[Federal Register Volume 76, Number 63 (Friday, April 1, 2011)]
[Notices]
[Pages 18167-18188]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-7487]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XA255


Takes of Marine Mammals Incidental to Specified Activities; 
Marine Geophysical Survey in the Central Gulf of Alaska, June, 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 the U.S. Geological 
Survey (USGS) for an Incidental Harassment Authorization (IHA) to take 
marine mammals, by harassment, incidental to conducting a marine 
geophysical survey in the central Gulf of Alaska (GOA), June, 2011. 
Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting 
comments on its proposal to issue an IHA to USGS to incidentally 
harass, by Level B harassment only, 9 species of marine mammals during 
the specified activity.

DATES: Comments and information must be received no later than May 2, 
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 email comments is [email protected]. NMFS is not 
responsible for e-mail comments sent to addresses other than the one 
provided here. Comments sent via email, 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 contact listed here (see FOR FURTHER INFORMATION 
CONTACT) or visiting the internet at: http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications.
    The U.S. Geological Survey (USGS), which is providing funding for 
the proposed action, has prepared a draft ``Environmental Assessment 
(EA) of a Marine Geophysical Survey by the R/V Marcus G. Langseth in 
the Central Gulf of Alaska, June 2011,'' prepared by LGL Ltd., 
Environmental Research Associates (LGL), on behalf of USGS, which 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: Howard Goldstein or Jolie Harrison, 
Office of Protected Resources, NMFS, (301) 713-2289, ext. 172.

SUPPLEMENTARY INFORMATION: 

Background

    Section 101(a)(5)(D) of the MMPA (16 U.S.C. 1371(a)(5)(D)) directs 
the Secretary of Commerce (Secretary) 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].

[[Page 18168]]

Summary of Request

    NMFS received an application on January 21, 2011, from USGS for the 
taking by harassment, of marine mammals, incidental to conducting a 
marine geophysical survey in the central GOA within the U.S. Exclusive 
Economic Zone (EEZ) and adjacent international waters in depths from 
approximately 2,000 meters (m) (6,561.7 feet [ft]) to greater than 
6,000 m (19,685 ft). USGS plans to conduct the proposed survey from 
approximately June 5 to 25, 2011.
    USGS plans to use one source vessel, the R/V Marcus G. Langseth 
(Langseth) and a seismic airgun array to collect seismic reflection and 
refraction profiles to be used to delineate the U.S. Extended 
Continental Shelf (ECS) in the GOA. In addition to the proposed 
operations of the seismic airgun array, USGS 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 USGS has requested an 
authorization to take 9 species of 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 21 days). 
It is likely that any marine mammal would be able to avoid the vessel.

Description of the Specified Activity

    USGS's proposed seismic survey in the central GOA is between 
approximately 200 to 650 kilometers (km) (108 to 351 nautical miles 
[nmi]) offshore in the area 53 to 57[deg] North, 135 to 148[deg] West 
(see Figure 1 of the IHA application). Water depths in the survey area 
range from approximately 2,000 m (6,561.7 ft) to greater than 6,000 m 
(19,685 ft). The project is scheduled to occur from approximately June 
5 to 25, 2011. Some minor deviation from these dates is possible, 
depending on logistics and weather. The proposed seismic survey will 
collect seismic reflection and refraction profiles to be used to 
delineate the U.S. ECS in the GOA. The ECS is the region beyond 200 nmi 
where a nation can show that it satisfies the conditions of Article 76 
of the United Nations Convention on the Law of the Sea. One of the 
conditions in Article 76 is a function of sediment thickness. The 
seismic profiles are designed to identify the stratigraphic 
``basement'' and to map the thickness of the overlying sediments. 
Acoustic velocities (required to convert measured travel times to true 
depth) will be measured directly using sonobuoys and ocean-bottom 
seismometers (OBSs), as well as by analysis of hydrophone streamer 
data. Acoustic velocity refers to the velocity of sound through 
sediments or crust.
    The survey will involve one source vessel, the Langseth. The 
Langseth will deploy an array of 36 airguns as an energy source. The 
receiving system will consist of one 8 km (4.3 nmi) long hydrophone 
streamer and/or five OBSs. As the airgun is towed along the survey 
lines, the hydrophone streamer will receive the returning acoustic 
signals and transfer the data to the on-board processing system. The 
OBSs record the returning acoustic signals internally for later 
analysis.
    The planned seismic survey (e.g., equipment testing, startup, line 
changes, repeat coverage of any areas, and equipment recovery) will 
consist of approximately 2,840 km (1,533.5 nmi) of transect lines in 
the central GOA survey area (see Figure 1 of the IHA application), with 
an additional 140 km (75.6 nmi) of turns. The array will be powered-
down to one 40 in\3\ airgun during turns. All of the survey will take 
place in water deeper than 1,000 m (3,280.8 ft). A multi-channel 
seismic (MCS) survey using the hydrophone streamer will take place 
along 17 MCS profile lines and 2 OBS lines. Following the MCS survey, 
five OBSs will be deployed and a refraction survey will take place 
along one of the 11 lines. If time permits, an additional 340 km (183.6 
nmi) contingency line will be added to the MCS survey. In addition to 
the operations of the airgun array, a Kongsberg EM 122 MBES and Knudsen 
320B SBP will also be operated from the Langseth continuously 
throughout the cruise. There will be additional seismic operations 
associated with equipment testing, start-up, and possible line changes 
or repeat coverage of any areas where initial data quality is sub-
standard. In USGS's calculations, 25% has been added for those 
additional operations.
    All planned geophysical data acquisition activities will be 
conducted by Lamont-Doherty Earth Observatory (L-DEO), the Langseth's 
operator, with on-board assistance by the scientists who have proposed 
the study. The Principal Investigators are Drs. Jonathan R. Childs and 
Ginger Barth of the USGS. The vessel will be self-contained, and the 
crew will live aboard the vessel for the entire cruise.

