sounds
strong enough to induce PTS.
Non-auditory Physiological Effects
Non-auditory physiological effects or
injuries that theoretically might occur in
marine mammals exposed to strong
underwater sound include stress,
neurological effects, bubble formation,
resonance, and other types of organ or
tissue damage (Cox et al., 2006; Southall
et al., 2007). Studies examining such
effects are limited. However, resonance
(Gentry, 2002) and direct noise-induced
bubble formation (Crum et al., 2005) are
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not expected in the case of an impulsive
source like an airgun array. If seismic
surveys disrupt diving patterns of deepdiving species, this might perhaps result
in bubble formation and a form of the
bends, as speculated to occur in beaked
whales exposed to sonar. However,
there is no specific evidence of this
upon exposure to airgun pulses.
In general, very little is known about
the potential for seismic survey sounds
(or other types of strong underwater
sounds) to cause non-auditory physical
effects in marine mammals. Such
effects, if they occur at all, would
presumably be limited to short distances
and to activities that extend over a
prolonged period. The available data do
not allow identification of a specific
exposure level above which nonauditory effects can be expected
(Southall et al., 2007), or any
meaningful quantitative predictions of
the numbers (if any) of marine mammals
that might be affected in those ways.
Marine mammals that show behavioral
avoidance of seismic vessels, including
most baleen whales, some odontocetes,
and some pinnipeds, are especially
unlikely to incur non-auditory physical
effects. Also, the planned mitigation
measures (see section XI), including
shut downs of the airguns, will reduce
any such effects that might otherwise
occur.
Strandings and Mortality
Marine mammals close to underwater
detonations of high explosives can be
killed or severely injured, and the
auditory organs are especially
susceptible to injury (Ketten et al., 1993;
Ketten, 1995). However, explosives are
no longer used for marine seismic
research or commercial seismic surveys,
and have been replaced entirely by
airguns or related non-explosive pulse
generators. Airgun pulses are less
energetic and have slower rise times,
and there is no specific evidence that
they can cause serious injury, death, or
stranding even in the case of large
airgun arrays. However, the association
of mass strandings of beaked whales
with naval exercises and, in one case, an
L-DEO seismic survey (Malakoff, 2002;
Cox et al., 2006), has raised the
possibility that beaked whales exposed
to strong pulsed sounds may be
especially susceptible to injury and/or
behavioral reactions that can lead to
stranding (e.g., Hildebrand, 2005;
Southall et al., 2007). Appendix B (7) of
L-DEO’s EA provides additional details.
Specific sound-related processes that
lead to strandings and mortality are not
well documented, but may include: (1)
swimming in avoidance of a sound into
shallow water; (2) a change in behavior
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(such as a change in diving behavior)
that might contribute to tissue damage,
gas bubble formation, hypoxia, cardiac
arrhythmia, hypertensive hemorrhage or
other forms of trauma; (3) a
physiological change such as a
vestibular response leading to a
behavioral change or stress-induced
hemorrhagic diathesis, leading in turn
to tissue damage; and (4) tissue damage
directly from sound exposure, such as
through acoustically mediated bubble
formation and growth or acoustic
resonance of tissues. There are
increasing indications that gas-bubble
disease (analogous to ‘‘the bends’’),
induced in supersaturated tissue by a
behavioral response to acoustic
exposure, could be a pathologic
mechanism for the strandings and
mortality of some deep-diving cetaceans
exposed to sonar. However, the
evidence for this remains circumstantial
and associated with exposure to naval
mid-frequency sonar, not seismic
surveys (Cox et al., 2006; Southall et al.,
2007).
Seismic pulses and mid-frequency
sonar signals are quite different, and
some mechanisms by which sonar
sounds have been hypothesized to affect
beaked whales are unlikely to apply to
airgun pulses. Sounds produced by
airgun arrays are broadband impulses
with most of the energy below 1 kHz.
Typical military mid-frequency sonars
emit non-impulse sounds at frequencies
of 2–10 kHz, generally with a relatively
narrow bandwidth at any one time. A
further difference between seismic
surveys and naval exercises is that naval
exercises can involve sound sources on
more than one vessel. Thus, it is not
appropriate to assume that there is a
direct connection between the effects of
military sonar and seismic surveys on
marine mammals. However, evidence
that sonar signals can, in special
circumstances, lead (at least indirectly)
to physical damage and mortality (e.g.,
Balcomb and Claridge, 2001; NOAA and
USN, 2001; Jepson et al., 2003;
Fernandez et al., 2004, 2005;
Hildebrand, 2005; Cox et al., 2006)
suggests that caution is warranted when
dealing with exposure of marine
mammals to any high-intensity pulsed
sound.
There is no conclusive evidence of
cetacean strandings or deaths at sea as
a result of exposure to seismic surveys,
but a few cases of strandings in the
general area where a seismic survey was
ongoing have led to speculation
concerning a possible link between
seismic surveys and strandings.
Suggestions that there was a link
between seismic surveys and strandings
of humpback whales in Brazil (Engel et
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al., 2004) were not well founded (IAGC,
2004; IWC, 2007). In September 2002,
there was a stranding of two Cuvier’s
beaked whales (Ziphius cavirostris) in
the Gulf of California, Mexico, when the
L-DEO vessel R/V Maurice Ewing was
operating a 20–airgun, 8490–in3 airgun
array in the general area. The link
between the stranding and the seismic
surveys was inconclusive and not based
on any physical evidence (Hogarth,
2002; Yoder, 2002). Nonetheless, the
Gulf of California incident plus the
beaked whale strandings near naval
exercises involving use of midfrequency sonar suggests a need for
caution in conducting seismic surveys
in areas occupied by beaked whales
until more is known about effects of
seismic surveys on those species
(Hildebrand, 2005).
No injuries of beaked whales are
anticipated during the proposed study
because of: (1) the high likelihood that
any beaked whales nearby would avoid
the approaching vessel before being
exposed to high sound levels; (2) the
proposed monitoring and mitigation
measures; and (3) differences between
the sound sources operated by L-DEO
and those involved in the naval
exercises associated with strandings.
Possible Effects of Multibeam
Echosounder (MBES) Signals
The Simrad EM120 12–kHz MBES
will be operated from the source vessel
continuously during the planned study.
Sounds from the MBES are very short
pulses, occurring for 2–15 ms once
every 5 20 s, depending on water depth.
Most of the energy in the sound pulses
emitted by this MBES is at frequencies
near 12 kHz, and the maximum source
level is 242 dB re 1 μPa• m (rms). The
beam is narrow (1°) in fore-aft extent
and wide (150°) in the cross-track
extent. Each ping consists of nine
successive fan-shaped transmissions
(segments) at different cross-track
angles. Any given mammal at depth
near the trackline would be in the main
beam for only one or two of the nine
segments. Also, marine mammals that
encounter the Simrad EM120 are
unlikely to be subjected to repeated
pulses because of the narrow fore aft
width of the beam and will receive only
limited amounts of pulse energy
because of the short pulses. Animals
close to the ship (where the beam is
narrowest) are especially unlikely to be
ensonified for more than one 2 15 ms
pulse (or two pulses if in the overlap
area). Similarly, Kremser et al. (2005)
noted that the probability of a cetacean
swimming through the area of exposure
when an MBES emits a pulse is small.
The animal would have to pass the
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transducer at close range and be
swimming at speeds similar to the
vessel in order to receive the multiple
pulses that might result in sufficient
exposure to cause TTS.
Navy sonars that have been linked to
avoidance reactions and stranding of
cetaceans: (1) generally have longer
pulse duration than the Simrad EM120,
and (2) are often directed close to
omnidirectionally versus more
downward for the Simrad EM120. The
area of possible influence of the MBES
is much smaller a narrow band below
the source vessel. The duration of
exposure for a given marine mammal
can be much longer for naval sonar.
During L-DEO’s operations, the
individual pulses will be very short, and
a given mammal would not receive
many of the downward-directed pulses
as the vessel passes by the area.
Masking - Marine mammal
communications will not be masked
appreciably by the MBES signals given
the low duty cycle of the echosounder
and the brief period when an individual
mammal is likely to be within its beam.
Furthermore, in the case of baleen
whales, the MBES signals (12 kHz) do
not overlap with the predominant
frequencies in the calls, which would
avoid any significant masking.
Behavioral Responses: Behavioral
reactions of free-ranging marine
mammals to sonar, echosounders, and
other sound sources appear to vary by
species and circumstance. Observed
reactions have included silencing and
dispersal by sperm whales (Watkins et
al., 1985), increased vocalizations and
no dispersal by pilot whales
(Globicephala spp.) (Rendell and
Gordon, 1999), and the previouslymentioned beachings by beaked whales.
During exposure to a 21–25 kHz sonar
with a source level of 215 dB re 1
μPa•m, gray whales reacted by orienting
slightly away from the source and being
deflected from their course by
approximately 200 m (Frankel, 2005).
When a 38–kHz echosounder and a
150–kHz acoustic Doppler current
profiler were transmitting during
studies in the Eastern Tropical Pacific,
baleen whales showed no significant
responses, while spotted and spinner
dolphins were detected slightly more
often and beaked whales less often
during visual surveys (Gerrodette and
Pettis, 2005).
Captive bottlenose dolphins exhibited
changes in behavior when exposed to 1–
s tonal signals at frequencies similar to
those that will be emitted by the MBES
used by L-DEO, and to shorter
broadband pulsed signals. Behavioral
changes typically involved what
appeared to be deliberate attempts to
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21641
avoid the sound exposure (Schlundt et
al., 2000; Finneran et al., 2002; Finneran
and Schlundt, 2004). The relevance of
those data to free-ranging odontocetes is
uncertain, and in any case, the test
sounds were quite different in duration
as compared with those from an MBES.
Very few data are available on the
reactions of pinnipeds to sonar sounds
at frequencies similar to those used
during seismic operations. Hastie and
Janik (2007) conducted a series of
behavioral response tests on two captive
gray seals to determine their reactions to
underwater operation of a 375–kHz
multibeam imaging sonar that included
significant signal components down to 6
kHz. Results indicated that the two seals
reacted to the sonar signal by
significantly increasing their dive
durations. Because of the likely brevity
of exposure to the MBES sounds,
pinniped reactions are expected to be
limited to startle or otherwise brief
responses of no lasting consequence to
the animals.
Hearing Impairment and Other
Physical Effects: Given recent stranding
events that have been associated with
the operation of naval sonar, there is
concern that mid-frequency sonar
sounds can cause serious impacts to
marine mammals (see above). However,
the MBES proposed for use by L-DEO is
quite different than sonars used for navy
operations. Pulse duration of the MBES
is very short relative to the naval sonars.
Also, at any given location, an
individual marine mammal would be in
the beam of the MBES for much less
time given the generally downward
orientation of the beam and its narrow
fore-aft beamwidth; navy sonars often
use nearhorizontally-directed sound.
Those factors would all reduce the
sound energy received from the MBES
rather drastically relative to that from
the sonars used by the navy.
Given the maximum source level of
242 dB re 1 μPa•m rms, the received
level for an animal within the MBES
beam 100 m (328 ft) below the ship
would be approximately 202 dB re 1 μPa
rms, assuming 40 dB of spreading loss
over 100 m (328 ft) (circular spreading).
Given the narrow beam, only one pulse
is likely to be received by a given
animal as the ship passes overhead. The
received energy level from a single
pulse ofduration 15 ms would be about
184 dB re 1 μPa2•s, i.e., 202 dB + 10 log
(0.015 s). That is below the TTS
threshold for a cetacean receiving a
single non-impulse sound (195 dB re 1
μPa2•s) and even further below the
anticipated PTS threshold (215 dB re 1
μPa2•s) (Southall et al., 2007). In
contrast, an animal that was only 10 m
(32 ft) below the MBES when a ping is
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emitted would be expected to receive a
level approximately 20 dB higher, i.e.,
204 dB re 1 μPa2•s in the case of the
EM120. That animal might incur some
TTS (which would be fully recoverable),
but the exposure would still be below
the anticipated PTS threshold for
cetaceans. As noted by Burkhardt et al.,
(2007, 2008), cetaceans are very unlikely
to incur PTS from operation of scientific
sonars on a ship that is underway.
In the harbor seal, the TTS threshold
for non-impulse sounds is about 183 dB
re 1 μPa2•s, as compared with
approximately 195 dB re 1 μPa2•s in
odontocetes (Kastak et al., 2005;
Southall et al., 2007). TTS onset occurs
at higher received energy levels in the
California sea lion and northern
elephant seal than in the harbor seal. A
harbor seal as much as 100 m (328 ft)
below the Langseth could receive a
single MBES pulse with received energy
level of greater than or equal to 184 dB
re 1 μPa2•s (as calculated in the toothed
whale subsection above) and thus could
incur slight TTS. Species of pinnipeds
with higher TTS thresholds would not
incur TTS unless they were closer to the
transducers when a sonar ping was
emitted. However, the SEL criterion for
PTS in pinnipeds (203 dB re 1 μPa2•s)
might be exceeded for a ping received
within a few meters of the transducers,
although the risk of PTS is higher for
certain species (e.g., harbor seal). Given
the intermittent nature of the signals
and the narrow MBES beam, only a
small fraction of the pinnipeds below
(and close to) the ship would receive a
pulse as the ship passed overhead.
Possible Effects of the Sub-bottom
Profiler Signals
An SBP may be operated from the
source vessel at times during the
planned study. Sounds from the subbottom profiler are very short pulses,
occurring for 1 4 ms once every second.
