[Federal Register Volume 75, Number 171 (Friday, September 3, 2010)]
[Notices]
[Pages 54095-54114]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2010-22080]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XY12


Takes of Marine Mammals Incidental to Specified Activities; Low-
Energy Marine Seismic Survey in the Eastern Tropical Pacific Ocean Off 
Central and South America, October-November 2010

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

ACTION: Notice; proposed Incidental Harassment Authorization; request 
for comments.

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SUMMARY: NMFS has received an application from the Scripps Institution 
of Oceanography (SIO) of the University of California for an Incidental 
Harassment Authorization (IHA) to take marine mammals, by harassment, 
incidental to conducting a low-energy marine seismic survey. Pursuant 
to the Marine Mammal Protection Act (MMPA), NMFS is requesting comments 
on its proposal to issue an IHA to SIO to take, by Level B Harassment 
only, 21 species of marine mammals during the specified activity.

DATES: Comments and information must be received no later than October 
4, 2010.

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. The mailbox address for providing e-
mail comments is [email protected]. NMFS is not responsible for e-
mail comments sent to addresses other than the one provided here. 
Comments sent via e-mail, including all attachments, must not exceed a 
10-megabyte file size.
    Instructions: All comments received are a part of the public record 
and will generally be posted to http://www.nmfs.noaa.gov/pr/permits/incidental.htm without change. All Personal Identifying Information 
(for example, name, address, etc.) voluntarily submitted by the 
commenter may be publicly accessible. Do not submit Confidential 
Business Information or otherwise sensitive or protected information.
    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. The National Science 
Foundation (NSF), which is providing funding for the proposed action, 
has prepared a draft Environmental Assessment (EA) titled ``Marine 
Geophysical Survey by the R/V Melville in the Pacific Ocean off Central 
and South America, October-November 2010''. The NSF draft EA 
incorporates an ``Environmental Assessment of a Marine Geophysical 
Survey by the R/V Melville in the Pacific Ocean off Central and South 
America, October-November 2010'', prepared by LGL Limited, 
Environmental Research Associates, on behalf of NSF. These associated 
documents, prepared in compliance with the National Environmental 
Policy Act (NEPA), are also available at the same Internet address. 
Documents cited in this notice may also be viewed, by appointment, 
during regular business hours, at the aforementioned address.

FOR FURTHER INFORMATION CONTACT: Ben Laws or Candace Nachman, 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 small numbers of marine 
mammals by U.S. citizens who engage in a specified activity (other than 
commercial fishing) within a specified geographical region if certain 
findings are made and either regulations are issued or, if the taking 
is limited to harassment, a notice of a proposed

[[Page 54096]]

authorization is provided to the public for review.
    Authorization for incidental takings shall be granted if NMFS finds 
that the taking will have a negligible impact on the species or 
stock(s), will not have an unmitigable adverse impact on the 
availability of the species or stock(s) for subsistence uses (where 
relevant), and if the permissible methods of taking and requirements 
pertaining to the mitigation, monitoring and reporting of such takings 
are set forth. NMFS has defined ``negligible impact'' in 50 CFR 216.103 
as ``* * * an impact resulting from the specified activity that cannot 
be reasonably expected to, and is not reasonably likely to, adversely 
affect the species or stock through effects on annual rates of 
recruitment or survival.''
    Section 101(a)(5)(D) of the MMPA established an expedited process 
by which citizens of the U.S. can apply for an authorization to 
incidentally take small numbers of marine mammals by harassment. 
Section 101(a)(5)(D) establishes a 45-day time limit for NMFS review of 
an application followed by a 30-day public notice and comment period on 
any proposed authorizations for the incidental harassment of marine 
mammals. Within 45 days of the close of the comment period, NMFS must 
either issue or deny the authorization. Except with respect to certain 
activities not pertinent here, the MMPA defines ``harassment'' as:

any act of pursuit, torment, or annoyance which (i) has the 
potential to injure a marine mammal or marine mammal stock in the 
wild [Level A harassment]; or (ii) has the potential to disturb a 
marine mammal or marine mammal stock in the wild by causing 
disruption of behavioral patterns, including, but not limited to, 
migration, breathing, nursing, breeding, feeding, or sheltering 
[Level B harassment].

Summary of Request

    NMFS received an application on May 28, 2010 from SIO for the 
taking, by harassment, of marine mammals incidental to conducting, in 
collaboration with Texas A&M University and with research funding 
provided by the National Science Foundation, a low-energy marine 
seismic survey. NMFS reviewed SIO's application and identified a number 
of issues requiring further clarification. After addressing comments 
from NMFS, SIO modified its application and submitted a revised 
application on July 14, 2010. NMFS carefully evaluated SIO's 
application, including their analyses, and determined that the 
application is complete and provides sufficient data for NMFS to make 
the necessary preliminary determinations pursuant to the MMPA. The July 
14, 2010 application is the one available for public comment (see 
ADDRESSES) and considered by NMFS for this proposed IHA.
    The proposed survey will occur in the Eastern Tropical Pacific 
Ocean (ETP), encompassing the area from approximately 8[deg] N-12[deg] 
S and 80-91[deg] W, off the coasts of Costa Rica, Panama, Colombia, 
Ecuador, and Peru, in International Waters and within the Exclusive 
Economic Zones (EEZs) of Costa Rica, Panama, Colombia, and Ecuador, and 
is scheduled to occur from October 19-November 14, 2010. Some minor 
deviation from these dates is possible, depending on logistics and 
weather. The survey will use a pair of Generator Injector (GI) airguns, 
each with a discharge volume of 45 in\3\. Seismic airgun operations are 
expected to result in the incidental take, by Level B harassment only, 
of up to 21 species of marine mammals. These species include: Bryde's 
whale; blue whale; sperm whale; humpback whale; Cuvier's beaked whale; 
Blainville's beaked whale; pygmy beaked whale; gingko-toothed beaked 
whale; rough-toothed dolphin; bottlenose dolphin; pantropical spotted 
dolphin; spinner dolphin; striped dolphin; Fraser's dolphin; short-
beaked common dolphin; Risso's dolphin; melon-headed whale; pygmy 
killer whale; false killer whale; killer whale; and short-finned pilot 
whale.

Description of the Specified Activity

    SIO plans to conduct a seismic survey as part of an integrated 
geophysical and geochemical study. In addition to the GI airguns, a 
multibeam echosounder (MBES) and a sub-bottom profiler (SBP) will be 
utilized for research purposes. The planned survey will involve one 
source vessel, the R/V Melville (Melville).
    The purpose of this project is to better understand how marine 
sediments record paleo-oceanographic information. The deposition of 
sediments in the upper 500 m (1640.4 ft) of the sediment column will be 
studied using known seismic horizons in the sediment column to estimate 
rates of deposition downstream from potential sediment sources on the 
topographic highs and to estimate loss from the ridges. The seismic 
survey and associated coring and water sampling will allow comparisons 
of geophysical estimates of the level of erosion from marine ridges and 
highs with geochemical estimates of sediment focusing based upon the 
distribution of Th-230, a particle-reactive isotope produced by the 
decay of dissolved uranium in the water column. In addition, the study 
will examine whether there are sediment sources for Th-230 in slowly-
accumulating sediments.
    The Melville is expected to depart Puntarenas, Costa Rica, on 
October 19, 2010, and spend approximately 15 days conducting seismic 
surveys, 10 days collecting water and core samples, and approximately 2 
days in transit, arriving at Arica, Chile, on November 14, 2010. At 
each of four sites (see Figure 1 of SIO's application), seismic 
operations will be conducted for approximately 2 days, and each water 
sampling and coring station will be occupied for 1-2 days. Some minor 
deviation from these dates is possible, depending on logistics and 
weather.
    The source vessel, the Melville, will deploy a pair of low-energy 
GI airguns as an energy source at a depth of 2 m (each with a discharge 
volume of 45 in\3\), plus either of two towed hydrophone streamers, one 
725 m (2378.6 ft) long with 40 channels, and the other 350 m (1148.3 
ft) long with 16 channels. Hydrophone streamers are towed at adjustable 
depth to afford best reception of returning seismic signals, depending 
upon surface conditions, but are typically towed in at approximately 10 
m. The energy to the GI airgun is compressed air supplied by 
compressors onboard the source vessel. As the GI airgun is towed along 
the survey lines, the receiving systems will receive the returning 
acoustic signals.
    In addition to the GI airguns, an MBES and an SBP will be used 
throughout the cruise, except while at water/core stations, to help 
verify seafloor conditions at possible coring sites and to collect 
additional seafloor bathymetric data. Passive geophysical sensors (a 
gravimeter and a magnetometer) will also be operated continuously 
throughout the entire cruise.
    All potential incidental take, by harassment only, is expected to 
result from the operation of the GI airguns. Take is not expected to 
result from the use of the MBES or SBP, for reasons discussed below, or 
from collision with the vessel because it is a single vessel, moving at 
a relatively slow speed (operational speeds of approximately 11 km/hr 
[6 knots] during seismic acquisition within the survey areas and 15-
18.5 km/hr [8-10 knots] between survey areas and stations), for a 
relatively short period of time (approximately 30 days). It is likely 
that any marine mammal would be able to avoid the vessel.
    The seismic program will consist of approximately 5475 km (3402 mi) 
of

[[Page 54097]]

survey lines, including turns (see Figure 1 of SIO's application). 
Water depths at the seismic survey locations are approximately 1000-
4800 m (3280.8-15,748 ft). The GI airguns will be operated on a small 
grid for approximately 45 hours at each of four sites (see Figure 1 of 
SIO's application) where the 40-channel streamer will be used, and for 
most of the time during transits between the sites, to the first site, 
and after the last site, where the 12-channel streamer will be used. 
There will be additional seismic operations associated with equipment 
testing, startup, and possible line changes or repeat coverage of any 
areas where initial data quality is sub-standard. Those additional 
operations are allowed for in the estimated total line-kilometers given 
above. The Melville is expected to depart Puntarenas, Costa Rica, on 
October 19, 2010 and spend approximately 15 days conducting seismic 
surveys, 10 days collecting water and core samples, and approximately 2 
days in transit, arriving at Arica, Chile, on November 14, 2010.
    All planned geophysical data acquisition activities will be 
conducted by SIO with on-board assistance by the scientists who have 
proposed the study. The Chief Scientist is Dr. Franco Marcantonio of 
Texas A&M University. The vessel will be self-contained, and the crew 
will live aboard the vessel for the entire cruise.

Vessel Specifications

    The Melville has a length of 85 m (278.9 ft), a beam of 14 m (45.9 
ft), and a maximum draft of 5 m (16.4 ft). The ship is powered by two 
1385-hp diesel engines and a 900-hp retracting azimuthing bow thruster. 
Operation speeds of approximately 11 km/hr (5.9 knots) and 15-18.5 km/
hr (8.1-10 knots) will be used during seismic acquisition within the 
survey areas and between the areas and stations, respectively. When not 
towing seismic survey gear, the Melville cruises at 21.7 km/hr (11.7 
knots) and has a maximum speed of 25.9 km/hr (14 knots). The Melville 
will also serve as the platform from which vessel-based protected 
species observers (PSOs) will watch for animals before and during 
airgun operations (discussed later in this document).

