Incidental Takes of Marine Mammals During Specified Activities; Marine Geophysical Survey in Southeast Asia, March-July 2009, 78294-78317 [E8-30365]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 73, Number 246 (Monday, December 22, 2008)]
[Notices]
[Pages 78294-78317]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E8-30365]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XL89


Incidental Takes of Marine Mammals During Specified Activities; 
Marine Geophysical Survey in Southeast Asia, March-July 2009

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

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

-----------------------------------------------------------------------

SUMMARY:  NMFS has received an application from the Lamont-Doherty 
Earth Observatory (L-DEO), a part of Columbia University, for an 
Incidental Harassment Authorization (IHA) to take small numbers of 
marine mammals, by harassment, incidental to conducting a marine 
seismic survey in Southeast (SE) Asia during March-July 2009. Pursuant 
to the Marine Mammal Protection Act (MMPA), NMFS requests comments on 
its proposal to authorize L-DEO to incidentally take, by Level B 
harassment only, small numbers of marine mammals during the 
aforementioned activity.

DATES:  Comments and information must be received no later than January 
21, 2009.

ADDRESSES:  Comments on the application should be addressed to Michael 
Payne, Chief, Permits, Conservation and Education Division, Office of 
Protected Resources, National Marine Fisheries Service, 1315 East-West 
Highway, Silver Spring, MD 20910-3225. The mailbox address for 
providing email comments is PR1.0648-XL89@noaa.gov. 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

[[Page 78295]]

the contact listed below (see FOR FURTHER INFORMATION CONTACT), or 
visiting the internet at: https://www.nmfs.noaa.gov/pr/permits/
incidental.htm.
    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 United 
States citizens who engage in a specified activity (other than 
commercial fishing) within a specified geographical region if certain 
findings are made and either regulations are issued or, if the taking 
is limited to harassment, a notice of a proposed authorization is 
provided to the public for review.
    Authorization for incidental taking shall be granted if NMFS finds 
that the taking will have a negligible impact on the species or 
stock(s), will not have an unmitigable adverse impact on the 
availability of the species or stock(s) for subsistence uses, and if 
the permissible methods of taking and requirements pertaining to the 
mitigation, monitoring and reporting of such takings are set forth. 
NMFS has defined ``negligible impact'' in 50 CFR 216.103 as ``...an 
impact resulting from the specified activity that cannot be reasonably 
expected to, and is not reasonably likely to, adversely affect the 
species or stock through effects on annual rates of recruitment or 
survival.''
    Section 101(a)(5)(D) of the MMPA established an expedited process 
by which citizens of the United States can apply for an authorization 
to incidentally take small numbers of marine mammals by harassment. 
Except with respect to certain activities not pertinent here, the MMPA 
defines ``harassment'' as:
    any act of pursuit, torment, or annoyance which (i) has the 
potential to injure a marine mammal or marine mammal stock in the 
wild [``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 
small numbers of marine mammals. Within 45 days of the close of the 
comment period, NMFS must either issue or deny issuance of the 
authorization.

Summary of Request

    On October 27, 2008, NMFS received an application from L-DEO for 
the taking, by Level B harassment only, of small numbers of marine 
mammals incidental to conducting, under cooperative agreement with the 
National Science Foundation (NSF), a marine seismic survey in SE Asia. 
The funding for the Taiwan Integrated Geodynamics Research (TAIGER) 
survey is provided by the NSF. The proposed survey will encompass the 
area 17 30'-26 30' N, 113 30'-126 E within the Exclusive Economic Zones 
(EEZ) of Taiwan, China, Japan, and the Philippines, and on the high 
seas, and is scheduled to occur from March 21 to July 14, 2009. Some 
minor deviation from these dates is possible, depending on logistics 
and weather.
    Taiwan is one of only a few sites of arc-continent collision 
worldwide; and one of the primary tectonic environments for large scale 
mountain building. The primary purpose of the TAIGER project is to 
investigate the processes of mountain building, a fundamental set of 
processes which plays a major role in shaping the face of the Earth. 
The vicinity of Taiwan is particularly well-suited for this type of 
study, because the collision can be observed at different stages of its 
evolution, from incipient, to mature, and finally to post-collision.
    As a result of its location in an ongoing tectonic collision zone, 
Taiwan experiences a great number of earthquakes, most are small, but 
many are large and destructive. This project will provide a great deal 
of information about the nature of the earthquakes around Taiwan and 
will lead to a better assessment of the earthquake hazards in the area. 
The information obtained from this study will help the people and the 
earthquake hazards in the area. The information obtained from this 
study will help the people and government of Taiwan to better prepare 
for future seismic events and may thus mitigate some of the loss of 
life and economic disruptions that will inevitably occur.
    The proposed action is planned to take place in the territorial 
seas and EEZ's of foreign nations, and will be continuous with the 
activity that takes place on the high seas. NMFS does not authorize the 
incidental take of marine mammals in the territorial seas of foreign 
nations, as the MMPA does not apply in those waters. However, NMFS 
still needs to calculate the level of incidental take in territorial 
seas as part of the proposed issuance of an IHA in regards to NMFS' 
analysis of small numbers and negligible impact determination.