Most of the energy in the sound pulses
emitted by the SBP is at 3.5 kHz, and
the beam is directed downward in a
narrow beam with a spacing of up to 15°
and a fan width up to 30°. The subbottom profiler on the Langseth has a
maximum source level of 204 dB re 1
μPa•m. Kremser et al. (2005) noted that
the probability of a cetacean swimming
through the area of exposure when a
bottom profiler emits a pulse is smalleven for an SBP more powerful than
that on the Langseth if the animal was
in the area, it would have to pass the
transducer at close range and in order to
be subjected to sound levels that could
cause TTS.
Masking - Marine mammal
communications will not be masked
appreciably by the sub-bottom profiler
signals given their directionality and the
brief period when an individual
mammal is likely to be within its beam.
Furthermore, in the case of most baleen
whales, the SBP signals do not overlap
with the predominant frequencies in the
calls, which would avoid significant
masking.
Behavioral Responses - Marine
mammal behavioral reactions to other
pulsed sound sources are discussed
above, and responses to the SBP are
likely to be similar to those for other
pulsed sources if received at the same
levels. However, the pulsed signals from
the SBP are considerably weaker than
those from the MBES. Therefore,
behavioral responses would not be
expected unless marine mammals were
to approach very close to the source.
Hearing Impairment and Other
Physical Effects: It is unlikely that the
SBP produces pulse levels strong
enough to cause hearing impairment or
other physical injuries even in an
animal that is (briefly) in a position near
the source. The SBP is usually operated
simultaneously with other higher-power
acoustic sources. Many marine
mammals will move away in response
to the approaching higher-power
sources or the vessel itself before the
mammals would be close enough for
there to be any possibility of effects
from the less intense sounds from the
SBP. In the case of mammals that do not
avoid the approaching vessel and its
various sound sources, mitigation
measures that would be applied to
minimize effects of other sources would
further reduce or eliminate any minor
effects of the SBP.
Possible Effects of the Acoustic Release
Signals
The acoustic release transponder used
to communicate with the OBS uses
frequencies of 9 13 kHz. Once the OBS
is ready to be retrieved, an acoustic
release transponder interrogates the
OBS at a frequency of 9 11 kHz, and a
response is received at a frequency of 9
13 kHz. However, these signals will be
used very intermittently. The source
level of the release signal is 190 dB (re
1 μPa at 1 m). An animal would have
to pass by the OBS at close range when
the signal is emitted in order to be
exposed to any pulses at that level. The
sound is expected to undergo a
spreading loss of approximately 40 dB
in the first 100 m (328 ft). Thus, any
animals located 100 m (328 ft) or more
from the signal will be exposed to very
weak signals (less than 150 dB) that are
not expected to have any effects. The
signal is used only for short intervals to
interrogate and trigger the release of the
OBS and consists of pulses rather than
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a continuous sound. Given the short
duration use of this signal and rapid
attenuation in seawater it is unlikely
that the acoustic release signals would
significantly affect marine mammals or
sea turtles through masking,
disturbance, or hearing impairment.
Any effects likely would be negligible
given the brief exposure at presumable
low levels.
Proposed Monitoring and Mitigation
Measures
Monitoring
L-DEO proposes to sponsor marine
mammal monitoring during the present
project, in order to implement the
proposed mitigation measures that
require real-time monitoring, and to
satisfy the anticipated monitoring
requirements of the IHA. L-DEO’s
proposed Monitoring Plan is described
below this section. L-DEO understands
that this monitoring plan will be subject
to review by NMFS, and that
refinements may be required. The
monitoring work described here has
been planned as a self-contained project
independent of any other related
monitoring projects that may be
occurring simultaneously in the same
regions. L-DEO is prepared to discuss
coordination of its monitoring program
with any related work that might be
done by other groups insofar as this is
practical and desirable.
Vessel-based Visual Monitoring
Marine mammal visual observers
(MMVOs) will be based aboard the
seismic source vessel and will watch for
marine mammals and turtles near the
vessel during daytime airgun operations
and during any start-ups at night. The
MMVOs will also watch for marine
mammals and turtles near the seismic
vessel for at least 30 minutes (min) prior
to the start of airgun operations after an
extended shut down. When feasible,
MMVOs will also observe during
daytime periods when the seismic
system is not operating for comparison
of sighting rates and behavior with
versus without airgun operations. Based
on the MMVOs’ observations, the
Langseth will power down the airguns
or shut down the airguns when marine
mammals are observed within or about
to enter a designated exclusion zone
(EZ). The EZ is a region in which a
possibility exists of adverse effects on
animal hearing or other physical effects.
During seismic operations in the
Endeavour MPA, at least three MMVOs
will be based aboard the Langseth.
MMVOs will be appointed by L-DEO
with NMFS concurrence. At least one
MMVO, and when feasible, two
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MMVOs, will monitor marine mammals
and turtles near the seismic vessel
during ongoing daytime operations and
nighttime start ups of the airguns. Use
of two simultaneous observers will
increase the proportion of the animals
present near the source vessel that are
detected. MMVO(s) will be on duty in
shifts of duration no longer than 4 h.
Other crew will also be instructed to
assist in detecting marine mammals and
turtles and implementing mitigation
requirements (if feasible). Before the
start of the seismic survey the crew will
be given additional instruction
regarding how to do so.
The Langseth is a suitable platform for
marine mammal and turtle observations.
When stationed on the observation
platform, the eye level will be
approximately 18 m (59 ft) above sea
level, and the observer will have a good
view around the entire vessel. During
daytime, the MMVOs will scan the area
around the vessel systematically with
reticle binoculars (e.g., 7 50 Fujinon),
Big-eye binoculars (25 150), and with
the naked eye. During darkness, night
vision devices (NVDs) will be available
(ITT F500 Series Generation 3
binocularimage intensifier or
equivalent), when required. Laser
rangefinding binoculars (Leica LRF 1200
laser rangefinder or equivalent) will be
available to assist with distance
estimation. Those are useful in training
observers to estimate distances visually,
but are generally not useful in
measuring distances to animals directly;
that is done primarily with the reticles
in the binoculars.
The vessel-based monitoring will
provide data to estimate the numbers of
marine mammals exposed to various
received sound levels, to document any
apparent disturbance reactions or lack
thereof, and thus to estimate the
numbers of mammals potentially
‘‘taken’’ by harassment. It will also
provide the information needed in order
to power down or shut down the
airguns at times when mammals and
turtles are present in or near the safety
radii. When a sighting is made, the
following information about the sighting
will be recorded:
1. Species, group size, age/size/sex
categories (if determinable), behavior
when first sighted and after initial
sighting, heading (if consistent), bearing
and distance from seismic vessel,
sighting cue, apparent reaction to the
airguns or vessel (e.g., none, avoidance,
approach, paralleling, etc.), and
behavioral pace.
2. Time, location, heading, speed,
activity of the vessel, sea state,
visibility, and sun glare.
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The data listed under (2) will also be
recorded at the start and end of each
observation watch, and during a watch
whenever there is a change in one or
more of the variables.
All observations and power-downs or
shut downs will be recorded in a
standardized format. Data will be
entered into a custom database using a
notebook computer. The accuracy of the
data entry will be verified by
computerized validity data checks as
the data are entered and by subsequent
manual checking of the database.
Preliminary reports will be prepared
during the field program and summaries
forwarded to the operating institution’s
shore facility and to NSF weekly or
more frequently.
Results from the vessel-based
observations will provide:
1. The basis for real-time mitigation
(airgun power-down or shut-down).
2. Information needed to estimate the
number of marine mammals potentially
taken by harassment, which must be
reported to NMFS per terms of MMPA
authorizations or regulations.
3. Data on the occurrence,
distribution, and activities of marine
mammals and turtles in the area where
the seismic study is conducted.
4. Data on the behavior and
movement patterns of marine mammals
and turtles seen at times with and
without seismic activity.
Passive Acoustic Monitoring
Passive acoustic monitoring (PAM)
will take place to complement the visual
monitoring program. Visual monitoring
typically is not effective during periods
of bad weather or at night, and even
with good visibility, is unable to detect
marine mammals when they are below
the surface or beyond visual range.
Acoustical monitoring can be used in
addition to visual observations to
improve detection, identification,
localization, and tracking of cetaceans.
The acoustic monitoring will serve to
alert visual observers (if on duty) when
vocalizing cetaceans are detected. It is
only useful when marine mammals call,
but it can be effective either by day or
by night, and does not depend on good
visibility. It will be monitored in real
time so that the visual observers can be
advised when cetaceans are detected.
When bearings (primary and mirrorimage) to calling cetacean(s) are
determined, the bearings will be relayed
to the visual observer to help him/her
sight the calling animal(s).
The PAM system consists of hardware
(i.e., hydrophones) and software. The
‘‘wet end’’ of the system consists of a
low-noise, towed hydrophone array that
is connected to the vessel by a ‘‘hairy’’
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21643
faired cable. The array will be deployed
from a winch located on the back deck.
A deck cable will connect from the
winch to the main computer lab where
the acoustic station and signal
conditioning and processing system will
be located. The lead-in from the
hydrophone array is approximately 400
m (1312 ft) long, and the active part of
the hydrophone array is approximately
50 m (164 ft) long. The hydrophone
array is typically towed at depths of 20
m (66 ft) to 30 m (98 ft).
The towed hydrophones will be
monitored 24 h per day while at the
seismic survey area during airgun
operations, and during most periods
when the Langseth is underway while
the airguns are not operating. One MMO
will monitor the acoustic detection
system at any one time, by listening to
the signals from two channels via
headphones and/or speakers and
watching the real-time spectrographic
display for frequency ranges produced
by cetaceans. MMOs monitoring the
acoustical data will be on shift for 1 6
h at a time. Besides the visual MMOs,
an additional MMO with primary
responsibility for PAM will also be
aboard. All MMOs are expected to rotate
through the PAM position, although the
most experienced with acoustics will be
on PAM duty more frequently.
When a vocalization is detected while
visual observations are in progress, the
acoustic MMO will contact the visual
MMO immediately, to alert him/her to
the presence of cetaceans (if they have
not already been seen), and to allow a
power down or shut down to be
initiated, if required. The information
regarding the call will be entered into a
database. The data to be entered include
an acoustic encounter identification
number, whether it was linked with a
visual sighting, date, time when first
and last heard and whenever any
additional information was recorded,
position and water depth when first
detected, bearing if determinable,
species or species group (e.g.,
unidentified dolphin, sperm whale),
types and nature of sounds heard (e.g.,
clicks, continuous, sporadic, whistles,
creaks, burst pulses, strength of signal,
etc.), and any other notable information.
The acoustic detection can also be
recorded for further analysis.
Mitigation
L-DEO’s mitigation procedures are
based on protocols used during previous
L-DEO seismic research cruises as
approved by NMFS, and on best
practices recommended in Richardson
et al. (1995), Pierson et al. (1998), and
Weir and Dolman (2007). The measures
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are described in detail below this
section.
hsrobinson on PROD1PC76 with NOTICES
Proposed Exclusion Zones
As noted earlier, L-DEO modeled
received sound levels for the 36–airgun
array and for a single 1900LL 40–in3
airgun (which will be used during
power downs), in relation to distance
and direction from the airguns. Based
on the modeling for deep water, the
distances from the source where sound
levels are predicted to be 190, 180, and
160 dB re 1 μPa (rms) were determined
(Table 1). The 180- and 190–dB radii
vary with tow depth of the airgun array
and range up to 1220 m (4002 ft) and
380 m (1246 ft), respectively. The 180and 190–dB levels are shut-down
criteria applicable to cetaceans and
pinnipeds, respectively, as specified by
NMFS (2000); these levels were used to
establish the exclusion zones (EZ). If the
MMO detects marine mammal(s) or
turtle(s) within or about to enter the
appropriate safety radii, the airguns will
be powered down (or shut down if
necessary) immediately.
Mitigation During Operations
Mitigation measures that will be
adopted during the L-DEO survey
include: (1) speed or course alteration,
provided that doing so will not
compromise operational safety
requirements; (2) power-down
procedures; (3) shut-down procedures;
(4) ramp-up procedures; and (5) special
procedures for species of particular
concern.
Speed or Course Alteration - If a
marine mammal or sea turtle is detected
outside the safety zone and, based on its
position and the relative motion, is
likely to enter the safety zone, the
vessel’s speed and/or direct course may
be changed. This would be done if
practicable while minimizing the effect
on the planned science objectives. The
activities and movements of the marine
mammal or sea turtle (relative to the
seismic vessel) will then be closely
monitored to determine whether the
animal is approaching the applicable
safety zone. If the animal appears likely
to enter the safety zone, further
mitigative actions will be taken, i.e.,
either further course alterations or a
power down or shut down of the
airguns. Typically, during seismic
operations that use hydrophone
streamers, the source vessel is unable to
change speed or course and one or more
alternative mitigation measures (see
below) will need to be implemented.
Power-down Procedures - A powerdown involves decreasing the number of
airguns in use such that the radius of
the 180–dB (or 190–dB) zone is
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decreased to the extent that marine
mammals or turtles are no longer in or
about to enter the safety zone. A powerdown of the airgun array can also occur
when the vessel is moving from one
seismic line to another. During a powerdown for mitigation, one airgun will be
operated. The continued operation of
one airgun is intended to alert marine
mammals and turtles to the presence of
the seismic vessel in the area. In
contrast, a shut-down occurs when all
airgun activity is suspended.
