`[Federal Register Volume 73, Number 168 (Thursday, August 28, 2008)]
[Notices]
[Pages 50760-50778]
From the Federal Register Online via the Government Publishing 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 [email protected]. Comments sent via 
e-mail, including all attachments, must not exceed a 10-megabyte file 
size.
    A copy of the application containing a list of the references used 
in this document may be obtained by writing to the address specified 
above, telephoning the contact listed below (see FOR FURTHER 
INFORMATION CONTACT), or visiting the Internet at: http://www.nmfs.noaa.gov/pr/permits/incidental.htm.
    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 been demonstrated and studied in certain 
captive odontocetes and pinnipeds exposed to strong sounds (reviewed in 
Southall et al., 2007). However, there has been no specific 
documentation of TTS let alone permanent hearing damage, i.e., 
permanent threshold shift (PTS), in free-ranging marine mammals exposed 
to sequences of airgun pulses during realistic field conditions. 
Current NMFS policy regarding exposure of marine mammals to high-level 
sounds is that cetaceans and pinnipeds should not be exposed to 
impulsive sounds with received levels of 180 and 190 dB re 1 
[mu]Parms or above, respectively, are considered to have 
been taken incidentally taken by Level A harassment. (NMFS, 2000). 
These levels are precautionary and were used in establishing the 
exclusion (i.e., shut-down) zones planned for the proposed seismic 
survey.
    Several aspects of the planned monitoring and mitigation measures 
for this project are designed to detect marine mammals occurring near 
the airgun array, and 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 and sea turtles are 
likely to show some avoidance or the area with high received levels of 
airgun sound. 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 might also occur in marine mammals 
exposed to strong underwater pulsed sound. Possible types of non-
auditory physiological effects or injuries that might (in theory) occur 
in mammals close to a strong sound source include stress, neurological 
effects, bubble formation, and other types of organ or tissue damage. 
It is possible that some

[[Page 50770]]

marine mammal species (i.e., beaked whales) may be especially 
susceptible to injury and/or stranding when exposed to strong pulsed 
sounds. However, as discussed below, there is no definitive evidence 
that any of these effects occur even for marine mammals in close 
proximity to large arrays of airguns. It is unlikely that any effects 
of these types would occur during the proposed project given the brief 
duration of exposure of any given mammal, the deep water in the survey 
area, and the planned monitoring and mitigation measures (see below). 
The following subsections discuss in somewhat more detail the 
possibilities of TTS, PTS, and non-auditory physical effects.

Temporary Threshold Shift (TTS)

    TTS is the mildest form of hearing impairment that can occur during 
exposure to a strong sound (Kryter, 1985). While experiencing TTS, the 
hearing threshold rises and a sound must be stronger in order to be 
heard. At least in terrestrial mammals, TTS can last from minutes or 
hours to (in cases of strong TTS) days. For sound exposures at or 
somewhat above the TTS threshold, hearing sensitivity in both 
terrestrial and marine mammals recovers rapidly after exposure to the 
noise ends. Few data on sound levels and durations necessary to elicit 
mild TTS have been obtained for marine mammals, and none of the 
published data concern TTS elicited by exposure to multiple pulses of 
sound. Available data on TTS in marine mammals are summarized in 
Southall et al. (2007).
    For toothed whales exposed to single short pulses, the TTS 
threshold appears to be, to a first approximation, a function of the 
energy content of the pulse (Finneran et al., 2002, 2005). Sound 
exposure level (SEL), which takes into account the duration of the 
sound, is the metric used to measure energy and uses the units dB re 1 
[mu]Pa\2\ [middot] s, as opposed to sound pressure level (SPL), which 
is the pressure metric used in the rest of this document (units--dB re 
1 [mu]Pa). Given the available data, the received energy level of a 
single seismic pulse (with no frequency weighting) might need to be 
approximately 186 dB re 1 [mu]Pa2 [middot] s, (i.e., 186 dB SEL or 
approximately 196-201 dB re 1 [mu]Parms) in order to produce 
brief, mild TTS. Exposure to several strong seismic pulses that each 
have received levels near 190 dB re 1 [mu]Parms might result 
in cumulative exposure of approximately 186 dB SEL and thus slight TTS 
in a small odontocete, assuming the TTS threshold is (to a first 
approximation) a function of the total received pulse energy. The 
distances from the Melville's single airgun at which the received 
energy level (per pulse, flat-weighted) would be expected to be 190 dB 
re 1 [mu]Parms or above, are shown in Table 2. Levels 190 dB 
re 1 [mu]Parms or above are expected to be restricted to 
radii no more than 12m (39 ft) (Table 2) from the airgun at full 
chamber size (45 in\3\). Again, this is a conservative safety zone 
since the applicant has indicated the airgun will likely be operated at 
25-35 in\3\. For an odontocete closer to the surface, the maximum 
radius with 190 dB re 1 [mu]Parms or above, would be 
smaller.
    The above TTS information for odontocetes is derived from studies 
on the bottlenose dolphin and beluga. There is no published TTS 
information for other types of cetaceans. However, preliminary evidence 
from a harbor porpoise exposed to airgun sound suggests that its TTS 
threshold may have been lower (Lucke et al., 2007).
    For baleen whales, there are no data, direct or indirect, on levels 
or properties of sound that are required to induce TTS. The frequencies 
to which baleen whales are most sensitive are assumed to be lower than 
those to which odontocetes are most sensitive, and natural background 
noise levels at those low frequencies tend to be higher. As a result, 
auditory thresholds of baleen whales within their frequency band of 
best hearing are believed to be higher (less sensitive) than are those 
of odontocetes at their best frequencies (Clark and Ellison, 2004). 
From this, it is suspected that received levels causing TTS onset may 
also be higher in baleen whales (Southall et al., 2007). In any event, 
no cases of TTS are expected given three considerations: (1) The low 
abundance of baleen whales in most parts of the planned study area; (2) 
the strong likelihood that baleen whales would avoid the approaching 
airgun (or vessel) before being exposed to levels high enough for TTS 
to occur; and (3) the mitigation measures that are planned.
    In pinnipeds, TTS thresholds associated with exposure to brief 
pulses (single or multiple) of underwater sound have not been measured. 
Initial evidence from more prolonged (non-pulse) exposures suggested 
that some pinnipeds (harbor seals in particular) incur TTS at somewhat 
lower received levels than do small odontocetes exposed for similar 
durations (Kastak et al., 1999, 2005; Ketten et al., 2001). The 
pinniped TTS threshold for pulsed sounds has been indirectly estimated 
as being a SEL of approximately 171 dB re 1 [mu]Pa\2\ [middot] s, 
(Southall et al., 2007), which would be equivalent to a single pulse 
with received level of approximately 181-186 dB re 1 
[mu]Parms, or a series of pulses for which the highest rms 
values are a few dB lower.

