Takes of Marine Mammals Incidental to Specified Activities; Marine Geophysical Survey in the Northwest Pacific Ocean, March Through April 2012, 4765-4787 [2012-2076]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 77, Number 20 (Tuesday, January 31, 2012)]
[Notices]
[Pages 4765-4787]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2012-2076]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XA879


Takes of Marine Mammals Incidental to Specified Activities; 
Marine Geophysical Survey in the Northwest Pacific Ocean, March Through 
April 2012

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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[[Page 4766]]

SUMMARY: NMFS has received an application from Lamont-Doherty Earth 
Observatory (L-DEO), a part of Columbia University, for an Incidental 
Harassment Authorization (IHA) to take marine mammals, by harassment, 
incidental to conducting a marine geophysical survey in the northwest 
Pacific Ocean, March through April, 2012.

DATES: Comments and information must be received no later than March 1, 
2012.

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 20910-3225. The mailbox address for 
providing email comments is ITP.Cody@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 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.
    An electronic 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 following associated documents are also available at the same 
internet address: the National Science Foundation's (NSF) draft 
Environmental Analysis (EA) pursuant to Executive Order 12114. The EA 
incorporates an ``Environmental Assessment of a Marine Geophysical 
Survey by the R/V Marcus G. Langseth in the Northwest Pacific Ocean, 
March-April, 2012,'' prepared by LGL Limited, on behalf of NSF. 
Documents cited in this notice may be viewed, by appointment, during 
regular business hours, at the aforementioned address.

FOR FURTHER INFORMATION CONTACT: Jeannine Cody, Office of Protected 
Resources, NMFS, (301) 427-8401.

SUPPLEMENTARY INFORMATION:

Background

    Section 101(a)(5)(D) of the Marine Mammal Protection Act of 1972, 
as amended (MMPA; 16 U.S.C. 1361 et seq.) directs the Secretary of 
Commerce 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 ``* * * 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' 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. NMFS must publish a notice in the Federal Register 
within 30 days of its determination to 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

    NMFS received an application on October 31, 2011, from L-DEO for 
the taking by harassment, of marine mammals, incidental to conducting a 
marine geophysical survey in the northwest Pacific Ocean in 
international waters. Upon receipt of additional information, NMFS 
determined the application complete and adequate on December 23, 2011.
    L-DEO, with research funding from the U.S. National Science 
Foundation (NSF), plans to conduct the survey from March 24, 2012, 
through April 16, 2012. L-DEO received an IHA in 2010 to conduct the 
same specified activity in the same location. However, due to medical 
emergencies, L-DEO suspended its operations and was unable to complete 
the seismic survey. Thus, this 2011 survey will allow L-DEO to acquire 
data necessary to complete the abbreviated 2010 study.
    L-DEO plans to use one source vessel, the R/V Marcus G. Langseth 
(Langseth), a seismic airgun array and a single hydrophone streamer to 
conduct a geophysical survey at the Shatsky Rise, a large igneous 
plateau in the northwest Pacific Ocean. The proposed survey will 
provide data necessary to decipher the crustal structure of the Shatsky 
Rise; may address major questions of earth history, geodynamics, and 
tectonics; could impact the understanding of terrestrial magmatism and 
mantle convection; and may obtain data that could be used to improve 
estimates of regional earthquake occurrence and distribution. In 
addition to the operations of the seismic airgun array and hydrophone 
streamer, L-DEO intends to operate a multibeam echosounder (MBES) and a 
sub-bottom profiler (SBP) 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 short-term behavioral disturbance for marine 
mammals in the survey area. This is the principal means of marine 
mammal taking associated with these activities and L-DEO has requested 
an authorization to take 30 species of marine mammals by Level B 
harassment. Take is not expected to result from the use of the MBES or 
the SBP for reasons discussed in this notice. Also, NMFS does not 
expect take to result from collision with the Langseth because it is a 
single vessel moving at

[[Page 4767]]

relatively slow speeds (4.6 knots (kts); 8.5 km per hr (km/h); 5.3 
miles (mi) per hour (mph)) during seismic acquisition within the 
survey, for a relatively short period of time. It is likely that any 
marine mammal would be able to avoid the vessel.