If a marine mammal or turtle is
detected outside the EZ but is likely to
enter the EZ, and if the vessel’s speed
and/or course cannot be changed to
avoid having the animal enter the safety
radius, the airguns will be powered
down before the animal is within the
EZ. Likewise, if a mammal or turtle is
already within the EZ when first
detected, the airguns will be powered
down immediately. During a powerdown of the airgun array, the 40–in3
airgun will be operated. If a marine
mammal or turtle is detected within or
near the smaller EZ around that single
airgun (Table 1), it will be shut down
(see next subsection).
Following a power-down, airgun
activity will not resume until the marine
mammal or turtle has cleared the EZ.
The animal will be considered to have
cleared the EZ if it: (1) is visually
observed to have left the EZ; or (2) has
not been seen within the zone for 15
min in the case of small odontocetes; or
(3) has not been seen within the zone for
30 min in the case of mysticetes and
large odontocetes, including sperm,
pygmy sperm, dwarf sperm, and beaked
whales; or (4) the vessel has moved
outside the EZ for turtles, i.e.,
approximately 5 to 20 min, depending
on the sighting distance, vessel speed,
and tow-depth.
During airgun operations following a
power down (or shut down) whose
duration has exceeded the limits
specified above, the airgun array will be
ramped up gradually (see below).
Shut-down Procedures - During a
power down, the operating airgun will
be shut down if a marine mammal or
turtle is seen within or approaching the
EZ for a single airgun. Shut-downs will
be implemented: (1) if an animal enters
the exclusion zone of the single airgun
after a power-down has been initiated,
or (2) if an animal is initially seen
within the exclusion zone of a single
airgun when more than one airgun
(typically the full array) is operating.
Airgun activity will not resume until
the marine mammal or turtle has cleared
the EZ, or until the visual marine
mammal observer (MMVO) is confident
that the animal has left the vicinity of
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the vessel. Criteria for judging that the
animal has cleared the EZ will be as
described in the preceding subsection.
The airguns will be shut down if a
North Pacific right whale is sighted from
the vessel, even if it is located outside
the EZ, because of the rarity and
sensitive status of this species.
Ramp-up Procedures - A ramp-up
procedure will be followed when the
airgun array begins operating after a
specified period without airgun
operations or when a power-down has
exceeded that period. It is proposed
that, for the present cruise, this period
would be approximately 9 min. This
period is based on the largest modeled
180–dB radius for the 36–airgun array
(see Table 1) in relation to the planned
speed of the Langseth while shooting
the airguns. Similar periods
(approximately 8 10 min) were used
during previous L-DEO surveys.
Ramp-up will begin with the smallest
gun in the array (40 in3). Airguns will
be added in a sequence such that the
source level of the array will increase in
steps not exceeding 6 dB per 5–min
period over a total duration of about 30
- 40 min. During ramp-up, the MMVOs
will monitor the safety zone and if
marine mammals or turtles are sighted,
a course/speed change, power down, or
shut down will be implemented as
though the full array were operational.
If the complete EZ has not been
visible for at least 30 min prior to the
start of operations in either daylight or
nighttime, ramp-up will not commence
unless at least one airgun (40 in3 or
similar) has been operating during the
interruption of seismic survey
operations. Given these provisions, it is
likely that the airgun array will not be
ramped up from a complete shut-down
at night or in thick fog, because the
outer part of the EZ for that array will
not be visible during those conditions.
If one airgun has operated during a
power-down period, ramp-up to full
power will be permissible at night or in
poor visibility, on the assumption that
marine mammals and turtles will be
alerted to the approaching seismic
vessel by the sounds from the single
airgun and could move away if they
choose. Ramp-up of the airguns will not
be initiated if a sea turtle or marine
mammal is sighted within or near the
applicable zones during the day or close
to the vessel at night.
Shutdown if Injured or Dead Whale is
Found - In the unanticipated event that
any cases of marine mammal injury or
mortality are found and are judged
likely to have resulted from these
activities, L-DEO will cease operating
seismic airguns and report the incident
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to the Office of Protected Resources,
NMFS immediately.
hsrobinson on PROD1PC76 with NOTICES
Reporting
L-DEO will submit a report to NMFS
within 90 days after the end of the
cruise. The report will describe the
operations that were conducted and
sightings of marine mammals and
turtles near the operations. The report
will provide full documentation of
methods, results, and interpretation
pertaining to all monitoring. The 90–day
report will summarize the dates and
locations of seismic operations, and all
marine mammal and turtle sightings
(dates, times, locations, activities,
associated seismic survey activities).
The report will also include estimates of
the number and nature of exposures that
could result in ‘‘takes’’ of marine
mammals by harassment or in other
ways.
All injured or dead marine mammals
(regardless of cause) must be reported to
NMFS as soon as practicable. Report
should include species or description of
animal, condition of animal, location,
time first found, observed behaviors (if
alive) and photo or video, if available.
Estimated Take by Incidental
Harassment
Because of the mitigation measures
that will be required and the likelihood
that some cetaceans will avoid the area
around the operating airguns of their
own accord, NMFS does not expect any
marine mammals to approach the sound
source close enough to be injured (Level
A harassment). All anticipated takes
would be ‘‘takes by Level B
harassment’’, as described previously,
involving temporary behavioral
modifications or low-level physiological
effects.
Estimates of the numbers of marine
mammals that might be affected are
based on consideration of the number of
marine mammals that could be
disturbed appreciably by approximately
1800 km (1118 mi) of seismic surveys
during the proposed seismic program in
the Endeavor MPA.
It is assumed that, during
simultaneous operations of the airgun
array and the other sources, any marine
mammals close enough to be affected by
the MBES or SBP would already be
affected by the airguns. However,
whether or not the airguns are operating
simultaneously with the other sources,
marine mammals are expected to exhibit
no more than short-term and
inconsequential responses to the MBES
and SBP given their characteristics (e.g.,
narrow downward-directed beam) and
other considerations described in
section I of L-DEO’s application. Such
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reactions are not considered to
constitute ‘‘taking’’ (NMFS, 2001).
Therefore, no additional allowance is
included for animals that might be
affected by sound sources other than
airguns.
Density Estimates
There is very little information on the
cetaceans that occur in deep water off
the west coast of Vancouver Island, but
the waters off Oregon and Washington
have been studied in some detail (e.g.,
Green et al., 1992, 1993; Barlow, 1997,
2003; Barlow and Taylor, 2001;
Calambokidis and Barlow, 2004; Barlow
and Forney, 2007). The primary data
used to provide densities for the
proposed project area off southwestern
British Columbia (BC) were obtained
from the 1996, 2001, and 2005 NMFS/
SWFSC ‘‘ORCAWALE’’ or ‘‘CSCAPE’’
ship surveys off Oregon/Washington, as
synthesized by Barlow and Forney
(2007). The surveys took place up to
approximately 550 km (341 mi) offshore
from June or July through November or
December. Thus, the surveys included
effort in coastal, shelf/slope, and
offshore water, and they encompass the
August September period for the
proposed study. Systematic, offshore
survey data for pinnipeds are more
limited. The most comprehensive such
studies are reported by Bonnell et al.,
(1992) based on systematic aerial
surveys conducted in 1989 1990.
The waters off the west coast of
Vancouver Island are included in the
same ecological province as Oregon/
Washington, the California Coastal
Province (Longhurst, 2007). Thus,
information on cetaceans from Oregon/
Washington is relevant to the proposed
offshore study area far offshore of BC.
Although densities for BC are available
for some cetacean species (see Williams
and Thomas 2007), these are for inshore
coastal waters and would not be
representative of the densities occurring
in offshore areas. Although the cetacean
densities based on data from Barlow and
Forney (2007) better reflect those that
will be encountered during the ETOMO
study, the actual densities in the
Endeavour MPA are expected to be
lower still, as the survey effort off
Oregon/Washington covered offshore as
well as shelf and coastal waters, and it
included sightings for summer and fall.
Oceanographic conditions, including
occasional El Nino and La Nina events,
influence the distribution and numbers
of marine mammals present in the
NEPO, resulting in considerable year-toyear variation in the distribution and
abundance of many marine mammal
species (Forney and Barlow, 1998;
Buchanan et al., 2001; Escorza-Trevino,
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21645
2002; Ferrero et al., 2002; Philbrick et
al., 2003; Becker, 2007). Thus, for some
species the densities derived from
recent surveys may not be
representative of the densities that will
be encountered during the proposed
seismic survey.
Potential Number of Exposures to
Sound Levels at or above 160 dB
L-DEO’s ‘‘best estimate’’ of the
potential number of exposures of
cetaceans, absent any mitigation
measures, to seismic sounds with
received levels at or above 160 dB re 1
μPa (rms) is 8,624 (Table 2). It is
assumed that marine mammals exposed
to airgun sounds this strong might
change their behavior sufficiently to be
considered ‘‘taken by harassment’’.
The number of potential exposures to
sound levels at or above 160 dB re 1 μPa
(rms) were calculated by multiplying
the expected average species density
(see section VII of L-DEO’s application)
times the anticipated minimum area
(7302 km2, 4537 mi2) to be ensonified
to that level during airgun operations
including overlap.
The area expected to be ensonified
was determined by entering the planned
survey lines into a MapInfo Geographic
Information System (GIS), using the GIS
to identify the relevant areas by
‘‘drawing’’ the applicable 160–dB buffer
around each seismic line, and then
calculating the total area within the
buffers. Areas where overlap occurred
(because of closely-spaced lines) were
included when estimating the number
of exposures.
Number of Individual Cetaceans
Exposed to Sound Levels at or above
160 dB
L-DEO’s ‘‘best estimate’’ of the
potential number of different
individuals that could be exposed to
airgun sounds with received levels at or
above 160 dB re 1 μPa (rms) on one or
more occasions is 1,748. That total
includes 22 baleen whales, 17 of which
are considered endangered under the
ESA: six humpback whales, two blue
whales, one sei whale, and eight fin
whales, which would represent small
numbers of the regional populations
(Table 2). Ten sperm whales and 19
beaked whales could be exposed during
the survey as well (Table 2).
Based on numbers of animals
encountered during previous L-DEO
seismic surveys, the likelihood of the
successful implementation of the
required mitigation measures, and the
likelihood that some animals will avoid
the area around the operating airguns,
NMFS believes that L-DEO’s airgun
seismic testing program may result in
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the Level B harassment of some lower
number of individual marine mammals
(a few times each) than is indicated by
the column titled, Number of
Individuals Exposed to ≥160 dB
(Request) in Table 2. L-DEO has asked
for authorization for take of their best
estimate of numbers for each species.
Though NMFS believes that take of the
requested numbers is unlikely, we still
find these numbers small relative to the
population sizes.
hsrobinson on PROD1PC76 with NOTICES
Potential Effects on Habitat
The proposed seismic survey will not
result in any permanent impact on
habitats used by marine mammals, or to
the food sources they use. The main
impact issue associated with the
proposed activity will be temporarily
elevated noise levels and the associated
direct effects on marine mammals.
The Langseth will deploy 16 OBS in
the vent field grid (see Figure 1 of LDEO’s application), and will deploy
another 48 OBS throughout the
remaining study area in the Endeavour
MPA. L-DEO proposes to use two
different types of OBS: (1) the WHOI
‘‘D2’’ OBS, which has an anchor made
of hot-rolled steel with dimensions 2.5
x 30.5 x 38.1 cm; and (2) the LC4x4,
which consists of a an anchor with a 1
m2 piece of steel grating. These OBS
anchors will remain upon equipment
recovery.
Although OBS placement may disrupt
a very small area of seafloor habitat and
may disturb benthic invertebrates, the
impacts are expected to be localized and
transitory. The vessel will deploy the
OBS in such a way that creates the least
disturbance to the area. The vent area is
dynamic, and the natural variability
within the system is high; toppling and
regrowth of sulphide structures, and
death of assemblages are common
(Tunnicliffe and Thomson, 1999). Thus,
it is not expected that the placement of
OBS would have adverse effects beyond
naturally occurring changes in this
environment, and any effects of the
planned activity on marine mammal
habitats and food resources are expected
to be negligible.
Potential Effects on Fish
Existing information on the impacts of
seismic surveys on marine fish and
invertebrate populations is very limited
(See Appendix D of L-DEO’s EA) and
the vast majority of the data are in the
form of reports and other documents
that have not been peer reviewed
(Popper and Hastings, 2009).
There are three types of potential
effects of exposure to seismic surveys:
(1) pathological, (2) physiological, and
(3) behavioral.
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Pathological Effects - Pathological
effects involve lethal and temporary or
permanent sub-lethal injury. The
potential for pathological damage to
hearing structures in fish depends on
the energy level of the received sound
and the physiology and hearing
capability of the species in question (see
Appendix D of L-DEO’s EA). For a given
sound to result in hearing loss, the
sound must exceed, by some substantial
amount, the hearing threshold of the
fish for that sound (Popper, 2005). The
consequences of temporary or
permanent hearing loss in individual
fish on a fish population are unknown;
however, they likely depend on the
number of individuals affected and
whether critical behaviors involving
sound (e.g. predator avoidance, prey
capture, orientation and navigation,
reproduction, etc.) are adversely
affected.
Little is known about the mechanisms
and characteristics of damage to fish
that may be inflicted by exposure to
seismic survey sounds. Few data have
been presented in the peer-reviewed
scientific literature. McCauley et al.