Vessel Specifications

    The Langseth, owned by the National Science Foundation, will tow 
the 36 airgun array, as well as the hydrophone streamer, along 
predetermined lines. The Langseth will also deploy and retrieve the 
OBSs. When the Langseth is towing the airgun array and the hydrophone 
streamer, the turning rate of the vessel is limited to five degrees per 
minute. Thus, the maneuverability of the vessel is limited during 
operations with the streamer.
    The vessel 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. 
The Langseth was designed as a seismic research vessel with a 
propulsion system designed to be as quiet as possible to avoid 
interference with the seismic signals emanating from the airgun array. 
The ship is powered by two 3,550 horsepower (hp) Bergen BRG-6 diesel 
engines which drive two propellers directly. 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 is typically 7.4 to 9.3 km per hour (hr) (km/hr) (4 to 5 
knots [kts]). When not towing seismic survey gear, the Langseth 
typically cruises at 18.5 km/hr (10 kts). The Langseth has a range of 
25,000 km (13,499 nmi) (the distance the vessel can travel without 
refueling).
    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, with a total volume of 
approximately 6,600 cubic inches (in\3\). The airgun array will consist 
of 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 airguns will be configured as four identical linear arrays or 
``strings.'' Each

[[Page 18169]]

string will have 10 airguns, the first and last airguns in the strings 
are spaced 16 m (52 ft) apart. Of the 10 airguns, nine airguns in each 
string will be fired simultaneously, whereas the tenth is kept in 
reserve as a spare, to be turned on in case of failure of another 
airgun. The four airgun strings will be distributed across an area of 
approximately 24x16 m (78.7x52.5 ft) behind the Langseth and will be 
towed approximately 100 m (328 ft) behind the vessel. The shot interval 
will be 50 m (164 ft) or approximately 22 seconds (s) for the MCS 
survey and 150 m (492.1 ft) or approximately 66 s for the OBS 
refraction survey. The firing pressure of the array is 1,900 pounds per 
square inch (psi). During firing, a brief (approximately 0.1 s) pulse 
sound is emitted. The airguns will be silent during the intervening 
periods. The dominant frequency components range from two to 188 Hertz 
(Hz).
    The tow depth of the array will be 9 m (29.5 ft) during OBS 
refraction and MCS surveys. Because the actual source is a distributed 
sound source (36 airguns) rather than a single point source, the 
highest sound measurable at any location in the water will be less than 
the nominal source level. In addition, the effective source level for 
sound propagating in near-horizontal directions will be substantially 
lower than the nominal source level applicable to downward propagation 
because of the directional nature of the sound from the airgun array.

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 USGS 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 36 airgun array 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 
USGS'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 USGS's EA discusses the characteristics of the airgun 
pulses and marine mammals. NMFS refers the reviewers to the application 
and EA 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 (EZs) for the 36 airgun array and the single airgun; to 
designate mitigation zones, and to estimate take 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.
    Using the corrected measurements (array) or model (single airgun), 
Table 1 (below) shows the distances at which three rms sound levels are 
expected to be received from the 36 airgun array and a single airgun. 
The 180 and 190 dB re 1 [micro]Pa (rms) distances are the safety 
criteria as specified by NMFS (2000) and are applicable to cetaceans 
and pinnipeds, respectively. If marine mammals are detected within or 
about to enter the appropriate EZ, the airguns will be powered-down (or 
shut-down, if necessary) immediately.
    Table 1 (below) summarizes the predicted distances at which sound 
levels (160, 180, and 190 dB [rms]) are expected to be received from 
the 36 airgun array and a single airgun operating in deep water depths.

 Table 1--Measured (Array) or Predicted (Single Airgun) Distances to Which Sound Levels >= 190, 180, and 160 dB
  re: 1 [mu]Pa (rms) Could be Received in Water Depths >1,000 m During the Proposed Survey in the Central GOA,
                                               June 5 to 25, 2011.
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                                                                                   Predicted RMS distances (m)
              Source and volume                           Water depth           --------------------------------
                                                                                   190 dB     180 dB     160 dB
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Single Bolt airgun (40 in\3\)................  Deep > 1,000 m..................         12         40        385
4 Strings 36 airguns (6,600 in\3\)...........  Deep > 1,000 m..................        400        940      3,850
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[[Page 18170]]

    Along with the airgun operations, two additional acoustical data 
acquisition systems will be operated during the survey. The ocean floor 
will be mapped with the Kongsberg EM 122 MBES and a Knudsen 320B SBP. 
These sound sources will be operated continuously from the Langseth 
throughout the cruise.

MBES

    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, usually 12 kHz) in a fan-shaped beam that extends downward 
and to the sides of the ship. The transmitting beamwidth is 1[deg] or 
2[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) or four (less than 1,000 m) successive, fan-
shaped transmissions, each ensonifying a sector that extends 1[deg] 
fore-aft. Continuous-wave pulses increase from 2 to 15 milliseconds 
(ms) long in water depths up to 2,600 m (8,530.2 ft), and FM chirp 
pulses up to 100 ms long are used in water greater than 2,600 m. The 
successive transmissions span an overall cross-track angular extent of 
about 150[deg], with 2 ms gaps between the pulses for successive 
sectors.

SBP

    The Langseth will also operate a Knudsen 320B SBP continuously 
throughout the cruise simultaneously with the MBES to map and provide 
information about the sedimentary features and bottom topography. The 
beam is transmitted as a 27[deg] cone, which is directed downward by a 
3.5 kHz transducer in the hull of the Langseth. 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 one second intervals 
followed by a five second pause.
    NMFS expects that acoustic stimuli resulting from the proposed 
operation of the single airgun or the 36 airgun array 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 knots [kts]; 8.5 km/hr; 5.3 mph) 
during seismic acquisition.

Description of the Proposed Dates, Duration, and Specified Geographic 
Region

    The survey will occur in the central GOA, between approximately 200 
and 650 km offshore, in the area 53 to 57[deg] North, 135 to 148[deg] 
West. The seismic survey will take place in water depths of 2,000 to 
greater than 6,000 m. The exact dates of the activities depend on 
logistics and weather conditions. The Langseth will depart from Dutch 
Harbor, Alaska on June 5, 2011, and return there on June 25, 2011. 
Seismic operations will be carried out for an estimated 12 to 14 days.

