[Federal Register Volume 76, Number 24 (Friday, February 4, 2011)]
[Notices]
[Pages 6430-6448]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-2538]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XA124


Takes of Marine Mammals Incidental to Specified Activities; 
Marine Geophysical Survey in the Pacific Ocean off Costa Rica, April 
Through May, 2011

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 Lamont-Doherty Earth 
Observatory (L-DEO), a part of Columbia University, for an Incidental 
Harassment Authorization (IHA) to take marine mammals, by harassment, 
incidental to conducting a marine geophysical survey in the eastern 
tropical Pacific (ETP) Ocean off Costa Rica, April through May, 2011. 
Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting 
comments on its proposal to issue an IHA to L-DEO to incidentally 
harass, by Level B harassment only, 19 species of marine mammals during 
the specified activity.

DATES: Comments and information must be received no later than March 7, 
2011.

ADDRESSES: Comments on the application should be addressed to P. 
Michael Payne, Chief, Permits, Conservation and Education Division, 
Office of Protected Resources, National Marine Fisheries Service, 1315 
East-West Highway, Silver Spring, MD 20910. 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.
    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#applications 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 above address, 
telephoning the

[[Page 6431]]

contact listed here (see FOR FURTHER INFORMATION CONTACT) or visiting 
the Internet at: http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications.
    The National Science Foundation (NSF), which is providing funding 
for the proposed action, has prepared a draft Environmental Analysis 
which incorporates an ``Environmental Assessment of a Marine 
Geophysical Survey by the R/V Marcus G. Langseth in the Pacific Ocean 
off Costa Rica, April-May, 2011'', prepared by LGL Limited, on behalf 
of NSF is also available at the same internet address. Documents cited 
in this notice may be viewed, by appointment, during regular business 
hours, at the aforementioned address.

FOR FURTHER INFORMATION CONTACT: Jeannine Cody, Office of Protected 
Resources, NMFS, (301) 713-2289, ext. 113.

SUPPLEMENTARY INFORMATION:

Background

    Section 101(a)(5)(D) of the MMPA (16 U.S.C. 1371(a)(5)(D)) directs 
the Secretary of Commerce to authorize, upon request, the incidental, 
but not intentional, taking of small numbers of marine mammals of a 
species or population stock, by United States citizens who engage in a 
specified activity (other than commercial fishing) within a specified 
geographical region if certain findings are made and, if the taking is 
limited to harassment, a notice of a proposed authorization is provided 
to the public for review.
    Authorization for the incidental taking of small numbers of marine 
mammals shall be granted if NMFS finds that the taking will have a 
negligible impact on the species or stock(s), and will not have an 
unmitigable adverse impact on the availability of the species or 
stock(s) for subsistence uses (where relevant). The authorization must 
set forth the permissible methods of taking, other means of effecting 
the least practicable adverse impact on the species or stock and its 
habitat, and requirements pertaining to the mitigation, monitoring and 
reporting of such takings. NMFS has defined ``negligible impact'' in 50 
CFR 216.103 as ``* * * an impact resulting from the specified activity 
that cannot be reasonably expected to, and is not reasonably likely to, 
adversely affect the species or stock through effects on annual rates 
of recruitment or survival.''
    Section 101(a)(5)(D) of the MMPA established an expedited process 
by which citizens of the United States can apply for an authorization 
to incidentally take small numbers of marine mammals by harassment. 
Section 101(a)(5)(D) of the MMPA establishes a 45-day time limit for 
NMFS' review of an application followed by a 30-day public notice and 
comment period on any proposed authorizations for the incidental 
harassment of small numbers of marine mammals. Within 45 days of the 
close of the public 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 November 12, 2010, from L-DEO for 
the taking by harassment, of marine mammals, incidental to conducting a 
marine geophysical survey in the eastern tropical Pacific Ocean within 
the Exclusive Economic Zone (EEZ) of Costa Rica. L-DEO, with research 
funding from the U.S. National Science Foundation (NSF), plans to 
conduct the proposed survey from April 7, 2011, through May 9, 2011. 
Upon receipt of additional information, NMFS determined the application 
complete and adequate on January 4, 2011.
    L-DEO plans to use one source vessel, the R/V Marcus G. Langseth 
(Langseth) and a seismic airgun array to image the structures along a 
major plate-boundary fault off in the ETP off Costa Rica using three-
dimensional (3-D) seismic reflection techniques. L-DEO will use the 3-D 
seismic reflection data to determine the fault structure and the 
properties of the rocks that lie along the fault zone. In addition to 
the proposed operations of the seismic airgun array, L-DEO intends to 
operate a multibeam echosounder (MBES) and a sub-bottom profiler (SBP) 
continuously throughout the survey.
    Acoustic stimuli (i.e., increased underwater sound) generated 
during the operation of the seismic airgun array, may have the 
potential to cause a short-term behavioral disturbance for marine 
mammals in the survey area. This is the principal means of marine 
mammal taking associated with these activities and L-DEO has requested 
an authorization to take 19 species marine mammals by Level B 
harassment. Take is not expected to result from the use of the MBES or 
SBP, for reasons discussed in this notice; nor is take expected to 
result from collision with the vessel because it is a single vessel 
moving at a relatively slow speed during seismic acquisition within the 
survey, for a relatively short period of time (approximately 32 days). 
It is likely that any marine mammal would be able to avoid the vessel.

Description of the Specified Activity

    L-DEO's proposed seismic survey in the ETP off Costa Rica is 
scheduled to commence on April 7, 2011 and continue for approximately 
32 days ending on May 9, 2011. L-DEO will operate the Langseth to 
deploy a seismic airgun array and hydrophone streamers to complete the 
survey.
    The Langseth will depart from Caldera, Costa Rica on April 7, 2011 
and transit to the survey area offshore from Costa Rica. Some minor 
deviation from these dates is possible, depending on logistics, weather 
conditions, and the need to repeat some lines if data quality is 
substandard. Therefore, NMFS plans to issue an authorization that 
extends to June 6, 2011.
    Geophysical survey activities will involve 3-D seismic 
methodologies to determine the fault structure and the properties of 
the rocks that lie along the fault zone and to assess the property 
changes along the fault and determine where the large stress 
accumulations that lead to large earthquakes occur along the fault 
zone.
    To obtain 3-D images of the fault zone which lies two to nine 
kilometers (km) below the seafloor, the Langseth will deploy a two-
string subarray of nine airguns each as an energy source. The identical 
subarrays will fire alternately, so that no more than 18 airguns will 
fire at any time during the proposed survey. The receiving system will 
consist of four 6-km-long hydrophone streamers. As the airgun subarrays 
are towed along the survey lines, the hydrophone streamers will receive 
the returning acoustic signals and transfer the data to the on-board 
processing system. L-DEO also plans to use two or three small fishing 
vessels around the Langseth to ensure that other vessels do not 
entangle the streamers.
    The proposed study (e.g., equipment testing, startup, line changes, 
repeat coverage of any areas, and equipment recovery) will take place 
in the EEZ of Costa Rica in water depths ranging from less than 100 
meters (m) (328 feet (ft)) to greater than 2,500 m (1.55 miles (mi)). 
The survey will require approximately 32 days (d) to complete 
approximately 19 transects in a racetrack configuration

[[Page 6432]]

that will cover an area of approximately 57 x 12 km (35.4 x 7.5 mi). In 
all, the proposed survey will complete approximately 2,145 km (1,333 
mi) of survey lines with an additional 365 km (227 mi) of turns. Data 
acquisition will include approximately 672 hours (hr) of airgun 
operation (28 d x 24 hr).
    The scientific team consists of Drs. Nathan Bangs, Kirk McIntosh 
(Institute for Geophysics, University of Texas) and Eli Silver 
(University of California at Santa Cruz).

Vessel Specifications

    The Langseth, owned by NSF, is a seismic research vessel with a 
propulsion system designed to be as quiet as possible to avoid 
interference with the seismic signals emanating from the airgun array. 
The vessel, which has a length of 71.5 m (235 ft); a beam of 17.0 m (56 
ft); a maximum draft of 5.9 m (19 ft); and a gross tonnage of 3,834, is 
powered by two 3,550 horsepower (hp) Bergen BRG-6 diesel engines which 
drive two propellers. Each propeller has four blades and the shaft 
typically rotates at 750 revolutions per minute. The vessel also has an 
800-hp bowthruster, which is not used during seismic acquisition. The 
Langseth's operation speed during seismic acquisition will be 
approximately 8.5 km per hr (km/h) (5.3 mi per hr (mph) or 4.6 knots 
(kts)) and the cruising speed of the vessel outside of seismic 
operations is 18.5 km/h (11.5 mph or 10 kts).
    The vessel also has an observation tower from which protected 
species visual observers (PSVO) will watch for marine mammals before 
and during the proposed airgun operations. When stationed on the 
observation platform, the PSVO's eye level will be approximately 21.5 m 
(71 ft) above sea level providing the PSVO an unobstructed view around 
the entire vessel.

Acoustic Source Specifications

Seismic Airguns

    The Langseth will deploy a 36-airgun array (two subarrays with 18 
airguns each) at a tow depth of 7 meters (m) (23 feet (ft)). However, 
the Langseth will fire one subarray at a time, so that no more than 18 
airguns will fire at any time. The maximum discharge volume is 3,300 
cubic inches (in\3\). The airguns are a mixture of Bolt 1500LL and Bolt 
1900LLX airguns ranging in size from 40 to 360 in\3\, with a firing 
pressure of 1,900 pounds per square inch. The dominant frequency 
components range from zero to 188 Hertz (Hz).
    The subarray configuration consists of two identical linear or 
strings, with 10 airguns on each string; the first and last airguns 
will be spaced 16 m (52 ft) apart. Of the 10 airguns, nine will fire 
simultaneously while the tenth airgun will serve as a spare and will be 
turned on in case of failure of one of the other airguns. Each airgun 
subarray will emit a pulse at approximately 11-second (s) intervals 
which corresponds to a shot interval of approximately 25 m (82 ft). 
During firing, the airguns will emit a brief (approximately 0.1 s) 
pulse of sound; during the intervening periods of operations, the 
airguns will be silent.
    L-DEO will tow each subarray approximately 140 m (459.3 ft) behind 
the vessel and will distribute the subarrays across an area of 
approximately 12 by 16 m (39.4 by 52.5 ft) behind the Langseth, offset 
by 75 m (246 ft).

Metrics Used in This Document

    This section includes a brief explanation of the sound measurements 
frequently used in the discussions of acoustic effects in this 
document. Sound pressure is the sound force per unit area, and is 
usually measured in micropascals ([mu]Pa), where 1 pascal (Pa) is the 
pressure resulting from a force of one newton exerted over an area of 
one square meter. Sound pressure level (SPL) is expressed as the ratio 
of a measured sound pressure and a reference level. The commonly used 
reference pressure level in underwater acoustics is 1 [mu]Pa, and the 
units for SPLs are dB re: 1 [mu]Pa.
    SPL (in decibels (dB)) = 20 log (pressure/reference pressure)
    SPL is an instantaneous measurement and can be expressed as the 
peak, the peak-peak (p-p), or the root mean square (rms). Root mean 
square, which is the square root of the arithmetic average of the 
squared instantaneous pressure values, is typically used in discussions 
of the effects of sounds on vertebrates and all references to SPL in 
this document refer to the root mean square unless otherwise noted. SPL 
does not take the duration of a sound into account.

Characteristics of the Airgun Pulses

    Airguns function by venting high-pressure air into the water which 
creates an air bubble. The pressure signature of an individual airgun 
consists of a sharp rise and then fall in pressure, followed by several 
positive and negative pressure excursions caused by the oscillation of 
the resulting air bubble. The oscillation of the air bubble transmits 
sounds downward through the seafloor and the amount of sound 
transmitted in the near horizontal directions is reduced. However, the 
airgun array also emits sounds that travel horizontally toward non-
target areas.
    The nominal source levels of the airgun arrays used by L-DEO on the 
Langseth are 236 to 265 dB re: 1 [mu]Pa(p-p) and the rms 
value for a given airgun pulse is typically 16 dB re: 1 [mu]Pa lower 
than the peak-to-peak value. However, the difference between rms and 
peak or peak-to-peak values for a given pulse depends on the frequency 
content and duration of the pulse, among other factors.
    Accordingly, L-DEO has predicted the received sound levels in 
relation to distance and direction from the 18-airgun subarray and the 
single Bolt 1900LL 40-in\3\ airgun, which will be used during power 
downs. A detailed description of L-DEO's modeling for marine seismic 
source arrays for species mitigation is provided in Appendix A of L-
DEO's application. These are the nominal source levels applicable to 
downward propagation. The effective source levels for horizontal 
propagation are lower than those for downward propagation when the 
source consists of numerous airguns spaced apart from one another.
    Appendix B of L-DEO's environmental analysis discusses the 
characteristics of the airgun pulses. NMFS refers the reviewers to the 
application and environmental analysis documents for additional 
information.

