Incidental Takes of Marine Mammals During Specified Activities; Low-Energy Marine Seismic Surveys in the Santa Barbara Channel, November 2008, 50760-50778 [E8-20014]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 73, Number 168 (Thursday, August 28, 2008)]
[Notices]
[Pages 50760-50778]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E8-20014]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XJ24


Incidental Takes of Marine Mammals During Specified Activities; 
Low-Energy Marine Seismic Surveys in the Santa Barbara Channel, 
November 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 the Scripps Institute of 
Oceanography (SIO) for an Incidental Harassment Authorization (IHA) to 
take small numbers of marine mammals, by harassment, incidental to 
conducting a seismic survey within the Santa Barbara Channel, 
California. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS 
requests comments on its proposal to authorize SIO to take, by Level B 
harassment only, small numbers of marine mammals incidental to 
conducting a marine seismic survey in November, 2008.

DATES: Comments and information must be received no later than 
September 29, 2008.

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 e-mail comments is PR1.0648-XJ24@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 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.

[[Page 50761]]


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

SUPPLEMENTARY INFORMATION:

Background

    Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) 
direct the Secretary of Commerce 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 June 27, 2008, NMFS received an application from SIO for the 
taking, by Level B harassment only, of small numbers of 16 species of 
marine mammals incidental to conducting a twelve-day, low-energy marine 
seismic survey within the Santa Barbara Channel, CA, in November 2008. 
The funding for this research survey is provided by the National 
Science Foundation (NSF).
    The purpose of the proposed study is to test the feasibility of 
extending the paleoclimate record from Santa Barbara Basin established 
in 1992 and 2005 from ~700,000 years ago back to ~1.2 million years 
using detailed 3D modeling of the structure and outcrop stratigraphy of 
the northern shelf, to locate optimal core sites, and high-resolution 
multichannel seismic (MCS) reflection site surveys, test coring, and 
core analyses in the northern shelf and mid-channel areas. The planned 
seismic survey (including turns) will consist of approximately 600 km 
of survey lines using a standard 45-in \3\ GI airgun and approximately 
500 km of survey lines using a mini-sparker or boomer. The seismic 
surveys will identify subsequent optimal and safe coring strategies 
suitable for recovering a continuous paleoclimate record from the 
shallow marine sediments in Santa Barbara Basin in the future as part 
of the Integrated Ocean Drilling Program (IODP).

Description of the Specified Activity

    The planned survey will involve one source vessel, the seismic ship 
R/V Melville, owned by the U.S. Navy and operated by SIO. The Melville 
is expected to depart San Diego and spend approximately 12 days 
conducting the survey and piston coring activities in November 2008. 
Seismic operations will be conducted during daylight hours only for 1-2 
days at each of five sites encompassing the small area approximately 
34-34.5[deg] N, 119.5-120[deg] W, north and northwest of Santa Cruz 
Island in the Santa Barbara Channel off southern California (see Figure 
1 in SIO's application). The seismic program will consist of grids of 
closely-spaced lines in each of 5 survey areas. Line spacing will be 
100-400 m. 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. Water depths in the 
survey area range from <50 m to ~580 m. The seismic survey will be 
conducted in the territorial waters of the U.S., partly in California 
state waters.
    At three deeper-water sites outside state waters, a small 45-in\3\ 
GI airgun will be used, but will likely be reduced to 25- or 35-in\3\. 
At two shallow-water sites that cross into California state waters, a 
1.5-kJ electromechanical boomer or a 2-kJ electric sparker system will 
be used, depending on water depth and seafloor conditions, and 
depending on which source provides the highest resolution and best sub-
seafloor signal penetration. The two systems will not operate 
concurrently and, in general, the boomer source likely will be 
preferred. As the boomer, sparker, or GI airgun are towed along the 
survey lines, a towed 72-channel, 450 m hydrophone streamer will 
receive the returning acoustic signals and transfer the data to the on-
board processing system. Given the relatively short streamer length 
behind the vessel, the turning rate of the vessel while the gear is 
deployed is much higher than the limit of five degrees per minute for a 
seismic vessel towing a streamer of more typical length (>1 km). Thus, 
the maneuverability of the vessel is not limited much during 
operations.
    In addition to the GI airgun, sparker, and boomer, a towed chirp 
system, a multibeam echosounder (MBES), and a sub-bottom profiler (SBP) 
will be used at various times during the cruise. The chirp system will 
be used in tandem with the seismic sources, or will be used separately 
to locate optimal piston core sites, up to 4 hours at a time to a 
maximum of 8-10 hours per day. A 3.5-kHz SBP will be used to help 
verify seafloor conditions at possible coring sites, and will also be 
used in tandem with a MBES during transit to and from the Santa Barbara 
Channel area to collect additional seafloor bathymetric data.

Vessel Specifications

    The Melville has a length of 85 m, a beam of 14.0 m, a maximum 
draft of 5.0 m, and can accommodate 23 crew and 86 scientists. Its 
gross tonnage is 2516 and is powered by two 1385-hp Propulsion General 
Electric motors and a 900-hp retracting Azimuthing bow thruster. The 
vessel will operate at a speed of ~7.4-8 km/h (4-4.3 knots) during 
seismic acquisition. When not towing seismic survey gear, the Melville 
cruises at 21.7 km/h (11.7 knots) and has a maximum speed of 25.9 km/h 
(14 knots). It has a normal operating range of approximately 18,630 km. 
The Melville will also serve as the platform from which vessel-based 
marine mammal observers will watch for marine mammals and sea turtles 
before and during airgun operations.

[[Page 50762]]

Acoustic Source Specifications

Seismic Airguns
    The Melville will operate one small 45-in\3\ GI airgun but will 
likely reduce the chamber size to 25-35-in\3\. However, in case that is 
not possible, the specifications provided below are for a 45-in\3\ GI 
airgun (Table 1). Seismic pulses will be emitted at intervals of 3 
seconds. At a vessel speed of approximately 4 knots (7.4 km/h), the 3-s 
spacing corresponds to a shot interval of approximately 6 m.
    If possible, the generator chamber of the GI airgun, the one 
responsible for introducing the sound pulse into the ocean, will be set 
to 25 in\3\. The injector chamber also will be set to the same 25-in\3\ 
size and will inject air into the previously generated bubble to 
maintain its shape. This does not introduce more sound into the water. 
The airgun will be towed 21 m behind the Melville at a depth of 2 m. 
The variation of the sound pressure field of that GI-gun set to its 
original 45-in\3\ size and towed at a depth of 2.5 m has been modeled 
by L-DEO in relation to distance and direction from the GI airgun. At 
its reduced chamber size of 25 in\3\, these numbers will be further 
reduced. For comparison, the peak source sound level of the 45-in\3\ 
gun is 225.3 dB re 1 [mu] Pa, whereas the peak source sound level of a 
USGS GI airgun with chamber sizes reduced to 25 in\3\ is approximately 
218 dB re 1 [mu]Pa[middot]m. More information on characteristics of 
airgun sounds can be found in Appendix A in the SIO's EA.