Acoustic Source Specifications

(1) Seismic Airguns
    The Melville will tow a pair of 45-in\3\ Sercel GI airguns and a 
streamer containing hydrophones along predetermined lines. Seismic 
pulses will be emitted at intervals of 8-10 s. At speeds of 
approximately 11-18.5 km/hr (5.9-10 knots), the 8-10 s spacing 
corresponds to shot intervals of approximately 25-50 m (82-164 ft).
    The generator chamber of each GI airgun, responsible for 
introducing the sound pulse into the ocean, is 45 in\3\. The larger 
(105-in\3\) injector chamber injects air into the previously-generated 
bubble to maintain its shape and does not introduce more sound into the 
water. The two 45-in\3\ GI airguns will be towed 8 m (26.2 ft) apart 
side by side, 21 m (68.9 ft) behind the Melville, at a depth of 2 m 
(6.6 ft).
    As the GI airgun is towed along the survey line, the towed 
hydrophone array in the streamer receives the reflected signals and 
transfers 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 (greater than l km (0.6 mi)). Thus, the maneuverability 
of the vessel is not limited much during operations.
    The root mean square (rms) received levels that are used as impact 
criteria for marine mammals are not directly comparable to the peak (pk 
or 0-pk) or peak-to-peak (pk-pk) values normally used to characterize 
source levels of airgun arrays. The measurement units used to describe 
airgun sources, peak or peak-to-peak decibels, are always higher than 
the rms decibels referred to in biological literature. A measured 
received level of 160 dB re 1 [mu]Pa (rms) in the far field would 
typically correspond to a peak measurement of approximately 170 dB and 
to a peak-to-peak measurement of approximately 176-178 dB, as measured 
for the same pulse received at the same location (Greene, 1997; 
McCauley et al., 1998, 2000). The precise difference between rms and 
peak or peak-to-peak values depends on the frequency content and 
duration of the pulse, among other factors. However, the rms level is 
always lower than the peak or peak-to-peak level for an airgun-type 
source. The actual received level at any location in the water near the 
GI airguns will not exceed the source level of the strongest individual 
source. In this case, that will be about 224.6 dB re 1 [micro]Pa-m peak 
or 229.8 dB re 1 [micro]Pa-m peak-to-peak. The dominant frequency 
components of the GI airguns are 0-188 Hertz (Hz).
    Received sound levels have been modeled by Lamont-Doherty Earth 
Observatory (L-DEO) for a number of airgun configurations, including 
two 45 in\3\ Nucleus G. Guns, in relation to distance and direction 
from the airgun (see Figure 2 of SIO's application). 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 airguns where sound levels of 190, 180, and 160 dB re 1 [mu]Pa 
(rms) are predicted to be received in deep (>1,000 m (3280.8 ft)) water 
are shown in Table 1 below. Because the model results are for G. Guns, 
which have more energy than GI airguns of the same size, the distances 
in Table 1 overestimate the distances for the 45 in\3\ GI airguns.
(2) Multibeam Echosounder and Sub-Bottom Profiler
    Along with the GI airgun operations, an MBES and a SBP will be 
operated from the source vessel at certain times during the planned 
study to help verify seafloor conditions at possible coring sites and 
to collect additional seafloor bathymetric data.
    The Kongsberg EM 122 MBES operates at 10.5-13 (usually 12) 
kilohertz (kHz) and is hull-mounted on the Melville. The transmitting 
beamwidth is 1[deg] fore-aft and 150[deg] athwartship. The maximum 
source level is 242 dB re 1 [mu]Pa-m (rms). Each ``ping'' consists of 
eight (in water >1000 m deep) or four (<1000 m deep) successive fan-
shaped transmissions, each ensonifying a sector that extends 1[deg] 
fore-aft. Continuous-wave pulses increase from 2 to 15 ms long in water 
depths up to 2600 m (8530.2 ft), and FM chirp pulses up to 100 ms long 
are used in water >2600 m. The successive transmissions span an overall 
cross-track angular extent of about 150[deg], with 2-ms gaps between 
the pulses for successive sectors.
    The Knudsen Engineering Model 320B/R SBP is a dual-frequency 
transceiver designed to operate at 3.5 and/or 12 kHz. It is used in 
conjunction with the MBES to provide data about the sedimentary 
features that occur below the sea floor. The energy from the SBP is 
directed downward via a 3.5-kHz transducer array mounted in the hull of 
the Melville. The maximum power output of the 320B/R is 10 kilowatts 
for the 3.5-kHz section and 2 kilowatts for the 12-kHz section. The 
nominal beamwidth is 80[deg].
    The pulse length for the 3.5-kHz section of the 320B/R is 0.8-24 
ms, controlled by the system operator in regards to water depth and 
reflectivity of the bottom sediments and will usually be 6, 12, or 24 
ms at the water depths at the study sites and in transit from 
Puntarenas and to Arica. The system produces one sound pulse and then 
waits for its return before transmitting again. Thus, the pulse

[[Page 54098]]

interval is directly dependent upon water depth, and in this survey is 
0.8-1.5 s. Using the Sonar Equations and assuming 100 percent 
efficiency in the system (impractical in real world applications), the 
source level for the 320B/R is calculated to be 211 dB re 1 [mu]Pa-m. 
In practice, the system is rarely operated above 80 percent power 
level.
(3) Safety Radii
    NMFS has determined that for acoustic effects, using acoustic 
thresholds in combination with corresponding safety radii is an 
effective way to consistently apply measures to avoid or minimize the 
impacts of an action, and to quantitatively estimate the effects of an 
action. Thresholds are used in two ways: (1) To establish a mitigation 
shut-down or power-down zone, i.e., if an animal enters an area 
calculated to be ensonified above the level of an established 
threshold, a sound source is powered down or shut down; and (2) to 
calculate take, in that a model may be used to calculate the area 
around the sound source that will be ensonified to that level or above, 
then, based on the estimated density of animals and the distance that 
the sound source moves, NMFS can estimate the number of marine mammals 
that may be ``taken.''
    As a matter of past practice and based on the best available 
information at the time regarding the effects of marine sound, NMFS 
estimates that Level A harassment from acoustic sources may occur when 
animals are exposed to levels above 180 dB re 1 [mu]Pa (rms) level for 
cetaceans and 190 dB re 1 [mu]Pa (rms) for pinnipeds. A review of the 
available scientific data using an application of science-based 
extrapolation procedures (Southall et al., 2007) strongly suggests that 
Level A harassment (as well as temporary threshold shift (TTS)) from 
single sound exposure impulse events may occur at much higher levels 
than the levels previously estimated using very limited data. However, 
for purposes of this proposed action, SIO's application sets forth, and 
NMFS is using, the more conservative 180 and 190 dB re 1 [mu]Pa (rms) 
criteria. NMFS also considers 160 dB re 1 [mu]Pa (rms) as the criterion 
for estimating the onset of Level B harassment from acoustic sources 
producing impulse sounds, as in this seismic survey.
    Empirical data concerning the 180- and 160-dB distances have been 
acquired based on measurements during the acoustic verification study 
conducted by L-DEO in the northern Gulf of Mexico from May 27-June 3, 
2003 (Tolstoy et al., 2004). Although the results are limited, the data 
showed that radii around the airguns where the received level would be 
180 dB re 1 [mu]Pa (rms), the safety criterion 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 
proposed survey will occur in depths of approximately 1000-4800 m, so 
the correction factors for shallow water are not relevant here. All of 
the seismic operations will be in depths >1000 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 values 
predicted by L-DEO's model (see Table 1 in this document). Therefore, 
the assumed 180- and 190-dB radii are 40 m (131.2 ft) and 10 m (32.8 
ft), respectively.

Table 1--Predicted Distances To Which Sound Levels [gteqt]190, 180 and 160 dB re 1 [mu]Pa (rms) Might Be Received From Two 45 in\3\ GI Airguns That Will
                          Be Used During the Seismic Surveys in the Eastern Tropical Pacific Ocean During October-November 2010
                                                [Distances are based on model results provided by L-DEO.]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                        Estimated distances at received levels (m)
              Source and volume                 Tow depth (m)              Water depth          --------------------------------------------------------
                                                                                                       190 dB             180 dB             160 dB
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Two GI airguns, 45 in\3\ each...............                 2   Deep (>1000 m)................                10                 40                400
--------------------------------------------------------------------------------------------------------------------------------------------------------

Description of Marine Mammals in the Area of the Specified Activity

    Forty-three species of marine mammals, including 29 odontocetes, 7 
mysticetes, 6 pinnipeds, and the marine sea otter (Enhydra lutris), are 
known to occur in the ETP. Of these, 23 cetacean species are likely to 
occur in the proposed survey areas in the ETP during October-November 
(see Table 2 in this document), and are considered further here. Three 
of these 23 cetacean species are listed under the Endangered Species 
Act (ESA) as Endangered: The sperm (Physeter macrocephalus), humpback 
(Megaptera novaeangliae), and blue (Balaenoptera musculus) whales.
    Nine cetacean species, although present in the wider ETP, likely 
would not be found in the proposed seismic survey areas because their 
ranges do not extend that far south or north. Pacific white-sided 
dolphins (Lagenorhynchus obliquidens) and Baird's beaked whales 
(Berardius bairdii) are seen very occasionally in the northernmost 
portions of the ETP (Ferguson and Barlow, 2001). Long-beaked common 
dolphins (Delphinus capensis) are known to occur in the northernmost 
areas of the ETP off Baja California, Mexico, and off the coast of Peru 
(Heyning and Perrin, 1994). Southern right whales (Eubalaena australis) 
are seen on rare occasions off the coasts of Peru and Chile (Aguayo et 
al., 1992; Santillan et al., 2004). Gray's beaked whales (Mesoplodon 
grayi) are distributed in the southernmost portions of the ETP and off 
the coast of southern Peru (Culik, 2010). Dusky dolphins 
(Lagenorhynchus obscurus), southern right whale dolphins (Lissodelphis 
peronii), Burmeister's porpoises (Phocoena spinipinnis), and long-
finned pilot whales (Globicephala melas) also occur near the Peruvian 
coast (Leatherwood et al., 1991; Van Waerebeek et al., 1991; Brownell 
and Clapham, 1999; Olson and Reilly, 2002). These nine species are not 
addressed in detail in SIO's application and are not considered further 
in this Notice of Proposed IHA.
    Sei (Balaenoptera borealis) and fin (B. physalus) whales, listed as 
Endangered under the ESA, are known from the ETP but are considered 
very rare in the proposed survey area. Sei whales may have been sighted 
during surveys in the ETP (Wade and Gerrodette, 1993; Kinzey et al., 
1999, 2000, 2001); however, it is difficult to distinguish sei whales 
from Bryde's whales (B. edeni) at sea. Because sei whales generally 
have a more northerly and temperate distribution (Leatherwood et al., 
1988), Wade and Gerrodette (1993) classified

[[Page 54099]]

any tentative sei whale observations in the ETP as Bryde's whale 
sightings. Sei whales may also have been sighted near the Galapagos 
Islands (Clarke, 1962); although, Clarke and Aguayo (1965) suggested 
that those sightings could have been Bryde's whales. Although the 
occurrence of sei whales is documented off Costa Rica (Rodriguez-
Herrera et al., 2002), the reliability of the identification is 
uncertain. Neither Ferguson and Barlow (2001) or Jackson et al. (2008) 
positively identified sei whales in or near the proposed project area 
during surveys conducted during July-December. Similarly, Rasmussen et 
al. (2004) did not report sei whales in 8 years of surveys off Costa 
Rica or Panama. No sei whales were detected during L-DEO seismic 
surveys off Costa Rica or Nicaragua in November-December 2004 or 
February-March 2008 (Holst et al., 2005b; Holst and Smultea, 2008), in 
the Hess Deep approximately 1100 km (683.5 mi) west of the Galapagos 
Islands in July 2003 (Smultea and Holst, 2003), or 1600-1950 km (994.2-
1211.7 mi) west of the proposed survey area in April-August 2008 
(Hauser et al., 2008).
    No confirmed fin whale sightings were made in the proposed study 
area during 10 years of survey effort in July-December by Ferguson and 
Barlow (2001) or by Jackson et al. (2008) during July-December surveys 
in 2006. Despite >30 years of NMFS and other surveys, as well as 
stranding records from the Pacific coast of Costa Rica, there have been 
no confirmed records of fin whales (May-Collado et al., 2005). A 
possible sighting of a fin whale in this region occurred off the Osa 
Peninsula in 1997; however, the sighting was not confirmed (May-Collado 
et al., 2005), although Rodriguez-Herrera et al. (2002) list the fin 
whale as having been documented off Costa Rica. No fin whales were 
detected during L-DEO seismic surveys off Costa Rica or Nicaragua in 
November-December 2004 or February-March 2008 (Holst et al., 2005b; 
Holst and Smultea, 2008), in the Hess Deep approximately 1100 km (683.5 
mi) west of the Galapagos Islands in July 2003 (Smultea and Holst, 
2003), or 1600-1950 km (994.2-1211.7 mi) west of the proposed survey 
area in April-August 2008 (Hauser et al., 2008). Sei and fin whales are 
not considered further in this document.
    The general distribution of minke whales (Balaenoptera 
acutorostrata) includes the offshore waters of the study area (Reeves 
et al., 2002). However, minke whales are likely to be rare in the 
survey area. This species has been found off the coast of Costa Rica on 
occasion (Rodriguez-Herrera et al., 2002). No minke whales were found 
in the proposed project region during July-December surveys during 
1986-1996 by Ferguson and Barlow (2001) or in 2006 by Jackson et al. 
(2008). Rasmussen et al. (2004) did not report seeing any minke whales 
in 8 years of surveys (1996-2003) off Costa Rica or in 2001-2003 off 
Panama. May-Collado et al. (2005) also did not report any minkes based 
on compiled sightings off Costa Rica during 1979-2001, nor have minkes 
been reported among compiled strandings off Costa Rica (Rodriguez-
Fonseca and Cubero-Pardo, 2001). Minke whales are unlikely to occur in 
the planned survey areas and are not considered further in this 
document.
    Longman's beaked whale (Indopacetus pacificus), also known as the 
tropical bottlenose whale, is considered rare in the ETP. Although 
widespread throughout the tropical Pacific, the species is considered 
rare because of a scarcity of sightings despite a great deal of survey 
effort (Pitman et al., 1999). In the ETP, most tropical bottlenose 
whale sightings have been made between 3-10[deg] N (Pitman et al., 
1999). Kinzey et al. (2001) reported one sighting of I. pacificus in 
the ETP at about 135[deg] W. Jackson et al. (2008) also reported I. 
pacificus in the ETP well to the west of the proposed study area. No 
Longman's beaked whales were reported by May-Collado et al. (2005) 
based on compiled sightings off Costa Rica from 1979-2001. The species 
is very rare in the study area and is not considered further in this 
document.
    Dwarf (Kogia sima) and pygmy (K. breviceps) sperm whales may occur 
in the proposed survey area, although dwarf sperm whales are likely to 
be very rare and pygmy sperm whales are likely to be rare. No Kogia sp. 
were detected during L-DEO seismic surveys off Costa Rica and Nicaragua 
in November-December 2004 (Holst et al., 2005b) or in the Hess Deep 
approximately 1100 km (683.5 mi) west of the Galapagos Islands in July 
2003 (Smultea and Holst, 2003). One sighting of a dwarf sperm whale and 
one sighting of two pygmy sperm whales were observed off the coast of 
Costa Rica in waters approximately 2000 m (6561.7 ft) and 3500 m 
(11482.9 ft) deep, respectively, during an L-DEO seismic survey off 
Costa Rica and Nicaragua in February-March 2008 (Holst and Smultea, 
2008), and one unidentified Kogia sp. was sighted during L-DEO seismic 
surveys 1600-1950 km (994.2-1211.7 mi) west of the proposed survey area 
in April-August 2008 (Hauser et al., 2008). Due to the rarity of these 
species, no take has been requested and none will be authorized.
    Six species of pinnipeds are known to occur in the ETP: The 
Guadalupe fur seal (Arctocephalus townsendi), California sea lion 
(Zalophus californianus), Galapagos sea lion (Z. wollebaeki), Galapagos 
fur seal (A. galapagoensis), southern sea lion (Otaria flavescens), and 
the South American fur seal (A. australis). Ranges of the first two are 
substantially north of the proposed seismic survey areas, and the last 
four species are not expected to occur in the offshore waters of the 
study areas. The marine sea otter, which is managed by the U.S. Fish 
and Wildlife Service, is a coastal species and does not occur in 
offshore waters. Pinnipeds are highly unlikely to occur in the survey 
area and are not considered in further detail here.
    The ETP is a biologically productive area that supports a variety 
of cetacean species (Au and Perryman, 1985). Several studies of marine 
mammal distribution and abundance have been conducted in the wider ETP. 
The most extensive regional distribution and abundance data that 
encompass the study area come primarily from multi-year vessel surveys 
conducted in the wider ETP by the NMFS Southwest Fisheries Science 
Center (SWFSC). Information on the distribution of cetaceans inhabiting 
the ETP has been summarized in several studies (Polacheck, 1987; Wade 
and Gerrodette, 1993; Ferguson and Barlow, 2001; Gerrodette et al., 
2008). However, for some species, abundance in the proposed seismic 
survey area could be quite different from that of the wider ETP, 
depending on local oceanographic variability.
    In addition, procedures used during the various surveys that are 
cited have differed somewhat, and those differences could affect the 
results. For example, Ferguson and Barlow (2001) calculated cetacean 
densities in the ETP based on summer/fall research surveys in 1986-
1996. Their densities are corrected for both changes in detectability 
of species with distance from the survey track line and for perception 
and availability bias. Gerrodette et al. (2008) calculated dolphin 
abundance in the ETP based on summer/fall research surveys in 1986-
1990, 1998-2000, 2003, and 2006. Their estimates are corrected for the 
former but not the latter.
    Additional sighting records are available from recent surveys in 
the ETP. Jackson et al. (2008) described cetacean sightings data 
collected during a survey from July 28-December 7, 2006. The survey 
area extended from 30[deg] N-18[deg] S from the coastline to 153[deg] 
W, overlapping with the proposed