Permanent Threshold Shift (PTS)

    When PTS occurs, there is physical damage to the sound receptors in 
the ear. In severe cases, there can be total or partial deafness, while 
in other cases, the animal has an impaired ability to hear sounds in 
specific frequency ranges (Kryter, 1985). There is no specific evidence 
that exposure to pulses of airgun sound can cause PTS in any marine 
mammal, even with large arrays of airguns. However, given the 
possibility that mammals close to an airgun array might incur at least 
mild TTS, there has been further speculation about the possibility that 
some individuals occurring very close to airguns might incur PTS 
(Richardson et al., 1995, p. 372ff). Single or occasional occurrences 
of mild TTS are not indicative of permanent auditory damage. 
Relationships between TTS and PTS thresholds have not been studied in 
marine mammals, but are assumed to be similar to those in humans and 
other terrestrial mammals. PTS might occur at a received sound level at 
least several decibels above that inducing mild TTS if the animal were 
exposed to strong sound pulses with rapid rise time--see Appendix A of 
NSF's EA. Based on data from terrestrial mammals, a precautionary 
assumption is that the PTS threshold for impulse sounds (such as airgun 
pulses as received close to the source) is at least 6 dB higher than 
the TTS threshold on a peak-pressure basis, and probably greater than 6 
dB (Southall et al., 2007). On an SEL basis, Southall et al. (2007:441-
4) estimated that received levels would need to exceed the TTS 
threshold by at least 15 dB for there to be risk of PTS. Thus, for 
cetaceans, they estimate that the PTS threshold might be an mammal-
weighted (M-weighted) SEL (for the sequence of received pulses) of 
approximately 198 dB re 1 [mu]Pa\2\ [middot] s, (15 dB higher than the 
TTS threshold for an impulse), where the SEL value is accumulated over 
the sequence of pulses. Additional assumptions had to be made to derive 
a corresponding estimate for pinnipeds, as the only available data on 
TTS-thresholds in pinnipeds pertain to non-impulse sound. Southall et 
al. (2007) estimate that the PTS threshold could be a cumulative 
Mpw-weighted SEL of approximately 186 dB re 1 [mu]Pa\2\ 
[middot] s, in the harbor seal exposed to impulse sound. The PTS 
threshold for the California sea lion and northern elephant seal, the 
PTS threshold would

[[Page 50771]]

probably be higher, given the higher TTS thresholds in those species.
    Southall et al. (2007) also note that, regardless of the SEL, there 
is concern about the possibility of PTS if a cetacean or pinniped 
received one or more pulses with peak pressure exceeding 230 or 218 dB 
re 1[mu]Pa (peak), respectively. A peak pressure of 230 dB re 1[mu]Pa 
(3.2 bar [middot] m, 0-peak) would only be found within a few meters of 
the largest (360 in\3\) airgun in the planned airgun array (Caldwell 
and Dragoset, 2000). A peak pressure of 218 dB re 1 [mu]Pa could be 
received somewhat farther away; to estimate that specific distance, one 
would need to apply a model that accurately calculates peak pressures 
in the nearfield around an array of airguns.
    Given the higher level of sound necessary to cause PTS as compared 
with TTS, it is considerably less likely that PTS would occur. Baleen 
whales generally avoid the immediate area around operating seismic 
vessels, as do some other marine mammals and sea turtles. The planned 
monitoring and mitigation measures, including visual monitoring, PAM, 
power downs, and shut downs of the airguns when mammals are seen within 
or approaching the exclusion zones, will further reduce the probability 
of exposure of marine mammals to sounds strong enough to induce PTS.

Non-Auditory Physiological Effects

    Non-auditory physiological effects or injuries that theoretically 
might occur in marine mammals exposed to strong underwater sound 
include stress, neurological effects, bubble formation, resonance, and 
other types of organ or tissue damage (Cox et al., 2006; Southall et 
al., 2007). Studies examining such effects are limited. However, 
resonance (Gentry, 2002) and direct noise-induced bubble formation 
(Crum et al., 2005) are not expected in the case of an impulsive source 
like an airgun array. If seismic surveys disrupt diving patterns of 
deep-diving species, this might perhaps result in bubble formation and 
a form of the bends, as speculated to occur in beaked whales exposed to 
sonar. However, there is no specific evidence of this upon exposure to 
airgun pulses.
    In general, very little is known about the potential for seismic 
survey sounds (or other types of strong underwater sounds) to cause 
non-auditory physical effects in marine mammals. Such effects, if they 
occur at all, would presumably be limited to short distances and to 
activities that extend over a prolonged period. The available data do 
not allow identification of a specific exposure level above which non-
auditory effects can be expected (Southall et al., 2007), or any 
meaningful quantitative predictions of the numbers (if any) of marine 
mammals that might be affected in those ways. Marine mammals that show 
behavioral avoidance of seismic vessels, including most baleen whales, 
some odontocetes, and some pinnipeds, are especially unlikely to incur 
non-auditory physical effects. Also, the planned mitigation measures, 
including shut downs of the airguns, will reduce any such effects that 
might otherwise occur.

Strandings and Mortality

    Marine mammals close to underwater detonations of high explosives 
can be killed or severely injured, and the auditory organs are 
especially susceptible to injury (Ketten et al., 1993; Ketten, 1995). 
However, explosives are no longer used for marine seismic research or 
commercial seismic surveys, and have been replaced entirely by airguns 
or related non-explosive pulse generators. Airgun pulses are less 
energetic and have slower rise times, and there is no specific evidence 
that they can cause serious injury, death, or stranding even in the 
case of large airgun arrays. However, the association of mass 
strandings of beaked whales with naval exercises and, in one case, an 
L-DEO seismic survey (Malakoff, 2002; Cox et al., 2006), has raised the 
possibility that beaked whales exposed to strong pulsed sounds may be 
especially susceptible to injury and/or behavioral reactions that can 
lead to stranding (e.g., Hildebrand, 2005; Southall et al., 2007).
    Specific sound-related processes that lead to strandings and 
mortality are not well documented, but may include: (1) Swimming in 
avoidance of a sound into shallow water; (2) a change in behavior (such 
as a change in diving behavior) that might contribute to tissue damage, 
gas bubble formation, hypoxia, cardiac arrhythmia, hypertensive 
hemorrhage or other forms of trauma; (3) a physiological change such as 
a vestibular response leading to a behavioral change or stress-induced 
hemorrhagic diathesis, leading in turn to tissue damage; and (4) tissue 
damage directly from sound exposure, such as through acoustically 
mediated bubble formation and growth or acoustic resonance of tissues. 
There are increasing indications that gas-bubble disease (analogous to 
the bends), induced in supersaturated tissue by a behavioral response 
to acoustic exposure, could be a pathologic mechanism for the 
strandings and mortality of some deep-diving cetaceans exposed to 
sonar. However, the evidence for this remains circumstantial and 
associated with exposure to naval mid-frequency sonar, not seismic 
surveys (Cox et al., 2006; Southall et al., 2007).
    Seismic pulses and mid-frequency sonar signals are quite different, 
and some mechanisms by which sonar sounds have been hypothesized to 
affect beaked whales are unlikely to apply to airgun pulses. Sounds 
produced by airgun arrays are broadband impulses with most of the 
energy below 1 kHz. Typical military mid-frequency sonars emit non-
impulse sounds at frequencies of 2-10 kHz, generally with a relatively 
narrow bandwidth at any one time. A further difference between seismic 
surveys and naval exercises is that naval exercises can involve sound 
sources on more than one vessel. Thus, it is not appropriate to assume 
that there is a direct connection between the effects of military sonar 
and seismic surveys on marine mammals. However, evidence that sonar 
signals can, in special circumstances, lead (at least indirectly) to 
physical damage and mortality (e.g., Balcomb and Claridge, 2001; NOAA 
and USN, 2001; Jepson et al., 2003; Fernandez et al., 2004, 2005; 
Hildebrand, 2005; Cox et al., 2006) suggests that caution is warranted 
when dealing with exposure of marine mammals to any high-intensity 
pulsed sound.
    There is no conclusive evidence of cetacean strandings or deaths at 
sea as a result of exposure to seismic surveys, but a few cases of 
strandings in the general area where a seismic survey was ongoing have 
led to speculation concerning a possible link between seismic surveys 
and strandings. Suggestions that there was a link between seismic 
surveys and strandings of humpback whales in Brazil (Engel et al., 
2004) were not well founded (IAGC, 2004; IWC, 2007). In September 2002, 
there was a stranding of two Cuvier's beaked whales (Ziphius 
cavirostris ) in the Gulf of California, Mexico, when the L-DEO vessel 
R/V Maurice Ewing was operating a 20-airgun, 8490-in\3\ airgun array in 
the general area. The link between the stranding and the seismic 
surveys was inconclusive and not based on any physical evidence 
(Hogarth, 2002; Yoder, 2002). Nonetheless, the Gulf of California 
incident plus the beaked whale strandings near naval exercises 
involving use of mid-frequency sonar suggests a need for caution in 
conducting seismic surveys in areas occupied by beaked whales until 
more is known about effects of seismic surveys on those species 
(Hildebrand, 2005). No injuries of beaked whales are anticipated during 
the proposed study because of: (1) The

