[Federal Register Volume 76, Number 224 (Monday, November 21, 2011)]
[Notices]
[Pages 71940-71958]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-30010]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XA792


Takes of Marine Mammals Incidental to Specified Activities; 
Physical Oceanographic Studies in the Southwest Indian Ocean, January 
Through February, 2012

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 United States Navy 
(Navy) for an Incidental Harassment Authorization (IHA) to take marine 
mammals, by harassment, incidental to conducting physical oceanographic 
studies in the southwest Indian Ocean, January through February, 2012. 
Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting 
comments on its proposal to issue an IHA to the Navy to incidentally 
harass, by Level B harassment only, 29 species of marine mammals during 
the specified activity.

DATES: Comments and information must be received no later than December 
21, 2011.

ADDRESSES: Comments on the application should be addressed to P. 
Michael Payne, Chief, Permits and Conservation 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 
email 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.
    An electronic 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.
    In accordance with Executive Order 12114, the Navy has prepared a 
draft Overseas Environmental Assessment (OEA), which is also available 
on the Internet. Documents cited in this notice may be viewed, by 
appointment, during regular business hours, at the aforementioned 
address.

FOR FURTHER INFORMATION CONTACT: Michelle Magliocca, Office of 
Protected Resources, NMFS, (301) 427-8401.

SUPPLEMENTARY INFORMATION:

Background

    Section 101(a)(5)(D) of the Marine Mammal Protect Act of 1972, as 
amended (MMPA; 16 U.S.C. 1361 et seq.) directs the Secretary of 
Commerce to authorize, upon request, the incidental, but not 
intentional, taking of small numbers of marine mammals of a species or 
population stock, by United States citizens who engage in a specified 
activity (other than commercial fishing) within a specified 
geographical region if certain findings are made and, if the taking is 
limited to harassment, a notice of a proposed authorization is provided 
to the public for review.
    Authorization for the incidental taking of small numbers of marine 
mammals shall be granted if NMFS finds that the taking will have a 
negligible impact on the species or stock(s), and will not have an 
unmitigable adverse impact on the availability of the species or 
stock(s) for subsistence uses (where relevant). The authorization must 
set forth the permissible methods of taking, other means of effecting 
the least practicable adverse impact on the species or stock and its 
habitat, and requirements pertaining to the mitigation, monitoring

[[Page 71941]]

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. NMFS must publish a notice in the Federal Register 
within 30 days of its determination to issue or deny the authorization.
    Except with respect to certain activities not pertinent here, the 
MMPA defines ``harassment'' as:

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

Summary of Request

    NMFS received an application on August 15, 2011, from the Navy for 
the taking of marine mammals, by Level B harassment, incidental to 
conducting physical oceanographic studies in the southwest Indian 
Ocean. The Navy plans to conduct a seismic oceanographic survey from 
January 23, 2012, through February 8, 2012. Upon receipt of additional 
information, NMFS determined the application complete and adequate on 
September 14, 2011.
    The Navy plans to use one source vessel, the R/V Melville 
(Melville), and a seismic airgun array to obtain high resolution 
imaging of ocean mixing dynamics at the Agulhas Return Current and 
Antarctic Circumpolar Currents (ARC/ACC). The Melville would spend 14 
days on seismic oceanography surveys and three days on acoustic Doppler 
current profiler (ADCP) mooring deployments and recoveries, other 
oceanographic sampling methods, and transit to and from the study site.
    Acoustic stimuli (i.e., increased underwater sound) generated 
during the operation of the 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 the Navy has requested an 
authorization to take 29 species of marine mammals by Level B 
harassment. Take is not expected to result from the use of the 
multibeam echosounder (MBES), subbottom profiler (SBP), or ADCPs, due 
to the narrow and directional acoustic beam field of the MBES, the 
attenuation rate of high-frequency sound in seawater, and the motility 
of free-ranging marine mammals. Take is also not expected to result 
from collision with the Melville because it is a single vessel moving 
at relatively slow speeds during seismic acquisition within the survey, 
for a relatively short period of time.

Description of the Specified Activity

    The Navy's proposed physical oceanographic studies are scheduled to 
commence on January 23, 2012, and continue for approximately 17 days 
ending on February 8, 2012. Some minor deviation from these dates is 
possible due to logistics and weather conditions; therefore, the 
authorization would be valid from January 23, 2012 through March 7, 
2012. Within this time period, the Navy would conduct seismic 
oceanography surveys using a towed array of two low-energy 105 in\3\ 
generator-injector (GI) airguns. The Melville would depart from Cape 
Town, South Africa, on January 23, 2012, and transit to the survey area 
near the Agulhas Plateau, off the southern tip of Africa. The exact 
location of the ARC/ACC front in January cannot be predetermined due to 
the natural meander of the currents, but studies would most likely take 
place within the boundaries of 36[deg]S to 43[deg]S and 19[deg]E to 
30[deg]E. The exact locations of the ARC/ACC frontal system would be 
determined on site using high-resolution conductivity-temperature-depth 
measurements. The total area of this region is about 207,500 nautical 
miles\2\ (Nm\2\) (713,000 kilometers\2\ [km\2\]). The proposed study 
would take place in water depths of approximately 1,000 to 5,200 meters 
(m). The survey would require approximately 17 days to complete 
approximately 2,489 km of transect lines, and be comprised of multiple 
transects across and along the ARC/ACC front.

Vessel Specifications

    The Melville, owned by the Navy, is a seismic research vessel with 
a propulsion system designed to be as quiet as possible to avoid 
interference with the seismic signals emanating from the airgun array. 
The vessel, which has a length of 97 m (318 feet [ft]); a beam of 14 m 
(46 ft); and a maximum draft of 5 m (16 ft); is powered by two 1,385 
horsepower (hp) Propulsion General Electric motors and a 900 hp 
retracting bow thruster. The Melville's operation speed during seismic 
acquisition would be approximately 7 to 11 km/hour (hr) (4 to 6 knots) 
and the cruising speed of the vessel outside of seismic operations 
would be about 20 km/hr (11 knots). The vessel also has a platform one 
deck below and forward of the bridge, which is positioned 12.5 m (41 
ft) above the waterline and provides a relatively unobstructed 180 
degree view forward. Aft views can be obtained along both the port and 
starboard decks.

Acoustic Source Specifications

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). RMS, 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.

Seismic Airguns

    The Melville would deploy two GI guns, which are stainless steel 
cylinders charged with high pressure air that, when instantaneously 
released into the water column, generate sound. The GI guns would 
operate in harmonic mode (105 in\3\ in each of the generator and 
injector chambers for a total discharge volume of 210 in\3\) with a 
1,200 m long hydrophone streamer. GI guns would be energized 
simultaneously at 2,000 psi every 17 seconds (s). The GI gun array

[[Page 71942]]

would emit sound at a frequency range of 10 to 188 Hertz (Hz) and reach 
a peak source level of 240 dB re 1 [micro]Pa. Seismic oceanography 
studies would be conducted 24 hours (hrs) per day for 14 days (336 hrs) 
and the GI guns would be towed at a depth of 3 to 9 m.

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 sound that travels horizontally toward non-
target areas. The nominal source levels of the airgun array that would 
be used by the Navy on the Melville are 234 dB re: 1 
[mu]Pa(0-p) to 240 dB re: 1 [mu]Pa(p-p).

Predicted Sound Levels for the Airguns

    Lamont-Doherty Earth Observatory (L-DEO) developed a verified model 
that predicts impulsive sound pressure field propagation and accurately 
describes acoustic propagation in marine waters of depths greater than 
1,000 m. These model-generated sound propagation radii are routinely 
used for determination of received sound levels generated by impulsive 
sound sources, and have been previously applied in calculating the 
total ensonified area for use of two low-energy 105 in\3\ GI-guns. 
Modeled sound propagation radii of GI-gun sources that are the same or 
similar to the GI-guns used in this study, in water depths > 1,000 m, 
are given in Table 1. These modeled acoustic propagation distances were 
applied in Environmental Assessments (EAs) and IHAs for seismic surveys 
conducted in the Eastern Tropical Pacific Ocean (ETP) off of Central 
America (NMFS, 2004), the Northern Gulf of Mexico (GOMEX) (L-DEO, 2003; 
NMFS, 2007), and the Arctic Ocean (NMFS, 2006).
    For the ETP, one and three 105 in\3\ GI-gun arrays were modeled, 
with a source output level of 241 dB re 1 [micro]Pa(0-p) and 
247 dB re 1 [micro]Pa(p-p). For the GOMEX survey, GI-gun 
source output levels were (a) 237 dB re 1 [micro]Pa(0-p) and 
243 dB re 1 [micro]Pa(p-p); and (b) 229 dB re 1 
[micro]Pa(0-p) and 236 dB re 1 [micro]Pa(p-p). L-
DEO modeling of a single G-gun has also been applied to a seismic 
survey in the Arctic Ocean. The source level for the 210 in\3\ G-gun 
was 246 dB re 1 [micro]Pa(0-p) and 253 dB re 1 
[micro]Pa(p-p). However, because the G-gun generates more 
energy than a GI-gun of the same size, the distances for received sound 
levels may be an overestimate for the lower energy dual 105 in\3\ GI-
gun source used in the ARC12 research project. The GI-gun is comprised 
of two, independently fired air chambers (the generator and the 
injector) to tune air bubble oscillation and minimize the amplitude of 
the acoustic pulse. In contrast, the G-gun is comprised of one chamber 
and generates a single, less refined injection of air into the water, 
which produces more acoustic energy than that of the GI-gun.