[[Page 54100]]

seismic survey area. Rasmussen et al. (2004) and Calambokidis et al. 
(2010) described cetacean sightings resulting from humpback whale 
surveys off Costa Rica and surrounding waters from January to March in 
1996-2003 and 2010. Recent at-sea monitoring for L-DEO in the ETP also 
provided sighting records for cetaceans during seismic programs. 
Seismic monitoring programs took place at the Hess Deep in July 2003, 
approximately 1100 km (683.5 mi) west of the Galapagos Islands (Smultea 
and Holst, 2003); from Costa Rica to El Salvador in November-December 
2004, mainly within approximately 100 km (62.1 mi) of the coast in 
water depths extending to 5000 m (16,404.2 ft) (Holst et al., 2005b); 
from Costa Rica to Nicaragua in March-April 2008, up to approximately 
200 km (124.3 mi) from the coast in water depths extending to 5000 m 
(Holst and Smultea, 2008); and approximately 1600-1900 km (994.2-
1,180.6 mi) west of the study area in April-August 2008 (Hauser et al., 
2008).
    Information on the occurrence, distribution, population size, and 
conservation status for each of the 23 cetacean species that may occur 
in the proposed project area during October-November is presented in 
Table 2 in this document. The five species of marine mammals expected 
to be most common in the waters of the project area, all delphinids, 
include the short beaked common dolphin (Delphinus delphis), 
pantropical spotted dolphin (Stenella attenuata), bottlenose dolphin 
(Tursiops truncatus), Risso's dolphin (Grampus griseus), and short-
finned pilot whale (Globicephala macrorhynchus). Additional information 
regarding the abundance and distribution, population status, and life 
history and behavior of these species expected to be found in the 
project area and how the estimated densities were calculated may be 
found in SIO's application. NMFS has reviewed these data and determined 
them to be the best available scientific information for the purposes 
of the proposed IHA. Please refer to the application for that 
information (see ADDRESSES). Additional information can also be found 
in the NMFS Stock Assessment Report (SAR). The Pacific 2009 SAR is 
available at: http://www.nmfs.noaa.gov/pr/pdfs/sars/po2009.pdf.

     Table 2--The Occurrence, Habitat, Regional Abundance, Conservation Status, and Best and Maximum Density
   Estimates for Marine Mammals in or Near the Proposed Low-Energy Seismic Survey Area in the Eastern Tropical
   Pacific Ocean. Cetacean Densities Are Based on NMFS SWFSC Ship Transect Surveys Conducted in 1986-2006 From
   Predictive Modeling (Barlow et al. 2009; Read et al. 2009) or in 1986-1996 From Ferguson and Barlow (2003)
                       [See text and Tables 2-4 in SIO's application for further detail.]
----------------------------------------------------------------------------------------------------------------
                                Occurrence in                        Regional                Density
           Species               survey area        Habitat      population size   ESA \2\    (best)    Density
                                during Oct-Nov                         \1\                     \3\     (max) \4\
----------------------------------------------------------------------------------------------------------------
Mysticetes:
    Bryde's Whale,             Uncommon.......  Pelagic and      13,000 \5\.....  NL......       0.53       1.15
     (Balaenoptera edeni).                       coastal.
    Blue whale, (Balaenoptera  Uncommon.......  Pelagic and      1415 \6\.......  EN......       0.13       0.23
     musculus).                                  coastal.
    Humpback whale,            Uncommon.......  Mainly           NE Pacific 1392  EN......   \15\ 0.1   \15\ 0.2
     (Megaptera novaeangliae).                   nearshore        \13\; SE
                                                 waters and       Pacific 2900
                                                 banks.           \14\.
Odontocetes:
    Sperm whale, (Physeter     Common.........  Usually deep     26,053 \7\.....  EN......       3.95      15.20
     macrocephalus).                             pelagic, steep
                                                 topography.
    Pygmy sperm whale, (Kogia  Rare...........  Deep waters off  NA \8\.........  NL......  \16\ 0.01  \16\ 0.02
     breviceps).                                 shelf.
    Dwarf sperm whale, (Kogia  Very rare......  Deep waters off  11,200 \9\.....  NL......  \16\ 0.01  \16\ 0.02
     sima).                                      shelf.
    Cuvier's beaked whale,     Common.........  Slope and        20,000 \6\.....  NL......       1.83       3.70
     (Ziphius cavirostris).                      pelagic.
    Blainville's beaked        Uncommon.......  Pelagic........  25,300 \10\....  NL......  \17\ 0.21  \17\ 0.37
     whale, (Mesoplodon
     densirostris).
    Pygmy beaked whale,        Uncommon.......  Pelagic........  25,300 \10\....  NL......  \17\ 0.21  \17\ 0.37
     (Mesoplodon peruvianus).
    Gingko-toothed beaked      Very rare......  Pelagic........  25,300 \10\....  NL......  \17\ 0.21  \17\ 0.37
     whale, (Mesoplodon
     stejnegeri).
    Bottlenose dolphin,        Very common....  Coastal, shelf,  335,834........  NL......      15.14      23.09
     (Tursiops truncatus).                       pelagic.
    Rough-toothed dolphin,     Common.........  Mainly pelagic.  107,633........  NL......       1.60       2.34
     (Steno bredanensis).
    Short-beaked common        Very common....  Shelf, pelagic,  3,127,203......  NL......     143.21     242.80
     dolphin, (Delphinus                         high relief.
     delphis).
    Pantropical spotted        Very common....  Coastal and      857,884........  NL......      12.43      22.53
     dolphin, (Stenella                          pelagic.
     attenuata).
    Risso's dolphin, (Grampus  Very common....  Shelf, slope,    110,457........  NL......      10.21      37.40
     griseus).                                   seamounts.
    Spinner dolphin,           Very common....  Coastal and      1,797,716......  NL......       3.81       5.74
     (Stenella longirostris).                    pelagic.
    Striped dolphin,           Very common....  Off continental  964,362........  NL......      35.23      53.67
     (Stenella coeruleoalba).                    shelf.
    Fraser's dolphin,          Common.........  Pelagic........  289,300 \6\....  NL......       1.03       5.60
     (Lagenodelphis hosei).
    Melon-headed whale,        Common.........  Pelagic........  45,400 \6\.....  NL......       2.80       9.30
     (Peponocephala electra).
    Pygmy killer whale,        Uncommon.......  Pelagic........  38,900 \6\.....  NL......       0.60       1.80
     (Feresa attenuata).
    False killer whale,        Uncommon.......  Pelagic........  39,800 \6\.....  NL......       0.39       2.10
     (Pseudorca crassidens).
    Killer whale, (Orcinus     Uncommon.......  Widely           8,500 \11\.....  NL......       0.85       4.00
     orca).                                      distributed.

[[Page 54101]]

 
    Short-finned pilot whale,  Common.........  Mostly pelagic,  589,315 \12\...  NL......       6.29      11.74
     (Globicephala                               high-relief.
     macrorhynchus).
----------------------------------------------------------------------------------------------------------------
NA--Data not available or species status was not assessed. For density estimates, NA indicates that estimates
  would be lower than the lowest estimate in this table.
\1\ Abundance from Gerrodette et al. (2008) unless otherwise stated.
\2\ U.S. Endangered Species Act: EN = Endangered, T = Threatened, NL = Not listed.
\3\ Best density (/1000km\2\) estimate as listed in Table 3 of the application. Cetecean densities are
  based on NMFS SWFSC ship transect surveys conducted in 1986-2006 from predictive modeling (Barlow et al. 2009;
  Read et al. 2009) or in 1986-1996 from Ferguson and Barlow (2003).
\4\ Maximum density (/1000km\2\) estimate as listed in Table 3 of the application.
\5\ This estimate is mainly for Balaenoptera edeni but may include some B. borealis.
\6\ ETP (Wade and Gerrodette 1993).
\7\ Eastern temperate North Pacific (Whitehead 2002).
\8\ California/Oregon/Washington (Carretta et al. 2010).
\9\ This abundance estimate is mostly for Kogia sima but may also include some K. breviceps. Density estimates
  for Kogia spp. combined.
\10\ Estimates for population size and for density include all species of the genus Mesoplodon in the ETP
  (Ferguson and Barlow 2001).
\11\ ETP (Ford 2002).
\12\ This estimate is for Globicephala macrorhynchus and G. melas in the ETP (Gerrodette and Forcada 2002).
\13\ U.S. west coast (Carretta et al. 2010).
\14\ Southeast Pacific; Felix et al. (2005).
\15\ Approximate estimates.
\16\ Density estimates are combined for pygmy and dwarf sperm whales.
\17\ Density estimates are combined for species of the genus Mesoplodon.