Description of the Specified Activity

    L-DEO's proposed seismic survey on the Shatsky Rise is scheduled to 
commence on March 24, 2012 and end on April 16, 2012. The Langseth 
would depart from Yokohama, Japan on March 24, 2012 and transit to the 
survey area in the northwest Pacific Ocean, approximately 1,200 
kilometers (km) (745.6 miles (mi)) in international waters offshore of 
the east coast of Japan. At the conclusion of the survey activities, 
the Langseth proposes to arrive in Honolulu, Hawaii, on April 16, 2012. 
Some minor deviation from these dates is possible, depending on 
logistics, weather conditions, and the need to repeat some lines if 
data quality is substandard. Therefore, NMFS proposes to issue an 
authorization that is effective from March 24, 2012 to May 7, 2012.
    Geophysical survey activities will involve 3-D seismic 
methodologies to decipher the crustal structure of the Shatsky Rise. To 
obtain high-resolution, 2-D structures of the area's magmatic systems 
and thermal structures, the Langseth will deploy a 36-airgun array as 
an energy source and a 6-km-long (3.7 mi-long) hydrophone streamer. As 
the airgun array is towed along the survey lines, the hydrophone 
streamer will receive the returning acoustic signals and transfer the 
data to the vessel's on-board processing system.
    The proposed study (e.g., equipment testing, startup, line changes, 
repeat coverage of any areas, and equipment recovery) will require 
approximately 7 days (d) to complete approximately 1,216 km (755.6 mi) 
of transect lines. The Langseth will conduct additional seismic 
operations in the survey area associated with turns, airgun testing, 
and repeat coverage of any areas where the initial data quality is sub-
standard. Data acquisition will include approximately 168 hours (hr) of 
airgun operations (7 d x 24 hr).
    L-DEO, the Langseth's operator, will conduct all planned seismic 
data acquisition activities, with on-board assistance by the scientists 
who have proposed the study. The Principal Investigators for this 
survey are Drs. Jun Korenaga (Yale University, New Haven, CT) and 
William Sager (Texas A&M University, College Station, TX). The vessel 
will be self-contained, and the crew will live aboard the vessel for 
the entire cruise.

Description of the Specified Geographic Region

    L-DEO will conduct the proposed survey in international waters in 
the northwest Pacific Ocean. The study area will encompass an area on 
the Shatsky Rise bounded by approximately 33.5-36 degrees ([deg]) North 
by 156-161[deg] East (see Figure 1 in L-DEO's application). Water 
depths in the survey area range from approximately 3,000 to 5,000 
meters (m) (1.9 to 3.1 mi).

Vessel Specifications

    The Langseth, owned by NSF, is a seismic research vessel with a 
propulsion system designed to be as quiet as possible to avoid 
interference with the seismic signals emanating from the airgun array. 
The vessel, which has a length of 71.5 m (235 feet (ft)); a beam of 
17.0 m (56 ft); a maximum draft of 5.9 m (19 ft); and a gross tonnage 
of 3,834 pounds, is powered by two 3,550 horsepower (hp) Bergen BRG-6 
diesel engines which drive two propellers. Each propeller has four 
blades and the shaft typically rotates at 750 revolutions per minute. 
The vessel also has an 800-hp bowthruster, which is not used during 
seismic acquisition. The Langseth's operation speed during seismic 
acquisition will be approximately 4.6 kts (8.5 km/h; 5.3 mph) and the 
cruising speed of the vessel outside of seismic operations is 18.5 km/h 
(11.5 mph or 10 kts).
    The Langseth will tow the 36-airgun array, as well as the 
hydrophone streamer, along predetermined lines. When the Langseth is 
towing the airgun array and the hydrophone streamer, the turning rate 
of the vessel is limited to five degrees per minute. Thus, the 
maneuverability of the vessel is limited during operations with the 
streamer.
    The vessel also has an observation tower from which protected 
species visual observers (PSVO) will watch for marine mammals before 
and during the proposed airgun operations. When stationed on the 
observation platform, the PSVO's eye level will be approximately 21.5 m 
(71 ft) above sea level providing the PSVO an unobstructed view around 
the entire vessel.

Acoustic Source Specifications

Seismic Airguns

    The Langseth will deploy a 36-airgun array, with a total volume of 
approximately 6,600 cubic inches (in\3\) at a tow depth of 9 m (29.5 
ft). The airguns are a mixture of Bolt 1500LL and Bolt 1900LLX airguns 
ranging in size from 40 to 360 in\3\, with a firing pressure of 1,900 
pounds per square inch. The dominant frequency components range from 
zero to 188 Hertz (Hz). The array configuration consists of four 
identical linear strings, with 10 airguns on each string; the first and 
last airguns will be spaced 16 m (52 ft) apart. Of the 10 airguns, nine 
will fire simultaneously while the tenth airgun will serve as a spare 
and will be turned on in case of failure of one of the other airguns. 
The Langseth will distribute the array across an area of approximately 
24 x 16 m (78.7 x 52.5 ft) and will tow the array approximately 140 m 
(459.3 ft) behind the vessel. The tow depth of the array will be 9 m 
(29.5 ft).
    During the multichannel seismic (MCS) survey, each airgun array 
will emit a pulse at approximately 20-second (s) intervals which 
corresponds to a shot interval of approximately 50 m (164 ft). During 
firing, the airguns will emit a brief (approximately 0.1 s) pulse of 
sound; during the intervening periods of operations, the airguns will 
be silent.

