[Federal Register Volume 73, Number 151 (Tuesday, August 5, 2008)]
[Notices]
[Pages 45407-45427]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E8-17949]



[[Page 45407]]

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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XI15


Small Takes of Marine Mammals Incidental to Specified Activities; 
Marine Geophysical Survey in the Gulf of Alaska, September 2008

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

ACTION:  Notice; proposed incidental take authorization; request for 
comments.

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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 incidental to 
conducting a marine seismic survey in the Gulf of Alaska during 
September 2008. Pursuant to the Marine Mammal Protection Act (MMPA), 
NMFS is requesting comments on its proposal to issue an IHA to L-DEO to 
incidentally take, by Level B harassment only, small numbers of several 
species of marine mammals during the aforementioned activity.

DATES:  Comments and information must be received no later than 
September 4, 2008.

ADDRESSES:  Comments on the application should be addressed to P. 
Michael Payne, Chief, Permits, Conservation and Education Division, 
Office of Protected Resources, National Marine Fisheries Service, 1315 
East-West Highway, Silver Spring, MD 20910-3225. The mailbox address 
for providing email comments is [email protected]. Comments sent 
via e-mail, including all attachments, must not exceed a 10-megabyte 
file size.
    A copy of the application containing a list of the references used 
in this document may be obtained by writing to the address specified 
above, telephoning the contact listed below (see FOR FURTHER 
INFORMATION CONTACT), or visiting the internet at: http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications.
    Documents cited in this notice may be viewed, by appointment, 
during regular business hours, at the aforementioned address.

FOR FURTHER INFORMATION CONTACT: Howard Goldstein or Ken Hollingshead, 
Office of Protected Resources, NMFS, (301) 713-2289.

SUPPLEMENTARY INFORMATION:

Background

    Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) 
direct the Secretary of Commerce to allow, upon request, the 
incidental, but not intentional, taking of marine mammals by U.S. 
citizens who engage in a specified activity (other than commercial 
fishing) within a specified geographical region if certain findings are 
made and either regulations are issued or, if the taking is limited to 
harassment, a notice of a proposed authorization is provided to the 
public for review.
    Authorization shall be granted if NMFS finds that the taking will 
have a negligible impact on the species or stock(s), will not have an 
unmitigable adverse impact on the availability of the species or 
stock(s) for subsistence uses (where relevant), and if the permissible 
methods of taking and requirements pertaining to the mitigation, 
monitoring and reporting of such takings are set forth. NMFS has 
defined ``negligible impact'' in 50 CFR 216.103 as '' * * * an impact 
resulting from the specified activity that cannot be reasonably 
expected to, and is not reasonably likely to, adversely affect the 
species or stock through effects on annual rates of recruitment or 
survival.''
    Section 101(a)(5)(D) of the MMPA established an expedited process 
by which citizens of the United States can apply for an authorization 
to incidentally take small numbers of marine mammals by harassment. 
Except with respect to certain activities not pertinent here, the MMPA 
defines ``harassment'' as:

    any act of pursuit, torment, or annoyance which (I) has the 
potential to injure a marine mammal or marine mammal stock in the 
wild [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].

    Section 101(a)(5)(D) establishes a 45-day time limit for NMFS 
review of an application followed by a 30-day public notice and comment 
period on any proposed authorizations for the incidental harassment of 
marine mammals. Within 45 days of the close of the comment period, NMFS 
must either approve or deny the authorization.

Summary of Request

    On April 10, 2008, NMFS received an application from L-DEO for the 
taking, by Level B harassment only, of small numbers of 21 species of 
marine mammals incidental to conducting, under a cooperative agreement 
with the National Science Foundation (NSF), a seismic survey in the 
northeast Gulf of Alaska (GOA). The proposed cruise will take place in 
the territorial waters and Exclusive Economic Zone (EEZ) of the U.S. 
and is scheduled to occur from 31 August to 23 September 2008.
    The purpose of the proposed seismic survey is to examine crustal 
structure, fault patterns, and tectonic-climate geohistory of the area. 
The proposed program will investigate the interplay of climate and 
tectonics onshore and offshore in an area that includes the world's 
largest strike-slip earthquakes (Magnitude 8.0 Denali Event), largest 
earthquake caused uplift (14.4 m or 47 ft in 1962), largest area of 
seismic uplift (during the 1962 event), highest tsunami (over 200 m or 
656 ft in Latoya Bay in 1958), largest temperate glaciers (the 
Malaspina and Bering Glaciers), and some of the highest sedimentation 
rates (over 1 m or 3.3 ft per year in some places). Nowhere else on the 
planet are tectonics and climate interacting to create this combination 
of mountain building, glacial erosion, strike-slip (California style), 
and subduction (Japan style) earthquakes.
    While affecting a small local population in the past, natural 
seismic activity in the GOA could influence the whole of the North 
Pacific basin, which includes many large population centers. Alaska is 
being directly affected by modern climate change, and new evidence 
suggests that, as climate changes tectonics respond and vice versa. 
This interplay could be fundamental to the way the Earth works as a 
system, and by examining this interplay, the intention of the STEEP 
program is to examine the feedbacks that drive the system.
    The STEEP program is 5 years in length and includes scientists from 
over 10 universities. The study represents the most comprehensive study 
of tectonic and climate interactions ever undertaken in a single 
project. The offshore seismic component is a keystone for the 
experiment. The data obtained from the seismic survey will be used to 
determine the history of tectonic-climate interplay, as well as the 
nature of the Yakutat plate that is causing all of the deformation in 
southern Alaska, built the Saint Elias Mountains, and started the 
aggressive glaciation that continues today.

Description of the Activity

    The seismic survey will involve one source vessel, the R/V Marcus 
G. Langseth (Langseth), which will occur offshore from the Saint Elias 
Mountains. The Langseth will deploy an array of 36

[[Page 45408]]

airguns (6,600 in\3\) as an energy source and, at times, a receiving 
system consisting of one 8-km (3.7-mi) towed hydrophone streamer. The 
streamer will be towed at a depth of 7 m (23 ft) and the airguns at 9 m 
(29.5 ft). The Langseth will also deploy Ocean Bottom Seismometers 
(OBSs) to receive the returning acoustic signals. The OBSs are housed 
in 43-cm diameter glass spheres that have a gross weight of 
approximately 45 kg (99 lbs). As the airgun array is towed along the 
survey lines, the hydrophone streamer and/or OBSs will receive the 
returning acoustic signals and transfer the data to the on-board 
processing system.
    The Langseth is expected to depart Prince Rupert, British Columbia, 
Canada, on approximately 31 August, 2008 for the study area in the GOA 
(see Figure 1 of L-DEO's application). The airgun array is expected to 
operate for a total of ~200-250 hours. With OBS deployment and 
retrieval, the length of the survey will be ~18 days. The overall area 
within which the STEEP survey will take place is located at ~58-
60.5[deg] N, 138-146[deg] W (see Figure 1 of L-DEO's application). The 
proposed survey will be conducted in water depths from <100 m to >3,000 
m (<330 to>9,840 ft) entirely within the territorial waters and 
Exclusive Economic Zone (EEZ) of the United States. The exact dates of 
the activities depend upon logistics, as well as weather conditions 
and/or the need to repeat some lines if data quality is substandard.
    The primary marine seismic survey will consist of two long transect 
lines that will cross each other (Figure 1 of L-DEO's application). For 
the longer line paralleling the shoreline, a seismic reflection-
refraction profile will be shot using the hydrophone streamer as well 
as 25 OBSs deployed on the seafloor and 60 Texan seismometers deployed 
on land across the toe of the Bering Glacier. A reflection-refraction 
profile will also be obtained from the slightly shorter line that is 
perpendicular to the shoreline using the hydrophone streamer as well as 
17 OBSs; this line will be shot twice if time allows. Both of these 
lines will have a shot spacing of 50 m (164 ft, 20 seconds); if the 
onshore-offshore line is shot twice, the shot interval used during the 
second run will be 150 m (492 ft, 60 s). During the reflection-
refraction profiling, the airgun array will be towed at a depth of 9 m. 
In addition, two reflection-only 2-dimensional (2-D) seismic grids will 
be shot; the western grid is located approximately 150 km (93 mi) from 
shore whereas the eastern grid is located nearshore (see Figure 1 in L-
DEO's application). The shot spacing for these grids will be 50 m (164 
ft) and the airgun array will be towed at a depth of 9 m. No OBSs will 
be deployed during reflection-only profiling. There will be additional 
operations associated with equipment testing, startup, line changes, 
and repeat coverage of any areas where initial data quality is sub-
standard. In L-DEO's calculations, 25% has been added to the line total 
for those additional operations.
    The planned seismic survey (excluding the 25 percent contingency) 
will consist of 1909 km of survey lines including turns (see Figure 1 
in L-DEO's application). Most of this effort (923 km or 574 mi) will 
take place in intermediate water depths of 100-1,000 m and in water 
depths >1,000 m deep (812 km or 504 mi), and a smaller portion (174 km 
or 108 mi) will take place in water <100 m deep.
    All planned geophysical data acquisition activities will be 
conducted by L-DEO with on-board assistance by the scientists who have 
proposed the study. The scientific team is headed by Dr. Sean Gullick 
of the University of Texas at Austin Institute for Geophysics (UTIG) 
and also includes Drs. G. Christesen, P. Mann, and H. Van Avendonk of 
UTIG. The vessel will be self-contained, and the crew will live aboard 
the vessel for the entire cruise.
    In addition to the operations of the airgun array, a multibeam 
echosounder (MBES) will be operated from the Langseth continuously 
throughout the STEEP cruise. Also, a sub-bottom profiler (SBP) will be 
operated by the Langseth during most of the survey.

Vessel Specifications

    The Langseth has a length of 71.5 m (234.6 ft), a beam of 17 m 
(55.8 ft), and a maximum draft of 5.9 m (19.4 ft). The ship was 
designed as a seismic research vessel, with a propulsion system 
designed to be as quiet as possible to avoid interference with the 
seismic signals. The ship is powered by two Bergen BRG-6 diesel 
engines, each producing 3,550 hp, that drive the two propellers 
directly. Each propeller has four blades, and the shaft typically 
rotates at 750 rpm. The vessel also has an 800-hp bowthruster. The 
operation speed during seismic acquisition is typically 7.4-9.3 km/h 
(4-5 kt). When not towing seismic survey gear, the Langseth can cruise 
at 20-24 km/h (11-13 kt). The Langseth has a range of 25,000 km (15,534 
mi). The Langseth will also serve as the platform from which vessel-
based marine mammal (and sea turtle) observers (MMOs) will watch for 
animals before and during airgun operations.

Acoustic Source Specifications

Seismic Airguns
    During the proposed survey, the airgun array to be used will 
consist of 36 airguns, with a total volume of approximately 6,600 
in\3\. The airguns will consist of a mixture of Bolt 1500LL and 1900LL 
airguns. The airguns array will be configured as four identical linear 
arrays or ``strings'' (see Figure 2 in L-DEO's application). Each 
string will have ten airguns; the first and last airguns in each string 
are spaced 16 m (52.5 ft) apart. Nine airguns in each string will be 
fired simultaneously, while the tenth is kept in reserve as a spare, to 
be turned on in case of failure of another airgun. The four airgun 
strings will be distributed across an approximate area of 24 x 16 m 
(78.7 x 52.5 ft) behind the Langseth and will be towed approximately 
50-100 m (164-328 ft) behind the vessel at 9-m depth. The firing 
pressure of the array is 2,000 psi. The airgun array will fire in two 
modes: every 50 m (164 ft; 20 s) or every 150 m (492 ft; 60 s). During 
firing, a brief (approximately 0.1 s) pulse of sound is emitted. The 
airguns will be silent during the intervening periods.
    Because the actual source is a distributed sound source (36 
airguns) rather than a single point source, the highest sound levels 
measurable at any location in the water will be less than the nominal 
source level (265 dB re 1 microPa.m, peak to peak). In addition, the 
effective source level for sound propagating in near-horizontal 
directions will be substantially lower than the nominal source level 
applicable to downward propagation because of the directional nature of 
the sound from the airgun array.
    Sound propagation has been predicted by L-DEO for the 36-airgun 
array operating in deep, intermediate, and shallow water and for a 
single 1900LL 40 in\3\ airgun (which will be used during power downs), 
in relation to distance and direction from the airguns (See Table 1). A 
detailed description of L-DEO's modeling effort is provided in Appendix 
A of the application.
Multibeam Echosounder
    The Simrad EM120 operates at 11.25-12.6 kHz and is hull-mounted on 
the Langseth. The beamwidth is 1[deg] fore-aft and 150[deg] 
athwartship. The maximum source level is 242 dB re 1 microPa (rms; 
Hammerstad, 2005). For deep-water operation, each ``ping'' consists of 
nine successive fan-shaped transmissions, each 15 ms in duration and 
each ensonifying a section that extends 1[deg] fore-aft. The nine 
successive

[[Page 45409]]

transmissions span an overall cross-track angular extent of about 
150[deg], with 16 ms gaps between the pulses for successive sectors. A 
receiver in the overlap area between the two sectors would receive two 
15-ms pulses separated by a 16-ms gap. In shallower water, the pulse 
duration is reduced to 5 or 2 ms, and the number of transmit beams is 
also reduced. The ping interval varies with water depth, from 
approximately 5 s at 1,000 m (3,280 ft) to 20 s at 4,000 m (13,123 ft; 
Kongsberg Maritime, 2005).
Sub-bottom Profiler
    The SBP is normally operated to provide information about the 
sedimentary features and the bottom topography that is simultaneously 
being mapped by the MBES. The energy from the SBP is directed downward 
by a 3.5 kHz transducer in the hull of the Langseth. The output varies 
with water depth from 50 watts in shallow water to 800 watts in deep 
water. The pulse interval is 1 s, but a common mode of operation is to 
broadcast five pulses at 1-s intervals followed by a 5-s pause.

