Takes of Marine Mammals Incidental to Specified Activities; Low-Energy Marine Geophysical Survey in the Gulf of Mexico, April to May, 2013, 11821-11844 [2013-03837]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 78, Number 34 (Wednesday, February 20, 2013)]
[Notices]
[Pages 11821-11844]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2013-03837]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XC389


Takes of Marine Mammals Incidental to Specified Activities; Low-
Energy Marine Geophysical Survey in the Gulf of Mexico, April to May, 
2013

AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and 
Atmospheric Administration (NOAA), Commerce.

ACTION: Notice; proposed Incidental Harassment Authorization; request 
for comments.

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SUMMARY: NMFS has received an application from the U.S. Geological 
Survey (USGS), for an Incidental Harassment Authorization (IHA) to take 
marine mammals, by harassment, incidental to conducting a low-energy 
marine geophysical (seismic) survey in the Gulf of Mexico, April to 
May, 2013. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is 
requesting comments on its proposal to issue an IHA to USGS to 
incidentally harass, by Level B harassment only, 19 species of marine 
mammals during the specified activity.

DATES: Comments and information must be received no later than March 
22, 2013.

ADDRESSES: Comments on the application should be addressed to P. 
Michael Payne, Chief, Permits and Conservation Division, Office of 
Protected Resources, National Marine Fisheries Service, 1315 East-West 
Highway, Silver Spring, MD 20910. The mailbox address for providing 
email comments is ITP.Goldstein@noaa.gov. NMFS is not responsible for 
email comments sent to addresses other than the one provided here. 
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

[[Page 11822]]

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 above address, 
telephoning the contact listed here (see FOR FURTHER INFORMATION 
CONTACT) or visiting the internet at: https://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications.
    The USGS has prepared a draft ``Environmental Assessment and 
Determination Pursuant to the National Environmental Policy Act, 42 
U.S.C. 4321 et seq. and Executive Order 12114 Low-Energy Marine Seismic 
Survey by the U.S. Geological Survey in the Deepwater Gulf of Mexico, 
April-May 2013'' (EA). USGS's EA incorporates a draft ``Environmental 
Assessment of a Low-Energy Marine Geophysical Survey by the U.S. 
Geological Survey in the Northwestern Gulf of Mexico, April-May 
2013,'', prepared by LGL Ltd., Environmental Research Associates, on 
behalf of USGS, which is also available at the same Internet address. 
Documents cited in this notice may be viewed, by appointment, during 
regular business hours, at the aforementioned address.

FOR FURTHER INFORMATION CONTACT: Howard Goldstein or Jolie Harrison, 
Office of Protected Resources, NMFS, 301-427-8401.

SUPPLEMENTARY INFORMATION:

Background

    Section 101(a)(5)(D) of the MMPA, as amended (16 U.S.C. 1371 
(a)(5)(D)), directs the Secretary of Commerce (Secretary) to authorize, 
upon request, the incidental, but not intentional, taking of small 
numbers of marine mammals of a species or population stock, 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, if the taking is limited to harassment, a notice 
of a proposed authorization is provided to the public for review.
    Authorization for the incidental taking of small numbers of marine 
mammals shall be granted if NMFS finds that the taking will have a 
negligible impact on the species or stock(s), and will not have an 
unmitigable adverse impact on the availability of the species or 
stock(s) for subsistence uses (where relevant). The authorization must 
set forth the permissible methods of taking, other means of effecting 
the least practicable adverse impact on the species or stock and its 
habitat, and requirements pertaining to the mitigation, monitoring and 
reporting of such takings. NMFS has defined ``negligible impact'' in 50 
CFR 216.103 as ``[hellip]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. 
Section 101(a)(5)(D) of the MMPA establishes a 45-day time limit for 
NMFS's 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. Within 45 days of the 
close of the public comment period, NMFS must either issue or deny the 
authorization.
    Except with respect to certain activities not pertinent here, the 
MMPA defines ``harassment'' as: any act of pursuit, torment, or 
annoyance which (i) has the potential to injure a marine mammal or 
marine mammal stock in the wild [Level A harassment]; or (ii) has the 
potential to disturb a marine mammal or marine mammal stock in the wild 
by causing disruption of behavioral patterns, including, but not 
limited to, migration, breathing, nursing, breeding, feeding, or 
sheltering [Level B harassment].

Summary of Request

    On November 5, 2012, NMFS received an application from the USGS 
requesting that NMFS issue an IHA for the take, by Level B harassment 
only, of small numbers of marine mammals incidental to conducting a 
low-energy marine seismic survey within the U.S. Exclusive Economic 
Zone in the deep water of the Gulf of Mexico during April to May 2013. 
The USGS plans to use one source vessel, the R/V Pelican (Pelican), or 
similar vessel, and a seismic airgun array to collect seismic data as 
part of the ``Gas Hydrates Project'' in the deep water of the northwest 
Gulf of Mexico. The USGS plans to use conventional low-energy, seismic 
methodology and ocean bottom seismometers (OBSs) to acquire the data 
necessary to delineate the distribution, saturation, and thickness of 
sub-seafloor methane hydrates and to image near-seafloor structure 
(e.g., faults) at high-resolution. In addition to the proposed 
operations of the seismic airgun array and hydrophone streamer, USGS 
intends to operate a sub-bottom profiler continuously throughout the 
survey.
    Acoustic stimuli (i.e., increased underwater sound) generated 
during the operation of the seismic airgun array may have the potential 
to cause a behavioral disturbance for marine mammals in the survey 
area. This is the principal means of marine mammal taking associated 
with these activities, and USGS has requested an authorization to take 
19 species of marine mammals by Level B harassment. Take is not 
expected to result from the use of the sub-bottom profiler, for reasons 
discussed in this notice; nor is take expected to result from collision 
with the source vessel because it is a single vessel moving at a 
relatively slow speed (4.5 knots [kts]; 8.1 kilometers per hour [km/
hr]; 5.0 miles per hour [mph]) during seismic acquisition within the 
survey, for a relatively short period of time (approximately 8 days of 
airgun operations out of 15 total operational days). It is likely that 
any marine mammal would be able to avoid the vessel.

Description of the Proposed Specified Activity

    USGS proposes to conduct a low-energy seismic survey at two sites 
that have been studied as part of the Gulf of Mexico Gas Hydrates Joint 
Industry Project. The GC955 (i.e., Green Canyon lease block 955) and 
WR313 (i.e., Walker Ridge lease block 313) study sites are located in 
the deep water of the northwestern GOM (see Figure 1 of the IHA 
application). Study site GC955 will be surveyed first, followed by 
WR313. The seismic survey is scheduled to take place for approximately 
eight days (out of 15 total operational days) in April to May 2013.
    The purpose of USGS's proposed seismic survey is to develop 
technology and to collect data to assist in the characterization of 
marine gas hydrates in order to better understand their impact on 
seafloor stability, their role in climate change, and their potential 
as an energy source. These sites have been extensively studied, 
including detailed logging while drilling (LWD), and are known to hold 
thick sequences of sand containing high saturations of gas hydrate. The 
purpose of this new seismic acquisition is to expand outward from the 
boreholes the detailed characterization that has been accomplished 
there and to develop and calibrate improved geophysical

[[Page 11823]]

techniques for gas hydrate characterization.
    The proposed survey will involve one source vessel, most likely the 
R/V Pelican (Pelican) or a similar vessel. USGS will deploy two (each 
with a discharge volume of 105 cubic inch [in\3\]) Generator Injector 
(GI) airgun array as a primary energy source at a tow depth of 3 m (9.8 
ft). A subset of the survey lines will be repeated using either a 
single 35 in\3\ GI airgun. The receiving system will consist of one 450 
meter (m) (1,476.4 feet [ft]) long, 72-channel hydrophone streamer and 
25 ocean bottom seismometers (OBSs). As the GI airguns are towed along 
the survey lines, the hydrophone streamer will receive the returning 
acoustic signals and transfer the data to the onboard processing 
system. The OBSs record the returning acoustic signals internally for 
later analysis. Regardless of which energy source is used, the 
calculated isopleths for the two GI (105 in\3\) airguns will be used.
    At each of the two study sites, 25 OBSs will be deployed and a 
total of approximately 700 km (378 nautical miles [nmi]) of survey 
lines will be collected in a grid pattern (see Figure 1 of the IHA 
application). The water depth will be 1,500 to 2,000 m (4,921.3 to 
6,561.7 ft) at each study site). All planned seismic data acquisition 
activities will be conducted by technicians provided by USGS with 
onboard assistance by the scientists who have proposed the study. The 
Principal Investigators are Dr. Seth Haines (USGS Energy Program, 
Denver, Colorado) and Mr. Patrick Hart (USGS Coastal and Marine 
Geology, Santa Cruz, California). The vessel will be self-contained, 
and the crew will live aboard the vessel for the entire cruise.
    The planned seismic survey (e.g., equipment testing, startup, line 
changes, repeat coverage of any areas, and equipment recovery) will 
consist of approximately 1,480 km (799.1 nmi) of transect lines 
(including turns) in the survey area in the deep water of the 
northwestern Gulf of Mexico (GOM) (see Figure 1 of the IHA 
application). In addition to the operation of the airgun array, a 
Knudsen sub-bottom profiler will also likely be operated from the 
Pelican continuously throughout the cruise. USGS will not be operating 
a multibeam system, the Pelican is not equipped with this equipment. 
There will be additional seismic operations associated with equipment 
testing, ramp-up, and possible line changes or repeat coverage of any 
areas where initial data quality is sub-standard. In USGS's estimated 
take calculations, 25% has been added for those additional operations.

Vessel Specifications

    The Pelican (although a similar vessel might be used for this 
proposed program), a research vessel owned by the Louisiana 
Universities Marine Consortium (LUMCON), will tow the two GI airgun 
array, as well as the hydrophone streamer, along predetermined lines 
(see Figure 1 of the IHA application). When the Pelican is towing the 
airgun array and the relatively short hydrophone streamer, the turning 
rate of the vessel while the gear is deployed is limited to better than 
5 degrees per a minute (this is higher than a seismic vessel towing a 
streamer of more typical length much greater than 1 km [0.5 nmi]). The 
LUMCON Marine Superintendent estimates that the turning radius of the 
Pelican will be approximately 500 m (1,640.4 ft) while the vessel is 
towing the hydrophone streamer. Thus, the maneuverability of the vessel 
is not limited much during operations with the streamer. The vessel 
would ``fly'' the appropriate U.S. Coast Guard-approved day shapes 
(mast head signals used to communicate with other vessels) and display 
the appropriate lighting to designate the vessel has limited 
maneuverability.
    The vessel has a length of 33.5 m (109.9 ft); a beam of 8.0 m (26.3 
ft); a full load draft of 2.9 m (9.5 ft); and a gross tonnage of 261. 
The ship is equipped with two Caterpillar Model 3412 1648 in\3\ diesel 
engines and an 80 horsepower (hp) Schottel bowthruster. Electrical 
power is provided by two Caterpillar 3306, 99 kiloWatt (kW) diesel 
generators. The Pelican's operation speed during seismic acquisition is 
typically approximately 8.1 km per hour (hr) (km/hr) (4.5 knots [kts]). 
When not towing seismic survey gear, the Pelican typically cruises at 
17 km/hr (9.2 kts). The Pelican has an operating range of approximately 
5,600 km (3,023.8 nmi) (the distance the vessel can travel without 
refueling).
    The vessel also has two locations as likely observation stations 
from which Protected Species Observers (PSO) will watch for marine 
mammals before and during the proposed airgun operations on the 
Pelican. When stationed on the observation platforms, the PSO's eye 
level will be approximately 12 m (39.4 ft) above sea level providing 
the PSO an approximately 210[deg] view aft of the vessel from the aft 
control station, and from the bridge station the PSO's eye level will 
be approximately 13 m (42.7 ft) above sea level providing the PSO an 
unobstructed 360[deg] view around the entire vessel. More details of 
the Pelican can be found in the IHA application.

Acoustic Source Specifications

Seismic Airguns

    The Pelican (or similar vessel) will deploy an airgun array, 
consisting of two 105 in\3\ Sercel GI airguns as the primary energy 
source and a streamer containing hydrophones along predetermined lines. 
A subset of the survey lines will be repeated using a single 35 in\3\ 
GI airgun. The airgun array will have a firing pressure of 2,000 pounds 
per square inch (psi). Discharge intervals depend on both the ship's 
speed and Two Way Travel Time recording intervals. Seismic pulses for 
the GI airguns will be emitted at intervals of approximately 6 to 10 
seconds. At speeds of approximately 8.1 km/hr, the shot intervals 
correspond to spacing of approximately will be 14 to 23 m (45.9 to 75.5 
ft) during the study. During firing, a brief (approximately 0.03 
second) pulse sound is emitted; the airguns will be silent during the 
intervening periods. The dominant frequency components range from zero 
to 188 Hertz (Hz).
    The generator chamber of each GI airgun in the primary source, the 
one responsible for introducing the sound pulse into the ocean, is 105 
in\3\. The injector chamber injects air into the previously-generated 
bubble to maintain its shape, and does not introduce more sound into 
the water. The two GI airguns will be towed 8 m (26.2 ft) apart, side-
by-side, 21 m (68.9 ft) behind the Pelican, at a depth of 3 m (9.8 ft) 
during the surveys. The total effective volume will be 210 in\3\.
    The single 35 in\3\ GI airgun is the same type of dual chamber 
airgun as the 105 in\3\ GI airgun described above, with the generator 
and injector chambers each being 35 in\3\. The manufacturer's 
literature indicates that a 35 in\3\ GI airgun has a root mean square 
(rms) source level of approximately 208 dB re 1 [mu]Pam, a duration of 
about 10 ms, and dominant frequency components of less than 500 Hz. 
Field measurements by USGS personnel indicate that the GI airgun 
outputs low sound amplitudes at frequencies greater than 500 Hz. The 35 
in\3\ GI airgun will be towed approximately 15 m (49.2 ft) behind the 
ship at approximately 2 m (6.6 ft) depth.
    As the GI airgun(s) is towed along the survey line, the towed 
hydrophone array in the streamer receives the reflected signals and 
transfers the data to the on-board processing system. The OBSs record 
the returning acoustic signals internally for later analysis. Given the 
relatively short streamer

[[Page 11824]]

length behind the vessel, the turning rate of the vessel while the gear 
is deployed is much higher than the limit of five degrees per minute 
for a seismic vessel towing a streamer of more typical length (i.e., 
much greater than 1 km [0.54 nmi]). Thus, the maneuverability of the 
vessel is not limited much during seismic operations.