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 root mean square (rms). Root mean 
square, 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

[[Page 4768]]

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 source levels of the airgun array used by L-DEO on the 
Langseth is 236 to 265 dB re: 1 [mu]Pa(p-p) and the rms 
value for a given airgun pulse is typically 16 dB re: 1 [mu]Pa lower 
than the peak-to-peak value (Greene, 1997; McCauley et al., 1998, 
2000a). 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.
    Accordingly, L-DEO has predicted the received sound levels in 
relation to distance and direction from the 36-airgun array and the 
single Bolt 1900LL 40-in\3\ airgun, which will be used during power 
downs. A detailed description of L-DEO's modeling for marine seismic 
source arrays for species mitigation is provided in Appendix A of NSF's 
EA. These are the nominal source levels applicable to downward 
propagation. The effective source levels for horizontal propagation are 
lower than those for downward propagation because of the directional 
nature of the sound from the airgun array. Appendix B(3) of NSF's EA 
discusses the characteristics of the airgun pulses. NMFS refers the 
reviewers to the IHA application and EA documents for additional 
information.

Predicted Sound Levels for the Airguns

    Tolstoy et al., (2009) reported results for propagation 
measurements of pulses from the Langseth's 36-airgun, 6,600 in\3\ array 
in shallow-water (approximately 50 m (164 ft)) and deep-water depths 
(approximately 1,600 m (5,249 ft)) in the Gulf of Mexico in 2007 and 
2008. Results of the Gulf of Mexico calibration study (Tolstoy et al., 
2009) showed that radii around the airguns for various received levels 
varied with water depth and that sound propagation varied with array 
tow depth.
    L-DEO used the results from the Gulf of Mexico study to determine 
the algorithm for its model that calculates the exclusion zones (EZ) 
for the 36-airgun array and the single airgun. L-DEO uses these values 
to designate mitigation zones and to estimate take (described in 
greater detail in Section VII of L-DEO's application and Section IV of 
NSF's EA) for marine mammals.
    Comparison of the Tolstoy et al. calibration study with L-DEO's 
model for the Langseth's 36-airgun array indicated that the model 
represents the actual received levels, within the first few kilometers, 
where the predicted EZs are located. However, the model for deep water 
(greater than 1,000 m; 3,280 ft) overestimated the received sound 
levels at a given distance but is still valid for defining exclusion 
zones at various tow depths. Because the tow depth of the array in the 
calibration study is less shallow (6 m; 19.7 ft) than the tow depth 
array in the proposed survey (9 m; 29.5 ft), L-DEO used correction 
factors for estimating the received levels in deep water during the 
proposed survey. The correction factors used were the ratios of the 
160-,180-, and 190-dB distances from the modeled results for the 6,600 
in\3\ airgun array towed at 6 m (19.7 ft) versus 9 m (29.5 ft) from LGL 
(2008); 1.285, 1.338, and 1.364 respectively. For a single airgun, the 
tow depth has minimal effect on the maximum near-field output and the 
shape of the frequency spectrum for the single airgun; thus, the 
predicted EZs are essentially the same at different tow depths. The L-
DEO model does not allow for bottom interactions, and thus is most 
directly applicable to deep water.
    Table 1 summarizes the predicted distances at which sound levels 
(160- and 180-dB) are expected to be received from the 36-airgun array 
and a single airgun operating in deep water. 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 dB 
re: 1 [mu]Pa. NMFS believes that to avoid the potential for permanent 
physiological damage (Level A harassment), cetaceans should not be 
exposed to pulsed underwater noise at received levels exceeding 180 dB 
re: 1 [mu]Pa. The 180-dB level is a shutdown criterion applicable to 
cetaceans, as specified by NMFS (2000); these levels were used to 
establish the EZs. NMFS also assumes that cetaceans exposed to levels 
exceeding 160 dB re: 1 [mu]Pa (rms) may experience Level B harassment.

 Table 1--Measured (Array) or Predicted (Single Airgun) Distances To Which Sound Levels Greater Than or Equal to
160 and 180 dB re: 1 [mu]PaRms That Could Be Received in Deep Water Using a 36-Airgun Array, as Well as a Single
Airgun Towed at a Depth of 9 m (29.5 ft) During the Proposed Survey in the Northwest Pacific Ocean, During March-
                                                   April, 2012
                            [Distances Are Based On Model Results Provided By L-DEO]
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                                                                         Predicted RMS Distances (m)
         Source and volume                Water depth      -----------------------------------------------------
                                                                 160 dB            180 dB            190 dB
----------------------------------------------------------------------------------------------------------------
Single Bolt airgun (40 in\3\)......  Deep (>1,000 m)......               385                40                12
36-Airgun Array....................  .....................             3,850               940               400
----------------------------------------------------------------------------------------------------------------

    Appendix A of NSF's EA discusses L-DEO's calculations for the 
model. NMFS refers the reviewers to L-DEO's application and the NSF's 
EA for additional information.