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

    Twenty-five marine mammal species (18 cetacean, 6 pinniped, and the 
sea otter) are known to or could occur in the GOA. Several 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 North Pacific 
right whale (Eubalaena japonica), humpback (Megaptera novaeangliae), 
sei (Balaenoptera borealis), fin (Balaenoptera physalus), blue 
(Balaenoptera musculus), and sperm (Physeter macrocephalus) whales, as 
well as the Cook Inlet distinct population segment (DPS) of beluga 
whales (Dephinapterus leucas) and the western stock of Steller sea 
lions (Eumetopias jubatus). The eastern stock of Steller sea lions is 
listed as threatened, as is the southwest Alaska DPS of the sea otter 
(Enhydra lutris).
    The marine mammals that occur in the proposed survey area belong to 
four taxonomic groups: odontocetes (toothed cetaceans, such as 
dolphins), mysticetes (baleen whales), pinnipeds (seals, sea lions, and 
walrus), and fissipeds (sea otter). Cetaceans and pinnipeds are the 
subject of the IHA application to NMFS. Walrus sightings are rare in 
the GOA. Sea otters generally inhabit nearshore areas inside the 40 m 
(131.2 ft) depth contour (Riedman and Estes, 1990) and likely would not 
be encountered in the deep, offshore waters of the study area. The sea 
otter and Pacific walrus are two marine mammal species mentioned in 
this document that are managed by the U.S. Fish and Wildlife Service 
(USFWS) and are not considered further in this analysis; all others are 
managed by NMFS. Coastal cetacean species (gray whales, beluga whales, 
and harbor porpoises) and pinniped species (California sea lions and 
harbor seals) likely would not be encountered in the deep, offshore 
waters of the survey area.
    Table 2 (below) presents information on the abundance, 
distribution, population status, conservation status, and density of 
the marine mammals that may occur in the proposed survey area during 
June, 2011.
BILLING CODE 3510-22-P

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[GRAPHIC] [TIFF OMITTED] TN01AP11.006

    Refer to Section III of USGS'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 USGS 
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 or more 
of the following: tolerance, masking of natural sounds, behavioral 
disturbance, temporary or permanent hearing impairment, or non-auditory 
physical or physiological effects (Richardson et al., 1995; Gordon et 
al., 2004; Nowacek et al., 2007; Southall et al., 2007).
    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

[[Page 18174]]

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 USGS's EA 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 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, 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 kms, even 
though the airgun pulses remain well above ambient noise levels out to 
much longer distances. However, as reviewed in Appendix B (5) of USGS's 
EA, baleen whales exposed to strong noise pulses from airguns often 
react by deviating from their normal migration route and/or 
interrupting their feeding and moving away. In the cases of migrating 
gray and bowhead whales, the observed changes in behavior appeared to 
be of little or no biological consequence to the animals (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 (rms) 
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 USGS's EA have shown that some species of baleen whales, notably 
bowhead and humpback whales, at times, show strong avoidance at 
received levels lower than 160 to 170 dB re 1 [mu]Pa (rms).
    McCauley et al. (1998, 2000a) 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 [micro]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 (rms).
    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 USGS's EA). However, more recent 
research on bowhead whales (Miller et al., 2005; Harris et al., 2007) 
corroborates earlier evidence that, during the summer feeding season, 
bowheads are not as

[[Page 18175]]

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 [micro]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 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; Allen and Angliss, 2010).
    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 USGS's EA 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 show stronger avoidance of seismic 
operations than do Dall's porpoises (Stone, 2003; MacLean and Koski, 
2005; Bain and Williams, 2006; Stone and Tasker, 2006). Dall's 
porpoises seem relatively tolerant of airgun operations (MacLean and 
Koski, 2005; Bain and Williams, 2006), although they too have been 
observed to avoid large arrays of operating airguns (Calambokidis and 
Osmek, 1998; Bain and Williams, 2006). This apparent difference in 
responsiveness of these two porpoise species is consistent with their 
relative responsiveness to boat traffic and some other acoustic sources 
(Richardson et al., 1995; Southall et al., 2007).
    Most studies of sperm whales exposed to airgun sounds indicate that 
the sperm whale shows considerable tolerance of airgun pulses (e.g., 
Stone, 2003; Moulton et al., 2005, 2006a; Stone and Tasker, 2006; Weir, 
2008). In most cases

[[Page 18176]]

the whales do not show strong avoidance, and they continue to call (see 
Appendix B of USGS's EA for review). However, controlled exposure 
experiments in the Gulf of Mexico indicate that foraging behavior was 
altered upon exposure to airgun sound (Jochens et al., 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 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 USGS's EA).
    Pinnipeds--Pinnipeds are not likely to show a strong avoidance 
reaction to the airgun array. Visual monitoring from seismic vessels 
has shown only slight (if any) avoidance of airguns by pinnipeds, and 
only slight (if any) changes in behavior, see Appendix B of USGS's EA. 
In the Beaufort Sea, some ringed seals avoided an area of 100 m to (at 
most) a few hundred meters around seismic vessels, but many seals 
remained within 100 to 200 m (328 to 656 ft) of the trackline as the 
operating airgun array passed by (e.g., Harris et al., 2001; Moulton 
and Lawson, 2002; Miller et al., 2005). Ringed seal sightings averaged 
somewhat farther away from the seismic vessel when the airguns were 
operating than when they were not, but the difference was small 
(Moulton and Lawson, 2002). Similarly, in Puget Sound, sighting 
distances for harbor seals and California sea lions tended to be larger 
when airguns were operating (Calambokidis and Osmek, 1998). Previous 
telemetry work suggests that avoidance and other behavioral reactions 
may be stronger than evident to date from visual studies (Thompson et 
al., 1998).