Marine Mammal Hearing

    The primary effect on marine mammals anticipated from the specified 
activities will result from exposure of animals to underwater sound. 
Exposure to sound can affect marine mammal hearing. When considering 
the influence of various kinds of sound on the marine environment, it 
is necessary to understand that different kinds of marine life are 
sensitive to different frequencies of sound. Based on available 
behavioral data, audiograms derived using auditory evoked potential 
techniques, anatomical modeling, and other data, Southall et al. (2007) 
designate ``functional hearing groups'' for marine mammals and estimate 
the lower and upper frequencies of functional hearing of the groups. 
The functional groups and the associated frequencies are indicated 
below (though animals are less sensitive to sounds at the outer edge of 
their functional range and most sensitive to sounds of frequencies 
within a smaller range somewhere in the middle of their functional 
hearing range):
     Low frequency cetaceans (13 species of mysticetes): 
Functional hearing is estimated to occur between approximately 7 Hz and 
22 kHz;
     Mid-frequency cetaceans (32 species of dolphins, six 
species of larger toothed whales, and 19 species of beaked and 
bottlenose whales): Functional hearing is estimated to occur between 
approximately 150 Hz and 160 kHz;
     High frequency cetaceans (six species of true porpoises, 
four species of river dolphins, two members of the genus Kogia, and 
four dolphin species of the genus Cephalorhynchus): Functional hearing 
is estimated to occur between approximately 200 Hz and 180 kHz; and
     Pinnipeds in water: Functional hearing is estimated to 
occur between approximately 75 Hz and 75 kHz, with the greatest 
sensitivity between approximately 700 Hz and 20 kHz.
    As mentioned previously in this document, 21 cetacean species are 
likely to occur in the proposed survey area. Of the 21 species likely 
to occur in SIO's project area, two are classified as low frequency 
cetaceans (Bryde's, humpback, and blue whales) and 18 are classified as 
mid-frequency cetaceans (sperm, Cuvier's beaked, Blainville's beaked, 
pygmy beaked, gingko-toothed beaked, melon-headed, pygmy killer, false 
killer, killer, and short-finned pilot whales and rough-toothed, 
bottlenose, pantropical spotted, spinner, striped, Fraser's, short-
beaked common, and Risso's dolphins) (Southall et al., 2007).

Potential Effects of the Specified Activity on Marine Mammals

Potential Effects of Airguns

    The effects of sounds from airguns might result in one or more of 
the following: Tolerance, masking of natural sounds, behavioral 
disturbances, temporary or permanent hearing impairment, and non-
auditory physical or physiological effects (Richardson et al., 1995; 
Gordon et al., 2004; Nowacek et al., 2007; Southall et al., 2007). 
Permanent hearing impairment, or PTS, in the unlikely event that it 
occurred, would constitute injury, but temporary threshold shift (TTS) 
is not an injury (Southall et al., 2007). 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 for reasons discussed later in this document. 
Some behavioral disturbance is expected, but it is expected that this 
would be localized and short-term because of the short amount of time 
that would be spent at any particular site within the survey area 
(approximately two days of seismic data acquisition at any one site).
(1) Tolerance
    Numerous studies have shown that pulsed sounds from airguns are 
often readily detectable in the water at

[[Page 54102]]

distances of many kilometers. For a brief summary of the 
characteristics of airgun pulses, see Appendix A(3) of the supporting 
EA (see ADDRESSES). However, it should be noted that most of the 
measurements are for airguns that would be detectable considerably 
farther away than the GI airgun planned for use in the present project.
    Several studies have shown that marine mammals at distances more 
than a few kilometers from operating seismic vessels often show no 
apparent response; see Appendix A(5) of the EA. That is often true even 
in cases when the pulsed sounds must be readily audible to the animals 
based on measured received levels and the hearing sensitivity of the 
mammal group. Although various baleen whales, toothed whales, and (less 
frequently) pinnipeds have been shown to react behaviorally to airgun 
pulses under some conditions, at other times, mammals of all three 
types have shown no overt reactions. In general, pinnipeds usually seem 
to be more tolerant of exposure to airgun pulses than are cetaceans, 
with the relative responsiveness of baleen and toothed whales being 
variable. Given the relatively small and low-energy GI airgun source 
planned for use in this project, mammals are expected to tolerate being 
closer to this source than would be the case for a larger airgun source 
typical of most seismic surveys.
(2) Masking
    Obscuring of sounds of interest by interfering sounds, generally at 
similar frequencies, is known as masking. Masking effects of pulsed 
sounds (even from large arrays of airguns, much larger than that 
proposed for use in this survey) on marine mammal calls and other 
natural sounds are expected to be limited, although there are few 
specific data of relevance. Because of the intermittent nature and low 
duty cycle of seismic pulses, animals can emit and receive sounds in 
the relatively quiet intervals between pulses. However, in some 
situations, multi-path arrivals and reverberation cause airgun sound to 
arrive for much or all of the interval between pulses (Simard et al., 
2005; Clark and Gagnon, 2006), which could mask calls. Whale calls 
often can be heard between the seismic pulses (Richardson et al., 1986; 
McDonald et al., 1995; Greene et al., 1999a,b; Nieukirk et al., 2004; 
Smultea et al., 2004; Holst et al., 2005a,b, 2006; Dunn and Hernandez, 
2009), and certain baleen and toothed whales are known to continue 
calling in the presence of seismic pulses. However, Clark and Gagnon 
(2006) reported that fin whales in the northeast Pacific Ocean went 
silent for an extended period starting soon after the onset of a 
seismic survey in the area. Similarly, there has been one report that 
sperm whales ceased calling when exposed to pulses from a very distant 
seismic ship (Bowles et al., 1994). However, more recent studies found 
that sperm whales continued calling in the presence of seismic pulses 
(Madsen et al., 2002; Tyack et al., 2003; Smultea et al., 2004; Holst 
et al., 2006; Jochens et al., 2008). Given the small source planned for 
use during the proposed survey, there is even less potential for 
masking of baleen or sperm whale calls during the present study than in 
most seismic surveys. Masking effects of seismic pulses are expected to 
be negligible in the case of small odontocetes, given the intermittent 
nature of seismic pulses. Dolphins and porpoises commonly are heard 
calling while airguns are operating (Gordon et al., 2004; Smultea et 
al., 2004; Holst et al., 2005a,b; Potter et al., 2007). 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. Masking effects on marine 
mammals are discussed further in Appendix A(4) of the EA.
(3) Disturbance Reactions
    Disturbance includes a variety of effects, including subtle changes 
in behavior, more conspicuous changes in activities, and displacement. 
Reactions to sound, if any, depend on species, state of maturity, 
experience, current activity, reproductive state, time of day, and many 
other factors (Richardson et al., 1995; Wartzok et al., 2004; Southall 
et al., 2007; Weilgart, 2007). If a marine mammal responds to an 
underwater sound by changing its behavior or moving a small distance, 
the response may or may not rise to the level of ``taking'', or affect 
the stock or the species as a whole. However, if a sound source 
displaces marine mammals from an important feeding or breeding area for 
a prolonged period, impacts on animals or on the stock or species could 
potentially be significant (Lusseau and Bejder, 2007; Weilgart, 2007). 
Given the many uncertainties in predicting the quantity and types of 
impacts of noise on marine mammals, it is common practice to estimate 
how many mammals are likely to be present within a particular distance 
of a given activity, or exposed to a particular level of sound. This 
practice potentially overestimates the numbers of marine mammals that 
are affected in some biologically-important manner.
    The sound exposure thresholds that are used to estimate how many 
marine mammals might be harassed by a seismic survey are based on 
behavioral observations during studies of several species. However, 
information is lacking for many species. Detailed studies have been 
done on humpback, gray (Eschrichtius robustus), bowhead (Balaena 
mysticetus), and sperm whales, and on ringed seals (Phoca 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. Most of those 
studies have concerned reactions to much larger airgun sources than 
planned for use in the proposed SIO project. Thus, effects are expected 
to be limited to considerably smaller distances and shorter periods of 
exposure in the present project than in most of the previous work 
concerning marine mammal reactions to airguns.
    Baleen Whales--Baleen whales generally tend to avoid operating 
airguns, but avoidance radii are quite variable. Whales are often 
reported to show no overt reactions to pulses from large arrays of 
airguns at distances beyond a few kilometers, even though the airgun 
pulses remain well above ambient noise levels out to much longer 
distances. However, as reviewed in Appendix A(5) of the EA, baleen 
whales exposed to strong noise pulses from airguns often react by 
deviating from their normal migration route (Richardson et al., 1999) 
and/or interrupting their feeding activities and moving away from the 
sound source. 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 (Schick and Urban, 2000; 
Richardson et al., 1999; Malme et al., 1983).
    Studies of gray, bowhead, and humpback whales have shown that 
seismic pulses with received levels of pulses in the 160-170 dB re 1 
[mu]Pa (rms) range 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 4.5-14.5 km (2.8-9 mi) from the 
source. A substantial proportion of the baleen whales within those 
distances may show avoidance or other strong

[[Page 54103]]

disturbance reactions to the airgun array. Subtle behavioral changes 
sometimes become evident at somewhat lower received levels, and studies 
summarized in Appendix A(5) of the 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). Reaction distances would be considerably smaller during the 
proposed project, for which the 160 dB radius is predicted to be 400 m 
(1312.3 ft) (see Table 1 in this document), as compared with several 
kilometers when a large array of airguns is operating.
    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 a source level of 227 dB re 1 [mu]Pa-m peak-to-peak. 
McCauley et al. (1998) documented that initial avoidance reactions 
began at 5-8 km (3.1-5 mi) from the array, and that those reactions 
kept most pods approximately 3-4 km (1.9-2.5 mi) from the operating 
seismic boat. McCauley et al. (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 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 received sound levels. The mean received level 
for initial avoidance reactions to an approaching airgun was 140 dB re 
1 [mu]Pa (rms) for humpback whale pods containing females. The standoff 
range, i.e., the mean closest point of approach of the whales to the 
airgun, corresponded to a received level of 143 dB re 1 [mu]Pa (rms). 
The initial avoidance response generally occurred at distances of 5-8 
km (3.1-5.0 mi) from the airgun array and 2 km (1.2 mi) from the single 
airgun. However, some individual humpback whales, especially males, 
approached within distances of 100-400 m (328.1-1312.3 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 100-in \3\ airgun (Malme et al., 1985). Some humpbacks seemed 
``startled'' at received levels of 150-169 dB re 1 [mu]Pa on an 
(approximate) rms basis. Malme et al. (1985) concluded that there was 
no clear evidence of avoidance, despite the possibility of subtle 
effects, at received 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 results from direct studies of humpback 
whales 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).
    Studies of bowhead whales show that their responsiveness can be 
quite variable depending on the activity (e.g., migrating vs. feeding). 
Bowhead whales migrating west across the Alaskan Beaufort Sea in 
autumn, in particular, are unusually responsive, with substantial 
avoidance occurring out to distances of 20-30 km (12.4-18.6 mi) from a 
medium-sized airgun source at received sound levels of around 120-130 
dB re 1 [mu]Pa (rms) (Miller et al., 1999; Richardson et al., 1999; see 
also Appendix A (5) of the EA). However, more recent research on 
bowhead whales (Miller et al., 2005; Harris et al., 2007) corroborates 
earlier evidence that, during the summer feeding season, bowheads are 
not as sensitive to seismic sources. Nonetheless, subtle but 
statistically significant changes in surfacing-respiration-dive cycles 
were evident upon statistical analysis (Richardson et al., 1986). In 
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 ceased 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 with observations of Western Pacific gray whales 
feeding off Sakhalin Island, Russia, when a seismic survey was underway 
just offshore of their feeding area (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). 
Gray whales typically show no conspicuous responses to airgun pulses 
with received levels up to 150 to 160 dB re 1 [mu]Pa (rms), but are 
increasingly likely to show avoidance as received levels increase above 
that range. While neither bowhead nor gray whales are present in the 
study area, these studies can be used to draw general inference about 
the potential reactions of other baleen whales to underwater sound.
    Various species of the genus Balaenoptera (e.g., blue, sei, fin, 
Bryde's, and minke whales) have occasionally been reported in areas 
ensonified by airgun pulses (Stone, 2003; MacLean and Haley, 2004; 
Stone and Tasker, 2006), and calls from blue and fin whales have been 
localized in areas with airgun operations (McDonald et al., 1995; Dunn 
and Hernandez, 2009). Sightings by observers on seismic vessels off the 
United Kingdom from 1997-2000 suggest that, at times of good 
sightability, sighting rates for mysticetes (mainly fin and sei whales) 
were similar when large arrays of airguns were shooting and not 
shooting (Stone, 2003; Stone and Tasker, 2006). However, these whales 
tended to exhibit localized avoidance, remaining significantly 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 vs. silent. 
However, there were indications that these whales were more likely to 
be moving away when seen during airgun operations. Similarly, ship-
based monitoring studies of blue, fin, sei, and minke whales offshore 
of Newfoundland (Orphan Basin and Laurentian Sub-basin) found no more 
than small differences in sighting rates and swim direction during 
seismic vs. non-seismic periods (Moulton et al., 2005, 2006a,b).
    Data on short-term reactions, or lack thereof, by cetaceans to 
impulsive noises do not necessarily provide information about long-term 
effects. It is