 Table 1--Specifications of GI-Airgun Proposed To Be Used During the SIO
                      Seismic Survey, November 2008
------------------------------------------------------------------------
                        GI-airgun specifications
-------------------------------------------------------------------------
                                           GI airgun of 45 in\3\ or GI
             Energy source                      airgun of 25 in\3\
------------------------------------------------------------------------
Source output (downward) (45 in\3\)....  0-pk is 1.8 bar-m (225.3 dB re
                                          1 [mu]Pa[middot]mp); pk-pk is
                                          3.4 bar-m (230.7 dB re 1
                                          [mu]Pa[middot]mp-p).
Source output (downward) (25 in\3\)....  approx. 218 dB re 1
                                          [mu]Pa[middot]mp.
Towing depth of energy source..........  2 meters.
Air discharge volume...................  approx. 45 in\3\ or 25 in\3\.
Dominant frequency components..........  0-188 Hz (45 in\3\) or <500 Hz
                                          (25 in\3\).
------------------------------------------------------------------------

Electric Sparker

    The Melville will use a minisparker system similar to the SQUID 
2000\TM\ sparker system manufactured by Applied Acoustic Engineering, 
Inc. This minisparker includes electrodes mounted on a small pontoon 
sled that simultaneously discharge electric current through the 
seawater to an electrical ground, creating an electrical arc that 
momentarily vaporizes water between positive and negative leads. The 
collapsing bubbles produce an omnidirectional pulse. The pontoon sled 
that supports the minisparker is towed on the sea surface, 
approximately 5 m behind the ship.
    Source characteristics of the SQUID 2000\TM\ provided by the 
manufacturer show a source level of 209 dB re 1 [mu]Parms. This is at 
the full power level of 2 kJ. The power level of this source may be 
reduced to provide more consistent, reliable output signals if 
necessary. The amplitude spectrum of this pulse indicates that most of 
the sound energy lies between 150 Hz and 1700 Hz, and the peak 
amplitude is at 900 Hz. The output sound pulse of the minisparker has a 
duration of about 0.8 ms. When operated at sea for the proposed MCS-
reflection survey, the minisparker will be discharged every 0.5-3 
seconds.

Electromechanical Boomer

    A boomer is a broad-band sound source operating in the 100-2500 Hz 
range. By sending electrical energy from the power supply through wire 
coils, spring-loaded plates in the boomer transducer are electrically 
charged causing the plates to repel, thus generating an acoustic pulse. 
The boomer planned for this cruise has three plates with a power input 
of 500 J per plate. The source level 219 dB re 1 [mu] Papeak; 209 dB re 
1 [mu]Parms and the boomer will be towed on the surface. When operated 
at sea for the proposed MCS-reflection survey, the boomer will be 
discharged every 0.5-2 seconds.

Multibeam Echosounders and Sub-Bottom Profilers

    Along with the seismic operations, two additional acoustical data 
acquisition systems will be operated during part of the R/V Melville's 
cruise but only in transit, not during airgun use. The ocean floor will 
be mapped with the 12-kHz Simrad EM120 multi-beam echosounder (MBES) in 
transit to the survey area, and a 3.5-kHz sub-bottom profiler (SBP) 
will also be operated along with the MBES and also to help verify sea 
floor conditions at possible coring sites.
    The Melville will operate a Kongsberg-Simrad EM120 Multi Beam Echo 
Sounder (MBES). The Kongsberg-Simrad EM120 operates at 11.25-12.6 kHz, 
and is mounted in the hull of the Melville. It operates in several 
modes, depending on water depth. In the proposed survey, it will be 
used in automatic mode, changing from ``Shallow'' to ``Medium'' mode at 
450 m and from ``Medium'' to ``Deep'' mode at 1000 m. In ``Shallow'' 
mode, the beamwidth is 2[deg] fore-aft and the estimated maximum source 
level is 232 dB re 1 [mu]Parms. Each ``ping'' consists of three 
successive fan-shaped transmissions, each 2 ms in duration with a delay 
of 3 ms between pulses for successive sectors. In ``Medium'' mode, the 
beamwidth is 1[deg] or 2[deg] fore-aft and the estimated maximum source 
levels are 232 or 226 dB re 1 [mu]Parms. Each ``ping'' consists of 
three successive fan-shaped transmissions, each 5 ms in duration with a 
delay of 6 ms between pulses for successive sectors. In ``Deep'' mode, 
the beamwidth is 1[deg] or 2[deg] fore-aft and the estimated maximum 
source levels are 239 or 233 dB re 1 [mu]Parms. Each ``ping'' consists 
of nine successive fan-shaped transmissions, each 15 ms in duration 
with a delay of 16 ms between pulses for successive sectors. The MBES 
will be used during transit to and from the Santa Barbara Channel area 
to collect additional sea floor bathymetric data.
    In addition, an Edgetech 512i Chirp sub-bottom profiler (SBP) will 
also be a high resolution system that provides full-spectrum 
(``chirp'') imaging. The system is towed either at the water surface or 
slightly submerged, depending on the application and water depth. The 
512i has a source level of 198 dB re 1 [mu]Parms. It has a frequency 
range of 500 Hz-12 kHz with pulse widths from 5 ms to 50 ms depending 
on the application. The chirp system will be used in tandem with the 
seismic sources, or will be used separately to locate optimal piston 
core sites, up to 4 hours at a time to a maximum of 8-10 hours per day.