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 (above) 
presents the distances from the Langseth's airguns at which the 
received energy level (per pulse, flat-weighted) would be expected to 
be greater than or equal to 180 dB re 1 [micro]Pa (rms).
    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 (rms). 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 (rms). 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

[[Page 18177]]

TTS onset may also be higher in baleen whales (Southall et al., 2007). 
For this proposed study, USGS 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.
    In pinnipeds, TTS thresholds associated with exposure to brief 
pulses (single or multiple) of underwater sound have not been measured. 
Initial evidence from more prolonged (non-pulse) exposures suggested 
that some pinnipeds (harbor seals in particular) incur TTS at somewhat 
lower received levels than do small odontocetes exposed for similar 
durations (Kastak et al., 1999, 2005; Ketten et al., 2001). The TTS 
threshold for pulsed sounds has been indirectly estimated as being an 
SEL of approximately 171 dB re 1 [mu]Pa\2\[middot]s (Southall et al., 
2007) which would be equivalent to a single pulse with received level 
approximately 181 to 186 dB re 1 [mu]Pa (rms), or a series of pulses 
for which the highest rms values are a few dB lower. Corresponding 
values for California sea lions and northern elephant seals are likely 
to be higher (Kastak et al., 2005).
    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 dBs above that inducing mild TTS if the animal were 
exposed to strong sound pulses with rapid rise time--see Appendix B(6) 
of USGS's EA. Based on data from terrestrial mammals, a precautionary 
assumption is that the PTS threshold for impulse sounds (such as airgun 
pulses as received close to the source) is at least 6 dB higher than 
the TTS threshold on a peak-pressure basis, and probably greater than 
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, 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 USGS's EA provides 
additional details.
    Specific sound-related processes that lead to strandings and 
mortality are not well documented, but may include:
    (1) Swimming in avoidance of a sound into shallow water;
    (2) A change in behavior (such as a change in diving behavior) that 
might contribute to tissue damage, gas bubble formation, hypoxia, 
cardiac arrhythmia, hypertensive hemorrhage or other forms of trauma;
    (3) A physiological change such as a vestibular response leading to 
a behavioral change or stress-induced hemorrhagic diathesis, leading in 
turn to tissue damage; and
    (4) Tissue damage directly from sound exposure, such as through 
acoustically-mediated bubble formation and growth or acoustic resonance 
of tissues. Some of these mechanisms are unlikely to apply in the case 
of impulse sounds. However, there are 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\) array in the 
general area. The link between the stranding and the seismic surveys 
was inconclusive and not based on any physical evidence (Hogarth, 2002; 
Yoder, 2002). Nonetheless, the Gulf of California incident plus the 
beaked whale strandings near naval exercises involving use of mid-
frequency sonar suggests a need for caution in conducting seismic 
surveys in areas

[[Page 18178]]

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, and
    (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
    USGS 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 (rms). 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 (in water 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 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 USGS'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 [micro]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 USGS, and to shorter 
broadband pulsed signals. Behavioral changes typically involved what 
appeared to be deliberate attempts to avoid the sound exposure 
(Schlundt et al., 2000; Finneran et al., 2002; Finneran and Schlundt, 
2004). The relevance of those data to free-ranging odontocetes is 
uncertain, and in any case, the test sounds were quite different in 
duration as compared with those from an MBES.
    Very few data are available on the reactions of pinnipeds to 
echosounder sounds at frequencies similar to those used during seismic 
operations. Hastie and Janik (2007) conducted a series of behavioral 
response tests on two captive gray seals to determine their reactions 
to underwater operation of a 375 kHz multibeam imaging echosounder that 
included significant signal components down to 6 kHz. Results indicated 
that the two seals reacted to the signal by significantly increasing 
their dive durations. Because of the likely brevity of exposure to the 
MBES sounds, pinniped reactions are expected to be limited to startle 
or otherwise brief responses of no lasting consequences to the animals.
    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 USGS is quite different than sonar used for Navy 
operations. Pulse duration of the MBES is very short relative to the 
naval sonar.

[[Page 18179]]

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
    USGS will also operate an 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 SBP on the Langseth has a maximum source level of 204 dB 
re 1 [micro]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 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.

Acoustic Release Signals

    The acoustic release transponder used to communicate with the OBSs 
uses frequencies 9 to 13 kHz. These signals will be used very 
intermittently. It is unlikely that the acoustic release signals would 
have a significant effect on marine mammals through masking, 
disturbance, or hearing impairment. Any effects likely would be 
negligible given the brief exposure at presumably low levels.
    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 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 USGS's EA). There are three 
types of potential effects of exposure to seismic surveys: (1) 
Pathological, (2) physiological, and (3) behavioral. Pathological 
effects involve lethal and temporary or permanent sub-lethal injury. 
Physiological effects involve temporary and permanent primary and 
secondary stress responses, such as changes in levels of enzymes and 
proteins. Behavioral effects refer to temporary and (if they occur) 
permanent changes in exhibited behavior (e.g., startle and avoidance 
behavior). The three categories are interrelated in complex ways. For 
example, it is possible that certain physiological and behavioral 
changes 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 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 USGS's EA). 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,

[[Page 18180]]

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 USGS and NMFS 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) 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 nine 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., 2000 a,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 USGS's EA).
    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; 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 USGS's EA).
    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.

[[Page 18181]]