[[Page 54104]]

not known whether impulsive noises affect reproductive rate or 
distribution and habitat use in subsequent days or years. However, gray 
whales continued to migrate annually along the west coast of North 
America with substantial increases in the population over recent years, 
despite intermittent seismic exploration (and much ship traffic) in 
that area for decades (see Appendix A in Malme et al., 1984; Richardson 
et al., 1995; Angliss and Allen, 2009). The Western Pacific gray whale 
population did not seem affected by a seismic survey in its feeding 
ground during a prior year (Johnson et al., 2007). Bowhead whales have 
continued to travel to the eastern Beaufort Sea each summer, and their 
numbers have increased notably (3.4 percent annually for nearly a 
decade), despite seismic exploration in their summer and autumn range 
for many years (Richardson et al., 1987; Angliss and Allen 2009). In 
any event, brief exposures to sound pulses from the proposed airgun 
source are highly unlikely to result in prolonged effects.
    Toothed Whales--Little systematic information is available about 
reactions of toothed whales to noise pulses. Few studies similar to the 
more extensive baleen whale/seismic pulse work summarized above have 
been reported for toothed whales. However, systematic studies on sperm 
whales have been done (Gordon et al., 2006; Madsen et al., 2006; Winsor 
and Mate, 2006; Jochens et al., 2008; Miller et al., 2009), and there 
is an increasing amount of information about responses of various 
odontocetes to seismic surveys based on monitoring studies (Stone 2003; 
Smultea et al., 2004; Moulton and Miller, 2005; Bain and Williams, 
2006; Holst et al., 2006; Stone and Tasker, 2006; Potter et al., 2007; 
Hauser et al., 2008; Holst and Smultea, 2008; Weir, 2008; Barkaszi et 
al., 2009; Richardson et al., 2009).
    Seismic operators and PSOs on seismic vessels regularly see 
dolphins and other small toothed whales near operating airgun arrays, 
but, in general, there seems to be a tendency for most delphinids to 
show some avoidance of operating seismic vessels (Goold, 1996a,b,c; 
Calambokidis and Osmek, 1998; Stone, 2003; Moulton and Miller, 2005; 
Holst et al., 2006; Stone and Tasker, 2006; Weir, 2008; Richardson et 
al., 2009; see also Barkaszi et al., 2009). Some dolphins seem to be 
attracted to the seismic vessel and floats, and some ride the bow wave 
of the seismic vessel even when large airgun arrays are firing (Moulton 
and Miller, 2005). Nonetheless, there have been indications that small 
toothed whales sometimes tend to head away, or to maintain a somewhat 
greater distance from the vessel, when a large array of airguns is 
operating than when it is silent (Stone and Tasker, 2006; Weir, 2008). 
In most cases, the avoidance radii for delphinids appear to be small, 
on the order of 1 km (0.62 mi) or less, and some individuals show no 
apparent avoidance. The beluga whale (Delphinapterus leucas) is a 
species that (at least at times) shows long-distance avoidance of 
seismic vessels. Aerial surveys conducted during seismic operations in 
the southeastern Beaufort Sea during summer recorded much lower 
sighting rates of beluga whales within 10-20 km (6.2-12.4 mi) compared 
with 20-30 km (12.4-18.6 mi) from an operating airgun array, and 
observers on seismic boats in that area rarely see beluga whales 
(Miller et al., 2005; Harris et al., 2007). However, beluga whales are 
not found in SIO's proposed project area.
    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). The animals tolerated high received levels of sound before 
exhibiting aversive behaviors.
    Most studies of sperm whales exposed to airgun sounds indicate that 
this species shows considerable tolerance of airgun pulses (Stone, 
2003; Moulton et al., 2005, 2006a; Stone and Tasker, 2006; Weir, 2008). 
In most cases the whales do not show strong avoidance and continue to 
call (see Appendix A of the EA for review). However, controlled 
exposure experiments in the Gulf of Mexico indicate that foraging 
effort is somewhat altered upon exposure to airgun sound (Jochens et 
al., 2008; Miller et al., 2009; Tyack, 2009).
    There are almost no specific data on the behavioral reactions of 
beaked whales (Family Ziphiidae) to seismic surveys. However, northern 
bottlenose whales (Hyperoodon ampullatus) continued to produce high-
frequency clicks when exposed to sound pulses from distant seismic 
surveys (Gosselin and Lawson, 2004; Laurinolli and Cochrane, 2005; 
Simard et al., 2005). Most beaked whales tend to avoid approaching 
vessels of other types (Wursig et al., 1998). They may also dive for an 
extended period when approached by a vessel (Kasuya, 1986), although it 
is uncertain how much longer such dives may be as compared to dives by 
undisturbed beaked whales, which also are often quite long (Baird et 
al., 2006; Tyack et al., 2006). In any event, it is likely that most 
beaked whales would also show strong avoidance of an approaching 
seismic vessel, although this has not been documented explicitly.
    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, beluga whales, and harbor porpoises (Appendix A of the EA).
    Additional details on the behavioral reactions (or the lack 
thereof) by all types of marine mammals to seismic vessels can be found 
in Appendix A (5) of the EA.
(4) Hearing Impairment and Other Physical Effects
    Temporary (TTS) or permanent (PTS) hearing impairment is a 
possibility when marine mammals are exposed to very strong sounds. 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 this for marine 
mammals exposed to sequences of airgun pulses.
    Several aspects of the planned monitoring and mitigation measures 
for this project (see the ``Proposed Mitigation'' and ``Proposed 
Monitoring and Reporting'' sections later in this document) are 
designed to detect marine mammals occurring near the airguns to avoid 
exposing them to sound pulses that might, at least in theory, cause 
hearing impairment. In addition, many cetaceans are likely to show some 
avoidance of the area where received levels of airgun sound are high 
enough that hearing impairment could potentially occur. In those cases, 
the avoidance responses of the animals themselves will reduce or (most 
likely) avoid any possibility of hearing impairment.
    Non-auditory physical effects may also occur in marine mammals 
exposed to strong underwater pulsed sound. Possible types of non-
auditory physiological effects or injuries that theoretically might 
occur in mammals close to a strong sound source include stress, 
neurological effects, bubble formation, resonance effects, and other 
types of organ or tissue damage. It is possible that some marine mammal 
species (i.e., beaked whales) may be especially susceptible to injury 
and/or stranding when exposed to strong pulsed sounds. However, as 
discussed later in this document, there is no definitive evidence that 
any of these effects occur even for marine mammals in close proximity 
to large arrays of airguns. It is especially unlikely that any

[[Page 54105]]

effects of these types would occur during the present project given the 
brief duration of exposure for any given individual and the planned 
monitoring and mitigation measures (see the ``Proposed Mitigation'' and 
``Proposed Monitoring and Reporting'' sections later in this document). 
The following subsections discuss in somewhat more detail the 
possibilities of TTS, permanent threshold shift (PTS), and non-auditory 
physical effects.
    Temporary Threshold Shift--TTS is the mildest form of hearing 
impairment that can occur during exposure to a strong sound (Kryter, 
1985). While experiencing TTS, the hearing threshold rises, and a sound 
must be stronger in order to be heard. At least in terrestrial mammals, 
TTS can last from minutes or hours to (in cases of strong TTS) days. 
For sound exposures at or somewhat above the TTS threshold, hearing 
sensitivity in both terrestrial and marine mammals recovers rapidly 
after exposure to the noise ends. Few data on sound levels and 
durations necessary to elicit mild TTS have been obtained for marine 
mammals, and none of the published data concern TTS elicited by 
exposure to multiple pulses of sound. Available data on TTS in marine 
mammals are summarized in Southall et al., (2007). The distances from 
the Melville's airguns at which the received energy level (per pulse, 
flat-weighted) that would be expected to be greater than or equal to 
180 dB re 1 [mu]Pa are estimated in Table 1.
    Given the available data, the received level of a single seismic 
pulse (with no frequency weighting) might need to be approximately 186 
dB re 1 [mu]Pa\2\-s (i.e., 186 dB sound exposure level (SEL) or 
approximately 221-226 dB pk-pk) in order to produce brief, mild TTS. 
Exposure to several strong seismic pulses that each have received 
levels near 190 dB re 1 [mu]Pa (rms) (175-180 dB SEL) 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. Levels 
>=190 dB re 1 [mu]Pa (rms) are expected to be restricted to radii no 
more than 15 m (49.2 ft) from the Melville's GI airguns. For an 
odontocete closer to the surface, the maximum radius with >=190 dB re 1 
[mu]Pa (rms) would be smaller.
    The above TTS information for odontocetes is derived from studies 
on the bottlenose dolphin and beluga whale. There is not published TTS 
information for other species 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., 2009).
    For baleen whales, there are no data, direct or indirect, on levels 
or properties for any sound source required to induce TTS. The 
frequencies to which baleen whales are most sensitive are lower than 
those for odontocetes, and natural background noise levels at those low 
frequencies tend to be higher. Marine mammals can hear sounds at 
varying frequency levels. However, sounds that are produced in the 
frequency range at which an animal hears the best do not need to be as 
loud as sounds in less functional frequencies to be detected by the 
animal. 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), meaning that baleen whales require sounds to 
be louder (i.e., higher dB levels) than odontocetes in the frequency 
ranges at which each group hears the best. From this, it is suspected 
that received levels causing TTS onset may also be higher in baleen 
whales (Southall et al., 2007). Since current NMFS practice assumes the 
same thresholds for the onset of hearing impairment in both odontocetes 
and mysticetes, the threshold is likely conservative for mysticetes. In 
any event, no cases of TTS are expected given two considerations: (1) 
The small size of the GI airgun source (a total discharge volume of 
approximately 90 in\3\ as opposed to arrays of much larger volumes up 
to 6,600 in\3\); and (2) the strong likelihood that baleen whales would 
avoid the approaching airguns (i.e., the vessel) before being exposed 
to levels high enough for TTS to possibly occur (as discussed 
previously in this document).
    As noted above, most cetacean species tend to avoid operating 
airguns, although not all individuals do so. In addition, ramping up 
airgun arrays, which is standard operational protocol for large airgun 
arrays and proposed for the much smaller airgun array for this action, 
should allow cetaceans to move away from the seismic source and avoid 
being exposed to the full acoustic output of the airgun array. Even 
with a large airgun array, it is unlikely that the cetaceans would be 
exposed to airgun pulses at a sufficiently high level for a 
sufficiently long period to cause more than mild TTS, given the 
relative movement of the vessel and the marine mammal. The potential 
for TTS is much lower in this project because of the much smaller 
airgun array proposed to be used. With a large array of airguns, TTS 
would be most likely in any odontocetes that bow-ride or otherwise 
linger near the airguns. While bow-riding, odontocetes would be at or 
above the surface, and thus not exposed to strong pulses given the 
pressure-release effect at the surface. However, bow-riding animals 
generally dive below the surface intermittently. If they did so while 
bow-riding near airguns, they would be exposed to strong sound pulses, 
possibly repeatedly. If some cetaceans did incur TTS through exposure 
to airgun sounds, this would very likely be mild, temporary, and 
reversible.
    To avoid the potential for injury, NMFS has determined that 
cetaceans should not be exposed to pulsed underwater noise at received 
levels exceeding 180 dB re 1 [mu]Pa (rms). As summarized above, data 
that are now available imply that TTS is unlikely to occur unless 
odontocetes (and probably mysticetes as well) are exposed to airgun 
pulses stronger than 180 dB re 1 [mu]Pa (rms).
    Permanent Threshold Shift--When PTS occurs, there is physical 
damage to the sound receptors in the ear. In severe cases, there can be 
total or partial deafness, 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 TTS, there has been further speculation about the 
possibility that some individuals occurring very close to airguns might 
incur PTS (Richardson et al., 1995, Gedamke et al., 2008). Single or 
occasional occurrences of mild TTS are not indicative of permanent 
auditory damage, but repeated or (in some cases) single exposures to a 
level well above that causing TTS onset might elicit PTS.
    Relationships between TTS and PTS thresholds have not been studied 
in marine mammals but are assumed to be similar to those in humans and 
other terrestrial mammals. PTS might occur at a received sound level at 
least several decibels above that inducing mild TTS if the animal were 
exposed to strong sound pulses with rapid rise time (see Appendix A (6) 
of the 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 > 6 dB 
(Southall et al., 2007). On an SEL basis, Southall et al.,

[[Page 54106]]

(2007) estimated that received levels would need to exceed the TTS 
threshold by at least 15 dB for there to be risk of PTS. Thus, for 
cetaceans, Southall et al. estimate that the PTS threshold might be an 
M-weighted SEL (for the sequence of received pulses) of approximately 
198 dB re 1 [mu]Pa\2\-s (15 dB higher than the TTS threshold for an 
impulse).
    Southall et al. (2007) also note that, regardless of the SEL, there 
is concern about the possibility of PTS if a cetacean or pinniped 
receives one or more pulses with peak pressure exceeding 230 or 218 dB 
re 1 [mu]Pa (peak), respectively. A peak pressure of 230 dB re 1 [mu]Pa 
(3.2 bar -m, 0-pk) would only be found within a meter from a GI gun, 
which has a peak pressure of 224.6 dB re 1[mu]Pa-m. 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 near-field around an array of airguns. 
However, no pinnipeds are expected in the proposed survey areas.
    Given the higher level of sound necessary to cause PTS as compared 
with TTS, it is considerably less likely that PTS could occur. Baleen 
whales generally avoid the immediate area around operating seismic 
vessels, as do some other marine mammals.
    Non-auditory Physiological Effects--Non-auditory physiological 
effects or injuries that theoretically might occur in marine mammals 
exposed to strong underwater sound include stress, neurological 
effects, bubble formation, resonance effects, and other types of organ 
or tissue damage (Cox et al., 2006; Southall et al., 2007). 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, little is known about the potential for seismic survey 
sounds to cause auditory impairment or other physical effects in marine 
mammals. Available data suggest that such effects, if they occur at 
all, would presumably be limited to short distances from the sound 
source 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 auditory impairment or non-auditory 
physical effects.
(5) Strandings and Mortality
    Marine mammals close to underwater detonations of high explosives 
can be killed or severely injured, and their auditory organs are 
especially susceptible to injury (Ketten et al., 1993; Ketten, 1995). 
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 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 (Hildebrand, 2005; Southall et al., 2007). Appendix A 
(6) of the EA provides additional details.
    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. 
As noted in SIO's application, some of these mechanisms are unlikely to 
apply in the case of impulse sounds. However, there are increasing 
indications that gas-bubble disease (analogous to ``the bends''), 
induced in super-saturated 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. 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 pulses 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 operate 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 correlation between the effects of military sonar and those of 
seismic surveys on marine mammals. However, evidence that sonar pulses 
can, in special circumstances, lead (at least indirectly) to physical 
damage and mortality (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 based on available data (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\ 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 when 
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 high likelihood that

[[Page 54107]]

any beaked whales nearby would avoid the approaching vessel before 
being exposed to high sound levels, and (2) differences between the 
sound sources operated by SIO and those involved in the naval exercises 
associated with strandings.