                               Table 1--Modeled Sound Propagation Radii for Low-Energy Air-Gun Arrays for Depths > 1,000 m
--------------------------------------------------------------------------------------------------------------------------------------------------------
 
--------------------------------------------------------------------------------------------------------------------------------------------------------
             Air-gun configuration               Water depth   Tow depth                   Received sound levels (dB re 1 [micro]Pa RMS)
                                                     (m)          (m)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                               190          180          160                     Location
                                                --------------------------------------------------------------------------------------------------------
                                                                      Distance
--------------------------------------------------------------------------------------------------------------------------------------------------------
1 GI-gun 105 in\3\.............................      > 1,000          2.5           10           27          275  ETP.
3 GI-guns 105 in\3\............................      > 1,000          2.5           26           82          823  ETP.
2 GI-guns 105 in\3\ (a)........................      > 1,000            3           20           69          670  GOMEX.
2 GI-guns 105 in\3\ (b)........................      > 1,000            6           15           50          520  GOMEX.
1 G-gun 210 in\3\..............................      > 1,000            9           20           78          698  Arctic.
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Based on extant modeling, the proposed sound propagation radii for 
the two 105 in\3\ GI-guns are 20 m, 70 m, and 670 m for the 190, 180, 
and 160 dB re 1 [micro]Pa RMS isopleths, respectively (Table 2). 
Empirical data indicate that for deep water (> 1,000 m), the L-DEO 
model tends to overestimate the received sound level at a given 
distance (Tolstoy et al., 2004). It follows that the proposed sound 
propagation radii are considered conservative, and the actual distance 
at which received sound levels are 160 dB re 1 uPa RMS or greater are 
expected to be less than that proposed. The proposed sound propagation 
radii are also consistent with recent modeling of sound propagation in 
the Southern Ocean (Breitzke and Bohlen, 2010).

    Table 2--Sound Propagation Radii for the Dual 105 in3 GI-Gun Array Proposed for Use in the ARC12 Research
                                                     Project
----------------------------------------------------------------------------------------------------------------
 
----------------------------------------------------------------------------------------------------------------
           Acoustic source             Frequency    Source level (dB re 1   Received levels (dB re 1 [micro]Pa)
                                          (Hz)            [micro]Pa)
----------------------------------------------------------------------------------------------------------------
                                                                               190          180          160
                                     ---------------------------------------------------------------------------
                                                        Distance (m)
----------------------------------------------------------------------------------------------------------------
2 GI-guns 105 in\3\.................       10-188  ~240(peak-to-peak)....           20           70          670
----------------------------------------------------------------------------------------------------------------

    Considering the circumference of the area ensonified to the 160 dB 
isopleth extends to 1,340 m (twice the 670 m radius); that the GI-gun 
array is towed approximately 2-9 m below the surface at a speed of 4 
knots (7.4 km/hr), and that the seismic oceanographic surveys would be 
conducted for 14 days for 24 hrs/day, the Navy estimates that the

[[Page 71943]]

seismic oceanographic survey distance would encompass 1,344 Nm (2,489 
km). Multiplying the total linear distance of the seismic oceanographic 
survey by the area ensonified to the 160 dB isopleth (1,340 m), yields 
a total ensonified area of approximately 3,335 km \2\.

Ocean Surveyor ADCP

    A hull-mounted Teledyne RD Instruments Ocean Surveyor ADCP (TRDI OS 
ADCP) would be operated at 38 kHz with acoustic output pressure of 224 
dB re 1 [micro]Pa. The beamwidth would be 30 degrees off nadir and the 
acoustic pressure along each beam is estimated at 180 dB re 1 [micro]Pa 
at 114 m. The TRDI OS ADCP would operate concurrently with the GI-gun 
array and intermittently to map the distribution of water currents and 
suspended materials in the water column.

Lowered ADCP (L-ADCP)

    A lowered Teledyne RD Instruments ADCP (L-ADCP) would be mounted on 
a rosette with a conductivity-temperature-depth gauge. The beamwidth 
would be 30 degrees off nadir and the output pressure would be 216 dB 
re 1 [micro]Pa at 300 kHz. The L-ADCP would be deployed intermittently 
to collect hydrographic data.

Moored ADCP

    Up to four long-range ADCPs (LR-ADCPs) would be anchored on the 
seafloor using 400 kilograms (kg) of scrap iron (assemblage of four 
scrap locomotive wheels). LR-ADCPs would be moored to the seafloor at 
an estimated 3,000 m, such that they float at a depth of 500 m below 
the sea surface. LR-ADCPs would be suspended from the iron anchorage 
assemblies by a single line comprised of \3/4\-inch (in) nylon line and 
\1/2\-in wire rope. The LR-ADCPs and suspension line would be recovered 
at the close of the study via an acoustic release and the iron 
anchorage assembly would remain on the sea floor. The acoustic source 
frequency would be 75 kHz with an output pressure level of 200 dB re 1 
[micro]Pa at a rate of once per second. The beamwidth would be four 
degrees and directed vertically upward at 20 degrees. LR-ADCPs would be 
moored several kilometers apart, in the area of the ARC/ACC frontal 
system, with exact mooring locations to be determined onsite due to the 
natural meander of the currents and front. LR-ADCPs would operate 
continuously for the estimated 14 days of research before being 
recovered.

Multibeam Echosounder

    The Melville would operate a hull-mounted Kongsberg EM 122 
multibeam echosounder (MBES) at 10.5 to 13 kilohertz (kHz). The MBES 
would generate acoustic pulses in a downward fan-shaped beam, one 
degree fore-aft and 150 degrees athwartship. For deep water operations, 
each ``ping'' is comprised of eight (> 1,000 m depth; 3,280 ft) or four 
(< 1,000 m depth; 3,280 ft) successive acoustic transmissions 2 to 100 
milliseconds (ms) in duration. The maximum sound pressure output level 
would be 242 dB re 1 [micro]Pa.

Sub-Bottom Profiler

    The Melville would also operate a Knudsen 320B/R sub-bottom 
profiler (SBP). The SBP is dual-frequency and operates at 3.5 and 12 
kHz with maximum power outputs of 10 kilowatts (kW) and 2 kW, 
respectively. The pulse length used during this study would be 0.8 to 
24 ms, relative to water depth and sediment characteristics. The pulse 
repetition rates would be between 0.5 and 2 seconds (s) in shallow 
water and up to 8 s in deep water. A common operational mode is 
broadcast of five pulses at 1-s intervals followed by a 5-s delay. 
Maximum acoustic output pressure would be 211 dB re 1 [micro]Pa at 3.5 
kHz; however, systems are typically used at 80 percent capacity. The 
SPB emits a downward conical beam with a width of about 30 degrees.

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

    Forty marine mammal species are known to inhabit waters between 
South Africa and Antarctica. Six of these species are listed as 
endangered under the U.S. Endangered Species Act of 1973 (ESA; 16 
U.S.C. 1531 et seq.) and depleted under the MMPA, including the 
southern right (Eubalaena australis), humpback (Megaptera 
novaeangliae), sei (Balaenoptera borealis), fin (Balaenoptera 
physalus), blue (Balaenoptera musculus), and sperm (Physeter 
macrocephalus) whales. Most of the species occurring in the area spend 
the austral summer in preferred Antarctic habitats, and the austral 
winter in areas northward around the east and west coasts of Africa, 
South America, Australia, and islands of the Indian Ocean. The cape fur 
seal is the only pinniped known to have breeding colonies along the 
southern coast of Africa. It is not listed as threatened or endangered 
under the ESA. Cape fur seals are endemic to South Africa, with 
colonies on islands and patches of mainland along the southern coast.
    Table 3 provides estimates of the average (best) and maximum marine 
mammal population densities in the area of the proposed study during 
the austral summer, anticipated occurrence of each species in the area 
of research during that time, primary habitat(s), and ESA listing 
status.

  Table 3--Habitat, Regional Abundance, and Conservation Status of Marine Mammals That May Occur in or Near the
                 Proposed Seismic Survey Areas Off Southern Africa in the Southwest Indian Ocean
     [See text and Tables 2.0-2.2 in the Navy's application and environmental analysis for further details.]
----------------------------------------------------------------------------------------------------------------
                                     Occurrence in                                                 Density
             Species               survey area during        Habitat            ESA\1\     ---------------------
                                  the Austral  summer                                          Best       Max
----------------------------------------------------------------------------------------------------------------
Mysticetes
    Antarctic minke whale.......  Rare...............  Pelagic and coastal  NL............     < 0.01       0.01
    Blue whale..................  Rare...............  Pelagic and coastal  E.............     < 0.01     < 0.01
    Bryde's whale...............  Common.............  Pelagic and coastal  NL............     < 0.01     < 0.01
    Common minke whale..........  Rare...............  Pelagic and coastal  NL............       0.03       0.05
    Fin whale...................  Rare...............  Continental shelf    E.............     < 0.01       0.01
                                                        and slope and
                                                        pelagic.
    Humpback whale..............  Rare...............  Mainly nearshore     E.............     < 0.01     < 0.01
                                                        waters and banks.
    Sei whale...................  Rare...............  Pelagic............  E.............     < 0.01     < 0.01
Odontocetes
    Arnoux's beaked whale.......  Rare...............  Deep water.........  NL............     < 0.01       0.01

[[Page 71944]]