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                                                                                                        Predicted RMS Distances (m)
        Source and Volume              Tow Depth (m)            Water Depth      -----------------------------------------------------------------------
                                                                                          190 dB                  180 dB                  160 dB
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Single Bolt airgun                ......................  Deep                    12                      40                      385
                                                         -----------------------------------------------------------------------------------------------
                                  9                       Intermediate            18                      60                      578
                                                         -----------------------------------------------------------------------------------------------
40 in\3\                          ......................  Shallow                 150                     296                     1050
--------------------------------------------------------------------------------------------------------------------------------------------------------
4 strings                         ......................  Deep                    300                     950                     6000
                                                         -----------------------------------------------------------------------------------------------
36 airguns                        9                       Intermediate            450                     1425                    6667
                                                         -----------------------------------------------------------------------------------------------
6600 in\3\                        ......................  Shallow                 2182                    3694                    8000
--------------------------------------------------------------------------------------------------------------------------------------------------------
Table 1. Predicted distances to which sound levels [gteqt]190, 180, and 160 dB re 1 microPa might be received in shallow (<100 m; 328 ft), intermediate
  (100-1,000 m; 328-3,280 ft), and deep (>1,000 m; 3,280 ft) water during the Central American SubFac and STEEP Gulf of Alaska survey.

    Because the predictions in Table 1 are based in part on empirical 
correction factors derived from acoustic calibration of different 
airgun configurations than those to be used on the Langseth (cf. 
Tolstoy et al., 2004a,b), L-DEO conducted an acoustic calibration study 
of the Langseth's 36-airgun (approximately 6,600 in\3\) array in late 
2007/early 2008 in the Gulf of Mexico (LGL Ltd. 2006). Distances where 
sound levels (e.g., 190, 180, and 160 dB re 1 microPa rms) were 
received in deep, intermediate, and shallow water will be determined 
for various airgun configurations. Acoustic data analysis is ongoing. 
After, analysis, the empirical data from the 2007/2008 calibration 
study will be used to refine the exclusion zones proposed above for use 
during the STEEP cruise, if the data are appropriate and available for 
use at the time of the survey.

Description of Marine Mammals in the Activity Area

    A total of 18 cetacean species, 3 species of pinnipeds, and the sea 
otter are known to or could occur in the GOA study area (see Table 2 of 
the application; Angliss and Outlaw, 2007). Several of the species are 
listed as Endangered under the U.S. Endangered Species Act (ESA), 
including the humpback, sei, fin, blue, North Pacific right, and sperm 
whale, sea otter, and the western stock of Steller sea lions. The 
eastern stock of Steller sea lions is listed as Threatened. The 
southeast Alaska Distinct Population Segment of northern sea otters are 
also listed as Threatened. There is little information on the 
distribution of marine mammals inhabiting the waters offshore of SE 
Alaska or the eastern GOA, although a few reports are available (e.g., 
Buckland et al., 1993; Hobbs and Lerczak, 1993; Straley et al. 1995; 
Calambokidis et al., 1997; MacLean and Koski, 2005; Angliss and Outlaw, 
2007).
    The marine mammals that occur in the proposed survey area belong to 
four taxonomic groups: odontocetes (toothed cetaceans such as 
dolphins), mysticetes (baleen whales), pinnipeds (seals and sea lions), 
and fissipeds (the sea otter). Cetaceans and pinnipeds are managed by 
NMFS and are the subject of this IHA application. Several of the 18 
cetacean species are common in the area (see below). Of the three 
species of pinnipeds that potentially could occur in the study area, 
only the Steller sea lion and harbor seal are likely to be present. The 
northern fur seal inhabits the Bering Sea during the summer, and is 
generally found in SE Alaska in low numbers during the winter and 
during the northward migration in the spring. Sea otters are managed by 
the U.S. Fish and Wildlife Service (USFWS). Informal consultation with 
the USFWS is being sought for sea otters.
    Information on the occurrence, distribution, population size, 
habitat, and conservation status for each of the 21 marine mammal 
species that are likely to occur in the proposed project area is 
presented in Table 5 of L-DEO's application and is reprinted in part 
here as Table 2.
    Based on a compilation of data from 1979 to 2001, many cetaceans 
and pinnipeds occur within the EEZ in both oceanic and coastal waters. 
However, beaked, sperm, dwarf/pygmy sperm, and baleen whales (except 
for the humpback) occur predominantly in oceanic waters (May-Collado et 
al., 2005). Bottlenose and pantropical spotted dolphins, as well as the 
humpback whale, tend to be coastal.
    Table 2 below outlines the cetacean and pinniped species, their 
habitat and abundance in the proposed project area, and the requested 
take levels. Additional information regarding the distribution of these 
species expected to be found in the project area and how the estimated 
densities were calculated may be found in L-DEO's application.

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           Species                   Habitat         Abundance (Alaska)   Regional Abundance        ESA \1\
----------------------------------------------------------------------------------------------------------------
Odontocetes
------------------------------                                                               -------------------

[[Page 45410]]

 
Sperm whale (Physeter          Pelagic              159 \4\              24,000 \5\           EN
 macrocephalus)
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Cuvier's beaked whale          Pelagic              N.A.                 20,000 \6\           N.L.
 (Ziphius cavirostris)
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Baird's beaked whale           Pelagic              N.A.                 6,000 \7\            N.L.
 (Berardius bairdii)
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Stejneger's beaked whale       Likely Pelagic       N.A.                 N.A.                 N.L.
 (Mesoplodon stejnegeri)
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Beluga whale (Delphinapterus   Coastal & Ice Edges  366 \8\              N.A.                 N.L.
 leucas)
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Pacific white-sided dolphin    Pelagic, Shelf,      26,880 \9\           931,000 \10\         N.L.
 (Lagenorhynchus obliquidens)   Coastal
----------------------------------------------------------------------------------------------------------------
Risso's dolphin (Grampus       Pelagic, Shelf,      N.A.                 16,066 \11\          N.L.
 griseus)                       Coastal
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Killer whale (Orcinus orca)    Pelagic, Shelf,      1,975 \12\           8,500 \13\           N.L.
                                Coastal
----------------------------------------------------------------------------------------------------------------
Short-finned pilot whale       Pelagic, Shelf,      N.A.                 160,200 \6\          N.L.
 (Globicephala macrorhynchus)   Coastal
----------------------------------------------------------------------------------------------------------------
Harbor Porpoise (Phocoena      Coastal              17,076 \14\          202,988 \16\         N.L.
 phocoena)                                          41,854 \15\
----------------------------------------------------------------------------------------------------------------
Dall's Porpoise (Phocoenoides  Pelagic & Shelf      83,400 \17\          1,186,000 \18\       N.L.
 dalli)
----------------------------------------------------------------------------------------------------------------
Mysticetes
------------------------------                                                               -------------------
Humpback whale (Megaptera      Coastal & Banks      2,644 \21\           >6,000 \22\          EN
 novaeangliae)
----------------------------------------------------------------------------------------------------------------
Minke whale (Balaenoptera      Coastal & Shelf      1,232 \21\           9,000 \23\           N.L.
 acutorostrata)
----------------------------------------------------------------------------------------------------------------
Gray whale (Eschrichtius       Coastal              N.A.                 18,813 \20\          N.L.
 robustus)
----------------------------------------------------------------------------------------------------------------
Sei whale (Balaenoptera        Pelagic              N.A.                 7,260-12,620 \22\    EN
 borealis)
----------------------------------------------------------------------------------------------------------------
Fin whale (Balaenoptera        Pelagic              1,652 \24\           13,620-18,680 \22\   EN
 physalus)
----------------------------------------------------------------------------------------------------------------
Blue whale (Balaenoptera       Pelagic, Shelf,      N.A.                 1,744 \11\           EN
 musculus)                      Coastal
----------------------------------------------------------------------------------------------------------------
North Pacific right whale      Coastal & Shelf      N.A.                 100-200 \19\         EN
 (Eubalaena japonica)
----------------------------------------------------------------------------------------------------------------
Pinnipeds
------------------------------                                                               -------------------
Northern fur seal              Pelagic, Breeds      N.A.                 721,935 \25\         N.L.
 (Callorhinus ursinus)          Coastally
----------------------------------------------------------------------------------------------------------------
Steller sea lion (Eumetopias   Coastal              47,885 \26\          N.A.                 T
 jubatus)                                           44,780 \27\                               EN
----------------------------------------------------------------------------------------------------------------
Harbor seal (Phoca vitulina    Coastal              180,017 \28\         N.A.                 N.L.
 richardsi)
----------------------------------------------------------------------------------------------------------------
Table 2. The habitat, abundance, and conservation status of marine mammals inhabiting the proposed study area in
  the Gulf of Alaska. Regional abundance estimates are also given, usually for the Northeastern Pacific Ocean or
  the U.S. West Coast.
Note: N.A. = Not available or not applicable.
\1\ U.S. Endangered Species Act. En = Endangered; T = Threatened; N.L. = Not Listed.
\2\ IUCN Red List of Threatened Species (2007). Codes for IUCN classifications: CR = Critically Endangered; EN =
  Endangered; VU = Vulnerable; LR = Lower Risk (-cd = Conservation Dependent; -nt = Near Threatened; -ic = Least
  Concern); DD = Data Deficient; NL = Not Listed.
\3\ Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) (UNEP-WCMC 2007). I
  and II are CITES Appendices; NL = Not Listed.

[[Page 45411]]

 
\4\ Western GOA and eastern Aleutians (Zerbini et al., 2004).
\5\ Eastern temperate North Pacific (Whitehead, 2002).
\6\ Eastern Tropical Pacific (Wade and Gerrodette, 1993).
\7\ Western North Pacific (Reeves and Leatherwood, 1994; Kasuya, 2002).
\8\ Cook Inlet stock (Rugh et al., 2005a).
\9\ GOA (Angliss and Outlaw, 2007).
\10\ North Pacific Ocean (Buckland et al., 1993).
\11\ California/Oregon/Washington (Carretta et al. 2007).
\12\ Minimum abundance in Alaskan waters, includes 1,339 resident and 636 transient (Angliss and Outlaw, 2007).
\13\ Eastern Tropical Pacific (Ford, 2002).
\14\ SE Alaska stock (Angliss and Outlaw, 2007).
\15\ GOA stock (Angliss and Outlaw 2007).
\16\ Western North Pacific Ocean (totals from Carretta et al., 2007 and Angliss and Outlaw, 2007).
\17\ Alaska stock (Angliss and Outlaw, 2007).
\18\ North Pacific Ocean and Bering Sea (Houk and Jefferson, 1999).
\19\ Eastern North Pacific (Wada, 1973).
\20\ Mean of 2000-2001 and 2001-2002 abundance estimates for eastern North Pacific (Angliss and Outlaw, 2007).
\21\ Western GOA and eastern Aleutians (Zerbini et al., 2006).
\22\ North Pacific Ocean (Carretta et al., 2007).
\23\ North Pacific Ocean (Wada, 1976).
\24\ Central waters of western Alaska and eastern and central Aleutian Islands (Angliss and Outlaw, 2007).
\25\ Abundance for Eastern Pacific Stock (Angliss and Outlaw, 2007).
\26\ Eastern U.S. Stock (Angliss and Outlaw, 2007).
\27\ Western U.S. Stock (Angliss and Outlaw, 2007).
\28\ Alaska statewide (Angliss and Outlaw, 2007).
\29\ Abundance estimate for SE Alaska stock (USFWS 2002 in Angliss and Outlaw, 2007).
\30\ Abundance estimate Southcentral Alaska (USFWS 2002 in Angliss and Outlaw, 2007).
\31\ SW Alaska stock (USFWS 2002 in Angliss and Outlaw, 2007).

Potential Effects on Marine Mammals

Potential Effects of Airguns

    The effects of sounds from airguns might include one or more of the 
following: tolerance, masking of natural sounds, behavioral 
disturbances, and 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). With the possible exception of some 
cases of temporary threshold shift in harbor seals, it is unlikely that 
the project would result in any cases of temporary or especially 
permanent hearing impairment, or any significant non-auditory physical 
or physiological effects. Some behavioral disturbance is expected, but 
this would be localized and short-term.
    The rms (root mean square) received levels that are used as impact 
criteria for marine mammals are not directly comparable to the peak or 
peak-to-peak values normally used to characterize source levels of 
airgun arrays. The measurement units used to describe airgun sources, 
peak or peak-to-peak decibels, are always higher than the rms decibels 
referred to in biological literature. A measured received level of 160 
dB rms in the far field would typically correspond to a peak 
measurement of approximately 170 to 172 dB, and to a peak-to-peak 
measurement of approximately 176 to 178 dB, as measured for the same 
pulse received at the same location (Greene, 1997; McCauley et al., 
1998, 2000a). The precise difference between rms and peak or peak-to-
peak values depends on the frequency content and duration of the pulse, 
among other factors. However, the rms level is always lower than the 
peak or peak-to-peak level for an airgun-type source.
Tolerance
    Numerous studies have shown that pulsed sounds from airguns are 
often readily detectable in the water at distances of many kilometers. 
For a summary of the characteristics of airgun pulses, see Appendices B 
) of L-DEO's application. Numerous studies have shown that marine 
mammals at distances more than a few kilometers from operating seismic 
vessels often show no apparent response see Appendix C (e) of the 
application. 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 mammal group. Although 
various baleen whales, toothed whales, and (less frequently) pinnipeds 
have been shown to react behaviorally to airgun pulses under some 
conditions, at other times, mammals of all three types have shown no 
overt reactions. In general, pinnipeds usually seem to be more tolerant 
of exposure to airgun pulses than are cetaceans, with relative 
responsiveness of baleen and toothed whales being variable.
Masking
    Obscuring of sounds of interest by interfering sounds, generally at 
similar frequencies, is known as masking. Masking effects of pulsed 
sounds (even from large arrays of airguns) on marine mammal calls and 
other natural sounds are expected to be limited, although there are few 
specific data of relevance. Because of the intermittent nature and low 
duty cycle of seismic pulses, animals can emit and receive sounds in 
the relatively quiet intervals between pulses. Some baleen and toothed 
whales are known to continue calling in the presence of seismic pulses. 
The airgun sounds are pulsed, with quiet periods between the pulses, 
and whale calls often can be heard between the seismic pulses 
(Richardson et al., 1986; McDonald et al., 1995; Greene et al., 1999; 
Nieukirk et al., 2004; Smultea et al., 2004). Although there has been 
one report that sperm whales cease calling when exposed to pulses from 
a very distant seismic ship (Bowles et al., 1994), a more recent study 
reports that sperm whales off northern Norway continued calling in the 
presence of seismic pulses (Madsen et al., 2002). That has also been 
shown during recent work in the Gulf of Mexico and Caribbean Sea 
(Smultea et al., 2004; Tyack et al., 2006). Masking effects of seismic 
pulses are expected to be negligible in the case of the small 
odontocetes given the intermittent nature of seismic pulses. Dolphins 
and porpoises commonly are heard calling while airguns are operating 
(Gordon et al., 2004; Smultea et al., 2004; Holst et al., 2005a,b). 
Also, the sounds important to small odontocetes are predominantly at 
much higher frequencies than the airgun sounds, thus further limiting 
the potential for masking. Masking effects, in general, are discussed 
further in Appendix B (d) of L-DEO's application.