Description of the Specified Activity

    The planned survey will involve one source vessel, the R/V Marcus 
G. Langseth (Langseth), which will occur in SE Asia. The Langseth will 
deploy an array of 36 airguns (6,600 in\3\) as an energy source at a 
tow depth of 6-9 m (20-30 ft). The receiving system will consist of a 
hydrophone streamer and approximately 100 ocean bottom seismometers 
(OBSs). The Langseth will deploy an 8 km (5 mi) long streamer for most 
transects requiring a streamer; however, a shorter streamer (500 m to 
2km or 1,640 ft to 1.2 mi) will be used during surveys in Taiwan 
(Formosa) Strait. As the airgun array is towed along the survey lines, 
the hydrophone streamer will receive the returning acoustic signals and 
transfer the data to the on-board processing system. The OBSs record 
the returning acoustic signals internally for later analysis. The OBSs 
to be used for the TAIGER program will be deployed and retrieved 
numerous times by a combination of 4 or 5 Taiwanese support vessels, as 
well as the Langseth. The Langseth will also retrieve 20 OBSs that were 
deployed in the study area during previous years to record earthquake 
activity.
    Approximately 100 OBSs will be deployed during the survey. OBSs 
will likely be deployed and retrieved by the Langseth as well as a 
combination of 4 to 5 Taiwanese vessels. The Taiwanese vessels to be 
used include two 30 m (98.4 ft) vessels (the R/V Ocean Researcher 2 and 
the R/V Ocean Researcher 3) and two vessels greater than 60 m (196.8 
ft) in length (R/V Fisheries Research I and the Navy ship Taquan). The 
R/V Ocean Research I may also be used if the Langseth is not used to 
deploy OBSs. The OBS deployment spacing will vary depending on the 
number of instruments available and shiptime. The nominal spacing is 15 
km (9.3 mi), but this will vary from as little as 5 km (3.1 mi) to 
perhaps as much as 25 km (15.5 mi). The OBSs will be deployed and 
recovered several (2 to 4) times. 60 of the 100 OBSs may be deployed 
from the Langseth. All OBSs will be retrieved at the end of the study.
    Up to 3 different types of OBSs may be used during the 2009 
program. The Woods Hole Oceanographic Institution (WHOI) ``D2'' OBS has 
a height of

[[Page 78296]]

approximately 1 m (3.3 ft) and a maximum diameter of 50 cm. The anchor 
is made of hot-rolled steel and weighs 23 kg (50.7 lbs). The anchor 
dimensions are 2.5 x 30.5 x 38.1 cm. The LC4x4 OBS from the Scripps 
Institution of Oceanography (SIO) has a volume of approximately 1 m\3\ 
(3.3 ft\2\), with an anchor that consists of a large piece of steel 
grating (approximately 1 m\2\ or 3.3 ft\2\). Taiwanese OBSs will also 
be used; their anchor is in the shape of an 'x' with dimensions of 51-
76 cm\2\ (1.7-2.5 ft\2\). Once the OBS is ready to be retrieved an 
acoustic release transponder interrogates the OBS at a frequency of 9-
11 kHz, and a response is received at a frequency of 9-13 kHz. The burn 
wire release assembly is then activated, and the instrument is released 
from the anchor to float to the surface.
    The planned seismic survey will consist of approximately 15,902 km 
(9,881 mi) of transect lines within the South and East China Seas as 
well as the Philippine Sea, with the majority of the survey effort 
occurring in the South China Sea. The survey will take place in water 
depths ranging from approximately 25 to 6,585 m (82-21,598 ft), but 
most of the survey effort (approximately 80 percent) will take place in 
water greater than 1,000 m (3,280 ft), 13 percent will take place in 
intermediate depth waters (100-1,000 m or 328-3,280 ft), and 7 percent 
will occur in shallow depth water (less than 100 m or 328 ft).
    All planned geophysical data acquisition activities will be 
conducted by L-DEO with onboard assistance by the scientists who have 
proposed the study. The scientific team consists of Dr. Francis Wu 
(State University of New York at Binghamton) and Dr. Kirk McIntosh 
(University of Texas at Austin, Institute of Geophysics). 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 12 kHz Simrad 
EM 120 multibeam echosounder (MBES) and a 3.5 kHz sub-bottom profiler 
(SBP) will be operated from the Langseth continuously throughout the 
TAIGER cruise.