[[Page 50763]]

Safety Radii

    To aid in estimating the number of marine mammals that are likely 
to be taken, pursuant to the MMPA, and in developing effective 
mitigation measures, NMFS applies certain acoustic thresholds that 
indicate the received level at which Level A or Level B harassment 
would occur in marine mammals where exposed.
    The distance from the sound source at which an animal would be 
exposed to these different received sound levels may be estimated and 
is typically referred to as safety radii. These safety radii are 
specifically used to help NMFS estimate the number of marine mammals 
likely to be harassed by the proposed activity and in deciding how 
close a marine mammal may approach an operating sound source before the 
applicant will be required to power-down or shut down the sound source.

GI-Airguns

    NMFS has established a 160 dB re 1 [mu]Parms behavioral harassment 
(Level B) threshold for both cetaceans and pinnipeds and a 190 dB and 
180 dB re 1 [mu]Parms threshold for the potential onset of injury 
(Level A) for pinnipeds and cetaceans, respectively. Received sound 
levels have been modeled by Lamont-Doherty Earth Observatory of 
Columbia University (L-DEO) for a number of airgun configurations, 
including one 45-in\3\ GI airgun, in relation to distance and direction 
from the GI airgun. The model does not allow for bottom interactions, 
and is most directly applicable to deep water. Based on the modeling, 
estimates of the maximum distances from the GI airgun where sound 
levels of 190, 180, 160 dB re 1 [mu]Parms are predicted to be received 
in deep (>1000-m) water are shown in Table 2. Because the model results 
are for a 2.5-m tow depth, which is deeper than the proposed 2-m tow 
depth, the distances in Table 2 slightly overestimate safety and 
harassment isopleth distances.
    Empirical data concerning the 180- and 160-dB distances were 
acquired based on measurements during the acoustic verification study 
conducted by L-DEO in the northern Gulf of Mexico from 27 May to 3 June 
2003 (Tolstoy et al. , 2004). Although the results are limited, the 
data show that radii around the airguns where the received level would 
be 180 dB re 1 [mu]Parms, the safety thresholds applicable to cetaceans 
(NMFS 2000), vary with water depth. Similar depth-related variation is 
likely in the 190-dB distances applicable to pinnipeds. Correction 
factors were developed for water depths 100-1000 m and <100 m. The 
empirical data indicate that, for deep water (>1000 m), the L-DEO model 
tends to overestimate the received sound levels at a given distance 
(Tolstoy et al. , 2004). However, to be precautionary pending 
acquisition of additional empirical data, it is proposed that safety 
radii during GI airgun operations in deep water will be the values 
predicted by L-DEO's model. Therefore, the assumed 190- and 180 dB re 1 
[mu] Pa radii are 8 m and 23 m, respectively, and the 160 dB radius for 
this depth is 330 m (Table 2).
    Empirical measurements were not conducted for intermediate depths 
(100-1000m). On the expectation that results will be intermediate 
between those from shallow and deep water, a 1.5x correction factor is 
applied to the estimates provided by the model for deep water 
situations. This is the same factor that was applied to the model 
estimates during L-DEO cruises in 2003. The assumed 190 and 180 dB re 1 
[mu] Pa radii in intermediate-depth water are 12m and 35m, 
respectively, and the 160 dB radius for this depth is 220m (Table 2). 
Additional information regarding how the safety radii were calculated 
and how the empirical measurements were used to correct the modeled 
numbers may be found in the SIO application and EA. The proposed survey 
using the GI airgun will occur only in depths approximately 150-580m; 
therefore the 12m, 35m, and 330m radii are applicable.

  Table 2--Distances To Which Sound Levels >=190, 180, and 160 dB re 1
  [mu]Parms Could Be Received From the 45-in\3\ GI Airgun That Will Be
Used During the Seismic Surveys in the Santa Barbara Channel in November
      2008. Distances are Based on Model Results Provided by L-DEO
------------------------------------------------------------------------
                                    Estimated distances (m) at received
                                                   levels
           Water depth            --------------------------------------
                                      190 dB       180 dB       160 dB
------------------------------------------------------------------------
>1000m...........................            8           23          220
100-1000m........................           12           35          330
------------------------------------------------------------------------

Boomer/Sparker

    Either the boomer or the mini sparker will be used in State waters. 
The boomer likely will be used and its source level is higher than that 
of the mini sparker; therefore, the propagation distances for the 
boomer will be used. Received sound levels from the boomer proposed for 
use in shallow water have not been modeled or measured. However, 
Burgess and Lawson (2001) measured received sound levels from a boomer 
with a source level of 203 dB re 1 [mu]Parms in water depths 12-14m, 
and Greene (2006) measured received sound levels from a boomer with a 
source level of 188.8 dB re 1 [mu]Parms in water depths 37-48m, both in 
the Alaskan Beaufort Sea. The distances at which sound levels 190-, 
180-, and 160-dB re 1 [mu]Parms were received are given in Table 3 
together with the distances predicted using a spherical spreading 
model. In each case, more so for the larger source level, the modeled 
distance exceeded the measured distance. As a conservative (i.e., 
precautionary) measure, the modeled distances will be used to 
calculation take estimates. The source level of the boomer is p, 
corresponding roughly to 209 dB re 1 [mu]Pa[middot]mrms. Based on the 
spherical spreading model, distances to which sound levels >=190, 180, 
170, and 160 dB re 1 [mu]Parms could be received from the boomer are 9, 
28, 90, and 280, respectively (Table 3).

[[Page 50764]]



Table 3--Distances To Which Received Sound Levels >=190, 180, and 160 dB
  re 1 [mu]Parms Were Measured for Two Boomers in the Alaskan Beaufort
  Sea, and Distances Predicted by a Spherical Spreading Model for Those
      Sources and for the Boomer To Be Used in the Proposed Surveys
------------------------------------------------------------------------
                                   Estimated distances (m) at received
 Boomer source level (dB re 1                    levels
    [mu]Pa[middot]mrms) and    -----------------------------------------
           distance                190 dB        180 dB        160 dB
------------------------------------------------------------------------
203, measured.................          <1             2            22
203, modeled..................           4.5          16           140
188.8, measured...............           0.9           2.3          14.6
188.8, modeled................           1             2.7          27.5
209 (this study), modeled.....           9            28           280
------------------------------------------------------------------------