[[Page 45412]]

Disturbance Reactions
    Disturbance includes a variety of effects, including subtle changes 
in behavior, more conspicuous changes in activities, 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. If a marine mammal responds to an underwater sound by 
changing its behavior or moving a small distance, the response may or 
may not rise to the level of ``harassment,'' let alone affect the stock 
or the species as a whole. However, if a sound source displaces marine 
mammals from an important feeding or breeding area for a prolonged 
period, impacts on animals or on the stock or species could potentially 
be significant. 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 are likely to be present within a 
particular distance of industrial activities, or exposed to a 
particular level of industrial sound. This practice potentially 
overestimates the numbers of marine mammals that are affected in some 
biologically-important manner.
    The sound exposure thresholds that affect marine mammals 
behaviorally are based on behavioral observations during studies of 
several species. However, information is lacking for many species. 
Detailed studies have been done on humpback, gray, and bowhead whales 
and on ringed seals. Less detailed data are available for some other 
species of baleen whales, sperm whales, and small toothed whales.
    Baleen Whales - Baleen whales generally tend to avoid operating 
airguns, but avoidance radii are quite variable. Whales are often 
reported to show no overt reactions to pulses from large arrays of 
airguns at distances beyond a few kilometers, even though the airgun 
pulses remain well above ambient noise levels out to much longer 
distances. However, as reviewed in Appendix B (e) of L-DEO's 
application, baleen whales exposed to strong noise pulses from airguns 
often react by deviating from their normal migration route and/or 
interrupting their feeding activities and moving away from the sound 
source. In the case of the migrating gray and bowhead whales, the 
observed changes in behavior appeared to be of little or no biological 
consequence to the animals. They simply avoided the sound source by 
displacing their migration route to varying degrees, but within the 
natural boundaries of the migration corridors.
    Studies of gray, bowhead, and humpback whales have determined that 
received levels of pulses in the 160-170 dB re 1 microPa rms range seem 
to cause obvious avoidance behavior in a substantial fraction of the 
animals exposed. In many areas, seismic pulses from large arrays of 
airguns diminish to those levels at distances ranging from 4.5-14.5 km 
(2.8-9 mi) from the source. A substantial proportion of the baleen 
whales within those distances may show avoidance or other strong 
disturbance reactions to the airgun array. Subtle behavioral changes 
sometimes become evident at somewhat lower received levels.
    Responses of humpback whales to seismic surveys have been studied 
during migration and on the summer feeding grounds, and there has also 
been discussion of effects on the Brazilian wintering grounds. McCauley 
et al. (1998, 2000) studied the responses of humpback whales off 
Western Australia to a full-scale seismic survey with a 16-airgun, 
2,678-in\3\ array, and to a single 20-in\3\ airgun with a source level 
of 227 dB re 1 microPa m peak-to-peak. McCauley et al. (1998) 
documented that initial avoidance reactions began at 5-8 km (3.1-5 mi) 
from the array, and that those reactions kept most pods approximately 
3-4 km (1.9-2.5 mi) from the operating seismic boat. McCauley et al. 
(2000) noted localized displacement during migration of 4-5 km (2.5-3.1 
mi) by traveling pods and 7-12 km (4.3-7.5 mi) by cow-calf pairs. 
Avoidance distances with respect to the single airgun were smaller (2 
km (1.2 mi)) but consistent with the results from the full array in 
terms of received sound levels. Mean avoidance distance from the airgun 
corresponded to a received sound level of 140 dB re 1 microPa (rms); 
that was the level at which humpbacks started to show avoidance 
reactions to an approaching airgun. The standoff range, i.e., the 
closest point of approach of the whales to the airgun, corresponded to 
a received level of 143 dB re 1 microPa (rms). However, some individual 
humpback whales, especially males, approached within distances of 100-
400 m (328-1,312 ft), where the maximum received level was 179 dB re 1 
microPa (rms).
    Humpback whales on their summer feeding grounds in southeast 
summering 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 
150-169 dB re 1 microPa on an approximate rms basis. 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 
microPa on an approximate rms basis.
    It has been suggested that South Atlantic humpback whales wintering 
off Brazil may be displaced or even strand upon exposure to seismic 
surveys (Engel et al., 2004). The evidence for this was circumstantial, 
subject to alternative explanations (IAGC 2004), and not consistent 
with results from 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).
    Results from bowhead whales show that responsiveness of baleen 
whales to seismic surveys can be quite variable depending on the 
activity (migrating vs. feeding) of the whales. Bowhead whales 
migrating west across the Alaskan Beaufort Sea in autumn, in 
particular, are unusually responsive, with substantial avoidance 
occurring out to distances of 20 30 km (12.4-18.6 mi) from a medium-
sized airgun source, where received sound levels were on the order of 
130 dB re 1 microPa (rms) (Miller et al., 1999; Richardson et al., 
1999; see Appendix B (e) of L-DEO's application). However, more recent 
research on bowhead whales (Miller et al., 2005a; Harris et al., 2007) 
corroborates earlier evidence that, during the summer feeding season, 
bowheads are not as sensitive to seismic sources. In summer, bowheads 
typically begin to show avoidance reactions at a received level of 
about 160 170 dB re 1 microPa (rms) (Richardson et al., 1986; Ljungblad 
et al., 1988; Miller et al., 2005a). Nonetheless, statistical analysis 
showed evidence of subtle changes in surfacing, respiration and diving 
cycles when feeding bowheads were exposed to lower-level pulses from 
distant seismic operations (Richardson et al., 1986).
    Reactions of migration 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. Malme et al. (1986, 1988) estimated, based on small sample sizes, 
that 50 percent of feeding gray whales ceased feeding at an average 
received pressure level of 173 dB re 1 microPa on an (approximate) rms 
basis, and that 10 percent of feeding whales interrupted feeding at 
received levels of 163 dB. Those findings were generally consistent 
with the results of experiments conducted on larger numbers of gray 
whales that were

[[Page 45413]]

migrating along the California coast (Malme et al., 1984; Malme and 
Miles, 1985), and with observations of Western Pacific gray whales 
feeding off Sakhalin Island, Russia, when a seismic survey was underway 
just offshore of their feeding area (Gailey et al., 2007; Johnson et 
al., 2007; Yazvenko et al. 2007a,b).
    Various species of Balaenoptera (blue, sei, fin, and minke whales) 
have occasionally been reported in areas ensonified by airgun pulses. 
Sightings by observers on seismic vessels off the United Kingdom from 
1997 to 2000 suggest that, at times of good sightability, numbers of 
rorquals seen are similar when airguns are shooting and not shooting 
(Stone, 2003; Stone and Tasker, 2006). Although individual species did 
not show any significant displacement in relation to seismic activity, 
all baleen whales combined were found to remain significantly further 
from the airguns during shooting compared with periods without shooting 
(Stone, 2003; Stone and Tasker, 2006). In a study off Nova Scotia, 
Moulton and Miller (in press) found only a little or no difference in 
sighting rates and initial sighting distances of balaenopterid whales 
when airguns were operating vs. silent. However, there were indications 
that these whales were more likely to be moving away when seen during 
airgun operations.
    Data on short-term reactions (or lack of reactions) of cetaceans to 
impulsive noises do not necessarily provide information about long-term 
effects. It is not known whether impulsive noises affect reproductive 
rate or distribution and habitat use in subsequent days or years. 
However, gray whales continued to migrate annually along the west coast 
of North America despite intermittent seismic exploration and much ship 
traffic in that area for decades (see Appendix A in Malme et al., 
1984). The western Pacific gray whale population did not seem affected 
by a seismic survey in its feeding ground during a prior year (Johnson 
et al., 2007). Bowhead whales continued to travel to the eastern 
Beaufort Sea each summer despite seismic exploration in their summer 
and autumn range for many years (Richardson et al., 1987). In any 
event, brief exposures to sound pulses from the proposed airgun source 
are highly 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, a systematic study on sperm 
whales has been done ( Jochens and Biggs, 2003; Tyack et al., 2003; 
Jochens et al., 2006; Miller et al., 2006), and there is an increasing 
amount of information about responses of various odontocetes to seismic 
surveys based on monitoring studies (e.g., Stone, 2003; Smultea et al., 
2004; Moulton and Miller, 2005; Bain and Williams, 2006; Holst et al., 
2006; Stone and Tasker, 2006).
    Seismic operators and marine mammal observers sometimes see 
dolphins and other small toothed whales near operating airgun arrays, 
but in general there seems to be a tendency for most delphinids to show 
some limited avoidance of seismic vessels operating large airgun 
systems. However, 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 airgun arrays are firing. Nonetheless, there have been 
indications that small toothed whales sometimes 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., Goold, 
1996a,b,c; Calambokidis and Osmek, 1998; Stone, 2003; Stone and Tasker, 
2006). In most cases, the avoidance radii for delphinids appear to be 
small, on the order of 1 km (0.62 mi) or less. The beluga may be a 
species that (at least at times) shows long-distance avoidance of 
seismic vessels. Aerial surveys during seismic operations in the 
southeastern Beaufort Sea recorded much lower sighting rates of beluga 
whales within 10-20 km (6.2-12.4 mi) of an active seismic vessel. These 
results were consistent with the low number of beluga sightings 
reported by observers aboard the seismic vessel, suggesting that some 
belugas might be avoiding the seismic operations at distances of 10-20 
km (6.2-12.4 mi) (Miller et al., 2005a).
    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; Finneran and Schlundt, 2004). The animals tolerated high received 
levels of sound (pk-pk level >200 dB re 1 microPa) before exhibiting 
aversive behaviors. For pooled data at 3, 10, and 20 kHz, sound 
exposure levels during sessions with 25, 50, and 75 percent altered 
behavior were 180, 190, and 199 dB re 1 microPa\2\, respectively 
(Finneran and Schlundt, 2004).
    Results for porpoises depend on species. Dall's porpoises seem 
relatively tolerant of airgun operations (MacLean and Koski, 2005) and, 
during a survey with a large airgun array, tolerated higher noise 
levels than did harbor porpoises and gray whales (Bain and Williams, 
2006). However, Dall's porpoises do respond to the approach of large 
airgun arrays by moving away (Calambokidis and Osmek, 1998; Bain and 
Williams, 2006). The limited available data suggest that harbor 
porpoises show stronger avoidance (Stone, 2003; Bain and Williams, 
2006; Stone and Tasker, 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 
in general (Richardson et al., 1995; Southall et al. 2007).
    Most studies of sperm whales exposed to airgun sounds indicate that 
this species shows considerable tolerance of airgun pulses. In most 
cases, the whales do not show strong avoidance and continue to call 
(see Appendix B of L-DEO's application). However, controlled exposure 
experiments in the Gulf of Mexico indicate that foraging effort is 
somewhat reduced upon exposure to airgun pulses from a seismic vessel 
operating in the area, and there may be a delay in diving to foraging 
depth (Miller et al., 2006; Tyack et al., 2006).
    There are no specific data on the behavioral reactions of beaked 
whales to seismic surveys. Most beaked whales tend to avoid approaching 
vessels of other types (Wursig et al., 1998). They may also dive for an 
extended period when approached by a vessel (Kasuya, 1986). It is 
likely that these beaked whales would normally show strong avoidance of 
an approaching seismic vessel, but this has not been documented 
explicitly.
    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 (Appendix B of L-DEO's 
application).
    Pinnipeds - Pinnipeds are not likely to show a strong avoidance 
reaction to the airgun sources that will be used. Visual monitoring 
from seismic vessels, usually employing larger sources, has shown only 
slight (if any) avoidance of airguns by pinnipeds, and only slight (if 
any) changes in behavior (see Appendix B(e) of L-DEO's application). 
Ringed seals frequently do not avoid the area within a few hundred 
meters of operating airgun arrays (Harris et al., 2001; Moulton and 
Lawson, 2002; Miller et al., 2005a). However, initial telemetry work 
suggests that avoidance and other behavioral reactions by two