[[Page 50772]]

high likelihood that any beaked whales nearby would avoid the 
approaching vessel before being exposed to high sound levels; (2) the 
proposed monitoring and mitigation measures; (3) the use of a single, 
low-energy airgun; and (4) differences between the sound sources 
operated by SIO and those involved in the naval exercises associated 
with strandings.

Potential Effects of Other Acoustic Devices

Multibeam Echosounder (MBES) Signals

    The Simrad EM120 12-kHz MBES will be operated from the source 
vessel at some times during the planned study. Sounds from the MBES are 
very short pulses, occurring for 2-15 ms once every 5-20 s, depending 
on water depth. Most of the energy in the sound pulses emitted by this 
MBES is at frequencies near 12 kHz, and the maximum source level is 242 
dB re 1 [mu]Parms. The beam is very narrow (1 degree) in 
fore-aft extent and wide (150 degrees) in the cross-track extent. Each 
ping consists of nine successive fan-shaped transmissions (segments) at 
different cross-track angles. Any given mammal at depth near the 
trackline would be in the main beam for only one or two of the nine 
segments. Also, marine mammals that encounter the Simrad EM120 are 
unlikely to be subjected to repeated pulses because of the narrow fore-
aft width of the beam and will receive only limited amounts of pulse 
energy because of the short pulses. Animals close to the ship (where 
the beam is narrowest) are especially unlikely to be ensonified for 
more than one 2-15 ms pulse (or two pulses if in the overlap area). 
Similarly, Kremser et al. (2005) noted that the probability of a 
cetacean swimming through the area of exposure when an MBES emits a 
pulse is small. The animal would have to pass the transducer at close 
range and be swimming at speeds similar to the vessel in order to 
receive the multiple pulses that might result in sufficient exposure to 
cause TTS.
    Navy sonars that have been linked to avoidance reactions and 
stranding of cetaceans (1) generally have a longer pulse duration than 
the Simrad EM120, and (2) are often directed close to omnidirectionally 
versus more downward for the Simrad EM120. The area of possible 
influence of the MBES is much smaller--a narrow band below the source 
vessel. The duration of exposure for a given marine mammal can be much 
longer for naval sonar. During SIO's operations, the individual pulses 
will be very short, and a given mammal would not receive many of the 
downward-directed pulses as the vessel passes by. Possible effects of 
an MBES on marine mammals are outlined below.

Masking

    Marine mammal communications will not be masked appreciably by the 
MBES signals given the low duty cycle of the echosounder and the brief 
period when an individual mammal is likely to be within its beam. 
Furthermore, in the case of baleen whales, the MBES signals (12 kHz) do 
not overlap with the predominant frequencies in the calls, which would 
avoid any significant masking.

Behavioral Responses

    Behavioral reactions of free-ranging marine mammals to sonar, 
echosounders, and other sound sources appear to vary by species and 
circumstance. Observed reactions have included silencing and dispersal 
by sperm whales (Watkins et al., 1985), increased vocalizations and no 
dispersal by pilot whales (Rendell and Gordon, 1999), and the 
previously-mentioned beachings by beaked whales. During exposure to a 
21-25 kHz sonar with a source level of 215 dB re 1[mu]Pa, gray whales 
reacted by orienting slightly away from the source and being deflected 
from their course by approximately 200 m (Frankel, 2005). When a 38-kHz 
echosounder and a 150-kHz acoustic Doppler current profiler were 
transmitting during studies in the Eastern Tropical Pacific, baleen 
whales showed no significant responses, while spotted and spinner 
dolphins were detected slightly more often and beaked whales less often 
during visual surveys (Gerrodette and Pettis, 2005).
    Captive bottlenose dolphins and a white whale exhibited changes in 
behavior when exposed to 1-s tonal signals at frequencies similar to 
those that will be emitted by the MBES used by SIO, and to shorter 
broadband pulsed signals. Behavioral changes typically involved what 
appeared to be deliberate attempts to avoid the sound exposure 
(Schlundt et al., 2000; Finneran et al., 2002; Finneran and Schlundt 
2004). The relevance of those data to free-ranging odontocetes is 
uncertain, and in any case, the test sounds were quite different in 
duration as compared with those from an MBES.
    Very few data are available on the reactions of pinnipeds to sonar 
sounds at frequencies similar to those used during seismic operations. 
Hastie and Janik (2007) conducted a series of behavioral response tests 
on two captive gray seals to determine their reactions to underwater 
operation of a 375-kHz multibeam imaging sonar that included 
significant signal components down to 6 kHz. Results indicated that the 
two seals reacted to the sonar signal by significantly increasing their 
dive durations. Because of the likely brevity of exposure to the MBES 
sounds, pinniped reactions are expected to be limited to startle or 
otherwise brief responses of no lasting consequence to the animals.