 
    Cuvier's beaked whale.......  Common.............  Pelagic............  NL............     < 0.01     < 0.01
    Dwarf sperm whale...........  Indeterminate......  Continental shelf    NL............     < 0.01     < 0.01
                                                        an deep water.
    Gray's beaked whale.........  Rare...............  Deep water.........  NL............     < 0.01     < 0.01
    Hector's beaked whale.......  Rare...............  Deep water.........  NL............     < 0.01     < 0.01
    Pygmy right whale...........  Indeterminate......  Continental shelf..  NL............     < 0.01     < 0.01
    Pygmy sperm whale...........  Indeterminate......  Continental shelf    ..............     < 0.01     < 0.01
                                                        and deep water.
    Southern bottlenose whale...  Rare...............  Deep water.........  NL............       0.01       0.01
    Southern right whale........  Common.............  Coastal and pelagic  E.............     < 0.01     < 0.01
    Sperm whale.................  Common.............  Pelagic and deep     E.............       0.01       0.01
                                                        water.
    Strap-toothed whale.........  Common.............  Deep water.........  NL............     < 0.01     < 0.01
    True's beaked whale.........  Common.............  Deep water.........  NL............     < 0.01     < 0.01
    Common bottlenose dolphin...  Common.............  Coastal and pelagic  ..............       0.04       0.10
    Dusky dolphin...............  Rare...............  Coastal and pelagic  NL............     < 0.01     < 0.01
    False killer whale..........  Indeterminate......  Pelagic............  NL............     < 0.01     < 0.01
    Fraser's dolphin............  n/a................  Deep water.........  NL............        n/a        n/a
    Heaviside's dolphin.........  Rare...............  Coastal and deep     NL............     < 0.01       0.01
                                                        water.
    Hourglass dolphin...........  Rare...............  Coastal and pelagic  NL............     < 0.01     < 0.01
    Indo-pacific bottlenose       n/a................  Coastal and          NL............        n/a        n/a
     dolphin.                                           continental shelf.
    Indo-pacific hump-backed      n/a................  Coastal............  NL............        n/a        n/a
     dolphin.
    Killer whale................  Common.............  Ubiquitous.........  NL............       0.01       0.01
    Long-beaked common dolphin..  Common.............  Coastal and          NL............     < 0.01     < 0.01
                                                        continental shelf.
    Long-finned pilot whale.....  Rare...............  Continental shelf    NL............       0.05       0.10
                                                        and slope and
                                                        pelagic.
    Pantropical spotted dolphin.  Indeterminate......  Coastal and pelagic  NL............       0.01       0.01
    Pygmy killer whale..........  Rare...............  Deep water.........  NL............     < 0.01     < 0.01
    Risso's dolphin.............  Common.............  Deep water.........  NL............       0.06       0.10
    Rough-toothed dolphin.......  Rare...............  Deep water.........  NL............     < 0.01     < 0.01
    Short-beaked common dolphin.  Common.............  Continental shelf    NL............       0.24       0.38
                                                        and slope and
                                                        pelagic.
    Short-finned pilot whale....  Rare...............  Pelagic............  NL............       0.03       0.04
    Southern right whale dolphin  Common.............  Deep water.........  NL............       0.01       0.02
    Spinner dolphin.............  Common.............  Coastal and pelagic  NL............     < 0.01       0.01
    Striped dolphin.............  Common.............  Continental shelf    NL............       0.19       0.31
                                                        and slope and
                                                        pelagic.
Pinnipeds
    Cape fur seal...............  Rare...............  Islands and          NL............       0.04        n/a
                                                        mainland.
----------------------------------------------------------------------------------------------------------------
n/a Not available or not assessed.
\1\ U.S. Endangered Species Act: EN = Endangered, T = Threatened, NL = Not listed.
\18\ Galapagos Islands (Alava and Salazar, 2006).

    Refer to section 2.0 of the Navy'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 the Navy calculated the estimated densities for the marine mammals 
in the proposed survey area. While Table 3 lists all 40 species known 
to inhabit the proposed survey area, the Navy is only requesting take 
authorization for 29 species. The Navy does not anticipate take, nor is 
NMFS proposing to authorize take, for the following species: Blue 
whale, Bryde's whale, dwarf sperm whale, pygmy right whale, pygmy sperm 
whale, dusky dolphin, Fraser's dolphin, heaviside's dolphin, Indo-
Pacific bottlenose dolphin, Indo-Pacific hump-backed dolphin, and Cape 
fur seal. This is based on population density estimates for cetaceans 
and the total ensonified area of the proposed activity. Cape fur seals 
are not expected to be harassed because their primary habitat is among 
the bays of the South African coastline, more than 30 Nm away from the 
proposed survey activities.

Potential Effects of the Specified Activity on Marine Mammals

    Acoustic stimuli generated by the operation of 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 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 considered an injury but rather a type of Level B harassment 
(Southall et al., 2007). Although the possibility cannot be entirely 
excluded, it is unlikely that the

[[Page 71945]]

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 mammal 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). Marine mammals are 
highly dependent on sound, and their ability to recognize sound signals 
amid other noise is important in communication, predator and prey 
detection, and, in the case of toothed whales, echolocation. 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). Even in the absence of manmade sounds, 
the sea is usually noisy. Background ambient noise often interferes 
with or masks the ability of an animal to detect a sound signal even 
when that signal is above its absolute hearing threshold. Natural 
ambient noise includes contributions from wind, waves, precipitation, 
other animals, and (at frequencies above 30 kHz) thermal noise 
resulting from molecular agitation (Richardson et al., 1995). 
Background noise can also include sounds from human activities. Masking 
of natural sounds can result when human activities produce high levels 
of background noise. Conversely, if the background level of underwater 
noise is high, (e.g., on a day with strong wind and high waves), an 
anthropogenic noise source will not be detectable as far away as would 
be possible under quieter conditions and will itself be masked.
    Masking effects of pulsed sounds on marine mammal calls and other 
natural sounds are expected to be limited. Because of the intermittent 
nature and low duty cycle of seismic airgun pulses, animals can emit 
and receive sounds in the relatively quiet intervals between pulses. 
However, in some situations, reverberation occurs for much or the 
entire interval between pulses (e.g., Simard et al., 2005; Clark and 
Gagnon, 2006) which could mask calls. Some baleen and toothed whales 
are known to continue calling in the presence of seismic pulses, and 
their calls can usually be heard between the seismic pulses (e.g., 
Richardson et al., 1986; McDonald et al., 1995; Greene et al., 1999; 
Nieukirk et al., 2004; Smultea et al., 2004; Holst et al., 2005a,b, 
2006; and Dunn and Hernandez, 2009). However, Clark and Gagnon (2006) 
reported that fin whales in the northeast Pacific Ocean went silent for 
an extended period starting soon after the onset of a seismic survey in 
the area. Similarly, there has been one report that sperm whales ceased 
calling when exposed to pulses from a very distant seismic ship (Bowles 
et al., 1994). However, more recent studies found that they continued 
calling in the presence of seismic pulses (Madsen et al., 2002; Tyack 
et al., 2003; Smultea et al., 2004; Holst et al., 2006; and Jochens et 
al., 2008). Dolphins and porpoises commonly are heard calling while 
airguns are operating (e.g., Gordon et al., 2004; Smultea et al., 2004; 
Holst et al., 2005a, b; and Potter et al., 2007). The sounds important 
to small odontocetes are predominantly at much higher frequencies than 
are the dominant components of airgun sounds, thus limiting the 
potential for masking.
    Although some degree of masking is inevitable when high levels of 
manmade broadband sounds are introduced into the sea, marine mammals 
have evolved systems and behavior that function to reduce the impacts 
of masking. Structured signals, such as the echolocation click 
sequences of small toothed whales, may be readily detected even in the 
presence of strong background noise because their frequency content and 
temporal features usually differ strongly from those of the background 
noise (Au and Moore, 1988, 1990). The components of background noise 
that are similar in frequency to the sound signal in question primarily 
determine the degree of masking of that signal.
    There is evidence of other marine mammal species continuing to call 
in the presence of industrial activity. For example, bowhead whale 
calls are frequently detected in the presence of seismic pulses, 
although the number of calls detected may sometimes be reduced 
(Richardson et al., 1986; Greene et al., 1999; Blackwell et al., 2009). 
Additionally, annual acoustical monitoring near BP's Northstar 
production facility during the fall bowhead migration westward through 
the Beaufort Sea has recorded thousands of calls each year (for 
examples, see Richardson et al., 2007; Aerts and Richardson, 2008). 
Construction, maintenance, and operational activities have been 
occurring from this facility for more than 10 years. To compensate and 
reduce masking, some mysticetes may alter the frequencies of their 
communication sounds (Richardson et al., 1995a; Parks et al., 2007). 
Masking processes in baleen whales are not amenable to laboratory 
study, and no direct measurements on hearing sensitivity are available 
for these species. It is not currently possible to determine with 
precision the potential consequences of temporary or local background 
noise levels. However, Parks et al. (2007) found that right whales 
altered their vocalizations, possibly in response to background noise 
levels. For species that can hear over a relatively broad frequency 
range, as is presumed to be the case for mysticetes, a narrow band 
source may only cause partial masking. Richardson et al. (1995a) note 
that a bowhead whale

[[Page 71946]]

20 km (12.4 mi) from a human sound source, such as that produced during 
oil and gas industry activities, might hear strong calls from other 
whales within approximately 20 km (12.4 mi), and a whale 5 km (3.1 mi) 
from the source might hear strong calls from whales within 
approximately 5 km (3.1 mi). Additionally, masking is more likely to 
occur closer to a sound source, and distant anthropogenic sound is less 
likely to mask short-distance acoustic communication (Richardson et 
al., 1995a).
    Redundancy and context can also facilitate detection of weak 
signals. These phenomena may help marine mammals detect weak sounds in 
the presence of natural or manmade noise. Most masking studies in 
marine mammals present the test signal and the masking noise from the 
same direction. The sound localization abilities of marine mammals 
suggest that, if signal and noise come from different directions, 
masking would not be as severe as the usual types of masking studies 
might suggest (Richardson et al., 1995). The dominant background noise 
may be highly directional if it comes from a particular anthropogenic 
source such as a ship or industrial site. Directional hearing may 
significantly reduce the masking effects of these noises by improving 
the effective signal-to-noise ratio. In the cases of high-frequency 
hearing by the bottlenose dolphin, beluga whale, and killer whale, 
empirical evidence confirms that masking depends strongly on the 
relative directions of arrival of sound signals and the masking noise 
(Penner et al., 1986; Dubrovskiy, 1990; Bain et al., 1993; Bain and 
Dahlheim, 1994). Toothed whales, and probably other marine mammals as 
well, have additional capabilities besides directional hearing that can 
facilitate detection of sounds in the presence of background noise. 
There is evidence that some toothed whales can shift the dominant 
frequencies of their echolocation signals from a frequency range with a 
lot of ambient noise toward frequencies with less noise (Au et al., 
1974, 1985; Moore and Pawloski, 1990; Thomas and Turl, 1990; Romanenko 
and Kitain, 1992; Lesage et al., 1999). A few marine mammal species are 
known to increase the source levels or alter the frequency of their 
calls in the presence of elevated sound levels (Dahlheim, 1987; Au, 
1993; Lesage et al., 1993, 1999; Terhune, 1999; Foote et al., 2004; 
Parks et al., 2007, 2009; Di Iorio and Clark, 2009; Holt et al., 2009).
    These data demonstrating adaptations for reduced masking pertain 
mainly to the very high frequency echolocation signals of toothed 
whales. There is less information about the existence of corresponding 
mechanisms at moderate or low frequencies or in other types of marine 
mammals. For example, Zaitseva et al. (1980) found that, for the 
bottlenose dolphin, the angular separation between a sound source and a 
masking noise source had little effect on the degree of masking when 
the sound frequency was 18 kHz, in contrast to the pronounced effect at 
higher frequencies. Directional hearing has been demonstrated at 
frequencies as low as 0.5-2 kHz in several marine mammals, including 
killer whales (Richardson et al., 1995). This ability may be useful in 
reducing masking at these frequencies. In summary, high levels of noise 
generated by anthropogenic activities may act to mask the detection of 
weaker biologically important sounds by some marine mammals. This 
masking may be more prominent for lower frequencies. For higher 
frequencies, such as that used in echolocation by toothed whales, 
several mechanisms are available that may allow them to reduce the 
effects of such masking.
    In general, NMFS expects the masking effects of seismic pulses to 
be minor, given the normally intermittent nature of seismic pulses, the 
frequency and output pressure of the dual GI-guns, and the likelihood 
that marine mammals may avoid the sound source.