Multibeam Echosounder

    The Langseth will operate a Kongsberg EM 122 MBES concurrently 
during airgun operations to map characteristics of the ocean floor. The 
hull-mounted MBES emits brief pulses of sound (also called a ping) 
(10.5 to 13 kilohertz (kHz)) in a fan-shaped beam that extends downward 
and to the sides of the ship. The transmitting beamwidth is one or two 
degrees ([deg]) fore-aft and 150 [deg] athwartship and the maximum 
source level is 242 dB re: 1 [mu]Pa.
    For deep-water operations, each ping consists of eight (in water 
greater than 1,000 m; 3,280 ft) or four (less than 1,000 m; 3,280 ft) 
successive, fan-shaped transmissions, from two to 15 milliseconds (ms) 
in duration and each ensonifying a sector that extends 1 [deg] fore-
aft. Continuous wave pulses increase from two to 15 milliseconds (ms) 
long in water depths up to 2,600 m (8,530 ft). The MBES uses frequency-
modulated chirp pulses up to 100-ms long in water greater than 2,600 m 
(8,530 ft). The eight successive transmissions span an overall cross-
track angular extent of about 150 [deg], with

[[Page 4769]]

2-ms gaps between the pulses for successive sectors.

Sub-bottom Profiler

    The Langseth will also operate a Knudsen Chirp 3260 SBP 
concurrently during airgun and MBES operations to provide information 
about the sedimentary features and bottom topography. The SBP is 
capable of reaching depths of 10,000 m (6.2 mi). The dominant frequency 
component of the SBP is 3.5 kHz which is directed downward in a 27[deg] 
cone by a hull-mounted transducer on the vessel. The nominal power 
output is 10 kilowatts (kW), but the actual maximum radiated power is 
three kW or 222 dB re: 1 [mu]Pa. The ping duration is up to 64 ms with 
a pulse interval of one second, but a common mode of operation is to 
broadcast five pulses at 1-s intervals followed by a 5-s pause.
    NMFS expects that acoustic stimuli resulting from the proposed 
operation of the single airgun or the 36-airgun array has the potential 
to harass marine mammals, incidental to the conduct of the proposed 
seismic survey. NMFS expects these disturbances to be temporary and 
result in a temporary modification in behavior and/or low-level 
physiological effects (Level B harassment only) of small numbers of 
certain species of marine mammals. NMFS does not expect that the 
movement of the Langseth, during the conduct of the seismic survey, has 
the potential to harass marine mammals because of the relatively slow 
operation speed of the vessel (4.6 kts; 8.5 km/hr; 5.3 mph) during 
seismic acquisition.

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

    Thirty-four marine mammal species may occur in the Shatsky Rise 
survey area, including 26 odontocetes (toothed cetaceans), seven 
mysticetes (baleen whales) and one species of pinniped during March 
through April. Six of these species are listed as endangered under the 
Endangered Species Act of 1973 (ESA; 16 U.S.C. 1531 et seq.), including 
the blue (Balaenoptera musculus), fin (Balaenoptera physalus), humpback 
(Megaptera novaeangliae), north Pacific right (Eubalaena japonica), sei 
(Balaenoptera borealis), and sperm (Physeter macrocephalus) whales.
    Based on available data, the western north Pacific gray whale 
(Eschrichtius robustus) may have the potential to migrate off of the 
Pacific coast of Japan (Reilly et al., 2008a), though any occurrence in 
the survey area would be rare as gray whales are known to prefer 
nearshore coastal waters. Based on available data, L-DEO does not 
expect to encounter the western north Pacific gray whale within the 
proposed study area and does not present analysis for these species. 
Accordingly, NMFS did not consider this cetacean species in greater 
detail and the proposed IHA will only address requested take 
authorizations for the seven mysticetes, 26 odontocetes, and one 
species of pinniped. The species of marine mammals expected to be most 
common in the survey area (all delphinids) include the short-beaked 
common (Delphinus delphis), striped (Stenella coeruleoalba), and 
Fraser's (Lagenodelphis hosei) dolphins, and Dall's porpoise 
(Phocoenoides dalli).
    Table 2 presents information on the abundance, distribution, and 
conservation status of the marine mammals that may occur in the 
proposed survey area March through April, 2012.