Metrics Used in This Document

    This section includes a brief explanation of the sound measurements 
frequently used in the discussions of acoustic effects in this 
document. Sound pressure is the sound force per unit area, and is 
usually measured in micropascals ([mu]Pa), where 1 pascal (Pa) is the 
pressure resulting from a force of one newton exerted over an area of 
one square meter. Sound pressure level (SPL) is expressed as the ratio 
of a measured sound pressure and a reference level. The commonly used 
reference pressure level in underwater acoustics is 1 [mu]Pa, and the 
units for SPLs are dB re: 1 [mu]Pa. SPL (in decibels [dB]) = 20 log 
(pressure/reference pressure).
    SPL is an instantaneous measurement and can be expressed as the 
peak, the peak-peak (p-p), or the rms. Root mean square (rms), which is 
the square root of the arithmetic average of the squared instantaneous 
pressure values, is typically used in discussions of the effects of 
sounds on vertebrates and all references to SPL in this document refer 
to the root mean square unless otherwise noted. SPL does not take the 
duration of a sound into account.

Characteristics of the Airgun Pulses

    Airguns function by venting high-pressure air into the water which 
creates an air bubble. The pressure signature of an individual airgun 
consists of a sharp rise and then fall in pressure, followed by several 
positive and negative pressure excursions caused by the oscillation of 
the resulting air bubble. The oscillation of the air bubble transmits 
sounds downward through the seafloor and the amount of sound 
transmitted in the near horizontal directions is reduced. However, the 
airgun array also emits sounds that travel horizontally toward non-
target areas.
    The nominal downward-directed source levels of the airgun arrays 
used by USGS on the Pelican do not represent actual sound levels that 
can be measured at any location in the water. Rather they represent the 
level that would be found 1 m (3.3 ft) from a hypothetical point source 
emitting the same total amount of sound as is emitted by the combined 
GI airguns. The actual received level at any location in the water near 
the GI airguns will not exceed the source level of the strongest 
individual source. In this case, that will be about 234.4 dB re 1 
[micro]Pam peak, or 239.8 dB re 1 [micro]Pam peak-to-peak. However, the 
difference between rms and peak or peak-to-peak values for a given 
pulse depends on the frequency content and duration of the pulse, among 
other factors. Actual levels experienced by any organism more than 1 m 
from either GI airgun will be significantly lower.
    Accordingly, Lamont-Doherty Earth Observatory of Columbia 
University (L-DEO) has predicted the received sound levels in relation 
to distance and direction from the two GI airgun array. A detailed 
description of L-DEO's modeling for this survey's marine seismic source 
arrays for protected species mitigation is provided in the NSF/USGS 
PEIS. These are the nominal source levels applicable to downward 
propagation. The NSF/USGS PEIS discusses the characteristics of the 
airgun pulses. NMFS refers the reviewers to that documents for 
additional information.

Predicted Sound Levels for the Airguns

    To determine exclusion zones for the airgun array to be used in the 
deep water of the GOM, received sound levels have been modeled by L-DEO 
for a number of airgun configurations, including two 105 in\3\ GI 
airguns, in relation to distance and direction from the airguns (see 
Figure 2 of the IHA application). The model does not allow for bottom 
interactions, and is most directly applicable to deep water. Based on 
the modeling, estimates of the maximum distances from the GI airguns 
where sound levels of 190, 180, and 160 dB re 1 [micro]Pa (rms) are 
predicted to be received in deep water are shown in Table 1 (see Table 
1 of the IHA application). Received sound levels have not been modeled 
for the single 35 in\3\ GI airgun, but maximum distances for that 
source would be much lower than those for the two 105 in\3\ GI airguns. 
USGS and NMFS will use the results for the two 105 in\3\ GI airguns for 
all seismic lines, resulting in conservative (precautionary for marine 
mammals) results when the smaller sources are used.
    Empirical data concerning the 190, 180, and 160 dB (rms) distances 
were acquired for various airgun arrays based on measurements during 
the acoustic verification studies conducted by L-DEO in the northern 
GOM in 2003 (Tolstoy et al., 2004) and 2007 to 2008 (Tolstoy et al., 
2009). Results of the 36 airgun array are not relevant for the two GI 
airguns to be used in the proposed survey. The empirical data for the 
6, 10, 12, and 20 airgun arrays indicate that, for deep water, the L-
DEO model tends to overestimate the received sound levels at a given 
distance (Tolstoy et al., 2004). Measurements were not made for the two 
GI airgun array in deep water; however, USGS proposes to use the buffer 
and exclusion zones predicted by L-DEO's model for the proposed GI 
airgun operations in deep water, although they are likely conservative 
given the empirical results for the other arrays. Using the L-DEO 
model, Table 1 (below) shows the distances at which three rms sound 
levels are expected to be received from the two GI airguns. The 180 and 
190 dB re 1 [micro]Pam (rms) distances are the safety criteria for 
potential Level A harassment as specified by NMFS (2000) and are 
applicable to cetaceans and pinnipeds, respectively. If marine mammals 
are detected within or about to enter the appropriate exclusion zone, 
the airguns will be shut-down immediately. Table 1 summarizes the 
predicted distances at which sound levels (160, 180, and 190 dB [rms]) 
are expected to be received from the two GI airgun array operating in 
deep water depths.
    Table 1 summarizes the predicted distances at which sound levels 
(160, 180, and 190 dB [rms]) are expected to be received from the two 
airgun array operating in deep water (greater than 1,000 m [3,280 ft]) 
depths. For the proposed project, USGS plans to use the distances for 
the two 105 in\3\ GI airguns for the single 35 in\3\ GI airgun, for the 
determination of the buffer and exclusion zones since this represents 
the largest and therefore most conservative distances determined by the 
model results provided by L-DEO.
    Table 1. Modeled (two 105 in\3\ GI airgun array) distances to which 
sound levels >= 190, 180, and 160 dB re: 1 [mu]Pa (rms) could be 
received in deep water during the proposed survey in the northwestern 
GOM, April to May, 2013.

[[Page 11825]]



----------------------------------------------------------------------------------------------------------------
                                                                       Predicted RMS radii distances (m) for 2
                                                                                     airgun array
       Source and volume          Tow depth (m)    Water depth (m)  --------------------------------------------
                                                                                                             160
                                                                           190 dB              180 dB         dB
----------------------------------------------------------------------------------------------------------------
Two GI Airguns (105 in\3\).....               3  Deep (> 1,000)....  20 m..............  70 m..............  670
                                                                     (65.6 ft).........  (229.7 ft)........   m
                                                                                                             (2,
                                                                                                             198
                                                                                                             .2
                                                                                                             ft)
----------------------------------------------------------------------------------------------------------------

    Along with the airgun operations, one additional acoustical data 
acquisition systems may be operated from the Pelican continuously 
during the survey. A hull-mounted Knudsen 3.5 kHz sub-bottom profiler 
(successor to model 320B) may be available since the Pelican is 
considering such an installation in the coming months. They have not 
yet chosen the exact equipment. The ocean floor may be mapped with the 
Knudsen sub-bottom profiler. If the sub-bottom profiler is available, 
USGS will use it if it provides quality supplemental information that 
enhances the higher-energy (i.e., GI airguns) surveys or site 
characterization in the immediate vicinity of an OBS deployment. This 
sound source would be operated continuously from the Pelican throughout 
the cruise.

Sub-Bottom Profiler

    The Pelican may operate a Knudsen 3.5 kHz sub-bottom continuously 
throughout the cruise simultaneously to map and provide information 
about the sedimentary features and bottom topography. The beam of the 
sub-bottom profiler is transmitted as a 27[deg] cone, which is directed 
downward by a 3.5 kHz transducer in the hull of the Pelican. The 
maximum output is 1 kilowatt (kW) (approximately 204 dB re: 1 [mu]Pam), 
but in practice, the output varies with water depth. Pulse duration is 
1, 2, or 4 milliseconds (ms).
    The sub-bottom profiler is operated continuously during survey 
operations. Power levels of the instrument would be modified to account 
for water depth. Actual operating parameters will be established at the 
time of the survey. This type of 3.5 kHz system falls within Appendix F 
(low-energy) of the NSF/USGS PEIS.
    NMFS expects that acoustic stimuli resulting from the proposed 
operation of the two GI airgun array has the potential to harass marine 
mammals., NMFS does not expect that the movement of the Pelican, during 
the conduct of the seismic survey, has the potential to harass marine 
mammals because of the relatively slow operation speed of the vessel 
(approximately 4.5 knots [kts]; 8.3 km/hr; 5.2 mph) during seismic 
acquisition.

Ocean Bottom Seismometers

    For the proposed study, 25 OBSs will be deployed from the Pelican 
at each of the two study sites in sequence (see Figure 1 of the IHA 
application). Once the seismic surveys have been completed at the first 
site, the OBSs will be retrieved, then re-deployed at the second site. 
Once the seismic surveys have been completed at the second site, OBSs 
will be retrieved. OBSs operated by the U.S. National OBS Instrument 
Pool will be used during the proposed cruise. This type of OBS has a 
height of approximately 1 m (3.3 ft) and a maximum diameter of 50 
centimeters (cm) (19.7 inches [in]). The anchor is a steel plate 
weighing approximately 40 kilograms (kg) (88.2 pounds [lb]) with 
dimensions approximately 30x30x8 cm (11.8x11.8x3.1 in). Once an OBS is 
ready to be retrieved, an acoustic release transponder interrogates the 
instrument at a frequency of 9 to 11 kiloHertz (kHz), and a response is 
received at a frequency of 9 to 13 kHz. The burn-wire release assembly 
is then activated, and the instrument is released from the anchor to 
float to the surface.

Dates, Duration, and Specified Geographic Region

    The proposed project will be located near the GC955 and WR313 study 
sites in the deep water of the northwest Gulf of Mexico and would have 
a total duration of approximately 15 operational days occurring during 
the April through May 2013 timeframe, which will include approximately 
8 days of active seismic airgun operations. Water depth at the site is 
approximately 2,000 m (6561.7 ft). The total survey time would be 
approximately 96 hours at each site. The proposed survey is scheduled 
from April 16 to May 5, 2013. The Pelican is expected to depart and 
return to Cocodrie, Louisiana, with no intermediate stops.
    Some minor deviation from this schedule is possible, depending on 
logistics and weather (i.e., the cruise may depart earlier or be 
extended due to poor weather; there could be additional days of seismic 
operations if collected data are deemed to be of substandard quality).
    The latitude and longitude for the bounds of the two study sites 
are:

WR313:
    91[deg] 34.75' West to 91[deg] 46.75' West
    26[deg] 33.75' North to 26[deg] 45.75' North
GC955:
    90[deg] 20.0' West to 90[deg] 31.75' West
    26[deg] 54.1' North to 27[deg] 6.0' North

Description of the Marine Mammals in the Area of the Proposed Specified 
Activity

    The marine mammal species that potentially occur within the GOM 
include 28 species of cetaceans and one sirenian (Jefferson and Schiro, 
1997; Wursig et al., 2000; see Table 2 below). In addition to the 28 
species known to occur in the GOM, the long-finned pilot whale 
(Globicephala melas), long-beaked common dolphin (Delphinus capensis), 
and short-beaked common dolphin (Delphinus delphis) could potentially 
occur there. However, there are no confirmed sightings of these species 
in the GOM, but they have been seen close and could eventually be found 
there (Wursig et al., 2000). Those three species are not considered 
further in this document. The marine mammals that generally occur in 
the proposed action area belong to three taxonomic groups: mysticetes 
(baleen whales), odontocetes (toothed whales), and sirenians (the West 
Indian manatee). Of the marine mammal species that potentially occur 
within the GOM, 21 species of cetaceans (20 odontocetes, 1 mysticete) 
are routinely present and have been included in the analysis for 
incidental take to the proposed seismic survey. Marine mammal species 
listed as endangered under the U.S. Endangered Species Act of 1973 
(ESA; 16 U.S.C. 1531 et seq.), includes the North Atlantic right 
(Eubalaena glacialis), humpback (Megaptera novaeangliae), sei 
(Balaenoptera borealis), fin (Balaenoptera physalus), blue 
(Balaenoptera musculus), and sperm (Physeter macrocephalus) whale, as 
well as the West Indian (Florida) manatee (Trichechus manatus 
latirostris). Of those endangered species, only the sperm whale is 
likely to be encountered in the proposed survey area. No species of 
pinnipeds are known to occur regularly in the GOM, and any pinniped 
sighted in the proposed study area would be considered extralimital. 
The Caribbean monk seal (Monachus tropicalis) used to inhabit the GOM 
but is considered extinct and has been

[[Page 11826]]

delisted from the ESA. The West Indian manatee is the one marine mammal 
species mentioned in this document that is managed by the U.S. Fish and 
Wildlife Service (USFWS) and is not considered further in this 
analysis; all others are managed by NMFS.
    In general, cetaceans in the GOM appear to be partitioned by 
habitat preferences likely related to prey distribution (Baumgartner et 
al., 2001). Most species in the northern GOM concentrated along the 
upper continental slope in or near areas of cyclonic circulation in 
waters 200 to 1,000 m (656.2 to 3,280.8 ft) deep. Species sighted 
regularly in these waters include Risso's, rough-toothed, spinner, 
striped, pantropical spotted, and Clymene dolphins, as well as short-
finned pilot, pygmy and dwarf sperm, sperm, Mesoplodon beaked, and 
unidentified beaked whales (Davis et al., 1998). In contrast, 
continental shelf waters (< 200 m deep) are primarily inhabited by two 
species: bottlenose and Atlantic spotted dolphins (Davis et al., 2000, 
2002; Mullin and Fulling, 2004). Bottlenose dolphins are also found in 
deeper waters (Baumgartner et al., 2001). The narrow continental shelf 
south of the Mississippi River delta (20 km [10.8 nmi] wide at its 
narrowest point) appears to be an important habitat for several 
cetacean species (Baumgartner et al., 2001; Davis et al., 2002). There 
appears to be a resident population of sperm whales within 100 km (54 
nmi) of the Mississippi River delta (Davis et al., 2002).
    Table 2 (below) presents information on the abundance, 
distribution, population status, conservation status, and population 
trend of the species of marine mammals that may occur in the proposed 
study area during April to May, 2013.