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 4 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/hr (4-5 kt). 
When not towing seismic survey gear, the Langseth can cruise at 20-24 
km/hr (11-13 kt). When the Langseth is towing the airgun array as well 
as the hydrophone streamer, the turning rate of the vessel is limited 
to 5 degrees per minute. Thus, the maneuverability of the vessel is 
limited during operations with the streamer. 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 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 airgun array will consist of a mixture of Bolt 1500LL and 
1900LL airguns. The airguns array will be configured as 4 identical 
linear arrays or ``strings'' (see Figure 2 in L-DEO's application). 
Each string will have 10 airguns; the first and last airguns in the 
strings 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 4 
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 140 m (459 ft) behind the vessel. The shot interval will 
be relatively short (approximately 25-50 m or 82-164 ft or 10-25 s) for 
multi-channel seismic surveying with the hydrophone streamer, and 
relatively long (approximately 100-125 m or 328-410 ft or 45-60 s) when 
recording data on the OBSs. The firing pressure of the array is 1,900 
psi. During firing, a brief (approximately 0.1 s) pulse of sound is 
emitted. The airguns will be silent during the intervening periods.
    The tow depth of the array will be 6-9 m (20-30 ft). The depth at 
which the source is towed (particularly a large source) affects the 
maximum near-field output and the shape of its frequency spectrum. If 
the source is towed at 9 m (30 ft), the effective source level for 
sound propagating in near-horizontal directions is higher than if the 
array is towed at shallow depths (see Figure 3-5 of L-DEO's 
application). However, the nominal source levels of the array (or the 
estimates of the sound that would be measured from a theoretical point 
source emitting the same total energy as the airgun array) at various 
tow depths are nearly identical. In L-DEO's calculations, a tow depth 
of 9 m is assumed at all times.
    Because the actual source is a distributed 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 (265 
dB re 1 microPam, 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.
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 millisecond (ms) in 
duration and each ensonifying a section that extends 1 fore-aft. The 
nine successive transmissions span an overall cross-track angular 
extent of about 150 , 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 seconds (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.

[[Page 78297]]



--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                        Predicted RMS Distances (m)
        Source and Volume              Tow Depth (m)            Water Depth      -----------------------------------------------------------------------
                                                                                          190 dB                  180 dB                  160 dB
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                  ......................  Deep                    12                      40                      385
                                                         -----------------------------------------------------------------------------------------------
Single Bolt airgun                6-9*                    Intermediate            18                      60                      578
                                                         -----------------------------------------------------------------------------------------------
40 in\3\                          ......................  Shallow                 150                     296                     1050
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                  ......................  Deep                    220                     710                     4670
                                                         -----------------------------------------------------------------------------------------------
4 strings                         6-7                     Intermediate            330                     1065                    5189
                                                         -----------------------------------------------------------------------------------------------
36 airguns                        ......................  Shallow                 1600                    2761                    6227
                                 -----------------------------------------------------------------------------------------------------------------------
6600 in\3\                        ......................  Deep                    300                     950                     6000
                                                         -----------------------------------------------------------------------------------------------
                                  8-9                     Intermediate            450                     1425                    6667
                                                         -----------------------------------------------------------------------------------------------
                                  ......................  Shallow                 2182                    3694                    8000
--------------------------------------------------------------------------------------------------------------------------------------------------------
Table 1. Predicted distances to which sound levels >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 from the 36 airgun array, as well as a single airgun, used during the Central American
  SubFac and STEEP Gulf of Alaska survey, and planned during the TAIGER SE Asia survey. *The tow depth has minimal effect on the maximum near-field
  output and the shape of the frequency spectrum for the single 40 in3 airgun; thus, the predicted safety radii are essentially the same at each tow
  depth. The most precautionary distances (i.e., for the deepest tow depth, 9m) are shown

    Because the predictions in Table 1 are based in part on empirical 
correction factors derived from acoustic calibration of airgun 
configurations different from 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 (EZ) proposed above for use 
during the TAIGER cruise, if the data are appropriate and available for 
use at the time of the survey.