(2003), found that exposure to airgun
sound caused observable anatomical
damage to the auditory maculae of
‘‘pink snapper’’ (Pagrusauratus). This
damage in the ears had not been
repaired in fish sacrificed and examined
almost two months after exposure. O n
the other hand, Popper et al. (2005)
documented only TTS (as determined
by auditory brainstem response) in two
of three fish species from the Mackenzie
River Delta. This study found that broad
whitefish (Coreogonus nasus) that
received a sound exposure level of 177
dB re 1 μPa2•s showed no hearing loss.
During both studies, the repetitive
exposure to sound was greater than
would have occurred during a typical
seismic survey. However, the
substantial low-frequency energy
produced by the airguns [less than
approximately 400 Hz in the study by
McCauley et al. (2003) and less than
approximately 200 Hz in Popper et al.
(2005)] likely did not propagate to the
fish because the water in the study areas
was very shallow (approximately 9 m
(29.5 ft) in the former case and less than
2 m (6.5 ft) in the latter). Water depth
sets a lower limit on the lowest sound
frequency that will propagate (the
‘‘cutoff frequency’’) at about one-quarter
wavelength (Urick, 1983; Rogers and
Cox, 1988).
According to Buchanan et al. (2004),
for the types of seismic airguns and
arrays involved with the proposed
program, the pathological (mortality)
zone for fish would be expected to be
within a few meters of the seismic
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source. Numerous other studies provide
examples of no fish mortality upon
exposure to seismic sources (Falk and
Lawrence, 1973; Holliday et al., 1987;
La Bella et al., 1996; Santulli et al.,
1999; McCauley et al., 2000a,b, 2003;
Bjarti, 2002; Hassel et al. 2003; Popper
et al., 2005).
Physiological Effects – Physiological
effects involve temporary and
permanent primary and secondary stress
responses. Cellular and/or biochemical
responses of fish to acoustic stress such
as changes in levels of enzymes and
proteins could potentially affect fish
populations by increasing mortality or
reducing reproductive success. Primary
and secondary stress responses of fish
after exposure to seismic survey sound
appear to be temporary in all studies
done to date (Sverdrup et al., 1994;
McCauley et al., 2000a,b). The periods
necessary for the biochemical changes
to return to normal are variable, and
depend on numerous aspects of the
biology of the species and of the sound
stimulus (see Appendix D of L-DEO’s
EA).
Behavioral Effects – Behavioral effects
include changes in the distribution,
migration, mating, and catchability of
fish populations. Studies investigating
the possible effects of sound (including
seismic survey sound) on fish behavior
have been conducted on both uncaged
and caged individuals (Chapman and
Hawkins, 1969; Pearson et al., 1992;
Santulli et al., 1999; Wardle et al., 2001;
Hassel et al., 2003). Typically, in these
studies fish exhibited a sharp ‘‘startle’’
response at the onset of a sound
followed by habituation and a return to
normal behavior after the sound ceased.
There is general concern about
potential adverse effects of seismic
operations on fisheries, namely a
potential reduction in the ‘‘catchability’’
of fish involved in fisheries. Although
reduced catch rates have been observed
in some marine fisheries during seismic
testing, in a number of cases the
findings are confounded by other
sources of disturbance (Dalen and
Raknes, 1985; Dalen and Knutsen, 1986;
Lokkeborg, 1991; Skalski et al., 1992;
Engas et al., 1996). In other airgun
experiments, there was no change in
catch per unit effort (CPUE) of fish
when airgun pulses were emitted,
particularly in the immediate vicinity of
the seismic survey (Pickett et al., 1994;
La Bella et al., 1996). For some species,
reductions in catch may have resulted
from a change in behavior of the fish,
e.g., a change in vertical or horizontal
distribution, as reported in Slotte et al.
(2004).
In general, any adverse effects on fish
behavior or fisheries attributable to
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Federal Register / Vol. 74, No. 88 / Friday, May 8, 2009 / Notices
hsrobinson on PROD1PC76 with NOTICES
seismic testing may depend on the
species in question and the nature of the
fishery (season, duration, fishing
method). They may also depend on the
age of the fish, its motivational state, its
size, and numerous other factors that are
difficult, if not impossible, to quantify at
this point, given such limited data on
effects of airguns on fish, particularly
under realistic at-sea conditions.
Potential Impacts on Invertebrates
The existing body of information on
the impacts of seismic survey sound on
marine invertebrates is very limited.
However, there is some unpublished
and very limited evidence of the
potential for adverse effects on
invertebrates, thereby justifying further
discussion and analysis of this issue.
The three types of potential effects of
exposure to seismic surveys on marine
invertebrates are pathological,
physiological, and behavioral. Based on
the physical structure of their sensory
organs, marine invertebrates appear to
be specialized to respond to particle
displacement components of an
impinging sound field and not to the
pressure component (Popper et al.,
2001; see also Appendix E of L-DEO’s
EA).
Pathological Effects – For the type of
airgun array planned for the proposed
program, the pathological (mortality)
zone for crustaceans and cephalopods is
expected to be within a few meters of
the seismic source; however, very few
specific data are available on levels of
seismic signals that might damage these
animals. This premise is based on the
peak pressure and rise/decay time
characteristics of seismic airgun arrays
currently in use around the world. Some
studies have suggested that seismic
survey sound has a limited pathological
impact on early developmental stages of
crustaceans (Pearson et al., 1994;
Christian et al., 2003; DFO, 2004).
However, the impacts appear to be
either temporary or insignificant
compared to what occurs under natural
conditions. Controlled field experiments
on adult crustaceans (Christian et al.,
2003, 2004; DFO, 2004) and adult
cephalopods (McCauley et al., 2000a,b)
exposed to seismic survey sound have
not resulted in any significant
pathological impacts on the animals. It
has been suggested that exposure to
commercial seismic survey activities
has injured giant squid (Guerra et al.,
2004), but there is no evidence to
support such claims.
Benthic invertebrates in the Endeavor
MPA are not expected to be affected by
seismic operations, as sound levels from
the airguns will diminish dramatically
by the time the sound reaches the ocean
VerDate Nov<24>2008
17:51 May 07, 2009
Jkt 217001
floor at a depth of approximately 2250
m (7382 ft).
Negligible Impact Determination
NMFS has preliminarily determined,
provided that the aforementioned
mitigation and monitoring measures are
implemented, that the impact of
conducting a seismic program in the
northeast Pacific Ocean may result, at
worst, in a temporary modification in
behavior and/or low-level physiological
effects (Level B Harassment) of small
numbers of certain species of marine
mammals. While behavioral and
avoidance reactions may be made by
these species in response to the
resultant noise from the airguns, these
behavioral changes are expected to have
a negligible impact on the affected
species and stocks of marine mammals.
While the number of potential
incidental harassment takes will depend
on the distribution and abundance of
marine mammals in the area of seismic
operations, the number of potential
harassment takings is estimated to be
relatively small in light of the
population size (see Table 2). NMFS
anticipates the actual take of individuals
to be lower than the numbers depicted
in the table, because those numbers do
not reflect either the implementation of
the mitigation numbers or the fact that
some animals will avoid the sound at
levels lower than those expected to
result in harassment. Additionally,
mitigation measures require that the
Langseth avoid any areas where marine
mammals are concentrated.
In addition, no take by death and/or
serious injury is anticipated, and the
potential for temporary or permanent
hearing impairment will be avoided
through the incorporation of the
required mitigation measures described
in this document. This conclusion is
supported by: (1) the likelihood that,
given sufficient notice through slow
ship speed and ramp-up of the seismic
array, marine mammals are expected to
move away from a noise source that it
is annoying prior to its becoming
potentially injurious; (2) TTS is unlikely
to occur, especially in odontocetes, until
levels above 180 dB re 1 μPa (rms) are
reached; (3) the fact that injurious levels
of sound are only likely very close to the
vessel; and (4) the monitoring program
developed to avoid injury will be
sufficient to detect (using visual
detection and PAM), with reasonable
certainty, all marine mammals within or
entering the identified safety zones.
Endangered Species Act (ESA)
Under section 7 of the ESA, the
National Science Foundation (NSF) has
begun consultation on this proposed
PO 00000
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Fmt 4703
Sfmt 4703
21647
seismic survey. NMFS will also consult
internally on the issuance of an IHA
under section 101(a)(5)(D) of the MMPA
for this activity. Consultation will be
concluded prior to a determination on
the issuance of an IHA.
National Environmental Policy Act
(NEPA)
On September 22, 2005 (70 FR 55630),
NSF published a notice of intent to
prepare a Programmatic Environmental
Impact Statement/Overseas
Environmental Impact Statement (EIS/
OES) to evaluate the potential
environmental impacts associated with
the use of seismic sources in support of
NSF-funded research by U.S. academic
scientists. NMFS agreed to be a
cooperating agency in the preparation of
the EIS/OEIS. This EIS/OEIS has not
been completed. Therefore, in order to
meet NSF’s and NMFS’ NEPA
requirements for the proposed activity
and issuance of an IHA to L-DEO, the
NSF has prepared an Environmental
Assessment of a Marine Geophysical
Survey by the Langseth in the northeast
Pacific Ocean in the Endeavor MPA.
NMFS is reviEwing that document and
will either adopt NSF’s EA or conduct
a separate NEPA analysis, as necessary,
prior to making a determination of the
issuance of the IHA. NMFS has posted
NSF’s EA on its website at https://
www.nmfs.noaa.gov/pr/permits/
incidental.htm#applications.
Preliminary Conclusions
Based on the preceding information,
and provided that the proposed
mitigation and monitoring are
incorporated, NMFS has preliminarily
concluded that the proposed activity
will incidentally take, by level B
behavioral harassment only, small
numbers of marine mammals. There is
no subsistence harvest of marine
mammals in the proposed research area;
therefore, there will be no impact of the
activity on the availability of the species
or stocks of marine mammals for
subsistence uses. No take by Level A
harassment (injury) or death is
anticipated and harassment takes
should be at the lowest level practicable
due to incorporation of the mitigation
measures proposed in this document.
Proposed Authorization
NMFS proposes to issue an IHA to LDEO for a marine seismic survey in the
northeast Pacific Ocean during August October 2009, provided the previously
mentioned mitigation, monitoring, and
reporting requirements are incorporated.
E:\FR\FM\08MYN1.SGM
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21648
Federal Register / Vol. 74, No. 88 / Friday, May 8, 2009 / Notices
Dated: May 4, 2009.
Helen M. Golde,
Deputy Director, Office of Protected
Resources, National Marine Fisheries Service.
[FR Doc. E9–10821 Filed 5–7–09; 8:45 am]
DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric
Administration
RIN 0648–XO84
BILLING CODE 3510–22–S
Small Takes of Marine Mammals
Incidental to Specified Activities;
Taking Marine Mammals Incidental to
Construction and Operation of a
Liquefied Natural Gas Facility off
Massachusetts
DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric
Administration
RIN 0648–XO92
Notice of Availability of the Marine
Mammal Health and Stranding
Response Program Record of Decision
AGENCY: National Marine Fisheries
Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA),
Commerce.
ACTION: Notice of Availability (NOA) of
Record of Decision.
SUMMARY: The National Marine
Fisheries Service (NMFS) announces the
availability of the Record of Decision
(ROD) for the Marine Mammal Health
and Stranding Response Program
(MMHSRP). This ROD announces
NMFS’ decisions for implementing the
MMHSRP. Pursuant to the National
Environmental Policy Act (NEPA) and
implementing regulations, NMFS
prepared a Programmatic Environmental
Impact Statement (PEIS) that evaluated
the potential environmental and
socioeconomic effects associated with
alternatives for the MMHSRP’s
activities.
Comments or questions
regarding the ROD can be sent to David
Cottingham, Chief, Marine Mammal and
Sea Turtle Division, Office of Protected
Resources, National Marine Fisheries
Service, 1315 East-West Highway, Room
13635, Silver Spring, MD 20910.
ADDRESSES:
FOR FURTHER INFORMATION CONTACT:
Sarah Howlett, Fishery Biologist, NMFS,
at (301) 713–2322; facsimile at (301)
427–2522.
A copy of
the ROD and the Final PEIS are
available at: https://www.nmfs.noaa.gov/
pr/health/eis.htm.
hsrobinson on PROD1PC76 with NOTICES
SUPPLEMENTARY INFORMATION:
Dated: May 1, 2009.
Katy M. Vincent,
Acting Deputy Director, Office of Protected
Resources, National Marine Fisheries Service.
[FR Doc. E9–10676 Filed 5–7–09; 8:45 am]
BILLING CODE S
VerDate Nov<24>2008
19:00 May 07, 2009
Jkt 217001
AGENCY: National Marine Fisheries
Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA),
Commerce.
ACTION: Notice; proposed incidental
harassment authorization; request for
comments and information.
NMFS received an
application from Neptune LNG, L.L.C.
(Neptune) for take of marine mammals,
by Level B harassment, incidental to
construction and operation of an
offshore liquefied natural gas (LNG)
facility in Massachusetts Bay. Under the
Marine Mammal Protection Act
(MMPA), NMFS is requesting comments
on its proposal to issue an incidental
harassment authorization (IHA) to
Neptune to incidentally take, by
harassment, small numbers of several
species of marine mammals during
construction and operations of the LNG
facility for a period of 1 year.
DATES: Comments and information must
be received no later than June 8, 2009.
ADDRESSES: Written comments on the
application should be addressed to: P.