  Table 2--Habitat, Abundance, and Conservation Status of Marine Mammals That May Occur in or Near the Proposed
                     Seismic Survey Area on the Shatsky Rise in the Northwest Pacific Ocean
            [See text and Tables 2 and 3 in L-DEO's application and the NSF's EA for further details]
----------------------------------------------------------------------------------------------------------------
            Species                  Habitat        Abundance in the NW Pacific      ESA \1\        Density \2\
----------------------------------------------------------------------------------------------------------------
Mysticetes
    North Pacific right whale.  Pelagic, coastal.  few 100 \3\.................  EN.............            0.04
    Humpback whale............  Mainly nearshore,  938-1107 \4\................  EN.............            0.47
                                 banks.
    Minke whale...............  Pelagic, coastal.  25,000 \5\..................  NL.............            2.51
    Bryde's whale.............  Pelagic, coastal.  20,501 \6\..................  NL.............            0.52
    Sei whale.................  Primarily          7260-12,620 \7\.............  EN.............            1.78
                                 offshore,
                                 pelagic.
    Fin whale.................  Continental        13,620-18,680 \8\...........  EN.............            0.74
                                 slope, mostly
                                 pelagic.
    Blue whale................  Pelagic, coastal.  3500 \9\....................  EN.............            0.39
Odontocetes
    Sperm whale...............  Usually pelagic,   29,674 \10\.................  EN.............            1.04
                                 deep sea.
    Pygmy sperm whale.........  Deep waters off    N.A.........................  NL.............            3.19
                                 the shelf.
    Dwarf sperm whale.........  Deep waters off    11,200 \11\.................  NL.............            7.82
                                 the shelf.
    Cuvier's beaked whale.....  Pelagic..........  20,000 \11\.................  NL.............            6.80
    Baird's beaked whale......  Deep water.......  N.A.........................  NL.............            0.88
    Longman's beaked whale....  Deep water.......  N.A.........................  NL.............            0.45
    Hubb's beaked whale.......  Deep water.......  25,300 \12\.................  NL.............            1.28
    Ginkgo-toothed beaked       Pelagic..........  25,300 \12\.................  NL.............            0.01
     whale.
    Blainville's beaked whale.  Pelagic..........  25,300 \12\.................  NL.............            3.12
    Stejneger's beaked whale..  Deep water.......  25,300 \12\.................  NL.............           23.99
    Rough-toothed dolphin.....  Deep water.......  145,900 \11\................  NL.............           70.41
    Common bottlenose dolphin.  Coastal, oceanic,  168,000 \13\................  NL.............            0.83
                                 shelf break.
    Pantropical spotted         Pelagic, coastal.  438,000 \13\................  NL.............          119.07
     dolphin.
    Spinner dolphin...........  Pelagic, coastal.  801,000 \14\................  NL.............            4.57
    Striped dolphin...........  Off continental    570,000 \13\................  NL.............          309.35
                                 shelf.
    Fraser's dolphin..........  Waters >1000 m...  289,300 \11\................  NL.............           36.40
    Short-beaked common         Shelf, pelagic,    2,963,000 \15\..............  NL.............            0.41
     dolphin.                    seamounts.
    Pacific white-sided         Continental        988,000 \16\................  NL.............           10.8
     dolphin.                    slope, pelagic.
    Northern right whale        Deep water.......  307,000 \16\................  NL.............            1.32
     dolphin.
    Risso's dolphin...........  Deep water,        838,000 \13\................  NL.............            0
                                 seamounts.
    Melon-headed whale........  Oceanic..........  45,400 \11\.................  NL.............            2.05
    Pygmy killer whale........  Deep, pantropical  38,900 \11\.................  NL.............            0.16
                                 waters.
    False killer whale........  Pelagic..........  16,000 \13\.................  NL.............            5.00
    Killer whale..............  Widely             8500 \11\...................  NL.............           21.94
                                 distributed.

[[Page 4770]]