Proposed Dates, Duration, and Region of Activity

    The survey will encompass the area 17[deg] 30'-26 30' N, 113[deg] 
30'-126 E within the EEZs of Taiwan, China, Japan, and the Philippines. 
The vessel will approach mainland Taiwan within 1 km (0.6 mi) and China 
within 10 km (6.2 mi). The closest approach to the Ryuku Islands will 
be 16 km (9.9 mi). Although the survey will occur at least 32 km (29.9 
mi) from Luzon, Philippines, survey lines will take place approximately 
8 km (5 mi) from some of the Babuyan and Batan islands. Water depths in 
the survey area range from approximately 25 to 6,585 m. The TAIGER 
program consists of 4 legs, each starting and ending in Kao-hsiung, 
Taiwan. The first leg is expected to occur from approximately March 21 
to April 19, 2008 and will include the survey lines in the South China 
Sea. The second leg is scheduled for April 20 to June 7 and will 
include survey lines in Luzon Strait and the Philippine Sea. The third 
leg (approximately June 8-20) will involve OBS recovery by the Langseth 
only; no seismic acquisition will occur during this leg. The fourth 
leg, consisting of the survey lines immediately around Taiwan, is 
scheduled to occur from June 21 to July 14, 2009. The program will 
consist of approximately 103 days of seismic acquisition. The exact 
dates of the activities depend on logistics and weather conditions.

Description of Marine Mammals in the Proposed Activity Area

    A total of 34 cetacean species, including 25 odontocete (dolphins 
and small- and large-toothed whales) species and 9 mysticetes (baleen 
whales) are known to occur in the proposed TAIGER study area (see Table 
2 of L-DEO's application). Cetaceans and pinnipeds are managed by NMFS 
and are the subject of this IHA application. Information on the 
occurrence, distribution, population size, and conservation status for 
each of the 34 marine mammal species that may occur in the proposed 
project area is presented in the Table 2 of L-DEO's application as well 
as here in the table below (Table 2). The status of these species is 
based on the U.S. Endangered Species Act (ESA), the International Union 
for Conservation of Nature (IUCN) Red List of Threatened Species, and 
Convention on International Trade in Endangered Species (CITES). 
Several species are listed as Endangered under the ESA, including the 
Western North Pacific gray, North Pacific right, sperm, humpback, fin, 
sei, and blue whales. In addition, the Indo-Pacific humpback dolphin is 
listed as Near Threatened and the finless porpoise is listed as 
Vulnerable under the 2008 IUCN Red List of Threatened Species (IUCN, 
2008).
    Although the dugong may have inhabited waters off Taiwan, it is no 
longer thought to occur there (March et al., n.d.; Chou, 2004; Perrin 
et al., 2005). Similarly, although the dugong was once widespread 
through the Philippines, current data suggest that it does not inhabit 
the Batan or Babuyan Islands or northwestern Luzon (Marsh et al., n.d.; 
Perrin et al., 2005), where seismic operations will occur. However, the 
dugong does occur off northeastern Luzon (Marsh et al., n.d.; Perrin et 
al., 2005) outside the study area. In China, it is only known to 
inhabit the waters off Guangxi and Guangdong and the west coast of 
Hanain Island (Marsh et al., n.d.; Perrin et al., 2005), which do not 
occur near the study area. It is rare in the Ryuku Islands, but can be 
sighted in Okinawa, particularly off the east coast of the island 
(Yoshida and Trono, 2004; Shirakihara et al., 2007); some individuals 
may have previously occurred in the southern most of the Ryuku Islands, 
Yaeyama (Marsh et al., n.d.), but these animals have not been 
documented there recently (Shirakihara et al., 2007).
    Wang et al. (2001a) noted that during the spring/summer off 
southern Taiwan,

[[Page 78298]]

the highest number of marine mammal sightings and species occur during 
April and June. The number of sightings per survey effort and the 
number of species were highest directly west of the southern tip of 
Taiwan and northeast off the southern tip.
    Table 2 below outlines the cetacean 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.