Potential Effects of Other Acoustic Devices

(1) Multi-Beam Echosounder Signals
    The Kongsberg EM 122 12-kHz MBES will be operated from the source 
vessel at some times during the planned study. Information about this 
equipment was provided earlier in this document. Any given mammal at 
depth near the trackline would be in the main beam for only one or two 
of the segments. Also, marine mammals that encounter the Kongsberg EM 
122 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 100-ms chirp (or two pulses or 
chirps 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 generally have longer pulse durations than the 
Kongsberg EM 122 and are often directed close to horizontally vs. more 
downward for the MBES. The area of possible influence of the MBES is 
much smaller--a narrow band below the source vessel. The duration of 
exposure for a given marine mammal can be much longer for Navy 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.
    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 echosounder signals (12 
kHz) do not overlap with the predominant frequencies in the calls, 
which would avoid any significant masking.
    Behavioral reactions of free-ranging marine mammals to sonars, 
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 (Globicephala spp.) (Rendell and Gordon, 
1999), and the previously-mentioned beachings by beaked whales. During 
exposure to a 21-25 kHz ``whale-finding'' sonar with a source level of 
215 dB re 1 [mu]Pa-m, gray whales reacted by orienting slightly away 
from the source and being deflected from their course by approximately 
200 m (656.2 ft) (Frankel, 2005). When a 38-kHz echosounder and a 150-
kHz acoustic Doppler current profiler were transmitting during studies 
in the ETP, baleen whales showed no significant responses, while 
spotted (Stenella spp.) and spinner (Stenella longirostris) dolphins 
were detected slightly more often and beaked whales less often during 
visual surveys (Gerrodette and Pettis, 2005).
    Captive bottlenose dolphins and a beluga 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.
    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 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 sonar often use near-horizontally directed sound. Those 
factors would all reduce the sound energy received from the MBES 
relative to that from the sonar used by the Navy.
    As noted earlier in this document, animals are unlikely to be 
exposed to levels that would result in TTS or Level B harassment 
because of the shape of the beam, the duration of the signal, and the 
likelihood that they will be avoiding the vessel at greater horizontal 
distance when airguns are operating.
(2) Sub-Bottom Profiler Signals
    A SBP will be operated from the source vessel during the planned 
study. Details about this equipment were provided earlier in this 
document. The SBP on the Melville has a maximum source level of 211 dB 
re 1 [mu]Pa-m. Kremser et al. (2005) noted that the probability of a 
cetacean swimming through the area of exposure when a bottom profiler 
emits a pulse is small, and--even for an SBP more powerful than those 
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.
    Marine mammal communications will not be masked appreciably by the 
SBP signals given their directionality and the brief period when an 
individual mammal is likely to be within their beams. 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.
    Marine mammal behavioral reactions to other pulsed sound sources 
were discussed previously, 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 SBPs are considerably 
weaker than those from the MBES. Therefore, behavioral responses are 
not expected unless marine mammals are within 10 m of the source, which 
is not expected to occur.
    The source levels of the SBP are much lower than those of the 
airguns. 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. Because of the shape 
of the beams of these sources and their power, NMFS believes it 
unlikely that marine mammals will be exposed to either the MBES or the 
SBP at levels at or above those likely to cause harassment. Further, 
NMFS believes that the brief exposure of cetaceans to a few signals 
from the multi-beam bathymetric sonar

[[Page 54108]]

system is not likely to result in the harassment of marine mammals.
    As stated above, current NMFS practice assumes that the onset of 
Level A harassment corresponds to 180 dB re 1 [mu]Pa (rms) for 
cetaceans. The precautionary nature of these criteria is discussed in 
Appendix A (5) of the supporting EA, including the fact that the 
minimum sound level necessary to cause permanent hearing impairment is 
higher, by a variable and generally unknown amount, than the level that 
induces barely-detectable TTS, and the level associated with the onset 
of TTS is often considered to be a level below which there is no danger 
of permanent damage. NMFS also assumes that cetaceans or pinnipeds 
exposed to levels exceeding 160 dB re 1 [mu]Pa (rms) may experience 
Level B (behavioral) harassment.

Potential Effects on Marine Mammal Habitat

    The proposed SIO seismic survey will not result in any permanent 
impact to habitats used by marine mammals or to their food sources, and 
there will be no physical damage to any habitat. While it is 
anticipated that the specified activity may result in marine mammals 
avoiding certain areas due to temporary ensonification, this impact to 
habitat is temporary and reversible and was considered in further 
detail earlier in this document, as behavioral modification. 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 previously.

Effects on Fish and Invertebrates

    The existing body of information on the impacts of seismic survey 
sound on marine fish and invertebrates is very limited. Furthermore, 
the available information on the impacts of seismic surveys on fish and 
invertebrates 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 problematic because ultimately, the most 
important aspect of potential impacts relates to how exposure to 
seismic survey sound affects populations and their viability, including 
their availability to fisheries. However, there is some unpublished and 
very limited evidence of the potential for adverse effects on fish and 
invertebrates, thereby justifying further discussion and analysis of 
this issue. The three types of potential effects of exposure to seismic 
surveys on fish and marine invertebrates are pathological, 
physiological, and behavioral.
    Pathological effects involve lethal and temporary or permanent 
sublethal 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.
    Based on the physical structure of their sensory organs, marine 
invertebrates appear to be specialized to respond to particle 
displacement components of an impinging sound field and not to the 
pressure component (Popper et al., 2001; see also Appendix D of the 
EA). More details concerning the effects of airguns on fish and 
invertebrates are included in SIO's application and the associated EA. 
In conclusion, NMFS has preliminarily determined that SIO's proposed 
seismic survey operations are not expected to have any habitat-related 
effects that could cause significant or long-term consequences for 
individual marine mammals or on the food sources they utilize.

Proposed Mitigation

    In order to issue an incidental take authorization (ITA) under 
Sections 101(a)(5)(A) and (D) of the MMPA, NMFS must, where applicable, 
set forth the permissible methods of taking pursuant to such activity, 
and other means of effecting the least practicable adverse impact on 
such species or stock and its habitat, paying particular attention to 
rookeries, mating grounds, and areas of similar significance, and on 
the availability of such species or stock for taking for certain 
subsistence uses (where relevant).
    Mitigation and monitoring measures proposed to be implemented for 
the proposed seismic survey have been developed and refined during 
previous SIO seismic studies and associated EAs, IHA applications, and 
IHAs. The mitigation and monitoring measures described herein represent 
a combination of procedures required by past IHAs for other similar 
projects and on best practices recommended in Richardson et al. (1995), 
Pierson et al. (1998), and Weir and Dolman (2007). The measures are 
described in detail below.
    Mitigation measures proposed by SIO for adoption during the 
proposed survey include (1) visual monitoring by protected species 
observers (discussed later in this document), (2) establishment of an 
exclusion zone (EZ), (3) speed or course alteration, provided that 
doing so will not compromise operational safety requirements, (4) GI 
airgun shut down procedures, and (5) ramp-up procedures. Although 
power-down procedures are often standard operating practice for seismic 
surveys, they will not be used here because powering down from two 
airguns to one airgun would make only a small difference in the 180-dB 
safety radius. The difference is not enough to allow continued one-
airgun operations if a mammal came within the safety radius for two 
airguns.
    Exclusion Zones--As discussed previously in this document, NMFS has 
determined that for acoustic effects, using acoustic thresholds in 
combination with corresponding safety radii is an effective way to 
consistently apply measures to avoid or minimize the impacts of an 
action. Thresholds are used to establish a mitigation shut-down, or 
exclusion, zone, i.e., if an animal enters an area calculated to be 
ensonified above the level of an established threshold, a sound source 
is shut down.
    As a matter of past practice and based on the best available 
information at the time regarding the effects of marine sound, NMFS 
estimates that Level A harassment from acoustic sources may occur when 
cetaceans are exposed to levels above 180 dB re 1 [mu]Pa (rms) level. 
NMFS also considers 160 dB re 1 [mu]Pa (rms) as the criterion for 
estimating the onset of Level B harassment from acoustic sources 
producing impulse sounds, as in this seismic survey.
    Empirical data concerning the 180- and 160-dB distances have been 
acquired based on measurements during the acoustic verification study 
conducted by L-DEO in the northern Gulf of Mexico from May 27-June 3, 
2003 (Tolstoy et al., 2004). The empirical data indicate that, for this 
survey, the assumed 180- and 160-dB radii are 40 m (131.2 ft) and 400 m 
(1312.3 ft), respectively (see Table 1 in this document).
    Speed or Course Alteration--If a marine mammal is detected outside 
the EZ but is likely to enter it based on relative movement of the 
vessel and the animal, and if safety and scientific objectives allow, 
the vessel speed and/

[[Page 54109]]

or course will be adjusted to minimize the likelihood of the animal 
entering the EZ. In the event that safety and/or scientific objectives 
do not allow for alteration of speed and/or course as a needed 
mitigation measure, shut-down procedures will still be utilized (see 
below). 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 a small source and short streamers will be 
used.
    Shut-down Procedures--If a marine mammal is detected by PSOs 
outside the EZ but is likely to enter the EZ, and if the vessel's speed 
and/or course cannot be changed to avoid having the animal enter the 
EZ, the airgun array, MBES, and SBP will be shut down before the animal 
is within the EZ. Likewise, if a marine mammal is already within the EZ 
when first detected, the airgun array, MBES, and SBP will be shut down 
immediately. Following a shut down, seismic activity will not resume 
until the marine mammal has cleared the EZ. The animal will be 
considered to have cleared the EZ if it (a) is visually observed to 
have left the EZ, or (b) has not been seen within the EZ for 15 min in 
the case of small odontocetes, or has not been seen within the EZ for 
30 min in the case of mysticetes and large odontocetes, including sperm 
and beaked whales.
    Ramp-up Procedures--A ramp-up procedure will be followed when the 
GI airguns begin operating after a specified period without GI airgun 
operations. It is proposed that, for the present cruise, this period 
would be approximately 1-2 min. This period is based on the 180-dB 
radii for the GI airguns (see Table 1 in this document) in relation to 
the planned speed of the Melville while shooting. Ramp-up will begin 
with a single GI airgun (45 in\3\). The second GI airgun (45 in\3\) 
will be added after 5 min. During ramp up, the PSOs will monitor the 
exclusion zone, and, if marine mammals are sighted, a shut-down will be 
implemented as though both GI airguns were operational.
    If the complete EZ has not been visible for at least 30 min prior 
to the start of operations in either daylight or nighttime, ramp-up 
will not commence. If one GI airgun has operated, ramp-up to full power 
will be permissible at night or in poor visibility on the assumption 
that marine mammals will be alerted to the approaching seismic vessel 
by the sounds from the single GI airgun and could move away if they 
choose. A ramp-up from a shut-down may occur at night, but only when 
the entire EZ is visible, and it has been determined from the pre-ramp 
up watch that the EZ is clear of marine mammals. Ramp-up of the GI 
airguns will not be initiated if a marine mammal is sighted within or 
near the applicable EZ during day or night.
    NMFS has carefully evaluated the applicant's proposed mitigation 
measures and considered a range of other measures in the context of 
ensuring that NMFS prescribes the means of effecting the least 
practicable impact on the affected marine mammal species and stocks and 
their habitat. Our evaluation of potential measures included 
consideration of the following factors in relation to one another:
     The manner in which, and the degree to which, the 
successful implementation of the measure is expected to minimize 
adverse impacts to marine mammals;
     The proven or likely efficacy of the specific measure to 
minimize adverse impacts as planned; and
     The practicability of the measure for applicant 
implementation.
    Based on our evaluation of the applicant's proposed measures, as 
well as other measures considered by NMFS, NMFS has preliminarily 
determined that the proposed mitigation measures provide the means of 
effecting the least practicable impact on marine mammal species or 
stocks and their habitat, paying particular attention to rookeries, 
mating grounds, and areas of similar significance.