[[Page 45414]]

other species of seals to small airgun sources may at times be stronger 
than evident to date from visual studies of pinniped reactions to 
airguns (Thompson et al., 1998). Even if reactions of any pinnipeds 
that might be encountered in the present study area are as strong as 
those evident in the telemetry study, reactions are expected to be 
confined to relatively small distances and durations, with no long-term 
effects on pinniped individuals or populations.
    Additional details on the behavioral reactions (or the lack 
thereof) by all types of marine mammals to seismic vessels can be found 
in Appendix B (e) of L-DEO's application.
Hearing Impairment and Other Physical Effects
    Temporary or permanent hearing impairment is a possibility when 
marine mammals are exposed to very strong sounds, but there has been no 
specific documentation of this for marine mammals exposed to sequences 
of airgun pulses.
    NMFS will be developing new noise exposure criteria for marine 
mammals that take account of the now-available scientific data on TTS, 
the expected offset between the TTS and permanent threshold shift (PTS) 
thresholds, differences in the acoustic frequencies to which different 
marine mammal groups are sensitive, and other relevant factors. 
Detailed recommendations for new science-based noise exposure criteria 
were published in early 2008 (Southall et al., 2007).
    Several aspects of the planned monitoring and mitigation measures 
for this project (see below) are designed to detect marine mammals 
occurring near the airguns to avoid exposing them to sound pulses that 
might, at least in theory, cause hearing impairment. In addition, many 
cetaceans are likely to show some avoidance of the area with high 
received levels of airgun sound (see above). In those cases, the 
avoidance responses of the animals themselves will reduce or (most 
likely) avoid any possibility of hearing impairment.
    Non-auditory physical effects may also occur in marine mammals 
exposed to strong underwater pulsed sound. Possible types of non-
auditory physiological effects or injuries that theoretically might 
occur in mammals close to a strong sound source include stress, 
neurological effects, bubble formation, resonance effects, and other 
types of organ or tissue damage. It is possible that some marine mammal 
species (i.e., beaked whales) may be especially susceptible to injury 
and/or stranding when exposed to strong pulsed sounds. However, as 
discussed below, there is no definitive evidence that any of these 
effects occur even for marine mammals in close proximity to large 
arrays of airguns. It is especially unlikely that any effects of these 
types would occur during the present project given the brief duration 
of exposure of any given mammal and the proposed monitoring and 
mitigation measures (see below). The following subsections discuss in 
somewhat more detail the possibilities of Temporary Threshold Shift 
(TTS), Permanent Threshold Shift (PTS), and non-auditory physical 
effects.
    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).
    For toothed whales exposed to single short pulses, the TTS 
threshold appears to be, to a first approximation, a function of the 
energy content of the pulse (Finneran et al., 2002, 2005). Given the 
available data, the received level of a single seismic pulse (with no 
frequency weighting) might need to be approximately 186 dB re 1 
microPa\2.\s (i.e., 186 dB SEL or approximately 221-226 dB pk-pk) in 
order to produce brief, mild TTS. Exposure to several strong seismic 
pulses that each have received levels near 175-180 dB SEL might result 
in slight TTS in a small odontocete, assuming the TTS threshold is (to 
a first approximation) a function of the total received pulse energy. 
The distance from the Langseth's airguns at which the received energy 
level (per pulse) would be expected to be [gteqt]175-180 dB SEL are the 
distances shown in the 190 dB re 1 microPa (rms) column in Table 3 of 
L-DEO's application and Table 1 above (given that the rms level is 
approximately 10-15 dB higher than the SEL value for the same pulse). 
Seismic pulses with received energy levels [gteqt]175-180 dB SEL (190 
dB re 1 microPa (rms)) are expected to be restricted to radii no more 
than 140-200 m (459-656 ft) around the airguns. The specific radius 
depends on the number of airguns, the depth of the water, and the tow 
depth of the airgun array. For an odontocete closer to the surface, the 
maximum radius with [gteqt]175-180 dB SEL or [gteqt]190 dB re 1 microPa 
(rms) would be smaller.
    The above TTS information for odontocetes is derived from studies 
on the bottlenose dolphin and beluga. There is not published TTS 
information for other types of cetaceans. However, preliminary evidence 
from harbor porpoise exposed to airgun sound suggests that its TTS 
threshold may have been lower (Lucke et al. 2007).
    For baleen whales, there are no data, direct or indirect, on levels 
or properties of sound required to induce TTS. The frequencies to which 
baleen whales are most sensitive are lower than those for odontocetes, 
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. In any 
event, no cases of TTS are expected given three considerations: (1) the 
relatively low abundance of baleen whales expected in the planned study 
areas; (2) the strong likelihood that baleen whales would avoid the 
approaching airguns (or vessel) before being exposed to levels high 
enough for there to be any possibility of TTS; and (3) the mitigation 
measures that are planned.
    In pinnipeds, TTS thresholds associated with exposure to brief 
pulses (single or multiple) of underwater sound have not been measured. 
Initial evidence from prolonged (non-pulse) exposures suggested that 
some pinnipeds may incur TTS at somewhat lower received levels than do 
small odontocetes exposed for similar durations (Kastak et al., 1999, 
2005; Ketten et al., 2001; Au et al., 2000). The TTS threshold for 
pulsed sounds has been indirectly estimated as being an SEL of 
approximately 171 dB re 1 microPa\2.\ s (Southall et al., 2007), which 
would be equivalent to a single pulse with received level approximately 
181-186 re 1 microPa (rms), or a series of pulses for which the highest 
rms values are a few dB lower. Corresponding values for California sea 
lions and northern elephant seals are likely to be higher (Kastak et 
al., 2005).
    A marine mammal within a radius of less than 100 m (328 ft) around 
a typical

[[Page 45415]]

large array of operating airguns might be exposed to a few seismic 
pulses with levels of greater than or equal to 205 dB, and possibly 
more pulses if the mammal moved with the seismic vessel. (As noted 
above, most cetacean species tend to avoid operating airguns, although 
not all individuals do so.) In addition, ramping up airgun arrays, 
which is standard operational protocol for large airgun arrays, should 
allow cetaceans to move away form the seismic source and to avoid being 
exposed to the full acoustic output of the airgun array. Even with a 
large airgun array, it is unlikely that the cetaceans would be exposed 
to airgun pulses at a sufficiently high level for a sufficiently long 
period to cause more than mild TTS, given the relative movement of the 
vessel and the marine mammal. The potential for TTS is much lower in 
this project. With a large array of airguns, TTS would be most likely 
in any odontocetes that bow-ride or otherwise linger near the airguns. 
While bow-riding, odontocetes would be at or above the surface, and 
thus not exposed to strong pulses given the pressure-release effect at 
the surface. However, bow-riding animals generally dive below the 
surface intermittently. If they did so while bow-riding near airguns, 
they would be exposed to strong sound pulses, possibly repeatedly. If 
some cetaceans did incur TTS through exposure to airgun sounds, this 
would very likely be mild, temporary, and reversible.
    To avoid the potential for injury, NMFS has determined that 
cetaceans and pinnipeds should not be exposed to pulsed underwater 
noise at received levels exceeding, respectively, 180 and 190 dB re 1 
microPa (rms). As summarized above, data that are now available imply 
that TTS is unlikely to occur unless odontocetes (and probably 
mysticetes as well) are exposed to airgun pulses stronger than 180 dB 
re 1 microPa (rms).
    Permanent Threshold Shift - When PTS occurs, there is physical 
damage to the sound receptors in the ear. In some cases, there can be 
total or partial deafness, while in other cases, the animal has an 
impaired ability to hear sounds in specific frequency ranges.
    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 TTS, there has been further speculation about the 
possibility that some individuals occurring very close to airguns might 
incur PTS. Single or occasional occurrences of mild TTS are not 
indicative of permanent auditory damage in terrestrial mammals. 
Relationships between TTS and PTS thresholds have not been studied in 
marine mammals, but are assumed to be similar to those in humans and 
other terrestrial mammals. PTS might occur at a received sound level at 
least several decibels above that inducing mild TTS if the animal were 
exposed to strong sound pulses with rapid rise time (see Appendix B (f) 
of L-DEO's application). The specific difference between the PTS and 
TTS thresholds has not been measured for marine mammals exposed to any 
sound type. However, 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.
    On an SEL basis, Southall et al. (2007) estimated that received 
levels would need to exceed the TTS threshold by at least 15 dB for 
there to be risk of PTS. Thus, for cetaceans they estimate that the PTS 
threshold might be a cumulative SEL (for the sequence of received 
pulses) of approximately 198 dB re 1 microPa\2.\s. Additional 
assumptions had to be made to derive a corresponding estimate for 
pinnipeds. Southall et al. (2007) estimate that the PTS threshold could 
be a cumulative SEL of approximately 186 dB 1 Pa2 s in the harbor seal; 
for the California sea lion and northern elephant seal the PTS 
threshold would probably be higher. Southall et al. (2007) also note 
that, regardless of the SEL, there is concern about the possibility of 
PTS if a cetacean or pinniped receives one or more pulses with peak 
pressure exceeding 230 or 218 dB re 1 microPa (3.2 bar\.\ m, 0-pk), 
which would only be found within a few meters of the largest (360-
in\3\) airguns in the planned airgun array (Caldwell and Dragoset, 
2000). A peak pressure of 218 dB re 1 microPa could be received 
somewhat farther away; to estimate that specific distance, one would 
need to apply a model that accurately calculates peak pressures in the 
near-field around an array of airguns.
    Given the higher level of sound necessary to cause PTS as compared 
with TTS, it is considerably less likely that PTS could occur. In fact, 
even the levels immediately adjacent to the airguns may not be 
sufficient to induce PTS, especially because a mammal would not be 
exposed to more than one strong pulse unless it swam immediately 
alongside the airgun for a period longer than the inter-pulse interval. 
Baleen whales generally avoid the immediate area around operating 
seismic vessels, as do some other marine mammals. The planned 
monitoring and mitigation measures, including visual monitoring, 
passive acoustic monitoring (PAM), power downs, and shut downs of the 
airguns when mammals are seen within the EZ will minimize the already 
minimal probability of exposure of marine mammals to sounds strong 
enough to induce PTS.
    Non-auditory Physiological Effects - Non-auditory physiological 
effects or injuries that theoretically might occur in marine mammals 
exposed to strong underwater sound include stress, neurological 
effects, bubble formation, resonance effects, and other types of organ 
or tissue damage (Cox et al., 2006.; Southall et al., 2007). However, 
studies examining such effects are limited. If any such effects do 
occur, they would probably be limited to unusual situations when 
animals might be exposed at close range for unusually long periods, 
when sound is strongly channeled with less-than-normal propagation 
loss, or when dispersal of the animals is constrained by shorelines, 
shallows, etc. Airgun pulses, because of their brevity and 
intermittence, are less likely to trigger resonance or bubble formation 
than are more prolonged sounds. It is doubtful that any single marine 
mammal would be exposed to strong seismic sounds for time periods long 
enough to induce physiological stress.
    Until recently, it was assumed that diving marine mammals are not 
subject to the bends or air embolism. This possibility was first 
explored at a workshop (Gentry [ed.], 2002) held to discuss whether a 
stranding of beaked whales in the Bahamas in 2000 (Balcomb and 
Claridge, 2001; NOAA and USN, 2001) might have been related to bubble 
formation in tissues caused by exposure to noise from naval sonar. 
However, this link could not be confirmed. Jepson et al. (2003) first 
suggested a possible link between mid-frequency sonar activity and 
acute chronic tissue damage that results from the formation in vivo of 
gas bubbles, based on a beaked whale stranding in the Canary Islands in 
2002 during naval exercises. Fernandez et al. (2005a) showed those 
beaked whales did indeed have gas bubble-associated lesions, as well as 
fat embolisms. Fernandez et al. (2005b) also found evidence of fat 
embolism in three beaked whales that stranded 100 km (62 mi) north of 
the Canaries in 2004 during naval exercises. Examinations of several 
other stranded species have also revealed evidence of gas and fat 
embolisms (Arbelo et al., 2005; Jepson et al., 2005a; Mendez et al., 
2005). Most of the afflicted species were deep divers. There is 
speculation that

[[Page 45416]]

gas and fat embolisms may occur if cetaceans ascend unusually quickly 
when exposed to aversive sounds, or if sound in the environment causes 
the destablization of existing bubble nuclei (Potter, 2004; Arbelo et 
al., 2005; Fernandez et al. 2005a; Jepson et al., 2005b; Cox et al., 
2006). Even if gas and fat embolisms can occur during exposure to mid-
frequency sonar, there is no evidence that that type of effect occurs 
in response to airgun sounds.
    In general, little is known about the potential for seismic survey 
sounds to cause auditory impairment or other physical effects in marine 
mammals. Available data suggest that such effects, if they occur at 
all, would be limited to within short distances of the sound source and 
probably to projects involving large arrays of airguns. The available 
data do not allow for 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 auditory impairment or non-auditory 
physical effects. It is not known whether aversive behavioral responses 
to airgun pulses by deep-diving species could lead to indirect 
physiological problems as apparently can occur upon exposure of some 
beaked whales to mid-frequency sonar (Cox et al., 2006). Also, the 
planned mitigation measures, including shut downs of the airguns, will 
reduce any such effects that might otherwise occur.
Strandings and Mortality
    Marine mammals close to underwater detonations of high explosives 
can be killed or severely injured, and their auditory organs are 
especially susceptible to injury (Ketten et al., 1993; Ketten 1995). 
Airgun pulses are less energetic and have slower rise times, and there 
is no proof that they can cause injury, death, or stranding even in the 
case of large airgun arrays. However, the association of mass 
strandings of beaked whales with naval exercises and, in one case, an 
L-DEO seismic survey, has raised the possibility that beaked whales 
exposed to strong pulsed sounds may be especially susceptible to injury 
and/or behavioral reactions that can lead to stranding. Appendix B(g) 
of LDEO's application provides addition details.
    Seismic pulses and mid-frequency sonar pulses are quite different. 
Sounds produced by airgun arrays are broadband with most of the energy 
below 1 kHz. Typical military mid-frequency sonars operate at 
frequencies of 2-10 kHz, generally with a relatively narrow bandwidth 
at any one time. Thus, it is not appropriate to assume that there is a 
direct connection between the effects of military sonar and seismic 
surveys on marine mammals. However, evidence that sonar pulses can, in 
special circumstances, lead to physical damage and mortality (Balcomb 
and Claridge, 2001; NOAA and USN, 2001; Jepson et al., 2003; Fernandez 
et al., 2004, 2005a; Cox et al., 2006), even if only indirectly, 
suggests that caution is warranted when dealing with exposure of marine 
mammals to any high-intensity pulsed sound.
    There is no conclusive evidence of cetacean strandings as a result 
of exposure to seismic surveys. Speculation concerning a possible link 
between seismic surveys and strandings of humpback whales in Brazil 
(Engel et al., 2004) was not well founded based on available data 
(IAGC, 2004; IWC, 2006). In September 2002, there was a stranding of 
two Cuvier's beaked whales in the Gulf of California, Mexico, when the 
L-DEO vessel Ewing was operating a 20-gun, 8,490-in\3\ array in the 
general area. The link between the stranding and the seismic survey was 
inconclusive and not based on any physical evidence (Hogarth, 2002; 
Yoder, 2002). Nonetheless, that plus the incidents involving beaked 
whale strandings near naval exercises involving use of mid-frequency 
sonar suggests a need for caution when conducting seismic surveys in 
areas occupied by beaked whales. No injuries of beaked whales are 
anticipated during the proposed study because of (1) the high 
likelihood that any beaked whales nearby would avoid the approaching 
vessel before being exposed to high sound levels, (2) the proposed 
monitoring and mitigation measures, and (3) differences between the 
sound sources operated by L-DEO and those involved in the naval 
exercises associated with strandings.