  Table 2. The occurrence, habitat, regional abundance, conservation status, best and maximum density estimates, number of marine mammals that could be
   exposed to sound level at or above 160dB re 1microPa, best estimate of number of individuals exposed, and best estimate of number of exposures per
             marine mammal in or near the proposed seismic survey area in SE Asia. See Tables 2-4 in L-DEO's application for further detail.
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                  Occurrence in Study                        Regional Population                          Density/          Density/
            Species                 Area in SE Asia           Habitat                Size                ESA\a\       1000km\b\ (best)   1000km\c\ (max)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Mysticetes
-------------------------------
Western North Pacific gray      Rare                     Coastal           131\d\                   EN                0                 0
 whale
(Eschrichtius robustus)
--------------------------------------------------------------------------------------------------------------------------------------------------------
North Pacific right whale       Rare                     Pelagic and       Less than 100\e\         EN                0                 0
(Eubalaena japonica)                                      coastal
--------------------------------------------------------------------------------------------------------------------------------------------------------
Humpback whale                  Uncommon                 Mainly nearshore  938-1107\f\              EN                0.89              1.33
(Megaptera novaeangliae)                                  waters and
                                                          banks
--------------------------------------------------------------------------------------------------------------------------------------------------------
Minke whale                     Uncommon                 Pelagic and       25,000\g\                NL                0.03              0.04
(Balaenoptera acutorostrata)                              coastal
--------------------------------------------------------------------------------------------------------------------------------------------------------
Bryde's whale                   Common                   Pelagic and       20,000-30,000\e,h\       NL                0.27              0.41
(Balaenoptera brydei)                                     coastal
--------------------------------------------------------------------------------------------------------------------------------------------------------
Omura's whale                   Uncommon                 Pelagic and       N.A.                     NL                0.03              0.04
(Balaenoptera omurai)                                     coastal
--------------------------------------------------------------------------------------------------------------------------------------------------------
Sei whale                       Uncommon                 Primarily         7,260-12,620\i\          EN                0.03              0.04
(Balaenoptera borealis)                                   offshore,
                                                          pelagic
--------------------------------------------------------------------------------------------------------------------------------------------------------
Fin whale                       Uncommon                 Continental       13.620-18.680\j\         EN                0.03              0.04
(Balaenoptera physalus)                                   slope, mostly
                                                          pelagic
--------------------------------------------------------------------------------------------------------------------------------------------------------
Blue whale                      Uncommon                 Pelagic and       N.A.                     EN                0.03              0.04
(Balaenoptera musculus)                                   coastal
--------------------------------------------------------------------------------------------------------------------------------------------------------
Odontocetes
-------------------------------
Sperm whale                     Uncommon                 Usually pelagic   26,674\k\                NL                0.03              0.04
(Physeter macrocephalus)                                  and deep seas
--------------------------------------------------------------------------------------------------------------------------------------------------------
Pygmy sperm whale               Uncommon                 Deep waters off   N.A.                     NL                0                 0
(Kogia breviceps)                                         shelf
--------------------------------------------------------------------------------------------------------------------------------------------------------
Dwarf sperm whale               Common?                  Deep waters off   11,200\e\                NL                4.25              6.68
(Kogia sima)                                              the shelf
--------------------------------------------------------------------------------------------------------------------------------------------------------
(Kogia sp.)                     Common?                  Deep waters off   N.A.                     NL                0.26              0.40
                                                          the shelf
--------------------------------------------------------------------------------------------------------------------------------------------------------
Cuvier's beaked whale           Likely Common            Pelagic           20,000\e\                NL                0.34              0.75
(Ziphius cavirostris)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Longman's beaked whale          Rare                     Deep water        N.A.                     NL                N.A.              N.A.
(Indopacetus pacificus)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Blainville's beaked whale       Uncommon?                Pelagic           25,300\l\                NL                0.89              1.60
(Mesoplodon densirostris)
--------------------------------------------------------------------------------------------------------------------------------------------------------

[[Page 78299]]