Description of Marine Mammals in the Activity Area

    Thirty-two species of marine mammals, including 17 odontocetes, 8 
mysticetes, 6 pinnipeds, and the southern sea otter (Enhydra lutris) 
could occur in the Santa Barbara Channel (SBC). In the U.S., sea otters 
are managed by the U.S. Fish and Wildlife Service (USFWS). The SIO is 
in the process of requesting consultation from the USFWS for impacts on 
sea otters; therefore, they will not be discussed further in this 
document. Of the 32 species, 20 are considered residents or regular 
visitors to the Channel Islands (CINMS), 14 of which are at least 
seasonally common to abundant in the SBC. The other 12 species are rare 
to extremely rare. Table 4 indicated relative abundance, density, 
habitat, status, and requested take for each species. Seven of the 
marine mammal species which could in the action area are endangered or 
threatened under the U.S. Endangered Species Act (ESA), including the 
North Pacific right whale (Eubalaena japonica), humpback whale 
(Megaptera novaeangliae), sei whale (Balaenoptera borealis), fin whale 
(Balaenoptera physalus), blue whale (Balenoptera musculus), sperm whale 
(Physeter macrocephalus), and southern resident killer whales (Orcinus 
orca). However, not all these species are expected to be harassed from 
the proposed seismic survey due to rarity in the area and the small 
harassment isopleth distances. Table 4 below outlines the species by 
the requested number of takes by both instances and individuals. Number 
of exposed individuals and number of exposures are listed with respect 
to the 160dB re 1 [mu]Pa threshold. Cetaceans and pinnipeds would not 
be exposed to sound levels at or above 180 and 190 dB, respectively, 
due to implementation of mitigation measures (see Proposed Mitigation 
section). For more information on the status, distribution, and 
seasonal distribution of species or stocks of marine mammals which 
could be in the action area, please refer to SIO's application, section 
IV.

  Table 4--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 1[mu]Pa, 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 the Santa Barbara Channel (SBC). See Tables 3-5 in SIO's Application for Further Detail
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                  Density/     Density/      Number of
            Species               Occurrence in SBC        Habitat        Abundance    ESA \1\   1000km\2\    1000km\2\     individuals      Number of
                                                                                                   (best)       (max)         exposed        exposures
--------------------------------------------------------------------------------------------------------------------------------------------------------
North Pacific right whale......  Extremely rare;     Offshore,               100-200  EN               0            0                  0               0
                                  winter-spring       occasionally
                                  vagrant.            inshore.
Gray whale.....................  Common when         Coastal except           18,813  NL               0            0                  0               0
                                  migrating; rare     near Channel
                                  Oct-Nov.            Islands.
Humpback whale.................  All year, common    Mainly nearshore          >6000  EN               0.22         0.33               0               0
                                  May-Jun, Sep-Dec.   waters and banks.
Minke whale....................  All year, common    Pelagic and                9000  NL               0.36         0.54               0               0
                                  spring-fall.        coastal.
Bryde's whale..................  Rare..............  Pelagic and              13,000  NL               0            0                  0               0
                                                      coastal.
Sei whale......................  Very rare.........  Mostly pelagic....  7260-12,620  EN               0            0                  0               0
Fin whale......................  Uncommon all year.  Slope, mostly       13,620-18,6  EN               0.55         0.82               0               0
                                                      pelagic.                    80
Blue whale.....................  All year, common    Pelagic and                1186  EN               5.45         8.15               2               4
                                  Jun--ct.            coastal.
Sperm whale....................  Uncommon all year.  Usually deep             24,000  EN               0.31         0.47               0               0
                                                      pelagic.
Pygmy sperm whale..............  Uncommon all year.  Deep waters off            N.A.  NL              21.78        32.68               6              15
                                                      shelf.
Dwarf sperm whale..............  Very rare.........  Deep waters off          11,200  NL               0            0                  0               0
                                                      shelf.
Cuvier's beaked whale..........  Rare all year.....  Slope and pelagic.       20,000  NL               1.44         2.16               1               1

[[Page 50765]]

 
Baird's beaked whale...........  Rare all year.....  Slope and pelagic.         6000  NL               0            0                  0               0
Mesoplodon spp. beaked whale...  Rare all year.....  Slope and pelagic.         1024  NL               0            0                  0               0
Offshore bottlenose dolphin....  Common all year...  Offshore, slope,           3257  NL               6.12         9.18               2               4
                                                      shelf.
Coastal bottlenose dolphin.....  Common all year...  Within 1 km of              323  NL               6.12         9.18               2               2
                                                      shore.
Striped dolphin................  Rare..............  Off continental       1,824,000  NL               3.37         5.05               1               2
                                                      shelf.
Short-beaked common dolphin....  Common all year...  Shelf, pelagic,         487,622  NL            1364.41      2046.61             394             942
                                                      high relief.
Long-beaked common dolphin.....  Common all year...  Coastal, high              1893  NL             174.69       262.04              50             121
                                                      relief.
Pacific white-sided dolphin....  All year, common    Offshore, slope...      931,000  NL              33           49.5               10              23
                                  fall-winter.
Northern right whale dolphin...  Common only         Slope, offshore          15,305  NL              16.8         25.2                5              12
                                  winter, spring.     waters.
Risso's dolphin................  Common all year...  Shelf, slope,            12,093  NL              18.35        27.53               5              13
                                                      seamounts.
Killer whale...................  Uncommon all year.  Widely distributed         8500  NL               0            0                  0               0
Short-finned pilot whale.......  Rare all year.....  Mostly pelagic,         160,200  NL               0            0                  0               0
                                                      high-relief.
Dall's porpoise................  Uncommon all year.  Shelf, slope,            57,549  NL               9.17        13.76               3               0
                                                      offshore.
Harbor porpoise................  Rare..............  Coastal...........      202,988  NL               0            0                  0               0
Guadalupe fur seal.............  Extremely rare....  Coastal...........         7408  T              N/A          N/A                  0               0
Northern fur seal..............  Uncommon all year.  Pelagic, offshore.      721,935  NL             N/A          N/A                  0               0
California sea lion............  Common all year...  Coastal, shelf....      238,000  NL             100          300                 29              69
Steller sea lion...............  Rare all year.....  Coastal, shelf....       44,584  T              N/A          N/A                  0               0
Harbor seal....................  Common all year...  Coastal...........       34,233  NL             N/A          N/A                  0               0
Northern elephant seal.........  All year, common    Coastal, pelagic        124,000  NL             N/A          N/A                  0               0
                                  Dec-Mar peak.       when migrating.
--------------------------------------------------------------------------------------------------------------------------------------------------------