Hearing Impairments and Other Physical Effects

    Given recent stranding events that have been associated with the 
operation of naval sonar, there is concern that mid-frequency sonar 
sounds can cause serious impacts to marine mammals (see above). 
However, the MBES proposed for use by SIO is quite different than sonar 
used for navy operations. Pulse duration of the MBES is very short 
relative to the naval sonar. Also, at any given location, an individual 
marine mammal would be in the beam of the MBES for much less time given 
the generally downward orientation of the beam and its narrow fore-aft 
beamwidth; navy sonars often use near-horizontally-directed sound. 
Those factors would all reduce the sound energy received from the MBES 
rather drastically relative to that from the sonar used by the navy.
    Given the maximum source level of 242 dB re 1 [mu]Parms 
(see Sec.  I), the received level for an animal within the MBES beam 
100 m below the ship would be approximately 202 dB re 1 
[mu]Parms, assuming 40 dB of spreading loss over 100 m 
(circular spreading). Given the narrow beam, only one pulse is likely 
to be received by a given animal as the ship passes overhead. The 
received energy level from a single pulse of duration 15 ms would be 
about 184 dB re 1 [mu]Pa\2\ [middot] s, i.e., 202 dB + 10 log (0.015 
s). That is below the TTS threshold for a cetacean receiving a single 
non-impulse sound (195 dB re 1 [mu]Pa\2\ [middot] s) and even further 
below the anticipated PTS threshold (215 dB re 1 [mu]Pa\2\ [middot] s) 
(Southall et al., 2007). In contrast, an animal that was only 10 m 
below the MBES when a ping is emitted would be expected to receive a 
level ~20 dB higher, i.e., 204 dB re 1 [mu]Pa\2\ [middot] s in the case 
of the EM120. That animal might incur some TTS (which would be fully 
recoverable), but the exposure would still be below the anticipated PTS 
threshold for cetaceans. As noted by Burkhardt et al. (2007, 2008), 
cetaceans are very unlikely to incur PTS from operation of scientific 
sonars on a ship that is underway.
    In the harbor seal, the TTS threshold for non-impulse sounds is 
about 183 dB re 1 [mu]Pa\2\ [middot] s, as compared with ~195 dB re 1 
[mu]Pa\2\ [middot] s in odontocetes (Kastak et

[[Page 50773]]

al., 2005; Southall et al., 2007). TTS onset occurs at higher received 
energy levels in the California sea lion and northern elephant seal 
than in the harbor seal. A harbor seal as much as 100 m below the 
Melville could receive a single MBES pulse with received energy level 
of >=184 dB re 1 [mu]Pa\2\ [middot] s (as calculated in the toothed 
whale subsection above) and thus could incur slight TTS. Species of 
pinnipeds with higher TTS thresholds would not incur TTS unless they 
were closer to the transducers when a sonar ping was emitted. However, 
the SEL threshold for PTS in pinnipeds (203 dB re 1 [mu]Pa\2\ [middot] 
s) might be exceeded for a ping received within a few meters of the 
transducers, although the risk of PTS is higher for certain species 
(e.g., harbor seal). Given the intermittent nature of the signals and 
the narrow MBES beam, only a small fraction of the pinnipeds below (and 
close to) the ship would receive a pulse as the ship passed overhead.

Sub-Bottom Profiler Signals

    An SBP may be operated from the source vessel at times during the 
planned study. Sounds from the sub-bottom profiler are very short 
pulses, occurring for 1-4 ms once every second. Most of the energy in 
the sound pulses emitted by the SBP is at 3.5 kHz, and the beam is 
directed downward in a narrow beam with a spacing of up to 15 degrees 
and a fan width up to 30 degrees. The Edgetech 512i Chirp and Knudsen 
320BR sub-bottom profilers on the Melville have a maximum source level 
of 198 and 211 dB re 1 [mu]Pa [middot] m, respectively. Kremser et al. 
(2005) noted that the probability of a cetacean swimming through the 
area of exposure when a bottom profiler emits a pulse is small--even 
for an SBP more powerful than that on the Melville if the animal was in 
the area, it would have to pass the transducer at close range in order 
to be subjected to sound levels that could cause TTS.

Masking

    Marine mammal communications will not be masked appreciably by the 
sub-bottom profiler signals given their directionality and the brief 
period when an individual mammal is likely to be within its beam. 
Furthermore, in the case of most baleen whales, the SBP signals do not 
overlap with the predominant frequencies in the calls, which would 
avoid significant masking.

Behavioral Reactions

    Marine mammal behavioral reactions to other pulsed sound sources 
are discussed above, and responses to the SBP are likely to be similar 
to those for other pulsed sources if received at the same levels. 
However, the pulsed signals from the SBP are considerably weaker than 
those from the MBES. Therefore, behavioral responses would not be 
expected unless marine mammals were to approach very close to the 
source.

Hearing Impairment and Other Physical Effects

    It is unlikely that the SBP produces pulse levels strong enough to 
cause hearing impairment or other physical injuries even in an animal 
that is (briefly) in a position near the source. The SBP is usually 
operated simultaneously with other higher-power acoustic sources. Many 
marine mammals will move away in response to the approaching higher-
power sources or the vessel itself before the mammals would be close 
enough for there to be any possibility of effects from the less intense 
sounds from the SBP. In the case of mammals that do not avoid the 
approaching vessel and its various sound sources, mitigation measures 
that would be applied to minimize effects of other sources would 
further reduce or eliminate any minor effects of the SBP.

Estimated Take by Incidental Harassment

    All anticipated takes would be ``takes by harassment'', involving 
temporary changes in behavior. The proposed mitigation measures are 
expected to minimize the possibility of injurious takes. (However, as 
noted earlier, there is no specific information demonstrating that 
injurious ``takes'' would occur even in the absence of the planned 
mitigation measures.) The sections below describe methods to estimate 
``take by harassment'', and present estimates of the numbers of marine 
mammals that might be affected during the proposed SBC seismic program. 
The estimates of ``take by harassment'' are based on consideration of 
the number of marine mammals that might be disturbed appreciably by 
approximately 600 km of trackline, including turns, using the airgun 
and approximately 500 km of trackline using the sparker or boomer. The 
main sources of distributional and numerical data used in deriving the 
estimates are described below.
    The anticipated radii of influence of the MBES and the SBP are less 
than those for the airgun array. It is assumed that, during 
simultaneous operations of the airgun array and echosounders, marine 
mammals close enough to be affected by the echosounders would already 
be affected by the airguns. However, whether or not the airguns are 
operating simultaneously with the echosounders, marine mammals are 
expected to exhibit no more than short-term and inconsequential 
responses to the echosounders given their characteristics (e.g., narrow 
downward-directed beam) and other considerations described above. NMFS 
believes that such reactions are not considered to constitute 
``taking.'' Therefore, no additional allowance is included for animals 
that might be affected by sound sources other than airguns, boomer, and 
sparker.
    Extensive systematic aircraft- and ship-based surveys have been 
conducted for marine mammals off the U.S. west coast; the most 
comprehensive and recent density data available for cetacean species in 
shelf, slope, and offshore waters of California are from the 1991, 
1993, 1996, 2001, and 2005 NMFS/SWFSC shipboard surveys as synthesized 
by Barlow and Forney (2007). The surveys were conducted up to 
approximately 550 km offshore from June or July to November or 
December. Densities are available for all of California in each of the 
five years, and for southern California (south of the latitude of Point 
Conception) for all years combined (Barlow and Forney, 2007), but not 
for southern California in each year except 2005 (Forney, 2007). 
Another set of surveys that included southern California was conducted 
by NMFS in the ETP during summer and fall 1986-1996, as summarized by 
Ferguson and Barlow (2001). Densities were calculated for 5[deg] x 
5[deg] blocks; the partial block that includes the waters off southern 
California (Block 58) has its northern boundary at 35[deg]N, just north 
of Point Conception. It extends off the coast as a wedge with a maximum 
distance of ~375 km offshore, and included 2925 km of survey effort in 
Beaufort sea states 0-5 and 600 km of survey effort in Beaufort sea 
states 0-2. We decided to use those density estimates because a smaller 
proportion of the waters surveyed were offshore. For two species 
expected to be common in the SBC but for which there were no sightings 
in Ferguson and Barlow (2001)--humpback whales and Dall's porpoise--the 
applicant estimated take using the 2005 densities for southern 
California in Forney (2007).
    Systematic at-sea survey data for pinnipeds are more limited. The 
only densities to our knowledge are for California sea lions, and are 
based on ~31,000 km of aerial surveys of the SCB during 1975-1978, as 
summarized by Bonnell and Ford (1987). There are no density data, to 
our knowledge, for sea otters in the study area.