  Table 2--The Habitat, Regional Abundance, and Conservation Status of Marine Mammals That May Occur in or Near
               the Proposed Seismic Survey Area in the Deep Water of the Northwest Gulf of Mexico
                        [See text and Table 2 in USGS's application for further details.]
----------------------------------------------------------------------------------------------------------------
                                                   Population
           Species                 Habitat        estimate\3\       ESA \1\         MMPA \2\        Population
                                                   (minimum)                                        Trend \3\
----------------------------------------------------------------------------------------------------------------
                                                   Mysticetes
----------------------------------------------------------------------------------------------------------------
North Atlantic right whale     Coastal and      Extralimital...  EN...........  D..............  Increasing.
 (Eubalaena glacialis).         shelf.
Humpback whale (Megaptera      Pelagic,         Rare...........  EN...........  D..............  Increasing.
 novaeangliae).                 nearshore
                                waters, and
                                banks.
Minke whale (Balaenoptera      Pelagic and      Rare...........  NL...........  NC.............  No information
 acutorostrata).                coastal.                                                          available.
Bryde's whale (Balaenoptera    Pelagic and      15 (5)--         NL...........  NC.............  Unable to
 brydei).                       coastal.         Northern GOM                                     determine.
                                                 stock.
Sei whale (Balaenoptera        Primarily        Rare...........  EN...........  D..............  Unable to
 borealis).                     offshore,                                                         determine.
                                pelagic.
Fin whale (Balaenoptera        Continental      Rare...........  EN...........  D..............  Unable to
 physalus).                     slope, pelagic.                                                   determine.
Blue whale (Balaenoptera       Pelagic, shelf,  Extralimital...  EN...........  D..............  Unable to
 musculus).                     coastal.                                                          determine.
----------------------------------------------------------------------------------------------------------------
                                                   Odontocetes
----------------------------------------------------------------------------------------------------------------
Sperm whale (Physeter          Pelagic, deep    1,665 (1,409)--  EN...........  D..............  Unable to
 macrocephalus).                sea.             Northern GOM                                     determine.
                                                 stock.
Pygmy sperm whale (Kogia       Deep waters off  323 (203)--      NL...........  NC.............  Unable to
 breviceps).                    the shelf.       Northern GOM                                     determine.
                                                 stock.
Dwarf sperm whale (Kogia       Deep waters off  453 (340)--      NL...........  NC.............  Unable to
 sima).                         the shelf.       Northern GOM                                     determine.
                                                 stock.
Cuvier's beaked whale          Pelagic........  65 (39)--        NL...........  NC.............  Unable to
 (Ziphius cavirostris).                          Northern GOM                                     determine.
                                                 stock.
Mesoplodon beaked whale        Pelagic........  57 (24)--        NL...........  NC.............  Unable to
 (includes Blainville's                          Northern GOM                                     determine.
 beaked whale [M.                                stock.
 densirostris], Gervais'
 beaked whale [M. europaeus],
 and Sowerby's beaked whale
 [M. bidens].
Killer whale (Orcinus orca)..  Pelagic, shelf,  49 (28)--        NL...........  NC.............  Unable to
                                coastal.         Northern GOM                                     determine.
                                                 stock.
Short-finned pilot whale.....  Pelagic, shelf   716 (542)--      NL...........  NC.............  Unable to
(Globicephala macrorhynchus).   coastal.         Northern GOM                                     determine.
                                                 stock.
False killer whale (Pseudorca  Pelagic........  777 (501)--      NL...........  NC.............  Unable to
 crassidens).                                    Northern GOM                                     determine.
                                                 stock.
Melon-headed whale             Pelagic........  2,283 (1,293)--  NL...........  NC.............  Unable to
 (Peponocephala electra).                        Northern GOM                                     determine.
                                                 stock.
Pygmy killer whale (Feresa     Pelagic........  323 (203)--      NL...........  NC.............  Unable to
 attenuata).                                     Northern GOM                                     determine.
                                                 stock.
Risso's dolphin (Grampus       Deep water,      1,589 (1,271)--  NL...........  NC.............  Unable to
 griseus).                      seamounts.       Northern GOM                                     determine.
                                                 stock.

[[Page 11827]]

 
Bottlenose dolphin (Tursiops   Offshore,        NA (NA)--32      NL...........  NC.............  Unable to
 truncatus).                    inshore,         Northern GOM                   S--32 stocks      determine.
                                coastal,         Bay, Sound and                  inhabitiing
                                estuaries.       Estuary stocks.                 the bays,
                                                NA (NA)--                        sounds, and
                                                 Northern GOM                    estuaries
                                                 continental                     along GOM
                                                 shelf stock.                    coast, and GOM
                                                7,702 (6,551)--                  western
                                                 GOM eastern                     coastal stock.
                                                 coastal stock.
                                                2,473 (2,004)--
                                                 GOM northern
                                                 coastal stock.
                                                NA (NA)--GOM
                                                 western
                                                 coastal stock.
                                                3,708 (2,641)--
                                                 Northern GOM
                                                 oceanic stock.
Rough-toothed dolphin (Steno   Pelagic........  2,653 (1,890)--  NL...........  NC.............  Unable to
 bredanensis).                                   Northern GOM                                     determine.
                                                 stock.
Fraser's dolphin               Pelagic........  Unknown          NL...........  NC.............  Unable to
 (Lagenodelphis hosei).                          (Unkown)--Nort                                   determine.
                                                 hern GOM stock.
Striped dolphin (Stenella      Pelagic........  3,325 (2,266)--  NL...........  NC.............  Unable to
 coeruleoalba).                                  Northern GOM                                     determine.
                                                 stock.
Pantropical spotted dolphin    Pelagic........  34,067           NL...........  NC.............  Unable to
 (Stenella attenuata).                           (29,311)--Nort                                   determine.
                                                 hern GOM stock.
Atlantic spotted dolphin       Coastal and      Unknown          NL...........  NC.............  Unable to
 (Stenella frontalis).          pelagic.         (Unknown)--Nor                                   determine.
                                                 thern GOM
                                                 stock.
Spinner dolphin (Stenella      Mostly pelagic.  1,989 (1,356)--  NL...........  NC.............  Unable to
 longirostris).                                  Northern GOM                                     determine.
                                                 stock.
Clymene dolphin (Stenella      Pelagic........  6,575 (4,901)--  NL...........  NC.............  Unable to
 clymene).                                       Northern GOM                                     determine.
                                                 stock.
----------------------------------------------------------------------------------------------------------------
                                                    Sirenians
----------------------------------------------------------------------------------------------------------------
West Indian (Florida) manatee  Coastal,         3,802--U.S.      EN...........  D..............  Increasing or
 (Trichechus manatus            rivers, and      stock.                                           stable
 latrostris).                   estuaries.                                                        throughout
                                                                                                  much of
                                                                                                  Florida.
----------------------------------------------------------------------------------------------------------------
NA = Not available or not assessed.
\1\ U.S. Endangered Species Act: EN = Endangered, T = Threatened, DL = Delisted, NL = Not listed.
\2\ U.S. Marine Mammal Protection Act: D = Depleted, S = Strategic, NC = Not Classified.
\3\ NMFS Stock Assessment Reports.
\4\ USFWS Stock Assessment Reports.

    Refer to sections 3 and 4 of USGS's application for detailed 
information regarding the abundance and distribution, population 
status, and life history and behavior of these other marine mammal 
species and their occurrence in the proposed project area. The 
application also presents how USGS calculated the estimated densities 
for the marine mammals in the proposed survey area. NMFS has reviewed 
these data and determined them to be the best available scientific 
information for the purposes of the proposed IHA.

Potential Effects on Marine Mammals

    Acoustic stimuli generated by the operation of the airguns, which 
introduce sound into the marine environment, may have the potential to 
cause Level B harassment of marine mammals in the proposed survey area. 
The effects of sounds from airgun operations 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 proposed project would result in any 
cases of temporary or permanent hearing impairment, or any significant 
non-auditory physical or physiological effects. Based on the available 
data and studies described here, some behavioral disturbance is 
expected. A more comprehensive review of these issues can be found in 
the ``Programmatic Environmental Impact Statement/Overseas 
Environmental Impact Statement prepared for Marine Seismic Research 
that is funded by the National Science Foundation and conducted by the 
U.S. Geological Survey'' (NSF/USGS, 2011).

Tolerance

    Richardson et al. (1995) defines tolerance as the occurrence of 
marine mammals in areas where they are exposed to human activities or 
man-made noise. In many cases, tolerance develops by the animal 
habituating to the stimulus (i.e., the gradual waning of responses to a 
repeated or ongoing stimulus) (Richardson, et al., 1995; Thorpe, 1963), 
but because of ecological or physiological requirements, many marine 
animals may need to remain in

[[Page 11828]]

areas where they are exposed to chronic stimuli (Richardson, et al., 
1995).
    Numerous studies have shown that pulsed sounds from airguns are 
often readily detectable in the water at distances of many kilometers. 
Several studies have shown that marine mammals at distances more than a 
few kilometers from operating seismic vessels often show no apparent 
response. 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 the marine mammal group. Although various 
baleen whales and toothed whales, and (less frequently) pinnipeds have 
been shown to react behaviorally to airgun pulses under some 
conditions, at other times marine mammals of all three types have shown 
no overt reactions. The relative responsiveness of baleen and toothed 
whales are quite variable.

Masking

    The term masking refers to the inability of a subject to recognize 
the occurrence of an acoustic stimulus as a result of the interference 
of another acoustic stimulus (Clark et al., 2009). 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. Because of the intermittent nature and low duty cycle of 
seismic airgun pulses, animals can emit and receive sounds in the 
relatively quiet intervals between pulses. However, in some situations, 
reverberation occurs for much or the entire 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; and Dunn and Hernandez, 2009). 
However, Clark and Gagnon (2006) reported that fin whales in the North 
Atlantic Ocean went silent for an extended period starting soon after 
the onset of a seismic survey in the area. Similarly, 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 they continued calling in the presence of seismic 
pulses (Madsen et al., 2002; Tyack et al., 2003; Smultea et al., 2004; 
Holst et al., 2006; and Jochens et al., 2008). Dilorio and Clark (2009) 
found evidence of increased calling by blue whales during operations by 
a lower-energy seismic source (i.e., sparker). 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; and 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, NMFS expects the masking effects of seismic pulses to 
be minor, given the normally intermittent nature of seismic pulses.

Behavioral Disturbance

    Marine mammals may behaviorally react to sound when exposed to 
anthropogenic noise. Disturbance includes a variety of effects, 
including subtle to conspicuous changes in behavior, movement, and 
displacement. 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; Weilgart, 2007). These behavioral 
reactions are often shown as: Changing durations of surfacing and 
dives, number of blows per surfacing, or moving direction and/or speed; 
reduced/increased vocal activities; changing/cessation of certain 
behavioral activities (such as socializing or feeding); visible startle 
response or aggressive behavior (such as tail/fluke slapping or jaw 
clapping); avoidance of areas where noise sources are located; and/or 
flight responses. If a marine mammal does react briefly to an 
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).
    The biological significance of many of these behavioral 
disturbances is difficult to predict, especially if the detected 
disturbances appear minor. However, the consequences of behavioral 
modification could be expected to be biologically significant if the 
change affects growth, survival, and/or reproduction. Some of these 
significant behavioral modifications include:
     Change in diving/surfacing patterns (such as those thought 
to be causing beaked whale stranding due to exposure to military mid-
frequency tactical sonar);
     Habitat abandonment due to loss of desirable acoustic 
environment; and
     Cessation of feeding or social interaction.
    The onset of behavioral disturbance from anthropogenic noise 
depends on both external factors (characteristics of noise sources and 
their paths) and the receiving animals (hearing, motivation, 
experience, demography) and is also difficult to predict (Richardson et 
al., 1995; Southall et al., 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/or 
exposed to a particular level of sound. In most cases, this approach 
likely overestimates the numbers of marine mammals that would be 
affected in some biologically-important manner.
    Baleen Whales--Baleen whales generally tend to avoid operating 
airguns, but avoidance radii are quite variable (reviewed in Richardson 
et al., 1995; Gordon et al., 2004). 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, 
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 (Richardson, et al., 
1995). 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 to 170 dB re 1 [mu]Pa (rms) 
seem to cause obvious avoidance behavior in a substantial fraction of 
the animals exposed (Malme et al., 1986, 1988; Richardson et al., 
1995). In many areas, seismic pulses from large arrays of airguns 
diminish to those levels at distances ranging from 4 to 15 km (2.2 to 
8.1 nmi) from the source. A

[[Page 11829]]

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 have shown that some species of 
baleen whales, notably bowhead, gray, and humpback whales, at times, 
show strong avoidance at received levels lower than 160 to 170 dB re 1 
[mu]Pa (rms).
    Researchers have studied the responses of humpback whales to 
seismic surveys during migration, feeding during the summer months, 
breeding while offshore from Angola, and wintering offshore from 
Brazil. McCauley et al. (1998, 2000a) studied the responses of humpback 
whales off western Australia to a full-scale seismic survey with a 16 
airgun array (2,678 in\3\) and to a single airgun (20 in\3\) with 
source level of 227 dB re 1 [micro]Pa (p-p). In the 1998 study, they 
documented that avoidance reactions began at 5 to 8 km (2.7 to 4.3 nmi) 
from the array, and that those reactions kept most pods approximately 3 
to 4 km (1.6 to 2.2 nmi) from the operating seismic boat. In the 2000 
study, they noted localized displacement during migration of 4 to 5 km 
(2.2 to 2.7 nmi) by traveling pods and 7 to 12 km (3.8 to 6.5 nmi) 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 [mu]Pa (rms) for humpback pods containing females, and at 
the mean closest point of approach distance the received level was 143 
dB re 1 [mu]Pa (rms). The initial avoidance response generally occurred 
at distances of 5 to 8 km (2.7 to 4.3 nmi) from the airgun array and 2 
km (1.1 nmi) from the single airgun. However, some individual humpback 
whales, especially males, approached within distances of 100 to 400 m 
(328 to 1,312 ft), where the maximum received level was 179 dB re 1 
[mu]Pa (rms).
    Data collected by observers during several seismic surveys in the 
Northwest Atlantic showed that sighting rates of humpback whales were 
significantly greater during non-seismic periods compared with periods 
when a full array was operating (Moulton and Holst, 2010). In addition, 
humpback whales were more likely to swim away and less likely to swim 
towards a vessel during seismic vs. non-seismic periods (Moulton and 
Holst, 2010).
    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). Some humpbacks 
seemed ``startled'' at received levels of 150 to 169 dB re 1 [mu]Pa. 
Malme et al. (1985) concluded that there was no clear evidence of 
avoidance, despite the possibility of subtle effects, at received 
levels up to 172 dB re 1 [mu]Pa (rms). However, Moulton and Holst 
(2010) reported that humpback whales monitored during seismic surveys 
in the Northwest Atlantic had lower sighting rates and were most often 
seen swimming away from the vessel during seismic periods compared with 
periods when airguns were silent.
    Studies have 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).
    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 [mu]Pa on an (approximate) rms basis, and that 10 
percent of feeding whales interrupted feeding at received levels of 163 
dB re 1 [micro]Pa (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 seen in areas ensonified by airgun pulses 
(Stone, 2003; MacLean and Haley, 2004; Stone and Tasker, 2006), and 
calls from blue and fin whales have been localized in areas with airgun 
operations (e.g., McDonald et al., 1995; Dunn and Hernandez, 2009; 
Castellote et al., 2010). 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). Castellote et al. (2010) 
reported that singing fin whales in the Mediterranean moved away from 
an operating airgun array.
    Ship-based monitoring studies of baleen whales (including blue, 
fin, sei, minke, and humpback whales) in the Northwest Atlantic found 
that overall, this group had lower sighting rates during seismic vs. 
non-seismic periods (Moulton and Holst, 2010). Baleen whales as a group 
were also seen significantly farther from the vessel during seismic 
compared with non-seismic periods, and they were more often seen to be 
swimming away from the operating seismic vessel (Moulton and Holst, 
2010). Blue and minke whales were initially sighted significantly 
farther from the vessel during seismic operations compared to non-
seismic periods; the same trend was observed for fin whales (Moulton 
and Holst, 2010). Minke whales were most often observed to be swimming 
away from the vessel when seismic operations were underway (Moulton and 
Holst, 2010).
    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; Allen and Angliss, 2010). 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