Potential Effects of Other Acoustic Devices

Multibeam Echosounder Signals
    The Simrad EM 120 12-kHz MBES will be operated from the source 
vessel at some times during the planned study. Sounds from the MBES are 
very short pulses, occurring for 15 ms once every 5-20 s, depending on 
water depth. Most of the energy in the sound pulses emitted by the MBES 
is at frequencies centered at 12 kHz, and the maximum source level is 
242 dB re 1 microPa (rms). The beam is narrow (1[deg]) in fore-aft 
extent and wide (150[deg]) in the cross-track extent. Each ping 
consists of nine successive fan-shaped transmissions (segments) at 
different cross-track angles. Any given mammal at depth near the 
trackline would be in the main beam for only one or two of the nine 
segments. Also, marine mammals that encounter the MBES are unlikely to 
be subjected to repeated pulses because of the narrow fore-aft width of 
the beam and will receive only limited amounts of pulse energy because 
of the short pulses. Animals close to the ship (where the beam is 
narrowest) are especially unlikely to be ensonified for more than one 
2-15 ms pulse (or two pulses if in the overlap area). Similarly, 
Kremser et al. (2005) noted that the probability of a cetacean swimming 
through the area of exposure when an MBES emits a pulse is small. The 
animal would have to pass the transducer at close range and be swimming 
at speeds similar to the vessel in order in order to receive the 
multiple pulses that might result in sufficient exposure to cause TTS. 
Burkhardt et al. (2007) concluded that immediate direct auditory injury 
was possible only if a cetacean dived under the vessel into the 
immediate vicinity of the transducer.
    Navy sonars that have been linked to avoidance reactions and 
stranding of cetaceans (1) generally have a longer pulse duration that 
the Simrad EM120, and (2) are often directed close to horizontally vs. 
more downward for the MBES.. The area of possible influence of the MBES 
is much smaller a narrow band below the source vessel. The duration of 
exposure for a given marine mammal can be much longer for a Navy sonar.
    Marine mammal communications will not be masked appreciably by the 
MBES signals given its low duty cycle and the brief period when an 
individual mammal is likely to be within its beam. Furthermore, in the 
case of baleen whales, the signals (12 kHz) do not overlap with the 
predominant frequencies in the calls, which would avoid significant 
masking.
    Behavioral reactions of free-ranging marine mammals to sonars and 
other sound sources appear to vary by species and circumstance. 
Observed reactions have included silencing and dispersal by sperm 
whales (Watkins et al., 1985), increased vocalizations and no dispersal 
by pilot whales (Rendell and Gordon, 1999), and the previously-
mentioned beachings by beaked whales. During exposure to a 21-25 kHz 
whale-finding sonar with a source level of 215 dB re 1 microPa, gray 
whales showed slight avoidance (approximately 200 m; 656 ft) behavior 
(Frankel, 2005). However, all of those observations are of limited 
relevance to the present situation. Pulse durations from those sonars 
were much

[[Page 45417]]

longer than those of the MBES, and a given mammal would have received 
many pulses from the naval sonars. During L-DEO's operations, the 
individual pulses will be very short, and a given mammal would not 
receive many of the downward-directed pulses as the vessel passes by.
    Captive bottlenose dolphins and a white whale exhibited changes in 
behavior when exposed to 1 s pulsed sounds at frequencies similar to 
those that will be emitted by the MBES used by L-DEO and to shorter 
broadband pulsed signals. Behavioral changes typically involved what 
appeared to be deliberate attempts to avoid the sound exposure 
(Schlundt et al., 2000; Finneran et al., 2002; Finneran and Schlundt, 
2004). The relevance of those data to free-ranging odontocetes is 
uncertain, and in any case, the test sounds were quite different in 
either duration or bandwidth as compared with those from an MBES.
    L-DEO is not aware of any data on the reactions of pinnipeds to 
sonar or echosounder sounds at frequencies similar to the 12 kHz 
frequency of the Langseth's MBES. Based on observed pinniped responses 
to other types of pulsed sounds, and the likely brevity of exposure to 
the MBES sounds, pinniped reactions are expected to be limited to 
startle or otherwise brief responses of no lasting consequence to the 
animals.
    NMFS believes that the brief exposure of marine mammals to one 
pulse, or small numbers of signals, from the MBES are not likely to 
result in the harassment of marine mammals.
Sub-bottom Profiler Signals
    A SBP will be operated from the source vessel during the planned 
study. Sounds from the SBP are very short pulses, occurring for 1-4 ms 
once every second. Most of the energy in the sound pulses emitted by 
the SBP is at mid frequencies, centered at 3.5 kHz. The beamwidth is 
approximately 30[deg] and is directed downward. The SBP on the Langseth 
has a maximum source level of 204 dB re 1 microPam. 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, and 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.
    Marine mammal communications will not be masked appreciably by the 
SBP signals given their directionality and the brief period when an 
individual mammal is likely to be within its beam. Furthermore, in the 
case of most odontocetes, the signals do not overlap with the 
predominant frequencies in the calls, which would avoid significant 
masking.
    Marine mammal behavioral reactions to other pulsed sound sources 
are discussed above, and responses to the SBP are likely to be similar 
to those for other pulsed sources if received at the same levels. The 
pulsed signals from the SBP are somewhat weaker than those from the 
MBES. Therefore, behavioral responses are not expected unless marine 
mammals are very close to the source.
    It is unlikely that the SBP produces pulse levels strong enough to 
cause hearing impairment or other physical injuries even in an animal 
that is (briefly) in a position near the source. The SBP is usually 
operated simultaneously with other higher-power acoustic sources. Many 
marine mammals will move away in response to the approaching higher-
power sources or the vessel itself before the mammals would be close 
enough for there to be any possibility of effects from the less intense 
sounds from the SBP. In the case of mammals that do not avoid the 
approaching vessel and its various sound sources, mitigation measures 
that would be applied to minimize effects of other sources would 
further reduce or eliminate any minor effects of the SBP.
    NMFS believes that to avoid the potential for permanent 
physiological damage (Level A Harassment), cetaceans and pinnipeds 
should not be exposed to pulsed underwater noise at received levels 
exceeding, respectively, 180 and 190 dB re 1 microPa (rms). The 
precautionary nature of these criteria is discussed in Appendix B (f) 
of L-DEO's application, including the fact that the minimum sound level 
necessary to cause permanent hearing impairment is higher, by a 
variable and generally unknown amount, than the level that induces 
barely-detectable temporary threshold shift (TTS) and the level 
associated with the onset of TTS is often considered to be a level 
below which there is no danger of permanent damage. NMFS also assumes 
that cetaceans or pinnipeds exposed to levels exceeding 160 dB re 1 
microPa (rms) may experience Level B Harassment.

Estimated Take by Incidental Harassment

    All anticipated takes would be ``takes by harassment'', involving 
temporary changes in behavior. The proposed mitigation measures are 
expected to minimize the possibility of injurious takes. The sections 
below describe methods to estimate ``take by harassment'', and present 
estimates of the numbers of marine mammals that might be affected 
during the proposed Gulf of Alaska seismic survey. The estimates of 
``take by harassment'' are based on consideration of the number of 
marine mammals that are exposed to certain received sound levels by 
approximately 2,386 km of seismic surveys in the Gulf of Alaska. The 
main sources of distributional and numerical data used in deriving the 
estimates are described below.
    Empirical data concerning 190-, 180-, 170-, and 160 dB re 1 microPa 
isopleth distances in deep and shallow water were acquired for various 
airgun configurations during the acoustic calibration study of the R/V 
Maurice Ewing's (Ewing) 20-airgun 8,600 in\3\ array in 2003 (Tolstoy et 
al., 2004a,b). The results showed that radii around the airguns where 
the received level was 180 dB re 1 microPa rms, the threshold for 
estimating level B harassment applicable to cetaceans (NMFS 2000), 
varied with water depth. Similar depth-related variation is likely for 
the 190-dB re 1 microPa threshold for estimating Level B harassment 
applicable to cetaceans and the 190-dB re 1 microPa threshold 
applicable to pinnipeds, although these were not measured. The L-DEO 
model does not allow for bottom interactions, and thus is most directly 
applicable to deep water and to relatively short ranges.
    The empirical data indicated that, for deep water (>1,000 m; 3,280 
ft), the L-DEO model (as applied to the Ewing's airgun configurations) 
overestimated the measured received sound levels at a given distance 
(Tolstoy et al., 2004a,b). However, to be conservative, the distances 
predicted by L-DEO's model for the survey will be applied to deep-water 
areas during the proposed study (see Figure 3 and 4 and Table 1 in the 
application). As very few, if any, mammals are expected to occur deeper 
than 2,000 m (6,562 ft), this depth was used as the maximum relevant 
depth.
    Empirical measurements of sounds from the Ewing's airgun arrays 
were not conducted for intermediate depths (100-1,000 m; 328-3,280 ft). 
On the expectation that results would be intermediate, the estimates 
provided by the model for deep-water situations are used to obtain 
estimates for intermediate-depth sites. Corresponding correction 
factors, applied to the modeled radii for the Langseth's airgun 
configuration, will be used during the proposed study for intermediate 
depths (see Table 1 of the application).
    Empirical measurements near the Ewing indicated that in shallow 
water (<100 m; 328 ft), the L-DEO model underestimates actual levels. 
In previous L-DEO projects, the exlusion

[[Page 45418]]

zones were typically based on measured values and ranged from 1.3 to 
15x higher than the modeled values depending on the size of the airgun 
array and the sound level measured (Tolstoy et al., 2004b). During the 
proposed cruise, similar correction factors will be applied to derive 
appropriate shallow-water radii from the modeled deep-water radii for 
the Langseth's airgun configuration (see Table 1 of the application).
    Using the modeled distances and various correction factors, Table 1 
(from the application) shows the distances at which four rms sound 
levels are expected to be received from the 36-airgun array and a 
single airgun in three different water depths.
    The anticipated radii of influence of the MBES and the SBP are much 
smaller than those for the airgun array. It is assumed that, during 
simultaneous operations of the airgun array and echosounders, marine 
mammals close enough to be affected by the echosounders would already 
be affected by the airguns. However, whether or not the airguns are 
operating simultaneously with the echosounders, marine mammals are not 
expected to be exposed to sound pressure levels great enough or long 
enough for taking to occur given echosounders' characteristics (e.g., 
narrow downward-directed beam) and other considerations described 
above. Therefore, no additional allowance is included for animals that 
might be affected by sound sources other than airguns.
    There are few systematic data on the numbers and distributions of 
marine mammals in SE Alaska and the GOA. Zerbini et al. (2003, 2006, 
2007) conducted vessel-based surveys in the northern and western GOA 
from the Kenai Peninsula to the central Aleutian Islands during July-
August 2001-2003. Killer whales were the principal target of the 
surveys, but the abundance and distribution of fin, humpback, and minke 
whales were also reported. Waite (2003) conducted vessel-based surveys 
in the northern and western GOA from PWS to approximately 160[deg] W 
off Alaska Peninsula during 26 June- 15 July 2003; cetaceans recorded 
included small odontocetes, beaked whales, and mysticetes. The eastern 
part of Zerbini et al.'s surveys and Waite's survey were confined to 
water <1,000 m deep, and most effort was in depths <100 m. Dahlheim et 
al. (2000) conducted aerial surveys of the nearshore waters from 
Bristol Bay to Dixon Entrance for harbor porpoises; SE Alaska was 
surveyed during 1-26 June 1993. Dahlheim and Towell (1994) conducted 
vessel-based surveys of Pacific white-sided dolphins in the inland 
waterways of SE Alaska during April-May, June or July, and September- 
early October of 1991-1993. In a report on a seismic cruise in SE 
Alaska from Dixon Entrance to Kodiak Island during August-September 
2004, MacLean and Koski (2005) included density estimates of cetaceans 
and pinnipeds for each of three depth ranges (<100 m, 100-1,000 m, and 
>1,000 m) during non-seismic periods.
    Most surveys for pinnipeds in Alaskan waters have estimated the 
number of animals at haul-out sites, not in the water (e.g., Loughlin, 
1994; Sease et al., 2001; Withrow and Cesarone, 2002; Sease and York, 
2003). To our knowledge, the estimates of MacLean and Koski (2005) are 
the only in-water estimates of pinnipeds in the proposed survey area.
    Table 7 in L-DEO's application gives the average and maximum 
densities in each of three depth ranges for each cetacean and pinniped 
species reported to occur in SE Alaska. The densities from MacLean and 
Koski (2005) and those calculated from effort and sightings in Dahlheim 
and Towell (1994) and Waite (2003) have been corrected for both 
detectability and availability bias using correction factors from 
Dahlheim et al. (2000) and Koski et al. (1998). Detectability bias is 
associated with diminishing sightability with increasing lateral 
distance from the trackline. Availability bias refers to the fact that 
there is less-than-100 percent probability of sighting an animal that 
is present along the survey trackline. In determining the estimated 
numbers, L-DEO used the killer whale and mysticete densities from the 
easternmost blocks (1-6) surveyed by Zerbini et al. (2006, 2007), the 
harbor porpoise densities for the SE Alska portion of the areas 
surveyed by Dahlheim et al. (2000), and only the Pacific white-sided 
dolphin data from the June or July and September- early October surveys 
by Dahlheim and Towell (1994). Maps of effort and sightings in Waite 
(2003) an Zerbini et al. (2006, 2007) were used to roughly allocate 
effort and sighting between waters <100 m and 100-1,000 m deep as 
either all or none, most (80 percent), or similar (50 percent).
    There is some uncertainty about the representatives of the data and 
the assumptions used in the calculations below for three main reasons: 
(1) all but the MacLean and Koski (2005) and Dahlheim and Towell (1994) 
September-early October surveys were carried out earlier (June-July) 
than the proposed September survey; (2) the Waite (2003) and Zerbini et 
al. (20006, 2007) surveys were in the northern and western GOA; and (3) 
only the MacLean and Koski (2005) surveys included depths >1,000 m, 
whereas approximately 43 percent of the proposed line-km are in water 
depths >1,000 m. However, these represent the best available 
information. Also, to provide some allowance for these uncertainties L-
DEO calculated, ``maximum estimates'' as well as ``best estimates'' of 
the densities present and numbers potentially affected. Best estimates 
of density are effort-weighted mean densities from all previous 
surveys, whereas maximum estimates of density come from whichever of 
the individual surveys provided the highest density. Where only one 
estimate was available, the maximum density was assumed to be the 
observed (best) density multiplied by 1.5.
    For three species, L-DEO's density estimates are much higher than 
densities expected during the proposed survey. The estimates for 
humpback and fin whales are based on surveys where large concentrations 
were sighted in nearshore waters and often inland waterways, viz. Sitka 
Sound, Icy Strait, and the bottom of Lynn Canal (MacLean and Koski, 
2005), and near Kodiak Island (Waite, 2003; Zerbini et al., 2006). No 
such concentrations are expected in the proposed survey area. L-DEO's 
estimates for Dall's porpoise are from vessel-based surveys without 
seismic survey activity; they are overestimates, possibly by a factor 
of 5x, given the tendency of this species to approach vessels (Turnock 
and Quinn, 1991). Noise from the airgun array during the proposed 
survey is expected to at least reduce and possibly eliminate the 
tendency to approach the vessel. Dall's porpoises are tolerant of small 
airgun sources (MacLean and Koski, 2005) and tolerated higher noise 
levels than other species during a large array survey (Bain and 
Williams, 2006), but they did respond to that and another large airgun 
array by moving away (Calambokidis and Osmek, 1998; Bain and Williams, 
2006). Because of these considerable overestimates, the best and 
maximum estimates in Table 7 of L-DEO's application were halved by L-
DEO to calculate numbers exposed. In fact, actual densities are 
undoubtedly much lower than that.
    The estimated numbers of individuals potentially exposed are 
presented below based on a 160-dB re 1 microPa (rms) Level B harassment 
exposure threshold for cetaceans and pinnipeds. It is assumed that 
marine mammals exposed to airgun sounds at these levels might 
experience disruption of behavioral patterns.
    It should be noted that the following estimates of takes by 
harassment assume that the surveys will be fully completed;