Michael Payne, Chief, Permits,
Conservation, and Education Division,
Office of Protected Resources, National
Marine Fisheries Service, 1315 EastWest Highway, Silver Spring, MD
20910–3225. The mailbox address for
providing email comments is PR1.0648–
XO84@noaa.gov. Comments sent via
email, including all attachments, must
not exceed a 10–megabyte file size. A
copy of the application containing a list
of references used in this document may
be obtained by writing to this address,
by telephoning the contact listed below
(see FOR FURTHER INFORMATION CONTACT)
or online at: https://www.nmfs.noaa.gov/
pr/permits/incidental.htm#applications.
Documents cited in this notice may be
viewed, by appointment, during regular
business hours, at the aforementioned
address.
Instructions: All comments received
are a part of the public record and will
generally be posted to https://
www.nmfs.noaa.gov/pr/permits/
incidental.htm#applications without
change. All Personal Identifying
SUMMARY:
PO 00000
Frm 00030
Fmt 4703
Sfmt 4703
Information (for example, name,
address, etc.) voluntarily submitted by
the commenter may be publicly
accessible. Do not submit Confidential
Business Information or otherwise
sensitive or protected information.
The Maritime Administration
(MARAD) and U.S. Coast Guard (USCG)
Final Environmental Impact Statement
(Final EIS) on the Neptune LNG
Deepwater Port License Application is
available for viewing at https://
www.regulations.gov by entering the
search words ‘‘Neptune LNG.’’
FOR FURTHER INFORMATION CONTACT:
Candace Nachman, Office of Protected
Resources, NMFS, (301) 713–2289 ext.
156.
SUPPLEMENTARY INFORMATION:
Background
Sections 101(a)(5)(A) and (D) of the
MMPA (16 U.S.C. 1361 et seq.) direct
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 if certain findings
are made and either regulations are
issued or, if the taking is limited to
harassment, notice of a proposed
authorization is provided to the public
for review.
Authorization for incidental takings
may be granted if NMFS finds that the
taking will have a negligible impact on
the species or stock(s), will not have an
unmitigable adverse impact on the
availability of the species or stock(s) for
subsistence uses, and if the permissible
methods of taking and requirements
pertaining to the mitigation, monitoring
and reporting of such taking 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.
Section 101(a)(5)(D) of the MMPA
establishes an expedited process by
which citizens of the U.S. can apply for
an authorization to incidentally take
small numbers of marine mammals by
harassment. Except for certain
categories of 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,
E:\FR\FM\08MYN1.SGM
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]]>Agencies
[Federal Register Volume 74, Number 88 (Friday, May 8, 2009)]
[Notices]
[Pages 21631-21648]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E9-10821]
-----------------------------------------------------------------------
DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
RIN 0648-XI63
Incidental Takes of Marine Mammals During Specified Activities;
Marine Geophysical Survey in the Northeast Pacific Ocean, August -
October 2009
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice; proposed incidental take authorization; request for
comments.
-----------------------------------------------------------------------
SUMMARY: NMFS has received an application from the Lamont-Doherty
Earth Observatory (L-DEO), a part of Columbia University, for an
Incidental Harassment Authorization (IHA) to take small numbers of
marine mammals, by harassment, incidental to conducting a seismic
survey in the northeast Pacific Ocean. Pursuant to the Marine Mammal
Protection Act (MMPA), NMFS requests comments on its proposal to
authorize L-DEO to take, by Level B harassment only, small numbers of
marine mammals incidental to conducting a marine seismic survey during
August through October, 2009.
DATES: Comments and information must be received no later than June 8,
2009.
ADDRESSES: Comments on the application should be addressed to Michael
Payne, Chief, Permits, Conservation and Education Division, Office of
Protected Resources, National Marine Fisheries Service, 1315 East-West
Highway, Silver Spring, MD 20910-3225. The mailbox address for
providing email comments is PR1.0648-XI63@noaa.gov. Comments sent via
e-mail, including all attachments, must not exceed a 10-megabyte file
size.
All comments received are a part of the public record and will
generally be posted to https://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications without change. All Personal Identifying
Information (for example, name, address, etc.) voluntarily submitted by
the commenter may be publicly accessible. Do not submit confidential
business information or otherwise sensitive or protected information.
A copy of the application containing a list of the references used
in this document may be obtained by writing to the address specified
above, telephoning the contact listed below (see FOR FURTHER
INFORMATION CONTACT), or visiting the internet at: https://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications.
Documents cited in this notice may be viewed, by appointment,
during regular business hours, at the aforementioned address.
FOR FURTHER INFORMATION CONTACT: Jeannine Cody or Howard Goldstein,
Office of Protected Resources, NMFS, (301) 713-2289.
SUPPLEMENTARY INFORMATION:
Background
Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.)
direct the Secretary of Commerce (Secretary) to allow, upon request,
the incidental, but not intentional, taking of marine mammals by United
States citizens who engage in a specified activity (other than
commercial fishing) within a specified geographical region if certain
findings are made and either regulations are issued or, if the taking
is limited to harassment, a notice of a proposed authorization is
provided to the public for review.
Authorization for incidental taking shall be granted if NMFS finds
that the taking will have a negligible impact on the species or
stock(s), will not have an unmitigable adverse impact on the
availability of the species or stock(s) for subsistence uses, 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.''
Section 101(a)(5)(D) of the MMPA established an expedited process
by which citizens of the United States can apply for an authorization
to incidentally take small numbers of marine mammals by harassment.
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 [ALevel A harassment@]; or (ii) has the potential to disturb a
marine mammal or marine mammal stock in the wild by causing
[[Page 21632]]
disruption of behavioral patterns, including, but not limited to,
migration, breathing, nursing, breeding, feeding, or sheltering
[ALevel B harassment@].
Section 101(a)(5)(D) establishes a 45-day time limit for NMFS=
review of an application followed by a 30-day public notice and comment
period on any proposed authorizations for the incidental harassment of
small numbers of marine mammals. Not later than 45 days after the close
of the public comment period, if the Secretary makes the findings set
forth in Section 101(a)(5)(D)(i), the Secretary shall issue or deny
issuance of the authorization with appropriate conditions to meet the
requirements of clause 101(a)(5)(D)(ii).
Summary of Request
On February 11, 2009, NMFS received an application from L-DEO for
the taking by Level B harassment only, of small numbers of 33 species
of marine mammals incidental to conducting a marine seismic survey
within the Exclusive Economic Zone (EEZ) of Canada in the northeast
Pacific Ocean during August through October 2009. L-DEO, with research
funding from the NSF, is conducting the geophysical data acquisition
activities with onboard assistance by Drs. Toomey and Hooft from the
University of Oregon, and Dr. Wilcock from the University of
Washington.
This survey, also known as the Endeavor Tomography (ETOMO) Study,
will take place approximately 250 kilometers (km) (155 miles (mi))
southwest of Vancouver Island, British Columbia, within the Canadian
Endeavour Marine Protected Area (MPA) along an 80-km- (50- mi-) long
section of the Endeavour segment of the Juan de Fuca Ridge. The
Endeavor MPA is a unique ecosystem consisting of hydrothermal vents and
associated fauna. Canada officially designated the area as an MPA in
March 2003. However, scientific research for the conservation,
protection and understanding of the area is permissible under the
Canadian Oceans Act of 1996. Regulations regarding this MPA can be
found on the Department of Justice Canada website at: https://laws.justice.gc.ca/en/ShowFullDoc/cr/SOR-2003-87///en.
The survey will obtain information on the sub-seafloor structure of
volcanic and hydrothermal features that form as a result of movements
of the Earth's plates; will obtain information on the three-dimensional
(3-D) seismic structure of the crust and top-most mantle along an the
Endeavour segment; and will define the distribution of magma beneath
active volcanoes. Past studies using manned submersibles and remotely
piloted vehicles have mapped the locations and characteristics of vent
fields along this ridge segment. The ETOMO Study will extend that
mapping beneath the seafloor and allow researchers to understand the
dynamics of these systems.
Description of the Specified Activity
The planned survey will involve one source vessel, the R/V Marcus
G.Langseth (Langseth), a seismic research vessel owned by the NSF and
operated by L-DEO. The proposed project is scheduled to commence on
August 17, 2009, and scheduled to end on October 13, 2009. The vessel
will depart Astoria, Oregon on August 17, 2009 for transit to the
Endeavor MPA, between 47-48[deg] N. and 128-130[deg] W.
To obtain high-resolution, 3-D structures of the area's magmatic
systems and thermal structures, the Langseth will deploy a towed array
of 36 airguns. The Langseth will also deploy 64 Ocean Bottom
Seismometers (OBS). As the airgun array is towed along the survey
lines, the OBSs will receive the returning acoustic signals and record
them internally for later analysis. For the ETOMO study, the Langseth
will not use a hydrophone streamer to receive geophysical data from the
airgun array.
The ETOMO study (e.g., equipment testing, startup, line changes,
repeat coverage of any areas, and equipment recovery) will take place
in deep (between 1200 and 3000 m, 3,280 feet (ft) and 1.8 mi) water and
will require approximately 10 days to complete 12 transects of variable
lengths totaling 1800 km of survey lines. Data acquisition will include
approximately 240 hours of airgun operation. Please see L-DEO's
application for more detailed information. The exact dates of the
activities will depend on logistics, weather conditions, and the need
to repeat some lines if data quality is substandard.
Vessel Specifications
The Langseth is a seismic research vessel with a propulsion system
designed to be as quiet as possible to avoid interference with the
seismic signals. The vessel, which has a length of 71.5 m (235 feet
(ft); a beam of 17.0 m (56 ft); a maximum draft of 5.9 m (19 ft); and a
gross tonnage of 2925, can accommodate up to 55 people. The ship is
powered by two Bergen BRG-6 diesel engines, each producing 3550
horsepower (hp), which drive the two propellers directly. Each
propeller has four blades, and the shaft typically rotates at 750
revolutions per minute. The vessel also has an 800 hp bowthruster,
which is not used during seismic acquisition. The operation speed
during seismic acquisition is typically 7.4B9.3 km/hour (h) (4-5
knots). When not towing seismic survey gear, the Langseth can cruise at
20B24 km/h (11-13 knots). The Langseth has a range of 25,000 km (13,499
nautical miles). The Langseth will also serve as the platform from
which vessel-based marine mammal (and sea turtle) observers will watch
for animals before and during airgun operations.
Acoustic Source Specifications
Seismic Airguns
The full airgun array for the survey consists of 36 airguns (a
mixture of Bolt 1500LL and Bolt 1900LLX airguns ranging in size from 40
to 360 cubic inches (in\3\)), with a total volume of approximately
6,600 in\3\ and a firing pressure of 1900 pounds per square inch (psi).
The dominant frequency components range from two to 188 Hertz (Hz).
The array configuration consists of four identical linear arrays or
strings, with 10 airguns on each string; the first and last airguns
will be spaced 16 m (52 ft) apart. For each operating string, nine
airguns will be fired simultaneously, whereas the tenth is kept in
reserve as a spare, to be turned on in case of failure of another
airgun. The four airgun strings will be distributed across an
approximate area of 24H16 m (79 x 52 ft) behind the Langseth and will
be towed approximately 50 to 100 m (164-328 ft) behind the vessel at a
tow-depth of 15 m (49.2 ft). The airgun array will fire every 250 m
(105 seconds (s)) or 500 m (210 s) depending on which grid or line the
Langseth surveys. During firing, a brief (approximately 0.1 s) pulse of
sound is emitted. The airguns will be silent during the intervening
periods.
Multibeam Echosounder
The Langseth will operate a Simrad EM120 multibeam echosounder
(MBES) simultaneously during airgun operations to map characteristics
of the ocean floor. The hull-mounted MBES emits brief pulses of mid- or
high-frequency (11.25-12.6 kHz) sound in a fanshaped beam that extends
downward and to the sides of the ship. The beamwidth is 1 degree
([deg]) fore-aft and 150[deg] athwartship. The maximum source level is
242 dB re 1 microPa m (root mean square (rms)). For deep-water
operation, each Aping@ consists of nine successive fan-shaped
transmissions, each 15 millisecond (ms) in duration and each
ensonifying a sector that extends 1[deg] foreBaft. The nine successive
[[Page 21633]]
transmissions span an overall cross-track angular extent of about
150[deg], with 16 ms gaps between the pulses for successive sectors. A
receiver in the overlap area between two sectors would receive two 15-
ms pulses separated by a 16-ms gap. In shallower water, the pulse
duration is reduced to 5 or 2 ms, and the number of transmit beams is
also reduced. The ping interval varies with water depth, from
approximately 5 s at 1000 m (3,281 ft) to 20 s at 4000 m (13,124 ft).
Sub-bottom Profiler
The Langseth will operate a sub-bottom profiler (SBP) continuously
throughout the cruise with the MBES. An SBP operates at mid- to high
frequencies and is generally used simultaneously with an MBES to
provide information about the sedimentary features and bottom
topography. SBP pulses are directed downward at typical frequencies of
approximately 3 18 kHz. However, the dominant frequency component of
the SBP is 3.5 kHz which is directed downward in a narrow beam by a
hull-mounted transducer on the vessel. The SBP output varies with water
depth from 50 watts in shallow water to 800 watts in deep water and has
a normal source output (downward) of 200 dB re 1 microPa m and a
maximum source level output (downward) of 204 dB re 1 microPa m.
The SBP used aboard the Langseth uses seven beams simultaneously,
with a beam spacing of up to 15[deg] and a fan width up to 30[deg].
Pulse duration is 0.4 100 ms at intervals of 1 s; a common mode of
operation is to broadcast five pulses at 1-s intervals followed by a 5-
s pause.