Predicted Sound Levels for the Airguns

    Tolstoy et al., (2009) reported results for propagation 
measurements of pulses from the Langseth's 36-airgun, 6,600 in\3\ array 
in shallow-water (approximately 50 m (164 ft)) and deep-water depths 
(approximately 1,600 m (5,249 ft)) in the Gulf of Mexico in 2007 and 
2008. L-DEO has used these reported empirical values to determine 
exclusion zones for the 18-airgun subarray and the single airgun; to 
designate mitigation zones, and to estimate take (described in greater 
detail in Section VII and Section IV of L-DEO's application and 
environmental analysis, respectively) for marine mammals.
    Results of the Gulf of Mexico calibration study (Tolstoy et al., 
2009) showed that radii around the airguns for various received levels 
varied with water depth. The empirical data for deep water (greater 
than 1,000 m; 3,280 ft) indicated that the L-DEO model (as applied to 
the Langseth's 36-airgun array) overestimated the received sound levels 
at a given distance. However, to be conservative, L-DEO has applied the 
modeled distances for the 36-airgun

[[Page 6433]]

array in deep water to the 18-airgun subarray when operating in deep-
water areas during the proposed study (Table 1). L-DEO set 2,000 m (1.2 
mi) as the maximum relevant depth as very few, if any, mammals are 
expected to occur below this depth.
    The empirical data for shallow water (< 100 m; 328 ft) indicated 
that the L-DEO model (as applied to the Langseth's 36-airgun array) 
underestimated actual received levels. Accordingly, L-DEO has applied 
correction factors to the distances reported by Tolstoy et al. (2009) 
for shallow depth water. For the 36-airgun array, the distances 
measured in shallow-water to the 160- to 190-dB isopleths ranged from 
1.7 to 5.2 times higher than the distances in deep water (Tolstoy et 
al. 2009). During the proposed cruise, the same factors will be applied 
to derive appropriate shallow-water radii from the modeled deep-water 
radii for the Langseth's 18-airgun subarray (Table 1).
    For intermediate-depths (100-1,000 m; 328-3,280 ft), L-DEO has 
applied a correction factor of 1.5 to the estimates provided by the 
model for the 18-airgun subarray operating in deep-water situations to 
predict safety radii for intermediate-depth sites. L-DEO applied the 
same correction factor to model estimates for an L-DEO cruise in the 
same area in 2003 and 2004.
    Table 1 summarizes the predicted distances at which sound levels 
(160- and 180-dB) are expected to be received from the 18-airgun 
subarray and a single airgun operating in shallow, intermediate and 
deep water depths.

  Table 1--Predicted Distances To Which Sound Levels >= 190, 180, and 160 dB re: 1 [mu]Parms Could Be Received
During the Proposed Survey Using A 18-Airgun Subarray, as Well as a Single Airgun Towed at a Depth Of 7 M in the
                                           Etp During April-May, 2011
                            [Distances are based on model results provided by L-DEO.]
----------------------------------------------------------------------------------------------------------------
                                                                                 Predicted RMS Distances (m)
         Source and volume                        Water depth              -------------------------------------
                                                                                  180 dB             160 dB
----------------------------------------------------------------------------------------------------------------
Single Bolt airgun (40 in\3\).....  Shallow < 100 m.......................                296              1,050
                                    Intermediate..........................                 60                578
                                    100-1,000 m...........................
                                    Deep..................................                 40                385
                                    > 1,000 m.............................
18-Airgun subarray (3,300 in\3\)..  Shallow...............................              1,030           * 19,500
                                    < 100 m...............................
                                    Intermediate..........................                675              5,700
                                    100-1,000 m...........................
                                    Deep..................................                450              3,800
                                    > 1,000 m.............................
----------------------------------------------------------------------------------------------------------------
* This is likely an overestimate, as the measured distance for the 36-airgun array operating in shallow waters
  of the northern Gulf of Mexico was 17,500 m (17.5 km).

    L-DEO conducted modeling for a 2008 survey off Costa Rica using 
site specific data on sound velocity profiles in the water column and 
bottom composition at a depth of 65 m (213.5 ft) in Drake Bay (at the 
proposed survey area) and at a depth of 340 m (1,115 ft) in an area 
approximately 100 km (62 mi) north of the survey area. The modeled 
exclusion zones were smaller than the shallow- and intermediate-depth 
ranges listed in Table 1, suggesting that L-DEO's estimates for the 
proposed survey are overestimates and thus precautionary. Also, the 
estimated 160-dB distance for the 18-airgun subarray in water depths 
less than 100 m (328 ft) (Table 1) is higher than the measured distance 
for the 36-airgun array (17.5 km; Tolstoy et al., 2009), again 
suggesting that these estimates are precautionary. Refer to Appendix A 
of L-DEO's environmental analysis for additional information on L-DEO's 
calculations for the model.

Multibeam Echosounder

    The Langseth will operate a Kongsberg EM 122 MBES concurrently 
during airgun operations to map characteristics of the ocean floor. The 
hull-mounted MBES emits brief pulses of sound (also called a ping) 
(10.5 to 13 kilohertz (kHz)) in a fan-shaped beam that extends downward 
and to the sides of the ship. The transmitting beamwidth is one or two 
degrees ([deg]) fore-aft and 150[deg] athwartship and the maximum 
source level is 242 dB re: 1 [mu]Pa.
    For deep-water operations, each ping consists of eight (in water 
greater than 1,000 m; 3,280 ft) or four (less than 1,000 m; 3,280 ft) 
successive, fan-shaped transmissions, from two to 15 milliseconds (ms) 
in duration and each ensonifying a sector that extends 1[deg] fore-aft. 
The eight successive transmissions span an overall cross-track angular 
extent of about 150[deg], with 2-ms gaps between the pulses for 
successive sectors.

Sub-Bottom Profiler

    The Langseth will also operate a Knudsen 320B SBP continuously 
throughout the cruise with the MBES to provide information about the 
sedimentary features and bottom topography. The dominant frequency 
component of the SBP is 3.5 kHz which is directed downward in a 30[deg] 
cone by a hull-mounted transducer on the vessel. The maximum output is 
1,000 watts (204 dB re: 1 [mu]Pa), but in practice, the output varies 
with water depth. The pulse interval is one second, but a common mode 
of operation is to broadcast five pulses at 1-s intervals followed by a 
5-s pause.
    NMFS expects that acoustic stimuli resulting from the proposed 
operation of the single airgun or the 18-airgun subarray has the 
potential to harass marine mammals, incidental to the conduct of the 
proposed seismic survey. NMFS expects these disturbances to be 
temporary and result, at worst, in a temporary modification in behavior 
and/or low-level physiological effects (Level B Harassment) of small 
numbers of certain species of marine mammals. NMFS does not expect that 
the movement of the Langseth, during the conduct of the seismic survey, 
has the potential to harass marine mammals because of the relatively 
slow operation speed of the vessel (4.6 kts; 8.5 km/h; 5.3 mph) during 
seismic acquisition.

Description of the Specified Geographic Region

    The survey will encompass the area bounded by 8.5-9[deg] N, 83.75-
84.25[deg] W

[[Page 6434]]

offshore from Costa Rica in the Pacific Ocean (see Figure 1 in L-DEO's 
application). The closest that the Langseth will approach the coastline 
is approximately 30 km.

Description of the Marine Mammals in the Area of the Proposed Specified 
Activity

    Twenty-eight marine mammal species may occur in the proposed survey 
area, including 20 odontocetes (toothed cetaceans), 6 mysticetes 
(baleen whales) and two pinnipeds. Of these, 19 cetacean species are 
likely to occur in the proposed survey area in the ETP during April 
through May. Five of these species are listed as endangered under the 
U.S. Endangered Species Act of 1973 (ESA; 16 U.S.C. 1531 et seq.), 
including the humpback (Megaptera novaeangliae), sei (Balaenoptera 
borealis), fin (Balaenoptera physalus), blue (Balaenoptera musculus), 
and sperm (Physeter macrocephalus) whale.
    The species of marine mammals expected to be most common in the 
survey area (all delphinids) include the short-beaked common dolphin 
(Delphinus delphis), spinner dolphin (Stenella longirostris), 
pantropical spotted dolphin (Stenella attenuata), striped dolphin 
(Stenella coeruleoalba), melon-headed whale (Peponocephala electra), 
and bottlenose dolphin (Tursiops truncatus).
    Two pinnipeds, the California sea lion (Zalophus californianus) and 
the Gal[aacute]pagos sea lion (Zalophus wollebaeki), have the potential 
to transit in the vicinity of the proposed seismic survey, although any 
occurrence would be rare as they are vagrants to the area. Based on 
available data and monitoring reports from previous seismic surveys in 
the area, L-DEO does not expect to encounter these species within the 
proposed survey area and does not present analysis for these species. 
Accordingly, NMFS will not consider these pinniped species in greater 
detail and the proposed IHA will only address requested take 
authorizations for mysticetes and odontocetes.
    Table 2 presents information on the abundance, distribution, 
population status, and conservation status of the marine mammals that 
may occur in the proposed survey area April through May, 2011.

  Table 2--Habitat, Regional Abundance, and Conservation Status of Marine Mammals That May Occur in or Near the Proposed Seismic Survey Areas Off Costa
                                                       Rica in the Eastern Tropical Pacific Ocean
                            [See text and Tables 2-4 in L-DEO's application and environmental analysis for further details.]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                            Density
              Species                Occurrence in survey         Habitat             Abundance in the ETP \1\           ESA \2\     -------------------
                                    area during April-May                                                                             Best \3\   Max \4\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Mysticetes
Humpback whale....................  Very rare............  Mainly nearshore       NE Pacific 1392 \6\.............  EN..............      0.25      4.40
                                                            waters and banks.     SE Pacific 2900 \7\.............
Bryde's whale.....................  Uncommon.............  Pelagic and coastal..  13,000 \8\......................  NL..............      0.96      2.52
Sei whale.........................  Very rare............  Mostly pelagic.......  N.A.............................  EN..............      0.01      0.01
Fin whale.........................  Very rare............  Slope, mostly pelagic  2636 \6\........................  EN..............      0.01      0.01
Blue whale........................  Rare.................  Pelagic and coastal..  1415 \9\........................  EN..............      0.13      1.86
Common minke whale................  Very rare............  Coastal..............  N.A.............................  NL..............    < 0.01    < 0.01
Odontocetes
Sperm whale.......................  Uncommon.............  Usually deep pelagic,  26,053 \10\.....................  EN..............      4.19      9.80
                                                            steep topography.
Pygmy sperm whale.................  Very rare............  Deep waters off shelf  N.A. \11\.......................  NL..............      0.03      0.05
Dwarf sperm whale.................  Rare.................  Deep waters off shelf  11,200 \12\.....................  NL..............      0.03      0.05
Cuvier's beaked whale.............  Uncommon.............  Slope and pelagic....  20,000 \9\......................  NL..............      2.47      3.70
Mesoplodon spp....................  Very rare or rare....  Pelagic..............  25,300 \13\.....................  NL..............      0.36      1.00
Rough-toothed dolphin.............  Common...............  Mainly pelagic.......  107,633.........................  NL..............      4.19     11.19
Bottlenose dolphin................  Very common..........  Coastal, shelf,        335,834.........................  NL..............     17.06     90.91
                                                            pelagic.
Pantropical spotted dolphin.......  Very common..........  Coastal and pelagic..  1,575,247 \14\..................  NL..............     76.96    236.66
Spinner dolphin...................  Common...............  Coastal and pelagic..  1,797,716 \14\..................  NL..............     58.43    364.26
Striped dolphin...................  Uncommon.............  Off continental shelf  964,362.........................  NL..............     67.75    154.21
Fraser's dolphin..................  Rare.................  Pelagic..............  289,300 \9\.....................  NL..............    < 0.01    < 0.01
Short-beaked common dolphin.......  Common...............  Shelf, pelagic, high   3,127,203.......................  NL..............    110.89    763.50
                                                            relief.
Risso's dolphin...................  Common...............  Shelf, slope,          110,457.........................  NL..............     12.76     12.76
                                                            seamounts.
Melon-headed whale................  Rare.................  Pelagic..............  45,400 \9\......................  NL..............     11.06     57.70
Pygmy killer whale................  Rare.................  Pelagic..............  38,900 \9\......................  NL..............      1.25      2.30
False killer whale................  Uncommon.............  Pelagic..............  39,800 \9\......................  NL..............      0.01      0.01
Killer whale......................  Rare.................  Widely distributed...  8500 \15\.......................  NL..............      0.19      0.40
Short-finned pilot whale..........  Common...............  Mostly pelagic, high-  589,315 \16\....................  NL..............     11.88     28.22
                                                            relief.
--------------------------------------------------------------------------------------------------------------------------------------------------------
N.A. Not available or not assessed.
\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.
\6\ U.S. west coast (Carretta et al., 2010).
\7\ Southeast Pacific; F[eacute]lix et al. (2005).
\8\ This estimate is mainly for Balaenoptera edeni but may include some B. borealis (Wade and Gerrodette, 1993).
\9\ ETP (Wade and Gerrodette, 1993).
\10\ Eastern temperate North Pacific (Whitehead, 2002).
\11\ California/Oregon/Washington (Carretta et al., 2010).
\12\ This abundance estimate is mostly for K. sima but may also include some K. breviceps (Wade and Gerrodette, 1993).
\13\ This estimate includes all species of the genus Mesoplodon in the ETP (Wade and Gerrodette, 1993).
\14\ For all stocks in ETP.
\15\ ETP (Ford, 2002).

[[Page 6435]]

 
\16\ This estimate is for G. macrorhynchus and G. melas in the ETP (Gerrodette and Forcada, 2002).
\17\ U.S. stock (Carretta et al., 2010).
\18\ Galapagos Islands (Alava and Salazar, 2006).