Behavioral Disturbance

    Behavioral disturbance includes a variety of effects, including 
subtle to conspicuous changes in behavior, movement, and displacement. 
Marine mammal 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 proximity to activities and/or exposed to a particular level 
of 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 and small toothed 
whales, but for many species there are no data on responses to marine 
seismic surveys.
    Baleen Whales--Baleen whales generally tend to avoid operating 
airguns, but avoidance radii are quite variable (reviewed in Richardson 
et al., 1995). Whales are often reported to show no overt reactions to 
pulses from large arrays of airguns at distances beyond a few 
kilometers, even though the airgun pulses remain well above ambient 
noise levels out to much longer distances. However, 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 altering their migration route to varying 
degrees, but within the natural boundaries of the migration corridors.
    Studies of gray, bowhead, and humpback whales have shown that 
seismic pulses with received levels of 160 to 170 dB re: 1 [mu]Pa seem 
to cause obvious avoidance behavior in a substantial fraction of the 
animals exposed (Malme et al., 1986, 1988; Richardson et al., 1995). In 
many areas, seismic pulses from large arrays of airguns diminish to 
those levels at distances ranging from four to 15 km from the source. A 
substantial proportion of the baleen whales within those distances may 
show avoidance or other strong behavioral reactions to the airgun 
array.
    McCauley et al. (1998, 2000) studied the responses of humpback 
whales off western Australia to a full-scale seismic survey with a 16-
airgun array (2,678-in\3\) and to a single airgun (20-in\3\) with 
source level of 227 dB re: 1 [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

[[Page 71947]]

seismic boat. In the 2000 study, they noted localized displacement 
during migration of four to five km by traveling pods and seven to 12 
km by more sensitive resting pods of cow-calf pairs. Avoidance 
distances with respect to the single airgun were smaller but consistent 
with the results from the full array in terms of the received sound 
levels. The mean received level for initial avoidance of an approaching 
airgun was 140 dB re: 1 [mu]Pa for humpback pods containing females, 
and at the mean closest point of approach distance the received level 
was 143 dB re: 1 [mu]Pa. The initial avoidance response generally 
occurred at distances of five to eight km from the airgun array and two 
km from the single airgun. However, some individual humpback whales, 
especially males, approached within distances of 100 to 400 m (328 to 
1,312 ft), where the maximum received level was 179 dB re: 1 [mu]Pa.
    Humpback whales on their summer feeding grounds in southeast Alaska 
did not exhibit persistent avoidance when exposed to seismic pulses 
from a 1.64-L (100-in\3\) airgun (Malme et al., 1985). Some humpbacks 
seemed ``startled'' at received levels of 150 to 169 dB re: 1 [mu]Pa. 
Malme et al. (1985) concluded that there was no clear evidence of 
avoidance, despite the possibility of subtle effects, at received 
levels up to 172 dB re: 1 [mu]Pa.
    Studies have suggested that south Atlantic humpback whales 
wintering off Brazil may be displaced or even strand upon exposure to 
seismic surveys (Engel et al., 2004). The evidence for this was 
circumstantial and subject to alternative explanations (IAGC, 2004). 
Also, the evidence was not consistent with subsequent results from the 
same area of Brazil (Parente et al., 2006), or with direct studies of 
humpbacks exposed to seismic surveys in other areas and seasons. After 
allowance for data from subsequent years, there was no observable 
direct correlation between strandings and seismic surveys (IWC, 
2007:236).
    There are no data on reactions of right whales to seismic surveys, 
but results from the closely-related bowhead whale show that their 
responsiveness can be quite variable depending on their activity 
(migrating versus feeding). Bowhead whales migrating west across the 
Alaskan Beaufort Sea in autumn, in particular, are unusually 
responsive, with substantial avoidance occurring out to distances of 20 
to 30 km from a medium-sized airgun source at received sound levels of 
around 120 to 130 dB re: 1 [mu]Pa (Miller et al., 1999; Richardson et 
al., 1999; see Appendix B (5) of L-DEO's environmental analysis). 
However, more recent research on bowhead whales (Miller et al., 2005; 
Harris et al., 2007) corroborates earlier evidence that, during the 
summer feeding season, bowheads are not as sensitive to seismic 
sources. Nonetheless, subtle but statistically significant changes in 
surfacing-respiration-dive cycles were evident upon statistical 
analysis (Richardson et al., 1986). In the summer, bowheads typically 
begin to show avoidance reactions at received levels of about 152 to 
178 dB re: 1 [mu]Pa (Richardson et al., 1986, 1995; Ljungblad et al., 
1988; Miller et al., 2005).
    Reactions of migrating and feeding (but not wintering) gray whales 
to seismic surveys have been studied. Malme et al. (1986, 1988) studied 
the responses of feeding eastern Pacific gray whales to pulses from a 
single 100-in\3\ airgun off St. Lawrence Island in the northern Bering 
Sea. They estimated, based on small sample sizes, that 50 percent of 
feeding gray whales stopped feeding at an average received pressure 
level of 173 dB re: 1 [mu]Pa on an (approximate) rms basis, and that 10 
percent of feeding whales interrupted feeding at received levels of 163 
dB re: 1 [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; Angliss and Allen, 2009).
    Toothed Whales--Little systematic information is available about 
reactions of toothed whales to noise pulses. Few studies similar to the 
more extensive baleen whale/seismic pulse work summarized above 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

[[Page 71948]]

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). Similarly, recent 
empirical observations indicate that delphinids have been frequently 
observed within the 160 dB isopleth during seismic survey operations 
(LGL 2009, 2010b). 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.
    Most studies of sperm whales exposed to airgun sounds indicate that 
the sperm whale shows considerable tolerance of airgun pulses (e.g., 
Stone, 2003; Moulton et al., 2005, 2006a; Stone and Tasker, 2006; Weir, 
2008). In most cases the whales do not show strong avoidance, and they 
continue to call. 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, seem to be confined to a smaller radius than 
has been observed for the more responsive of the mysticetes and other 
odontocetes.

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, 
can be limited to a particular frequency range, and can be in varying 
degrees (i.e., a loss of a certain number of dBs of sensitivity). 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). As illustrated 
previously in Table 2, the Melville's airguns are expected to reach or 
exceed 180 dB re: 1 [micro]Pa at 70 m (230 ft).
    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. The established 180-dB re 1 
[micro]Pa (rms) criterion is the received level above which, in the 
view of a panel of bioacoustics specialists convened by NMFS before 
additional TTS measurements for marine mammals became available, one 
could not be certain that there would be no injurious effects, auditory 
or otherwise, to marine mammals. TTS is considered by NMFS to be a type 
of Level B (non-injurious) harassment. The 180-dB level is a shutdown 
criterion applicable to cetaceans, as specified by NMFS (2000) and is 
used to establish an exclusion zone (EZ), as appropriate. NMFS also 
assumes that cetaceans exposed to levels exceeding 160 dB re: 1 [mu]Pa 
(rms) may experience Level B harassment.

[[Page 71949]]

    Researchers have derived TTS information for odontocetes from 
studies on the bottlenose dolphin and beluga. For the one harbor 
porpoise tested, the received level of airgun sound that elicited onset 
of TTS was lower (Lucke et al., 2009). If these results from a single 
animal are representative, it is inappropriate to assume that onset of 
TTS occurs at similar received levels in all odontocetes (cf. Southall 
et al., 2007). Some cetaceans apparently can incur TTS at considerably 
lower sound exposures than are necessary to elicit TTS in the beluga or 
bottlenose dolphin.
    For baleen whales, there are no data, direct or indirect, on levels 
or properties of sound that are required to induce TTS. The frequencies 
to which baleen whales are most sensitive are assumed to be lower than 
those to which odontocetes are most sensitive, and natural background 
noise levels at those low frequencies tend to be higher. As a result, 
auditory thresholds of baleen whales within their frequency band of 
best hearing are believed to be higher (less sensitive) than are those 
of odontocetes at their best frequencies (Clark and Ellison, 2004). 
From this, it is suspected that received levels causing TTS onset may 
also be higher in baleen whales (Southall et al., 2007).
    Marine mammal hearing plays a critical role in communication with 
conspecifics and in interpretation of environmental cues for purposes 
such as predator avoidance and prey capture. Depending on the degree 
(elevation of threshold in dB), duration (i.e., recovery time), and 
frequency range of TTS and the context in which it is experienced, TTS 
can have effects on marine mammals ranging from discountable to 
serious. For example, a marine mammal may be able to readily compensate 
for a brief, relatively small amount of TTS in a non-critical frequency 
range that takes place during a time when the animal is traveling 
through the open ocean, where ambient noise is lower and there are not 
as many competing sounds present. Alternatively, a larger amount and 
longer duration of TTS sustained during a time when communication is 
critical for successful mother/calf interactions could have more 
serious impacts if it were in the same frequency band as the necessary 
vocalizations and of a severity that it impeded communication. The fact 
that animals exposed to levels and durations of sound that would be 
expected to result in this physiological response would also be 
expected to have behavioral responses of a comparatively more severe or 
sustained nature is also notable and potentially of more importance 
than the simple existence of a TTS. For this proposed study, the Navy 
expects cases of TTS to be improbable given: (1) The slow speed of the 
vessel during survey activities; (2) the motility of free-ranging 
marine mammals in the water column; and (3) the propensity for marine 
mammals to avoid obtrusive sounds.
    Permanent Threshold Shift--When PTS occurs, there is physical 
damage to the sound receptors in the ear. In severe cases, there can be 
total or partial deafness, whereas in other cases, the animal has an 
impaired ability to hear sounds in specific frequency ranges (Kryter, 
1985). There is no specific evidence that exposure to pulses of airgun 
sound can cause PTS in any marine mammal, even with large arrays of 
airguns. However, given the possibility that mammals close to an airgun 
array might incur at least mild TTS, there has been further speculation 
about the possibility that some individuals occurring very close to 
airguns might incur PTS (e.g., Richardson et al., 1995, p. 372ff; 
Gedamke et al., 2008). Single or occasional occurrences of mild TTS are 
not indicative of permanent auditory damage, but repeated or (in some 
cases) single exposures to a level well above that causing TTS onset 
might elicit PTS.
    Relationships between TTS and PTS thresholds have not been studied 
in marine mammals, but are assumed to be similar to those in humans and 
other terrestrial mammals. PTS might occur at a received sound level at 
least several decibels above that inducing mild TTS if the animal were 
exposed to strong sound pulses with rapid rise time. 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 during 
the Navy's proposed activity. Baleen whales generally avoid the 
immediate area around operating seismic vessels, as do some other 
marine mammals.
    Non-auditory Physiological Effects--Non-auditory physiological 
effects or injuries that theoretically might occur in marine mammals 
exposed to strong underwater sound include stress, neurological 
effects, bubble formation, resonance, 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.