[[Page 45419]]

in fact, the planned number of line-km has been increased by 25 percent 
to accomodate lines that may need to be repeated, equipment testing, 
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-km to seismic operations that can be undertaken. 
Furthermore, any marine mammal sightings within or near the designated 
EZ (see will result in the shut down of seismic operations. Thus, the 
following estimates of the numbers of marine mammals exposed to 160-dB 
sounds probably overestimate the actual numbers of marine mammals that 
might be involved. These estimates assume that there will be no 
weather, equipment, or mitigation delays, which is highly unlikely.
    The number of different individuals that may be exposed to airgun 
sounds with received levels [gteqt]160 dB re 1 microPa (rms) on one or 
more occasions was estimated by considering the total marine area that 
would be within the 160-dB radius around the operating airgun array on 
at least one occasion. The proposed seismic lines do not run parallel 
to each other in close proximity, which minimizes the number of times 
an individual mammal may be exposed during the survey. Only one 
transect line is proposed to be surveyed twice, and it is unknown how 
much time will pass between the first and the second transit. 
Therefore, some of the same individuals may be approached by the 
operating airguns and come within the 160-dB distance on up to two 
occasions. However, this also means that some different marine mammals 
could occur in the area during the second pass. The line that could be 
surveyed twice was counted twice in L-DEO's calculations.
    For each depth stratum, the number of different individuals 
potentially exposed to received levels [gteqt]160 dB re 1 microPa (rms) 
was calculated by multiplying:
     The expected species density, either ``mean'' (i.e., best 
estimate) or ``maximum'', for a particular water depth, times
     The anticipated minimum area to be ensonified to that 
level during airgun operations in each water depth stratum.
    The same approach was used to estimate exposures of pinnipeds, 
delphinids, and Dall's porpoise to received levels [gteqt]170 dB.
    The area expected to be ensonified was determined by entering the 
planned survey lines into a MapInfo Geographic Information System 
(GIS), using the GIS to identify the relevant areas by ``drawing'' the 
applicable 160-dB buffer around each seismic line (depending on water 
and tow depth) and then calculating the total area within the buffers. 
Areas where overlap occurred (because of intersecting lines) were 
limited and included only once to determine the area expected to be 
ensonified.
    Applying the approach described above, approximately 28,900 km2 
would be within the 160-dB isopleth on one or more occasions during the 
survey, including the 25 percent added as a contingency. However, this 
approach does not allow for turnover in the mammal populations in the 
study area during the course of the study. This might somewhat 
underestimate actual numbers of individuals exposed, although the 
conservative (i.e., probably overestimated) line-kilometer distances 
used to calculate the area may offset this. In addition, the approach 
assumes that no cetaceans will move away or toward the trackline (as 
the Langseth approaches) in response to increasing sound levels prior 
to the time the levels reach 160 dB re 1 microPa (rms). Another way of 
interpreting the estimates that follow is that they represent the 
number of individuals that are expected (in the absence of the seismic 
activity) to occur in the waters that will be exposed to [gteqt]160 dB 
re 1 microPa (rms).

  TABLE 3. Estimates of the possible numbers of marine mammals exposed to sound levels [gteqt]160 dB during L DEO's proposed seismic survey in SE Alaska in September 2008. The proposed sound
 source consists of a 36-gun, 6600-in\3\, airgun array. Received levels of airgun sounds are expressed in dB re 1 microParms (averaged over pulse duration), consistent with NMFS' practice. Not
  all marine mammals will change their behavior when exposed to these sound levels, but some may alter their behavior when levels are lower (see text). The column of numbers in boldface shows
                                                                 the numbers of ''takes'' for which authorization is requested.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                         Number of Individuals Exposed to Sound Levels 160 dB
                                 ----------------------------------------------------------------------------------------------------------------------------------------------
                                                                 Best Estimate \1\                                                     Maximum Estimate \1\
             Species             ----------------------------------------------------------------------------------------------------------------------------------------------  Requested Take
                                                               Number                                                                                                             Authorization
                                 ----------------------------------------------------------------- % of Pop'n \2\      <100 m       100-1000 m       >1000 m         Total
                                      <100 m         100-1000 m        >1000 m          Total
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Odontocetes
---------------------------------                                                                                                                                              -----------------
Sperm whale                       0               4                45              49              0.2             0              7               67             74             74
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Cuvier's beaked whale             0               35               0               35              0.3             0              47              0              47             47
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Baird's beaked whale              0               8                0               8               0.1             0              11              0              11             11
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Stejneger's beaked whale          0               0                0               0               0               0              0               0              3              3
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Beluga                            0               0                0               0               0               0              0               0              5              5
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Pacific white-sided dolphin       13              43               0               56              0.1             27             176             0              203            203
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Risso's dolphin                   0               0                0               0               0               0              0               0              5              5
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Killer whale                      65              51               0               116             1.4             173            112             0              285            285
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

[[Page 45420]]

 
Short-finned pilot whale          0               0                0               0               0               0              0               0              20             20
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Harbor porpoise                   118             228              0               346             0.4             239            309             0              548            548
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Dall's porpoise                   372             4225             783             5379            0.5             561            5594            1174           7329           7329
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Mysticetes
---------------------------------                                                                                                                                              -----------------
North Pacific right whale         0               0                0               0               0               0              0               0              2              2
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Gray whale                        0               0                0               0               0               0              0               0              6              6
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Humpback whale                    83              76               87              246             4.1             138            156             130            424            424
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Minke whale                       6               3                0               9               0.1             25             16              0              41             41
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Fin whale                         19              71               0               89              0.6             49             129             0              178            178
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Blue whale                        0               0                0               0               0               0              0               0              2              2
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Pinnipeds
---------------------------------                                                                                                                                              -----------------
Northern fur seal                 0               0                0               0               0               0              0               0              5              5
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Harbor seal                       10              259              0               269             <0.1            15             388             0              403            403
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Steller sea lion                  20              54               0               74              <0.1            30             80              0              110            110
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Best and maximum estimates of density are from Table 3 in L-DEO's application.
\2\ Regional population size estimates are from Table 2 of L-DEO's application.

    The ``best estimates'' of the numbers of individual marine mammals 
that could be exposed to seismic sounds with received levels [gteqt]160 
dB re 1 microPa (rms) during the proposed survey is shown in Table 8 of 
L-DEO's application and Table 3 (shown above). That total includes 49 
sperm, 246 humpback, and 89 fin whales, which would represent 0.2 
percent, 4.1 percent, and 0.6 percent, respectively, of the regional 
populations (Table 3). However the numbers of humpback and fin whales 
exposed are overestimated considerably because the estimated densities 
are overestimates (see previous section). Dall's porpoise is expected 
to be the most common species in the study area; the best estimate of 
the number of Dall's porpoise that could be exposed is 5,379 or 0.5 
percent of the regional population (Table 3). This is also an 
overestimate because the estimated densities are overestimates (see 
previous section). Estimates for other species are lower (Table 3).
    The ``maximum estimate'' column in Table 3 shows estimates totaling 
9,701 marine mammals for the three depth ranges combined. For species 
that could occur in the study area but were not sighted in the surveys 
from which density estimates were calculated, the average group size 
has been used as the maximum estimate.
    Based on the ``best'' densities, 74 threatened Steller sea lions 
and 269 harbor seals could be exposed to airgun sounds [gteqt]160 dB re 
1 microPa (rms), which would represent <0.1 percent for both of the 
respective regional populations. The ``maximum estimate'' column in 
Table 3 shows an estimated 110 Steller sea lions could be exposed to 
airgun sounds [gteqt]160 dB re 1 microPa (rms). The corresponding 
numbers for harbor seals are 403. LDEO has also included a low maximum 
estimate for the northern fur seal, a species that could be present, 
but whose density was not calculated because it was not sighted during 
the survey of MacLean and Koski (2005). The numbers for which ``take 
authorization'' is requested, given in the far right column of Table 3, 
are based on the maximum 160-dB estimates.
Potential Effects on Habitat
    The proposed L-DEO seismic survey in the GOA will not result in any 
permanent impact on habitats used by marine mammals or to the food 
sources they use. The main impact issue associated with the proposed 
activity will be temporarily elevated noise levels and the associated 
direct effects on marine mammals, as discussed above. The following 
sections briefly review effects of airguns on fish and invertebrates, 
and more details are included in Appendices C and D, respectively, in 
L-DEO's application.
Effects on Fish
    One reason for the adoption of airguns as the standard energy 
source for marine seismic surveys was that, unlike explosives, they 
have not been associated with large-scale fish kills. However, existing 
information relating to the impacts of seismic surveys on

[[Page 45421]]

marine fish populations and invertebrate species is very limited (see 
Appendix C of L-DEO's application). There are three types of potential 
effects of exposure to seismic surveys: (1) pathological, (2) 
physiological, and (3) behavioral. Pathological effects include 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 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 
the ultimate pathological effect on individual animals (i.e., 
mortality).
    The specific received sound levels at which permanent adverse 
effects to fish potentially 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. 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 aspect of potential impacts relates to how exposure to 
seismic survey sound affects marine fish populations and their 
viability, including their availability to fisheries.
    The following sections provide a general synopsis of available 
information on the effects of exposure to seismic and other 
anthropogenic sound as relevant to fish and invertebrates. The 
information comprises results from scientific studies of varying 
degrees of soundness and 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 then 
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 (see Appendix C of L-DEO's application). For a given sound to 
result in hearing loss, the sound must exceed, by some specific 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 is unknown; however, it likely depends 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 is known, there are two valid papers with proper experimental 
methods, controls, and careful pathological investigation implicating 
sounds produced by actual seismic survey airguns with 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 fishes 
from the Mackenzie River Delta. This study found that broad whitefish 
(Coreogonus nasus) that received a sound exposure level of 177 dB re 1 
microPa\2.\s showed no hearing loss. During both studies, the 
repetitive exposure to sound was greater than would have occurred 
during a typical seismic survey. However, the substantial low-frequency 
energy produced by the airgun arrays [less than approximately 400 Hz in 
the study by McCauley et al. (2003) and less than approximately 200 Hz 
in Popper et al. (2005)] likely did not propagate to the fish because 
the water in the study areas was very shallow (approximately 9 m, 29.5 
ft, in the former case and <2 m, 6.6 ft, in the latter). Water depth 
sets a lower limit on the lowest sound frequency that will propagate 
(the ``cut-off frequency'') at about one-quarter wavelength (Urick, 
1983; Rogers and Cox, 1988).
    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 (Hubbs and Rechnitzer, 1951; Wardle et al., 2001). 
Generally, the higher the received pressure and the less time it takes 
for the pressure to rise and decay, the greater the chance of acute 
pathological effects. Considering the peak pressure and rise/decay time 
characteristics of seismic airgun arrays used today, the pathological 
zone for fish and invertebrates would be expected to be within a few 
meters of the seismic source (Buchanan et al., 2002). 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, 2000b; 
Bjarti, 2002; Hassel et al., 2003; Popper et al., 2005).
    Except for these two studies, at least with airgun-generated sound 
treatments, most contributions rely on rather subjective assays such as 
fish ``alarm'' or ``startle response'' or changes in catch rates by 
fishers. These observations are important in that they attempt to use 
the levels of exposures that are likely to be encountered by most free-
ranging fish in actual survey areas. However, the associated sound 
stimuli are often poorly described, and the biological assays are 
varied (Hastings and Popper, 2005).
    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 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 fih would be expected to be with 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; Hassel et al., 2003; 
Popper et al., 2005).
    Some studies have reported 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. Saetre 
and Ona (1996) applied a ``worst-case scenario'' mathematical model to 
investigate the effects of seismic energy on fish eggs and larvae and 
concluded that mortality rates caused by exposure to seismic are so 
low, as compared to natural mortality