    Refer to Section III of L-DEO's application for detailed 
information regarding the abundance and distribution, population 
status, and life history and behavior of these species and their 
occurrence in the proposed project area. The application also presents 
how L-DEO calculated the estimated densities for the marine mammals in 
the proposed survey area. NMFS has reviewed these data and determined 
them to be the best available scientific information for the purposes 
of the proposed IHA.

Potential Effects on Marine Mammals

    Acoustic stimuli generated by the operation of the airguns, which 
introduce sound into the marine environment, may have the potential to 
cause Level B harassment of marine mammals in the proposed survey area. 
The effects of sounds from airgun operations might include one of the 
following: tolerance, masking of natural sounds, behavioral 
disturbance, temporary or permanent impairment, or non-auditory 
physical or physiological effects (Richardson et al., 1995; Gordon et 
al., 2004; Nowacek et al., 2007; Southall et al., 2007).
    Permanent hearing impairment, in the unlikely event that it 
occurred, would constitute injury, but temporary threshold shift (TTS) 
is not an injury (Southall et al., 2007). Although the possibility 
cannot be entirely excluded, it is unlikely that the proposed project 
would result in any cases of temporary or permanent hearing impairment, 
or any significant non-auditory physical or physiological effects. 
Based on the available data and studies described here, some behavioral 
disturbance is expected, but NMFS expects the disturbance to be 
localized and short-term.

Tolerance to Sound

    Studies on marine mammals' tolerance to sound in the natural 
environment are relatively rare. Richardson et al. (1995) defines 
tolerance as the occurrence of marine mammals in areas where they are 
exposed to human activities or man-made noise. In many cases, tolerance 
develops by the animal habituating to the stimulus (i.e., the gradual 
waning of responses to a repeated or ongoing stimulus) (Richardson, et 
al., 1995; Thorpe, 1963), but because of ecological or physiological 
requirements, many marine animals may need to remain in areas where 
they are exposed to chronic stimuli (Richardson, et al., 1995).
    Numerous studies have shown that pulsed sounds from airguns are 
often readily detectable in the water at distances of many kilometers. 
Malme et al., (1985) studied the responses of humpback whales on their 
summer feeding grounds in southeast Alaska to seismic pulses from a 
airgun with a total volume of 100-in\3\. They noted that the whales did 
not exhibit persistent avoidance when exposed to the airgun and 
concluded that there was no clear evidence of avoidance, despite the 
possibility of subtle effects, at received levels up to 172 dB: re 1 
[mu]Pa.
    Weir (2008) observed marine mammal responses to seismic pulses from 
a 24-airgun array firing a total volume of either 5,085 in\3\ or 3,147 
in\3\ in Angolan waters between August 2004 and May 2005. She recorded 
a total of 207 sightings of humpback whales (n = 66), sperm whales (n = 
124), and Atlantic spotted dolphins (n = 17) and reported that there 
were no significant differences in encounter rates (sightings/hr) for 
humpback and sperm whales according to the airgun array's operational 
status (i.e., active versus silent).

Masking of Natural Sounds

    The term masking refers to the inability of a subject to recognize 
the occurrence of an acoustic stimulus as a result of the interference 
of another acoustic stimulus (Clark et al., 2009). Introduced 
underwater sound may, through masking, reduce the effective 
communication distance of a marine mammal species if the frequency of 
the source is close to that used as a signal by the marine mammal, and 
if the anthropogenic sound is present for a significant fraction of the 
time (Richardson et al., 1995).
    Masking effects of pulsed sounds (even from large arrays of 
airguns) on marine mammal calls and other natural sounds are expected 
to be limited. Because of the intermittent nature and low duty cycle of 
seismic airgun pulses, animals can emit and receive sounds in the 
relatively quiet intervals between pulses. However, in some situations, 
reverberation occurs for much or the entire interval between pulses 
(e.g., Simard et al., 2005; Clark and Gagnon, 2006) which could mask 
calls. Some baleen and toothed whales are known to continue calling in 
the presence of seismic pulses, and their calls can usually be heard 
between the seismic pulses (e.g., Richardson et al., 1986; McDonald et 
al., 1995; Greene et al., 1999; Nieukirk et al., 2004; Smultea et al., 
2004; Holst et al., 2005a,b, 2006; and Dunn and Hernandez, 2009). 
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 they continued calling in the presence 
of seismic pulses (Madsen et al., 2002; Tyack et al., 2003; Smultea et 
al., 2004; Holst et al., 2006; and Jochens et al., 2008). Dolphins and 
porpoises commonly are heard calling while airguns are operating (e.g., 
Gordon et al., 2004; Smultea et al., 2004; Holst et al., 2005a, b; and 
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, NMFS expects the masking effects of seismic pulses to 
be minor, given the normally intermittent nature of seismic pulses. 
Refer to Appendix B (4) of L-DEO's environmental analysis for a more 
detailed discussion of masking effects on marine mammals.

Behavioral Disturbance

    Disturbance includes a variety of effects, including subtle to 
conspicuous changes in behavior, movement, 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 does react briefly to an 
underwater sound by changing its behavior or moving a small distance, 
the impacts of the change are unlikely to be significant to the 
individual, let alone the stock or population. However, if a sound 
source displaces marine mammals from an important feeding or breeding 
area for a prolonged period, impacts on individuals and populations 
could be significant (e.g., 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 would be present within a

[[Page 6436]]

particular distance of industrial activities and/or exposed to a 
particular level of industrial sound. In most cases, this approach 
likely overestimates the numbers of marine mammals that would be 
affected in some biologically-important manner.
    The sound criteria used to estimate how many marine mammals might 
be disturbed to some biologically-important degree by a seismic program 
are based primarily on behavioral observations of a few species. 
Scientists have conducted detailed studies on humpback, gray, bowhead 
(Balaena mysticetus), and sperm whales. Less detailed data are 
available for some other species of baleen whales, small toothed 
whales, and sea otters (Enhydra lutris), but for many species there are 
no data on responses to marine seismic surveys.
    Baleen Whales--Baleen whales generally tend to avoid operating 
airguns, but avoidance radii are quite variable (reviewed in 
Richardson, et al., 1995). Whales are often reported to show no overt 
reactions to pulses from large arrays of airguns at distances beyond a 
few kilometers, even though the airgun pulses remain well above ambient 
noise levels out to much longer distances. However, as reviewed in 
Appendix B (5) of L-DEO's environmental analysis, baleen whales exposed 
to strong noise pulses from airguns often react by deviating from their 
normal migration route and/or interrupting their feeding and moving 
away. In the cases of migrating gray and bowhead whales, the observed 
changes in behavior appeared to be of little or no biological 
consequence to the animals (Richardson, et al., 1995). They simply 
avoided the sound source by displacing their migration route to varying 
degrees, but within the natural boundaries of the migration corridors.
    Studies of gray, bowhead, and humpback whales have shown that 
seismic pulses with received levels of 160 to 170 dB re: 1 [mu]Pa seem 
to cause obvious avoidance behavior in a substantial fraction of the 
animals exposed (Malme et al., 1986, 1988; Richardson et al., 1995). In 
many areas, seismic pulses from large arrays of airguns diminish to 
those levels at distances ranging from four to 15 km from the source. A 
substantial proportion of the baleen whales within those distances may 
show avoidance or other strong behavioral reactions to the airgun 
array. Subtle behavioral changes sometimes become evident at somewhat 
lower received levels, and studies summarized in Appendix B (5) of L-
DEO's environmental analysis 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.
    McCauley et al. (1998, 2000) studied the responses of humpback 
whales off western Australia to a full-scale seismic survey with a 16-
airgun array (2,678-in\3\) and to a single airgun (20-in\3\) with 
source level of 227 dB re: 1 [mu]Pa(p-p). In the 1998 study, 
they documented that avoidance reactions began at five to eight km from 
the array, and that those reactions kept most pods approximately three 
to four km from the operating seismic boat. In the 2000 study, they 
noted localized displacement during migration of four to five km by 
traveling pods and seven to 12 km by more sensitive resting pods of 
cow-calf pairs. Avoidance distances with respect to the single airgun 
were smaller but consistent with the results from the full array in 
terms of the received sound levels. The mean received level for initial 
avoidance of an approaching airgun was 140 dB re: 1 [mu]Pa for humpback 
pods containing females, and at the mean closest point of approach 
distance the received level was 143 dB re: 1 [mu]Pa. The initial 
avoidance response generally occurred at distances of five to eight km 
from the airgun array and two km from the single airgun. However, some 
individual humpback whales, especially males, approached within 
distances of 100 to 400 m (328 to 1,312 ft), where the maximum received 
level was 179 dB re: 1 [mu]Pa.
    Humpback whales on their summer feeding grounds in southeast Alaska 
did not exhibit persistent avoidance when exposed to seismic pulses 
from a 1.64-L (100-in\3\) airgun (Malme et al., 1985). Some humpbacks 
seemed ``startled'' at received levels of 150 to 169 dB re: 1 [mu]Pa. 
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 dB re: 1 [mu]Pa.
    Studies have suggested that south Atlantic humpback whales 
wintering off Brazil may be displaced or even strand upon exposure to 
seismic surveys (Engel et al., 2004). The evidence for this was 
circumstantial and subject to alternative explanations (IAGC, 2004). 
Also, the evidence was not consistent with subsequent results from the 
same area of Brazil (Parente et al., 2006), or with direct studies of 
humpbacks exposed to seismic surveys in other areas and seasons. After 
allowance for data from subsequent years, there was no observable 
direct correlation between strandings and seismic surveys (IWC, 
2007:236).
    There are no data on reactions of right whales to seismic surveys, 
but results from the closely-related bowhead whale show that their 
responsiveness can be quite variable depending on their activity 
(migrating versus feeding). Bowhead whales migrating west across the 
Alaskan Beaufort Sea in autumn, in particular, are unusually 
responsive, with substantial avoidance occurring out to distances of 20 
to 30 km from a medium-sized airgun source at received sound levels of 
around 120 to 130 dB re: 1 [mu]Pa (Miller et al., 1999; Richardson et 
al., 1999; see Appendix B (5) of L-DEO's environmental analysis). 
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 the summer, bowheads typically 
begin to show avoidance reactions at received levels of about 152 to 
178 dB re: 1 [mu]Pa (Richardson et al., 1986, 1995; Ljungblad et al., 
1988; Miller et al., 2005).
    Reactions of migrating and feeding (but not wintering) gray whales 
to seismic surveys have been studied. Malme et al. (1986, 1988) studied 
the responses of feeding eastern Pacific gray whales to pulses from a 
single 100-in\3\ airgun off St. Lawrence Island in the northern Bering 
Sea. They estimated, based on small sample sizes, that 50 percent of 
feeding gray whales stopped feeding at an average received pressure 
level of 173 dB re: 1 [mu]Pa on an (approximate) rms basis, and that 10 
percent of feeding whales interrupted feeding at received levels of 163 
dB re: 1 [mu]Pa. Those findings were generally consistent with the 
results of experiments conducted on larger numbers of gray whales that 
were migrating along the California coast (Malme et al., 1984; Malme 
and Miles, 1985), and western Pacific gray whales feeding off Sakhalin 
Island, Russia (Wursig et al., 1999; Gailey et al., 2007; Johnson et 
al., 2007; Yazvenko et al., 2007a, b), along with data on gray whales 
off British Columbia (Bain and Williams, 2006).
    Various species of Balaenoptera (blue, sei, fin, and minke whales) 
have occasionally been seen 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 (e.g., McDonald et al., 1995; Dunn and

[[Page 6437]]