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).
    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

[[Page 71950]]

contribute to tissue damage, gas bubble formation, hypoxia, cardiac 
arrhythmia, hypertensive hemorrhage or other forms of trauma;
    (3) A physiological change such as a vestibular response leading to 
a behavioral change or stress-induced hemorrhagic diathesis, leading in 
turn to tissue damage; and
    (4) Tissue damage directly from sound exposure, such as through 
acoustically-mediated bubble formation and growth or acoustic resonance 
of tissues. Some of these mechanisms are unlikely to apply in the case 
of impulse sounds. However, there are increasing indications that gas-
bubble disease (analogous to the bends), induced in supersaturated 
tissue by a behavioral response to acoustic exposure, could be a 
pathologic mechanism for the strandings and mortality of some deep-
diving cetaceans exposed to sonar. Still, 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 survey was 
inconclusive and not based on any physical evidence (Hogarth, 2002; 
Yoder, 2002). Nonetheless, the Gulf of California incident plus the 
beaked whale strandings near naval exercises involving use of mid-
frequency sonar suggests a need for caution in conducting seismic 
surveys in areas occupied by beaked whales until more is known about 
effects of seismic surveys on those species (Hildebrand, 2005). No 
injuries of beaked whales are anticipated during the proposed study 
because of:
    (1) The high likelihood that any beaked whales nearby would avoid 
the approaching vessel before being exposed to high sound levels,
    (2) Differences between the sound sources operated from the 
Melville and those involved in the naval exercises associated with 
strandings.

Potential Effects of Other Acoustic Devices

    As previously mentioned, the Kongsberg EM 122 MBES generates short 
acoustic pulses for 2 to 100 ms every 1.5 to 20 s, depending on water 
depth. Acoustic output frequency is 12 kHz and the maximum source level 
is 242 dB re 1 [mu]Pa.m. The Knudsen 320B/R SBP generates short 
acoustic pulses of 0.8 to 24 ms at 0.5 to 8 s intervals. Pulse 
frequency is 3.5 kHz and the maximum source level is 211 dB re 1 
[mu]Pa.m. The TRDI OS ADCP would operate at 38 kHz with sound output 
pressure level of 224 dB re 1 [mu]P.m, producing a ping every 0.2 to 6 
s. L-ADCPs would operate at 300 kHz with an output pressure level of 
216 dB re 1 [mu]P.m. Moored L-R ADCPs would operate at 75 kHz with an 
output pressure level of 200 dB re 1 [mu]P.m and pulse interval of 2 s.
    The MBES, SBP, and TRDI OS ADCP would operate from the Melville 
during the proposed study to verify seafloor conditions and collect 
additional seafloor bathymetric data. The MBES and SBP would operate 
continuously, and concurrent, with airgun operations. The TRDI OS ADCP 
would operate intermittently to map the distribution of water currents 
and suspended materials in the water column, and would also operate 
concurrent with the dual GI-gun array. The moored LR-ADCPs would 
operate continuously for approximately 14 days, and L-ADCPs deployed 
intermittently, to collect hydrographic data.
    Marine mammals would need to be within 100 m of the hull mounted 
MBES (highest acoustic pressure) to experience a received level of ~185 
dB re 1 [mu]Pa2.s and the potential for TTS. If exposed to the MBES or 
SBP, it is unlikely that animals would be ensonified for more than a 
single pulse of >10 ms, given the narrowness of the acoustic beamwidths 
of all instruments, and mobile nature of the vessel and free-ranging 
marine mammals. Kremser et al. (2005) concluded that an animal would 
have to pass through the area ensonified by an MBES/SBP transducer at 
close range, and be moving at a speed and bearing similar to that of 
the vessel to be subjected to the multiple pulses and sound levels 
sufficient to cause harm. Similarly, Burkhardt et al. (2007) suggest 
that auditory injury is possible only if a cetacean dove into the 
immediate vicinity of a transducer. Standard echosounding instruments, 
such as the MBES and SBP, are considered to present a low risk of TTS 
or auditory injury, given that an individual would have to be within 
the acoustic beam field, ~10 m or less from the transducer, and receive 
exposure to 250 to 1000 acoustic pulses to be at risk for TTS (Boebel 
et al., 2004). Based in part on the foregoing discussion, NMFS has 
determined that brief exposure of marine mammals to a single pulse, or 
small numbers of pulses from an MBES or SBP, is not likely to result in 
the harassment of marine mammals (NMFS 2010a, b, 2011b).
    The shipboard TRDI OS ADCP operates at similar frequencies and duty 
cycles, generates a relatively narrow beamwidth, and is not expected to 
pose any significant risk to marine mammals for the same reasons that 
MBES and SBP present a low risk of harassment. In summary, due to (a) 
The narrow and directional acoustic beam fields of these instruments; 
(b) the relatively high frequencies of the MBES, SBP and TRDI OS ADCP; 
(c) the motility of both free-ranging marine animals and the vessel; 
and (d) the fact that an animal's bearing and speed would need to 
parallel that of the vessel to receive exposure to sound pressure for 
any significant period of time; harassment of marine mammals is 
considered to be of low probability. The likelihood of hearing 
impairment and other physiological effects occurring is considered to 
be very low.
    The LR- and L-ADCP source frequencies of 75 kHz and 300 kHz, 
respectively, are also not expected to

[[Page 71951]]

pose any significant risk to marine mammals. Neither of the ADCP output 
frequencies overlap the predominant communication frequencies employed 
by mysticetes (upper hearing threshold of mysticetes is ~30 kHz), which 
would preclude any significant masking in these species. The L-ADCP 
generates sound at 300 kHz, which is inaudible to marine mammals. The 
moored LR-ADCPs would operate at a depth of about 500 m (1640 feet), 
which exceeds the average diving depths of the majority of marine 
mammals in the research area. Of the deep diving marine mammals, beaked 
whales (recorded at depths of 2,000 m) have peak auditory sensitivity 
between 5 kHz and 80 kHz. Hence, the 75 kHz tone generated by the LR-
ADCPs would be at the upper limit of the beaked whales hearing 
threshold, and not expected to pose a significant risk in terms of TTS 
or PTS, or result in significant behavioral responses. The sperm whale 
(recorded at depths of 3,000 m) generates clicks in the 2 to 4 kHz and 
10 to16 kHz frequency ranges. No direct testing of hearing has been 
performed on sperm whales, although it is assumed sperm whales hear at 
the same frequencies at which they vocalize. As such, significant 
exposure of sperm whales to the LR-ADCP sound sources would not be 
expected to occur. Sound generated by the LR-ADCPs is above the 
auditory threshold of humpback and southern right whales. The fin whale 
has a known maximum dive depth of 500 m, although the mean depth of 
dives is substantially less. Given these factors, the fairly rapid 
attenuation of high-frequency sound in seawater, and the motility of 
free-ranging marine mammals in the water column, significant exposure 
of marine mammals to the LR- and L-ADCPs is expected to be of low 
probability.
    Considering the foregoing factors discussed, the potential for the 
adverse effects of masking, tolerance, TTS/PTS, and non-auditory 
physiological injury as a result of operation of the MBES, SBP, TRDI OS 
ADCP, LR-ADCP or L-ADCP is considered to be very low. Marine mammal 
communication and hearing is not expected to be significantly masked by 
these instruments, given the relatively low duty cycles and brief 
period of exposure an individual marine mammal may receive if 
transiting an acoustic beam field. Any behavioral reactions that result 
from exposure to these sources are anticipated to be short-term, and 
limited to avoidance of the sound source.
    Based on this assessment, previously conducted oceanographic 
research using same or similar instrumentation and procedures and 
environmental studies associated with these previous actions (e.g., 
NMFS 2004, 2010a, b), and current literature (Boebel et al. 2004; 
Breitzke and Bohlen 2010; Costa et al. 2003; Kastak et al. 2005; Popper 
2008; Popper and Hastings 2009a; Richardson et al. 1995; Tyack 2008, 
2009), operation of the MBES, SBP, TRDI OS ADCP and deployed ADCPs is 
not expected to result in any significant adverse impact on marine 
mammals, their habitats, or food sources. Of the potential adverse 
effects, short-term behavioral responses primarily in the way of 
avoidance of the vessel, LR-ADCPs, and L-ADCPs is considered the only 
type of effect that will likely occur as a result of operation of these 
acoustic sources.
    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).