[[Page 45422]]

rates, that the impact of seismic surveying on recruitment to a fish 
stock must be regarded as insignificant.
    Some studies have suggested that seismic survey sound has a limited 
pathological impact on early developmental stages of crustaceans 
(Pearson et al., 1994; Christian et al., 2003; DFO, 2004). However, the 
impacts appear to be either temporary or insignificant compared to what 
occurs under natural conditions. Controlled field experiments on adult 
crustaceans (Christian et al., 2003, 2004; DFO, 2004) and adult 
cephalopods (McCauley et al., 2000a,b) exposed to seismic survey sound 
have not resulted in any significant pathological impacts on the 
animals. It has been suggested that exposure to commercial seismic 
survey activities has injured giant squid (Guerra et al., 2004), but 
there is no evidence to support such claims.
    Physiological Effects - Physiological effects refer to cellular 
and/or biochemical responses of fish and invertebrates to acoustic 
stress. Such stress potentially could affect fish and 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 or fish after 
exposure to seismic survey sound appear to be temporary (hours to days) 
in all studies done to date (see Payne et al., 2007 for invertebrates; 
see Sverdrup et al., 1994; McCauley et al., 2000a,b for fish). 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 (see Appendix C of L-DEO's application).
    Summary of Physical (Pathological and Physiological) Effects - As 
indicated in the preceding general discussion, there is a relative lack 
of knowledge about the potential physical (pathological and 
physiological) effects of seismic energy on marine fish and 
invertebrates. Available data suggest that there may be physical 
impacts on egg, larval, juvenile, and adult stages at very close range. 
Considering typical source levels associated with commercial seismic 
arrays, close proximity to the source would result in exposure to very 
high energy levels. Whereas egg and larval stages are not able to 
escape such exposures, juveniles and adults most likely would avoid it. 
In the case of eggs and larvae, it is likely that the numbers adversely 
affected by such exposure would not be that different from those 
succumbing to natural mortality. Limited data regarding physiological 
impacts on fish and invertebrates indicate that these impacts are short 
term and are most apparent after exposure at close range.
    The proposed seismic program for 2008 is predicted to have 
negligible to low physical effects on the various life stages of fish 
and invertebrates for its short duration (approximately 24 days) and 
approximately 1,909-km of unique survey lines extent. Therefore, 
physical effects of the proposed program on fish and invertebrates 
would not be significant.
    Behavioral Effects - Because of the apparent lack of serious 
pathological and physiological effects of seismic energy on marine fish 
and invertebrates, the highest level of concern now centers on the 
possible effects of exposure to seismic surveys on the distribution, 
migration patterns, mating, and catchability of fish. There is a need 
for more information on exactly what effects such sound sources might 
have on the detailed behavior patterns of fish and invertebrates at 
different ranges.
    Behavioral effects include changes in the distribution, migration, 
mating, and catchability of fish populations. Studies investigating the 
possible effects of sound (including seismic sound) on fish and 
invertebrate behavior have been conducted on both uncaged and caged 
animals (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.
    There is general concern about potential adverse effects of seismic 
operations on fisheries, namely a potential reduction in the 
``catchability'' of fish involved in fisheries. Although reduced catch 
rates have been observed in some marine fisheries during seismic 
testing, in a number of cases the findings are confounded by other 
sources of disturbance (Dalen and Raknes, 1985; Dalen and Knutsen, 
1986; Lokkeborg, 1991; Skalski et al., 1992; Engas et al., 1996). In 
other airgun experiments, there was no change in catch per unit effort 
(CPUE) of fish when airgun pulses were emitted, particularly in the 
immediate vicinity of the seismic survey (Pickett et al., 1994; La 
Bella et al., 1996). For some species, reductions in catch may have 
resulted from a change in behavior of the fish (e.g., a change in 
vertical or horizontal distribution) as reported in Slotte et al. 
(2004).
    In general, any adverse effects on fish behavior or fisheries 
attributable to 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.
    For marine invertebrates, behavioral changes could potentially 
affect such aspects as reproductive success, distribution, 
susceptibility to predation, and catchability by fisheries. Studies of 
squid indicated startle responses (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). Parry 
and Gason (2006) reported no changes in rock lobster CPUE during or 
after seismic surveys off western Victoria, Australia, from 1978-2004. 
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). 
Additional information regarding the behavioral effects of seismic on 
invertebrates is contained in Appendix D (c) of L-DEO's application.
    Summary of Behavioral Effects - As is the case with pathological 
and physiological effects of seismic on fish and invertebrates, 
available information is relatively scant and often contradictory. 
There have been well-documented observations of fish and invertebrates 
exhibiting behaviors that appeared to be responses to exposure to 
seismic energy (i.e., startle response, change in swimming direction 
and speed, and change in vertical distribution), but the ultimate 
importance of those behaviors is unclear. Some studies indicate that 
such behavioral changes are very temporary, whereas others imply that 
fish might not resume pre-seismic behaviors or distributions for a 
number of days. There appears to be a great deal of inter- and intra-
specific variability. In the case of finfish, three general types of 
behavioral responses have been identified: startle, alarm, and 
avoidance. The type of behavioral reaction appears to depend on many 
factors, including the type of behavior being exhibited before 
exposure, and proximity and energy level of sound source.
    During the proposed study, only a small fraction of the available 
habitat would be ensonified at any given time,

[[Page 45423]]

and fish species would return to their pre-disturbance behavior once 
the seismic activity ceased. The proposed seismic program is predicted 
to have negligible to low behavioral effects on the various life stages 
of the fish and invertebrates during its relatively short duration and 
extent.
    Because of the reasons noted above and the nature of the proposed 
activities, the proposed operations are not expected to have any 
habitat-related effects that could cause significant or long-term 
consequences for individual marine mammals or their populations or 
stocks. Similarly, any effects to food sources are expected to be 
negligible.
Subsistence Activities
    Subsistence hunting and fishing continue to feature prominently in 
the household economies and social welfare of some Alaskan residents, 
particularly among those living in small, rural villages (Wolfe and 
Walker, 1987). Subsistence remains the basis for Alaska Native culture 
and community. In rural Alaska, subsistence activities are often 
central to many aspects o human existence from patterns of family life 
to artistic expression and community religious and celebratory 
activities.
    Marine mammals are hunted legally in Alaskan waters by coastal 
Alaska Natives. In SE Alaska, the only marine mammals that are hunted 
are Steller sea lions, harbor seals, and sea otters. Wolfe et al. (2004 
in Angliss and Outlaw, 2007) estimated that means of 959 and 678 harbor 
seals from the SE Alaska and the Gulf of Alaska stock, respectively, 
harvested per year by Alaska Natives between 2000 and 2004, with 743 
and 747 seals, respectively, harvested in 2004. Means of 3 and 191 
Steller sea lions from the Eastern and Western Alaska stocks, 
respectively, were harvested per year by Alaska Natives between 2000 
and 2004, with 5 and 137 sea lions, respectively, harvested in 2004.
    Sea otters are harvested by Alaska Native hunters from SE Alaska to 
the Aleutian Islands. The USFWS monitors the harvest of sea otters in 
Alaska. The mean annual subsistence takes from 1996 to 2000 were 97, 
297, and 301 animals from the Southwest, Southcentral, and Southeast 
Alaska sea otter stocks, respectively (USFWS 2002 in Angliss and 
Outlaw, 2007).
    The subsistence harvest of sea otters occurs year-round in coastal 
communities throughout SE Alaska and the northern GOA. However, there 
is a general reduction in harvest during the summer months. Hunters are 
required to obtain tags for sea otter pelts from designated USFWS 
taggers located in all harvesting villages. The geographical 
distribution of the harvest is difficult to determine because reports 
are generated by marking location; harvest location is generally not 
recorded. Harvests can take place from a large geographic area 
surrounding each sea otter harvesting village.
    Since 1992, the seasonal distribution of harbor seal takes by 
Alaska Natives has shown two distinct peaks, one during spring, and the 
other during fall and early winter (Wolfe et al., 2003). The peak 
harbor seal harvest season for villages in SE Alaska and the northern 
GOA varies, but in general the months of highest harvest are September 
through December, with a smaller peak in March. Harvests are 
traditionally low from May through August, when harbor seals are 
raising pups and molting in SE Alaska. The Steller sea lion harvest in 
SE Alaska and the northern GOA is low throughout the year. In 2002, the 
only harvests in SE Alaska occurred during March and November, and in 
the northern GOA and Prince William Sound, harvests occurred in July, 
November, and December (Wolfe et al., 2003).
    Beluga whales do not occur regularly within the project area. Any 
occassional subsistence hunting of belugas that might occur in that 
area would be opportunistic hunting of extralimital animals.
    Gray whales are not hunted within the project area. Some of the 
gray whales that migrate through SE Alaska in spring and late autumn 
are hunted in Russian waters during summer, and a very limited 
subsistence has occurred in recent years off Washington. Any small-
scale disturbance effects that might occur in SE Alaska as a result of 
L-DEO's project would have no effect on the hunts for gray whales in 
those distant locations.
    The proposed survey could potentially impact the availability of 
marine mammals for harvest in a very small area immediately around the 
Langseth, and for a very short time period during seismic activities. 
Considering the limited time and locations for the planned seismic 
surveys, most of which are well offshore (Figure 1 of L-DEO's 
application), the proposed survey is not expected to have any 
significant impacts to the availability of Steller sea lions, harbor 
seals, or sea otters for subsistence harvest. Nonetheless, L-DEO will 
coordinate its activities with local communities, so that seismic 
operations will be conducted outside of subsistence hunting times and 
areas if possible.

 Table 4. The estimated 2002 harvest of harbor seals and Steller sea lions by Alaska Native communities near the
                                   proposed study area in the Gulf of Alaska.
----------------------------------------------------------------------------------------------------------------
                                     Estimated Total Harvest   Estimated Total Harvest     Peak of Harbor Seal
              Village                  of Harbor Seal \1\      of Steller Sea Lion \1\         Harvest \2\
----------------------------------------------------------------------------------------------------------------
Southeast Alaska                    1.8                       0.0                       October
Pelican
----------------------------------------------------------------------------------------------------------------
Yakutat                             137.5                     0.0                       March
----------------------------------------------------------------------------------------------------------------
Northern GOA and PWS                10.5                      0.0                       August
Chenega Bay
----------------------------------------------------------------------------------------------------------------
Cordova                             108.5                     3.5                       February
----------------------------------------------------------------------------------------------------------------
Tatilek                             14.9                      0.0                       February and March \3\
----------------------------------------------------------------------------------------------------------------
Valdez                              50.0                      0.0                       December
----------------------------------------------------------------------------------------------------------------
\1\ Includes estimates of both harvested and struck-and-lost animals. Totals are estimated from incomplete
  household surveys and were multiplied by a correction factor for missed households, which result in fractional
  estimates rather than whole number counts.
\2\ Maximum number harvested in 2002 reported by Wolfe et al. (2003).
\3\ Peak harvest in 2000 (Wolfe, 2001).


[[Page 45424]]

    Subsistence fisheries, on average, provide about 230 pounds (104.5 
kg) of food per person per year in rural Alaska (Wolfe, 2000). Of the 
estimated 43.7 million pounds of wild food harvested in rural Alaska 
communities annually, subsistence fisheries contributed approximately 
60 percent from finfish and 2 percent from shellfish. In the rural 
communities along the GOA, salmon species are the most targeted 
subsistence fish.
    In 2006, there were 609 residents in the Yakutat Region eligible to 
participate in the Alaska subsistence fishery. The Yakutat Region 
subsistence fishers rely mostly upon Pacific halibut, with 5,079-16,561 
kg taken in annual catch from 2003 to 2006 (Fall et al., 2007). Halibut 
typically are taken with a setline or hand-operated fishing gear, with 
the majority of the catch coming from the setline gear. The halibut 
fishery is open for subsistence harvest from 1 February to 31 December 
unless limited for expanded by emergency order. Salmon are also 
significant importance to subsistence fisheres in the Yakutat Region, 
with 6,918 harvested there in 2003 (ADFG, 2005). Set gillnets are thee 
preferred subsistence harvest method for salmon, and there are not 
restrictions on specific streams, nor are there daily or annual limits 
to the number of fish taken; there are restrictions to keep subsistence 
and commercial fisheries separate (ADFG, 2005). Bottomfish, Pacific 
herring, smelt, and crustaceans are also caught by substance fishers in 
the Yakutat Region.
    Seismic surveys can, at times, cause changes in the catchability of 
fish. L-DEO will minimize the potential to negatively impact the 
subsistence fish harvest by avoiding areas where subsistence fishers 
are fishing. Additionally, L-DEO will consult with each village near 
the planned project area to identify and avoid areas of potential 
conflict. These consultations will include all marine subsistence 
activities (marine mammals and fisheries).

Proposed Mitigation and Monitoring

    Mitigation and monitoring measures proposed to be implemented for 
the proposed seismic survey have been developed and refined during 
previous L-DEO seismic studies and associated environmental assessments 
(EAs), IHA applications, and IHAs. The mitigation and monitoring 
measures described herein represent a combination of the procedures 
required by past IHAs for other similar projects and on recommended 
best practices in Richardson et al. (1995), Pierson et al. (1998), and 
Weir and Dolman (2007). The measures are described in detail below.
    Mitigation measures that will be adopted during the proposed STEEP 
survey include: (1) speed or course alteration, provided that doing so 
will not compromise operational safety requirements; (2) power-down 
procedures; (3) shutdown procedures; (4) ramp-up procedures; and (5) 
special procedures for situations or species of particular concern, 
e.g., avoidance of critical habitat around Steller sea lion rookeries 
and haul-outs (see ``shut-down procedures'' and ``special procedures 
for situations and species of particular concern,'' below). The 
thresholds used for estimating take are also used in connection with 
proposed mitigation.