 
    Short-finned pilot whale..  Mostly pelagic,    53,000 \13\.................  NL.............            1.04
                                 high-relief.
    Dall's porpoise...........  Deep water.......  1,337,224 \17\..............  NL.............            3.19
Pinnipeds
    Northern fur seal.........  Pelagic, coastal.  1.1 million \18\............  NL.............            1.79 
----------------------------------------------------------------------------------------------------------------
N.A.--Not available or not assessed.
\1\ Endangered Species Act: EN = Endangered, NL = Not listed
\2\ Density estimate as listed in Table 3 of L-DEO's application. Refer to page 41 for specific references.
\3\ North Pacific (Jefferson et al. 2008).
\4\ Western North Pacific (Calambokidis et al. 2008).
\5\ Northwest Pacific and Okhotsk Sea (Buckland et al. 1992; IWC 2010a).
\6\ Western North Pacific (Kitakado et al. 2008; IWC 2010a).
\7\ North Pacific (Tillman 1977).
\8\ North Pacific (Ohsumi and Wada 1974).
\9\ North Pacific (NMFS 1998).
\10\ Western North Pacific (Whitehead 2002b).
\11\ Eastern Tropical Pacific (ETP) (Wade and Gerrodette 1993).
\12\ ETP; all Mesoplodon spp. (Wade and Gerrodette 1993).
\13\ Western North Pacific (Miyashita 1993a).
\14\ Whitebelly spinner dolphin in the ETP in 2000 (Gerrodette et al. 2005 in Hammond et al 2008a).
\15\ ETP (Gerrodette and Forcada 2002 in Hammond et al 2008b).
\16\ North Pacific (Miyashita 1993b).
\17\ North Pacific (Buckland et al 1993).
\18\ North Pacific, 2004-2005 (Gelatt and Lowry 2008).

    NMFS refers the reader to Sections III and IV of L-DEO's 
application for detailed information regarding the abundance and 
distribution, population status, and life history and behavior of these 
species and their occurrence in the proposed project area. The 
application also presents how L-DEO 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 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, but NMFS expects the disturbance to be 
localized and short-term.

Tolerance

    Studies on marine mammals' tolerance to sound in the natural 
environment are relatively rare. Richardson et al. (1995) defines 
tolerance as the occurrence of marine mammals in areas where they are 
exposed to human activities or manmade 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 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 (see Appendix B(5) in NSF's EA). That is often true even in 
cases when the pulsed sounds must be readily audible to the animals 
based on measured received levels and the hearing sensitivity of 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 (Stone 2003; Stone and 
Tasker 2006; Moulton et al. 2005, 2006a; Weir 2008a for sperm whales), 
(MacLean and Koski 2005; Bain and Williams 2006 for Dall's porpoises). 
The relative responsiveness of baleen and toothed whales are quite 
variable.

Masking of Natural Sounds

    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).
    NMFS expects the masking effects of pulsed sounds (even from large 
arrays of airguns) on marine mammal calls and other natural sounds to 
be limited, although there are very few specific data on this. Because 
of the intermittent nature and low duty cycle of seismic

[[Page 4771]]

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 
northeast Pacific 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). 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. 
Refer to Appendix B(4) of NSF's EA for a more detailed discussion of 
masking effects on marine mammals.

Behavioral Disturbance

    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). 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). 
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 
industrial sound. In most cases, this approach likely overestimates the 
numbers of marine mammals that would be affected in some biologically-
important manner.
    The sound criteria used to estimate how many marine mammals might 
be disturbed to some biologically-important degree by a seismic program 
are based primarily on behavioral observations of a few species. 
Scientists have conducted detailed studies on humpback, gray, bowhead 
(Balaena mysticetus), and sperm whales. Less detailed data are 
available for some other species of baleen whales, small toothed 
whales, and sea otters (Enhydra lutris), but for many species there are 
no data on responses to marine seismic surveys.
    Baleen Whales--Baleen whales generally tend to avoid operating 
airguns, but avoidance radii are quite variable (reviewed in Richardson 
et al., 1995). Whales are often reported to show no overt reactions to 
pulses from large arrays of airguns at distances beyond a few 
kilometers, even though the airgun pulses remain well above ambient 
noise levels out to much longer distances. However, as reviewed in 
Appendix B(5) of the NSF's EA, baleen whales exposed to strong noise 
pulses from airguns often react by deviating from their normal 
migration route and/or interrupting their feeding and moving away from 
the area. 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 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 four to 15 km from the source. A 
substantial proportion of the baleen whales within those distances may 
show avoidance or other strong behavioral reactions to the airgun 
array. Subtle behavioral changes sometimes become evident at somewhat 
lower received levels, and studies summarized in Appendix B(5) of NSF's 
EA have shown that some species of baleen whales, notably bowhead and 
humpback whales, at times show strong avoidance at received levels 
lower than 160-170 dB re: 1 [mu]Pa.
    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, 20-in\3\ airgun with source 
level of 227 dB re: 1 [micro]Pa (p-p). In the 1998 study, the 
researchers documented that avoidance reactions began at five to eight 
km (3.1 to 4.9 mi) from the array, and that those reactions kept most 
pods approximately three to four km (1.9 to 2.5 mi) from the operating 
seismic boat. In the 2000 study, McCauley et al. noted localized 
displacement during migration of four to five km (2.5 to 3.1 mi) by 
traveling pods and seven to 12 km (4.3 to 7.5 mi) by more sensitive 
resting pods of cow-calf pairs. Avoidance distances with respect to the 
single airgun were smaller but consistent with the results from the 
full array in terms of the received sound levels. The mean received 
level for initial avoidance of an approaching airgun was 140 dB re: 1 
[mu]Pa for humpback pods containing females, and at the mean closest 
point of approach distance, the received level was 143 dB re: 1 [mu]Pa. 
The initial avoidance response generally occurred at distances of five 
to eight km (3.1 to 4.9 mi) from the airgun array and two km (1.2 mi) 
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.
    Data collected by observers during several seismic surveys in the 
northwest Atlantic Ocean 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 versus non-seismic periods 
(Moulton and Holst, 2010).
    Humpback whales on their summer feeding grounds in Frederick Sound 
and Stephens Passage, Alaska did not