[[Page 11830]]

numbers have increased notably, despite seismic exploration in their 
summer and autumn range for many years (Richardson et al., 1987; Allen 
and Angliss, 2010). The history of coexistence between seismic surveys 
and baleen whales suggests that brief exposures to sound pulses from 
any single seismic survey are unlikely to result in prolonged effects.
    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 have 
been reported for toothed whales. However, there are recent systematic 
studies on sperm whales (e.g., Gordon et al., 2006; Madsen et al., 
2006; Winsor and Mate, 2006; Jochens et al., 2008; Miller et al., 
2009). 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; Hauser et al., 2008; Holst and Smultea, 2008; 
Weir, 2008; Barkaszi et al., 2009; Richardson et al., 2009; Moulton and 
Holst, 2010).
    Seismic operators and PSOs 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; Richardson et 
al., 2009; Barkaszi et al., 2009; Moulton and Holst, 2010). 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; Barry et al., 2010; Moulton and Holst, 2010). In most cases, the 
avoidance radii for delphinids appear to be small, on the order of one 
km or less, and some individuals show no apparent avoidance.
    Captive bottlenose dolphins 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.
    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. However, controlled exposure experiments in the Gulf 
of Mexico indicate that foraging behavior was altered upon exposure to 
airgun sound (Jochens et al., 2008; Miller et al., 2009; Tyack, 2009).
    There are almost no specific data on the behavioral reactions of 
beaked whales to seismic surveys. However, some northern bottlenose 
whales (Hyperoodon ampullatus) remained in the general area and 
continued to produce high-frequency clicks when exposed to sound pulses 
from distant seismic surveys (Gosselin and Lawson, 2004; 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). Based on a 
single observation, Aguilar-Soto et al. (2006) suggested that foraging 
efficiency of Cuvier's beaked whales may be reduced by close approach 
of vessels. 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. In fact, Moulton and Holst 
(2010) reported 15 sightings of beaked whales during seismic studies in 
the Northwest Atlantic; seven of those sightings were made at times 
when at least one airgun was operating. There was little evidence to 
indicate that beaked whale behavior was affected by airgun operations; 
sighting rates and distances were similar during seismic and non-
seismic periods (Moulton and Holst, 2010).
    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 ``Stranding and Mortality'' section in this 
notice). These strandings are apparently 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. Seismic survey sounds are quite different 
from those of the sonar in operation during the above-cited incidents.
    Odontocete reactions to large arrays of airguns are variable and, 
at least for delphinids and Dall's porpoises, seem to be confined to a 
smaller radius than has been observed for the more responsive of some 
mysticetes. However, other data suggest that some odontocete species, 
including harbor porpoises, may be more responsive than might be 
expected given their poor low-frequency hearing. Reactions at longer 
distances may be particularly likely when sound propagation conditions 
are conducive to transmission of the higher frequency components of 
airgun sound to the animals' location (DeRuiter et al., 2006; Goold and 
Coates, 2006; Tyack et al., 2006; Potter et al., 2007).

Hearing Impairment and Other Physical Effects

    Exposure to high intensity sound for a sufficient duration may 
result in auditory effects such as a noise-induced threshold shift--an 
increase in the auditory threshold after exposure to noise (Finneran, 
Carder, Schlundt, and Ridgway, 2005). Factors that influence the amount 
of threshold shift include the amplitude, duration, frequency content, 
temporal pattern, and energy distribution of noise exposure. The 
magnitude of hearing threshold shift normally decreases over time 
following cessation of the noise exposure. The amount of threshold 
shift just after exposure is called the initial threshold shift. If the 
threshold shift eventually returns to zero (i.e., the threshold returns 
to the pre-exposure value), it is called temporary threshold shift 
(TTS) (Southall et al., 2007).
    Researchers have studied TTS in certain captive odontocetes and 
pinnipeds exposed to strong sounds (reviewed in Southall et al., 2007). 
However, there has been no specific documentation of TTS let alone 
permanent hearing damage, i.e., permanent threshold shift (PTS), in 
free-ranging marine mammals exposed to sequences of airgun pulses 
during realistic field conditions.
    Temporary Threshold Shift--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. At least in terrestrial mammals, 
TTS can last from minutes or hours to (in cases of strong TTS) days.

[[Page 11831]]

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). Table 1 (above) 
presents the estimated distances from the Pelican's airguns at which 
the received energy level (per pulse, flat-weighted) would be expected 
to be greater than or equal to 180 or 190 dB re 1 [micro]Pa (rms).
    To avoid the potential for injury, NMFS (1995, 2000) concluded that 
cetaceans should not be exposed to pulsed underwater noise at received 
levels exceeding 180 and 190 dB re 1 [mu]Pa (rms), respectively. NMFS 
believes that to avoid the potential for Level A harassment, cetaceans 
should not be exposed to pulsed underwater noise at received levels 
exceeding 180 and 190 dB re 1 [mu]Pa (rms), respectively. The 
established 180 and 190 dB (rms) criteria are not considered to be the 
levels above which TTS might occur. Rather, they are 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.
    For toothed whales, researchers have derived TTS information for 
odontocetes from studies on the bottlenose dolphin and beluga. The 
experiments show that exposure to a single impulse at a received level 
of 207 kPa (or 30 psi, p-p), which is equivalent to 228 dB re 1 Pa (p-
p), resulted in a 7 and 6 dB TTS in the beluga whale at 0.4 and 30 kHz, 
respectively. Thresholds returned to within 2 dB of the pre-exposure 
level within 4 minutes of the exposure (Finneran et al., 2002). For the 
one harbor porpoise tested, the received level of airgun sound that 
elicited onset of TTS was lower (Lucke et al., 2009). If these results 
from a single animal are representative, it is inappropriate to assume 
that onset of TTS occurs at similar received levels in all odontocetes 
(cf. Southall et al., 2007). Some cetaceans apparently can incur TTS at 
considerably lower sound exposures than are necessary to elicit TTS in 
the beluga or bottlenose dolphin.
    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 than those of odontocetes (Southall et 
al., 2007).
    Permanent Threshold Shift--When PTS occurs, there is physical 
damage to the sound receptors in the ear. In severe cases, there can be 
total or partial deafness, whereas 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 (e.g., Richardson et al., 1995, p. 372ff; 
Gedamke et al., 2008). Single or occasional occurrences of mild TTS are 
not indicative of permanent auditory damage, but repeated or (in some 
cases) single exposures to a level well above that causing TTS onset 
might elicit PTS.
    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 (Southall et al., 2007). PTS might occur at a 
received sound level at least several dBs above that inducing mild TTS 
if the animal were exposed to strong sound pulses with rapid rise 
times. 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).
    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.
    Stranding and Mortality--When a living or dead marine mammal swims 
or floats onto shore and becomes ``beached'' or incapable of returning 
to sea, the event is termed a ``stranding'' (Geraci et al., 1999; 
Perrin and Geraci, 2002; Geraci and Lounsbury, 2005; NMFS, 2007). The 
legal definition for a stranding under the MMPA is that ``(A) a marine 
mammal is dead and is (i) on a beach or shore of the United States; or 
(ii) in waters under the jurisdiction of the United States (including 
any navigable waters); or (B) a marine mammal is alive and is (i) on a 
beach or shore of the United States and is unable to return to the 
water; (ii) on a beach or shore of the United States and, although able 
to return to the water is in need of apparent medical attention; or 
(iii) in the waters under the jurisdiction of the United States 
(including any navigable waters), but is unable to return to its 
natural habitat under its own power or without assistance.''
    Marine mammals are known to strand for a variety of reasons, such 
as infectious agents, biotoxicosis, starvation, fishery interaction, 
ship strike, unusual oceanographic or weather events, sound exposure, 
or combinations of these stressors sustained concurrently or in series. 
However, the cause or causes of most strandings are unknown (Geraci et 
al., 1976; Eaton, 1979; Odell et al., 1980; Best, 1982). Numerous 
studies suggest that the physiology, behavior, habitat relationships, 
age, or condition of cetaceans may cause them to strand or might pre-
dispose them to strand when exposed to another phenomenon. These 
suggestions are consistent with the conclusions of numerous other 
studies that have demonstrated that combinations of dissimilar 
stressors commonly combine to kill an animal or dramatically reduce its 
fitness, even though one exposure without the other does not produce 
the same result (Chroussos, 2000; Creel, 2005; DeVries et al., 2003; 
Fair and Becker, 2000; Foley et al., 2001; Moberg, 2000; Relyea, 2005a, 
2005b; Romero, 2004; Sih et al., 2004).
    Strandings Associated with Military Active Sonar--Several sources 
have published lists of mass stranding events of cetaceans in an 
attempt to identify relationships between those stranding events and 
military active sonar (Hildebrand, 2004; IWC, 2005; Taylor et al., 
2004). For example, based on a review of stranding records between 1960 
and 1995, the International Whaling Commission (2005) identified ten 
mass stranding events and concluded that, out of eight stranding events 
reported from the mid-1980s to the summer of 2003, seven had been 
coincident with the use of mid-

[[Page 11832]]

frequency active sonar and most involved beaked whales.
    Over the past 12 years, there have been five stranding events 
coincident with military mid-frequency active sonar use in which 
exposure to sonar is believed to have been a contributing factor to 
strandings: Greece (1996); the Bahamas (2000); Madeira (2000); Canary 
Islands (2002); and Spain (2006). Refer to Cox et al. (2006) for a 
summary of common features shared by the strandings events in Greece 
(1996), Bahamas (2000), Madeira (2000), and Canary Islands (2002); and 
Fernandez et al., (2005) for an additional summary of the Canary 
Islands 2002 stranding event.
    Potential for Stranding from Seismic Surveys--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 in marine waters for commercial seismic surveys or (with rare 
exceptions) for seismic research. These methods 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 strandings of beaked whales with naval exercises 
involving mid-frequency active sonar (non-pulse sound) and, in one 
case, the co-occurrence of an L-DEO seismic survey (Malakoff, 2002; Cox 
et al., 2006), has raised the possibility that beaked whales exposed to 
strong ``pulsed'' sounds could also be susceptible to injury and/or 
behavioral reactions that can lead to stranding (e.g., Hildebrand, 
2005; Southall et al., 2007).
    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 (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.
Some of these mechanisms are unlikely to apply in the case of impulse 
sounds. However, there are 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. 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 one kHz. Typical military mid-frequency sonar emits non-
impulse sounds at frequencies of 2 to 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 expect that the same to marine mammals will result from 
military sonar and seismic surveys. 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; Fern[aacute]ndez 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 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 al., 
2004) were not well founded (IAGC, 2004; IWC, 2007). In September, 
2002, there was a stranding of two Cuvier's beaked whales in the Gulf 
of California, Mexico, when the L-DEO vessel R/V Maurice Ewing was 
operating a 20 airgun (8,490 in\3\) 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 mid-frequency 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, and
    (2) Differences between the sound sources operated by L-DEO and 
those involved in the naval exercises associated with strandings.
    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 effects (Gentry, 
2002) and direct noise-induced bubble formations (Crum et al., 2005) 
are implausible in the case of exposure to an impulsive broadband 
source like an airgun array. If seismic surveys disrupt diving patterns 
of deep-diving 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 non-
auditory 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.

Potential Effects of Other Acoustic Devices

Sub-bottom Profiler
    USGS may also operate a sub-bottom profiler from the source vessel 
during the proposed survey. A hull-mounted Knudsen 3.5 kHz sub-bottom 
profiler may be available since the Pelican is

[[Page 11833]]

considering such an installation in the coming months. Sounds from the 
sub-bottom profiler are very short pulses, occurring for 1 to 4 ms once 
every second. Most of the energy in the sound pulses emitted by the 
sub-bottom profiler is at 3.5 kHz, and the beam is directed downward. 
The sub-bottom profiler that may be used on the Pelican has a maximum 
source level of 204 dB re 1 [micro]Pa. 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 small--even for a sub-bottom 
profiler more powerful than that that may be on the Pelican. If the 
animal was in the area, it would have to pass the transducer at close 
range 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 the directionality 
of the signal and the brief period when an individual mammal is likely 
to be within its beam. Furthermore, in the case of most baleen whales, 
the sub-bottom profiler 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 sub-
bottom profiler are likely to be similar to those for other pulsed 
sources if received at the same levels. Therefore, behavioral responses 
are not expected unless marine mammals are very close to the source.
    Hearing Impairment and Other Physical Effects--It is unlikely that 
the sub-bottom profiler 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 sub-bottom profiler is 
usually operated simultaneously with other higher-power acoustic 
sources, including airguns. 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 sub-bottom 
profiler.
Acoustic Release Signals
    The acoustic release transponder used to communicate with the OBSs 
uses frequencies 9 to 13 kHz. These signals will be used 
intermittently. It is unlikely that the acoustic release signals would 
have a significant effect on marine mammals through masking, 
disturbance, or hearing impairment. Any effects likely would be 
negligible given the brief exposure at presumable low levels.
    The potential effects to marine mammals described in this section 
of the document do not take into consideration the proposed monitoring 
and mitigation measures described later in this document (see the 
``Proposed Mitigation'' and ``Proposed Monitoring and Reporting'' 
sections) which, as noted are designed to effect the least practicable 
impact on affected marine mammal species and stocks.