Characteristics of Airgun Pulses
Discussion of the characteristics of airgun pulses has been
provided in Appendix B of L-DEO=s application and in previous Federal
Register notices (see 69 FR 31792, June 7, 2004; 71 FR 58790, October
5, 2006; 72 FR 71625, December 18, 2007; 73 FR 52950, September 12,
2008, or 73 FR 71606, November 25, 2008). Reviewers are referred to
those documents for additional information.
Safety Radii
Safety zones are areas defined by the radius of received sound
levels believed to have the potential for at least temporary hearing
impairment (HESS, 1999). The distance from the sound source at which an
animal would be exposed to these different received sound levels may be
estimated and is typically referred to as safety radii. These safety
radii are specifically used to help NMFS estimate the number of marine
mammals likely to be harassed by the proposed activity and in deciding
how close a marine mammal may approach an operating sound source before
the applicant will be required to power-down or shut down the sound
source.
During this study, all survey efforts will take place in deep
(greater than 1000 m, 3820 ft) water. L-DEO has summarized the modeled
safety radii for the planned airgun configuration in Table 1 which
shows the predicted distances at which sound levels (190 decibels (dB),
180 dB, and 160 dB) are expected to be received from the 36-airgun
array and a single airgun operating in water greater than 1000 m (3,820
ft) in depth.
Table 1. Predicted distances to which sound levels [gteqt]190, 180, and 160 dB re 1 microPa might be received in
deep (>1000 m; 3280 ft) water from the 36-airgun array during the seismic survey, August September, 2009 (based
on L-DEO modeling).
----------------------------------------------------------------------------------------------------------------
Predicted RMS Distances (m)
Source and Volume Tow Depth (m) -----------------------------------------
190 dB 180 dB 160 dB
----------------------------------------------------------------------------------------------------------------
Single Bolt airgun 40 in\3\ 6-15\*\ 12 40 385
4 strings 36 airguns 6600 in\3\ 6 220 710 4670
9 300 950 6000
12 340 1120 6850
15 380 1220 7690
----------------------------------------------------------------------------------------------------------------
\*\The tow depth has minimal effect on the maximum near-field output and the shape of the frequency spectrum for
the single 40 in\3\ airgun; thus the predicted safety radii are essentially the same at each tow depth.
The L-DEO model applied to airgun configuration does not allow for
bottom interactions, and thus is most directly applicable to deep water
and to relatively short ranges. The calculated distances are expected
to overestimate the actual distances to the corresponding Sound
Pressure Levels (SPL), given the deep-water results of Tolstoy et al.
(2004a,b). Additional information regarding how the safety radii were
calculated and how the empirical measurements were used to correct the
modeled numbers may be found in Appendix A of L-DEO=s Environmental
Assessment (EA). The conclusion that the model predictions in Table 1
are precautionary, relative to actual 180- and 190-dB (rms) radii, is
based on empirical data from the acoustic calibration of different
airgun configurations used by the R/V Maurice Ewing (Ewing) in the
northern Gulf of Mexico. (Tolstoy et al., 2004a,b).
L-DEO conducted a more extensive acoustic calibration study of the
Langseth=s 36-airgun array in late 2007/early 2008 in the northern Gulf
of Mexico (LGL Ltd., 2006; Holst and Beland, 2008). L-DEO is currently
modeling the distances to the corresponding Sound Pressure Levels (SPL)
(e.g., 190, 180, and 160 dB re 1 microPa (rms)) for various airgun
configurations and water depths. Those results are not yet available.
However, the empirical data from the 2007/2008 calibration study will
be used to refine the exclusion zones proposed above for use during
survey, if the data are appropriate and available at the time of the
survey.
Description of Marine Mammals in the Activity Area
Thirty-three marine mammal species may occur off the coast of
British Columbia, Canada, including 20 odontocetes (toothed cetaceans),
7 mysticetes (baleen whales), 5 pinnipeds, and the sea otter (Enhydra
sp.). In the United States, sea otters are managed by the U.S. Fish and
Wildlife Service (USFWS) and are unlikely to be encountered in or near
the Endeavor Marine Protected Area where seismic operations will occur,
and are, therefore, not addressed further in this document. Eight of
these species are listed as endangered under the U.S. Endangered
Species Act of 1973 (ESA), including the Steller sea lion (Eumetopias
jubatus), the humpback (Megaptera
[[Page 21634]]
novaeanliae), sei (Balaenoptera borealis), fin (Balenoptera physalus),
blue (Balenoptera musculus), North Pacific right (Eubalena japonica),
sperm (Physeter macrocephalus), and Southern Resident killer (Orcinus
orca) whales.
This proposed IHA will only address requested take authorizations
for cetaceans and pinnipeds. Table 2 below outlines the species, their
habitat and abundance in the proposed survey area, the estimated number
of exposures (based on average density) to sound levels greater than or
equal to 160 dB during the seismic survey if no animals moved away from
the survey vessel.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Estimated Number
Estimated Number of Individuals Approx. Percent
Species Habitat Abundance in the NE Occurrence in the of Exposures to Exposed to Sound of Regional
Pacific Survey Area Sound Levels Levels Population
[gteqt] 160 dB [gteqt]160 dB
--------------------------------------------------------------------------------------------------------------------------------------------------------
North Pacific right whale* Coastal and shelf waters 100-200 Rare and unlikely 0 0 0
--------------------------------------------------------------------------------------------------------------------------------------------------------
Humpback whale* Coastal waters >6000 Uncommon 29 6 0.10
--------------------------------------------------------------------------------------------------------------------------------------------------------
Minke whale Coastal and shelf waters 9000 Uncommon 26 26 0.06
--------------------------------------------------------------------------------------------------------------------------------------------------------
Sei whale Pelagic 7260 - 12,620 Uncommon 5 1 0.01
--------------------------------------------------------------------------------------------------------------------------------------------------------
Fin whale* Pelagic, shelf and 13,620-18,680 Uncommon 39 8 0.05
coastal waters
--------------------------------------------------------------------------------------------------------------------------------------------------------
Blue whale* Pelagic, shelf and 1186 Uncommon 8 2 0.14
inshore waters
--------------------------------------------------------------------------------------------------------------------------------------------------------
Sperm whale* Pelagic 24,000 Uncommon 52 10 0.04
--------------------------------------------------------------------------------------------------------------------------------------------------------
Pygmy sperm whale Deep waters off the Not available Common 47 9 Not available
shelf
--------------------------------------------------------------------------------------------------------------------------------------------------------
Dwarf Sperm whale Deep waters off the Not available Uncommon 0 0 0.0
shelf
--------------------------------------------------------------------------------------------------------------------------------------------------------
Baird's beaked whale Deep waters and cont. 6000 Common 62 13 0.21
slopes
--------------------------------------------------------------------------------------------------------------------------------------------------------
Blainville's beaked whale Deep waters and cont. 603 Uncommon 8 2 0.28
slopes
--------------------------------------------------------------------------------------------------------------------------------------------------------
Cuvier's beaked whale Pelagic 20,000 Uncommon 0 0 0.0
--------------------------------------------------------------------------------------------------------------------------------------------------------
Hubb's beaked whale Deep waters and cont. 421 Uncommon 8 2 0.40
slopes
--------------------------------------------------------------------------------------------------------------------------------------------------------
Stejneger's beaked whale Deep waters 421 Uncommon 8 2 0.40
--------------------------------------------------------------------------------------------------------------------------------------------------------
Bottlenose dolphin Coastal and offshore 3257 Rare 0 0 0.0
waters
--------------------------------------------------------------------------------------------------------------------------------------------------------
Striped dolphin Pelagic 23,883 rare 2 0 0.0
--------------------------------------------------------------------------------------------------------------------------------------------------------
Short-beaked common dolphin Coastal and offshore 487,622 Common 511 104 0.02
waters
--------------------------------------------------------------------------------------------------------------------------------------------------------
Pacific white-sided dolphin Pelagic, shelf and slope 931,000 Common 895 181 0.02
waters
--------------------------------------------------------------------------------------------------------------------------------------------------------
Northern right-whale dolphin Pelagic, shelf and slope 15,305 Common 699 142 0.93
waters
--------------------------------------------------------------------------------------------------------------------------------------------------------
Risso's dolphin Pelagic 12,093 Common 467 95 0.78
--------------------------------------------------------------------------------------------------------------------------------------------------------
False killer whale Pelagic Not available Rare 0 0 0.0
--------------------------------------------------------------------------------------------------------------------------------------------------------
Killer whale Widely distributed 8500 Uncommon 61 12 0.15
--------------------------------------------------------------------------------------------------------------------------------------------------------
Short-finned pilot whale Pelagic 160,200 Uncommon 0 0 00.0
--------------------------------------------------------------------------------------------------------------------------------------------------------
[[Page 21635]]
Dall's porpoise Offshore and nearshore 57,549 Common 5337 1081 1.88
waters
--------------------------------------------------------------------------------------------------------------------------------------------------------
Northern fur seal Coastal 721,935 Common 360 73 0.01
--------------------------------------------------------------------------------------------------------------------------------------------------------
Total ........................ ................... ................... 8,624 1,748 ................
--------------------------------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------------------------------
Table 2. Abundance, preferred habitat, and commonness of the marine mammal species that may be encountered during the proposed survey within the ETOMO
survey area. The far right columns indicate the estimated number of each species that will be exposed to [gteqt]160 dB based on average density
estimates. NMFS believes that, when mitigation measures are taken into consideration, the activity is likely to result in take of numbers of animals
less than those indicated by the column titled NUmber of Individuals Exposed [gteqt]160 dB.
* Federally listed endangered species.
Detailed information regarding the status and distribution of these
marine mammals may be found in sections III and IV of L-DEO's
application.
Potential Effects of the Proposed Activity on Marine Mammals
Summary of Potential Effects of Airgun Sounds on Marine Mammals
The effects of sounds from airguns might include one or more of the
following: tolerance, masking of natural sounds, behavioral
disturbance, temporary or permanent hearing impairment, or non-auditory
physical or physiological effects (Richardson et al., 1995; Gordon et
al., 2004; Nowacek et al., 2007; Southall et al., 2007). Permanent
hearing impairment, in the unlikely event that it occurred, would
constitute injury, but temporary threshold shift (TTS) is not an injury
(Southall et al., 2007). Although the possibility cannot be entirely
excluded, it is unlikely that the project would result in any cases of
temporary or permanent hearing impairment, or any significant non-
auditory physical or physiological effects. Some behavioral disturbance
is expected, but is expected to be localized and short-term.
Tolerance
Numerous studies have shown that pulsed sounds from airguns are
often readily detectable in the water at distances of many kilometers.
For a brief summary of the characteristics of airgun pulses, see
Appendix B of L-DEO's application. Several studies have also shown that
marine mammals at distances more than a few kilometers from operating
seismic vessels often show no apparent response (tolerance) (see
Appendix B (5) of L-DEO's EA). That is often true even in cases when
the pulsed sounds must be readily audible to the animals based on
measured received levels and the hearing sensitivity of that mammal
group. Although various baleen whales, toothed whales, and (less
frequently) pinnipeds have been shown to react behaviorally to airgun
pulses under some conditions, at other times mammals of all three types
have shown no overt reactions. In general, pinnipeds usually seem to be
more tolerant of exposure to airgun pulses than cetaceans, with the
relative responsiveness of baleen and toothed whales being variable.
Masking
Introduced underwater sound may, through masking, reduce the
effective communication distance of a marine mammal species if the
frequency of the source is close to that used as a signal by the marine
mammal, and if the anthropogenic sound is present for a significant
fraction of the time (Richardson et al., 1995).
Masking effects of pulsed sounds (even from large arrays of
airguns) on marine mammal calls and other natural sounds are expected
to be limited, although there are very few specific data on this.
Because of the intermittent nature and low duty cycle of seismic
pulses, animals can emit and receive sounds in the relatively quiet
intervals between pulses. However, in some situations, multi-path
arrivals and reverberation cause airgun sound to arrive for much or all
of the interval between pulses (e.g., Simard et al., 2005; Clark and
Gagnon, 2006) which could mask calls. Some baleen and toothed whales
are known to continue calling in the presence of seismic pulses, and
their calls can usually be heard between the seismic pulses (e.g.,
Richardson et al., 1986; McDonald et al., 1995; Greene et al., 1999;
Nieukirk et al., 2004; Smultea et al., 2004; Holst et al., 2005a,b,
2006). In the northeast Pacific Ocean, blue whale calls have been
recorded during a seismic survey off Oregon (McDonald et al., 1995).
Among odontocetes, there has been one report that sperm whales ceased
calling when exposed to pulses from a very distant seismic ship (Bowles
et al., 1994). However, more recent studies found that this species
continued calling in the presence of seismic pulses (Madsen et al.,
2002; Tyack et al., 2003; Smultea et al., 2004; Holst et al., 2006;
Jochens et al., 2006, 2008). Dolphins and porpoises commonly are heard
calling while airguns are operating (e.g., Gordon et al., 2004; Smultea
et al., 2004; Holst et al., 2005a,b; Potter et al., 2007). The sounds
important to small odontocetes are predominantly at much higher
frequencies than are the dominant components of airgun sounds, thus
limiting the potential for masking. In general, masking effects of
seismic pulses are expected to be negligible, given the normally
intermittent nature of seismic pulses. Masking effects on marine
mammals are discussed further in Appendix B (4) of L-DEO's EA.