    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 USGS's EA.
    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., 2000 a,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., 2000 a,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 
grounds, and areas of similar significance, and the availability of 
such species or stock for taking for certain subsistence uses.
    USGS has based the mitigation measures described herein, to be 
implemented for the proposed seismic survey, on the following:
    (1) Protocols used during previous USGS and 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, USGS and/or its designees has proposed 
to implement the following mitigation measures for marine mammals:
    (1) Proposed exclusion zones;
    (2) Power-down procedures;
    (3) Shut-down procedures;
    (4) Ramp-up procedures; and
    (5) Special procedures for situations and species of concern.
    Planning Phase--In designing the proposed seismic survey, USGS has 
considered potential environmental impacts including seasonal, 
biological, and weather factors; ship schedules; and equipment 
availability. Part of the considerations was whether the research 
objectives could be met with a smaller source; tests will be conducted 
to determine whether the two-string sub-array (3,300 in\3\) will be 
satisfactory to accomplish the geophysical objectives. If so, the 
smaller array will be used to minimize environmental impact. Also, the 
array will be powered-down to a single airgun during turns, and the 
array will be shut-down during OBS deployment and retrieval.
    Proposed Exclusion Zones--Received sound levels have been 
determined by empirical corrected measurements for the 36 airgun array, 
and an L-DEO model was used to predict the EZs for the single 1,900LL 
40 in\3\ airgun, which will be used during power-downs. Results were 
recently reported for propagation measurements of pulses from the 36 
airgun array in two water depths (approximately 1,600 m and 50 m [5,249 
to 164 ft]) in the Gulf of Mexico in 2007 to 2008 (Tolstoy et al., 
2009). It would be prudent to use the empirical values that resulted to 
determine EZs for the airgun array. Results of the propagation 
measurements (Tolstoy et al., 2009) showed that radii around the 
airguns for various received levels varied with water depth. During the 
proposed study, all survey effort will take place in deep (greater than 
1,000 m) water, so propagation in shallow water is not relevant here. 
The depth of the array was different in the Gulf of Mexico calibration 
study (6 m [19.7 ft]) than in the proposed survey (9 m); thus, 
correction factors have been applied to the distances reported by 
Tolstoy et al.

[[Page 18182]]

(2009). The correction factors used were the ratios of the 160, 180, 
and 190 dB distances from the modeled results for the 6,600 in\3\ 
airgun array towed at 6 m versus 9 m. Based on the propagation 
measurements and modeling, the distances from the source where sound 
levels are predicted to be 190, 180, and 160 dB re 1 [micro]Pa (rms) 
were determined (see Table 1 above). The 180 and 190 dB radii are to 
940 m and 400 m, respectively, as specified by NMFS (2000); these 
levels were used to establish the EZs. If the PSVO detects marine 
mammal(s) within or about to enter the appropriate EZ, the airguns will 
be powered-down (or shut-down, if necessary) immediately.
    Power-Down Procedures--A power-down involves decreasing the number 
of airguns in use such that the radius of the 180 dB (or 190 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 array can also occur 
when the vessel is moving from one seismic line to another. During a 
power-down for mitigation, USGS 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, USGS will power-down the airguns before the 
animal is within the EZ. Likewise, if a mammal is already within the 
EZ, when first detected USGS will power-down the airguns immediately. 
During a power-down of the airgun array, USGS 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), USGS will shut-down the airgun 
(see next section).
    Following a power-down, USGS will not resume airgun activity until 
the marine mammal has cleared the EZ. 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 species with shorter dive durations (i.e., small odontocetes or 
pinnipeds), or 30 min for species with longer dive durations (i.e., 
mysticetes and large odontocetes, including sperm, pygmy sperm, dwarf 
sperm, killer, and beaked whales).
    During airgun operations following a power-down (or shut-down) 
whose duration has exceeded the time limits specified previously, USGS 
will ramp-up the airgun array gradually (see Shut-down and Ramp-up 
Procedures).
    Shut-down Procedures--USGS will shut down the operating airgun(s) 
if a marine mammal is seen within or approaching the EZ for the single 
airgun. USGS will implement a shut-down:
    (1) If an animal enters the EZ of the single airgun after USGS 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.
    USGS 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--USGS will follow a ramp-up procedure when the 
airgun array begins operating after a specified period without airgun 
operations or when a power-down has exceeded that period. USGS proposes 
that, for the present cruise, this period would be approximately eight 
min. This period is based on the 180 dB radius (940 m) for the 36 
airgun array towed at a depth of 9 m in relation to the minimum planned 
speed of the Langseth while shooting (7.4 km/hr). USGS and L-DEO have 
used similar periods (approximately 8 to 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 min 
period over a total duration of approximately 35 min. During ramp-up, 
the PSOs will monitor the EZ, and if marine mammals are sighted, USGS 
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, USGS 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. USGS 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.
    Special Procedures for Situations and Species of Concern--USGS will 
implement special mitigation procedures as follows:
     The airguns will be shut-down immediately if ESA-listed 
species for which no takes are being requested (i.e., North Pacific 
right, sei, blue, and beluga whales) are sighted at any distance from 
the vessel. Ramp-up will only begin if the whale has not been seen for 
30 min.
     Concentrations of humpback, fin, and/or killer whales will 
be avoided if possible, and the array will be powered-down if 
necessary. For purposes of this proposed survey, a concentration or 
group of whales will consist of three or more individuals visually 
sighted and do not appear to be traveling (e.g., feeding, socializing, 
etc.).
    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. NMFS's 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 NMFS's 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 mammal species or stocks and their habitat, paying particular 
attention to rookeries, mating grounds, and areas of similar 
significance.

Proposed Monitoring and Reporting

    In order to issue an ITA for an activity, section 101(a)(5)(D) of 
the MMPA states that NMFS must set forth ``requirements pertaining to 
the monitoring and reporting of such taking.'' The MMPA implementing 
regulations at 50 CFR 216.104 (a)(13) indicate that requests for IHAs 
must

[[Page 18183]]

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

    USGS proposes to sponsor marine mammal monitoring during the 
proposed project, in order to implement the proposed mitigation 
measures that require real-time monitoring, and to satisfy the 
anticipated monitoring requirements of the IHA. USGS's proposed 
Monitoring Plan is described below this section. USGS 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. USGS 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 ramp-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 in the central GOA, at least four PSOs 
will be based aboard the Langseth. USGS will appoint the PSOs with 
NMFS' concurrence. Observations will take place during ongoing daytime 
operations and nighttime ramp-ups of the airguns. During the majority 
of seismic operations, two PSVOs will be on duty from the observation 
tower to monitor marine mammals near the seismic vessel. Use of two 
simultaneous PSVOs will increase the effectiveness of detecting animals 
near the source vessel. However, during meal times and bathroom breaks, 
it is sometimes difficult to have two PSVOs on effort, but at least one 
PSVO will be on duty. PSVO(s) will be on duty in shifts of duration no 
longer than 4 hr.
    Two PSVOs will also be on visual watch during all nighttime ramp-
ups of the seismic airguns. A third PSO 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 PSO on PAM. 
Other crew will also be instructed to assist in detecting marine 
mammals and implementing mitigation requirements (if practical). Before 
the start of the seismic survey, the crew will be given additional 
instruction on how to do so.
    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 PSVO 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.
    When marine mammals are detected within or about to enter the 
designated EZ, the airguns will immediately be powered-down or shut-
down if necessary. The PSO(s) will continue to maintain watch to 
determine when the animal(s) are outside the EZ by visual confirmation. 
Airgun operations will not resume until the animal is confirmed to have 
left the EZ, or if not observed after 15 min for species with shorter 
dive durations (small odontocetes and pinnipeds) or 30 min for species 
with longer dive durations (mysticetes and large odontocetes, including 
sperm, killer, and beaked whales).