Vessel-based Visual Monitoring

    Marine Mammal Visual Observers (MMVOs) will be based aboard the 
seismic source vessel and will watch for marine mammals near the vessel 
during daytime airgun operations and during start-ups of airguns at 
night. MMVOs 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 shutdown of the airguns. When feasible, MMVOs will also 
make observations during daytime periods when the seismic system is not 
operating for comparison of sighting rates and animal behavior with vs. 
without airgun operations. Based on MMVO observations, the airguns will 
be powered down, or if necessary, shut down completely (see below), 
when marine mammals are detected within or about to enter a designated 
EZ. The MMVOs will continue to maintain watch to determine when the 
animal(s) are outside the safety radius, and airgun operations will not 
resume until the animal has left that zone. The predicted distances for 
the safety radius' are listed according to the sound source, water 
depth, and received isopleth in Table 1.
    During seismic operations in the GOA, at least three MMVOs will be 
based aboard the Langseth. MMVOs will be appointed by L-DEO with NMFS 
concurrence. At least one MMVO, and when practical two, will monitor 
the EZ for marine mammals during ongoing daytime operations and 
nighttime startups of the airguns. Use of two simultaneous MMVOs will 
increase the proportion of the animals present near the source vessel 
that are detected. MMVO(s) will be on duty in shifts of duration no 
longer than 4 hours. The vessel 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 regarding how to do so.
    The Langseth is a suitable platform for marine mammal observations. 
When stationed on the observation platform, the eye level will be 
approximately 17.8 m (58.4 ft) above sea level, and the observer will 
have a good view around the entire vessel. During daytime, the MMVO(s) 
will scan the area around the vessel systematically with reticle 
binoculars (e.g., 7x50 Fujinon), Big-eye binoculars (25x150), and with 
the naked eye. During darkness, night vision devices (NVDs) will be 
available (ITT F500 Series Generation 3 binocular-image intensifier or 
equivalent), when required. Laser rangefinding binoculars (Leica LRF 
1200 laser rangefinder or equivalent) will be available to assist with 
distance estimation. Those are useful in training MMVOs to estimate 
distances visually, but are generally not useful in measuring distances 
to animals directly.
    Speed or Course Alteration - If a marine mammal is detected outside 
the safety radius and, based on its position and the relative motion, 
is likely to enter the exclusion zone, the vessel's speed and/or direct 
course may be changed. This would be done if practicable while 
minimizing the effect on th planned science objectives. The activities 
and movements of the marine mammal(s) (relative to the seismic vessel) 
will then be closely monitored to determine whether the animals is 
approaching the applicable EZ. If the animal appears likely to enter 
the EZ, further mitigative actions will be taken, i.e., either further 
course alterations or a power down or shut down of the airguns. 
Typically, during seismic operations, major course and speed 
adjustments are often impractical when towing long seismic streamers 
and large source arrays, thus alternative mitigation measures (see 
below) will need to be implemented.
    Power-down Procedures - A power-down involves reducing the number 
of operating airguns in use to minimize the EZ, so that marine mammals 
are no longer in or about to enter this zone. A power-down of the 
airgun array to a reduced number of operating airguns may also occur 
when the vessel is moving from one seismic line to another. During a 
power down for mitigation, one airgun will be operated. The continued 
operation of at least one airgun is intended to alert marine mammals to 
the presence of the seismic vessel in the area. In contrast, a shut 
down occurs when all airgun activity is suspended.

[[Page 45425]]

    If a marine mammal is detected outside the EZ but is likely to 
enter it, and if the vessel's speed and/or course cannot be changed to 
avoid the animal(s) entering the EZ, the airguns will be powered down 
to a single airgun before the animal is within the EZ. Likewise, if a 
mammal is already within the EZ when first detected, the airguns will 
be powered down immediately. During a power down of the airgun array, 
the 40-in\3\ airgun will be operated. If a marine mammal is detected 
within or near the smaller EZ around that single airgun (see Table 1 of 
L-DEO's application and Table 1 above), all airguns will be shutdown 
(see next subsection).
    Following a power down, airgun activity will not resume until the 
marine mammal is outside the EZ for the full array. The animal will be 
considered to have cleared the EZ if it:
    (1) Is visually observed to have left the EZ; or
    (2) Has not been seen within the EZ for 15 minutes in the case of 
small odontocetes and pinnipeds; or
    (3) Has not been seen within the EZ for 30 minutes in the case of 
mysticetes and large odontocetes, including sperm, pygmy sperm, dwarf 
sperm, and beaked whales; or
    During airgun operations following a power-down (or shut down) and 
subsequent animal departure as above, the airgun array will resume 
operations following ramp-up procedures described below.
    Shutdown Procedures - The operating airgun(s) will be shutdown if a 
marine mammal is detected within or approaching the EZ for the then-
operating single 40 in\3\ airgun source while the airgun array is at 
full volume or during a power down. Airgun activity will not resume 
until the marine mammal has cleared the EZ or until the MMVO is 
confident that the animal has left the vicinity of the vessel. Criteria 
for judging that the animal has cleared the EZ will be as describing in 
the preceding subsection.
    Ramp-up Procedures - A ramp-up procedure will be followed when the 
airgun array begins operating after a specified-duration period without 
airgun operations or when a power down has exceeded that period. It is 
proposed that, for the present cruise, this period would be 
approximately 7 minutes. This period is based on the modeled 180-dB 
radius for the 36-airgun array (see Table 1 of L-DEO's application and 
Table 1 here) in relation to the planned speed of the Langseth while 
shooting. Similar periods (approximately 8-10 minutes) were used during 
previous L-DEO surveys.
    Ramp-up will begin with the smallest airgun in the array (40 
in\3\). Airguns will be added in a sequence such that the source level 
of the array will increase in steps not exceeding 6 dB per 5-minute 
period over a total duration of approximately 20-25 minutes. During 
ramp-up, the MMVOs will monitor the EZ, and if marine mammals are 
sighted, a course/speed change, power down, or shutdown will be 
implemented as though the full array were operational.
    If the complete EZ has not been visible for at least 30 min prior 
to the start of operations in either daylight or nighttime, ramp up 
will not commence unless at least one airgun (40 in\3\ or similar) has 
been operating during the interruption of seismic survey operations. 
Given these provisions, it is likely that the airgun array will not be 
ramped up from a complete shut down at night or in thick fog, because 
the other part of the EZ for that array will not be visible during 
those conditions. If one airgun has operated during a power down 
period, ramp up to full power will be permissible at night or in poor 
visibility, on the assumption that marine mammals will be alerted to 
the approaching seismic vessel by the sounds from the single airgun and 
could move away if they choose. Ramp up of the airguns will not be 
initiated if a marine mammal is isghted within or near the applicable 
EZ during the day or close to the vessel at night.

Special Procedures for Situations and Species of Particular Concern

    Several species of particular concern could occur in the study 
area. Special mitigation procedures will be used for those species, as 
follows:
    (1) Critical habitat around Steller sea lion rookeries and haul-
outs will be avoided;
    (2) The airguns will be shut down if a North Pacific right whale is 
sighted at any distance from the vessel;
    (3) Concentrations of humpack whales, fin whales, and sea otters 
will be avoided;
    (4) The seismic vessel will avoid areas where subsistence fishers 
are fishing; and
    (5) Because the sensitivity of beaked whales, approach to slopes 
and submarine canyons will be minimized, if possible. There are no 
submarine canyons in or near the study area, and only a limited amount 
of airgun operations is planned over slope during the proposed survey 
(Figure 1 of L-DEO's application).

Passive Acoustic Monitoring

    Passive Acoustic Monitoring (PAM) will take place to complement the 
visual monitoring program. Visual monitoring typically is not effective 
during periods of bad weather or at night, and even with good 
visibility, is unable to detect marine mammals when they are below the 
surface or beyond visual range. Acoustical monitoring can be used in 
addition to visual observations to improve detection, identification, 
localization, and tracking of cetaceans. The acoustic monitoring will 
serve to alert visual observers (if on duty) when vocalizing cetaceans 
are detected. It is only useful when marine mammals call, but it can be 
effective either by day or by night and does not depend on good 
visibility. It will be monitored in real time so visual observers can 
be advised when cetaceans are detected. When bearings (primary and 
mirror-image) to calling cetacean(s) are determined, the bearings will 
be relayed to the visual observer to help him/her sight the calling 
animal(s).
    The PAM system consists of hardware (i.e., hydrophones) and 
software. The ``wet end'' of the system consists of a low-noise, towed 
hydrophone array that is connected to the vessel by a ``hairy'' faired 
cable. The array will be deployed from a winch located on the back 
deck. A deck cable will connect from th winch to the main computer lab 
where the acoustic station and signal condition and processing system 
will be located. Th lead-in from the hydrophone array is approximately 
400 m (1,312 ft) long, and the active part of the hydrophone is 
approximately 56 m (184 ft) long. The hydrophone array is typically 
towed at depths <20 m (65.6 ft).
    The towed hydrophone array will be monitored 24 hours per day while 
at the survey area during airgun operations, and also during most 
periods when the Langseth is underway while the airguns are not 
operating. One Marine Mammal Observer (MMO) will monitor the acoustic 
detection system at any one time, by listening to the signals from two 
channels via headphones and/or speakers and watching the real time 
spectrographic display for frequency ranges produced by cetaceans. MMOs 
monitoring the acoustical data will be on shift for 1-6 hours. Besides 
the ``visual'' MMOs, an additional MMO with primary responsibility for 
PAM will also be aboard. However, all MMOs are expected to rotate 
through the PAM position, although the most experienced with acoustics 
will be on PAM duty more frequently.
    When a vocalization is detected, the acoustic MMO will, if visual 
observations are in progress, contact the MMVO immediately to alert 
him/her to the presence of the cetacean(s) (if they have not already 
been seen), and to

[[Page 45426]]

allow a power down or shutdown to be initiated, if required. The 
information regarding the call will be entered into a database. The 
data to be entered include an acoustic encounter identification number, 
whether it was linked with a visual sighting, date, time when first and 
last heard and whenever any additional information was recorded, 
position and water depth when first detected, bearing if determinable, 
species or species group (e.g., unidentified dolphin, sperm whale), 
types and nature of sounds heard (e.g., clicks, continuous, sporadic, 
whistles, creaks, burst pulses, strength of signal, etc.), and any 
other notable information. The acoustic detection can also be recorded 
for further analysis.

MMVO Data and Documentation

    MMVOs will record data to estimate the numbers of marine mammals 
exposed to various received sound levels and to document any apparent 
disturbance reactions or lack thereof. Data will be used to estimate 
the numbers of mammals potentially ``taken'' by harassment. They will 
also provide information needed to order a power down or shutdown of 
airguns when marine mammals are within or near the EZ. When a sighting 
is made, the following information about the sighting will be recorded:
    (1) Species, group size, age/size/sex categories (if determinable), 
behavior when first sighted and after initial sighting, heading (if 
consistent), bearing and distance from seismic vessel, sighting cue, 
apparent reaction to the airguns or vessel (e.g., none, avoidance, 
approach, paralleling, etc.), and behavioral pace.
    (2) Time, location, heading, speed, activity of the vessel 
(shooting or not), sea state, visibility, cloud cover, 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 airgun power 
down and shutdown, will be recorded in a standardized format. Data will 
be entered into a custom electronic database. The accuracy of the data 
entry will be verified by computerized data validity checks as the data 
are entered and by subsequent manual checking of the database. 
Preliminary reports will be prepared during the field program and 
summaries forwarded to the operating institution's shore facility and 
to NSF weekly or more frequently. MMVO observations will provide the 
following information:
    (1) The basis for decisions about powering down or shutting down 
airgun arrays.
    (2) Information needed to estimate the number of marine mammals 
potentially 'taken by harassment.' These data will be reported to NMFS 
per terms of MMPA authorizations or regulations.
    (3) Data on the occurrence, distribution, and activities of marine 
mammals in the area where the seismic study is conducted.
    (4) Data on the behavior and movement patterns of marine mammals 
seen at times with and without seismic activity.

Proposed Reporting

    A report will be submitted 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 will be 
submitted to NMFS, providing full documentation of methods, results, 
and interpretation pertaining to all monitoring. The 90-day report will 
summarize the dates and locations of seismic operations, all marine 
mammal sightings (dates, times, locations, activities, associated 
seismic survey activities). The report will also include estimates of 
the amount and nature of potential ``take'' of marine mammals by 
harassment or in other ways.

Endangered Species Act (ESA)

    Under section 7 of the ESA, NSF has begun consultation with the 
NMFS, Office of Protected Resources, Endangered Species Division on 
this proposed seismic survey. NMFS will also consult on the issuance of 
an IHA under section 101(a)(5)(D) of the MMPA for this activity. 
Consultation will be concluded prior to a determination on the issuance 
of the IHA.

National Environmental Policy Act (NEPA)

    NSF prepared an Environmental Assessment of a Marine Geophysical 
Survey by the R/V Marcus G.Langseth in the Gulf of Alaska, September 
2008. NMFS will either adopt NSF's EA or conduct a separate NEPA 
analysis, as necessary, prior to making a determination of the issuance 
of the IHA.

Preliminary Determinations

    NMFS has preliminarily determined that the impact of conducting the 
seismic survey in the Gulf of Alaska may result, at worst, in a 
temporary modification in behavior (Level B Harassment) of small 
numbers of 20 species of marine mammals. Further, this activity is 
expected to result in a negligible impact on the affected species or 
stocks. The provision requiring that the activity not have an 
unmitigable adverse impact on the availability of the affected species 
or stock for subsistence uses is not implicated for this proposed 
action.
    For reasons stated previously in this document, this determination 
is supported by: (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 fact that pinnipeds would have to be 
closer than 300 m (0.19 mi) in deep water, 450 m (0.28 mi) at 
intermediate depths, or 2,182 m (1.36 mi) in shallow water when a 
single airgun is in use from the vessel to be exposed to levels of 
sound (190 dB) and to have even a minimal chance of causing TTS; (3) 
the fact that cetaceans would have to be closer than 950 m (0.6 mi) in 
deep water, 1,425 m (0.9 mi) at intermediate depths, and 3,694 m (2.3 
mi) in shallow water when the full array is in use at a 9 m (29.5 ft) 
tow depth from the vessel to be exposed to levels of sound (180 dB) 
believed to have even a minimal chance of causing TTS; (4) the fact 
that marine mammals would have to be closer than 6,000 m (3.7 mi) in 
deep water, 6,667 m (4.1 mi) at intermediate depths, and 8,000 m (4.9 
mi) in shallow water when the full array is in use at a 9 m (29.5 ft) 
tow depth from the vessel to be exposed to levels of sound (160 dB) 
believed to have even a minimal chance of causing TTS; and (5) the 
likelihood that marine mammal detection ability by trained observers is 
high at that short distance from the vessel. As a result, no take by 
injury or death is anticipated, and the potential for temporary or 
permanent hearing impairment is very low and will be avoided through 
the incorporation of the proposed mitigation measures.
    While the number of potential incidental harassment takes will 
depend on the distribution and abundance of marine mammals in the 
vicinity of the survey activity, the number of potential harassment 
takings is estimated to be small, less than a few percent of any of the 
estimated population sizes, and has been mitigated to the lowest level 
practicable through incorporation of the measures mentioned previously 
in this document.

Proposed Authorization

    As a result of these preliminary determinations, NMFS proposes to 
issue an IHA to L-DEO for conducting a marine geophysical survey in the 
Gulf of

[[Page 45427]]

Alaska from August-September, 2008, provided the previously mentioned 
mitigation, monitoring, and reporting requirements are incorporated.

    Dated: July 30, 2008.
James H. Lecky,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. E8-17949 Filed 8-4-08; 8:45 am]
BILLING CODE 3510-22-S