Proposed Monitoring and Reporting

    In order to issue an ITA for an activity, Section 101(a)(5)(D) of 
the MMPA states that NMFS must set forth ``requirements pertaining to 
the monitoring and reporting of such taking''. The MMPA implementing 
regulations at 50 CFR 216.104(a)(13) indicate that requests for ITAs 
must include the suggested means of accomplishing the necessary 
monitoring and reporting that will result in increased knowledge of the 
species and of the level of taking or impacts on populations of marine 
mammals that are expected to be present in the proposed action area.
    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 IHA. SIO's proposed Monitoring Plan is described 
next. The monitoring work described here has been planned as a self-
contained project independent of any other related monitoring projects 
that may be occurring simultaneously in the same regions. SIO is 
prepared to discuss coordination of its monitoring program with any 
related work that might be done by other groups insofar as this is 
practical and desirable.

Vessel-based Visual Monitoring

    Three protected species observers (PSOs) will be based aboard the 
seismic source vessel for the duration of the cruise and will watch for 
marine mammals near the vessel during daytime airgun operations and 
during start-up of airguns at any time. Watches will be conducted by at 
least one observer 100% of the time during seismic surveys in daylight 
hours. Daylight observation by at least one observer will continue 
during non-seismic periods, as long as weather conditions make 
observations meaningful, for comparison of sighting rates and animal 
behavior during periods with vs. without airgun operations. PSOs will 
be appointed by SIO with NMFS concurrence after a review of their 
qualifications.
    The Melville is a suitable platform for marine mammal observations. 
The observer platform is located one deck below and forward of the 
bridge (12.46 meters (40.88 ft) above the waterline), affording a 
relatively unobstructed 180-degree forward view. Aft views can be 
obtained along the port and starboard decks. During daytime hours, the 
observer(s) will scan the area systematically using reticulated 25x150 
big-eye binoculars and 7x50 hand-held binoculars to determine bearing 
and distance of sightings. A clinometer is used to determine distances 
of animals in close proximity to the vessel. Hand-held fixed 
rangefinders and distance marks on the ship's side rails are used to 
measure the exact location of the safety zone. Laser rangefinders, 
which have proven to be less reliable for open water sighting, are also 
provided. During darkness, night-vision equipment will be available. 
The PSOs 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 GI airgun 
shut down.
    Before commencing seismic operations during daylight hours, two 
observers will maintain a 360-degree watch for all marine mammals for 
at least 30 minutes prior to the start of seismic operations after an 
extended shutdown of the airguns (1-2 minutes, depending on vessel 
speed). If no marine mammals are observed within the EZ during this 
time, the observers will notify the seismic personnel of an ``all 
clear'' status. Watch periods are scheduled as a 2-hour rotation. The

[[Page 54110]]

observers continually scan the water from the horizon to the ship's 
hull, and forward of 90 degrees from the port and starboard beams. 
Based on PSO observations, the GI airgun will be shut down (as 
described earlier in this document) when marine mammals are detected 
within or about to enter a designated EZ that corresponds to the 180-dB 
re 1 [micro]Pa (rms) isopleths. The PSOs will continue to maintain 
watch to determine when the animal(s) are outside the EZ, and airgun 
operations will not resume until the animal has left that EZ. The 
predicted distance for the 180-dB EZ is listed in Table 1 earlier in 
this document. Seismic operations will resume only after the animals 
are seen to exit the safety radius or after no further visual detection 
of the animal for 15 minutes (for small odontocetes and pinnipeds) or 
30 minutes (for mysticetes and large odontocetes, including beaked 
whales).
    The bridge officers and other crew will be instructed to alert the 
observer on watch of any suspected marine mammal sighting. If needed, 
the bridge will be contacted in order to maneuver the ship to avoid 
interception with approaching marine mammals.

PSO Data and Documentation

    PSOs will record data to estimate the numbers of marine mammals 
exposed to various received sound levels and to document 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 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; and
     Time, location, heading, speed, activity of the vessel, 
sea state, visibility, cloud cover, and sun glare.

The data 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 collection 
procedures are adapted from the line-transect protocols developed by 
the SWFSC for their marine mammal abundance research cruises. A laptop 
computer is located on the observer platform for ease of data entry. 
The computer is connected to the ship's Global Positioning System, 
which allows a record of time and position to be made at 3-minute 
intervals and for each event entered (such as sightings, weather 
updates and effort changes). Data accuracy will be verified by the PSOs 
at sea and preliminary reports will be prepared during the field 
program and summaries forwarded to the SIO's shore facility and to NSF 
weekly or more frequently. PSO observations will provide the following 
information:
     The basis for decisions about shutting down the airgun 
arrays;
     Information needed to estimate the number of marine 
mammals potentially `taken by harassment', which will be reported to 
NMFS;
     Data on the occurrence, distribution, and activities of 
marine mammals in the area where the seismic study is conducted; and
     Data on the behavior and movement patterns of marine 
mammals 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 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 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) will be reported to NMFS as soon as practicable. 
The 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.
Estimated Takes by Incidental Harassment
    With respect to the activities described 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].

    All anticipated takes would be by Level B harassment, involving 
temporary changes in behavior. The proposed mitigation and monitoring 
measures are expected to minimize the possibility of injurious or 
lethal takes such that take by Level A harassment, serious injury or 
mortality is considered remote. However, as noted earlier, there is no 
specific information demonstrating that injurious or lethal ``takes'' 
would occur even in the absence of the planned mitigation and 
monitoring measures. The sections here describe methods to estimate 
``take by Level B harassment'' and present estimates of the numbers of 
marine mammals that might be affected during the proposed seismic 
program. The estimates of ``take'' are based on data collected in the 
ETP by NMFS SWFSC during 12 ship-based cetacean and ecosystem 
assessment surveys conducted during July-December from 1986-2006.
    It is assumed that, during simultaneous operations of the seismic 
sources and the other sources, any marine mammals close enough to be 
affected by the MBES or SBP would already be affected by the seismic 
sources. However, whether or not the seismic sources are operating 
simultaneously with the other sources, marine mammals are expected to 
exhibit no more than short-term and inconsequential responses to the 
MBES and SBP given their characteristics (e.g., narrow downward-
directed beam) and other considerations described above, such as the 
unlikelihood of being exposed to the source at higher levels and the 
fact that it would likely only be for one or two pulses. Such reactions 
are not considered to constitute ``taking'' (NMFS, 2001). Therefore, no 
additional allowance is included for animals that might be affected by 
sound sources other than the seismic sources (i.e., air guns).
    Extensive systematic ship-based surveys have been conducted by NMFS 
SWFSC for marine mammals in the ETP. SWFSC has recently developed 
habitat modeling as a method to estimate cetacean densities on a finer 
spatial scale than traditional line-transect analyses by using a 
continuous function of habitat variables, e.g., sea surface 
temperature, depth, distance from shore, and prey density (Barlow et 
al., 2009). The models have been incorporated into a Web-based 
Geographic Information System (GIS) developed by Duke University's 
Department of Defense Strategic Environmental Research and Development 
Program (SERDP) team in close collaboration with the SWFSC SERDP team 
(Read et al., 2009). The GIS was used to obtain densities for the 11

[[Page 54111]]

cetaceans in the model (Bryde's whale, blue whale, Kogia spp., 
Mesoplodon spp., rough-toothed, bottlenose, pantropical spotted, 
spinner, striped, and short-beaked common dolphins, and short-finned 
pilot whale) in each of eight areas: the four proposed survey areas 
(see Figure 1 in SIO's application), and corridors 1[deg] wide and 
centered on the tracklines between the survey areas and from the 
southernmost survey area to the EEZ of Peru. For species sighted in 
SWFSC surveys whose sample sizes were too small to model density (sperm 
whale, humpback whale, Cuvier's beaked whale, Fraser's dolphin, Risso's 
dolphin, melon-headed, pygmy killer, false killer, and killer whales), 
SIO used densities from the surveys conducted during summer and fall 
1986-1996, as summarized by Ferguson and Barlow (2001). Densities were 
calculated from Ferguson and Barlow (2003) for 5[deg] x 5[deg] blocks 
that include the proposed survey areas and corridors. Those blocks 
included 27,275 km (16,947.9 mi) of survey effort in Beaufort sea 
states 0-5 and 2564 km (1593.2 mi) of survey effort in Beaufort sea 
states 0-2. Densities were obtained for an additional eight species 
that were sighted in one or more of those blocks.
    Oceanographic conditions, including occasional El Nino and La Nina 
events, influence the distribution and numbers of marine mammals 
present in the ETP, resulting in considerable year-to-year variation in 
the distribution and abundance of many marine mammal species (Escorza-
Trevino, 2009). Thus, for some species, the densities derived from 
recent surveys (see Table 2 of this document) may not be representative 
of the densities that will be encountered during the proposed seismic 
survey.
    Table 3 in SIO's application gives the average (or ``best'') and 
maximum densities for each species of cetacean likely to occur in the 
study area, i.e., species for which densities were obtained or 
assigned. These densities have been corrected for both detectability 
and availability bias by the study authors. Detectability bias is 
associated with diminishing sightability with increasing lateral 
distance from the trackline. Availability bias refers to the fact that 
there is less than 100 percent probability of sighting an animal that 
is present along the survey trackline.
    The estimated numbers of individuals potentially exposed are 
presented next based on the 160-dB re 1 [mu]Pa (rms) Level B harassment 
criterion for all cetaceans. It is assumed that marine mammals exposed 
to airgun sounds at that level might change their behavior sufficiently 
to be considered ``taken by harassment''.
    It should be noted that the following estimates of ``takes by 
harassment'' assume that the surveys will be undertaken and completed; 
in fact, the planned number of line-kilometers has been increased to 
accommodate lines that may need to be repeated, equipment testing, etc. 
As is typical on offshore 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 
EZ will result in the shutdown of seismic operations as a mitigation 
measure. Thus, the following estimates of the numbers of marine mammals 
potentially exposed to 160-dB re 1 [mu]Pa (rms) sounds are 
precautionary and probably overestimate the actual numbers of marine 
mammals that might be taken. These estimates assume that there will be 
no weather, equipment, or mitigation delays, which is highly unlikely.
    There is some uncertainty about the representativeness of the data 
and the assumptions used in the calculations presented here. However, 
the approach used here is believed to be the best available approach. 
Also, to provide some allowance for these uncertainties, ``maximum 
estimates'' as well as ``best estimates'' of the densities present and 
numbers potentially affected have been derived. Best estimates of 
density are the mean densities weighted by effort in the eight survey 
areas or corridors from Read et al. (2009) or the nine 5[deg] x 5[deg] 
blocks from Ferguson and Barlow (2001, 2003), whereas maximum estimates 
of density are the highest densities in any of those survey areas/
corridors or blocks.
    The number of different individuals that may be exposed to GI 
airgun sounds with received levels >=160 dB re 1 [mu]Pa (rms) on one or 
more occasions was estimated by considering the total marine area that 
would be within the 160-dB radius around the operating airgun array on 
at least one occasion, along with the expected density of animals in 
the area. The proposed seismic lines do not run parallel to each other 
in close proximity, which minimizes the number of times an individual 
mammal may be exposed during the survey; in this case, an individual 
could be exposed 1.01 times on average. The numbers of different 
individuals potentially exposed to >=160 dB re 1 [mu]Pa (rms) were 
calculated by multiplying the expected species density, either ``mean'' 
(i.e., best estimate) or ``maximum'', times the anticipated area to be 
ensonified to that level during GI airgun operations.
    The area expected to be ensonified was determined by entering the 
planned survey lines into a MapInfo GIS, using the GIS to identify the 
relevant areas by ``drawing'' the applicable 160-dB buffer (see Table 1 
in this document) around each seismic line, and then calculating the 
total area within the buffers. Areas where overlap occurred (because of 
intersecting lines) were included only once when estimating the number 
of individuals exposed.
    Applying the approach described here, approximately 4340 km\2\ 
(1675.7 mi\2\) would be within the 160-dB isopleth on one or more 
occasions during the surveys. This approach does not allow for turnover 
in the mammal populations in the study area during the course of the 
survey. That might underestimate actual numbers of individuals exposed, 
although the conservative distances used to calculate the area may 
offset this. In addition, the approach assumes that no cetaceans will 
move away or toward the trackline as the Melville approaches in 
response to increasing sound levels prior to the time the levels reach 
160 dB. Another way of interpreting the estimates that follow (Table 3 
in this document) is that they represent the number of individuals that 
are expected (in the absence of a seismic program) to occur in the 
waters that will be exposed to >=160 dB re 1 [mu]Pa (rms). The take 
estimates presented here do not take the proposed mitigation measures 
into consideration and thus are likely to be overestimates.