Passive Acoustic Monitoring (PAM)

    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 Protected Species Acoustic 
Observer (PSAO) with primary responsibility for PAM will also be aboard 
the vessel. USGS can use acoustic 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 PSVOs 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 array will be 
deployed from a winch located on the back deck. A deck cable will 
connect from the winch to the main computer laboratory where the 
acoustic station and signal conditioning and processing system will be 
located. The digitized signal and PAM system is monitored by PSOs at a 
station in the main laboratory. 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).
    Ideally, the PSAO will monitor the towed hydrophones 24 hr per day 
at the seismic survey area 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 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, USGS would continue 
science acquisition with the visual-based observer program. The PAM

[[Page 18184]]

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 PSAO will monitor the acoustic detection system at any one 
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. PSAOs monitoring the acoustical 
data will be on shift for one to six hours at a time. Besides the PSVO, 
an additional PSAO 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 PSAO will contact the 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. Observations will also be made during daytime periods when the 
Langseth is underway without seismic operations. In addition to 
transits to, from, and through the study area, there will also be 
opportunities to collect baseline biological data during the deployment 
and recovery of OBSs.
    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 in the area where the seismic study is conducted.
    4. Information to compare the distance and distribution of marine 
mammals 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.
    USGS 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 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.
    USGS 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. In the unanticipated event that any taking of a 
marine mammal in a manner prohibited by the proposed IHA occurs, such 
as an injury, serious injury, or mortality, and are judged to result 
from the proposed activities, the operator will immediately report the 
incident to the Chief of the Permits, Conservation, and Education 
Division, Office of Protected Resources, NMFS. The operator will 
postpone the proposed activities until NMFS is able to review the 
circumstances of the take. NMFS will work with the operator to 
determine whether modifications in the activities are appropriate and 
necessary, and notify the operator that they may resume sound source 
operations.

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 in the central GOA. 
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 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 USGS seeks the IHA. The required mitigation and 
monitoring measures will minimize any potential risk for injury, 
serious injury, or mortality.
    The following sections describe USGS's methods to estimate take by 
incidental harassment and present the applicant's estimates of the 
numbers of marine mammals that could be affected

[[Page 18185]]

during the proposed seismic program. The estimates are based on a 
consideration of the number of marine mammals that could be disturbed 
appreciably by operations with the 36 airgun array to be used during 
approximately 3,300 km (1,782 nmi) of survey lines in the central GOA.
    USGS 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, USGS provides no 
additional allowance for animals that could be affected by sound 
sources other than airguns.
    There are several sources of systematic data on the numbers and 
distributions of marine mammals in the coastal and nearshore areas of 
the GOA, but there are fewer data for offshore areas. Vessel-based 
surveys in the northern and western GOA from the Kenai Peninsula to the 
central Aleutian Islands during July to August, 2001 to 2001 (Zerbini 
et al., 2003, 2006, 2007) and in the northern and western GOA from 
Prince William Sound to approximately 160[deg] West off the Alaska 
Peninsula during June 26 to July 15, 2003 (Waite, 2003) were confined 
to waters less than 1,000 m deep, and most effort was in depths less 
than 100 m. Similarly, Dahlheim et al. (2000) conducted aerial surveys 
of the nearshore waters from Bristol Bay to Dixon Entrance for harbor 
porpoises during 1993, and Dahlheim and Towell (1994) conducted vessel-
based surveys of Pacific white-sided dolphins in the inland waterways 
of southeast Alaska during April to May, June or July, and September to 
early October of 1991 to 1993.
    Deeper water was included in several surveys. In a report on a 
seismic cruise in southeast Alaska from Dixon Entrance to Kodiak Island 
during August to September, 2004, MacLean and Koski (2005) included 
density estimates of cetaceans and pinnipeds for each of three depth 
ranges (less than 100 m, 100 to 1,000 m, and greater than 1,000 m) 
during non-seismic periods. Hauser and Holst (2009) reported density 
estimates during non-seismic periods for all marine mammals sighted 
during a September to early October seismic cruise in southeast Alaska 
for each of the same three depth ranges as MacLean and Koski (2005). 
Rone et al. (2010) conducted surveys of nearshore and offshore strata 
in the GOA during April, 2009, with much of their survey effort in 
water depths greater than 1,000 m. The Department of the Navy (DON) 
(2009) estimated densities of several species of marine mammals in the 
offshore GOA based on surveys by other researchers.
    Table 2 (Table 3 of the IHA application) gives the estimated 
average (best) and maximum densities of marine mammals expected to 
occur in the deep, offshore waters of the proposed survey area. USGS 
used the densities reported by MacLean and Koski (2005) and Hauser and 
Holst (2009) for greater than 1,000 m, which were corrected for both 
detectability and availability biases. USGS calculated density 
estimates from effort and sightings in water depths greater than 1,000 
m in Rone et al. (2010) for humpback, fin, and killer whales and Dall's 
porpoise, and in 500 to 1,000 m depths of Waite (2003) for Cuvier's and 
Baird's beaked whales, using values for [fnof](0) and g(0) from Barlow 
and Forney (2007). Finally, USGS used seasonal densities for pinnipeds 
from DON (2009), which were based on counts at haul-out sites and 
biological (mostly breeding) information to estimate in-water 
densities.
    There is some uncertainty about the representativeness of the data 
and the assumptions used in the calculations below for two main 
reasons: (1) The surveys from which densities were derived were at 
different times of year: April (Rone et al., 2010), June to July 
(Waite, 2003), August to September (MacLean and Koski, 2005), and 
September to October (Hauser and Holst, 2009); and (2) the MacLean and 
Koski (2005) and Hauser and Holst (2009) surveys were conducted 
primarily in southeast Alaska (east of the proposed study area). 
However, the approach used here is believed to be the best available 
approach.
    Also, to provide some allowance for these uncertainties, ``maximum 
estimates'' as well as ``best estimates'' of the densities present and 
numbers potentially affected have been derived. Best estimates of 
cetacean density are effort-weighted mean densities from the various 
surveys, whereas maximum estimates of density come from the individual 
survey that provided the highest density. For marine mammals where only 
one density estimate was available, the maximum is 1.5x the best 
estimate.
    For one species, the Dall's porpoise, density estimates in the 
original reports are much higher than densities expected during the 
proposed survey, because this porpoise is attracted to vessels. USGS 
estimates for Dall's porpoises are from vessel-based surveys without 
seismic activity; they are overestimates possibly by a factor of 5x, 
given the tendency of this species to approach vessels (Turnock and 
Quinn, 1991). Noise from the airgun array during the proposed survey is 
expected to at least reduce and possibly eliminate the tendency of this 
porpoise to approach the vessel. Dall's porpoises are tolerant of small 
airgun sources (MacLean and Koski, 2005) and tolerated higher sound 
levels than other species during a large-array survey (Bain and 
Williams, 2006); however, they did respond to that and another large 
airgun array by moving away (Calambokidis and Osmek, 1998; Bain and 
Williams, 2006). Because of the probable overestimates, the best and 
maximum estimates for Dall's porpoises shown in Table 2 (Table 3 of the 
IHA application) are one-quarter of the reported densities. In fact, 
actual densities are probably slightly lower than that.
    USGS's estimates of exposures to various sound levels assume that 
the proposed surveys will be fully completed including the contingency 
line; in fact, the ensonified areas calculated using the planned number 
of line-km have been increased by 25% to accommodate lines that may 
need to be repeated, equipment testing, etc. 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. Furthermore, 
any marine mammal sightings within or near the designated EZs 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 
[mu]Pa (rms) 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.
    USGS 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 [mu]Pa (rms) 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

