[Federal Register Volume 73, Number 228 (Tuesday, November 25, 2008)]
[Notices]
[Pages 71606-71620]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E8-27895]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XK83


Incidental Takes of Marine Mammals During Specified Activities; 
Marine Seismic Surveys in the Southwest Pacific Ocean, January-
February, 2009

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

ACTION:  Notice; proposed incidental take authorization; request for 
comments.

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SUMMARY:  NMFS has received an application from the Lamont-Doherty 
Earth Observatory (L-DEO) for an Incidental Harassment Authorization 
(IHA) to take small numbers of marine mammals, by harassment, 
incidental to conducting a seismic survey in the southwest Pacific 
Ocean. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS 
requests comments on its proposal to authorize L-DEO to take, by Level 
B harassment only, small numbers of marine mammals incidental to 
conducting a marine seismic survey during January through February, 
2009.

DATES:  Comments and information must be received no later than 
December 26, 2008.

ADDRESSES:  Comments on the application should be addressed to Michael 
Payne, Chief, Permits, Conservation and Education Division, Office of 
Protected Resources, National Marine Fisheries Service, 1315 East-West 
Highway, Silver Spring, MD 20910-3225. The mailbox address for 
providing email comments is [email protected]. Comments sent via 
e-mail, including all attachments, must not exceed a 10-megabyte file 
size.
    A copy of the application containing a list of the references used 
in this document may be obtained by writing to the address specified 
above, telephoning the contact listed below (see FOR FURTHER 
INFORMATION CONTACT), or visiting the internet at: http://www.nmfs.noaa.gov/pr/permits/incidental.htm.
    Documents cited in this notice may be viewed, by appointment, 
during regular business hours, at the aforementioned address.

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

SUPPLEMENTARY INFORMATION:

Background

    Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) 
direct the Secretary of Commerce to allow, upon request, the 
incidental, but not intentional, taking of marine mammals by United 
States citizens who engage in a specified activity (other than 
commercial fishing) within a specified geographical region if certain 
findings are made and either regulations are issued or, if the taking 
is limited to harassment, a notice of a proposed authorization is 
provided to the public for review.
    Authorization for incidental taking shall be granted if NMFS finds 
that the taking will have a negligible impact on the species or 
stock(s), will not have an unmitigable adverse impact on the 
availability of the species or stock(s) for subsistence uses, and if 
the permissible methods of taking and requirements pertaining to the 
mitigation, monitoring and reporting of such takings are set forth. 
NMFS has defined ``negligible impact'' in 50 CFR 216.103 as ``...an 
impact resulting from the specified activity that cannot be reasonably 
expected to, and is not reasonably likely to, adversely affect the 
species or stock through effects on annual rates of recruitment or 
survival.''
    Section 101(a)(5)(D) of the MMPA established an expedited process 
by which citizens of the United States can apply for an authorization 
to incidentally take small numbers of marine mammals by harassment. 
Except with respect to certain activities not pertinent here, the MMPA 
defines ``harassment'' as:
    any act of pursuit, torment, or annoyance which (i) has the 
potential to injure a marine mammal or marine mammal stock in the 
wild [``Level A harassment'']; or (ii) has the potential to disturb 
a marine mammal or marine mammal stock in the wild by causing 
disruption of behavioral patterns, including, but not limited to, 
migration, breathing, nursing, breeding, feeding, or sheltering 
[``Level B harassment'';].
    Section 101(a)(5)(D) establishes a 45-day time limit for NMFS' 
review of an application followed by a 30-day public notice and comment 
period on any proposed authorizations for the incidental harassment of 
small numbers of marine mammals. Within 45 days of the close of the 
comment period, NMFS must either issue or deny issuance of the 
authorization.

Summary of Request

    On August 18, 2008, NMFS received an application from L-DEO for the 
taking by Level B harassment only, of small numbers of 29 species of 
marine mammals incidental to conducting, with

[[Page 71607]]

research funding from the National Science Foundation (NSF), a marine 
seismic survey within the Exclusive Economic Zone (EEZ) of Tonga in the 
southwest Pacific Ocean during January through February 2009.
    L-DEO proposes to tomographically image the crust and uppermost 
mantle of the Eastern Lau Spreading Center (ELSC). The survey area is 
approximately 42 kilometers (km) offshore from Tonga in water depths 
ranging from 1000 - 2600 meters (m). L-DEO chose to survey the ELSC 
because it provides the best site to study the complete range of 
spreading center processes, magma storage and thermal systems. This 
study is part of NSF's RIDGE 2000 program, which was developed to 
facilitate the study of mid-ocean ridges and back-arc spreading 
centers. These areas mark the boundaries where oceanic plates separate 
from one another. Around the mid-ocean ridges, heat from the mantle 
drives vast hydrothermal systems that influence ocean water chemistry 
and nourish enormous ecosystems. These data are integral to 
understanding how mid-ocean ridges influence global climatic conditions 
and to understanding plate tectonic processes and their effects on 
earthquake occurrence and distribution.