 
Ginkgo-toothed beaked whale     Rare                     Pelagic           N.A.                     NL                N.A.              N.A.
(Mesoplodon ginkgodens)
--------------------------------------------------------------------------------------------------------------------------------------------------------
(Mesoplodon sp.)                Uncommon?                Pelagic           N.A.                     NL                1.55              1.60
--------------------------------------------------------------------------------------------------------------------------------------------------------
Unidentified beaked whale       Rare                     Pelagic           N.A.                     NL                0.72              0.94
--------------------------------------------------------------------------------------------------------------------------------------------------------
Rough-toothed beaked dolphin    Common                   Deep water        146,000 ETP\e\           NL                1.33              5.44
(Steno bredanensis)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Indo-Pacific humpback dolphin   Uncommon                 Coastal           1,680 China + Taiwan\e\  NL                24.30             35.36
(Sousa chinensis)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Common bottlenose dolphin       Common                   Coastal and       243,500 ETP\e\           NL                24.30             35.36
(Tursiops truncatus)                                      oceanic, shelf
                                                          break
--------------------------------------------------------------------------------------------------------------------------------------------------------
Indo-Pacific bottlenose         Common?                  Coastal and       N.A.                     NL                43.60             65.40
 dolphin                                                  shelf waters
(Tursiops aduncus)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Pacific white-sided dolphin     Rare                     Coastal and       930,000-990,000\e\       NL                N.A.              N.A.
(Lagenorhynchus obliquidens)                              pelagic
--------------------------------------------------------------------------------------------------------------------------------------------------------
Pantropical spotted dolphin     Common                   Coastal and       800,000 ETP\e\           NL                120.80            140.97
(Stenella attenuata)                                      pelagic
--------------------------------------------------------------------------------------------------------------------------------------------------------
Spinner dolphin                 Common                   Coastal and       800,000 ETP\e\           NL                54.84             88.89
(Stenella longirostris)                                   pelagic
--------------------------------------------------------------------------------------------------------------------------------------------------------
Striped dolphin                 Common                   Coastal and       1,000,000 ETP\e\         NL                0.20              0.32
(Stenella coeruleoalba)                                   pelagic
--------------------------------------------------------------------------------------------------------------------------------------------------------
Fraser's dolphin                Common                   Waters greater    289,000 ETP\e\           NL                96.84             124.14
(Lagenodelphis hosei)                                     than 1,000 m
--------------------------------------------------------------------------------------------------------------------------------------------------------
Short-beaked common dolphin     Rare                     Shelf and         3,000,000 ETP\e\         NL                N.A.              N.A.
(Delphinus delphis)                                       pelagic,
                                                          seamounts
--------------------------------------------------------------------------------------------------------------------------------------------------------
Long-beaked common dolphin      Uncommon                 Coastal           N.A.                     NL                0.05              0.12
(Delphinus capensis)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Risso's dolphin                 Common                   Pelagic           175,000 ETP\e\           NL                41.88             67.18
(Grampus griseus)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Melon-headed whale              Common?                  Oceanic           45,000 ETP\e\            NL                13.37             20.86
(Peponocephala electra)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Pygmy killer whale              Uncommon                 Deep,             39,000 ETP\e\            NL                2.01              3.16
(Feresa attenuata)                                        pantropical
                                                          waters
--------------------------------------------------------------------------------------------------------------------------------------------------------
False killer whale              Common?                  Pelagic           40,000\n\                NL                4.56              4.77
(Pseudorca crassidens)
--------------------------------------------------------------------------------------------------------------------------------------------------------

[[Page 78300]]

 
Killer whale                    Uncommon?                Widely            8,500 ETP\e\             NL                1.00              1.73
(Orcinus orca)                                            distributeds
--------------------------------------------------------------------------------------------------------------------------------------------------------
Short-finned pilot whale        Common?                  Mostly pelagic,   500,000 ETP\e\           NL                3.83              6.43
(Globicephala macrorhynchus)                              relief
                                                          topography
--------------------------------------------------------------------------------------------------------------------------------------------------------
Finless porpoise                Common?                  Coastal           5,220-10,220             NL                4.36              6.54
(Neophocaena phocaenoides)                                                 Japan + HK\e\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Sirenians
-------------------------------
Dugong                          Uncommon?                Coastal           N.A.                     EN                N.A.              N.A.
(Dugong dugon)
--------------------------------------------------------------------------------------------------------------------------------------------------------
N.A. - Data not available or species status was not assessed, ETP - Eastern Tropical Pacific, HK = Hong Kong
\a\ U.S. Endangered Species Act: EN = Endangered, T = Threatened, NL = Not listed
\b\ Best estimate as listed in Table 3 of the application.
\c\ Maximum estimate as listed in Table 3 of the application.
\d\ Vladimirov et al. (2008)
\e\ North Pacific unless otherwise indicated (Jefferson et al., 2008)
\f\ Western North Pacific (Calambokidis et al., 2008)
\g\ Northwest Pacific and Okhotsk Sea (IWC, 2007a)
\h\ Kitakado et al. (2008)
\i\ Tillman (1977)
\j\ Ohsumi and Wada (1974)
\k\ Western North Pacific (Whitehead, 2002b)
\l\ ETP; all Mesoplodon spp. (Wade and Gerrodette, 1993)
\m\ IUCN states that this species should be re-assessed following taxonomic classification of the two forms. The chinensis-type would be considered
  vulnerable (IUCN, 2008)
\n\ ETP (Wade and Gerrodette, 1993)