Vessel Movement and Collisions

    Vessel movement in the vicinity of marine mammals has the potential 
to result in either a behavioral response or a direct physical 
interaction. Both scenarios are discussed below in this section.
    Behavioral Responses to Vessel Movement--There are limited data 
concerning marine mammal behavioral responses to vessel traffic and 
vessel noise, and a lack of consensus among scientists with respect to 
what these responses mean or whether they result in short-term or long-
term adverse effects. In those cases where there is a busy shipping 
lane or where there is a large amount of vessel traffic, marine mammals 
(especially low frequency specialists) may experience acoustic masking 
(Hildebrand, 2005) if they are present in the area (e.g., killer whales 
in Puget Sound; Foote et al., 2004; Holt et al., 2008). In cases where 
vessels actively approach marine mammals (e.g., whale watching or 
dolphin watching boats), scientists have documented that animals 
exhibit altered behavior such as increased swimming speed, erratic 
movement, and active avoidance behavior (Bursk, 1983; Acevedo, 1991; 
Baker and MacGibbon, 1991; Trites and Bain, 2000; Williams et al., 
2002; Constantine et al., 2003), reduced blow interval (Ritcher et al., 
2003), disruption of normal social behaviors (Lusseau, 2003, 2006), and 
the shift of behavioral activities which may increase energetic costs 
(Constantine et al., 2003, 2004). A detailed review of marine mammal 
reactions to ships and boats is available in Richardson et al., (1995). 
For each of the marine mammal taxonomy groups, Richardson et al., 
(1995) provides the following assessment regarding reactions to vessel 
traffic:
    Toothed whales--``In summary, toothed whales sometimes show no 
avoidance reaction to vessels, or even approach them. However, 
avoidance can occur, especially in response to vessels of types used to 
chase or hunt the animals. This may cause temporary displacement, but 
we know of no clear evidence that toothed whales have abandoned 
significant parts of their range because of vessel traffic.''
    Baleen whales--``When baleen whales receive low-level sounds from 
distant or stationary vessels, the sounds often seem to be ignored. 
Some whales approach the sources of these sounds. When vessels approach 
whales slowly and non-aggressively, whales often exhibit slow and 
inconspicuous avoidance maneuvers. In response to strong or rapidly 
changing vessel noise, baleen whales often interrupt their normal 
behavior and swim rapidly away. Avoidance is especially strong when a 
boat heads directly toward the whale.''
    Behavioral responses to stimuli are complex and influenced to 
varying degrees by a number of factors, such as species, behavioral 
contexts, geographical regions, source characteristics (moving or 
stationary, speed, direction, etc.), prior experience of the animal and 
physical status of the animal. For example, studies have shown that 
beluga whales' reaction varied when exposed to vessel noise and 
traffic. In some cases, beluga whales exhibited rapid swimming from 
ice-breaking vessels up to 80 km (43.2 nmi) away and showed changes in 
surfacing, breathing, diving, and group composition in the Canadian 
high Arctic where vessel traffic is rare (Finley et al., 1990). In 
other cases, beluga whales were more tolerant of vessels, but responded 
differentially to certain vessels and operating characteristics by 
reducing their calling rates (especially older animals) in the St. 
Lawrence River where vessel traffic is common (Blane and Jaakson, 
1994). In Bristol Bay, Alaska, beluga whales continued to feed when 
surrounded by fishing vessels and resisted dispersal even when 
purposefully harassed (Fish and Vania, 1971).
    In reviewing more than 25 years of whale observation data, Watkins 
(1986) concluded that whale reactions to vessel traffic were ``modified 
by their previous experience and current activity: habituation often 
occurred rapidly, attention to other stimuli or preoccupation with 
other activities sometimes overcame their interest or wariness of 
stimuli.'' Watkins noticed that over the years of exposure to ships in 
the Cape Cod area, minke whales changed from frequent positive interest 
(e.g., approaching vessels) to generally uninterested reactions; fin 
whales changed from mostly negative (e.g., avoidance) to uninterested 
reactions; fin whales changed from mostly negative (e.g., avoidance) to 
uninterested

[[Page 11834]]

reactions; right whales apparently continued the same variety of 
responses (negative, uninterested, and positive responses) with little 
change; and humpbacks dramatically changed from mixed responses that 
were often negative to reactions that were often strongly positive. 
Watkins (1986) summarized that ``whales near shore, even in regions 
with low vessel traffic, generally have become less wary of boats and 
their noises, and they have appeared to be less easily disturbed than 
previously. In particular locations with intense shipping and repeated 
approaches by boats (such as the whale-watching areas of Stellwagen 
Bank), more and more whales had positive reactions to familiar vessels, 
and they also occasionally approached other boats and yachts in the 
same ways.''
    Although the radiated sound from the Pelican will be audible to 
marine mammals over a large distance, it is unlikely that marine 
mammals will respond behaviorally (in a manner that NMFS would consider 
harassment under the MMPA) to low-level distant shipping noise as the 
animals in the area are likely to be habituated to such noises (Nowacek 
et al., 2004). In light of these facts, NMFS does not expect the 
Pelican's movements to result in Level B harassment.
    Vessel Strike--Ship strikes of cetaceans can cause major wounds, 
which may lead to the death of the animal. An animal at the surface 
could be struck directly by a vessel, a surfacing animal could hit the 
bottom of a vessel, or an animal just below the surface could be cut by 
a vessel's propeller. The severity of injuries typically depends on the 
size and speed of the vessel (Knowlton and Kraus, 2001; Laist et al., 
2001; Vanderlaan and Taggart, 2007).
    The most vulnerable marine mammals are those that spend extended 
periods of time at the surface in order to restore oxygen levels within 
their tissues after deep dives (e.g., the sperm whale). In addition, 
some baleen whales, such as the North Atlantic right whale, seem 
generally unresponsive to vessel sound, making them more susceptible to 
vessel collisions (Nowacek et al., 2004). These species are primarily 
large, slow moving whales. Smaller marine mammals (e.g., bottlenose 
dolphin) move quickly through the water column and are often seen 
riding the bow wave of large ships. Marine mammal responses to vessels 
may include avoidance and changes in dive pattern (NRC, 2003).
    An examination of all known ship strikes from all shipping sources 
(civilian and military) indicates vessel speed is a principal factor in 
whether a vessel strike results in death (Knowlton and Kraus, 2001; 
Laist et al., 2001; Jensen and Silber, 2003; Vanderlaan and Taggart, 
2007). In assessing records in which vessel speed was known, Laist et 
al. (2001) found a direct relationship between the occurrence of a 
whale strike and the speed of the vessel involved in the collision. The 
authors concluded that most deaths occurred when a vessel was traveling 
in excess of 13 kts (24.1 km/hr, 14.9 mph).
    USGS's proposed operation of one source vessel for the proposed 
survey is relatively small in scale compared to the number of 
commercial ships transiting at higher speeds in the same areas on an 
annual basis. The probability of vessel and marine mammal interactions 
occurring during the proposed survey is unlikely due to the Pelican's 
slow operational speed, which is typically 4.5 kts (8.1 km/hr, 5 mph). 
Outside of seismic operations, the Pelican's cruising speed would be 
approximately 9.2 kts (17 km/hr, 10.6 mph), which is generally below 
the speed at which studies have noted reported increases of marine 
mammal injury or death (Laist et al., 2001).
    As a final point, the Pelican has a number of other advantages for 
avoiding ship strikes as compared to most commercial merchant vessels, 
including the following: the Pelican's bridge offers good visibility to 
visually monitor for marine mammal presence; PSOs posted during 
operations scan the ocean for marine mammals and must report visual 
alerts of marine mammal presence to crew; and the PSOs receive 
extensive training that covers the fundamentals of visual observing for 
marine mammals and information about marine mammals and their 
identification at sea.

Entanglement

    Entanglement can occur if wildlife becomes immobilized in survey 
lines, cables, nets, or other equipment that is moving through the 
water column. The proposed seismic survey would require towing 
approximately a single 450 m cable streamer. This large of an array 
carries the risk of entanglement for marine mammals. Wildlife, 
especially slow moving individuals, such as large whales, have a low 
probability of becoming entangled due to slow speed of the survey 
vessel and onboard monitoring efforts. In May, 2011, there was one 
recorded entanglement of an olive ridley sea turtle (Lepidochelys 
olivacea) in the R/V Marcus G. Langseth's barovanes after the 
conclusion of a seismic survey off Costa Rica. There have cases of 
baleen whales, mostly gray whales (Heyning, 1990), becoming entangled 
in fishing lines. The probability for entanglement of marine mammals is 
considered not significant because of the vessel speed and the 
monitoring efforts onboard the survey vessel.
    The potential effects to marine mammals described in this section 
of the document do not take into consideration the proposed monitoring 
and mitigation measures described later in this document (see the 
``Proposed Mitigation'' and ``Proposed Monitoring and Reporting'' 
sections) which, as noted are designed to effect the least practicable 
impact on affected marine mammal species and stocks.

Anticipated Effects on Marine Mammal Habitat

    The proposed seismic survey is not anticipated to have any 
permanent impact on habitats used by the marine mammals in the proposed 
survey area, including the food sources they use (i.e. fish and 
invertebrates). Additionally, no physical damage to any habitat is 
anticipated as a result of conducting the proposed seismic survey. 
While it is anticipated that the specified activity may result in 
marine mammals avoiding certain areas due to temporary ensonification, 
this impact to habitat is temporary and was considered in further 
detail earlier in this document, as behavioral modification. The main 
impact associated with the proposed activity will be temporarily 
elevated noise levels and the associated direct effects on marine 
mammals in any particular area of the approximately 445.4 km\2\ 
proposed project area, previously discussed in this notice. The next 
section discusses the potential impacts of anthropogenic sound sources 
on common marine mammal prey in the proposed survey area (i.e., fish 
and invertebrates).

Anticipated Effects on Fish

    One reason for the adoption of airguns as the standard energy 
source for marine seismic surveys is that, unlike explosives, they have 
not been associated with large-scale fish kills. However, existing 
information on the impacts of seismic surveys on marine fish and 
invertebrate populations is limited. There are three types of potential 
effects of exposure to seismic surveys: (1) Pathological, (2) 
physiological, and (3) behavioral. Pathological effects involve lethal 
and temporary or permanent sub-lethal injury. Physiological effects 
involve temporary and permanent primary and secondary stress responses, 
such as changes in levels of enzymes and proteins. Behavioral effects 
refer to temporary and (if they occur) permanent

[[Page 11835]]

changes in exhibited behavior (e.g., startle and avoidance behavior). 
The three categories are interrelated in complex ways. For example, it 
is possible that certain physiological and behavioral changes could 
potentially lead to an ultimate pathological effect on individuals 
(i.e., mortality).
    The specific received sound levels at which permanent adverse 
effects to fish potentially could occur are little studied and largely 
unknown. Furthermore, the available information on the impacts of 
seismic surveys on marine fish is from studies of individuals or 
portions of a population; there have been no studies at the population 
scale. The studies of individual fish have often been on caged fish 
that were exposed to airgun pulses in situations not representative of 
an actual seismic survey. Thus, available information provides limited 
insight on possible real-world effects at the ocean or population 
scale. This makes drawing conclusions about impacts on fish problematic 
because, ultimately, the most important issues concern effects on 
marine fish populations, their viability, and their availability to 
fisheries.
    Hastings and Popper (2005), Popper (2009), and Popper and Hastings 
(2009a,b) provided recent critical reviews of the known effects of 
sound on fish. The following sections provide a general synopsis of the 
available information on the effects of exposure to seismic and other 
anthropogenic sound as relevant to fish. The information comprises 
results from scientific studies of varying degrees of rigor plus some 
anecdotal information. Some of the data sources may have serious 
shortcomings in methods, analysis, interpretation, and reproducibility 
that must be considered when interpreting their results (see Hastings 
and Popper, 2005). Potential adverse effects of the program's sound 
sources on marine fish are noted.
    Pathological Effects--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. 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. As 
far as USGS and NMFS know, there are only two papers with proper 
experimental methods, controls, and careful pathological investigation 
implicating sounds produced by actual seismic survey airguns in causing 
adverse anatomical effects. One such study indicated anatomical damage, 
and the second indicated TTS in fish hearing. The anatomical case is 
McCauley et al. (2003), who found that exposure to airgun sound caused 
observable anatomical damage to the auditory maculae of pink snapper 
(Pagrus auratus). This damage in the ears had not been repaired in fish 
sacrificed and examined almost two months after exposure. On 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 (Coregonus 
nasus) exposed to five airgun shots were not significantly different 
from those of controls. 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 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 nine m in the former case and less than two m 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).
    Wardle et al. (2001) suggested that in water, acute injury and 
death of organisms exposed to seismic energy depends primarily on two 
features of the sound source: (1) the received peak pressure, and (2) 
the time required for the pressure to rise and decay. Generally, as 
received pressure increases, the period for the pressure to rise and 
decay decreases, and the chance of acute pathological effects 
increases. 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 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; 
Thomsen, 2002; Hassel et al., 2003; Popper et al., 2005; Boeger et al., 
2006).
    An experiment of the effects of a single 700 in\3\ airgun was 
conducted in Lake Meade, Nevada (USGS, 1999). The data were used in an 
Environmental Assessment of the effects of a marine reflection survey 
of the Lake Meade fault system by the National Park Service (Paulson et 
al., 1993, in USGS, 1999). The airgun was suspended 3.5 m (11.5 ft) 
above a school of threadfin shad in Lake Meade and was fired three 
successive times at a 30 second interval. Neither surface inspection 
nor diver observations of the water column and bottom found any dead 
fish.
    For a proposed seismic survey in Southern California, USGS (1999) 
conducted a review of the literature on the effects of airguns on fish 
and fisheries. They reported a 1991 study of the Bay Area Fault system 
from the continental shelf to the Sacramento River, using a 10 airgun 
(5,828 in\3\) array. Brezzina and Associates were hired by USGS to 
monitor the effects of the surveys and concluded that airgun operations 
were not responsible for the death of any of the fish carcasses 
observed. They also concluded that the airgun profiling did not appear 
to alter the feeding behavior of sea lions, seals, or pelicans observed 
feeding during the seismic surveys.
    Some studies have reported, some equivocally, that mortality of 
fish, fish eggs, or larvae can occur close to seismic sources 
(Kostyuchenko, 1973; Dalen and Knutsen, 1986; Booman et al., 1996; 
Dalen et al., 1996). Some of the reports claimed seismic effects from 
treatments quite different from actual seismic survey sounds or even 
reasonable surrogates. However, Payne et al. (2009) reported no 
statistical differences in mortality/morbidity between control and 
exposed groups of capelin eggs or monkfish larvae. Saetre and Ona 
(1996) applied a `worst-case scenario' mathematical model to 
investigate the effects of seismic energy on fish eggs and larvae. They 
concluded that mortality rates caused by exposure to seismic surveys 
are so low, as compared to natural mortality rates, that the impact of 
seismic surveying on recruitment to a fish stock must be regarded as 
insignificant.
    Physiological Effects--Physiological effects refer to cellular and/
or biochemical responses of fish to acoustic stress. Such stress 
potentially

[[Page 11836]]

could 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; Santulli et al., 1999; 
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.
    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 (e.g., 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.
    The Minerals Management Service (MMS, 2005) assessed the effects of 
a proposed seismic survey in Cook Inlet. The seismic survey proposed 
using three vessels, each towing two, four-airgun arrays ranging from 
1,500 to 2,500 in\3\. MMS noted that the impact to fish populations in 
the survey area and adjacent waters would likely be very low and 
temporary. MMS also concluded that seismic surveys may displace the 
pelagic fishes from the area temporarily when airguns are in use. 
However, fishes displaced and avoiding the airgun noise are likely to 
backfill the survey area in minutes to hours after cessation of seismic 
testing. Fishes not dispersing from the airgun noise (e.g., demersal 
species) may startle and move short distances to avoid airgun 
emissions.
    In general, any adverse effects on fish behavior or fisheries 
attributable to 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.