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. 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 (Hastings and 
Popper, 2005). Potential adverse effects of the program's sound sources 
on marine fish are then noted.
    Pathological Effects--The potential for pathological damage to 
hearing structures in fish depends on the energy level of the received 
sound and the physiology and hearing capability of the species in 
question. For a given sound to result in hearing loss, the sound must 
exceed, by some substantial amount, the hearing threshold of the fish 
for that sound (Popper, 2005). The consequences of temporary or 
permanent hearing loss in individual fish on a fish population are 
unknown; however, they likely depend on the number of individuals 
affected and whether critical behaviors involving sound (e.g., predator 
avoidance, prey capture, orientation and navigation, reproduction, 
etc.) are adversely affected.
    Little is known about the mechanisms and characteristics of damage 
to fish that may be inflicted by exposure to seismic survey sounds. Few 
data have

[[Page 71952]]

been presented in the peer-reviewed scientific literature. As far as we 
know, there are only two papers with proper experimental methods, 
controls, and careful pathological investigation implicating sounds 
produced by actual seismic survey airguns in causing adverse anatomical 
effects. One such study indicated anatomical damage, and the second 
indicated TTS in fish hearing. The anatomical case is McCauley et al. 
(2003), who found that exposure to airgun sound caused observable 
anatomical damage to the auditory maculae of pink snapper (Pagrus 
auratus). This damage in the ears had not been repaired in fish 
sacrificed and examined almost two months after exposure. On the other 
hand, Popper et al. (2005) documented only TTS (as determined by 
auditory brainstem response) in two of three fish species from the 
Mackenzie River Delta. This study found that broad whitefish (Coregonus 
nasus) 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., 2000 a, b, 2003; Bjarti, 2002; 
Thomsen, 2002; Hassel et al., 2003; Popper et al., 2005; Boeger et al., 
2006).
    Some studies have reported, some equivocally, that mortality of 
fish, fish eggs, or larvae can occur close to seismic sources 
(Kostyuchenko, 1973; Dalen and Knutsen, 1986; Booman et al., 1996; 
Dalen et al., 1996). Some of the reports claimed seismic effects from 
treatments quite different from actual seismic survey sounds or even 
reasonable surrogates. However, Payne et al. (2009) reported no 
statistical differences in mortality/morbidity between control and 
exposed groups of capelin eggs or monkfish larvae. Saetre and Ona 
(1996) applied a ``worst-case scenario'' mathematical model to 
investigate the effects of seismic energy on fish eggs and larvae. They 
concluded that mortality rates caused by exposure to seismic surveys 
are so low, as compared to natural mortality rates, that the impact of 
seismic surveying on recruitment to a fish stock must be regarded as 
insignificant.
    Physiological Effects--Physiological effects refer to cellular and/
or biochemical responses of fish to acoustic stress. Such stress 
potentially could affect fish populations by increasing mortality or 
reducing reproductive success. Primary and secondary stress responses 
of fish after exposure to seismic survey sound appear to be temporary 
in all studies done to date (Sverdrup et al., 1994; Santulli et al., 
1999; McCauley et al., 2000a, b). The periods necessary for the 
biochemical changes to return to normal are variable and depend on 
numerous aspects of the biology of the species and of the sound 
stimulus.
    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).
    The only information available on the impacts of seismic surveys on 
marine invertebrates involves studies of individuals; there have been 
no studies at the population scale. Thus, available information 
provides limited insight on possible real-world effects at the regional 
or ocean scale. The most important aspect of potential impacts concerns 
how exposure to seismic survey sound ultimately affects invertebrate 
populations and their viability, including availability to fisheries.
    Literature reviews of the effects of seismic and other underwater 
sound on invertebrates were provided by Moriyasu et al. (2004) and 
Payne et al. (2008). The following sections provide a synopsis of 
available information on the effects of exposure to seismic survey 
sound on species of decapod

[[Page 71953]]

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.
    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 
survey, the pathological (mortality) zone for crustaceans and 
cephalopods is expected to be less than a few meters of the seismic 
source; however, very few specific data are available on levels of 
seismic signals that might damage these animals. This premise is based 
on the peak pressure and rise/decay time characteristics of seismic 
airgun arrays currently in use around the world.
    Some studies have suggested that seismic survey sound has a limited 
pathological impact on early developmental stages of crustaceans 
(Pearson et al., 1994; Christian et al., 2003; DFO, 2004). However, the 
impacts appear to be either temporary or insignificant compared to what 
occurs under natural conditions. Controlled field experiments on adult 
crustaceans (Christian et al., 2003, 2004; DFO, 2004) and adult 
cephalopods (McCauley et al., 2000a, b) exposed to seismic survey sound 
have not resulted in any significant pathological impacts on the 
animals. It has been suggested that exposure to commercial seismic 
survey activities has injured giant squid (Guerra et al., 2004), but 
the article provides little evidence to support this claim.
    Physiological Effects--Physiological effects refer mainly to 
biochemical responses by marine invertebrates to acoustic stress. Such 
stress potentially could affect invertebrate populations by increasing 
mortality or reducing reproductive success. Primary and secondary 
stress responses (i.e., changes in haemolymph levels of enzymes, 
proteins, etc.) of crustaceans have been noted several days or months 
after exposure to seismic survey sounds (Payne et al., 2007). The 
periods necessary for these biochemical changes to return to normal are 
variable and depend on numerous aspects of the biology of the species 
and of the sound stimulus.
    Behavioral Effects--There is increasing interest in assessing the 
possible direct and indirect effects of seismic and other sounds on 
invertebrate behavior, particularly in relation to the consequences for 
fisheries. Changes in behavior could potentially affect such aspects as 
reproductive success, distribution, susceptibility to predation, and 
catchability by fisheries. Studies investigating the possible 
behavioral effects of exposure to seismic survey sound on crustaceans 
and cephalopods have been conducted on both uncaged and caged animals. 
In some cases, invertebrates exhibited startle responses (e.g., squid 
in McCauley et al., 2000a, b; juvenile cuttlefish in Komak et al. 
2005). 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). In general, 
data on which to assess the potential adverse effects of GI-gun sounds 
on invertebrate species is rather ambiguous; however, of the limited 
data available, crustaceans and cephalopods appear sensitive and 
responsive to the frequencies of sound generated by airguns, although 
at sound pressures somewhat higher than that for marine mammals.
    In conclusion, NMFS has preliminarily determined that the Navy's 
proposed marine seismic survey is not expected to have any habitat-
related effects that could cause significant or long-term consequences 
for marine mammals or on the food sources that they utilize.

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 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.
    The Navy has proposed the following mitigation measures to be 
implemented for the proposed seismic survey:

Exclusion Zones

    The Navy used the exposure threshold isopleths applicable to 
cetaceans (there is no proposed take for pinnipeds), as well as extant 
models of same/similar GI-gun sources and water depths, as the basis 
for their exclusion zones. The proposed exclusion zone is 70 m for the 
180 dB exposure thresholds and would be employed for monitoring.

Speed or Course Alteration

    If a marine mammal is observed moving on a path toward an exclusion 
zone, an attempt would be made to adjust the vessel speed or course in 
order to minimize the likelihood of an animal entering an exclusion 
zone. Speed and course alterations are not always possible when towing 
a long GI-gun array, but are considered possible options given the use 
of a dual GI-gun array.

Shut-Down Procedures

    The Navy proposes to shut down the operating airgun array if a 
marine mammal is seen within or approaching an exclusion zone. The Navy 
would implement a shut-down if a cetacean is observed within or 
approaching the 180 dB isopleth (70 m). Airgun activity would not 
resume until the marine mammal has cleared the exclusion zone or has 
not been seen for 15 (dolphins) to 30 minutes (whales).

Ramp-Up Procedures

    Ramp-up would be comprised of gradually activating the dual GI-guns 
in sequence over a period of about 30 min until the desired operating 
level is reached. This should allow any marine mammals in the area to 
avoid the maximum sound source. Airguns would be activated in a 
sequence such that the source level of the array would increase in 
steps not exceeding 6 dB per 5-min periods over a total duration of 30 
min. During ramp-up, protected species observers would monitor the 
exclusion zones for marine mammals and a shutdown would be implemented 
if an animal is detected in or approaching an exclusion zone.
    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 impact on the affected marine mammal species and stocks and 
their habitat. Our evaluation of potential measures included 
consideration of the following

[[Page 71954]]

factors in relation to one another: (1) The manner in which, and the 
degree to which, the successful implementation of the measure is 
expected to minimize adverse impacts to marine mammals; (2) the proven 
or likely efficacy of the specific measure to minimize adverse impacts 
as planned; and (3) the practicability of the measure for applicant 
implementation.
    Based on our evaluation of the applicant's proposed measures, NMFS 
has preliminarily determined that the proposed mitigation measures 
provide the means of effecting the least practicable impacts on marine 
mammals 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 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

    The Navy proposes to sponsor marine mammal monitoring during the 
proposed activity, in order to implement the proposed mitigation 
measures that require real-time monitoring, and to satisfy the 
anticipated monitoring requirements of the IHA. The Navy's proposed 
Monitoring Plan is described below this section. The Navy understands 
that this monitoring plan will be subject to review by NMFS, and that 
refinements may be required.

Vessel-Based Visual Monitoring

    The Navy proposes to continuously monitor the harassment isopleths 
during daytime and nighttime airgun operations. Visual monitoring would 
be comprised of three protected species observers (PSOs) typically 
working in shift of 4-hr durations or less. A PSO platform is located 
one deck below and forward of the bridge (12.5 m [41 ft] above the 
waterline), providing a relatively unobstructed 180 degree view 
forward. Aft views can be obtained along both the port and starboard 
decks. During daytime operations, PSOs would systematically survey the 
area around the vessel with reticle and big-eye binoculars and the 
naked eye. A clinometer would be used to determine distances of animals 
in close proximity to the vessel, and hand-held fixed rangefinders and 
distance marks on the Melville's side rails would be used to measure 
the exact location of the exclusion zones. During nighttime operations, 
night vision devices would be available if required.
    The PSOs would be in wireless communication with ship's officers on 
the bridge and scientists in the vessel's operations laboratory, so 
they can promptly advise of the need for avoidance maneuvers or seismic 
source shutdown. Shutdown of GI-gun operations would occur immediately 
upon observation/detection of any marine mammal in an exclusion zone. 
Following a shutdown, GI-gun ramp-up would not be initiated until PSOs 
have confirmed the marine mammal is no longer observed/detected for a 
period of 15 or 30 minutes (depending on species). If a marine mammal 
is outside of an exclusion zone and observed by a PSO to exhibit 
abnormal behaviors consistent with signs of harassment (e.g., 
avoidance, dive patterns, multiple changes in direction), operation of 
the GI-guns would cease until the animal moves out of the area or is 
not resighted for a period of 30 min.