[[Page 18186]]

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 widely spaced in the survey 
area, so few individual marine mammals would be exposed more than once 
during the survey. The area including overlap is only 1.13 times the 
area excluding overlap. 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 [mu]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.
    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 
of the IHA application) around each seismic line, and then calculating 
the total area within the buffers. Areas of overlap (because of lines 
being closer together than the 160 dB radius) were limited and included 
only once when estimating the number of individuals exposed. Before 
calculating numbers of individuals exposed, the areas were increased by 
25% as a precautionary measure.
    Table 2 (Table 4 of the IHA application) shows the best and maximum 
estimates of the number of different individual marine mammals that 
potentially could be exposed to greater than or equal to 160 dB re 1 
[mu]Pa (rms) during the seismic survey if no animals moved away from 
the survey vessel. The requested take authorization, given in Table 3 
(the far right column of Table 4 of the IHA application), is based on 
the maximum estimates rather than the best estimates of the numbers of 
individuals exposed, because of uncertainties about the 
representativeness of the density data discussed previously.
    Applying the approach described above, approximately 20,933 km\2\ 
(6,103.1 nmi\2\) (approximately 26,166 km\2\ [7,628.8 nmi\2\] including 
the 25% contingency) would be within the 160 dB isopleths on one or 
more occasions during the survey, assuming that the contingency line is 
completed. Because this approach does not allow for turnover in the 
marine 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.
    The ``best estimate'' of the number of individual cetaceans that 
could be exposed to seismic sounds with greater than or equal to 160 dB 
re 1 [mu]Pa (rms) during the proposed survey is 776 (see Table 4 of the 
IHA application). That total includes 56 humpback, 63 fin, 8 sperm, 34 
Cuvier's beaked, 11 Baird's beaked, and 82 killer whales, which would 
represent 0.3%, 0.4%, less than 0.1%, 0.2%, 0.2%, and 1% of the 
regional populations, respectively. Dall's porpoises are expected to be 
the most common species in the study area; the best estimate of the 
number of Dall's porpoises that could be exposed is 522 or less than 
0.1% of the regional population. This may be a slight overestimate 
because the estimated densities are slight overestimates. Estimates for 
other species are lower. The ``maximum estimates'' total 1,882 
cetaceans. ``Best estimates'' of 256 Steller sea lions and 2,771 
northern fur seals could be exposed to airgun sounds with received 
levels greater than or equal to 160 dB re 1 [mu]Pa (rms). These 
estimates represent 0.6% of the Steller sea lion regional population 
and less than 0.1% of the northern fur seal regional population. The 
estimated numbers of pinnipeds that could be exposed to received levels 
greater than or equal to 160 dB re 1 [mu]Pa (rms) are probably 
overestimates of the actual numbers that will be affected. During the 
June survey period, the Steller sea lion is in its breeding season, 
with males staying on land and females with pups generally staying 
close to the rookeries in shallow water. Male northern fur seals are at 
their rookeries in June, and adult females are either there or 
migrating there, possibly through the survey area. No take has been 
requested for North Pacific right, minke, sei, and blue whales, 
Stejneger's beaked whales, beluga whales, Pacific white-sided and 
Risso's dolphins, short-finned pilot whales, harbor porpoises, Northern 
elephant and harbor seals, and California sea lions.