Disturbance Reactions
Disturbance includes a variety of effects, including subtle to
conspicuous changes in behavior, movement, and displacement. Based on
NMFS (2001, p. 9293), NRC (2005), and Southall et al. (2007), L-DEO
assumes that simple exposure to sound, or brief reactions that do not
disrupt behavioral patterns in a potentially significant manner, do not
constitute harassment or ``taking''. By potentially significant, L-DEO
means ``in a manner that might have deleterious effects to the well-
being of individual marine mammals or their populations''.
Reactions to sound, if any, depend on species, state of maturity,
experience, current activity, reproductive state, time of day, and many
other factors (Richardson et al., 1995; Wartzok et al., 2004; Southall
et al., 2007). If a marine mammal does react briefly to an
[[Page 21636]]
underwater sound by changing its behavior or moving a small distance,
the impacts of the change are unlikely to be significant to the
individual, let alone the stock or population. However, if a sound
source displaces marine mammals from an important feeding or breeding
area for a prolonged period, impacts on individuals and populations
could be significant (e.g., Lusseau and Bejder, 2007; Weilgart, 2007).
Given the many uncertainties in predicting the quantity and types of
impacts of noise on marine mammals, it is common practice to estimate
how many mammals would be present within a particular distance of
industrial activities and exposed to a particular level of industrial
sound. In most cases, this approach likely overestimates the numbers of
marine mammals that would be affected in some biologically-important
manner.
The sound criteria used to estimate how many marine mammals might
be disturbed to some biologically-important degree by a seismic program
are based primarily on behavioral observations of a few species.
Detailed studies have been done on humpback, gray (Eshrichtius
robustus), bowhead (Balena mysticetes), and sperm whales, and on ringed
seals (Pusa hispida). Less detailed data are available for some other
species of baleen whales, and small toothed whales, but for many
species there are no data on responses to marine seismic surveys.
Baleen Whales
Baleen whales generally tend to avoid operating airguns, but
avoidance radii are quite variable. Whales are often reported to show
no overt reactions to pulses from large arrays of airguns at distances
beyond a few kilometers, even though the airgun pulses remain well
above ambient noise levels out to much longer distances. However, as
reviewed in Appendix B (5) of L-DEO's EA, baleen whales exposed to
strong noise pulses from airguns often react by deviating from their
normal migration route and/or interrupting their feeding and moving
away. In the cases of migrating gray and bowhead whales, the observed
changes in behavior appeared to be of little or no biological
consequence to the animals. They simply avoided the sound source by
displacing their migration route to varying degrees, but within the
natural boundaries of the migration corridors.
Studies of gray, bowhead, and humpback whales have shown that
seismic pulses with received levels of 160 170 dB re 1 microPa (rms)
seem to cause obvious avoidance behavior in a substantial fraction of
the animals exposed (Richardson et al., 1995). In many areas, seismic
pulses from large arrays of airguns diminish to those levels at
distances ranging from 4-15 km (2.5-9.3 mi) from the source. A
substantial proportion of the baleen whales within those distances may
show avoidance or other strong behavioral reactions to the airgun
array. Subtle behavioral changes sometimes become evident at somewhat
lower received levels, and studies summarized in Appendix B of L-DEO's
EA have shown that some species of baleen whales, notably bowhead and
humpback whales, at times show strong avoidance at received levels
lower than 160 170 dB re 1 microPa (rms).
Responses of humpback whales to seismic surveys have been studied
during migration, on summer feeding grounds, and on Angolan winter
breeding grounds; there has also been discussion of effects on the
Brazilian wintering grounds. McCauley et al. (1998, 2000a) studied the
responses of humpback whales off Western Australia to a full-scale
seismic survey with a 16-airgun, 2678-in\3\ array, and to a single 20-
in\3\ airgun with source level of 227 dB re 1 microPa m (peak to peak).
McCauley et al. (1998) documented that avoidance reactions began at 5-8
km (3-5 mi) from the array, and that those reactions kept most pods
approximately 3-4 km (1.8-2.5 mi) from the operating seismic boat.
McCauley et al. (2000a) noted localized displacement during migration
of 4-5 km (2.5-3.1 mi) by traveling pods and 7-12 km (4.3-7.5 mi) by
more sensitive resting pods of cow-calf pairs. Avoidance distances with
respect to the single airgun were smaller but consistent with the
results from the full array in terms of the received sound levels. The
mean received level for initial avoidance of an approaching airgun was
140 dB re 1 microPa (rms) for humpback pods containing females, and at
the mean closest point of approach distance the received level was 143
dB re 1 microPa (rms). The initial avoidance response generally
occurred at distances of 5-8 km (3.1-4.9 mi) from the airgun array and
2 km (1.2 mi) from the single airgun. However, some individual humpback
whales, especially males, approached within distances of 100-400 m
(328-1312 ft), where the maximum received level was 179 dB re 1 microPa
(rms).
Humpback whales on their summer feeding grounds in southeast Alaska
did not exhibit persistent avoidance when exposed to seismic pulses
from a 1.64-L (100-in\3\) airgun (Malme et al., 1985). Malme et al.
reported that some of the humpbacks seemed startled at received levels
of 150 169 dB re 1 microPa and concluded that there was no clear
evidence of avoidance, despite the possibility of subtle effects, at
received levels up to 172 re 1 FPa on an approximate rms basis.
It has been suggested that South Atlantic humpback whales wintering
off Brazil may be displaced or even strand upon exposure to seismic
surveys (Engel et al., 2004). The evidence for this was circumstantial
and subject to alternative explanations (IAGC, 2004). Also, the
evidence was not consistent with subsequent results from the same area
of Brazil (Parente et al., 2006), or with direct studies of humpbacks
exposed to seismic surveys in other areas and seasons. After allowance
for data from subsequent years, there was ``no observable direct
correlation'' between strandings and seismic surveys (IWC, 2007:236).
There are no data on reactions of right whales to seismic surveys,
but results from the closely-related bowhead whale show that their
responsiveness can be quite variable depending on their activity
(migrating vs. feeding). Bowhead whales migrating west across the
Alaskan Beaufort Sea in autumn, in particular, are unusually
responsive, with substantial avoidance occurring out to distances of 20
- 30 km (12.4 - 18.6 mi) from a medium-sized airgun source at received
sound levels of around 120 130 dB re 1 microPa (rms) (Miller et al.,
1999; Richardson et al., 1999; see Appendix B (5) of the EA. However,
more recent research on bowhead whales (Miller et al., 2005; Harris et
al., 2007) corroborates earlier evidence that, during the summer
feeding season, bowheads are not as sensitive to seismic sources.
Nonetheless, subtle but statistically significant changes in surfacing
respiration dive cycles were evident upon statistical analysis
(Richardson et al., 1986). In summer, bowheads typically begin to show
avoidance reactions at received levels of about 152 178 dB re 1 microPa
(rms) (Richardson et al., 1986, 1995; Ljungblad et al., 1988; Miller et
al., 2005).
Reactions of migrating and feeding (but not wintering) gray whales
to seismic surveys have been studied. Malme et al. (1986, 1988) studied
the responses of feeding eastern Pacific gray whales to pulses from a
single 100-in\3\ airgun off St. Lawrence Island in the northern Bering
Sea. They estimated, based on small sample sizes, that 50 percent of
feeding gray whales stopped feeding at an average received pressure
level of 173 dB re 1 microPa on an (approximate) rms basis, and that 10
percent of feeding whales interrupted feeding at received levels of 163
dB re
[[Page 21637]]
1 microPa (rms). Those findings were generally consistent with the
results of experiments conducted on larger numbers of gray whales that
were migrating along the California coast (Malme et al., 1984; Malme
and Miles, 1985), and western Pacific gray whales feeding off Sakhalin
Island, Russia (Wursig et al., 1999; Gailey et al., 2007; Johnson et
al., 2007; Yazvenko et al., 2007a,b), along with data on gray whales
off British Columbia (Bain and Williams, 2006).
Various species of Balaenoptera (blue, sei, fin, and minke whales)
have occasionally been reported in areas ensonified by airgun pulses
(Stone, 2003; MacLean and Haley, 2004; Stone and Tasker, 2006).
Sightings by observers on seismic vessels off the United Kingdom from
1997 to 2000 suggest that, during times of good sightability, sighting
rates for mysticetes (mainly fin and sei whales) were similar when
large arrays of airguns were shooting vs. silent (Stone, 2003; Stone
and Tasker, 2006). However, these whales tended to exhibit localized
avoidance, remaining significantly further (on average) from the airgun
array during seismic operations compared with non-seismic periods
(Stone and Tasker, 2006). In a study off Nova Scotia, Moulton and
Miller (2005) found little difference in sighting rates (after
accounting for water depth) and initial sighting distances of
balaenopterid whales when airguns were operating versus silent.
However, there were indications that these whales were more likely to
be moving away when seen during airgun operations. Similarly, ship-
based monitoring studies of blue, fin, sei and minke whales offshore of
Newfoundland (Orphan Basin and Laurentian Sub-basin) found no more than
small differences in sighting rates and swim directions during seismic
vs. non-seismic periods Moulton et al., 2005, 2006a,b).
Data on short-term reactions by cetaceans to impulsive noises are
not necessarily indicative of long-term or biologically significant
effects. It is not known whether impulsive sounds affect reproductive
rate or distribution and habitat use in subsequent days or years.
However, gray whales have continued to migrate annually along the west
coast of North America with substantial increases in the population
over recent years, despite intermittent seismic exploration (and much
ship traffic) in that area for decades (Appendix A in Malme et al.,
1984; Richardson et al., 1995; Angliss and Outlaw, 2008). The western
Pacific gray whale population did not seem affected by a seismic survey
in its feeding ground during a previous year (Johnson et al., 2007).
Similarly, bowhead whales have continued to travel to the eastern
Beaufort Sea each summer, and their numbers have increased notably,
despite seismic exploration in their summer and autumn range for many
years (Richardson et al., 1987; Angliss and Outlaw, 2008).
Toothed Whales
Little systematic information is available about reactions of
toothed whales to noise pulses. Few studies similar to the more
extensive baleen whale/seismic pulse work summarized above and (in more
detail) in Appendix B of L-DEO's EA have been reported for toothed
whales. However, there are recent systematic studies on sperm whales
(Jochens et al., 2006; Miller et al., 2006), and there is an increasing
amount of information about responses of various odontocetes to seismic
surveys based on monitoring studies (e.g., Stone, 2003; Smultea et al.,
2004; Moulton and Miller, 2005; Bain and Williams, 2006; Holst et al.,
2006; Stone and Tasker, 2006; Potter et al., 2007; Weir, 2008).
Seismic operators and marine mammal observers on seismic vessels
regularly see dolphins and other small toothed whales near operating
airgun arrays, but in general there is a tendency for most delphinids
to show some avoidance of operating seismic vessels (e.g., Goold,
1996a,b,c; Calambokidis and Osmek, 1998; Stone, 2003; Moulton and
Miller, 2005; Holst et al., 2006; Stone and Tasker, 2006; Weir, 2008).
Some dolphins seem to be attracted to the seismic vessel and floats,
and some ride the bow wave of the seismic vessel even when large arrays
of airguns are firing (e.g., Moulton and Miller, 2005). Nonetheless,
small toothed whales more often tend to head away, or to maintain a
somewhat greater distance from the vessel, when a large array of
airguns is operating than when it is silent (e.g., Stone and Tasker,
2006; Weir, 2008). In most cases the avoidance radii for delphinids
appear to be small, on the order of 1 km less, and some individuals
show no apparent avoidance. The beluga (Delphinapterus leucas) is a
species that (at times) shows long-distance avoidance of seismic
vessels. Aerial surveys conducted in the southeastern Beaufort Sea
during summer found that sighting rates of beluga whales were
significantly lower at distances 10-20 km (6.2-12.4 mi) compared with
20-30 km (12.4-18.6 mi) from an operating airgun array, and observers
on seismic boats in that area rarely see belugas (Miller et al., 2005;
Harris et al., 2007).
Captive bottlenose dolphins (Tursiops truncates) and beluga whales
exhibited changes in behavior when exposed to strong pulsed sounds
similar in duration to those typically used in seismic surveys
(Finneran et al., 2000, 2002, 2005). However, the animals tolerated
high received levels of sound before exhibiting aversive behaviors.
Results for porpoises depend on species. The limited available data
suggest that harbor porpoises (Phocoena phocoena) show stronger
avoidance of seismic operations than do Dall's porpoises (Phocoenoides
dalli) (Stone, 2003; MacLean and Koski, 2005; Bain and Williams, 2006;
Stone and Tasker, 2006). Dall's porpoises seem relatively tolerant of
airgun operations (MacLean and Koski, 2005; Bain and Williams, 2006),
although they too have been observed to avoid large arrays of operating
airguns (Calambokidis and Osmek, 1998; Bain and Williams, 2006). This
apparent difference in responsiveness of these two porpoise species is
consistent with their relative responsiveness to boat traffic and some
other acoustic sources (Richardson et al., 1995; Southall et al.,
2007).