Anticipated Effects 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).
    The only information available on the impacts of seismic surveys on 
marine invertebrates involves studies of individuals; there have been 
no studies at the population scale. Thus, available information 
provides limited insight on possible real-world effects at the regional 
or ocean scale. The most important aspect of potential impacts concerns 
how exposure to seismic survey sound ultimately affects invertebrate 
populations and their viability, including availability to fisheries.
    Literature reviews of the effects of seismic and other underwater 
sound on invertebrates were provided by Moriyasu et al. (2004) and 
Payne et al. (2008). The following sections provide a synopsis of 
available information on the effects of exposure to seismic survey 
sound on species of decapod crustaceans and cephalopods, the two 
taxonomic groups of invertebrates on which most such studies have been 
conducted. The available information is from studies with variable 
degrees of scientific soundness and from anecdotal information. A more 
detailed review of the literature on the effects of seismic survey 
sound on invertebrates is provided in Appendix D of NSF/USGS's PEIS.
    Pathological Effects--In water, lethal and sub-lethal injury to 
organisms exposed to seismic survey sound appears to depend on at least 
two features of the sound source: (1) the received peak pressure; and 
(2) the time required for the pressure to rise and decay. Generally, as 
received pressure increases, the period for the pressure to rise and 
decay decreases, and the chance of acute pathological effects 
increases. 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, at most; 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 
the article provides little evidence to support this claim. Tenera 
Environmental (2011b) reported that Norris and Mohl (1983, summarized 
in Mariyasu et al., 2004) observed lethal effects in squid (Loligo 
vulgaris) at levels of 246 to 252 dB after 3 to 11 minutes.
    Andre et al. (2011) exposed four species of cephalopods (Loligo 
vulgaris, Sepia officinalis, Octopus vulgaris, and Ilex coindetii), 
primarily cuttlefish, to two hours of continuous 50 to 400 Hz 
sinusoidal wave sweeps at 157+/-5 dB re 1 [micro]Pa while captive in 
relatively small tanks. They reported morphological and ultrastructural 
evidence of massive acoustic trauma (i.e., permanent and substantial 
alterations [lesions] of statocyst sensory hair cells) to the exposed 
animals that increased in severity with time, suggesting that 
cephalopods are particularly sensitive to low frequency sound. The 
received SPL was reported as 157+/-5 dB re 1 [micro]Pa, with peak 
levels at 175 dB re 1 [micro]Pa. As in the McCauley et al. (2003) paper 
on sensory hair cell damage in pink snapper as a result of exposure to 
seismic sound, the cephalopods were subjected to higher sound levels 
than they would be under natural conditions, and they were unable to 
swim away from the sound source.
    Physiological Effects--Physiological effects refer mainly to 
biochemical responses by marine invertebrates to acoustic stress. Such 
stress potentially could affect invertebrate populations by increasing 
mortality or reducing reproductive success. Primary and secondary 
stress responses (i.e., changes in haemolymph levels of enzymes, 
proteins, etc.) of crustaceans have been noted several days or months 
after exposure to seismic survey sounds (Payne et al., 2007). It was 
noted however, than no behavioral impacts

[[Page 11837]]

were exhibited by crustaceans (Christian et al., 2003, 2004; DFO, 
2004). The periods necessary for these biochemical changes to return to 
normal are variable and depend on numerous aspects of the biology of 
the species and of the sound stimulus.
    Behavioral Effects--There is increasing interest in assessing the 
possible direct and indirect effects of seismic and other sounds on 
invertebrate behavior, particularly in relation to the consequences for 
fisheries. Changes in behavior could potentially affect such aspects as 
reproductive success, distribution, susceptibility to predation, and 
catchability by fisheries. Studies investigating the possible 
behavioral effects of exposure to seismic survey sound on crustaceans 
and cephalopods have been conducted on both uncaged and caged animals. 
In some cases, invertebrates exhibited startle responses (e.g., squid 
in McCauley et al., 2000a,b). In other cases, no behavioral impacts 
were noted (e.g., crustaceans in Christian et al., 2003, 2004; DFO 
2004). There have been anecdotal reports of reduced catch rates of 
shrimp shortly after exposure to seismic surveys; however, other 
studies have not observed any significant changes in shrimp catch rate 
(Andriguetto-Filho et al., 2005). Similarly, Parry and Gason (2006) did 
not find any evidence that lobster catch rates were affected by seismic 
surveys. Any adverse effects on crustacean and cephalopod behavior or 
fisheries attributable to seismic survey sound depend on the species in 
question and the nature of the fishery (season, duration, fishing 
method).
    OBS Deployment--A total of approximately 25 OBSs will be deployed 
during the proposed survey. OBSs operated by the U.S. National OBS 
Instrument Pool will be used during the proposed cruise. This type of 
OBS has a height of approximately 1 m (3.3 ft) and a maximum diameter 
of 50 cm (19.7 in). The anchor is a steel plate weighing approximately 
40 kg (88.2 lb) with dimensions approximately 30 x 30 x 8 cm (11.8 x 
11.8 x 3.1 in). Once an OBS is ready to be retrieved, an acoustic 
release transponder interrogates the instrument at a frequency of 9 to 
11 kHz, and a response is received at a frequency of 9 to 13 kHz. The 
burn-wire release assembly is then activated, and the instrument is 
released from the anchor to float to the surface. OBS anchors will be 
left behind upon equipment recovery. Although OBS placement will 
disrupt a very small area of the seafloor habitat and could disturb 
invertebrates, the impacts are expected to be localized and transitory.

Proposed Mitigation

    In order to issue an Incidental Take Authorization (ITA) under 
section 101(a)(5)(D) of the MMPA, NMFS must set forth the permissible 
methods of taking pursuant to such activity, and other means of 
effecting the least practicable impact on such species or stock and its 
habitat, paying particular attention to rookeries, mating grounds, and 
areas of similar significance, and the availability of such species or 
stock for taking for certain subsistence uses.
    USGS reviewed the following source documents and have incorporated 
a suite of appropriate mitigation measures into their project 
description.
    (1) Protocols used during previous NSF and USGS-funded seismic 
research cruises as approved by NMFS and detailed in the recently 
completed Final Programmatic Environmental Impact Statement/Overseas 
Environmental Impact Statement for Marine Seismic Research Funded by 
the National Science Foundation or Conducted by the U.S. Geological 
Survey;
    (2) Previous IHA applications and IHAs approved and authorized by 
NMFS; and
    (3) Recommended best practices in Richardson et al. (1995), Pierson 
et al. (1998), and Weir and Dolman, (2007).
    To reduce the potential for disturbance from acoustic stimuli 
associated with the activities, USGS and/or its designees have proposed 
to implement the following mitigation measures for marine mammals:
    (1) Proposed exclusion zones around the sound source;
    (2) Speed and course alterations;
    (3) Shut-down procedures; and
    (4) Ramp-up procedures.
    Proposed Exclusion Zones--USGS use radii to designate exclusion and 
buffer zones and to estimate take for marine mammals. Table 1 
(presented earlier in this document) shows the distances at which one 
would expect to receive three sound levels (160, 180, and 190 dB) from 
the 18 airgun array and a single airgun. The 180 dB and 190 dB level 
shut-down criteria are applicable to cetaceans and pinnipeds, 
respectively, as specified by NMFS (2000). USGS used these levels to 
establish the exclusion and buffer zones.
    Received sound levels have been modeled by L-DEO for a number of 
airgun configurations, including two 105 in\3\ GI airguns, in relation 
to distance and direction from the airguns (see Figure 2 of the IHA 
application). The model does not allow for bottom interactions, and is 
most directly applicable to deep water. Based on the modeling, 
estimates of the maximum distances from the GI airguns where sound 
levels are predicted to be 190, 180, and 160 dB re 1 [micro]Pa (rms) in 
deep water were determined (see Table 1 above).
    Empirical data concerning the 190, 180, and 160 dB (rms) distances 
were acquired for various airgun arrays based on measurements during 
the acoustic verification studies conducted by L-DEO in the northern 
GOM in 2003 (Tolstoy et al., 2004) and 2007 to 2008 (Tolstoy et al., 
2009). Results of the 36 airgun array are not relevant for the 2 GI 
airguns to be used in the proposed survey. The empirical data for the 
6, 10, 12, and 20 airgun arrays indicate that, for deep water, the L-
DEO model tends to overestimate the received sound levels at a given 
distance (Tolstoy et al., 2004). Measurements were not made for the two 
GI airgun array in deep water; however, USGS propose to use the safety 
radii predicted by L-DEO's model for the proposed GI airgun operations 
in deep water, although they are likely conservative given the 
empirical results for the other arrays. The 180 and 190 dB (rms) radii 
are shut-down criteria applicable to cetaceans and pinnipeds, 
respectively, as specified by NMFS (2000); these levels were used to 
establish exclusion zones. Therefore, the assumed 180 and 190 dB radii 
are 70 m (229.7 ft) and 20 m (65.6 ft), respectively. If the PSO 
detects a marine mammal(s) within or about to enter the appropriate 
exclusion zone, the airguns will be shut-down immediately.
    Speed and Course Alterations--If a marine mammal is detected 
outside the exclusion zone and, based on its position and direction of 
travel (relative motion), is likely to enter the exclusion zone, 
changes of the vessel's speed and/or direct course will be considered 
if this does not compromise operational safety. This would be done if 
operationally practicable while minimizing the effect on the planned 
science objectives. For marine seismic surveys towing large streamer 
arrays, however, course alterations are not typically implemented due 
to the vessel's limited maneuverability. After any such speed and/or 
course alteration is begun, the marine mammal activities and movements 
relative to the seismic vessel will be closely monitored to ensure that 
the marine mammal does not approach within the exclusion zone. If the 
marine mammal appears likely to enter the exclusion zone, further 
mitigation actions will be taken, including further course alterations 
and/or shut-down of the airgun(s). Typically, during seismic 
operations, the source vessel is unable to change speed or course, and 
one or more alternative

[[Page 11838]]

mitigation measures will need to be implemented.
    Shut-down Procedures--USGS will shut-down the operating airgun(s) 
if a marine mammal is detected outside the exclusion zone for the 
airgun(s), and if the vessel's speed and/or course cannot be changed to 
avoid having the animal enter the exclusion zone, the seismic source 
will be shut-down before the animal is within the exclusion zone. 
Likewise, if a marine mammal is already within the exclusion zone when 
first detected, the seismic source will be shut down immediately.
    Following a shut-down, USGS will not resume airgun activity until 
the marine mammal has cleared the exclusion zone. USGS will consider 
the animal to have cleared the exclusion zone if:
     A PSO has visually observed the animal leave the exclusion 
zone, or
     A PSO has not sighted the animal within the exclusion zone 
for 15 minutes for species with shorter dive durations (i.e., small 
odontocetes or pinnipeds), or 30 minutes for species with longer dive 
durations (i.e., mysticetes and large odontocetes, including sperm, 
killer, and beaked whales).
    Although power-down procedures are often standard operating 
practice for seismic surveys, they are not proposed to be used during 
this planned seismic survey because powering-down from two airguns to 
one airgun would make only a small difference in the exclusion 
zone(s)--but probably not enough to allow continued one-airgun 
operations if a marine mammal came within the exclusion zone for two 
airguns.
    Ramp-up Procedures--Ramp-up of an airgun array provides a gradual 
increase in sound levels, and involves a step-wise increase in the 
number and total volume of airguns firing until the full volume of the 
airgun array is achieved. The purpose of a ramp-up is to ``warn'' 
marine mammals in the vicinity of the airguns and to provide the time 
for them to leave the area avoiding any potential injury or impairment 
of their hearing abilities. USGS will follow a ramp-up procedure when 
the airgun array begins operating after a specified period without 
airgun operations or when a shut-down shut down has exceeded that 
period. USGS proposes that, for the present cruise, this period would 
be approximately 15 minutes. L-DEO and Scripps Institution of 
Oceanography (SIO) has used similar periods (approximately 15 minutes) 
during previous low-energy seismic surveys.
    Ramp-up will begin with a single GI airgun (105 in\3\). The second 
GI airgun (105 in\3\) will be added after 5 minutes. During ramp-up, 
the PSOs will monitor the exclusion zone, and if marine mammals are 
sighted, a shut-down will be implemented as though both GI airguns were 
operational.
    If the complete exclusion zone has not been visible for at least 30 
minutes prior to the start of operations in either daylight or 
nighttime, USGS will not commence the ramp-up. 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 exclusion zone for that array will not be visible during those 
conditions. If one airgun has operated, ramp-up to full power will be 
permissible at night or in poor visibility, on the assumption that 
marine mammals will be alerted to the approaching seismic vessel by the 
sounds from the single airgun and could move away if they choose. A 
ramp-up from a shut-down may occur at night, by only where the 
exclusion zone is small enough to be visible. USGS will not initiate a 
ramp-up of the airguns if a marine mammal is sighted within or near the 
applicable exclusion zones during the day or close to the vessel at 
night.
    NMFS has carefully evaluated the applicant's proposed mitigation 
measures and has considered a range of other measures in the context of 
ensuring that NMFS prescribes the means of effecting the least 
practicable adverse impact on the affected marine mammal species and 
stocks and their habitat. NMFS's evaluation of potential measures 
included consideration of the following factors in relation to one 
another:
    (1) The manner in which, and the degree to which, the successful 
implementation of the measure is expected to minimize adverse impacts 
to marine mammals;
    (2) The proven or likely efficacy of the specific measure to 
minimize adverse impacts as planned; and
    (3) The practicability of the measure for applicant implementation.
    Based on NMFS's evaluation of the applicant's proposed measures, as 
well as other measures considered by NMFS or recommended by the public, 
NMFS has preliminarily determined that the proposed mitigation measures 
provide the means of effecting the least practicable adverse impacts on 
marine mammal species or stocks and their habitat, paying particular 
attention to rookeries, mating grounds, and areas of similar 
significance.

Proposed Monitoring and Reporting

    In order to issue an ITA for an activity, section 101(a)(5)(D) of 
the MMPA states that NMFS must set forth ``requirements pertaining to 
the monitoring and reporting of such taking.'' The MMPA implementing 
regulations at 50 CFR 216.104(a)(13) indicate that requests for IHAs 
must include the suggested means of accomplishing the necessary 
monitoring and reporting that will result in increased knowledge of the 
species and of the level of taking or impacts on populations of marine 
mammals that are expected to be present in the action area.

Proposed Monitoring

    USGS propose to sponsor marine mammal monitoring during the 
proposed 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 and PG&E's 
proposed ``Monitoring Plan'' is described below this section. USGS 
understand 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. USGS are prepared to discuss coordination of their 
monitoring program with any related work that might be done by other 
groups insofar as this is practical and desirable.