Potential Effects on Marine Mammals

Potential Effects of Airguns

    The sounds from airguns might result in one or more of the 
following: tolerance, masking of natural sounds, behavioral 
disturbances, temporary or permanent hearing impairment, and 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 root mean square (rms) 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 Appendix B 
(3) 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 B (5) of L-DEO's 
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

[[Page 78301]]

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. However in exceptional situations, reverberation occurs for 
much or all of the interval between pulses (Simard et al., 2005; Clark 
and Gagnon, 2006). 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; Holst et al., 2005a,b, 2006). In the northeast 
Pacific Ocean, blue whale calls have been recorded during a seismic 
survey off Oregon (McDonald et al., 1995). Among odontocetes, there has 
been one report that sperm whales 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; 
Potter et al., 2007). Also, the sounds important to small odontocetes 
are predominantly at much higher frequencies than the airgun sounds, 
thus further limiting the potential for masking. In general, masking 
effects of seismic pulses are expected to be minor, given the normally 
intermittent nature of seismic pulses. Masking effects on marine 
mammals are discussed further in Appendix B (4) of L-DEO's application.
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,'' or 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, bowhead, and sperm 
whales and on ringed seals. Less detailed data are available for some 
other species of baleen whales, small toothed whales, and sea otters, 
but for many species there are no data on responses to marine seismic 
surveys.
    Baleen Whales - Baleen whales generally tend to avoid operating 
airguns, but avoidance radii are quite variable. Whales are often 
reported to show no overt reactions to pulses from large arrays of 
airguns at distances beyond a few kilometers, even though the airgun 
pulses remain well above ambient noise levels out to much longer 
distances. However, as reviewed in Appendix B (5) of L-DEO's 
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 demonstrated 
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 4-15 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, and studies 
summarized in Appendix B(5) of L-DEO's application have shown that some 
species of baleen whales, notably bowhead and humpback whales, at times 
show strong avoidance at received levels lower than 160-170 dB re 1 
microPa (rms).
    Responses of humpback whales to seismic surveys have been studied 
during migration, on the summer feeding grounds, and on Angolan winter 
breeding grounds; there has also been discussion of effects on the 
Brazilian wintering grounds. McCauley et al. (1998, 2000a) studied the 
responses of humpback whales off Western Australia to a full-scale 
seismic survey with a 16-airgun, 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. The 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). The initial avoidance response generally occurred at distances 
of 5-8 km (3.1-5 mi) from the airgun array and 2 km (1.2 mi) from the 
single airgun. However, some individual humpback whales, especially 
males, approached within distances of 100-400 m (328-1,312 ft), where 
the maximum received level was 179 dB re 1 microPa (rms).
    Humpback whales on their summer feeding grounds in southeast Alaska 
did not exhibit persistent avoidance when exposed to seismic pulses 
from a 1.64-L (100 in\3\) airgun (Malme et al., 1985). Some humpbacks 
seemed ``startled'' at received levels of 150-169 dB re 1 ?Pa 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

[[Page 78302]]