[[Page 50774]]

    Oceanographic conditions, including occasional El Nino and La Nina 
events, influence the distribution and numbers of marine mammals 
present in the NEPO, including California, resulting in considerable 
year-to-year variation in the distribution and abundance of many marine 
mammal species (Forney and Barlow 1998; Buchanan et al. 2001; Escorza-
Trevino 2002; Ferrero et al. 2002; Philbrick et al. 2003; Becker 2007). 
Thus, for some species the densities derived from recent surveys may 
not be representative of the densities that will be encountered during 
the proposed seismic survey.
    The estimated numbers of individuals potentially exposed are 
presented below based on the 160-dB re 1 [mu]Parms threshold 
for all cetaceans and pinnipeds. It is assumed that marine mammals 
exposed to seismic sounds this strong might change their behavior 
sufficiently to be considered ``taken by harassment''. It should be 
noted that the following estimates of exposures to various sound levels 
assume that the surveys will be fully completed; in fact, the planned 
number of line-kilometers has been increased by 25% to accommodate 
lines that may need to be repeated, equipment testing, etc. As is 
typical during ship surveys, inclement weather and equipment 
malfunctions are likely to cause delays and may limit the number of 
useful line-kilometers of seismic operations that can be undertaken. 
Furthermore, any marine mammal sightings within or near the designated 
exclusion zone will result in the shutdown of seismic operations as a 
mitigation measure. Thus, the following estimates of the numbers of 
marine mammals potentially expose to 160 dB re 1 [mu]Parms 
sounds are precautionary, and probably overestimate the actual numbers 
of marine mammals that might be involved. These estimates assume that 
there will be no weather, equipment, or mitigation delays, which is 
highly unlikely.
    The number of different individuals that could be exposed to GI-gun 
or boomer sounds with received levels 160 dB re 1 [mu]Parms 
on one or more occasions can be estimated by considering the total 
marine area that would be within the 160-dB radius around the operating 
seismic sources on at least one occasion along with the expected 
density of animals in the area. The proposed seismic lines run parallel 
to each other in close proximity; thus, an individual mammal may be 
exposed numerous times during the survey. The number of possible 
exposures to GI-gun and boomer sounds with received levels >=160 dB re 
1 [mu]Parms (including repeated exposures of the same 
individuals) can be estimated by considering the total marine area that 
would be within the 160-dB radius around the operating seismic sources, 
including areas of overlap. However, it is unlikely that a particular 
animal would stay in the area during the entire survey. The number of 
potential exposures and the number of different individuals potentially 
exposed to >=160 dB re 1 [mu]Parms were calculated by 
multiplying: (1) The expected species density, either ``mean'' (i.e., 
best estimate) or ``maximum'', times; (2) the anticipated area to be 
ensonified to that level during seismic operations including overlap 
(exposures), or; (3) the anticipated area to be ensonified to that 
level during seismic operations excluding overlap (individuals).
    The area expected to be ensonified was determined by entering the 
planned survey lines into a MapInfo Geographic Information System 
(GIS), using the GIS to identify the relevant areas by ``drawing'' the 
applicable 160-dB buffer around each seismic line, and then calculating 
the total area within the buffers. Areas where overlap occurred 
(because of closely-spaced lines) were included when estimating the 
number of exposures, whereas the areas of overlap were included only 
once when estimating the number of individuals exposed.
    Applying the approach described above, approximately 289 km\2\ 
would be within the 160-dB isopleth on one or more occasions during the 
survey, whereas approximately 690 km\2\ is the area ensonified to >=160 
dB when overlap is included. Thus, it is possible that an average 
individual marine mammal could be exposed up to two or three times 
during the survey. Because this approach does not allow for turnover in 
the mammal populations in the study area during the course of the 
survey, the actual number of individuals exposed may be underestimated, 
although the conservative (i.e., probably overestimated) line-kilometer 
distances used to calculate the area may offset this. Also, the 
approach assumes that no cetaceans will move away or toward the 
trackline as the Melville approaches in response to increasing sound 
levels prior to the time the levels reach 160 dB.
    The best estimate of the number of individual marine mammals that 
could be exposed to seismic sounds with received levels >=160 dB re 1 
[mu]Parms (but below Level A harassment thresholds) during 
the survey is 508 (Table 4). These estimates were derived from the best 
density estimates calculated for these species in the area (see Table 4 
of SIO's application). However, SIO is requesting takes of marine 
mammals based on the maximum density estimates (see Table 4 in SIO's 
application) given that density data is not always precise, hence best 
and maximum estimates, and that these animals may be in the area. 
Requested number of marine mammals taken is listed in Table 4 below. In 
addition, the number of exposures those animals could be subjected to 
is also outlined. These numbers are based on trackline length, 
harassment isopleth distances, and density of animals. More information 
on how number of individuals and number of exposures were calculated 
can be found in SIO's application. Because the single 45 in\3\ airgun 
will likely be operated at a reduced chamber size but exposures are 
based on maximum chamber size, NMFS believes that the ``best'' estimate 
of exposures is the most appropriate number to use. The best estimate 
of the total number of exposures of marine mammals to seismic sounds 
with received levels >=160 dB re 1 [mu]Parms during the 
survey is 1212, including four blue whale exposures, and one Cuvier's 
beaked whale exposure. The short-beaked common dolphin is estimated to 
be exposed most frequently, with a best estimate of 942 exposures.
    Two of the six pinniped species listed in Table 4, the Guadalupe 
fur seal (Arctocephalus townsendi) and the Steller sea lion (Eumetopias 
jubatus), are rare in the SBC, and another two, the northern fur seal 
(Callorhinus ursinus) and northern elephant seal (Mirounga 
angustirostris), are not expected to occur there at the time of the 
proposed survey (November) because they are feeding offshore at that 
time. Densities are available for the California sea lion, the most 
abundant pinniped in the Channel Islands, but not for the harbor seal, 
which could be encountered during the survey. Therefore, allowances 
have been made in Table 4 for the exposure of a small number (20) of 
harbor seals to received sound levels >=160 dB re 1 
[mu]Parms.