[[Page 54112]]



 Table 3--The Estimates of the Possible Numbers of Marine Mammals Exposed to Sound Levels Greater Than or Equal
    to 160 dB During SIO's Proposed Seismic Survey in the Eastern Tropical Pacific Ocean in Oct-Nov 2010. The
 Proposed Sound Source Is a Pair of GI Airguns. Received Levels Are Expressed in dB re 1 [mu]Pa (rms) (Averaged
  Over Pulse Duration), Consistent With NMFS' Practice. Not All Marine Mammals Will Change Their Behavior When
        Exposed to These Sound Levels, But Some May Alter Their Behavior When Levels Are Lower (See Text)
                            [See Tables 2-4 in SIO's Application for Further Detail]
----------------------------------------------------------------------------------------------------------------
                                              Number of         Number of         Approx. %
                                             individuals       individuals        regional       Requested take
                 Species                   exposed (best)     exposed (max)      population       authorization
                                                 \1\               \1\           (best) \2\
----------------------------------------------------------------------------------------------------------------
Mysticetes:
    Bryde's whale, (Balaenoptera edeni).                 3                 6              0.02                 3
    Blue whale, (Balaenoptera musculus).                 1                 1              0.05               * 2
    Humpback whale, (Megaptera                           1                 1            \3\ NA               * 2
     novaeangliae)......................
Odontocetes:
    Sperm whale, (Physeter                              23                82              0.09                23
     macrocephalus).....................
    Cuvier's beaked whale, (Ziphius                     10                20              0.05                10
     cavirostris).......................
    Mesoplodon sp. (unidentified).......                 1                 2             <0.01                 1
    Rough-toothed dolphin, (Steno                        9                13              0.01              * 15
     bredanensis).......................
    Pantropical spotted dolphin,                        67               122              0.01             * 131
     (Stenella attenuata)...............
    Spinner dolphin, (Stenella                          21                31             <0.01             * 109
     longirostris)......................
    Bottlenose dolphin, (Tursiops                       82               125              0.02                82
     truncatus).........................
    Striped dolphin, (Stenella                           6               291             <0.01                 6
     coeruleoalba)......................
    Fraser's dolphin, (Lagenodelphis                     6                30             <0.01             * 440
     hosei).............................
    Short-beaked common dolphin,                       777              1317              0.02               777
     (Delphinus delphis)................
    Pygmy killer whale, (Feresa                          3                10              0.01              * 30
     attenuata).........................
    Melon-headed whale, (Peponocephala                  15                50              0.03             * 258
     electra)...........................
    Risso's dolphin, (Grampus griseus)..                55               203              0.05                55
    False killer whale, (Pseudorca                       2                11              0.01              * 11
     crassidens)........................
    Killer whale, (Orcinus orca)........                 5                22              0.05                 5
    Short-finned pilot whale,                           34                64              0.01                34
     (Globicephala macrorhynchus).......
----------------------------------------------------------------------------------------------------------------
* Requested take authorization increased from `best' exposure estimate to mean group size as reported in
  Ferguson et al. (2006).
\1\ Best estimate and maximum estimate density are from Table 3 of SIO's application; therefore, takes are not
  anticipated for sei, fin, humpback, minke, Longman's beaked whales, pygmy sperm whales, and dwarf sperm
  whales. Humpback whale estimates calculated independently using methodology described previously.
\2\ Regional population size estimates are from Table 2 in this document.
\3\ Southern Hemisphere population sizes are poorly understood. However, the number of individuals potentially
  exposed is low relative to regional population.

    Table 4 in SIO's application shows the best and maximum estimates 
of the number of exposures and the number of individual marine mammals 
that potentially could be exposed to >=160 dB re 1 [mu]Pa (rms) during 
the seismic survey if no animals moved away from the survey vessel. 
Proposed take authorizations are based on best estimates, calculated 
according to the methodology described previously. The best estimate of 
the number of individual cetaceans that could be exposed to seismic 
sounds with received levels >=160 dB re 1 [mu]Pa (rms) (but below Level 
A harassment thresholds) during the survey is shown in Table 4 of SIO's 
application and Table 3 here. That total includes 25 endangered whales: 
1 blue whale (0.05% of the regional population), 1 humpback whale, and 
23 sperm whales (0.09%). Percentage of regional population for humpback 
whale is not listed because Southern Hemisphere population numbers are 
poorly understood; however, the authorized take is low compared to 
regional population. It should be noted that the applicant did not 
initially request take authorization for humpback whales, believing 
that migrating individuals would depart the proposed study area prior 
to the activity dates. In subsequent discussions between NMFS and the 
applicant, it was agreed that there was some reasonable chance that 
late-migrant Southern Hemisphere individuals could be present in one or 
more of the study areas. The proposed take authorization for humpback 
whales reflects this decision. Most (96.8%) of the cetaceans 
potentially exposed are delphinids; short-beaked common, pantropical 
spotted, bottlenose, and Risso's dolphins and short-finned pilot whales 
are estimated to be the most common species in the area, with best 
estimates of 777 (0.02% of the regional population), 67 (0.01%), 82 
(0.02%), 55 (0.05%), and 34 (0.01%) exposed to >=160 dB re 1 [mu]Pa 
(rms), respectively. For certain species where the calculated number of 
individuals exposed was between 1 and the mean group size, the 
requested take authorization has been increased to the mean group size 
as observed in the ETP (Ferguson et al., 2006).

Negligible Impact and Small Numbers Analysis and Preliminary 
Determination

    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.'' In making a negligible impact determination, 
NMFS considers a variety of factors, including but not limited to: (1) 
The number of anticipated mortalities; (2) the number and nature of 
anticipated injuries; (3) the number, nature, intensity, and duration 
of Level B harassment; and (4) the context in which the take occurs.
    NMFS has preliminarily determined that the impact of conducting the 
low-energy marine seismic survey in the ETP may result, at worst, in a 
temporary modification in behavior (Level B harassment) of small 
numbers of marine mammals. No mortality or injuries are

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anticipated as a result of the specified activity, and none are 
proposed to be authorized. Additionally, animals in the area are not 
expected to incur hearing impairment (i.e., TTS or PTS) or non-auditory 
physiological effects. Due to the nature, degree, and context of 
behavioral harassment anticipated, the activity is not expected to 
impact rates of recruitment or survival. This activity is expected to 
result in a negligible impact on the affected species or stocks.
    Many animals perform vital functions, such as feeding, resting, 
traveling, and socializing, on a diel cycle (24-hr cycle). Behavioral 
reactions to noise exposure (such as disruption of critical life 
functions, displacement, or avoidance of important habitat) are more 
likely to be significant if they last more than one diel cycle or recur 
on subsequent days (Southall et al., 2007). Consequently, a behavioral 
response lasting less than one day and not recurring on subsequent days 
is not considered particularly severe unless it could directly affect 
reproduction or survival (Southall et al., 2007). Seismic operations 
are only scheduled to occur at each site for approximately 2 days. 
Additionally, the source vessel will be constantly moving and will not 
remain in any one spot for a prolonged period of time. Survey 
operations will be conducted solely in deep-water areas of no 
specifically-known (e.g., breeding) importance for the species 
described.
    Several species for which take authorization is requested are 
either ESA-listed and/or are considered ``Depleted'' under the MMPA. 
Blue, sperm, and humpback whales are listed as Endangered under the ESA 
(as well as MMPA-Depleted). Along the California coast blue whale 
abundance has been increasing during the past two decades (Calambokidis 
et al., 1990; Barlow, 1994; Calambokidis, 1995). Though the magnitude 
of this apparent increase is too large to be accounted for by 
population growth alone and, therefore, is assumed to partly result 
from a shift in distribution, there is an apparent increasing trend. 
Some individuals from this stock may be present year-round on the Costa 
Rica Dome (Reilly and Thayer, 1990). Although the population in the 
North Pacific is expected to have grown since being given protected 
status in 1966, there is no evidence showing that the eastern North 
Pacific stock is currently growing, and no information exists on the 
rate of growth of blue whale populations in the Pacific (Best, 1993). 
Slightly more information is available for sperm whales, and it has 
been suggested that ETP animals of this species may form a distinct 
stock (Dufault and Whitehead 1995; Jaquet et al., 2003). However, 
little is known about population trends and growth rates in the survey 
area. Again, populations are assumed to have increased since the 
species gained protection. Humpback whales potentially seen in the 
survey area would likely be late migrant individuals belonging to 
Southern Hemisphere stocks, where the International Whaling Commission 
has designated seven major breeding stocks linked to seven major 
feeding areas. In most areas for which there are good data, humpback 
whales have shown evidence of strong recovery towards their unexploited 
size, with annual increase rates of about 10% being recorded in a 
number of areas including off South America. The total Southern 
Hemisphere abundance is probably at least 60,000, although little data 
on which to base this number exists. The eastern spinner dolphin (S. l. 
orientalis), considered an offshore species and common in the survey 
area, is considered a Depleted stock under the MMPA. The long-term 
trend is flat for this stock. For all of these species, the levels of 
requested take are small relative to the regional population (see Table 
3 in this document).
    For reasons stated previously in this document, the negligible 
impact determination is also supported by 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; the fact that cetaceans 
would have to be closer than 40 m (131.2 ft) in deep water when the GI 
airgun is in use from the vessel to be exposed to levels of sound (180 
dB) believed to have even a minimal chance of causing PTS; and the 
likelihood that marine mammal detection ability by trained observers is 
high at that short distance from the vessel, enabling the 
implementation of shut-downs to avoid injury, serious injury, or 
mortality. 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 incidentally 
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 one percent of 
any of the estimated population sizes, and has been mitigated to the 
lowest level practicable through incorporation of the proposed 
mitigation and monitoring measures mentioned previously in this 
document.
    Based on the analysis contained herein of the likely effects of the 
specified activity on marine mammals and their habitat, and taking into 
consideration the implementation of the mitigation and monitoring 
measures, NMFS preliminarily finds that the proposed SIO seismic survey 
will result in the incidental take of small numbers of marine mammal, 
by Level B harassment only, and that the total taking from the seismic 
survey will have a negligible impact on the affected species or stocks.

Impact on Availability of Affected Species or Stock for Taking for 
Subsistence Uses

    Subsistence whaling of several species of small cetaceans, 
including the bottlenose dolphin, takes place in territorial coastal 
waters of Peru (Read et al., 1998). This hunt is mainly for human 
consumption and uses gill nets, purse seines, and harpoons. Read et al. 
(1998) estimated that approximately 10,000 dolphins and porpoises were 
landed in Peru in 1985. Because the seismic surveys are in offshore 
waters, the proposed activities will not have any impact on the 
availability of the species or stocks for subsistence users. However, 
there are no relevant subsistence uses of marine mammals implicated by 
this action.

Endangered Species Act (ESA)

    There are six marine mammal species that are listed as endangered 
under the ESA with confirmed or possible occurrence in the study area: 
The humpback whale, South Pacific right whale, sei whale, fin whale, 
blue whale, and sperm whale. Under section 7 of the ESA, SIO has begun 
consultation with NMFS on the proposed seismic survey. NMFS will also 
consult internally on the issuance of an IHA under section 101(a)(5)(D) 
of the MMPA for this activity. As discussed previously in this 
document, take is requested only for species likely to occur in the 
survey area during the project timeframe (blue, humpback, and sperm 
whales), and consultation will consider these three species. 
Consultation will be concluded prior to a determination on the issuance 
of an IHA.

National Environmental Policy Act (NEPA)

    On behalf of NSF, LGL Limited, Environmental Research Associates, 
prepared an EA titled ``Environmental Assessment of a Marine 
Geophysical Survey by the R/V Melville in the Pacific

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Ocean off Central and South America, October-November 2010''. NMFS, 
after independently reviewing and evaluating the document for 
sufficiency and compliance with the Council on Environmental Quality 
regulations and NOAA Administrative Order 216-6, will either adopt 
NSF's EA or conduct a separate NEPA analysis, as necessary, prior to 
making a determination on the issuance of the IHA.

Proposed Authorization

    As a result of these preliminary determinations, NMFS proposes to 
issue an IHA for Level B harassment, at levels specified in Table 3 of 
this document, to SIO incidental to conducting a low-energy marine 
seismic survey in the ETP during the period October-November 2010, 
provided the previously mentioned mitigation, monitoring, and reporting 
requirements are incorporated.

    Dated: August 30, 2010.
James H. Lecky,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. 2010-22080 Filed 9-2-10; 8:45 am]
BILLING CODE 3510-22-P