PSO Data and Documentation

    PSOs 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 
nearing the exclusion zone.
    When a sighting is made, the following information will be 
recorded:
    1. Time, location, heading, speed, activity of the vessel, sea 
state, visibility, and sun glare;
    2. Species, group size, age, individual size, sex (if 
determinable);
    3. Behavior when first sighted and subsequent behaviors;
    4. Bearing and distance from the vessel, sighting cue, exhibited 
reaction to the airgun sounds or vessel (e.g., none, avoidance, 
approach, etc.), behavioral pace, and depth at time of detection;
    5. Fin/fluke characteristics and angle of fluke when an animal 
submerges to determine if the animal executed a deep or surface dive;
    6. Type and nature of sounds heard; and
    7. Any other relevant information.
    When shutdown is required for mitigation purposes, the following 
information will be recorded:
    1. The basis for decisions resulting in shutdown of the GI-guns;
    2. Information needed to estimate the number of marine mammals 
potentially taken by harassment;
    3. Information on the frequency of occurrence, distribution, and 
activities of marine mammals in the study area;
    4. Information on the behaviors and movements of marine mammals 
during and without operation of the GI-guns; and
    5. Any adverse effects the shutdown had on the research.
    PSOs would provide estimates of the numbers of marine mammals 
exposed to the GI-gun source and any disturbance reactions exhibited, 
or the lack thereof. Observations and data collection would aim to 
provide estimates of the actual numbers of animals taken, verify the 
level of harassment, aide in assessment of impacts on populations on 
conclusion of the study, and increase knowledge of species in the study 
area. Observations and data collection would also aim to provide 
information that would allow for verifying or disputing that the 
takings are negligible.

Reporting Measures

    The Navy would submit a report to NMFS within 90 days after the end 
of the cruise. The report would describe the operations that were 
conducted and sightings of marine mammals near the operations. The 
report would provide full documentation of methods, results, and 
interpretation pertaining to all monitoring. The 90-day report would 
summarize the dates and locations of seismic operations, and all marine 
mammal sightings (dates, times, locations, activities, associated 
seismic survey activities). The report would also include estimates of 
the number and nature of exposures that could result in ``takes'' of 
marine mammals.
    In the unanticipated event that the specified activity clearly 
causes the take of a marine mammal in a manner prohibited by the IHA 
(if issued), such as an injury (Level A harassment), serious injury, or 
mortality (e.g., ship-strike, gear interaction, and/or entanglement), 
the Navy would immediately cease the specified activities and 
immediately report the incident to the Chief of the Permits and 
Conservation Division, Office of Protected Resources, NMFS. The report 
must include the following information:

[[Page 71955]]

     Time, date, and location (latitude/longitude) of the 
incident;
     Name and type of vessel involved;
     Vessel's speed during and leading up to the incident;
     Description of the incident;
     Status of all sound source use in the 24 hrs preceding the 
incident;
     Water depth;
     Environmental conditions (e.g., wind speed and direction, 
Beaufort sea state, cloud cover, and visibility);
     Description of all marine mammal observations in the 24 
hrs preceding the incident;
     Species identification or description of the animal(s) 
involved;
     Fate of the animal(s); and
     Photographs or video footage of the animal(s) (if 
equipment is available).

Activities would not resume until NMFS is able to review the 
circumstances of the prohibited take. NMFS would work with the Navy to 
determine what is necessary to minimize the likelihood of further 
prohibited take and ensure MMPA compliance. The Navy may not resume 
their activities until notified by NMFS via letter, email, or 
telephone.
    In the event that the Navy discovers an injured or dead marine 
mammal, and the lead PSO determines that the cause of the injury or 
death is unknown and the death is relatively recent (i.e., in less than 
a moderate state of decomposition as described in the next paragraph), 
the Navy would immediately report the incident to the Chief of the 
Permits and Conservation Division, Office of Protected Resources, NMFS. 
The report must include the same information identified in the 
paragraph above. Activities may continue while NMFS reviews the 
circumstances of the incident. NMFS would work with the Navy to 
determine whether modifications in the activities are appropriate.
    In the event that the Navy discovers an injured or dead marine 
mammal, and the lead PSO determines that the injury or death is not 
associated with or related to the activities authorized in the IHA 
(e.g., previously wounded animal, carcass with moderate to advanced 
decomposition, or scavenger damage), the Navy would report the incident 
to the Chief of the Permits and Conservation Division, Office of 
Protected Resources, NMFS within 24 hrs of the discovery. The Navy 
would provide photographs or video footage (if available) or other 
documentation of the stranded animal sighting to NMFS.

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 proposed to be 
authorized as a result of the proposed physical oceanographic survey 
off the southern coast of Africa. Acoustic stimuli (i.e., increased 
underwater sound) generated during the operation of the dual 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 would result in injury, serious injury, or mortality within 
the specified geographic area for which the Navy seeks the IHA. The 
mitigation and monitoring measures proposed for implementation are 
expected to minimize any potential risk for injury or mortality.
    The following sections describe the Navy's methods to estimate take 
by incidental harassment and present the applicant's estimates of the 
numbers of marine mammals that could be taken during the proposed 
physical oceanographic survey. The estimates are based on a 
consideration of the number of marine mammals that could be disturbed 
appreciably by operations with the GI-gun array to be used during 
multiple transects totaling approximately 2,489 km (1,547 mi).
    The Navy 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. Therefore, the Navy provides no 
additional allowance for animals that could be affected by sound 
sources other than airguns.
    Density estimates on the marine mammal species in the proposed 
survey area are based on data derived from a number of sources: The 
Ocean Biogeographic Information System OBIS Seamap (OBIS-SEAMP); the 
International Union for Conservation of Nature (IUCN, 2010); the 
Convention on the Conservation of Migratory Species of Wild Animals 
(CMS, 2010); NatureServe Explorer (NatureServe, 2010); the 
International Whaling Commission (IWC); NOAA Fisheries Office of 
Protected Resources; and the Navy Marine Species Density Database 
(NMSDD); unless otherwise cited. The NMSDD includes the highest 
quality, spatially modeled, density data where data is available. For 
all other geographic areas, data were evaluated using a hierarchical 
approach and a review process to incorporate the best data available. 
The NMSDD incorporates density from global predictive relative 
environmental suitability models for geographic areas where no survey 
data or density estimates exist. The global predictive estimates for 
areas beyond survey coverage are available in two forms: (1) Sea Mammal 
Research Unit Limited (SMRUL) that includes survey-based density 
estimates in the prediction of densities estimated elsewhere within 
Food and Agriculture Organization (FAO) areas; and (2) predictions from 
Kristin Kaschner which are based on using relative environmental 
suitability as an index in conjunction with a global mean population 
estimate determined from literature (Kaschner et al., 2006). The 
resulting data within the NMFSDD provide the best available, single 
density value for a selected geographic area and time.
    One method of estimating takes assumes marine mammals are uniformly 
distributed throughout a given area, although this is not 
representative of the real world distribution of marine mammals in any 
given geographic region. Marine mammals are typically found grouped in 
pods, concentrate around preferred breeding and foraging habitats, and 
most species follow seasonal migratory patterns and routes. However, 
due to lack of substantive information on marine mammal population 
distributions and densities in the area of the proposed action, 
informed assumptions on distribution patterns cannot be made, and 
exposure estimates are based on uniform distribution of marine mammals 
over the area for which population data are available. Bearing these 
factors in mind, the exposure estimates provided are considered 
reasonable approximations of potential exposure, and based on the best 
available information.

[[Page 71956]]

    Marine mammal population density estimates for the area and time of 
year of study provide species of cetacea that would be expected to be 
present in the study area during the time research activities would be 
conducted. Many species are unlikely to be significantly populous in 
the proposed area of study during the research time frame, as the 
austral summer migration finds many of the migratory species in the 
Antarctic waters of the Southern Ocean, typically south of 40[deg] S. 
The only known commonly sighted whales year-round off the South African 
coast is an in-shore sub-species of Bryde's whale and the Southern 
right whale. In general, whales are most populous in the study area 
during the austral winter months, from approximately June to November, 
and populations are at their lowest during the austral summer.
    Table 3 provides estimates of the minimum, average (considered the 
best estimate), and maximum marine mammal population densities in the 
area of the proposed study during the austral summer, anticipated 
occurrence of each species, and requested take authorization. For all 
species evaluated, average population density estimates were used for 
calculation of the number of marine mammals that may be exposed. NMFS 
has used average (or best) population density estimates when analyzing 
the allowable harassment for ESA-listed marine mammals incidental to 
marine seismic surveys for scientific research purposes (e.g., see NMFS 
2010c, 2011c). The results of the monitoring reports from those 
surveys, and others, show that the use of the average estimate is 
appropriate for provision of reasonable estimates of exposure and 
harassment. Requested takes estimates are based on Navy exposure 
criteria, which determines take at 0.5 animals exposed for non-ESA-
listed marine mammals, and 0.05 animals exposed for ESA-listed species. 
In other words, if 0.5-0.9 non-ESA animals are expected to be exposed 
to sounds above 160 dB, the value is rounded up to one; for ESA-listed 
animals, the value is rounded up to one if 0.05-0.9 individuals are 
expected to be exposed to sounds above 160 dB.
    Because extant mathematical models poorly simulate and predict the 
natural meander of the AC, ARC, and ARC/ACC frontal system, and due to 
unpredictable weather conditions, it is not possible to accurately 
predict the exact location where seismic oceanographic survey transects 
would occur. For this reason, the minimum, average, and maximum 
population densities given in Table 3 are the mean of the population 
densities for each species within the coordinates of 36[deg] S to 
43[deg] S, and 19[deg] E to 30[deg] E. Therefore, the mean of the 
minimum, average, and maximum marine mammal population density values 
for each square kilometer of this region were used in order to (1) 
capture the uncertainty as to exactly where the SO survey will take 
place, and (2) the inherent uncertainty in marine mammal population 
density estimates. The front is estimated to be phase-locked between 
36[deg] S to 40[deg] S, and 21[deg] E to 27[deg] E; however, the 
position of the front can vary by up to 100 km (generally west, east, 
and south of this estimated location). Because the precise location of 
the seismic oceanography survey transects cannot be known in advance, 
it is not possible to accurately differentiate the numbers of marine 
mammals that may be exposed in waters of the global commons (high 
seas), as opposed to within the South African exclusive economic zone 
(EEZ). Because the specific location of research activities cannot be 
predetermined, due to the variables described, this assessment 
conservatively estimates that all exposures occur in waters of the 
global commons (high seas) where estimated population density estimates 
are higher.
    Based on the best available population density estimates, 2,410 
cetacea may potentially be exposed to sound pressure levels >= 160 dB 
re 1 [mu]Pa.rms. Of the total number of cetaceans that are estimated to 
be exposed, 60 are listed as endangered under the ESA: 29 fin (< 0.2% 
of the southern hemisphere population), 1 humpback (< 0.004% of the 
southern hemisphere population), 10 sei (< 0.2% of the population south 
of 30[deg] S), 1 southern right (< 0.004% of the southern hemisphere 
population), and 19 sperm (< 0.02% of the southern hemisphere 
population) whales. For all species, the number of individuals that 
would be exposed to sounds >= 160 dB re 1 [mu]Pa.rms is less than 0.2 
percent of the given species' population for which regional population 
density estimates are known.