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 
and subject to alternative explanations (IAGC, 2004). Also, the 
evidence was not consistent with subsequent results from the same area 
of Brazil (Parente et al., 2006), or with 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).
    There are no data on reactions of right whales to seismic surveys, 
but results from the closely-related bowhead whale show that their 
responsiveness can be quite variable depending on the activity 
(migrating vs. feeding). Bowhead whales migrating west across the 
Alaskan Beaufort Sea in autumn, in particular, are unusually 
responsive, with substantial avoidance occurring out to distances of 
20-30 km (12.4-18.6 mi) from a medium-sized airgun source at received 
sound levels of around 120-130 dB re 1 microPa (rms) (Miller et al., 
1999; Richardson et al., 1999; see Appendix B (5) of 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. Nonetheless, subtle but statistically significant 
changes in surfacing-respiration-dive cycles were evident upon 
statistical analysis (Richardson et al., 1986). In summer, bowheads 
typically begin to show avoidance reactions at a received level of 
about 160-170 dB re 1 microPa (rms) (Richardson et al., 1986; Ljungblad 
et al., 1988; Miller et al., 2005a).
    Reactions of migrating and feeding (but not wintering) gray whales 
to seismic surveys have been studied. Malme et al. (1986, 1988) studied 
the responses of feeding Eastern Pacific gray whales to pulses from a 
single 100 in\3\ airgun off St. Lawrence Island in the northern Bering 
Sea. 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 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), along with data on gray 
whales off British Columbia (Bain and Williams, 2006).
    Various species of Balaenoptera (blue, sei, fin, Bryde's, and minke 
whales) have occasionally been reported in areas ensonified by airgun 
pulses (Stone, 2003; MacLean and Haley, 2004; Stone and Tasker, 2006). 
Sightings by observers on seismic vessels off the United Kingdom from 
1997 to 2000 suggest that, at times of good sightability, sighting 
rates for mysticetes (mainly fin and sei whales) were similar when 
large arrays of airguns were shooting and not shooting (Stone, 2003; 
Stone and Tasker, 2006). However, these whales tended to exhibit 
localized avoidance, remaining significantly (on average) from the 
airgun array during seismic operations compared with non-seismic 
periods (Stone and Tasker, 2006). In a study off Nova Scotia, Moulton 
and Miller (2005) found little difference in sighting rates (after 
accounting for water depth) and initial sighting distances of 
balaenopterid whales when airguns were operating vs. silent. However, 
there were indications that these whales were more likely to be moving 
away when seen during airgun operations. Similarly, ship-based 
monitoring studies of blue, fin, sei, and minke whales offshore of 
Newfoundland (Orphan Basin and Laurentian Sub-basin) found no more than 
small differences in sighting rates and swim direction during seismic 
vs. non-seismic periods (Moulton et al., 2005, 2006a,b).
    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 with substantial increases in the population over 
recent years, despite intermittent seismic exploration and much ship 
traffic in that area for decades (see Appendix A in Malme et al., 1984; 
Richardson et al., 1995; Angliss and Outlaw, 2008). The Western Pacific 
gray whale population did not seem affected by a seismic survey in its 
feeding ground during a prior year (Johnson et al., 2007). Bowhead 
whales continued to travel to the eastern Beaufort Sea each summer, and 
their numbers have increased notably, despite seismic exploration in 
their summer and autumn range for many years (Richardson et al., 1987). 
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, systematic studies on sperm 
whales have 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; Potter et al., 2007; Weir, 2008).
    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 avoidance of operating seismic vessels (Goold, 1996a,b,c; 
Calambokidis and Osmek, 1998; Stone, 2003; Moulton and Miller, 2005; 
Holst et al., 2006; Stone and Tasker, 2006; Weir, 2008). 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 (Moulton and Miller, 2005). 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 (Stone and 
Tasker, 2006; Weir, 2008). In most cases, the avoidance radii for 
delphinids appear to be small, on the order of 1 km (0.62 mi) or less, 
and some individuals show no apparent avoidance. The beluga is a 
species that (at least at times) shows long-distance avoidance of 
seismic vessels. Aerial surveys during seismic operations in the 
southeastern Beaufort Sea during summer recorded much lower sighting 
rates of beluga whales within 10-20 km (6.2-12.4 mi) compared with 20-
30 km (mi) from an operating airgun array, and observers on seismic 
boats in that area rarely see belugas (Miller et al., 2005; Harris et 
al., 2007).

[[Page 78303]]

    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 (Stone, 
2003; Moulton et al., 2005, 2006a; Stone and Tasker, 2006; Weir, 2008). 
In most cases, the whales do not show strong avoidance and continue to 
call (see Appendix B in L-DEO's EA). However, controlled exposure 
experiments in the Gulf of Mexico indicate that foraging effort is 
somewhat altered upon exposure to airgun sounds (Jochens et al., 2006).
    There are almost no specific data on the behavioral reactions of 
beaked whales to seismic surveys. However, northern bottlenose whales 
(Hyperodon ampullatus) continued to produce high-frequency clicks when 
exposed to sound pulses from distant seismic surveys (Laurinolli and 
Cochrane, 2005; Simard et al., 2005). 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 EA).
    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 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 
temporary threshold shift (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 and (to a limited degree) pinnipeds 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 mar