Vessel-Based Visual Monitoring

    PSOs will be based aboard the seismic source vessel and will watch 
for marine mammals near the vessel during daytime airgun operations and 
during any ramp-ups of the airguns at night. PSOs will also watch for 
marine mammals near the seismic vessel for at least 30 minutes prior to 
the start of airgun operations after an extended shut-down (i.e., 
greater than approximately 15 minutes for this proposed cruise). When 
feasible, PSOs will conduct observations during daytime periods when 
the seismic system is not operating for comparison of sighting rates 
and behavior with and without airgun operations and between acquisition 
periods. Based on PSO observations, the airguns will be shut-down when 
marine mammals are observed within or about to enter a designated 
exclusion zone. The exclusion zone is a region in which a possibility 
exists of adverse effects on animal hearing or other physical effects.
    During seismic operations in the deep water of the northwestern 
GOM, at least three PSOs will be based aboard the Pelican. USGS will 
appoint the PSOs

[[Page 11839]]

with NMFS's concurrence. Observations will take place during ongoing 
daytime operations and nighttime ramp-ups of the airguns. During the 
majority of seismic operations, at least one PSO will be on duty from 
observation platforms (i.e., the best available vantage point on the 
source vessel) to monitor marine mammals near the seismic vessel. 
PSO(s) will be on duty in shifts no longer than 4 hours in duration. 
Other crew will also be instructed to assist in detecting marine 
mammals and implementing mitigation requirements (if practical). Before 
the start of the seismic survey, the crew will be given additional 
instruction on how to do so.
    The Pelican is a suitable platform for marine mammal observations 
and will serve as the platform from which PSOs will watch for marine 
mammals before and during seismic operations. Two locations are likely 
as observation stations onboard the Pelican. When stationed on the aft 
control station on the upper deck (01 level), the eye level will be 
approximately 12 m (39.3 ft) above sea level, and the PSO will have an 
approximately 210[deg] view aft of the vessel centered on the seismic 
source location. At the bridge station, the eye level will be 
approximately 13 m (42.7 ft) above sea level, and the location will 
offer a full 360[deg] view around the entire vessel. During daytime, 
the PSO(s) will scan the area around the vessel systematically with 
reticle binoculars (e.g., 7 x 50 Fujinon), optical range-finders (to 
assist with distance estimation), and the naked eye. At night, night-
vision equipment will be available. The optical range-finders are 
useful in training observers to estimate distances visually, but are 
generally not useful in measuring distances to animals directly. 
Estimating distances is done primarily with the reticles in the 
binoculars. The PSO(s) will be in wireless communication with ship's 
officers on the bridge and scientists in the vessel's operations 
laboratory, so they can advise promptly of the need for avoidance 
maneuvers or a shut-down of the seismic source.
    When marine mammals are detected within or about to enter the 
designated exclusion zone, the airguns will immediately be shut-down if 
necessary. The PSO(s) will continue to maintain watch to determine when 
the animal(s) are outside the exclusion zone by visual confirmation. 
Airgun operations will not resume until the animal is confirmed to have 
left the exclusion zone, or if not observed after 15 minutes for 
species with shorter dive durations (small odontocetes) or 30 minutes 
for species with longer dive durations (mysticetes and large 
odontocetes, including sperm, pygmy sperm, dwarf sperm, killer, and 
beaked whales).

PSO Data and Documentation

    PSOs will record data to estimate the numbers of marine mammals 
exposed to various received sound levels and to document apparent 
disturbance reactions or lack thereof. Data will be used to estimate 
numbers of animals potentially ``taken'' by harassment (as defined in 
the MMPA). They will also provide information needed to order a shut-
down of the airguns when a marine mammal is within or near the 
exclusion zone. Observations will also be made during daytime periods 
when the Pelican is underway without seismic operations (i.e., 
transits, to, from, and through the study area) to collect baseline 
biological data.
    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 seismic source or vessel (e.g., none, 
avoidance, approach, paralleling, etc.), and behavioral pace.
    2. Time, location, heading, speed, activity of the vessel, sea 
state, wind force, visibility, and sun glare.
    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, as well as information regarding ramp-ups or 
shut-downs will be recorded in a standardized format. The data accuracy 
will be verified by the PSOs at sea, and preliminary reports will be 
prepared during the field program and summaries forwarded to the 
operating institution's shore facility weekly or more frequently.
    Results from the vessel-based observations will provide the 
following information:
    1. The basis for real-time mitigation (airgun shut-down).
    2. Information needed to estimate the number of marine mammals 
potentially taken by harassment, which must be reported to NMFS.
    3. Data on the occurrence, distribution, and activities of marine 
mammals in the area where the seismic study is conducted.
    4. Information to compare the distance and distribution of marine 
mammals relative to the source vessel at times with and without seismic 
activity.
    5. Data on the behavior and movement patterns of marine mammals 
seen at times with and without seismic activity.
    USGS will submit a comprehensive 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 near the 
operations. The report submitted to NMFS 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 sightings (i.e., dates, times, 
locations, activities, and associated seismic survey activities). The 
report will minimally include:
     Summaries of monitoring effort--total hours, total 
distances, and distribution of marine mammals through the study period 
accounting for sea state and other factors affecting visibility and 
detectability of marine mammals;
     Analyses of the effects of various factors influencing 
detectability of marine mammals including sea state, number of PSOs, 
and fog/glare;
     Species composition, occurrence, and distribution of 
marine mammals sightings including date, water depth, numbers, age/
size/gender, and group sizes; and analyses of the effects of seismic 
operations;
     Sighting rates of marine mammals during periods with and 
without airgun activities (and other variables that could affect 
detectability);
     Initial sighting distances versus airgun activity state;
     Closest point of approach versus airgun activity state;
     Observed behaviors and types of movements versus airgun 
activity state;
     Numbers of sightings/individuals seen versus airgun 
activity state; and
     Distribution around the source vessel versus airgun 
activity state.
    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. After the report is considered final, it 
will be publicly available on the NMFS Web site at: https://www.nmfs.noaa.gov/pr/permits/incidental.htm#iha.
    In the unanticipated event that the specified activity clearly 
causes the take of a marine mammal in a manner prohibited by this IHA, 
such as an injury (Level A harassment), serious injury or mortality 
(e.g., ship-strike, gear interaction, and/or entanglement), USGS will 
immediately cease the specified activities and immediately report the 
incident to the Chief of the Permits and Conservation Division,

[[Page 11840]]

Office of Protected Resources, NMFS at 301-427-8401 and/or by email to 
Jolie.Harrison@noaa.gov and Howard.Goldstein@noaa.gov, and the NMFS 
Southeast Region Marine Mammal Stranding Network at 877-433-8299 
(Blair.Mase@noaa.gov and Erin.Fougeres@noaa.gov) or the Florida Marine 
Mammal Stranding Hotline at 888-404-3922. The report must include the 
following information:
     Time, date, and location (latitude/longitude) of the 
incident;
     Name and type of vessel involved;
     Vessel's speed during and leading up to the incident;
     Description of the incident;
     Status of all sound source use in the 24 hours preceding 
the incident;
     Water depth;
     Environmental conditions (e.g., wind speed and direction, 
Beaufort sea state, cloud cover, and visibility);
     Description of all marine mammal observations in the 24 
hours preceding the incident;
     Species identification or description of the animal(s) 
involved;
     Fate of the animal(s); and
     Photographs or video footage of the animal(s) (if 
equipment is available).
    Activities shall not resume until NMFS is able to review the 
circumstances of the prohibited take. NMFS shall work with USGS to 
determine what is necessary to minimize the likelihood of further 
prohibited take and ensure MMPA compliance. USGS may not resume their 
activities until notified by NMFS via letter or email, or telephone.
    In the event that USGS discovers an injured or dead marine mammal, 
and the lead PSO determines that the cause of the injury or death is 
unknown and the death is relatively recent (i.e., in less than a 
moderate state of decomposition as described in the next paragraph), 
USGS will immediately report the incident to the Chief of the Permits 
and Conservation Division, Office of Protected Resources, NMFS, at 301-
427-8401, and/or by email to Jolie.Harrison@noaa.gov and 
Howard.Goldstein@noaa.gov, and the NMFS Southeast Region Marine Mammal 
Stranding Network (877-433-8299) and/or by email to the Southeast 
Regional Stranding Coordinator (Blair.Mase@noaa.gov) and Southeast 
Regional Stranding Program Administrator (Erin.Fougeres@noaa.gov). The 
report must include the same information identified in the paragraph 
above. Activities may continue while NMFS reviews the circumstances of 
the incident. NMFS will work with USGS to determine whether 
modifications in the activities are appropriate.
    In the event that USGS discovers an injured or dead marine mammal, 
and the lead PSO determines that the injury or death is not associated 
with or related to the activities authorized in the IHA (e.g., 
previously wounded animal, carcass with moderate or advanced 
decomposition, or scavenger damage), USGS will report the incident to 
the Chief of the Permits and Conservation Division, Office of Protected 
Resources, NMFS, at 301-427-8401, and/or by email to 
Jolie.Harrison@noaa.gov and Howard.Goldstein@noaa.gov, and the NMFS 
Southeast Regional Marine Mammal Stranding Network (877-433-8299), and/
or by email to the Southeast Regional Stranding Coordinator 
(Blair.Mase@noaa.gov) and Southeast Regional Stranding Program 
Administrator (Erin.Fougeres@noaa.gov), within 24 hours of discovery. 
USGS will provide photographs or video footage (if available) or other 
documentation of the stranded animal sighting to NMFS and the Marine 
Mammal Stranding Network. Activities may continue while NMFS reviews 
the circumstances of the incident.

Estimated Take by Incidental 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 [Level A harassment]; or (ii) has the 
potential to disturb a marine mammal or marine mammal stock in the wild 
by causing disruption of behavioral patterns, including, but not 
limited to, migration, breathing, nursing, breeding, feeding, or 
sheltering [Level B harassment].
    Level B harassment is anticipated and proposed to be authorized as 
a result of the proposed low-energy marine seismic survey in the deep 
water of the northwestern GOM. Acoustic stimuli (i.e., increased 
underwater sound) generated during the operation of the seismic airgun 
array are expected to result in the behavioral disturbance of some 
marine mammals. There is no evidence that the planned activities could 
result in injury, serious injury, or mortality for which USGS seeks the 
IHA. The required mitigation and monitoring measures will minimize any 
potential risk for injury, serious injury, or mortality.
    The following sections describe USGS's methods to estimate take by 
incidental harassment and present the applicant's estimates of the 
numbers of marine mammals that could be affected during the proposed 
seismic program in the deep water of the northwestern GOM. The 
estimates are based on a consideration of the number of marine mammals 
that could be harassed by approximately 1,480 km (799.1 nmi) of seismic 
operations with the two GI airgun array to be used. The size of the 
proposed 2D seismic survey area in 2013 is approximately 356 km\2\ 
(103.8 nmi\2\) (approximately 445 km\2\ [129.7 nmi\2\]), as depicted in 
Figure 1 of the IHA application.
    USGS assumes that, during simultaneous operations of the airgun 
array and the other sources, any marine mammals close enough to be 
affected by the sub-bottom profiler 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 
sub-bottom profiler given their characteristics (e.g., narrow, 
downward-directed beam) and other considerations described previously. 
Such reactions are not considered to constitute ``taking'' (NMFS, 
2001). Therefore, USGS provides no additional allowance for animals 
that could be affected by sound sources other than airguns.
    USGS used spring densities reported in Table A-9 of Appendix A of 
the Bureau of Ocean Energy Management, Regulation and Enforcement's 
(BOEMRE, now the Bureau of Ocean Energy Management [BOEM] and Bureau of 
Safety and Environmental Enforcement [BSEE]) ``Request for incidental 
take regulations governing seismic surveys on the Outer Continental 
Shelf (OCS) of the Gulf of Mexico'' (BOEMRE, 2011). Those densities 
were calculated from the U.S. Navy's ``OPAREA Density Estimates'' 
(NODE) database (DoN, 2007b). The density estimates are based on the 
NMFS-Southeast Fisheries Science Center (SEFSC) shipboard surveys 
conducted from 1994 to 2006 and were derived using a model-based 
approach and statistical analysis of the existing survey data. The 
outputs from the NODE database are four seasonal surface density plots 
of the GOM for each of the marine mammal species occurring there. Each 
of the density plots was overlaid with the boundaries of the 9 acoustic 
model regions used in Appendix A of BOEMRE (2011). USGS used the 
densities for Acoustic Model Region 8, which corresponds roughly with 
the deep waters (greater than 1,000 m) of the BOEMRE GOM Central 
Planning

[[Page 11841]]

Area, and includes the GC955 and WR313 study sites.

 Table 3--Estimated Densities and Possible Number of Marine Mammal Species That Might Be Exposed to Greater Than
 or Equal to 160 dB During USGS's Proposed Seismic Survey (Ensonified Area 445.4 km\2\) in the Deep Water of the
                                      Northwestern GOM, April to May, 2013
----------------------------------------------------------------------------------------------------------------
                                                          Calculated
                                                          take (i.e.,
                                                           estimated
                                          Density \a\      number of     Approximate percentage   Requested take
                Species                   (/     individuals      of best population      authorization
                                         1,000 km\2\)     exposed to        estimate of stock           \3\
                                                         sound levels     (calculated take) \2\
                                                        >= 160 dB re 1
                                                        [micro]Pa) \1\
----------------------------------------------------------------------------------------------------------------
                                                   Mysticetes
----------------------------------------------------------------------------------------------------------------
North Atlantic right whale............              NA              NA  NA......................              NA
Humpback whale........................              NA              NA  NA......................              NA
Minke whale...........................              NA              NA  NA......................              NA
Bryde's whale.........................             0.1               0  0.......................               0
Sei whale.............................              NA              NA  NA......................              NA
Fin whale.............................              NA              NA  NA......................              NA
Blue whale............................              NA              NA  NA......................              NA
----------------------------------------------------------------------------------------------------------------
                                                   Odontocetes
----------------------------------------------------------------------------------------------------------------
Sperm whale...........................             4.9               2  0.18 (0.12).............               3
Kogia spp. (Pygmy and dwarf sperm                  2.1               1  0.62 (0.31)--Pygmy sperm               2
 whale).                                                                 whale.
                                                                        0.44 (0.22)--Dwarf sperm
                                                                         whale.
Small (Mesoplodon and Cuvier's) beaked             3.7               2  3.51 (3.51)--Mesoplodon                2
 whale.                                                                  beaked whale.
                                                                        3.1 (3.1)--Cuvier's
                                                                         beaked whale.
Killer whale..........................            0.40               0  0.......................               0
Short-finned pilot whale..............             6.3               3  2.65 (0.42).............              19
False killer whale....................             2.7               1  4.63 (0.13).............              36
Melon-headed whale....................             9.1               4  5.17 (0.18).............             118
Pygmy killer whale....................             1.1               0  0.......................               0
Risso's dolphin.......................            10.0               4  0.57 (0.25).............               9
Bottlenose dolphin....................             4.8               2  NA (NA)--32 Northern GOM              18
                                                                         Bay, Sound and Estuary
                                                                         stocks.
                                                                        NA (NA)--Northern GOM
                                                                         continental shelf stock.
                                                                        0.23 (0.03)--GOM eastern
                                                                         coastal stock.
                                                                        0.73 (0.08)--GOM
                                                                         northern coastal stock.
                                                                        NA (NA)--GOM western
                                                                         coastal stock.
                                                                        0.49 (0.05)--Northern
                                                                         GOM oceanic stock.
Rough-toothed dolphin.................             6.7               3  0.6 (0.11)..............              16
Fraser's dolphin......................             1.9               1  NA (NA).................             117
Striped dolphin.......................            51.5              23  1.35 (0.69).............              45
Pantropical spotted dolphin...........           582.6             259  0.76 (0.76).............             259
Atlantic spotted dolphin..............             2.2               1  NA (NA).................              15
Spinner dolphin.......................            72.6              32  4.98 (1.61).............              99
Clymene dolphin.......................            45.6              20  1.14 (0.3)..............              75
----------------------------------------------------------------------------------------------------------------
NA = Not available or not assessed.
\1\ Calculated take is density times the area ensonified to >160 dB (rms) around the planned seismic lines,
  increased by 25%.
\2\ Stock sizes are best populations from NMFS Stock Assessment Reports (see Table 2 above).
\3\ Requested Take Authorization increased to mean group size.