--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                             Number of
             Species                 Occurrence in SBC         Habitat           Abundance      ESA \1\      Number of      individuals   Requested take
                                                                                                           exposures \2\    exposed \3\         \4\
--------------------------------------------------------------------------------------------------------------------------------------------------------
North Pacific right whale........  Extremely rare;       Offshore,                   100-200  EN                       0               0               0
                                    winter-spring         occasionally
                                    vagrant.              inshore.
Gray whale.......................  Common when           Coastal except near          18,813  NL                       0               0               0
                                    migrating; rare Oct-  Channel Islands.
                                    Nov.
Humpback whale...................  All year, common May- Mainly nearshore              >6000  EN                       0               0               2
                                    Jun, Sep-Dec.         waters and banks.
Minke whale......................  All year, common      Pelagic and coastal            9000  NL                       0               0               0
                                    spring-fall.
Bryde's whale....................  Rare................  Pelagic and coastal          13,000  NL                       0               0               0
Sei whale........................  Very rare...........  Mostly pelagic.....     7260-12,620  EN                       0               0               0
Fin whale........................  Uncommon all year...  Slope, mostly         13,620-18,680  EN                       0               0               2
                                                          pelagic.
Blue whale.......................  All year, common Jun- Pelagic and coastal            1186  EN                       4               2               2
                                    Oct.
Sperm whale......................  Uncommon all year...  Usually deep                 24,000  EN                       0               0               8
                                                          pelagic.
Pygmy sperm whale................  Uncommon all year...  Deep waters off                N.A.  NL                      15               6               9
                                                          shelf.

[[Page 50766]]

 
Dwarf sperm whale................  Very rare...........  Deep waters off              11,200  NL                       0               0               0
                                                          shelf.
Cuvier's beaked whale............  Rare all year.......  Slope and pelagic..          20,000  NL                       1               1               1
Baird's beaked whale.............  Rare all year.......  Slope and pelagic..            6000  NL                       0               0               0
Mesoplodont beaked whale.........  Rare all year.......  Slope and pelagic..            1024  NL                       0               0               0
Offshore bottlenose dolphin......  Common all year.....  Offshore, slope,               3257  NL                       4               2               3
                                                          shelf.
Coastal bottlenose dolphin.......  Common all year.....  Within 1 km of                  323  NL                       4               2               3
                                                          shore.
Striped dolphin..................  Rare................  Off continental           1,824,000  NL                       2               1               1
                                                          shelf.
Short-beaked common dolphin......  Common all year.....  Shelf, pelagic,             487,622  NL                     942             394             591
                                                          high relief.
Long-beaked common dolphin.......  Common all year.....  Coastal, high                  1893  NL                     121              50              76
                                                          relief.
Pacific white-sided dolphin......  All year, common      Offshore, slope....         931,000  NL                      23              10              14
                                    fall-winter.
Northern right whale dolphin.....  Common only winter,   Slope, offshore              15,305  NL                      12               5               7
                                    spring.               waters.
Risso's dolphin..................  Common all year.....  Shelf, slope,                12,093  NL                      13               5               8
                                                          seamounts.
Killer whale.....................  Uncommon all year...  Widely distributed.            8500  NL                       0               0               0
Short-finned pilot whale.........  Rare all year.......  Mostly pelagic,             160,200  NL                       0               0               0
                                                          high-relief.
Dall's porpoise..................  Uncommon all year...  Shelf, slope,                57,549  NL                       0               3               4
                                                          offshore.
Harbor porpoise..................  Rare................  Coastal............         202,988  NL                       0               0               0
Guadalupe fur seal...............  Extremely rare......  Coastal............            7408  T                        0               0               0
Northern fur seal................  Uncommon all year...  Pelagic, offshore..         721,935  NL                       0               0               0
California sea lion..............  Common all year.....  Coastal, shelf.....         238,000  NL                      69              29              87
Steller sea lion.................  Rare all year.......  Coastal, shelf.....          44,584  T                        0               0               0
Harbor seal......................  Common all year.....  Coastal............          34,233  NL                       0               0              20
Northern elephant seal...........  All year, common Dec- Coastal, pelagic            124,000  NL                       0               0               0
                                    Mar peak.             when migrating.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ U.S. Endangered Species Act: EN = Endangered, T = Threatened, NL = Not listed
\2\ Best estimate as listed in Table 5 of the application
\3\ Best estimate as listed in Table 5 of the application
\4\ Requested number of takes as listed in Table 5 of application

Potential Effects of the Proposed Activity on Marine Mammals

Potential Effects of Airgun Sounds on Marine Mammals

    The effects of sounds from airguns might include one or more of the 
following: tolerance, masking of natural sounds, behavioral 
disturbance, temporary or permanent hearing impairment, or non-auditory 
physical or physiological effects (Richardson et al., 1995; Gordon et 
al., 2004; Nowacek et al., 2007; Southall et al., 2007). Given the 
small size of the GI gun planned for the present project, effects are 
anticipated to be considerably less than would be the case with a large 
array of airguns. It is very unlikely that there would be any cases of 
temporary or, especially, permanent hearing impairment or any 
significant non-auditory physical or physiological effects. Also, 
behavioral disturbance is expected to be limited to relatively short 
distances. 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 and perhaps 
some other 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 is expected to be localized and 
short-term.

Tolerance

    Numerous studies have shown that pulsed sounds from airguns are 
often readily detectable in the water at distances of many kilometers. 
A summary of the characteristics of airgun pulses, is provided in 
Appendix A of NSF's EA prepared for this survey. Several studies have 
also shown that marine mammals at distances more than a few kilometers 
from operating seismic vessels often show no apparent response 
(tolerance) (see Appendix A of NSF's EA). That is often true even in 
cases when the pulsed sounds must be readily audible to the animals 
based on measured received levels and the hearing sensitivity of that 
mammal group. Although various baleen whales, toothed whales, and (less 
frequently) pinnipeds have been shown to react behaviorally to airgun 
pulses under some conditions, at other times mammals of all three types 
have shown no overt reactions. In general, pinnipeds usually seem to be 
more tolerant of exposure to airgun pulses than cetaceans, with the 
relative responsiveness of baleen and toothed whales being variable.