Hernandez, 2009). Sightings by observers on seismic vessels off the 
United Kingdom from 1997 to 2000 suggest that, during times of good 
sightability, sighting rates for mysticetes (mainly fin and sei whales) 
were similar when large arrays of airguns were shooting vs. silent 
(Stone, 2003; Stone and Tasker, 2006). However, these whales tended to 
exhibit localized avoidance, remaining significantly further (on 
average) from the airgun array during seismic operations compared with 
non-seismic periods (Stone and Tasker, 2006). In a study off of 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 directions during seismic 
versus non-seismic periods (Moulton et al., 2005, 2006a,b).
    Data on short-term reactions by cetaceans to impulsive noises are 
not necessarily indicative of long-term or biologically significant 
effects. It is not known whether impulsive sounds affect reproductive 
rate or distribution and habitat use in subsequent days or years. 
However, gray whales have continued to migrate annually along the west 
coast of North America with substantial increases in the population 
over recent years, despite intermittent seismic exploration (and much 
ship traffic) in that area for decades (Appendix A in Malme et al., 
1984; Richardson et al., 1995; Allen and Angliss, 2010). The western 
Pacific gray whale population did not seem affected by a seismic survey 
in its feeding ground during a previous year (Johnson et al., 2007). 
Similarly, bowhead whales have continued to travel to the eastern 
Beaufort Sea each summer, and their numbers have increased notably, 
despite seismic exploration in their summer and autumn range for many 
years (Richardson et al., 1987; Angliss and Allen, 2009).
    Toothed Whales--Little systematic information is available about 
reactions of toothed whales to noise pulses. Few studies similar to the 
more extensive baleen whale/seismic pulse work summarized above and (in 
more detail) in Appendix B of L-DEO's environmental analysis have been 
reported for toothed whales. However, there are recent systematic 
studies on sperm whales (e.g., Gordon et al., 2006; Madsen et al., 
2006; Winsor and Mate, 2006; Jochens et al., 2008; Miller et al., 
2009). There is an increasing amount of information about responses of 
various odontocetes to seismic surveys based on monitoring studies 
(e.g., Stone, 2003; Smultea et al., 2004; Moulton and Miller, 2005; 
Bain and Williams, 2006; Holst et al., 2006; Stone and Tasker, 2006; 
Potter et al., 2007; Hauser et al., 2008; Holst and Smultea, 2008; 
Weir, 2008; Barkaszi et al., 2009; Richardson et al., 2009).
    Seismic operators and marine mammal observers on seismic vessels 
regularly see dolphins and other small toothed whales near operating 
airgun arrays, but in general there is a tendency for most delphinids 
to show some avoidance of operating seismic vessels (e.g., Goold, 
1996a,b,c; Calambokidis and Osmek, 1998; Stone, 2003; Moulton and 
Miller, 2005; Holst et al., 2006; Stone and Tasker, 2006; Weir, 2008; 
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 arrays of airguns 
are firing (e.g., Moulton and Miller, 2005). Nonetheless, small toothed 
whales more often tend to head away, or to maintain a somewhat greater 
distance from the vessel, when a large array of airguns is operating 
than when it is silent (e.g., Stone and Tasker, 2006; Weir, 2008). In 
most cases, the avoidance radii for delphinids appear to be small, on 
the order of one km 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 in the southeastern Beaufort Sea during summer 
found that sighting rates of beluga whales were significantly lower at 
distances 10 to 20 km compared with 20 to 30 km from an operating 
airgun array, and observers on seismic boats in that area rarely see 
belugas (Miller et al., 2005; Harris et al., 2007).
    Captive bottlenose dolphins (Tursiops truncatus) and beluga whales 
exhibited changes in behavior when exposed to strong pulsed sounds 
similar in duration to those typically used in seismic surveys 
(Finneran et al., 2000, 2002, 2005). However, the animals tolerated 
high received levels of sound before exhibiting aversive behaviors.
    Results for porpoises depend on species. The limited available data 
suggest that harbor porpoises (Phocoena phocoena) show stronger 
avoidance of seismic operations than do Dall's porpoises (Phocoenoides 
dalli) (Stone, 2003; MacLean and Koski, 2005; Bain and Williams, 2006; 
Stone and Tasker, 2006). Dall's porpoises seem relatively tolerant of 
airgun operations (MacLean and Koski, 2005; Bain and Williams, 2006), 
although they too have been observed to avoid large arrays of operating 
airguns (Calambokidis and Osmek, 1998; Bain and Williams, 2006). This 
apparent difference in responsiveness of these two porpoise species is 
consistent with their relative responsiveness to boat traffic and some 
other acoustic sources (Richardson et al., 1995; Southall et al., 
2007).
    Most studies of sperm whales exposed to airgun sounds indicate that 
the sperm whale shows considerable tolerance of airgun pulses (e.g., 
Stone, 2003; Moulton et al., 2005, 2006a; Stone and Tasker, 2006; Weir, 
2008). In most cases the whales do not show strong avoidance, and they 
continue to call (see Appendix B of L-DEO's environmental analysis for 
review). However, controlled exposure experiments in the Gulf of Mexico 
indicate that foraging behavior was altered upon exposure to airgun 
sound (Jochens et al., 2008; Miller et al., 2009; Tyack, 2009).
    There are almost no specific data on the behavioral reactions of 
beaked whales to seismic surveys. However, some northern bottlenose 
whales (Hyperoodon ampullatus) remained in the general area and 
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 (e.g., Wursig et al., 1998). They 
may also dive for an extended period when approached by a vessel (e.g., 
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). Based on a 
single observation, Aguilar-Soto et al. (2006) suggested that foraging 
efficiency of Cuvier's beaked whales may be reduced by close approach 
of vessels. 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.
    There are increasing indications that some beaked whales tend to 
strand when naval exercises involving mid-frequency sonar operation are 
ongoing nearby (e.g., Simmonds and Lopez-Jurado, 1991; Frantzis, 1998; 
NOAA and

[[Page 6438]]

USN, 2001; Jepson et al., 2003; Hildebrand, 2005; Barlow and Gisiner, 
2006; see also the Stranding and Mortality section in this notice). 
These strandings are apparently a disturbance response, although 
auditory or other injuries or other physiological effects may also be 
involved. Whether beaked whales would ever react similarly to seismic 
surveys is unknown. Seismic survey sounds are quite different from 
those of the sonar in operation during the above-cited incidents.
    Odontocete reactions to large arrays of airguns are variable and, 
at least for delphinids and Dall's porpoises, seem to be confined to a 
smaller radius than has been observed for the more responsive of the 
mysticetes, belugas, and harbor porpoises (Appendix B of L-DEO's 
environmental analysis).

Hearing Impairment and Other Physical Effects

    Exposure to high intensity sound for a sufficient duration may 
result in auditory effects such as a noise-induced threshold shift--an 
increase in the auditory threshold after exposure to noise (Finneran, 
Carder, Schlundt, and Ridgway, 2005). Factors that influence the amount 
of threshold shift include the amplitude, duration, frequency content, 
temporal pattern, and energy distribution of noise exposure. The 
magnitude of hearing threshold shift normally decreases over time 
following cessation of the noise exposure. The amount of threshold 
shift just after exposure is called the initial threshold shift. If the 
threshold shift eventually returns to zero (i.e., the threshold returns 
to the pre-exposure value), it is called temporary threshold shift 
(TTS) (Southall et al., 2007).
    Researchers have studied TTS in certain captive odontocetes and 
pinnipeds exposed to strong sounds (reviewed in Southall et al., 2007). 
However, there has been no specific documentation of TTS let alone 
permanent hearing damage, i.e., permanent threshold shift (PTS), in 
free-ranging marine mammals exposed to sequences of airgun pulses 
during realistic field conditions.
    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). Table 1 presents the 
distances from the Langseth'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.
    To avoid the potential for injury, NMFS (1995, 2000) concluded that 
cetaceans should not be exposed to pulsed underwater noise at received 
levels exceeding 180 dB re: 1 [mu]Pa. NMFS believes that to avoid the 
potential for permanent physiological damage (Level A harassment), 
cetaceans should not be exposed to pulsed underwater noise at received 
levels exceeding 180 dB re: 1 [mu]Pa. The 180-dB level is a shutdown 
criterion applicable to cetaceans, as specified by NMFS (2000); these 
levels were used to establish the EZs. NMFS also assumes that cetaceans 
exposed to levels exceeding 160 dB re: 1 [mu]Pa (rms) may experience 
Level B harassment.
    Researchers have derived TTS information for odontocetes from 
studies on the bottlenose dolphin and beluga. For the one harbor 
porpoise tested, the received level of airgun sound that elicited onset 
of TTS was lower (Lucke et al., 2009). If these results from a single 
animal are representative, it is inappropriate to assume that onset of 
TTS occurs at similar received levels in all odontocetes (cf. Southall 
et al., 2007). Some cetaceans apparently can incur TTS at considerably 
lower sound exposures than are necessary to elicit TTS in the beluga or 
bottlenose dolphin.
    For baleen whales, there are no data, direct or indirect, on levels 
or properties of sound that are required to induce TTS. The frequencies 
to which baleen whales are most sensitive are assumed to be lower than 
those to which odontocetes are most sensitive, and natural background 
noise levels at those low frequencies tend to be higher. As a result, 
auditory thresholds of baleen whales within their frequency band of 
best hearing are believed to be higher (less sensitive) than are those 
of odontocetes at their best frequencies (Clark and Ellison, 2004). 
From this, it is suspected that received levels causing TTS onset may 
also be higher in baleen whales (Southall et al., 2007). For this 
proposed study, L--DEO expects no cases of TTS given: (1) The low 
abundance of baleen whales in the planned study area at the time of the 
survey; and (2) the strong likelihood that baleen whales would avoid 
the approaching airguns (or vessel) before being exposed to levels high 
enough for TTS to occur. 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, whereas in other cases, 
the animal has an impaired ability to hear sounds in specific frequency 
ranges (Kryter, 1985). There is no specific evidence that exposure to 
pulses of airgun sound can cause PTS in any marine mammal, even with 
large arrays of airguns. However, given the possibility that mammals 
close to an airgun array might incur at least mild TTS, there has been 
further speculation about the possibility that some individuals 
occurring very close to airguns might incur PTS (e.g., Richardson et 
al., 1995, p. 372ff; 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 B (6) 
of L-DEO's environmental analysis. Based on data from terrestrial 
mammals, a precautionary assumption is that the PTS threshold for 
impulse sounds (such as airgun pulses as received close to the source) 
is at least 6 dB higher than the TTS threshold on a peak-pressure 
basis, and probably greater than six dB (Southall et al., 2007).
    Given the higher level of sound necessary to cause PTS as compared 
with TTS, it is considerably less likely that PTS would occur. Baleen 
whales generally avoid the immediate area around operating seismic 
vessels, as do some other marine mammals.
    Stranding and Mortality--Marine mammals close to underwater 
detonations of high explosives can be killed or severely injured, and 
the auditory organs are especially susceptible to injury (Ketten et 
al., 1993; Ketten, 1995). However, explosives are no longer used for 
marine waters for commercial seismic surveys or (with rare exceptions) 
for seismic research; they have been replaced entirely by airguns or 
related non-explosive pulse generators. Airgun pulses are less 
energetic and have slower rise times,

[[Page 6439]]

and there is no specific evidence that they can cause serious injury, 
death, or stranding even in the case of large airgun arrays. However, 
the association of strandings of beaked whales with naval exercises 
involving mid-frequency active sonar and, in one case, an L-DEO seismic 
survey (Malakoff, 2002; Cox et al., 2006), has raised the possibility 
that beaked whales exposed to strong ``pulsed'' sounds may be 
especially susceptible to injury and/or behavioral reactions that can 
lead to stranding (e.g., Hildebrand, 2005; Southall et al., 2007). 
Appendix B (6) of L-DEO's environmental analysis 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. 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 supersaturated 
tissue by a behavioral response to acoustic exposure, could be a 
pathologic mechanism for the strandings and mortality of some deep-
diving cetaceans exposed to sonar. However, the evidence for this 
remains circumstantial and associated with exposure to naval mid-
frequency sonar, not seismic surveys (Cox et al., 2006; Southall et 
al., 2007).
    Seismic pulses and mid-frequency sonar signals are quite different, 
and some mechanisms by which sonar sounds have been hypothesized to 
affect beaked whales are unlikely to apply to airgun pulses. Sounds 
produced by airgun arrays are broadband impulses with most of the 
energy below one kHz. Typical military mid-frequency sonar emits non-
impulse sounds at frequencies of two to 10 kHz, generally with a 
relatively narrow bandwidth at any one time. A further difference 
between seismic surveys and naval exercises is that naval exercises can 
involve sound sources on more than one vessel. Thus, it is not 
appropriate to assume that there is a direct connection between the 
effects of military sonar and seismic surveys on marine mammals. 
However, evidence that sonar signals can, in special circumstances, 
lead (at least indirectly) to physical damage and mortality (e.g., 
Balcomb and Claridge, 2001; NOAA and USN, 2001; Jepson et al., 2003; 
Fern[aacute]ndez et al., 2004, 2005; Hildebrand 2005; Cox et al., 2006) 
suggests that caution is warranted when dealing with exposure of marine 
mammals to any high-intensity ``pulsed'' sound.
    There is no conclusive evidence of cetacean strandings or deaths at 
sea as a result of exposure to seismic surveys, but a few cases of 
strandings in the general area where a seismic survey was ongoing have 
led to speculation concerning a possible link between seismic surveys 
and strandings. Suggestions that there was a link between seismic 
surveys and strandings of humpback whales in Brazil (Engel et al., 
2004) were not well founded (IAGC, 2004; IWC, 2007). In September 2002, 
there was a stranding of two Cuvier's beaked whales (Ziphius 
cavirostris) in the Gulf of California, Mexico, when the L DEO vessel 
R/V Maurice Ewing was operating a 20-airgun (8,490 in\3\) in the 
general area. The link between the stranding and the seismic surveys 
was inconclusive and not based on any physical evidence (Hogarth, 2002; 
Yoder, 2002). Nonetheless, the Gulf of California incident plus the 
beaked whale strandings near naval exercises involving use of mid-
frequency sonar suggests a need for caution in conducting seismic 
surveys in areas occupied by beaked whales until more is known about 
effects of seismic surveys on those species (Hildebrand, 2005). No 
injuries of beaked whales are anticipated during the proposed study 
because of:
    (1) The high likelihood that any beaked whales nearby would avoid 
the approaching vessel before being exposed to high sound levels,
    (2) differences between the sound sources operated by L-DEO and 
those involved in the naval exercises associated with strandings.
    Non-auditory Physiological Effects-- Non-auditory physiological 
effects or injuries that theoretically might occur in marine mammals 
exposed to strong underwater sound include stress, neurological 
effects, bubble formation, resonance, and other types of organ or 
tissue damage (Cox et al., 2006; Southall et al., 2007). Studies 
examining such effects are limited. However, resonance effects (Gentry, 
2002) and direct noise-induced bubble formations (Crum et al., 2005) 
are implausible in the case of exposure to an impulsive broadband 
source like an airgun array. If seismic surveys disrupt diving patterns 
of deep-diving species, this might perhaps result in bubble formation 
and a form of the bends, as speculated to occur in beaked whales 
exposed to sonar. However, there is no specific evidence of this upon 
exposure to airgun pulses.
    In general, very little is known about the potential for seismic 
survey sounds (or other types of strong underwater sounds) to cause 
non-auditory physical effects in marine mammals. Such effects, if they 
occur at all, would presumably be limited to short distances and to 
activities that extend over a prolonged period. The available data do 
not allow identification of a specific exposure level above which non-
auditory effects can be expected (Southall et al., 2007), or any 
meaningful quantitative predictions of the numbers (if any) of marine 
mammals that might be affected in those ways. Marine mammals that show 
behavioral avoidance of seismic vessels, including most baleen whales 
and some odontocetes, are especially unlikely to incur non-auditory 
physical effects.