[[Page 4772]]

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 
re: 1 [mu]Pa.
    Other 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). Although, the evidence for this 
was circumstantial and subject to alternative explanations (IAGC, 
2004). Also, the evidence was not consistent with subsequent results 
from the same area of Brazil (Parente et al., 2006), or with direct 
studies of humpbacks exposed to seismic surveys in other areas and 
seasons. After allowance for data from subsequent years, there was ``no 
observable direct correlation'' between strandings and seismic surveys 
(IWC, 2007: 236).
    There are no data on reactions of right whales to seismic surveys, 
but results from the closely-related bowhead whale show that their 
responsiveness can be quite variable depending on their activity 
(migrating versus feeding). Bowhead whales migrating west across the 
Alaskan Beaufort Sea in autumn, in particular, are unusually 
responsive, with substantial avoidance occurring out to distances of 20 
to 30 km (12.4 to 18.6 mi) from a medium-sized airgun source at 
received sound levels of approximately 120 to 130 dB re: 1 [mu]Pa 
(Miller et al., 1999; Richardson et al., 1999; see Appendix B(5) of 
NSF's EA). However, more recent research on bowhead whales (Miller et 
al., 2005; Harris et al., 2007) corroborates earlier evidence that, 
during the summer feeding season, bowheads are not as sensitive to 
seismic sources. Nonetheless, subtle but statistically significant 
changes in surfacing--respiration--dive cycles were evident upon 
statistical analysis (Richardson et al., 1986). In the summer, bowheads 
typically begin to show avoidance reactions at received levels of about 
152 to 178 dB re: 1 [mu]Pa (Richardson et al., 1986, 1995; Ljungblad et 
al., 1988; Miller et al., 2005).
    Reactions of migrating and feeding (but not wintering) gray whales 
to seismic surveys have been studied. Malme et al. (1986, 1988) studied 
the responses of feeding eastern Pacific gray whales to pulses from a 
single 100-in\3\ airgun off St. Lawrence Island in the northern Bering 
Sea. They estimated, based on small sample sizes, that 50 percent of 
feeding gray whales stopped feeding at an average received pressure 
level of 173 dB re: 1 [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. 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) 
also observed localized avoidance by fin whales during seismic airgun 
events in the western Mediterranean Sea and adjacent Atlantic waters 
from 2006-2009. They reported that singing fin whales moved away from 
an operating airgun array for a time period that extended beyond the 
duration of the airgun activity.
    Ship-based monitoring studies of baleen whales (including blue, 
fin, sei, minke, and whales) in the northwest Atlantic found that 
overall, this group had lower sighting rates during seismic versus 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, 2011). The western 
Pacific gray whale population did not seem affected by a seismic survey 
in its feeding ground during a previous year (Johnson et al., 2007). 
Similarly, bowhead whales have continued to travel to the eastern 
Beaufort Sea each summer, and their numbers have increased notably, 
despite seismic exploration in their summer and autumn range for many 
years (Richardson et al., 1987; Allen and Agliss, 2011).
    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 earlier and 
(in more detail) in Appendix B of NSF's EA 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 protected species observers (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

[[Page 4773]]