          Table 3--Estimated Number of Marine Mammals Exposed to >=160 dB During the Proposed Activity
----------------------------------------------------------------------------------------------------------------
                                                                      Density
           Species                  ESA \1\      ------------------------------------------------ Requested take
                                                       Best             Min             Max
----------------------------------------------------------------------------------------------------------------
Mysticetes
    Antarctic minke whale....  NL...............          < 0.01          < 0.01            0.01              14
    Blue whale...............  E................          < 0.01          < 0.01          < 0.01               0
    Bryde's whale............  NL...............          < 0.01          < 0.01          < 0.01               0
    Common minke whale.......  NL...............            0.03            0.02            0.05             103
    Fin whale................  E................            0.01          < 0.01            0.01              29
    Humpback whale...........  E................          < 0.01          < 0.01          < 0.01               1
    Sei whale................  E................          < 0.01          < 0.01          < 0.01              10
Odontocetes
    Arnoux's beaked whale....  NL...............          < 0.01          < 0.01            0.01              15
    Cuvier's beaked whale....  NL...............          < 0.01          < 0.01          < 0.01              12
    Dwarf sperm whale........  NL...............          < 0.01          < 0.01          < 0.01               0
    Gray's beaked whale......  NL...............          < 0.01          < 0.01          < 0.01              11
    Hector's beaked whale....  NL...............          < 0.01          < 0.01          < 0.01               9
    Pygmy right whale........  NL...............          < 0.01          < 0.01          < 0.01               0
    Pygmy sperm whale........  NL...............          < 0.01          < 0.01          < 0.01               0
    Southern bottlenose whale  NL...............          < 0.01          < 0.01            0.01              21
    Southern right whale.....  E................          < 0.01          < 0.01          < 0.01               1
    Sperm whale..............  E................            0.01          < 0.01            0.01              19
    Strap-toothed whale......  NL...............          < 0.01          < 0.01          < 0.01               9
    True's beaked whale......  NL...............          < 0.01          < 0.01          < 0.01              10
    Common bottlenose dolphin  NL...............            0.04            0.01            0.10             141
    Dusky dolphin............  NL...............          < 0.01          < 0.01          < 0.01               0
    False killer whale.......  NL...............          < 0.01          < 0.01          < 0.01               1

[[Page 71957]]

 
    Fraser's dolphin.........  NL...............             n/a             n/a             n/a               0
    Heaviside's dolphin......  NL...............          < 0.01          < 0.01            0.01               0
    Hourglass dolphin........  NL...............          < 0.01          < 0.01          < 0.01               3
    Indo-pacific bottlenose    NL...............             n/a             n/a             n/a               0
     dolphin.
    Indo-pacific hump-backed   NL...............             n/a             n/a             n/a               0
     dolphin.
    Killer whale.............  NL...............            0.01          < 0.01            0.01              30
    Long-beaked common         NL...............          < 0.01          < 0.01          < 0.01               1
     dolphin.
    Long-finned pilot whale..  NL...............            0.05          < 0.01            0.10             180
    Pantropical spotted        NL...............            0.01          < 0.01            0.01              20
     dolphin.
    Pygmy killer whale.......  NL...............          < 0.01          < 0.01          < 0.01               1
    Risso's dolphin..........  NL...............            0.06            0.04            0.10             210
    Rough-toothed dolphin....  NL...............          < 0.01          < 0.01          < 0.01               2
    Short-beaked common        NL...............            0.24            0.13            0.38             799
     dolphin.
    Short-finned pilot whale.  NL...............            0.03            0.01            0.04              86
    Southern right whale       NL...............            0.01          < 0.01            0.02              29
     dolphin.
    Spinner dolphin..........  NL...............          < 0.01          < 0.01            0.01              16
    Striped dolphin..........  NL...............            0.19            0.03            0.31             626
Pinnipeds
    Cape fur seal............  NL...............            0.04             n/a             n/a               0
----------------------------------------------------------------------------------------------------------------

    Exposure estimates are based on marine mammal population density 
estimates relative to the total area ensonified by the GI-gun array, 
and evaluated for exposure to the 160 dB isopleth. Multiplying the 
total area ensonified during the seismic oceanography survey by the 
population estimate for each species, yields the estimated number of 
marine mammals exposed to sound pressures > 160 dB. The total 
ensonified area is about 3,335 km\2\ and assumes no area of overlap 
during the survey transects, which would cover a total distance of 
2,489 km.

Negligible Impact and Small Numbers Analysis and Preliminary 
Determination

    NMFS has defined ``negligible impact'' in 50 CFR 216.103 as ``* * * 
an impact resulting from the specified activity that cannot be 
reasonably expected to, and is not reasonably likely to, adversely 
affect the species or stock through effects on annual rates of 
recruitment or survival.'' In making a negligible impact determination, 
NMFS considers a variety of factors, including but not limited to:
    (1) The number of anticipated mortalities;
    (2) The number and nature of anticipated injuries;
    (3) The number, nature, and intensity, and duration of Level B 
harassment; and
    (4) The context in which the takes occur.
    As mentioned previously, NMFS estimates that 29 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 (less than 
one percent) relative to the population size.
    No injuries, serious injuries, or mortalities are anticipated to 
occur as a result of the Navy's planned physical oceanographic survey, 
and none are proposed to be authorized by NMFS. Additionally, for 
reasons presented earlier in this document, temporary hearing 
impairment (and especially permanent hearing impairment) is not 
anticipated to occur during the proposed specified activity. 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 physical oceanographic survey off the southern coast of 
Africa, January through February, 2012, 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.
    Of the ESA-listed marine mammals that may potentially occur in the 
proposed survey area, blue and southern right whale populations are 
thought to be increasing; population trends for fin, humpback, sei, and 
sperm whales are not well known in the southern hemisphere. There is no 
designated critical habitat for marine mammals in the proposed survey 
area. There are also no important habitat areas (e.g., breeding, 
calving, feeding, etc.) for marine mammals known around the area that 
would overlap with the proposed survey. 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 preliminarily 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 the Navy's planned research 
activities would result in the incidental take of small numbers of 
marine mammals, by Level B harassment only, and that the total taking 
from the physical oceanographic survey would have a negligible impact 
on the affected species or stocks.

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

    There are no relevant subsistence uses of marine mammals implicated 
by this action. Therefore, NMFS has

[[Page 71958]]

determined that the total taking of affected species or stocks would 
not have an unmitigable adverse impact on the availability of such 
species or stocks for taking for subsistence purposes.

Endangered Species Act

    Of the species of marine mammals that may occur in the proposed 
survey area, six are listed as endangered under the ESA, including the 
blue, fin, humpback, sei, southern right, and sperm whales. Under 
section 7 of the ESA, the Navy has initiated formal consultation with 
NMFS, Office of Protected Resources, Endangered Species Act Interagency 
Cooperation Division, on this proposed survey. NMFS' Office of 
Protected Resources, Permits and Conservation Division, has also 
initiated formal consultation under section 7 of the ESA with NMFS' 
Office of Protected Resources, Endangered Species Act Interagency 
Cooperation 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, the Navy, in 
addition to the mitigation and monitoring requirements included in the 
IHA, would be required to comply with the Terms and Conditions of the 
Incidental Take Statement corresponding to NMFS' Biological Opinion 
issued to both the Navy and NMFS' Office of Protected Resources, 
Permits and Conservation Division.

National Environmental Policy Act (NEPA)

    The Navy has prepared a draft Overseas Environmental Assessment 
(OEA) to address the potential environmental impacts that could occur 
as a result of the proposed activity. To meet NMFS' National 
Environmental Policy Act (NEPA; 42 U.S.C. 4321 et seq.) requirements 
for the issuance of an IHA to the Navy, NMFS will either adopt the OEA 
(if sufficient) or prepare an independent NEPA analysis. This analysis 
will be completed prior to issuance of a final IHA.

Proposed Authorization

    As a result of these preliminary determinations, NMFS proposes to 
issue an IHA to the Navy for conducting a physical oceanographic survey 
off the southern coast of Africa, provided the previously mentioned 
mitigation, monitoring, and reporting requirements are incorporated.

    Dated: November 15, 2011.
James H. Lecky,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. 2011-30010 Filed 11-18-11; 8:45 am]
BILLING CODE 3510-22-P