Potential Effects of Other Acoustic Devices

MBES
    L-DEO will operate the Kongsberg EM 122 MBES from the source vessel 
during the planned study. Sounds from the MBES are very short pulses, 
occurring for two to 15 ms once every five to 20 s, depending on water 
depth. Most of the energy in the sound pulses emitted by this MBES is 
at frequencies near 12 kHz, and the maximum source level is 242 dB re: 
1 [mu]Pa. The beam is narrow (1 to 2[deg]) in fore-aft extent and wide 
(150[deg]) in the cross-track extent. Each ping consists of eight (in 
water greater than 1,000 m deep) or four (less than 1,000 m deep) 
successive fan-shaped transmissions (segments) at different cross-track 
angles. Any given mammal at depth near the trackline would be in the 
main beam for only one or two of the nine segments. Also, marine 
mammals that encounter the 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-to-15 ms pulse (or two pulses if in the overlap area). Similarly, 
Kremser et al. (2005) noted that the probability of a cetacean swimming 
through the area of exposure when an MBES emits

[[Page 6440]]

a pulse is small. The animal would have to pass the transducer at close 
range and be swimming at speeds similar to the vessel in order to 
receive the multiple pulses that might result in sufficient exposure to 
cause TTS.
    Navy sonars that have been linked to avoidance reactions and 
stranding of cetaceans: (1) Generally have longer pulse duration than 
the Kongsberg EM 122; and (2) are often directed close to horizontally 
versus more downward for the MBES. The area of possible influence of 
the MBES is much smaller--a narrow band below the source vessel. Also, 
the duration of exposure for a given marine mammal can be much longer 
for naval sonar. During L-DEO's operations, the individual pulses will 
be very short, and a given mammal would not receive many of the 
downward-directed pulses as the vessel passes by. Possible effects of 
an MBES on marine mammals are outlined below.
    Masking--Marine mammal communications will not be masked 
appreciably by the MBES signals given the low duty cycle of the 
echosounder and the brief period when an individual mammal is likely to 
be within its beam. Furthermore, in the case of baleen whales, the MBES 
signals (12 kHz) do not overlap with the predominant frequencies in the 
calls, which would avoid any significant masking.
    Behavioral Responses--Behavioral reactions of free-ranging marine 
mammals to 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 melas) 
(Rendell and Gordon, 1999), and the previously-mentioned beachings by 
beaked whales. During exposure to a 21 to 25 kHz ``whale-finding'' 
sonar with a source level of 215 dB re: 1 [mu]Pa, gray whales reacted 
by orienting slightly away from the source and being deflected from 
their course by approximately 200 m (Frankel, 2005). When a 38-kHz 
echosounder and a 150-kHz acoustic Doppler current profiler were 
transmitting during studies in the Eastern Tropical Pacific, baleen 
whales showed no significant responses, while spotted and spinner 
dolphins were detected slightly more often and beaked whales less often 
during visual surveys (Gerrodette and Pettis, 2005).
    Captive bottlenose dolphins and a 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 L DEO, and to shorter 
broadband pulsed signals. Behavioral changes typically involved what 
appeared to be deliberate attempts to avoid the sound exposure 
(Schlundt et al., 2000; Finneran et al., 2002; Finneran and Schlundt, 
2004). The relevance of those data to free-ranging odontocetes is 
uncertain, and in any case, the test sounds were quite different in 
duration as compared with those from an MBES.
    Hearing Impairment and Other Physical Effects--Given recent 
stranding events that have been associated with the operation of naval 
sonar, there is concern that mid-frequency sonar sounds can cause 
serious impacts to marine mammals (see above). However, the MBES 
proposed for use by L DEO is quite different than sonar used for navy 
operations. Pulse duration of the MBES is very short relative to the 
naval sonar. Also, at any given location, an individual marine mammal 
would be in the beam of the MBES for much less time given the generally 
downward orientation of the beam and its narrow fore-aft beamwidth; 
navy sonar often uses near-horizontally-directed sound. Those factors 
would all reduce the sound energy received from the MBES rather 
drastically relative to that from naval sonar.
    NMFS believes that the brief exposure of marine mammals to one 
pulse, or small numbers of signals, from the MBES is not likely to 
result in the harassment of marine mammals.

SBP

    L-DEO will also operate a SBP from the source vessel during the 
proposed survey. Sounds from the SBP are very short pulses, occurring 
for one to four ms once every second. Most of the energy in the sound 
pulses emitted by the SBP is at 3.5 kHz, and the beam is directed 
downward. The sub-bottom profiler on the Langseth has a maximum source 
level of 204 dB re: 1 [mu]Pa.
    Kremser et al. (2005) noted that the probability of a cetacean 
swimming through the area of exposure when a bottom profiler emits a 
pulse is small--even for an SBP more powerful than that on the 
Langseth--if the animal was in the area, it would have to pass the 
transducer at close range and in order to be subjected to sound levels 
that could cause TTS.
    Masking--Marine mammal communications will not be masked 
appreciably by the SBP signals given the directionality of the signal 
and the brief period when an individual mammal is likely to be within 
its beam. Furthermore, in the case of most baleen whales, the SBP 
signals do not overlap with the predominant frequencies in the calls, 
which would avoid significant masking.
    Behavioral Responses--Marine mammal behavioral reactions to other 
pulsed sound sources are discussed above, and responses to the SBP are 
likely to be similar to those for other pulsed sources if received at 
the same levels. However, the pulsed signals from the SBP are 
considerably weaker than those from the MBES. Therefore, behavioral 
responses are not expected unless marine mammals are very close to the 
source.
    Hearing Impairment and Other Physical Effects--It is unlikely that 
the SBP produces pulse levels strong enough to cause hearing impairment 
or other physical injuries even in an animal that is (briefly) in a 
position near the source. The SBP is usually operated simultaneously 
with other higher-power acoustic sources. Many marine mammals will move 
away in response to the approaching higher-power sources or the vessel 
itself before the mammals would be close enough for there to be any 
possibility of effects from the less intense sounds from the SBP.
    The potential effects to marine mammals described in this section 
of the document do not take into consideration the proposed monitoring 
and mitigation measures described later in this document (see the 
``Proposed Mitigation'' and ``Proposed Monitoring and Reporting'' 
sections) which, as noted are designed to effect the least practicable 
adverse impact on affected marine mammal species and stocks.

Anticipated Effects on Marine Mammal Habitat

    The proposed seismic survey will not result in any permanent impact 
on habitats used by the marine mammals in the proposed survey area, 
including the food sources they use (i.e. fish and invertebrates), 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 associated with the proposed activity will be temporarily 
elevated noise levels and the associated direct effects on marine 
mammals, previously discussed in this notice.

Anticipated Effects on Fish

    One reason for the adoption of airguns as the standard energy 
source for marine seismic surveys is that, unlike

[[Page 6441]]

explosives, they have not been associated with large-scale fish kills. 
However, existing information on the impacts of seismic surveys on 
marine fish populations is limited (see Appendix D of L-DEO's 
environmental analysis). There are three types of potential effects of 
exposure to seismic surveys: (1) Pathological, (2) physiological, and 
(3) behavioral. Pathological effects involve lethal and temporary or 
permanent sub-lethal injury. Physiological effects involve temporary 
and permanent primary and secondary stress responses, such as changes 
in levels of enzymes and proteins. Behavioral effects refer to 
temporary and (if they occur) permanent changes in exhibited behavior 
(e.g., startle and avoidance behavior). The three categories are 
interrelated in complex ways. For example, it is possible that certain 
physiological and behavioral changes could potentially lead to an 
ultimate pathological effect on individuals (i.e., mortality).
    The specific received sound levels at which permanent adverse 
effects to fish potentially could occur are little studied and largely 
unknown. Furthermore, the available information on the impacts of 
seismic surveys on marine fish is from studies of individuals or 
portions of a population; there have been no studies at the population 
scale. The studies of individual fish have often been on caged fish 
that were exposed to airgun pulses in situations not representative of 
an actual seismic survey. Thus, available information provides limited 
insight on possible real-world effects at the ocean or population 
scale.
    Hastings and Popper (2005), Popper (2009), and Popper and Hastings 
(2009a,b) provided recent critical reviews of the known effects of 
sound on fish. The following sections provide a general synopsis of the 
available information on the effects of exposure to seismic and other 
anthropogenic sound as relevant to fish. The information comprises 
results from scientific studies of varying degrees of rigor plus some 
anecdotal information. Some of the data sources may have serious 
shortcomings in methods, analysis, interpretation, and reproducibility 
that must be considered when interpreting their results (see Hastings 
and Popper, 2005). Potential adverse effects of the program's sound 
sources on marine fish are then noted.
    Pathological Effects--The potential for pathological damage to 
hearing structures in fish depends on the energy level of the received 
sound and the physiology and hearing capability of the species in 
question (see Appendix D L-DEO's environmental analysis). For a given 
sound to result in hearing loss, the sound must exceed, by some 
substantial amount, the hearing threshold of the fish for that sound 
(Popper, 2005). The consequences of temporary or permanent hearing loss 
in individual fish on a fish population are unknown; however, they 
likely depend on the number of individuals affected and whether 
critical behaviors involving sound (e.g., predator avoidance, prey 
capture, orientation and navigation, reproduction, etc.) are adversely 
affected.
    Little is known about the mechanisms and characteristics of damage 
to fish that may be inflicted by exposure to seismic survey sounds. Few 
data have been presented in the peer-reviewed scientific literature. As 
far as we know, there are only two papers with proper experimental 
methods, controls, and careful pathological investigation implicating 
sounds produced by actual seismic survey airguns in causing adverse 
anatomical effects. One such study indicated anatomical damage, and the 
second indicated TTS in fish hearing. The anatomical case is McCauley 
et al. (2003), who found that exposure to airgun sound caused 
observable anatomical damage to the auditory maculae of pink snapper 
(Pagrus auratus). This damage in the ears had not been repaired in fish 
sacrificed and examined almost two months after exposure. On the other 
hand, Popper et al. (2005) documented only TTS (as determined by 
auditory brainstem response) in two of three fish species from the 
Mackenzie River Delta. This study found that broad whitefish (Coregonus 
nasus) that exposed to five airgun shots were not significantly 
different from those of controls. During both studies, the repetitive 
exposure to sound was greater than would have occurred during a typical 
seismic survey. However, the substantial low-frequency energy produced 
by the airguns [less than 400 Hz in the study by McCauley et al. (2003) 
and less than approximately 200 Hz in Popper et al. (2005)] likely did 
not propagate to the fish because the water in the study areas was very 
shallow (approximately 9 m in the former case and less than two m in 
the latter). Water depth sets a lower limit on the lowest sound 
frequency that will propagate (the ``cutoff frequency'') at about one-
quarter wavelength (Urick, 1983; Rogers and Cox, 1988).
    Wardle et al. (2001) suggested that in water, acute injury and 
death of organisms exposed to seismic energy depends primarily on two 
features of the sound source: (1) The received peak pressure and (2) 
the time required for the pressure to rise and decay. Generally, as 
received pressure increases, the period for the pressure to rise and 
decay decreases, and the chance of acute pathological effects 
increases. According to Buchanan et al. (2004), for the types of 
seismic airguns and arrays involved with the proposed program, the 
pathological (mortality) zone for fish would be expected to be within a 
few meters of the seismic source. Numerous other studies provide 
examples of no fish mortality upon exposure to seismic sources (Falk 
and Lawrence, 1973; Holliday et al., 1987; La Bella et al., 1996; 
Santulli et al., 1999; McCauley et al., 2000a,b, 2003; Bjarti, 2002; 
Thomsen, 2002; Hassel et al., 2003; Popper et al., 2005; Boeger et al., 
2006).
    Some studies have reported, some equivocally, that mortality of 
fish, fish eggs, or larvae can occur close to seismic sources 
(Kostyuchenko, 1973; Dalen and Knutsen, 1986; Booman et al., 1996; 
Dalen et al., 1996). Some of the reports claimed seismic effects from 
treatments quite different from actual seismic survey sounds or even 
reasonable surrogates. However, Payne et al. (2009) reported no 
statistical differences in mortality/morbidity between control and 
exposed groups of capelin eggs or monkfish larvae. Saetre and Ona 
(1996) applied a `worst-case scenario' mathematical model to 
investigate the effects of seismic energy on fish eggs and larvae. They 
concluded that mortality rates caused by exposure to seismic surveys 
are so low, as compared to natural mortality rates, that the impact of 
seismic surveying on recruitment to a fish stock must be regarded as 
insignificant.
    Physiological Effects--Physiological effects refer to cellular and/
or biochemical responses of fish to acoustic stress. Such stress 
potentially could affect fish populations by increasing mortality or 
reducing reproductive success. Primary and secondary stress responses 
of fish after exposure to seismic survey sound appear to be temporary 
in all studies done to date (Sverdrup et al., 1994; Santulli et al., 
1999; McCauley et al., 2000a,b). The periods necessary for the 
biochemical changes to return to normal are variable and depend on 
numerous aspects of the biology of the species and of the sound 
stimulus (see Appendix D of L-DEO's environmental analysis).
    Behavioral Effects--Behavioral effects include changes in the 
distribution, migration, mating, and catchability of fish populations. 
Studies investigating the possible effects of sound (including seismic 
survey sound) on fish behavior have been conducted on both uncaged and 
caged individuals (e.g., Chapman and Hawkins, 1969; Pearson et al., 
1992;