Masking

    Introduced underwater sound may, through masking, reduce the 
effective communication distance of a marine mammal species if the 
frequency of the source is close to that used as a signal

[[Page 50767]]

by the marine mammal, and if the anthropogenic sound is present for a 
significant fraction of the time (Richardson et al., 1995).
    Masking effects of pulsed sounds (even from large arrays of 
airguns) on marine mammal calls and other natural sounds are expected 
to be limited, although there are very few specific data on this. 
Because of the intermittent nature (one pulse every 105 or 210 seconds) 
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 (e.g., Simard et al., 2005; Clark and Gagnon, 
2006) which could mask calls. Some baleen and toothed whales are known 
to continue calling in the presence of seismic pulses, and their calls 
can usually be heard between the seismic pulses (e.g., Richardson et 
al., 1986; McDonald et al., 1995; Greene et al., 1999; Nieukirk et al., 
2004; Smultea et al., 2004; Holst et al., 2005a,b, 2006). In the 
northeastern Pacific Ocean, blue whale calls have been recorded during 
a seismic survey off Oregon (McDonald et al., 1995). Among odontocetes, 
there has been one report that sperm whales ceased calling when exposed 
to pulses from a very distant seismic ship (Bowles et al., 1994), but 
more recent studies found that they continued calling in the presence 
of seismic pulses (Madsen et al., 2002c; Tyack et al., 2003; Smultea et 
al., 2004; Holst et al., 2006; Jochens et al., 2006). Dolphins and 
porpoises commonly are heard calling while airguns are operating (e.g., 
Gordon et al., 2004; Smultea et al., 2004; Holst et al., 2005a,b; 
Potter et al., 2007). The sounds important to small odontocetes are 
predominantly at much higher frequencies than are the dominant 
components of airgun sounds, thus limiting the potential for masking. 
In general, masking effects of seismic pulses are expected to be minor, 
given the normally intermittent nature of seismic pulses and the 
Melville being the only seismic vessel operating in the area for a 
limited time. Masking effects on marine mammals are discussed further 
in Appendix A of NSF's EA.

Disturbance Reactions

    Disturbance includes a variety of effects, including subtle to 
conspicuous changes in behavior, movement, and displacement. Based on 
NMFS (2001, p. 9293), NRC (2005), and Southall et al. (2007), it is 
assumed that simple exposure to sound, or brief reactions that do not 
disrupt behavioral patterns in a potentially significant manner, do not 
constitute harassment or ``taking,'' with ``potentially significant'' 
meaning ``in a manner that might have deleterious effects to the well-
being of individual marine mammals or their populations''.
    Reactions to sound, if any, depend on species, state of maturity, 
experience, current activity, reproductive state, time of day, and many 
other factors (Richardson et al., 1995; Wartzok et al., 2004; Southall 
et al., 2007). If a marine mammal does react briefly to an underwater 
sound by changing its behavior or moving a small distance, the impacts 
of the change are unlikely to be significant to the individual, let 
alone the stock or population. However, if a sound source displaces 
marine mammals from an important feeding or breeding area for a 
prolonged period, impacts on individuals and populations could be 
significant. Given the many uncertainties in predicting the quantity 
and types of impacts of noise on marine mammals, it is common practice 
to estimate how many mammals would be present within a particular 
distance of industrial activities and exposed to a particular level of 
industrial sound. In most cases, this approach likely overestimates the 
numbers of marine mammals that would be affected in some biologically-
important manner.
    The sound criteria used to estimate how many marine mammals might 
be disturbed to some biologically-important degree by a seismic program 
are based primarily on behavioral observations of a few species. 
Detailed studies have been done on humpback, gray, bowhead (Balaena 
mysticetus), and sperm whales, and on ringed seals (Pusa hispida). 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 SIO's application and Appendix A of NSF's EA, baleen whales 
exposed to strong noise pulses from airguns often react by deviating 
from their normal migration route and/or interrupting their feeding and 
moving away. In the cases of migrating gray and bowhead whales, the 
observed changes in behavior appeared to be of little or no biological 
consequence to the animals. They simply avoided the sound source by 
displacing their migration route to varying degrees, but within the 
natural boundaries of the migration corridors.
    Studies of gray, bowhead, and humpback whales have shown that 
seismic pulses with received levels of 160-170 dB re 1 [mu]Pa (rms) 
seem to cause obvious avoidance behavior in a substantial fraction of 
the animals exposed (Richardson et al., 1995). In many areas, seismic 
pulses from large arrays of airguns diminish to those levels at 
distances ranging from 4-15 km (2.5-9.3 mi) from the source. A 
substantial proportion of the baleen whales within those distances may 
show avoidance or other strong behavioral reactions to the airgun 
array. Subtle behavioral changes sometimes become evident at somewhat 
lower received levels, and studies, summarized in Appendix A(5) of 
SIO's EA, have shown that some species of baleen whales, notably 
bowhead and humpback whales, at times show strong avoidance at received 
levels lower than 160-170 dB re 1 [mu]Pa (rms).
    Responses of humpback whales to seismic surveys have been studied 
during migration, on summer feeding grounds, and on Angolan winter 
breeding grounds; there has also been discussion of effects on the 
Brazilian wintering grounds. McCauley et al. (1998, 2000a) studied the 
responses of humpback whales off Western Australia to a full-scale 
seismic survey with a 16-airgun, 2678-in\3\ array, and to a single 20-
in\3\ airgun with source level 227 dB re 1 [mu]Pa [middot] m (peak to 
peak). McCauley et al. (1998) documented that avoidance reactions began 
at 5-8 km (3-5 mi) from the array, and that those reactions kept most 
pods approximately 3-4 km (1.8-2.5 mi) from the operating seismic boat. 
McCauley et al. (2000a) noted localized displacement during migration 
of 4-5 km (2.5-3.1 mi) by traveling pods and 7-12 km (4.3-7.5 mi) by 
more sensitive resting pods of cow-calf pairs. Avoidance distances with 
respect to the single airgun were smaller but consistent with the 
results from the full array in terms of the received sound levels. The 
mean received level for initial avoidance of an approaching airgun was 
140 dB re 1 [mu]Pa (rms) for humpback pods containing females, and at 
the mean closest point of approach distance the received level was 143 
dB re 1 [mu]Pa (rms). The initial avoidance response generally occurred 
at distances of 5-8 km (3.1-4.9 mi) from the airgun array and 2 km (1.2 
mi) from the single airgun. However, some individual humpback whales, 
especially males, approached within distances of 100-400