Potential Effects on Marine Mammal Habitat

    The proposed seismic surveys will not result in any permanent 
impact on habitats used by marine mammals, or to the food sources they 
use. The main impact issue associated with the proposed activity will 
be temporarily elevated noise levels and the associated direct effects 
on marine mammals, as described above. The following sections briefly 
review effects of airguns on fish and invertebrates, and more details 
are

[[Page 50775]]

included in Appendices C and D, respectively, of NSF's EA, 
respectively.
    One reason for the adoption of airguns as the standard energy 
source for marine seismic surveys is that, unlike explosives, they have 
not been associated with large-scale fish kills. However, existing 
information on the impacts of seismic surveys on marine fish 
populations is very limited (see Appendix C of NSF's EA). There are 
three types of potential effects of exposure to seismic surveys: (1) 
Pathological, (2) physiological, and (3) behavioral. Pathological 
effects involve lethal and temporary or permanent sub-lethal injury. 
Physiological effects involve temporary and permanent primary and 
secondary stress responses, such as changes in levels of enzymes and 
proteins. Behavioral effects refer to temporary and (if they occur) 
permanent changes in exhibited behavior (e.g., startle and avoidance 
behavior). The three categories are interrelated in complex ways. For 
example, it is possible that certain physiological and behavioral 
changes potentially could lead to an ultimate pathological effect on 
individuals (i.e., mortality).
    The specific received sound levels at which permanent adverse 
effects to fish potentially could occur are little studied and largely 
unknown. Furthermore, the available information on the impacts of 
seismic surveys on marine fish is from studies of individuals or 
portions of a population; there have been no studies at the population 
scale. Thus, available information provides limited insight on possible 
real-world effects at the ocean or population scale. This makes drawing 
conclusions about impacts on fish problematic because ultimately, the 
most important aspect of potential impacts relates to how exposure to 
seismic survey sound affects marine fish populations and their 
viability, including their availability to fisheries.
    The following sections provide a general synopsis of available 
information on the effects of exposure to seismic and other 
anthropogenic sound as relevant to fish. The information comprises 
results from scientific studies of varying degrees of rigor plus some 
anecdotal information. Some of the data sources may have serious 
shortcomings in methods, analysis, interpretation, and reproducibility 
that must be considered when interpreting their results (see Hastings 
and Popper, 2005). Potential adverse effects of the program's sound 
sources on marine fish are then noted.
    Pathological Effects--Wardle et al. (2001) suggested that in water, 
acute injury and death of organisms exposed to seismic energy depends 
primarily on two features of the sound source: (1) The received peak 
pressure and (2) the time required for the pressure to rise and decay. 
Generally, as received pressure increases, the period for the pressure 
to rise and decay decreases, and the chance of acute pathological 
effects increases. According to Buchanan et al. (2004), for the types 
of seismic airguns and arrays involved with the proposed program, the 
pathological (mortality) zone for fish and invertebrates would be 
expected to be within a few meters of the seismic source. Numerous 
other studies provide examples of no fish mortality upon exposure to 
seismic sources (Falk and Lawrence, 1973; Holliday et al., 1987; La 
Bella et al., 1996; Santulli et al., 1999; McCauley et al., 2000a,b, 
2003; Bjarti, 2002; Hassel et al., 2003; Popper et al., 2005).
    The potential for pathological damage to hearing structures in fish 
depends on the energy level of the received sound and the physiology 
and hearing capability of the species in question (see Appendix C of 
NSF's EA). For a given sound to result in hearing loss, the sound must 
exceed, by some specific amount, the hearing threshold of the fish for 
that sound (Popper 2005). The consequences of temporary or permanent 
hearing loss in individual fish on a fish population is unknown; 
however, it likely depends on the number of individuals affected and 
whether critical behaviors involving sound (e.g., predator avoidance, 
prey capture, orientation and navigation, reproduction, etc.) are 
adversely affected.
    Little is known about the mechanisms and characteristics of damage 
to fish that may be inflicted by exposure to seismic survey sounds. Few 
data have been presented in the peer-reviewed scientific literature. As 
far as we know, there are only two valid papers with proper 
experimental methods, controls, and careful pathological investigation 
implicating sounds produced by actual seismic survey airguns with 
adverse anatomical effects. One such study indicated anatomical damage 
and the second indicated TTS in fish hearing. The anatomical case is 
McCauley et al. (2003), who found that exposure to airgun sound caused 
observable anatomical damage to the auditory maculae of ``pink 
snapper'' (Pagrus auratus). This damage in the ears had not been 
repaired in fish sacrificed and examined almost two months after 
exposure. On the other hand, Popper et al. (2005) documented only TTS 
(as determined by auditory brainstem response) in two of three fishes 
from the Mackenzie River Delta. This study found that broad whitefish 
(Coreogonus nasus) that received a sound exposure level of 177 dB re 1 
[mu]Pa\2\ [middot] s showed no hearing loss. During both studies, the 
repetitive exposure to sound was greater than would have occurred 
during a typical seismic survey. However, the substantial low-frequency 
energy produced by the airgun arrays [less than approximately 400 Hz in 
the study by McCauley et al. (2003) and less than approximately 200 Hz 
in Popper et al. (2005)] likely did not propagate to the fish because 
the water in the study areas was very shallow (approximately 9 m in the 
former case and <2 m in the latter). Water depth sets a lower limit on 
the lowest sound frequency that will propagate (the ``cutoff 
frequency'') at about one-quarter wavelength (Urick, 1983; Rogers and 
Cox, 1988). Except for these two studies, at least with airgun-
generated sound treatments, most contributions rely on rather 
subjective assays such as fish ``alarm'' or ``startle response'' or 
changes in catch rates by fishers. These observations are important in 
that they attempt to use the levels of exposures that are likely to be 
encountered by most free-ranging fish in actual survey areas. However, 
the associated sound stimuli are often poorly described, and the 
biological assays are varied (Hastings and Popper, 2005).
    Some studies have reported, some equivocally, that mortality of 
fish, fish eggs, or larvae can occur close to seismic sources 
(Kostyuchenko, 1973; Dalen and Knutsen, 1986; Booman et al., 1996; 
Dalen et al., 1996). Some of the reports claimed seismic effects from 
treatments quite different from actual seismic survey sounds or even 
reasonable surrogates. Saetre and Ona (1996) applied a ``worst-case 
scenario'' mathematical model to investigate the effects of seismic 
energy on fish eggs and larvae. They concluded that mortality rates 
caused by exposure to seismic surveys are so low, as compared to 
natural mortality rates, that the impact of seismic surveying on 
recruitment to a fish stock must be regarded as insignificant.
    Physiological Effects--Physiological effects refer to cellular and/
or biochemical responses of fish to acoustic stress. Such stress 
potentially could affect fish populations by increasing mortality or 
reducing reproductive success. Primary and secondary stress responses 
of fish after exposure to seismic survey sound appear to be temporary 
in all studies done to date (Sverdrup et al., 1994; McCauley et al., 
2000a, 2000b). The periods necessary for the biochemical changes to 
return to normal are variable, and depend on numerous aspects of the