[[Page 6442]]

Santulli et al., 1999; Wardle et al., 2001; Hassel et al., 2003). 
Typically, in these studies fish exhibited a sharp startle response at 
the onset of a sound followed by habituation and a return to normal 
behavior after the sound ceased.
    There is general concern about potential adverse effects of seismic 
operations on fisheries, namely a potential reduction in the 
``catchability'' of fish involved in fisheries. Although reduced catch 
rates have been observed in some marine fisheries during seismic 
testing, in a number of cases the findings are confounded by other 
sources of disturbance (Dalen and Raknes, 1985; Dalen and Knutsen, 
1986; Lokkeborg, 1991; Skalski et al., 1992; Engas et al., 1996). In 
other airgun experiments, there was no change in catch per unit effort 
(CPUE) of fish when airgun pulses were emitted, particularly in the 
immediate vicinity of the seismic survey (Pickett et al., 1994; La 
Bella et al., 1996). For some species, reductions in catch may have 
resulted from a change in behavior of the fish, e.g., a change in 
vertical or horizontal distribution, as reported in Slotte et al. 
(2004).
    In general, any adverse effects on fish behavior or fisheries 
attributable to seismic testing may depend on the species in question 
and the nature of the fishery (season, duration, fishing method). They 
may also depend on the age of the fish, its motivational state, its 
size, and numerous other factors that are difficult, if not impossible, 
to quantify at this point, given such limited data on effects of 
airguns on fish, particularly under realistic at-sea conditions.

Anticipated Effects on Invertebrates

    The existing body of information on the impacts of seismic survey 
sound on marine invertebrates is very limited. However, there is some 
unpublished and very limited evidence of the potential for adverse 
effects on invertebrates, thereby justifying further discussion and 
analysis of this issue. The three types of potential effects of 
exposure to seismic surveys on marine invertebrates are pathological, 
physiological, and behavioral. 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 E of L-DEO's environmental analysis).
    The only information available on the impacts of seismic surveys on 
marine invertebrates involves studies of individuals; there have been 
no studies at the population scale. Thus, available information 
provides limited insight on possible real-world effects at the regional 
or ocean scale. The most important aspect of potential impacts concerns 
how exposure to seismic survey sound ultimately affects invertebrate 
populations and their viability, including availability to fisheries.
    Literature reviews of the effects of seismic and other underwater 
sound on invertebrates were provided by Moriyasu et al. (2004) and 
Payne et al. (2008). The following sections provide a synopsis of 
available information on the effects of exposure to seismic survey 
sound on species of decapod crustaceans and cephalopods, the two 
taxonomic groups of invertebrates on which most such studies have been 
conducted. The available information is from studies with variable 
degrees of scientific soundness and from anecdotal information. A more 
detailed review of the literature on the effects of seismic survey 
sound on invertebrates is provided in Appendix E of L-DEO's 
environmental analysis.
    Pathological Effects--In water, lethal and sub-lethal injury to 
organisms exposed to seismic survey sound appears to depend on at least 
two features of the sound source: (1) The received peak pressure; and 
(2) the time required for the pressure to rise and decay. Generally, as 
received pressure increases, the period for the pressure to rise and 
decay decreases, and the chance of acute pathological effects 
increases. For the type of airgun array planned for the proposed 
program, the pathological (mortality) zone for crustaceans and 
cephalopods is expected to be within a few meters of the seismic 
source, at most; however, very few specific data are available on 
levels of seismic signals that might damage these animals. This premise 
is based on the peak pressure and rise/decay time characteristics of 
seismic airgun arrays currently in use around the world.
    Some studies have suggested that seismic survey sound has a limited 
pathological impact on early developmental stages of crustaceans 
(Pearson et al., 1994; Christian et al., 2003; DFO, 2004). However, the 
impacts appear to be either temporary or insignificant compared to what 
occurs under natural conditions. Controlled field experiments on adult 
crustaceans (Christian et al., 2003, 2004; DFO, 2004) and adult 
cephalopods (McCauley et al., 2000a,b) exposed to seismic survey sound 
have not resulted in any significant pathological impacts on the 
animals. It has been suggested that exposure to commercial seismic 
survey activities has injured giant squid (Guerra et al., 2004), but 
the article provides little evidence to support this claim.
    Physiological Effects--Physiological effects refer mainly to 
biochemical responses by marine invertebrates to acoustic stress. Such 
stress potentially could affect invertebrate populations by increasing 
mortality or reducing reproductive success. Primary and secondary 
stress responses (i.e., changes in haemolymph levels of enzymes, 
proteins, etc.) of crustaceans have been noted several days or months 
after exposure to seismic survey sounds (Payne et al., 2007). The 
periods necessary for these biochemical changes to return to normal are 
variable and depend on numerous aspects of the biology of the species 
and of the sound stimulus.
    Behavioral Effects--There is increasing interest in assessing the 
possible direct and indirect effects of seismic and other sounds on 
invertebrate behavior, particularly in relation to the consequences for 
fisheries. Changes in behavior could potentially affect such aspects as 
reproductive success, distribution, susceptibility to predation, and 
catchability by fisheries. Studies investigating the possible 
behavioral effects of exposure to seismic survey sound on crustaceans 
and cephalopods have been conducted on both uncaged and caged animals. 
In some cases, invertebrates exhibited startle responses (e.g., squid 
in McCauley et al., 2000a,b). In other cases, no behavioral impacts 
were noted (e.g., crustaceans in Christian et al., 2003, 2004; DFO 
2004). There have been anecdotal reports of reduced catch rates of 
shrimp shortly after exposure to seismic surveys; however, other 
studies have not observed any significant changes in shrimp catch rate 
(Andriguetto-Filho et al., 2005). Similarly, Parry and Gason (2006) did 
not find any evidence that lobster catch rates were affected by seismic 
surveys. Any adverse effects on crustacean and cephalopod behavior or 
fisheries attributable to seismic survey sound depend on the species in 
question and the nature of the fishery (season, duration, fishing 
method).

Proposed Mitigation

    In order to issue an incidental take authorization (ITA) under 
Section 101(a)(5)(D) of the MMPA, NMFS must 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

[[Page 6443]]

grounds, and areas of similar significance, and the availability of 
such species or stock for taking for certain subsistence uses.
    L-DEO has based the mitigation measures described herein, to be 
implemented for the proposed seismic survey, on the following:
    (1) Protocols used during previous L-DEO seismic research cruises 
as approved by NMFS;
    (2) previous IHA applications and IHAs approved and authorized by 
NMFS; and
    (3) recommended best practices in Richardson et al. (1995), Pierson 
et al. (1998), and Weir and Dolman (2007).
    To reduce the potential for disturbance from acoustic stimuli 
associated with the activities, L-DEO and/or its designees has proposed 
to implement the following mitigation measures for marine mammals:
    (1) Proposed exclusion zones;
    (2) power-down procedures;
    (3) shutdown procedures; and
    (4) ramp-up procedures.
    Proposed Exclusion Zones-L-DEO uses safety radii to designate 
exclusion zones and to estimate take (described in greater detail in 
Section IV and Appendix A of L-DEO's environmental analysis) for marine 
mammals. Table 1 shows the distances at which two sound levels (160- 
and 180-dB) are expected to be received from the 18-airgun subarray and 
a single airgun. The 180-dB level shut-down criterion is applicable to 
cetaceans, as specified by NMFS (2000); and L-DEO used these levels to 
establish the EZs. If the protected species visual observer (PSVO) 
detects marine mammal(s) within or about to enter the appropriate EZ, 
the Langseth crew will immediately power down the airgun subarrays, or 
perform a shut down if necessary (see Shut-down Procedures).
    Power-down Procedures-A power-down involves decreasing the number 
of airguns in use such that the radius of the 180-dB zone is decreased 
to the extent that marine mammals are no longer in or about to enter 
the EZ. A power down of the airgun subarray can also occur when the 
vessel is moving from one seismic line to another. During a power-down 
for mitigation, L-DEO will operate one airgun. The continued operation 
of one airgun is intended to alert marine mammals to the presence of 
the seismic vessel in the area. In contrast, a shut down occurs when 
the Langseth suspends all airgun activity.
    If the PSVO detects a marine mammal outside the EZ, but it is 
likely to enter the EZ, L-DEO will power down the airguns before the 
animal is within the EZ. Likewise, if a mammal is already within the 
EZ, when first detected L-DEO will power down the airguns immediately. 
During a power down of the airgun array, L-DEO will also operate the 
40-in\3\ airgun. If a marine mammal is detected within or near the 
smaller EZ around that single airgun (Table 1), L-DEO will shut down 
the airgun (see next section).
    Following a power-down, L-DEO will not resume airgun activity until 
the marine mammal has cleared the safety zone. L-DEO will consider the 
animal to have cleared the EZ if
     a PSVO has visually observed the animal leave the EZ, or
     a PSVO has not sighted the animal within the EZ for 15 min 
for small odontocetes, or 30 min for mysticetes and large odontocetes, 
including sperm, pygmy sperm, dwarf sperm, and beaked whales.
    During airgun operations following a power-down (or shut-down) 
whose duration has exceeded the time limits specified previously, L-DEO 
will ramp-up the airgun array gradually (see Shut-down Procedures).
    Shut-down Procedures--L-DEO will shut down the operating airgun(s) 
if a marine mammal is seen within or approaching the EZ for the single 
airgun. L-DEO will implement a shut-down:
    (1) if an animal enters the EZ of the single airgun after L-DEO has 
initiated a power down, or
    (2) if an animal is initially seen within the EZ of the single 
airgun when more than one airgun (typically the full airgun array) is 
operating.
    L-DEO will not resume airgun activity until the marine mammal has 
cleared the EZ, or until the PSVO is confident that the animal has left 
the vicinity of the vessel. Criteria for judging that the animal has 
cleared the EZ will be as described in the preceding section.
    Ramp-up Procedures--L-DEO will follow a ramp-up procedure when the 
airgun subarrays begin operating after a specified period without 
airgun operations or when a power down has exceeded that period. L-DEO 
proposes that, for the present cruise, this period would be 
approximately eight min. This period is based on the 180-dB radius for 
the 18-airgun subarray towed at a depth of seven m (23 ft) in relation 
to the minimum planned speed of the Langseth while shooting (8.5 km/h; 
5.3 mph; 4.6 kts). L-DEO has used similar periods (8-10 min) during 
previous L-DEO surveys.
    Ramp-up will begin with the smallest airgun in the array (40-
in\3\). Airguns will be added in a sequence such that the source level 
of the array will increase in steps not exceeding six dB per five-
minute period over a total duration of approximately 30 min. During 
ramp-up, the PSVOs will monitor the EZ, and if marine mammals are 
sighted, L-DEO will implement a power down or shut down as though the 
full airgun array were operational.
    If the complete EZ has not been visible for at least 30 min prior 
to the start of operations in either daylight or nighttime, L-DEO will 
not commence the ramp-up unless at least one airgun (40-in\3\ or 
similar) has been operating during the interruption of seismic survey 
operations. Given these provisions, it is likely that the airgun array 
will not be ramped up from a complete shut down at night or in thick 
fog, because the outer part of the safety zone for that array will not 
be visible during those conditions. If one airgun has operated during a 
power-down period, ramp-up to full power will be permissible at night 
or in poor visibility, on the assumption that marine mammals will be 
alerted to the approaching seismic vessel by the sounds from the single 
airgun and could move away. L-DEO will not initiate a ramp-up of the 
airguns if a marine mammal is sighted within or near the applicable EZs 
during the day or close to the vessel at night.
    NMFS has carefully evaluated the applicant's proposed mitigation 
measures and has considered a range of other measures in the context of 
ensuring that NMFS prescribes the means of effecting the least 
practicable adverse 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: (1) 
The manner in which, and the degree to which, the successful 
implementation of the measure is expected to minimize adverse impacts 
to marine mammals; (2) the proven or likely efficacy of the specific 
measure to minimize adverse impacts as planned; and (3) 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 or recommended by the public, 
NMFS has preliminarily determined that the proposed mitigation measures 
provide the means of effecting the least practicable adverse impacts on 
marine mammals species or stocks and their habitat, paying particular 
attention to rookeries, mating grounds, and areas of similar 
significance.

[[Page 6444]]

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 IHAs 
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 action area.