[[Page 50768]]

m (328-1312 ft), where the maximum received level was 179 dB re 1 
[mu]Pa (rms).
    Humpback whales on their summer feeding grounds in southeast Alaska 
did not exhibit persistent avoidance when exposed to seismic pulses 
from a 1.64-L (100-in\3\) airgun (Malme et al., 1985). Malme et al. 
reported that some of the humpbacks seemed startled at received levels 
of 150-169 dB re 1 [mu]Pa and concluded that there was no clear 
evidence of avoidance, despite the possibility of subtle effects, at 
received levels up to 172 re 1 [mu]Pa on an approximate rms basis. It 
has been suggested that South Atlantic humpback whales wintering off 
Brazil may be displaced or even strand upon exposure to seismic surveys 
(Engel et al., 2004). The evidence for this was circumstantial and 
subject to alternative explanations (IAGC, 2004). Also, the evidence 
was not consistent with subsequent results from the same area of Brazil 
(Parente et al., 2006), or with direct studies of humpbacks exposed to 
seismic surveys in other areas and seasons. After allowance for data 
from subsequent years, there was ``no observable direct correlation'' 
between strandings and seismic surveys (IWC, 2007:236).
    There are no data on reactions of right whales to seismic surveys, 
but results from the closely-related bowhead whale show that their 
responsiveness can be quite variable depending on their activity 
(migrating versus feeding). Bowhead whales migrating west across the 
Alaskan Beaufort Sea in autumn, in particular, are unusually 
responsive, with substantial avoidance occurring out to distances of 
20-30 km from a medium-sized airgun source at received sound levels of 
around 120-130 dB re 1 [mu]Pa (rms) (Miller et al., 1999; Richardson et 
al., 1999). However, more recent research on bowhead whales (Miller et 
al., 2005; Harris et al., 2007) corroborates earlier evidence that, 
during the summer feeding season, bowheads are not as sensitive to 
seismic sources. Nonetheless, subtle but statistically significant 
changes in surfacing-respiration-dive cycles were evident upon 
statistical analysis (Richardson et al., 1986). In summer, bowheads 
typically begin to show avoidance reactions at received levels of about 
152-178 dB re 1 [mu]Pa (rms) (Richardson et al., 1986, 1995; Ljungblad 
et al., 1988; Miller et al., 2005).
    Reactions of migrating and feeding (but not wintering) gray whales 
to seismic surveys have been studied. Malme et al. (1986, 1988) studied 
the responses of feeding eastern Pacific gray whales to pulses from a 
single 100-in\3\ airgun off St. Lawrence Island in the northern Bering 
Sea. They estimated, based on small sample sizes, that 50 percent of 
feeding gray whales stopped feeding at an average received pressure 
level of 173 dB re 1 [mu]Pa on an (approximate) rms basis, and that 10 
percent of feeding whales interrupted feeding at received levels of 163 
dB re 1 [mu]Pa (rms). Those findings were generally consistent with the 
results of experiments conducted on larger numbers of gray whales that 
were migrating along the California coast (Malme et al., 1984; Malme 
and Miles, 1985), and western Pacific gray whales feeding off Sakhalin 
Island, Russia (Wursig et al., 1999; Gailey et al., 2007; Johnson et 
al., 2007; Yazvenko et al., 2007a, b), along with data on gray whales 
off British Columbia (Bain and Williams, 2006).
    Various species of Balaenoptera (blue, sei, fin, and minke whales) 
have occasionally been reported in areas ensonified by airgun pulses 
(Stone, 2003; MacLean and Haley, 2004; Stone and Tasker, 2006). 
Sightings by observers on seismic vessels off the United Kingdom from 
1997 to 2000 suggest that, during times of good sightability, sighting 
rates for mysticetes (mainly fin and sei whales) were similar when 
large arrays of airguns were shooting vs. silent (Stone, 2003; Stone 
and Tasker, 2006). However, these whales tended to exhibit localized 
avoidance, remaining significantly further (on average) from the airgun 
array during seismic operations compared with non-seismic periods 
(Stone and Tasker, 2006). In a study off Nova Scotia, Moulton and 
Miller (2005) found little difference in sighting rates (after 
accounting for water depth) and initial sighting distances of 
balaenopterid whales when airguns were operating versus silent. 
However, there were indications that these whales were more likely to 
be moving away when seen during airgun operations. Similarly, ship-
based monitoring studies of blue, fin, sei and minke whales offshore of 
Newfoundland (Orphan Basin and Laurentian Sub-basin) found no more than 
small differences in sighting rates and swim directions during seismic 
vs. non-seismic periods Moulton et al., 2005, 2006a,b).
    Data on short-term reactions by cetaceans to impulsive noises are 
not necessarily indicative of long-term or biologically significant 
effects. It is not known whether impulsive sounds affect reproductive 
rate or distribution and habitat use in subsequent days or years. 
However, gray whales have continued to migrate annually along the west 
coast of North America with substantial increases in the population 
over recent years, despite intermittent seismic exploration (and much 
ship traffic) in that area for decades (Appendix A in Malme et al., 
1984; Richardson et al., 1995; Angliss and Outlaw, 2008). The western 
Pacific gray whale population did not seem affected by a seismic survey 
in its feeding ground during a previous year (Johnson et al., 2007). 
Similarly, bowhead whales have continued to travel to the eastern 
Beaufort Sea each summer, and their numbers have increased notably, 
despite seismic exploration in their summer and autumn range for many 
years (Richardson et al., 1987; Angliss and Outlaw, 2008).