[[Page 50776]]

biology of the species and of the sound stimulus (see Appendix C of 
NSF's EA).
    Summary of Physical (Pathological and Physiological) Effects--As 
indicated in the preceding general discussion, there is a relative lack 
of knowledge about the potential physical (pathological and 
physiological) effects of seismic energy on marine fish and 
invertebrates. Available data suggest that there may be physical 
impacts on egg, larval, juvenile, and adult stages at very close range. 
Considering typical source levels associated with commercial seismic 
arrays, close proximity to the source would result in exposure to very 
high energy levels. Whereas egg and larval stages are not able to 
escape such exposures, juveniles and adults most likely would avoid it. 
In the case of eggs and larvae, it is likely that the numbers adversely 
affected by such exposure would not be that different from those 
succumbing to natural mortality. Limited data regarding physiological 
impacts on fish and invertebrates indicate that these impacts are short 
term and are most apparent after exposure at close range.
    The SIO's proposed seismic survey is predicted to have negligible 
to low physical effects on the various life stages of fish and 
invertebrates for its short duration (approximately 25 days each in the 
Pacific Ocean and Caribbean Sea) and approximately 2,149-km of unique 
survey lines extent. Therefore, physical effects of the proposed 
program on fish and invertebrates would not be significant.
    Behavioral Effects--Behavioral effects include changes in the 
distribution, migration, mating, and catchability of fish populations. 
Studies investigating the possible effects of sound (including seismic 
survey sound) on fish behavior have been conducted on both uncaged and 
caged individuals (Chapman and Hawkins, 1969; Pearson et al., 1992; 
Santulli et al., 1999; Wardle et al., 2001; Hassel et al., 2003). 
Typically, in these studies fish exhibited a sharp ``startle'' response 
at the onset of a sound followed by habituation and a return to normal 
behavior after the sound ceased.
    There is general concern about potential adverse effects of seismic 
operations on fisheries, namely a potential reduction in the 
``catchability'' of fish involved in fisheries. Although reduced catch 
rates have been observed in some marine fisheries during seismic 
testing, in a number of cases the findings are confounded by other 
sources of disturbance (Dalen and Raknes, 1985; Dalen and Knutsen, 
1986; L[oslash]kkeborg, 1991; Skalski et al., 1992; Eng[aring]s et al., 
1996). In other airgun experiments, there was no change in catch per 
unit effort (CPUE) of fish when airgun pulses were emitted, 
particularly in the immediate vicinity of the seismic survey (Pickett 
et al., 1994; La Bella et al., 1996). For some species, reductions in 
catch may have resulted from a change in behavior of the fish, e.g., a 
change in vertical or horizontal distribution, as reported in Slotte et 
al., (2004).
    In general, any adverse effects on fish behavior or fisheries 
attributable to seismic testing may depend on the species in question 
and the nature of the fishery (season, duration, fishing method). They 
may also depend on the age of the fish, its motivational state, its 
size, and numerous other factors that are difficult, if not impossible, 
to quantify at this point, given such limited data on effects of 
airguns on fish, particularly under realistic at-sea conditions.
    For marine invertebrates, behavioral changes could potentially 
affect such aspects as reproductive success, distribution, 
susceptibility to predation, and catchability by fisheries. Studies of 
squid indicated startle responses (McCauley et al., 2000a,b). In other 
cases, no behavioral impacts were noted (e.g., crustaceans in Christian 
et al., 2003, 2004; DFO, 2004). There have been anecdotal reports of 
reduced catch rates of shrimp shortly after exposure to seismic 
surveys; however, other studies have not observed any significant 
changes in shrimp catch rate (Andriguetto-Filho et al., 2005). Parry 
and Gason (2006) reported no changes in rock lobster CPUE during or 
after seismic surveys off western Victoria, Australia, from 1978-2004. 
Any adverse effects on crustacean and cephalopod behavior or fisheries 
attributable to seismic survey sound depend on the species in question 
and the nature of the fishery (season, duration, fishing method). 
Additional information regarding the behavioral effects of seismic on 
invertebrates is contained in Appendix D in NSF's EA.
    Summary of Behavioral Effects--As is the case with pathological and 
physiological effects of seismic on fish and invertebrates, available 
information is relatively scant and often contradictory. There have 
been well-documented observations of fish and invertebrates exhibiting 
behaviors that appeared to be responses to exposure to seismic energy 
(i.e., startle response, change in swimming direction and speed, and 
change in vertical distribution), but the ultimate importance of those 
behaviors is unclear. Some studies indicate that such behavioral 
changes are very temporary, whereas others imply that fish might not 
resume pre-seismic behaviors or distributions for a number of days. 
There appears to be a great deal of inter- and intra-specific 
variability. In the case of finfish, three general types of behavioral 
responses have been identified: Startle, alarm, and avoidance. The type 
of behavioral reaction appears to depend on many factors, including the 
type of behavior being exhibited before exposure, and proximity and 
energy level of sound source.
    During the proposed study, only a small fraction of the available 
habitat would be ensonified at any given time, and fish species would 
return to their pre-disturbance behavior once the seismic activity 
ceased. The proposed seismic program is predicted to have negligible to 
low behavioral effects on the various life stages of the fish and 
invertebrates during its relatively short duration and extent.
    Because of the reasons noted above and the nature of the proposed 
activities, the proposed operations are not expected to have any 
habitat-related effects that could cause significant or long-term 
consequences for individual marine mammals or their populations or 
stocks. Similarly, any effects to food sources are expected to be 
negligible.

Proposed Monitoring

    SIO proposes to sponsor marine mammal monitoring during the present 
project, in order to implement the proposed mitigation measures that 
require real-time monitoring, and to satisfy the anticipated monitoring 
requirements of the Incidental Harassment Authorization. Vessel-based 
marine mammal visual observers (MMVOs) will be based on board the 
seismic source vessel, and they will watch for marine mammals and 
turtles near the vessel during seismic operations. MMVOs will also 
watch for marine mammals and turtles near the seismic vessel for at 
least 30 minutes prior to the start of seismic operations after an 
extended shutdown. When feasible, MMVOs will also make observations 
during daytime periods when the seismic system is not operating for 
comparison of animal abundance and behavior. Based on MMVO 
observations, the seismic source will be shut down when marine mammals 
are observed within or about to enter a designated exclusion zone (EZ). 
The EZ is a region in which a possibility exists of adverse effects on 
animal hearing or other physical effects.
    MMVOs will be appointed by the academic institution conducting the 
research cruise, with NMFS Office of Protected Resources concurrence. 
At least one MMVO will monitor the EZ

[[Page 50777]]

during seismic operations. MMVOs will normally work in shifts of 4-hour 
duration or less. The vessel crew will also be instructed to assist in 
detecting marine mammals and turtles.
    Standard equipment for marine mammal observers will be 7 x 50 
reticule binoculars and optical range finders. At night, night-vision 
equipment will be available, although seismic activity will be 
restricted to daylight hours. The observers will be in wireless 
communication with ship's officers on the bridge and scientists in the 
vessel's operations laboratory, so they can advise promptly of the need 
for avoidance maneuvers or seismic source shut down.