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. The beluga whale (Delphinapterus leucas) is a species that 
(at least at times) shows long-distance avoidance of seismic vessels. 
Summer aerial surveys conducted in the southeastern Beaufort Sea 
reported that sighting rates of beluga whales were significantly lower 
at distances of 10 to 20 km (6.2 to 12.4 mi) from an operating airgun 
array compared to distances of 20 to 30 km (12.4 to 18.6 mi). Further, 
PSOs on seismic boats in that area have rarely reported sighting beluga 
whales (Miller et al., 2005; Harris et al., 2007).
    Captive bottlenose dolphins (Tursiops truncatus) and beluga whales 
exhibited changes in behavior when exposed to strong pulsed sounds 
similar in duration to those typically used in seismic surveys 
(Finneran et al., 2000, 2002, 2005). However, the animals tolerated 
high received levels of sound before exhibiting aversive behaviors.
    Results for porpoises depend on species. The limited available data 
suggest that harbor porpoises (Phocoena phocoena) show stronger 
avoidance of seismic operations than do Dall's porpoises (Stone, 2003; 
MacLean and Koski, 2005; Bain and Williams, 2006; Stone and Tasker, 
2006). Dall's porpoises seem relatively tolerant of airgun operations 
(MacLean and Koski, 2005; Bain and Williams, 2006), although they too 
have been observed to avoid large arrays of operating airguns 
(Calambokidis and Osmek, 1998; Bain and Williams, 2006). This apparent 
difference in responsiveness of these two porpoise species is 
consistent with their relative responsiveness to boat traffic and some 
other acoustic sources (Richardson et al., 1995; Southall et al., 
2007).
    Most studies of sperm whales exposed to airgun sounds indicate that 
the sperm whale shows considerable tolerance of airgun pulses (e.g., 
Stone, 2003; Moulton et al., 2005, 2006a; Stone and Tasker, 2006; Weir, 
2008). In most cases the whales do not show strong avoidance, and they 
continue to call (see Appendix B of NSF's EA for review). However, 
controlled exposure experiments in the Gulf of Mexico indicate that 
foraging behavior was altered upon exposure to airgun sound (Jochens et 
al., 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 (Ziphius cavirostris) 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 the 
mysticetes, belugas, and harbor porpoises (See Appendix B of NSF's EA).
    Pinnipeds--Pinnipeds are not likely to show a strong avoidance 
reaction to the airgun array. Visual monitoring from seismic vessels 
has shown only slight (if any) avoidance of airguns by pinnipeds, and 
only slight (if any) changes in behavior, see Appendix B(5) of NSF's 
EA. In the Beaufort Sea, some ringed seals avoided an area of 100 m 
(328 ft) to (at most) a few hundred meters around seismic vessels, but 
many seals remained within 100 to 200 m (328 to 656 ft) of the 
trackline as the operating airgun array passed by (e.g., Harris et al., 
2001; Moulton and Lawson, 2002; Miller et al., 2005). Ringed seal 
sightings averaged somewhat farther away from the seismic vessel when 
the airguns were operating than when they were not, but the difference 
was small (Moulton and Lawson, 2002). Similarly, in Puget Sound, 
sighting distances for harbor seals and California sea lions tended to 
be larger when airguns were operating (Calambokidis and Osmek, 1998). 
Previous telemetry work suggests that avoidance and other behavioral 
reactions may be stronger than evident to date from visual studies 
(Thompson et al., 1998).

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 et 
al., 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-

[[Page 4774]]

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. 
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 (introduced 
earlier in this document) presents the distances from the Langseth's 
airguns at which the received energy level (per pulse, flat-weighted) 
would be expected to be greater than or equal to 180 dB re: 1 [mu]Pa.
    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 dB re: 1 [mu]Pa. NMFS believes that to avoid the 
potential for permanent physiological damage (Level A harassment), 
cetaceans should not be exposed to pulsed underwater noise at received 
levels exceeding 180 dB re: 1 [mu]Pa. The 180-dB level is a shutdown 
criterion applicable to cetaceans, as specified by NMFS (2000); these 
levels were used to establish the EZs. NMFS also assumes that cetaceans 
exposed to SPLs exceeding 160 dB re: 1 [mu]Pa may experience Level B 
harassment.
    Researchers have derived TTS information for odontocetes from 
studies on the bottlenose dolphin and beluga. 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 (Southall et al., 2007). For this 
proposed study, L-DEO expects no cases of TTS given the low abundance 
of baleen whales in the planned study area at the time of the survey, 
and the strong likelihood that baleen whales would avoid the 
approaching airguns (or vessel) before being exposed to levels high 
enough for TTS to occur.
    In pinnipeds, TTS thresholds associated with exposure to brief 
pulses (single or multiple) of underwater sound have not been measured. 
Initial evidence from more prolonged (nonpulse) exposures suggested 
that some pinnipeds (harbor seals in particular) incur TTS at somewhat 
lower received levels than do small odontocetes exposed for similar 
durations (Kastak et al., 1999, 2005; Ketten et al., 2001). The 
indirectly estimated TTS threshold for pulsed sounds would be 
approximately 181 to 186 dB re: 1 [mu]Pa (Southall et al., 2007), or a 
series of pulses for which the highest SEL values are a few dB lower. 
Corresponding values for California sea lions and northern elephant 
seals are likely to be higher (Kastak et al., 2005).
    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. 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-see