Monitoring

    L-DEO 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. L-DEO's proposed Monitoring Plan is 
described below this section. L-DEO understands that this monitoring 
plan will be subject to review by NMFS, and that refinements may be 
required. 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. L-
DEO 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

    PSVOs will be based aboard the seismic source vessel and will watch 
for marine mammals near the vessel during daytime airgun operations and 
during any start-ups at night. PSVOs will also watch for marine mammals 
near the seismic vessel for at least 30 min prior to the start of 
airgun operations after an extended shut down.
    PSVOs will conduct observations during daytime periods when the 
seismic system is not operating for comparison of sighting rates and 
behavior with and without airgun operations and between acquisition 
periods. Based on PSVO observations, the airguns will be powered down 
or shut down when marine mammals are observed within or about to enter 
a designated EZ. The EZ is a region in which a possibility exists of 
adverse effects on animal hearing or other physical effects.
    During seismic operations off Costa Rica, at least three PSVOs will 
be based aboard the Langseth. L-DEO will appoint the PSVOs with NMFS' 
concurrence. During all daytime periods, two PSVOs will be on duty from 
the observation tower to monitor and PSVOs will be on duty in shifts of 
duration no longer than four hours.
    During mealtimes it is sometimes difficult to have two PSVOs on 
effort, but at least one PSVO will be on watch during bathroom breaks 
and mealtimes. Use of two simultaneous observers increases the 
effectiveness of detecting animals near the source vessel. However, 
during meal times, only one PSVO may be on duty.
    Two PSVOs will also be on visual watch during all nighttime start-
ups of the seismic airguns. A third PSVO will monitor the PAM equipment 
24 hours a day to detect vocalizing marine mammals present in the 
action area. In summary, a typical daytime cruise would have scheduled 
two PSVOs on duty from the observation tower, and a third PSVO on PAM.
    L-DEO will also instruct other crew to assist in detecting marine 
mammals and implementing mitigation requirements (if practical). Before 
the start of the seismic survey, L-DEO will give the crew additional 
instruction regarding how to accomplish this task.
    The Langseth is a suitable platform for marine mammal observations. 
When stationed on the observation platform, the eye level will be 
approximately 21.5 m (70.5 ft) above sea level, and the observer will 
have a good view around the entire vessel. During daytime, the PSVOs 
will scan the area around the vessel systematically with reticle 
binoculars (e.g., 7 x 50 Fujinon), Big-eye binoculars (25 x 150), and 
with the naked eye. During darkness, night vision devices (NVDs) will 
be available (ITT F500 Series Generation 3 binocular-image intensifier 
or equivalent), when required. Laser range-finding binoculars (Leica 
LRF 1200 laser rangefinder or equivalent) will be available to assist 
with distance estimation. Those are useful in training observers to 
estimate distances visually, but are generally not useful in measuring 
distances to animals directly; that is done primarily with the reticles 
in the binoculars.

Passive Acoustic Monitoring

    Passive Acoustic Monitoring (PAM) will complement the visual 
monitoring program, when practicable. Visual monitoring typically is 
not effective during periods of poor visibility or at night, and even 
with good visibility, is unable to detect marine mammals when they are 
below the surface or beyond visual range.
    Besides the three PSVOs, an additional acoustic Protected Species 
Observer (PSO) with primary responsibility for PAM will also be aboard 
the vessel. L-DEO can use acoustical monitoring in addition to visual 
observations to improve detection, identification, and localization of 
cetaceans. The acoustic monitoring will serve to alert visual observers 
(if on duty) when vocalizing cetaceans are detected. It is only useful 
when marine mammals call, but it can be effective either by day or by 
night, and does not depend on good visibility. It will be monitored in 
real time so that the visual observers can be advised when cetaceans 
are detected. When bearings (primary and mirror-image) to calling 
cetacean(s) are determined, the bearings will be relayed to the visual 
observer to help him/her sight the calling animal(s).
    The PAM system consists of hardware (i.e., hydrophones) and 
software. The ``wet end'' of the system consists of a towed hydrophone 
array that is connected to the vessel by a cable. The lead in from the 
hydrophone array is approximately 400 m (1,312 ft) long, the active 
section of the array is approximately 56 m (184 ft) long, and the 
hydrophone array is typically towed at depths of less than 20 m (66 
ft).
    The deck cable is connected from the array to a computer in the 
laboratory where signal conditioning and processing takes place. The 
digitized signal is then sent to the main laboratory, where the 
acoustic PSO monitors the system.
    Ideally, the acoustic PSO will monitor the towed hydrophones 24 h 
per day during airgun operations and during most periods when the 
Langseth is underway while the airguns are not operating. However, PAM 
may not be possible if damage occurs to both the primary and back-up 
hydrophone the arrays during operations. The primary PAM streamer on 
the Langseth is a digital hydrophone streamer. Should the digital 
streamer fail, back-up systems should include an analog spare streamer 
and a hull-mounted hydrophone. Every effort would be made to have a 
working PAM system during the cruise. In the unlikely event that all 
three of these systems were to fail, L-DEO would continue science 
acquisition with the visual-based observer program. The PAM system is a 
supplementary enhancement to the visual monitoring program. If weather 
conditions were to prevent the use of PAM then conditions would also 
likely prevent the use of the airgun array.
    One acoustic PSO will monitor the acoustic detection system at any 
one

[[Page 6445]]

time, by listening to the signals from two channels via headphones and/
or speakers and watching the real-time spectrographic display for 
frequency ranges produced by cetaceans. Acoustic PSOs monitoring the 
acoustical data will be on shift for one to six hours at a time. 
Besides the PSVO, an additional acoustic PSO with primary 
responsibility for PAM will also be aboard the source vessel. All PSVOs 
are expected to rotate through the PAM position, although the most 
experienced with acoustics will be on PAM duty more frequently.
    When a vocalization is detected while visual observations are in 
progress, the acoustic PSO will contact the visual PSVO immediately, to 
alert him/her to the presence of cetaceans (if they have not already 
been seen), and to allow a power down or shut down to be initiated, if 
required. The information regarding the call will be entered into a 
database. Data entry will include an acoustic encounter identification 
number, whether it was linked with a visual sighting, date, time when 
first and last heard and whenever any additional information was 
recorded, position and water depth when first detected, bearing if 
determinable, species or species group (e.g., unidentified dolphin, 
sperm whale), types and nature of sounds heard (e.g., clicks, 
continuous, sporadic, whistles, creaks, burst pulses, strength of 
signal, etc.), and any other notable information. The acoustic 
detection can also be recorded for further analysis.

PSVO Data and Documentation

    PSVOs will record data to estimate the numbers of marine mammals 
exposed to various received sound levels and to document apparent 
disturbance reactions or lack thereof. Data will be used to estimate 
numbers of animals potentially `taken' by harassment (as defined in the 
MMPA). They will also provide information needed to order a power down 
or shut down of the airguns when a marine mammal is within or near the 
EZ.
    When a sighting is made, the following information about the 
sighting will be recorded:
    1. Species, group size, age/size/sex categories (if determinable), 
behavior when first sighted and after initial sighting, heading (if 
consistent), bearing and distance from seismic vessel, sighting cue, 
apparent reaction to the airguns or vessel (e.g., none, avoidance, 
approach, paralleling, etc.), and behavioral pace.
    2. Time, location, heading, speed, activity of the vessel, sea 
state, visibility, and sun glare.
    The data listed under (2) will also be recorded at the start and 
end of each observation watch, and during a watch whenever there is a 
change in one or more of the variables.
    All observations and power downs or shut downs will be recorded in 
a standardized format. Data will be entered into an electronic 
database. The accuracy of the data entry will be verified by 
computerized data validity checks as the data are entered and by 
subsequent manual checking of the database. These procedures will allow 
initial summaries of data to be prepared during and shortly after the 
field program, and will facilitate transfer of the data to statistical, 
graphical, and other programs for further processing and archiving.
    Results from the vessel-based observations will provide:
    1. The basis for real-time mitigation (airgun power down or shut 
down).
    2. Information needed to estimate the number of marine mammals 
potentially taken by harassment, which must be reported to NMFS.
    3. Data on the occurrence, distribution, and activities of marine 
mammals and turtles in the area where the seismic study is conducted.
    4. Information to compare the distance and distribution of marine 
mammals and turtles relative to the source vessel at times with and 
without seismic activity.
    5. Data on the behavior and movement patterns of marine mammals 
seen at times with and without seismic activity.
    L-DEO will submit a report to NMFS and NSF within 90 days after the 
end of the cruise. The report will describe the operations that were 
conducted and sightings of marine mammals and turtles near the 
operations. The report will provide 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 number and nature of exposures that could result in 
``takes'' of marine mammals by harassment or in other ways.
    L-DEO will report all injured or dead marine mammals (regardless of 
cause) to NMFS as soon as practicable. The report should include the 
species or description of the animal, the condition of the animal, 
location, time first found, observed behaviors (if alive) and photo or 
video, if available.

Estimated Take by Incidental Harassment

    Except with respect to certain activities not pertinent here, the 
MMPA defines ``harassment'' as:

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

    Only take by Level B harassment is anticipated and authorized as a 
result of the proposed marine geophysical survey off Costa Rica. 
Acoustic stimuli (i.e., increased underwater sound) generated during 
the operation of the seismic airgun array, may have the potential to 
cause marine mammals in the survey area to be exposed to sounds at or 
greater than 160 decibels (dB) or cause temporary, short-term changes 
in behavior. There is no evidence that the planned activities could 
result in injury, serious injury or mortality within the specified 
geographic area for which L-DEO seeks the IHA. The required mitigation 
and monitoring measures will minimize any potential risk for injury or 
mortality.
    The following sections describe L-DEO's methods to estimate take by 
incidental harassment and present the applicant's estimates of the 
numbers of marine mammals that could be affected during the proposed 
geophysical survey. The estimates are based on a consideration of the 
number of marine mammals that could be disturbed appreciably by 
operations with the 18-airgun subarray to be used during approximately 
2,145 km (1,333 mi) of survey lines with an additional 365 km (227 mi) 
of turns.
    L-DEO assumes that, during simultaneous operations of the airgun 
array and the other sources, any marine mammals close enough to be 
affected by the MBES and SBP would already be affected by the airguns. 
However, whether or not the airguns 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 previously. Such reactions are not considered 
to constitute ``taking'' (NMFS, 2001). Therefore, L-DEO provides no 
additional allowance for animals that could be affected by sound 
sources other than airguns.

[[Page 6446]]

    Density data on the marine mammal species in the proposed survey 
area are available from extensive ship-based surveys for marine mammals 
in the ETP conducted by NMFS' Southwest Fisheries Science Center 
(SWFSC). L-DEO used densities from two sources: (1) The SWFSC's habitat 
models that predict density for 15 cetacean species in the ETP; and (2) 
densities from the surveys conducted during summer and fall 1986-1996, 
as summarized by Ferguson and Barlow (2001, 2003) for species sighted 
in SWFSC surveys whose sample sizes were too small to model density.
    For the predictive models, the SWFSC developed habitat modeling as 
a method to estimate cetacean densities on a finer spatial scale 
compared to 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 SWFSC 
incorporated the models into a web-based Geographic Information System 
(GIS) developed by Duke University's Department of Defense Strategic 
Environmental Research and Development Program (SERDP) team and L-DEO 
used the GIS to obtain mean and maximum densities for 11 cetacean 
species in the model in the proposed survey area.
    For the second source, L-DEO used the densities calculated from 
Ferguson and Barlow (2003) for 5[deg] x 5[deg] blocks that include the 
proposed survey area (Block 138) and blocks adjacent to 138 that 
include coastal waters: Blocks 119, 137, 138, 139, 158, and 159. Those 
blocks included 18,385 km (11,423 mi) of survey effort in Beaufort sea 
states 0-5, and 3,899 square kilometers (km\2\) (1,505 square miles 
(mi\2\)) of survey effort in Beaufort sea states 0-2. L-DEO also 
obtained densities for an additional seven species that were sighted in 
one or more of those blocks.
    For two endangered species for which there are only unconfirmed 
sightings in the region, the sei and fin whales, L-DEO assigned low 
density values (equal to the density of the species with the lowest 
calculated density). The false killer whale has been sighted near the 
survey area but not in the seven blocks of Ferguson and Barlow (2003), 
so it was also assigned the same low density value.
    Oceanographic conditions, including occasional El Ni[ntilde]o and 
La Ni[ntilde]a 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 (e.g., Escorza-Trevi[ntilde]o, 2009). Thus, for some species 
the densities derived from recent surveys may not be representative of 
the densities that will be encountered during the proposed seismic 
survey. Table 2 includes L-DEO's estimates of the ``best'' and 
``maximum'' densities of marine mammals in the ETP near the proposed 
survey area. For the modeled species, best estimates and maximum 
estimates of density in the survey area are the mean and maximum 
densities given in Read et al. (2009). For the other species, best 
estimates of density are the effort-weighted mean densities in the 
seven 5[deg] x 5[deg] blocks from Ferguson and Barlow (2001, 2003), and 
maximum estimates of density are the highest densities in any of the 
blocks.
    L-DEO's estimates of exposures to various sound levels assume that 
the proposed surveys will be completed. As is typical during offshore 
ship surveys, inclement weather and equipment malfunctions are likely 
to cause delays and may limit the number of useful line-kilometers of 
seismic operations that can be undertaken. L-DEO has included an 
additional 25% of line transects to account for mission uncertainty and 
follow a precautionary approach. Furthermore, any marine mammal 
sightings within or near the designated exclusion zones will result in 
the power down or shut down of seismic operations as a mitigation 
measure. Thus, the following estimates of the numbers of marine mammals 
potentially exposed to sound levels of 160 dB re: 1 [micro]Pa are 
precautionary and probably overestimate the actual numbers of marine 
mammals that might be involved. These estimates also assume that there 
will be no weather, equipment, or mitigation delays, which is highly 
unlikely.
    L-DEO estimated the number of different individuals that may be 
exposed to airgun sounds with received levels greater than or equal to 
160 dB re: 1 [micro]Pa on one or more occasions by considering the 
total marine area that would be within the 160-dB radius around the 
operating airgun array on at least one occasion and the expected 
density of marine mammals. The number of possible exposures (including 
repeated exposures of the same individuals) can be estimated by 
considering the total marine area that would be within the 160-dB 
radius around the operating airguns, including areas of overlap. In the 
proposed survey, the seismic lines are parallel and in close proximity; 
thus individuals could be exposed on two or more occasions. The area 
including overlap is 31.9 times the area excluding overlap. Thus a 
marine mammal that stayed in the survey area during the entire survey 
could be exposed 32 times (14 times), on average. Given the pattern of 
the seismic lines, the interval between exposures of a stationary 
animal would be approximately 18 hr. Moreover, it is unlikely that a 
particular animal would stay in the area during the entire survey. The 
number of different individuals potentially exposed to received levels 
greater than or equal to 160 re: 1 [micro]Pa was calculated by 
multiplying:
    (1) The expected species density, either ``mean'' (i.e., best 
estimate) or ``maximum'', times
    (2) the anticipated area to be ensonified to that level during 
airgun operations excluding overlap, which is approximately 3,225 km\2\ 
(2,003 mi\2\).
    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) around each seismic line, and then calculating the total area within 
the buffers. Areas of overlap were included only once when estimating 
the number of individuals exposed. Applying this approach, 
approximately 3,225 km\2\ (1,245 mi\2\) would be within the 160-dB 
isopleth on one or more occasions during the survey. Because this 
approach does not allow for turnover in the mammal populations in the 
study area during the course of the survey, the actual number of 
individuals exposed could be underestimated. However, the approach 
assumes that no cetaceans will move away from or toward the trackline 
as the Langseth approaches in response to increasing sound levels prior 
to the time the levels reach 160 dB, which will result in overestimates 
for those species known to avoid seismic vessels.
    Table 3 shows the best and maximum estimates of the number 
individual cetaceans that potentially could be exposed to greater than 
or equal to 160 dB re: 1 [mu]Pa during the seismic survey if no animals 
moved away from the survey vessel. The requested take authorization, 
given in the far right column of Table 3, is based on the maximum 
estimates rather than the best estimates of the numbers of individuals 
exposed, because of uncertainties associated with applying density data 
from one area to another.
    The total `maximum estimate' of the number of individual cetaceans 
that could be exposed to seismic sounds with received levels greater 
than or equal to 160 dB re: 1 [mu]Pa during the proposed survey is 
7,078 (see Table 3 below this section). That total includes 38 baleen 
whales, four of which are endangered: 18 humpback whales or 1.2