Proposed Mitigation During Operations

    Mitigation measures that will be adopted will include (1) Vessel 
speed or course alteration, provided that doing so will not compromise 
operational safety requirements, (2) GI-gun or boomer shut down within 
calculated exclusion zones, and (3) shut down at any range in the 
unlikely event that a North Pacific right whale or a concentration of 
sea otters is sighted. Two other standard mitigation measures--airgun 
array power down and airgun array ramp up--are not possible because 
only one, low-volume GI airgun, boomer, or sparker will be used for the 
surveys. In addition, avoidance of airgun operations over or near steep 
slopes or submarine canyons has become a standard mitigation measure, 
as these are places where beaked whales tend to concentrate. However, 
no such bathymetric features exist in the study area; therefore, this 
mitigation measure is not applicable to these surveys.

Speed or Course Alteration

    If a marine mammal or turtle is detected outside the EZ but is 
likely to enter it based on relative movement of the vessel and the 
animal, then if safety and scientific objectives allow, the vessel 
speed and/or course will be adjusted to minimize the likelihood of the 
animal entering the EZ. Major course and speed adjustments are often 
impractical when towing long seismic streamers and large source arrays, 
but are possible in this case because only one small source and a short 
(450-m) streamer will be used.

Shut-Down Requirements and Procedures

    If a marine mammal is detected outside the exclusion zones but is 
likely to enter the exclusion zone, and if the vessel's speed and/or 
course cannot be changed to avoid having the animal enter the exclusion 
zone, the seismic source will be shut down before the animal is within 
the exclusion zone. Likewise, if a mammal is already within the safety 
zone when first detected, the seismic source will be shut down 
immediately.
    Following a shut down, seismic activity will not resume until the 
marine mammal or turtle has cleared the exclusion zone. The animal will 
be considered to have cleared the exclusion zone if it is visually 
observed to have left the exclusion zone; has not been seen within the 
zone for 10 min in the case of small odontocetes and pinnipeds; or has 
not been seen within the zone for 15 min in the case of mysticetes and 
large odontocetes, including sperm, pygmy sperm, dwarf sperm, and 
beaked whales.
    In the unanticipated event that any cases of marine mammal injury 
or mortality are judged to result from these activities, SIO will cease 
operating seismic airgun operation and report the incident to the 
Office of Protected Resources, NMFS, and the Southwest Regional 
Administrator, NMFS, immediately.

Proposed Reporting

    MMVOs will record data to estimate the numbers of marine mammals 
and turtles exposed to various received sound levels and to document 
apparent disturbance reactions or lack thereof. Data will be used to 
estimate numbers of animals potentially ``taken'' by harassment (as 
defined in the MMPA). They will also provide information needed to 
order a shutdown of the seismic source when a marine mammal or sea 
turtles is within or near the EZ.
    When a sighting is made, the following information about the 
sighting will be recorded: Species, group size, and age/size/sex 
categories (if determinable); behavior when first sighted and after 
initial sighting; heading (if consistent), bearing, and distance from 
seismic vessel; sighting cue; apparent reaction to the seismic source 
or vessel (e.g., none, avoidance, approach, paralleling, etc.); and 
behavioral pace. In addition, time, location, heading, speed, activity 
of the vessel, sea state, visibility, and sun glare will also be 
recorded. This data (time, location, etc.) will also be recorded at the 
start and end of each observation watch, and during a watch whenever 
there is a change in one or more of the variables.
    All observations, as well as information regarding seismic source 
shutdown, will be recorded in a standardized format. Data accuracy will 
be verified by the MMVOs at sea, and preliminary reports will be 
prepared during the field program and summaries forwarded to the 
operating institution's shore facility and to NSF weekly or more 
frequently. MMVO observations will provide the following information:
    1. The basis for decisions about shutting down the seismic source.
    2. Information needed to estimate the number of marine mammals 
potentially ``taken by harassment''. These data will be reported to 
NMFS and/or USFWS per terms of MMPA authorizations or regulations.
    3. Data on the occurrence, distribution, and activities of marine 
mammals and turtles in the area where the seismic study is conducted.
    4. Data on the behavior and movement patterns of marine mammals and 
turtles seen at times with and without seismic activity.
    A report will be submitted to NMFS within 90 days after the end of 
the cruise. The report will describe the operations that were conducted 
and sightings of marine mammals and turtles near the operations. The 
report will be submitted to NMFS, providing full documentation of 
methods, results, and interpretation pertaining to all monitoring. The 
90-day report will summarize the dates and locations of seismic 
operations, and all marine mammal and turtle sightings (dates, times, 
locations, activities, associated seismic survey activities). The 
report will also include estimates of the amount and nature of 
potential ``take'' of marine mammals by harassment or in other ways.
    All injured or dead marine mammals (regardless of cause) must be 
reported to NMFS as soon as practicable. Report should include species 
or description of animal, condition of animal, location, time first 
found, observed behaviors (if alive) and photo or video, if available.

Endangered Species Act (ESA)

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

National Environmental Policy Act (NEPA)

    NSF prepared an Environmental Assessment (EA) of a Marine 
Geophysical Survey by the R/V Melville in the Santa Barbara Channel, 
November 2008. NMFS will either adopt NSF's EA or conduct a separate 
NEPA analysis, as necessary, prior to making a

[[Page 50778]]

determination of the issuance of the IHA.

Preliminary Determinations

    NMFS has preliminarily determined that the impact of conducting the 
seismic survey in the SBC may result, at worst, in a temporary 
modification in behavior (Level B Harassment) of small numbers of 26 
species of marine mammals. This activity is expected to result in a 
negligible impact on the affected species or stocks. There are no 
subsistence uses of affected marine mammals in this area.
    For reasons stated previously in this document, this determination 
is supported by: (1) The likelihood that, given sufficient notice 
through relatively slow ship speed, marine mammals are expected to move 
away from a noise source that is annoying prior to its becoming 
potentially injurious; (2) the fact that marine mammals would have to 
be closer than 35 m (114 ft) in water less than 1,000 m to be exposed 
to levels of sound which could result in Level A harassment (injury); 
(3) the 35 m distance is conservative as it is for the airgun opening 
at full chamber size (45 in\3\) and the airgun will likely be operating 
at reduced chamber size; and (4) the marine mammal detection ability by 
trained observers is high at that very short distance from the vessel. 
As a result, no take by injury or death is anticipated, and the 
potential for temporary or permanent hearing impairment is very low and 
will be avoided through the incorporation of the proposed mitigation 
measures.
    While the number of marine mammals potentially harassed will depend 
on the distribution and abundance of marine mammals in the vicinity of 
the survey activity, the number of potential harassment takings is 
estimated to be small, less than a few percent of any of the estimated 
population sizes, and has been mitigated to the lowest level 
practicable through incorporation of the measures mentioned previously 
in this document.

Proposed Authorization

    As a result of these preliminary determinations, NMFS proposes to 
issue an IHA to SIO for conducting a marine geophysical survey in the 
Santa Barbara Channel, November 2008, provided the previously mentioned 
mitigation, monitoring, and reporting requirements are incorporated.

    Dated: August 22, 2008.
Helen M. Golde,
Deputy Director, Office of Protected Resources, National Marine 
Fisheries Service.
[FR Doc. E8-20014 Filed 8-27-08; 8:45 am]
BILLING CODE 3510-22-P`