 Table 3--Estimates of the Possible Numbers of Marine Mammals Exposed to Different Sound Levels >=160 dB During
                       USGS's Proposed Seismic Survey in the Central GOA During June 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 (Best     re 1 [mu]Pa                          population \2\
                                             \1\)          (Maximum \1\)                             (Best)
----------------------------------------------------------------------------------------------------------------
Balaenopteridae:
    North Pacific right whale.......                  0                  0                  0                  0
    Gray whale......................                 NA                 NA                 NA                 NA
    Humpback whale..................                 56                171                171                0.3
    Minke whale.....................                  0                  0                  0                  0
    Sei whale.......................                  0                  0                  0                  0
    Fin whale.......................                 63                155                155                0.4
    Blue whale......................                  0                  0                  0                  0
Physeteridae:
    Sperm whale.....................                  8                 35                 35               <0.1
Ziphidae:
    Cuvier's beaked whale...........                 34                 38                 38                0.2
    Baird's beaked whale............                 11                 13                 13                0.2
    Stejneger's beaked whale........                  0                  0                  0                  0
Delphinidae:
    Beluga whale....................                 NA                 NA                 NA                 NA

[[Page 18187]]

 
    Pacific white-sided dolphin.....                 NA                 NA                 NA                 NA
    Risso's dolphin.................                 NA                 NA                 NA                 NA
    Killer whale....................                 82                162                162                1.0
    Short-finned pilot whale........                 NA                 NA                 NA                 NA
Phocoenidae:
    Harbor porpoise.................                 NA                 NA                 NA                 NA
    Dall's porpoise.................                522              1,308              1,308               <0.1
Pinnipeds:
    Northern fur seal...............              2,771              3,325              3,325               <0.1
    Steller sea lion................                256                308                308                0.6
    California sea lion.............                 NA                 NA                 NA                 NA
    Harbor seal.....................                 NA                 NA                 NA                 NA
    Northern elephant seal..........                  0                  0                  0                  0
----------------------------------------------------------------------------------------------------------------
\1\ Best and maximum estimates are based on densities from Table 3 and ensonified areas (including 25%
  contingency) of 26,166.25 km\2\ for 160 dB.
\2\ Regional population size estimates are from Table 2 (see Table 2 of the IHA application); NA means not
  available.

Encouraging and Coordinating Research

    USGS will coordinate the planned marine mammal monitoring program 
associated with the seismic survey in the central GOA with other 
parties that may have interest in the area and/or be conducting marine 
mammal studies in the same region during the proposed seismic survey. 
USGS will coordinate with applicable U.S. agencies (e.g., NMFS), and 
will comply with their requirements.

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.''
    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, on behalf of the Secretary, preliminarily finds that 
USGS's activities would result in the incidental take of marine 
mammals, by Level B harassment only, and that the total taking from the 
marine seismic survey in the central GOA would have a negligible impact 
on the affected species or stocks of marine mammals.
    For reasons stated previously in this document, the specified 
activities associated with the marine seismic survey are not likely to 
cause TTS, PTS, or other non-auditory injury, serious injury, or death 
is anticipated or authorized, and the potential for temporary or 
permanent hearing impairment is very low and will be minimized through 
the incorporation of the monitoring and mitigation measures.
    In making a negligible impact determination, NMFS evaluated factors 
such as:
    (1) The number of anticipated injuries, serious injuries, or 
mortalities;
    (2) the number, nature, and intensity, and duration of Level B 
harassment (all relatively limited); and
    (3) the context in which the takes occur (i.e., impacts to areas of 
significance, impacts to local populations, and cumulative impacts when 
taking into account successive/contemporaneous actions when added to 
baseline data);
    (4) the status of stock or species of marine mammals (i.e., 
depleted, not depleted, decreasing, increasing, stable, impact relative 
to the size of the population);
    (5) impacts on habitat affecting rates of recruitment/survival; and
    (6) the effectiveness of monitoring and mitigation measures.
    As mentioned previously, NMFS estimates that nine 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, one 
percent or less) relative to the population size.
    No injuries, serious injuries, or mortalities are anticipated to 
occur as a result of the USGS's planned marine seismic 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 central GOA, June, 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 USGS'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 seismic survey

[[Page 18188]]

will have a negligible impact on the affected species or stocks.

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

    Section 101(a)(5)(D) also requires NMFS to determine that the 
authorization will not have an unmitigable adverse effect on the 
availability of marine mammal species or stocks for subsistence use. 
There are no relevant subsistence uses of marine mammals in the study 
area (deep, offshore waters of the central GOA) that implicate MMPA 
Section 101(a)(5)(D).

Endangered Species Act

    Of the species of marine mammals that may occur in the proposed 
survey area, several are listed as endangered under the ESA, including 
the North Pacific right, humpback, sei, fin, blue, and sperm whales, as 
well as the Cook Inlet DPS of beluga whales and the western stock of 
Steller sea lions. The eastern stock of Steller sea lions is listed as 
threatened, as is the southwest Alaska DPS of the sea otter. Under 
Section 7 of the ESA, USGS has initiated formal consultation with the 
NMFS, Office of Protected Resources, Endangered Species Division, on 
this proposed seismic survey. NMFS's 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, 
USGS, 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's 
Biological Opinion issued to both USGS and NMFS's Office of Protected 
Resources.

National Environmental Policy Act (NEPA)

    With its complete application, USGS provided NMFS an EA analyzing 
the direct, indirect, and cumulative environmental impacts of the 
proposed specified activities on marine mammals including those listed 
as threatened or endangered under the ESA. The EA, prepared by LGL on 
behalf of USGS is entitled ``Environmental Assessment of a Marine 
Geophysical Survey by the R/V Marcus G. Langseth in the central Gulf of 
Alaska, June 2011.'' Prior to making a final decision on the IHA 
application, NMFS will either prepare an independent EA, or, after 
review and evaluation of the USGS EA for consistency with the 
regulations published by the Council of Environmental Quality (CEQ) and 
NOAA Administrative Order 216-6, Environmental Review Procedures for 
Implementing the National Environmental Policy Act, adopt the USGS EA 
and make a decision of whether or not to issue a Finding of No 
Significant Impact (FONSI).

Proposed Authorization

    NMFS proposes to issue an IHA to USGS for conducting a marine 
geophysical survey in the central GOA, 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: March 25, 2011.
James H. Lecky,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. 2011-7487 Filed 3-31-11; 8:45 am]
BILLING CODE 3510-22-P