Toothed Whales

    Little systematic information is available about reactions of 
toothed whales to noise pulses. Few studies similar to the more 
extensive baleen whale/seismic pulse work summarized above and (in more 
detail) in Appendix A of SIO's application have been reported for 
toothed whales. However, there are recent systematic studies on sperm 
whales (Jochens et al., 2006; Miller et al., 2006), and there is an 
increasing amount of information about responses of various odontocetes 
to seismic surveys based on monitoring studies (e.g., Stone, 2003; 
Smultea et al., 2004; Moulton and Miller, 2005; Bain and Williams, 
2006; Holst et al., 2006; Stone and Tasker, 2006; Potter et al., 2007; 
Weir, 2008).
    Seismic operators and marine mammal observers on seismic vessels 
regularly see dolphins and other small toothed whales near operating 
airgun arrays, but in general there is a tendency for most delphinids 
to show some avoidance of operating seismic vessels (e.g., Goold, 
1996a,b,c; Calambokidis and Osmek, 1998; Stone, 2003; Moulton and 
Miller, 2005; Holst et al., 2006; Stone and Tasker, 2006; Weir, 2008). 
Some dolphins seem to be attracted to the seismic vessel and floats, 
and some ride the bow wave of the seismic vessel even when large arrays 
of airguns are firing (e.g., Moulton and Miller, 2005). Nonetheless, 
small toothed whales more often tend to head away, or to maintain a 
somewhat greater distance from the vessel, when a large array of 
airguns is operating than when it is silent (e.g., Stone and Tasker, 
2006; Weir, 2008). In most cases the avoidance radii for delphinids 
appear to be small, on the order of 1 km less, and some individuals 
show no apparent avoidance. The beluga (Delphinapterus leucas) is a 
species that (at least at times) shows long-distance avoidance of 
seismic

[[Page 50769]]

vessels. Aerial surveys conducted in the southeastern Beaufort Sea 
during summer found that sighting rates of beluga whales were 
significantly lower at distances 10-20 km (6.2-12.4 mi) compared with 
20-30 km (12.4-18.6 mi) from an operating airgun array, and observers 
on seismic boats in that area rarely see belugas (Miller et al., 2005; 
Harris et al., 2007).
    Captive bottlenose dolphins and beluga whales exhibited changes in 
behavior when exposed to strong pulsed sounds similar in duration to 
those typically used in seismic surveys (Finneran et al., 2000, 2002, 
2005). However, the animals tolerated high received levels of sound 
before exhibiting aversive behaviors.
    Results for porpoises depend on species. The limited available data 
suggest that harbor porpoises show stronger avoidance of seismic 
operations than do Dall's porpoises (Stone, 2003; MacLean and Koski, 
2005; Bain and Williams, 2006; Stone and Tasker, 2006). Dall's 
porpoises seem relatively tolerant of airgun operations (MacLean and 
Koski, 2005; Bain and Williams, 2006), although they too have been 
observed to avoid large arrays of operating airguns (Calambokidis and 
Osmek, 1998; Bain and Williams, 2006). This apparent difference in 
responsiveness of these two porpoise species is consistent with their 
relative responsiveness to boat traffic and some other acoustic sources 
(Richardson et al., 1995; Southall et al., 2007).
    Most studies of sperm whales exposed to airgun sounds indicate that 
the sperm whale shows considerable tolerance of airgun pulses (e.g., 
Stone, 2003; Moulton et al., 2005, 2006a; Stone and Tasker, 2006; Weir, 
2008). In most cases the whales do not show strong avoidance, and they 
continue to call (see Appendix A of NSF's EA for review). However, 
controlled exposure experiments in the Gulf of Mexico indicate that 
foraging behavior was altered upon exposure to airgun sound (Jochens et 
al., 2006).
    There are almost no specific data on the behavioral reactions of 
beaked whales to seismic surveys. However, northern bottlenose whales 
(Hyperoodon 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 (e.g., Wursig et al., 1998). They 
may also dive for an extended period when approached by a vessel (e.g., 
Kasuya, 1986). Thus, it is likely that beaked whales would also show 
strong avoidance of an approaching seismic vessel, although this has 
not been documented explicitly.
    There are increasing indications that some beaked whales tend to 
strand when naval exercises involving mid-frequency sonar operation are 
ongoing nearby (e.g., Simmonds and Lopez-Jurado, 1991; Frantzis, 1998; 
NOAA and USN, 2001; Jepson et al., 2003; Hildebrand, 2005; Barlow and 
Gisiner, 2006; see also the ``Strandings and Mortality'' subsection, 
later). These strandings are apparently at least in part a disturbance 
response, although auditory or other injuries or other physiological 
effects may also be a involved. Whether beaked whales would ever react 
similarly to seismic surveys is unknown (see ``Strandings and 
Mortality'', below). Seismic survey sounds are quite different from 
those of the sonar in operation during the above-cited incidents.
    Odontocete reactions to large arrays of airguns are variable and, 
at least for delphinids and Dall's porpoises, seem to be confined to a 
smaller radius than has been observed for the more responsive of the 
mysticetes, belugas, and harbor porpoises (refer to Appendix A in NSF's 
EA). NMFS has established a 160 dB re 1 [mu]Pa disturbance threshold. 
Animals exposed to received sound levels at or above this threshold 
(but below injurious threshold) shall be considered ``taken'' by 
behavioral harassment (Level B).

Pinnipeds

    Pinnipeds are not likely to show a strong avoidance reaction to the 
airgun array. Visual monitoring from seismic vessels has shown only 
slight (if any) avoidance of airguns by pinnipeds, and only slight (if 
any) changes in behavior (Appendix A in NSF's EA). In the Beaufort Sea, 
some ringed seals avoided an area of 100 m (328 ft) to (at most) a few 
hundred meters around seismic vessels, but many seals remained within 
100-200 m (328-656 ft) of the trackline as the operating airgun array 
passed by (e.g., Harris et al., 2001; Moulton and Lawson, 2002; Miller 
et al., 2005). Ringed seal sightings averaged somewhat farther away 
from the seismic vessel when the airguns were operating than when they 
were not, but the difference was small (Moulton and Lawson, 2002). 
Similarly, in Puget Sound, sighting distances for harbor seals and 
California sea lions tended to be larger when airguns were operating 
(Calambokidis and Osmek, 1998). Previous telemetry work suggests that 
avoidance and other behavioral reactions may be stronger than evident 
to date from visual studies (Thompson et al., 1998). 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. As 
for cetaceans, the 160 dB or above disturbance threshold, but below 
injurious levels (190 dB), is considered appropriate for pinnipeds.

Hearing Impairment and Other Physical Effects

    Temporary or permanent hearing impairment is a possibility when 
marine mammals are exposed to very strong sounds, and temporary 
threshold shift (TTS) has bee