Most studies of sperm whales exposed to airgun sounds indicate that
the sperm whale shows considerable tolerance of airgun pulses (e.g.,
Stone, 2003; Moulton et al., 2005, 2006a; Stone and Tasker, 2006; Weir,
2008). In most cases the whales do not show strong avoidance, and they
continue to call (see Appendix B of L-DEO's EA for review). However,
controlled exposure experiments in the Gulf of Mexico indicate that
foraging behavior was altered upon exposure to airgun sound (Jochens et
al., 2006). In the Sperm Whale Seismic Study (SWSS), D-tags (Johnson
and Tyack, 2003) were used to record the movement and acoustic exposure
of eight foraging sperm whales before, during, and after controlled
sound exposures of airgun arrays in the Gulf of Mexico (Jochens et al.,
2008). Whales were exposed to maximum received sound levels between 111
and 147 dB re 1 microPa rms (131 - 164 dB re 1 microPa pk-pk) at ranges
of approximately 1.4 - 12.6 km (0.8 - 7.8 mi) from the sound source.
Although the tagged whales showed no horizontal avoidance, some whales
changed foraging behavior during full-array exposure (Jochens et al.,
2008).
There are almost no specific data on the behavioral reactions of
beaked whales to seismic surveys. However, northern bottlenose whales
continued to produce high-frequency clicks when exposed to sound pulses
from distant
[[Page 21638]]
seismic surveys (Laurinolli and Cochrane, 2005; Simard et al., 2005).
Most beaked whales tend to avoid approaching vessels of other types
(e.g., Wursig et al., 1998). They may also dive for an extended period
when approached by a vessel (e.g., Kasuya, 1986), although it is
uncertain how much longer such dives may be as compared to dives by
undisturbed beaked whales, which also are often quite long (Baird et
al., 2006; Tyack et al., 2006). In any event, it is likely that most
beaked whales would also show strong avoidance of an approaching
seismic vessel, although this has not been documented explicitly.
There are increasing indications that some beaked whales tend to
strand when naval exercises involving mid-frequency sonar operation are
ongoing nearby (e.g., Simmonds and Lopez-Jurado, 1991; Frantzis, 1998;
NOAA and USN, 2001; Jepson et al., 2003; Hildebrand, 2005; Barlow and
Gisiner, 2006; see also the ``Strandings and Mortality'' subsection,
later). These strandings are apparently at least in part a disturbance
response, although auditory or other injuries or other physiological
effects may also be involved. Whether beaked whales would ever react
similarly to seismic surveys is unknown (see ``Strandings and
Mortality'', below). Seismic survey sounds are quite different from
those of the sonars in operation during the above-cited incidents, and
in particular, the dominant frequencies in airgun pulses are at lower
frequencies than used by mid-frequency naval sonars.
Odontocete reactions to large arrays of airguns are variable and,
at least for delphinids and some porpoises (e.g., Dall's, Phocoenoides
dalli), seem to be confined to a smaller radius than has been observed
for the more responsive of the mysticetes, belugas, and harbor
porpoises (refer to Appendix B in L-DEO's EA).
Pinnipeds
Pinnipeds are not likely to show a strong avoidance reaction to the
airgun array. Visual monitoring from seismic vessels has shown only
slight (if any) avoidance of airguns by pinnipeds, and only slight (if
any) changes in behavior see Appendix B (5) of the EA. In the Beaufort
Sea, some ringed seals avoided an area of 100 m (328 ft) to (at most) a
few hundred meters around seismic vessels, but many seals remained
within 100 - 200 m (328 656 ft) of the trackline as the operating
airgun array passed by (e.g., Harris et al., 2001; Moulton and Lawson
2002; Miller et al., 2005). Ringed seal sightings averaged somewhat
farther away from the seismic vessel when the airguns were operating
than when they were not, but the difference was small (Moulton and
Lawson, 2002). Similarly, in Puget Sound, sighting distances for harbor
seals (Phoca vitulina) and California sea lions (Zalophus
californianus) tended to be larger when airguns were operating
(Calambokidis and Osmek, 1998). Previous telemetry work suggests that
avoidance and other behavioral reactions may be stronger than evident
to date from visual studies (Thompson et al., 1998). Even if reactions
of any pinnipeds that might be encountered in the present study area
are as strong as those evident in the telemetry study, reactions are
expected to be confined to relatively small distances and durations,
with no long-term effects on pinniped individuals or populations.
Hearing Impairment and Other Physical Effects
Temporary or permanent hearing impairment is a possibility when
marine mammals are exposed to very strong sounds, and temporary
threshold shift (TTS) has been demonstrated and studied in certain
captive odontocetes and pinnipeds exposed to strong sounds (reviewed in
Southall et al., 2007).
Current NMFS policy regarding exposure of marine mammals to high-
level sounds is that cetaceans and pinnipeds should not be exposed to
impulsive sounds with received levels greater than or equal to 180 and
190 dB re 1 microPa rms, respectively (NMFS 2000). L-DEO has used those
criteria to establish the exclusion (i.e., shut-down) zones planned for
the proposed seismic survey. However, those criteria were established
before there was any information about minimum received levels of
sounds necessary to cause auditory impairment in marine mammals. As
discussed in Appendix B of the EA: (1) the 180-dB criterion for
cetaceans is probably quite precautionary, i.e., lower than necessary
to avoid temporary auditory impairment let alone permanent auditory
injury; (2) NMFS treats TTS as the upper bound of Level B Harassment.
Tissues are not irreparably damaged with the onset of TTS, the effects
are temporary (particularly for onset-TTS), and NMFS does not believe
that this effect qualifies as an injury; (3) the minimum sound level
necessary to cause permanent hearing impairment (``Level A
harassment'') is higher, by a variable and generally unknown amount,
than the level that induces barely detectable TTS; and (4) the level
associated with the onset of TTS is often considered to be a level
below which there is no danger of permanent damage. The actual PTS
threshold is likely to be well above the level causing onset of TTS
(Southall et al., 2007).
Recommendations for new science-based noise exposure criteria for
marine mammals, frequency-weighting procedures, and related matters
were published recently (Southall et al., 2007). Those recommendations
have not, as of early 2009, been formally adopted by NMFS for use in
regulatory processes and during mitigation programs associated with
seismic surveys. However, some aspects of the recommendations have been
taken into account in certain Environmental Impact Statements and
small-take authorizations. NMFS has indicated that it may issue new
noise exposure criteria for marine mammals that account for the now
available scientific data on TTS, the expected offset between the TTS
and PTS thresholds, differences in the acoustic frequencies to which
different marine mammal groups are sensitive, and other relevant
factors. Preliminary information about possible changes in the
regulatory and mitigation requirements, and about the possible
structure of new criteria, was given by Wieting (2004) and NMFS (2005).
Several aspects of the planned monitoring and mitigation measures
for this project are designed to detect marine mammals occurring near
the airgun array, and to avoid exposing them to sound pulses that
might, at least in theory, cause hearing impairment (see section XI of
L-DEO's application). In addition, many cetaceans and (to a limited
degree) pinnipeds and sea turtles show some avoidance of the area where
received levels of airgun sound are high enough such that hearing
impairment could potentially occur. In those cases, the avoidance
responses of the animals themselves will reduce or (most likely) avoid
any possibility of hearing impairment.
Non-auditory physical effects might also occur in marine mammals
exposed to strong underwater pulsed sound. Possible types of non-
auditory physiological effects or injuries that might (in theory) occur
in mammals close to a strong sound source include stress, neurological
effects, bubble formation, and other types of organ or tissue damage.
It is possible that some marine mammal species (i.e., beaked whales)
may be especially susceptible to injury and/or stranding when exposed
to strong pulsed sounds. However, as discussed below, there is no
definitive evidence that any of these effects occur even for marine
mammals in close proximity to large arrays of airguns. It is unlikely
that any effects of these types would occur during the proposed
[[Page 21639]]
project given the brief duration of exposure of any given mammal, the
deep water in the survey area, and the planned monitoring and
mitigation measures (see below). The following subsections discuss in
somewhat more detail the possibilities of TTS, PTS, and non-auditory
physical effects.
Temporary Threshold Shift (TTS)
TTS is the mildest form of hearing impairment that can occur during
exposure to a strong sound (Kryter, 1985). While experiencing TTS, the
hearing threshold rises and a sound must be stronger in order to be
heard. In terrestrial mammals, TTS can last from minutes or hours to
(in cases of strong TTS) days. For sound exposures at or somewhat above
the TTS threshold, hearing sensitivity in both terrestrial and marine
mammals recovers rapidly after exposure to the noise ends. Few data on
sound levels and durations necessary to elicit mild TTS have been
obtained for marine mammals, and none of the published data concern TTS
elicited by exposure to multiple pulses of sound. Available data on TTS
in marine mammals are summarized in Southall et al. (2007).
For toothed whales exposed to single short pulses, the TTS
threshold appears to be, to a first approximation, a function of the
energy content of the pulse (Finneran et al., 2002, 2005). Given the
available data, the received energy level of a single seismic pulse
(with no frequency weighting) might need to be approximately 186 dB re
1 microPa\2\s (i.e., 186 dB SEL or approximately 196 201 dB re
1 microPa rms in order to produce brief, mild TTS. Exposure to several
strong seismic pulses that each have received levels near 190 dB re 1
microPa rms might result in cumulative exposure of approximately 186 dB
SEL and thus slight TTS in a small odontocete, assuming the TTS
threshold is (to a first approximation) a function of the total
received pulse energy. The distances from the Langseth's airguns at
which the received energy level (per pulse, flat-weighted) would be
expected to be greater than or equal to 190 dB re 1 microPa rms are
estimated in Table 1. Levels greater than or equal to 190 dB re 1
microPa rms are expected to be restricted to radii no more than 380 m
(1246 ft) (See Table 1). For an odontocete closer to the surface, the
maximum radius with greater than or equal to 190 dB re 1 microPa rms
would be smaller.
The above TTS information for odontocetes is derived from studies
on the bottlenose dolphin and beluga. There is no published TTS
information for other types of cetaceans. However, preliminary evidence
from a harbor porpoise exposed to airgun sound suggests that its TTS
threshold may have been lower (Lucke et al., 2007).
For baleen whales, there are no data, direct or indirect, on levels
or properties of sound that are required to induce TTS. The frequencies
to which baleen whales are most sensitive are assumed to be lower than
those to which odontocetes are most sensitive, and natural background
noise levels at those low frequencies tend to be higher. As a result,
auditory thresholds of baleen whales within their frequency band of
best hearing are believed to be higher (less sensitive) than are those
of odontocetes at their best frequencies (Clark and Ellison, 2004).
From this, it is suspected that received levels causing TTS onset may
also be higher in baleen whales (Southall et al., 2007). In any event,
no cases of TTS are expected given three considerations: (1) the low
abundance of baleen whales in most parts of the planned study area; (2)
the strong likelihood that baleen whales would avoid the approaching
airguns (or vessel) before being exposed to levels high enough for TTS
to occur; and (3) the mitigation measures that are planned.
In pinnipeds, TTS thresholds associated with exposure to brief
pulses (single or multiple) of underwater sound have not been measured.
Initial evidence from more prolonged (non-pulse) exposures suggested
that some pinnipeds (harbor seals in particular) incur TTS at somewhat
lower received levels than do small odontocetes exposed for similar
durations (Kastak et al., 1999, 2005; Ketten et al., 2001). The TTS
threshold for pulsed sounds has been indirectly estimated as being an
SEL of approximately 171 dB re 1 microPa\2\s (Southall et al.,
2007), which would be equivalent to a single pulse with received level
of approximately 181 - 186 dB re 1 microPa (rms), or a series of pulses
for which the highest rms values are a few dB lower. Corresponding
values for California sea lions and northern elephant seals (Mirounga
angustirostris) are likely to be higher (Kastak et al., 2005).
NMFS (1995, 2000) concluded that cetaceans and pinnipeds should not
be exposed to pulsed underwater noise at received levels exceeding 180
and 190 dB re 1 microPa rms, respectively. Those sound levels are not
considered to be the levels above which TTS might occur. Rather, they
were the received levels above which, in the view of a panel of
bioacoustics specialists convened by NMFS before TTS measurements for
marine mammals started to become available, one could not be certain
that there would be no injurious effects, auditory or otherwise, to
marine mammals. As summarized above and in Southall et al. (2007), data
that are now available imply that TTS is unlikely to occur in most
odontocetes (and probably mysticetes as well) unless they are exposed
to a sequence of several airgun pulses in which the strongest pulse has
a received level substantially exceeding 180 dB re 1 microPa rms. On
the other hand, for the harbor seal and any species with similarly low
TTS thresholds (possibly including the harbor porpoise), TTS may occur
upon exposure to one or more airgun pulses whose received level equals
the NMFS ``do not exceed'' value of 190 dB re 1 microPa rms. That
criterion corresponds to a single-pulse SEL of
175 - 180 dB re 1 microPa\2\s in typical conditions,
whereas TTS is suspected to be possible (in harbor seals) with a
cumulative SEL of approximately 171 dB re 1 microPa\2\s.
Permanent Threshold Shift (PTS)
When PTS occurs, there is physical damage to the sound receptors in
the ear. In severe cases, there can be total or partial deafness, while
in other cases; the animal has an impaired ability to hear sounds in
specific frequency ranges (Kryter, 1985).
There is no specific evidence that exposure to pulses of airgun
sound can cause PTS in any marine mammal, even with large arrays of
airguns. However, given the possibility that mammals close to an airgun
array might incur at least mild TTS, there has been further speculation
about the possibility that some individuals occurring very close to
airguns might incur PTS (Richardson et al., 1995, p. 372ff). Single or
occasional occurrences of mild TTS are not indicative of permanent
auditory damage.
Relationships between TTS and PTS thresholds have not been studied
in marine mammals, but are assumed to be similar to those in humans and
other terrestrial mammals. PTS might occur at a received sound level at
least sever