    USGS estimated the number of different individuals that may be 
exposed to airgun sounds with received levels greater than or equal to 
160 dB re 1 [mu]Pa (rms) on one or more occasions by considering the 
total marine area that would be within the 160 dB radius around the 
operating airgun array on at least one occasion and the expected 
density of marine mammals in the area. The number of possible exposures 
(including repeat exposures of the same individuals) can be estimated 
by considering the total marine area that would be within the 160 dB 
radius around the operating airguns, excluding areas of overlap. During 
the proposed survey, the transect lines in the square

[[Page 11842]]

grid are closely spaced (approximately 100 m [328.1 ft] apart at the 
GC955 site and 250 m [820.2 ft] apart at the WR313 site) relative to 
the 160 dB distance (670 m [2,198.2 ft]). Thus, the area including 
overlap is 6.5 times the area excluding overlap at GC955 and 5.3 times 
the area excluding overlap at WR313, so a marine mammal that stayed in 
the survey areas during the entire survey could be exposed 
approximately 6 or 7 times on average. While some individuals may be 
exposed multiple times since the survey tracklines are spaced close 
together; however, it is unlikely that a particular animal would stay 
in the area during the entire survey.
    The number of different individuals potentially exposed to received 
levels greater than or equal to 160 re 1 [mu]Pa (rms) was calculated by 
multiplying:
    (1) The expected species density (in number/km\2\), times
    (2) The anticipated area to be ensonified to that level during 
airgun operations excluding overlap.
    The area expected to be ensonified was determined by entering the 
planned survey lines into a MapInfo GIS, using the GIS to identify the 
relevant areas by ``drawing'' the applicable 160 dB buffer (see Table 1 
of the IHA application) around each seismic line, and then calculating 
the total area within the buffers.
    Applying the approach described above, approximately 356 km\2\ 
(approximately 445 km\2\ including the 25% contingency) would be within 
the 160 dB isopleth on one or more occasions during the proposed 
survey. The take calculations within the study sites do not explicitly 
add animals to account for the fact that new animals (i.e., turnover) 
are not accounted for in the initial density snapshot and animals could 
also approach and enter the area ensonified above 160 dB; however, 
studies suggest that many marine mammals will avoid exposing themselves 
to sounds at this level, which suggests that there would not 
necessarily be a large number of new animals entering the area once the 
seismic survey started. Because this approach for calculating take 
estimates does not allow for turnover in the marine mammal populations 
in the area during the course of the survey, the actual number of 
individuals exposed may be underestimated, although the conservative 
(i.e., probably overestimated) line-kilometer distances used to 
calculate the area may offset this. Also, the approach assumes that no 
cetaceans will move away or toward the tracklines as the Pelican 
approaches in response to increasing sound levels before the levels 
reach 160 dB. Another way of interpreting the estimates that follow is 
that they represent the number of individuals that are expected (in 
absence of a seismic program) to occur in the waters that will be 
exposed to greater than or equal to 160 dB (rms).
    USGS's estimates of exposures to various sound levels assume that 
the proposed surveys will be carried out in full (i.e., approximately 8 
days of seismic airgun operations for the two study sites, 
respectively); however, the ensonified areas calculated using the 
planned number of line-kilometers have been increased by 25% to 
accommodate lines that may need to be repeated, equipment testing, 
account for repeat exposure, etc. As is typical during offshore ship 
surveys, inclement weather and equipment malfunctions are likely to 
cause delays and may limit the number of useful line-kilometers of 
seismic operations that can be undertaken. The estimates of the numbers 
of marine mammals potentially exposed to 160 dB (rms) received levels 
are precautionary and probably overestimate the actual numbers of 
marine mammals that could be involved. These estimates assume that 
there will be no weather, equipment, or mitigation delays, which is 
highly unlikely.
    Table 3 (Table 3 of the IHA application) shows the estimates of the 
number of different individual marine mammals anticipated to be exposed 
to greater than or equal to 160 dB re 1 [mu]Pa (rms) during the seismic 
survey if no animals moved away from the survey vessel. The requested 
take authorization is given in the far right column of Table 3 (Table 3 
of the IHA application). The requested take authorization has been 
increased to the average mean group sizes in the GOM in 1996 to 2001 
(Mullin and Fulling, 2004) and 2003 and 2004 (Mullin, 2007) in cases 
where the calculated number of individuals exposed was between one and 
the mean group size.
    The estimate of the number of individual cetaceans that could be 
exposed to seismic sounds with received levels greater than or equal to 
160 dB re 1 [mu]Pa (rms) during the proposed survey is 358, 
respectively (with 25% contingency) (see Table 3 of the IHA 
application). That total (with 25% contingency) includes 0 baleen 
whales, 1 dwarf/pygmy sperm whale, and 2 beaked whales, (including 
Cuvier's and Mesoplodon beaked whales) could be taken by Level B 
harassment during the proposed seismic survey. Most of the cetaceans 
potentially taken by Level B harassment are delphinids; pantropical 
spotted, spinner, Clymene, and striped dolphins are estimated to be the 
most common species in the area, with estimates of 259, 32, 20, and 23, 
which would represent 0.76, 0.3, 1.61, and 0.69% of the affected 
populations or stocks, respectively.

Encouraging and Coordinating Research

    USGS will coordinate the planned marine mammal monitoring program 
associated with the proposed seismic survey with any parties that 
express interest in this activity.

Negligible Impact and Small Numbers Analysis Determination

    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.''
    In making a negligible impact determination, NMFS evaluated factors 
such as:
    (1) The number of anticipated injuries, serious injuries, or 
mortalities;
    (2) The number, nature, and intensity, and duration of Level B 
harassment (all relatively limited); and
    (3) The context in which the takes occur (i.e., impacts to areas of 
significance, impacts to local populations, and cumulative impacts when 
taking into account successive/contemporaneous actions when added to 
baseline data);
    (4) The status of stock or species of marine mammals (i.e., 
depleted, not depleted, decreasing, increasing, stable, impact relative 
to the size of the population);
    (5) Impacts on habitat affecting rates of recruitment/survival; and
    (6) The effectiveness of monitoring and mitigation measures.
    As described above and based on the following factors, the 
specified activities associated with the marine seismic survey are not 
likely to cause PTS, or other non-auditory injury, serious injury, or 
death. The factors include:
    (1) The likelihood that, given sufficient notice through relatively 
slow ship speed, marine mammals are expected to move away from a noise 
source that is annoying prior to its becoming potentially injurious;
    (2) The potential for temporary or permanent hearing impairment is 
relatively low and would likely be avoided through the implementation 
of the shut-down measures;
    No injuries, serious injuries, or mortalities are anticipated to 
occur as a result of the USGS's planned marine

[[Page 11843]]

seismic surveys, and none are proposed to be authorized by NMFS. Table 
3 of this document outlines the number of requested Level B harassment 
takes that are anticipated as a result of these activities. Due to the 
nature, degree, and context of Level B (behavioral) harassment 
anticipated and described (see ``Potential Effects on Marine Mammals'' 
section above) in this notice, the activity is not expected to impact 
rates of annual recruitment or survival for any affected species or 
stock, particularly given the NMFS and the applicant's proposal to 
implement mitigation, monitoring, and reporting measures to minimize 
impacts to marine mammals.
    For the other marine mammal species that may occur within the 
proposed action area, there are no known designated or important 
feeding and/or reproductive areas. Many animals perform vital 
functions, such as feeding, resting, traveling, and socializing, on a 
diel cycle (i.e., 24 hr cycle). Behavioral reactions to noise exposure 
(such as disruption of critical life functions, displacement, or 
avoidance of important habitat) are more likely to be significant if 
they last more than one diel cycle or recur on subsequent days 
(Southall et al., 2007). Additionally, the seismic survey will be 
increasing sound levels in the marine environment in a relatively small 
area surrounding the vessel (compared to the range of the animals), 
which is constantly travelling over distances, and some animals may 
only be exposed to and harassed by sound for less than day.
    Of the 28 marine mammal species under NMFS jurisdiction that may or 
are known to likely to occur in the study area, six are listed as 
threatened or endangered under the ESA: North Atlantic right, humpback, 
sei, fin, blue, and sperm whales. These species are also considered 
depleted under the MMPA. Of these ESA-listed species, incidental take 
has been requested to be authorized for sperm whales. There is 
generally insufficient data to determine population trends for the 
other depleted species in the study area. To protect these animals (and 
other marine mammals in the study area), USGS must cease or reduce 
airgun operations if any marine mammal enters designated zones. No 
injury, serious injury, or mortality is expected to occur and due to 
the nature, degree, and context of the Level B harassment anticipated, 
and the activity is not expected to impact rates of recruitment or 
survival.
    As mentioned previously, NMFS estimates that 19 species of marine 
mammals under its jurisdiction could be potentially affected by Level B 
harassment over the course of the IHA. The population estimates for the 
marine mammal species that may be taken by Level B harassment were 
provided in Table 3 of this document.
    NMFS's practice has been to apply the 160 dB re 1 [mu]Pa (rms) 
received level threshold for underwater impulse sound levels to 
determine whether take by Level B harassment occurs. Southall et al. 
(2007) provide a severity scale for ranking observed behavioral 
responses of both free-ranging marine mammals and laboratory subjects 
to various types of anthropogenic sound (see Table 4 in Southall et al. 
[2007]).
    NMFS has preliminarily determined, provided that the aforementioned 
mitigation and monitoring measures are implemented, the impact of 
conducting a low-energy marine seismic survey in the deep water of the 
northwestern GOM, April to May, 2013, may result, at worst, in a 
modification in behavior and/or low-level physiological effects (Level 
B harassment) of certain species of marine mammals.
    While behavioral modifications, including temporarily vacating the 
area during the operation of the airgun(s), may be made by these 
species to avoid the resultant acoustic disturbance, the availability 
of alternate areas within these areas for species and the short and 
sporadic duration of the research activities, have led NMFS to 
preliminary determine that the taking by Level B harassment from the 
specified activity will have a negligible impact on the affected 
species in the specified geographic region. NMFS believes that the 
length of the seismic survey, the requirement to implement mitigation 
measures (e.g., shut-down of seismic operations), and the inclusion of 
the monitoring and reporting measures, will reduce the amount and 
severity of the potential impacts from the activity to the degree that 
it will have a negligible impact on the species or stocks in the action 
area.
    NMFS has preliminary determined, provided that the aforementioned 
mitigation and monitoring measures are implemented, that the impact of 
conducting a marine seismic survey in the deep water of the Gulf of 
Mexico, April to May, 2013, 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. 
See Table 3 for the requested authorized take numbers of marine 
mammals.

Impact on Availability of Affected Species or Stock for Taking for 
Subsistence Uses

    Section 101(a)(5)(D) of the MMPA also requires NMFS to determine 
that the authorization will not have an unmitigable adverse effect on 
the availability of marine mammal species or stocks for subsistence 
use. There are no relevant subsistence uses of marine mammals in the 
study area (in the deep water of the northwest GOM) that implicate MMPA 
section 101(a)(5)(D).

Endangered Species Act

    Of the species of marine mammals that may occur in the proposed 
survey area, several are listed as endangered under the ESA, including 
the North Atlantic right, humpback, sei, fin, blue, and sperm whales. 
USGS did not request take of endangered North Atlantic right, humpback, 
sei, fin, and blue whales due to the low likelihood of encountering 
this species during the cruise. Under section 7 of the ESA, USGS has 
initiated formal consultation with the NMFS, Office of Protected 
Resources, Endangered Species Act Interagency Cooperation Division, on 
this proposed seismic survey. NMFS's Office of Protected Resources, 
Permits and Conservation Division, has initiated formal consultation 
under section 7 of the ESA with NMFS's Office of Protected Resources, 
Endangered Species Act Interagency Cooperation Division, to obtain a 
Biological Opinion evaluating the effects of issuing the IHA on 
threatened and endangered marine mammals and, if appropriate, 
authorizing incidental take. NMFS will conclude formal section 7 
consultation prior to making a determination on whether or not to issue 
the IHA. If the IHA is issued, USGS, in addition to the mitigation and 
monitoring requirements included in the IHA, will be required to comply 
with the Terms and Conditions of the Incidental Take Statement 
corresponding to NMFS's Biological Opinion issued to both USGS and 
NMFS's Office of Protected Resources.

National Environmental Policy Act

    With USGS's complete application, they provided NMFS a draft 
``Environmental Assessment and Determination Pursuant to the National 
Environmental Policy Act, 42 U.S.C. 4321 et seq. and Executive Order 
12114 Low-Energy Marine Seismic Survey by the U.S. Geological Survey in 
the Deepwater Gulf of Mexico, April-May 2013,'' which incorporates a 
draft ``Environmental Assessment of Low-Energy Marine Geophysical 
Survey by the U.S. Geological Survey in the

[[Page 11844]]

Northwestern Gulf of Mexico, April-May 2013,'' prepared by LGL Ltd., 
Environmental Research Associates on behalf of USGS. The EA analyzes 
the direct, indirect, and cumulative environmental impacts of the 
proposed specified activities on marine mammals including those listed 
as threatened or endangered under the ESA. Prior to making a final 
decision on the IHA application, NMFS will either prepare an 
independent EA, or, after review and evaluation of the USGS EA for 
consistency with the regulations published by the Council of 
Environmental Quality (CEQ) and NOAA Administrative Order 216-6, 
Environmental Review Procedures for Implementing the National 
Environmental Policy Act, adopt the USGS EA and make a decision of 
whether or not to issue a Finding of No Significant Impact (FONSI).

Proposed Authorization

    NMFS proposes to issue an IHA to USGS for conducting a low-energy 
marine seismic survey in the deep water of the northwestern GOM, 
provided the previously mentioned mitigation, monitoring, and reporting 
requirements are incorporated. The duration of the IHA would not exceed 
one year from the date of its issuance.

Information Solicited

    NMFS requests interested persons to submit comments and information 
concerning this proposed project and NMFS's preliminary determination 
of issuing an IHA (see ADDRESSES). Concurrent with the publication of 
this notice in the Federal Register, NMFS is forwarding copies of this 
application to the Marine Mammal Commission and its Committee of 
Scientific Advisors.

Helen M. Golde,
Acting Director, Office of Protected Resources, National Marine 
Fisheries Service.
[FR Doc. 2013-03837 Filed 2-19-13; 8:45 am]
BILLING CODE 3510-22-P