[[Page 6447]]

percent of the regional population; one sei whale, one fin whale (less 
than 0.01 percent); and eight blue whales (0.6 percent). In addition, 
40 sperm whales (also listed as endangered under the ESA) or 0.15 
percent of the regional population could be exposed during the survey, 
and 19 beaked whales. Most (97 percent) of the cetaceans that could be 
potentially exposed are delphinids (e.g., short-beaked common, striped, 
pantropical spotted, striped and spinner dolphins) with maximum 
estimates ranging from two to 3,077 exposed to levels greater than or 
equal to 160 dB re: 1 [mu]Pa.

  Table 3--Estimates of the Possible Numbers of Marine Mammals Exposed to Different Sound Levels During L-DEO's
                           Proposed Seismic Survey in the ETP During April-May, 2011.
----------------------------------------------------------------------------------------------------------------
                                          Estimated number  Estimated number
                                           of individuals    of individuals                        Approximate
                                          exposed to sound  exposed to sound   Requested take      percent of
                 Species                  levels >= 160 dB  levels >= 160 dB    authorization       regional
                                            re: 1 [mu]Pa      re: 1 [mu]Pa                       population \2\
                                             (Best \1\)       (Maximum \1\)                           (Max)
----------------------------------------------------------------------------------------------------------------
Humpback whale..........................                 1                18                18              1.29
Bryde's whale...........................                 4                10                10              0.08
Sei whale...............................                 0                 0             \3\ 1                NA
Fin whale...............................                 0                 0             \3\ 1              0.04
Blue whale..............................                 1                 8                 8              0.57
Sperm whale.............................                17                40                40              0.15
Pygmy/Dwarf sperm whale.................                 0                 0                 0              0.00
Cuvier's beaked whale...................                10                15                15              0.08
Mesoplodon spp..........................                 1                 4                 4              0.01
Rough-toothed dolphin...................                17                45                45              0.04
Bottlenose dolphin......................                69               366               366              0.11
Pantropical spotted dolphin.............               310               954               954              0.06
Spinner dolphin.........................               236             1,468              1468              0.08
Striped dolphin.........................               273               622               622              0.06
Short-beaked common dolphin.............               447             3,077              3077              0.10
Risso's dolphin.........................                51                91                91              0.08
Melon-headed whale......................                45               233           \3\ 258              0.57
Pygmy killer whale......................                 5                 9            \3\ 30              0.08
False killer whale......................                 0                 0                 0              0.00
Killer whale............................                 1                 2             \3\ 5              0.06
Short-finned pilot whale................                48               114               114              0.02
----------------------------------------------------------------------------------------------------------------
\1\ Best and maximum estimates are based on densities from Table 3 and ensonified areas (including 25%
  contingency) of 4030.63 for 160 dB and 1605.71 km\2\ for 170 dB (identified in parentheses). Takes are not
  anticipated for the minke whale and Fraser's dolphin.
\2\ Regional population size estimates are from Table 2; NA means not available.
\3\ Requested Take Authorization increased to mean group size in the ETP for baleen whales (Jackson et al. 2008)
  and delphinids (Ferguson et al. 2006).

Negligible Impact and Small Numbers Analysis and 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:
    (1) The number of anticipated mortalities;
    (2) the number and nature of anticipated injuries;
    (3) the number, nature, and intensity, and duration of Level B 
harassment; and
    (4) the context in which the takes occur.
    As mentioned previously, NMFS estimates that 19 species of marine 
mammals could be potentially affected by Level B harassment over the 
course of the IHA. For each species, these numbers are small (each, 
less than two percent) relative to the population size.
    No injuries, serious injuries or mortalities are anticipated to 
occur as a result of the L-DEO's planned marine geophysical survey, and 
none are authorized. Only short-term behavioral disturbance is 
anticipated to occur due to the brief and sporadic duration of the 
survey activities. No mortality or injury is expected to occur, and due 
to the nature, degree, and context of behavioral harassment 
anticipated, the activity is not expected to impact rates of 
recruitment or survival.
    NMFS has preliminarily determined, provided that the aforementioned 
mitigation and monitoring measures are implemented, that the impact of 
conducting a marine geophysical survey in the ETP off Costa Rica, April 
through May, 2011, may result, at worst, in a temporary modification in 
behavior and/or low-level physiological effects (Level B harassment) of 
small numbers of certain species of marine mammals.
    While behavioral modifications, including temporarily vacating the 
area during the operation of the airgun(s), may be made by these 
species to avoid the resultant acoustic disturbance, the availability 
of alternate areas within these areas and the short and sporadic 
duration of the research activities, have led NMFS to preliminary 
determine that this action will have a negligible impact on the species 
in the specified geographic region.
    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 L-DEO's planned research 
activities, will result in the incidental take of small numbers of 
marine mammals, by Level B harassment only, and that the total taking 
from the marine geophysical survey will have a negligible impact on the 
affected species or stocks.

[[Page 6448]]

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

    There are no relevant subsistence uses of marine mammals implicated 
by this action.

Endangered Species Act

    Of the species of marine mammals that may occur in the proposed 
survey area, five are listed as endangered under the ESA, including the 
humpback, sei, fin, blue, and sperm whales. Under Section 7 of the ESA, 
NSF has initiated formal consultation with the NMFS, Office of 
Protected Resources, Endangered Species Division, on this proposed 
seismic survey. NMFS' Office of Protected Resources, Permits, 
Conservation and Education Division, has initiated formal consultation 
under section 7 of the ESA with NMFS' Office of Protected Resources, 
Endangered Species Division, to obtain a Biological Opinion evaluating 
the effects of issuing the IHA on threatened and endangered marine 
mammals and, if appropriate, authorizing incidental take. NMFS will 
conclude formal section 7 consultation prior to making a determination 
on whether or not to issue the IHA. If the IHA is issued, L-DEO, in 
addition to the mitigation and monitoring requirements included in the 
IHA, will be required to comply with the Terms and Conditions of the 
Incidental Take Statement corresponding to NMFS' Biological Opinion 
issued to both NSF and NMFS' Office of Protected Resources.

National Environmental Policy Act (NEPA)

    To meet NMFS' National Environmental Policy Act (NEPA; 42 U.S.C. 
4321 et seq.) requirements for the issuance of an IHA to L-DEO, NMFS 
will prepare an Environmental Assessment (EA) titled ``Issuance of an 
Incidental Harassment Authorization to the Lamont-Doherty Earth 
Observatory to Take Marine Mammals by Harassment Incidental to a Marine 
Geophysical Survey in the Pacific Ocean off Costa Rica, April-May, 
2011.'' This EA will incorporate the NSF's Environmental Analysis 
Pursuant To Executive Order 12114 (NSF, 2010) and an associated report 
(Report) prepared by LGL Limited Environmental Research Associates 
(LGL) for NSF, titled, ``Environmental Assessment of a Marine 
Geophysical Survey by the R/V Marcus G. Langseth in the Pacific Ocean 
off Costa Rica (LGL, 2010) (draft),'' by reference pursuant to 40 CFR 
1502.21 and NOAA Administrative Order (NAO) 216-6 Sec.  5.09(d). Prior 
to making a final decision on the IHA application, NMFS will make a 
decision of whether or not to issue a Finding of No Significant Impact 
(FONSI).

Preliminary Determinations

    NMFS has preliminarily determined that the impact of conducting the 
specific seismic survey activities described in this notice and the IHA 
request in the specific geographic region within the ETP off Costa Rica 
may result, at worst, in a temporary modification in behavior (Level B 
harassment) of small numbers of marine mammals. Further, NMFS has 
preliminarily determined that this activity is expected to result in a 
negligible impact on the affected species or stocks of marine mammals. 
The provision requiring that the activity not have an unmitigable 
impact on the availability of the affected species or stock of marine 
mammals for subsistence uses is not implicated for this proposed 
action.
    For reasons stated previously in this document, the specified 
activities associated with the proposed survey are not likely to cause 
TTS, PTS or other non-auditory injury, serious injury, or death to 
affected marine mammals because:
    (1) The likelihood that, given sufficient notice through relatively 
slow ship speed, marine mammals are expected to move away from a noise 
source that is annoying prior to its becoming potentially injurious;
    (2) The fact that cetaceans would have to be closer than 450 m 
(1,476 ft) in deep water when the 18-airgun subarray is in use at a 7 m 
(23 ft) tow depth from the vessel to be exposed to levels of sound 
believed to have even a minimal chance of causing PTS;
    (3) The fact that marine mammals would have to be closer than 3,800 
m (2.4 mi) in deep water when the full array is in use at a 7 m (23 ft) 
tow depth from the vessel to be exposed to levels of sound (160 dB) 
believed to have even a minimal chance at causing TTS; and
    (4) The likelihood that marine mammal detection ability by trained 
observers is high at that short distance from the vessel.
    As a result, no take by injury, serious injury, or death is 
presently anticipated nor would it be authorized were NMFS to issue a 
final IHA, and the potential for temporary or permanent hearing 
impairment is very low and would likely be avoided through the 
incorporation of the proposed monitoring and mitigation measures.
    While the number of marine mammals potentially incidentally 
harassed would depend on the distribution and abundance of marine 
mammals in the vicinity of the survey activity, the number of potential 
Level B incidental harassment takings (see Table 3 above this section) 
should a final IHA be issued is estimated to be small, less than two 
percent of any of the estimated population sizes based on the data 
disclosed in Table 2 of this notice. NMFS has preliminarily determined 
that impacts to affected species or stocks of marine mammals have been 
mitigated to the lowest level practicable through incorporation of the 
monitoring and mitigation measures mentioned previously in this 
document.

Proposed Authorization

    As a result of these preliminary determinations, NMFS proposes to 
issue an IHA to L-DEO for conducting a marine geophysical survey in the 
ETP off Costa Rica, provided the previously mentioned mitigation, 
monitoring, and reporting requirements are incorporated. The duration 
of the IHA would not exceed one year from the date of its issuance.

Information Solicited

    NMFS requests interested persons to submit comments and information 
concerning this proposed project and NMFS' preliminary determination of 
issuing an IHA (see ADDRESSES). Concurrent with the publication of this 
notice in the Federal Register, NMFS is forwarding copies of this 
application to the Marine Mammal Commission and its Committee of 
Scientific Advisors.

    Dated: January 31, 2011.
James H. Lecky,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. 2011-2538 Filed 2-3-11; 8:45 am]
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