Description of the Specified Activity

    The planned survey will involve one source vessel, the R/V Marcus 
G. Langseth (Langseth), a seismic vessel owned by the NSF. The proposed 
project is scheduled to commence on January 14, 2009, and end on 
February 21, 2009. The vessel will depart Nuku'alofa, Tonga on January 
14, 2009 for a one-day transit to the study area in the Lau Basin in 
the southwest Pacific Ocean (between 19-21[deg] S. and 175-176[deg] 
W.).
    To obtain high-resolution three-dimensional (3D) structures of the 
Lau Basin's magmatic systems and thermal structures, the Langseth will 
deploy a towed array of 36 airguns with a total discharge volume of 
approximately 6,600 cubic inches (in\3\). The Langseth will also deploy 
55 to 64 Ocean Bottom Seismometers (OBS) for the survey. As the airgun 
array is towed along the survey lines, the OBS will receive the 
returning acoustic signals and record them internally for later 
analysis. In addition to the OBS, L-DEO may use a relatively short (up 
to 6-km) hydrophone streamer to receive the returning acoustic signals 
and transfer the data to the on-board processing system.
    The seismic survey effort (e.g., equipment testing, startup, line 
changes, repeat coverage of any areas, and equipment recovery) will 
require approximately 19 days to complete 42 transects of variable 
lengths, totaling 3650 km and will include approximately 456 hours of 
airgun operation. Please see L-DEO's application for more detailed 
information. The proposed seismic transects will provide a 
tomographical image in three dimensions of the physical properties of 
the crust and uppermost mantle of this area. The exact dates of the 
activities will depend on logistics, weather conditions, and the need 
to repeat some lines if data quality is substandard.

Vessel Specifications

    The Langseth, operated by L-DEO, was designed as a seismic research 
vessel, with a propulsion system designed to be as quiet as possible to 
avoid interference with the seismic signals. The vessel, which has a 
length of 71.5 m (235 feet (ft); a beam of 17.0 m (56 ft); a maximum 
draft of 5.9 m (19 ft); and a gross tonnage of 2925, can accommodate up 
to 55 people. The ship is powered by two Bergen BRG-6 diesel engines, 
each producing 3550 horsepower (hp), which drive the two propellers 
directly. Each propeller has four blades, and the shaft typically 
rotates at 750 revolutions per minute. The vessel also has an 800 hp 
bowthruster, which is not used during seismic acquisition. The 
operation speed during seismic acquisition is typically 7.4B9.3 km/h 
(4-5 knots). When not towing seismic survey gear, the Langseth can 
cruise at 20B24 km/h (11-13 knots). The Langseth has a range of 25,000 
km (13,499 nautical miles). The Langseth will also serve as the 
platform from which vessel-based marine mammal (and sea turtle) 
observers will watch for animals before and during airgun operations.

Acoustic Source Specifications

Seismic Airguns
    The full airgun array for the survey consists of 36 airguns (a 
mixture of Bolt 1500LL and Bolt 1900LLX airguns ranging in size from 40 
to 360 in\3\), with a total volume of approximately 6,600 in\3\ and a 
firing pressure of 1900 pounds per square inch (psi). The airgun array 
will fire every 400 m or 180 seconds. The dominant frequency component 
is 2-188 Hertz (Hz).
    The array configuration consists of four identical linear arrays or 
strings, with 10 airguns on each string; the first and last airguns 
will be spaced 16 m (52 ft) apart. For each operating string, nine 
airguns will be fired simultaneously, whereas the tenth is kept in 
reserve as a spare, to be turned on in case of failure of another 
airgun. The four airgun strings will be distributed across an 
approximate area of 24H16 m (79 x 52 ft) behind the Langseth and will 
be towed approximately 50-100 m (164-328 ft) behind the vessel at a 
tow-depth of 9-12 m (29.5-39.4 ft). The airgun array will fire for a 
brief (0.1 second (s)) pulse every 180 s. The array will remain silent 
at all other times.
Multibeam Echosounder
    The Langseth will operate a Simrad EM120 multibeam echosounder 
(MBES) simultaneously during airgun operations to map characteristics 
of the ocean floor. The hull-mounted MBES emits brief pulses of mid- or 
high-frequency (11.25-12.6 kHz) sound in a fanshaped beam that extends 
downward and to the sides of the ship. The beamwidth is 1[deg] fore-aft 
and 150[deg] athwartship. The maximum source level is 242 dB re 1 
microPam (root mean square (rms)). For deep-water operation, 
each ``ping'' consists of nine successive fan-shaped transmissions, 
each 15 millisecond (ms) in duration and each ensonifying a sector that 
extends 1[deg] foreBaft. The nine successive transmissions span an 
overall cross-track angular extent of about 150[deg], with 16 ms gaps 
between the pulses for successive sectors. A receiver in the overlap 
area between two sectors would receive two 15-ms pulses separated by a 
16-ms gap. In shallower water, the pulse duration is reduced to 5 or 2 
ms, and the number of transmit beams is also reduced. The ping interval 
varies with water depth, from approximately 5 s at 1000 m (3,281 ft) to 
20 s at 4000 m (13,124 ft).
Sub-bottom Profiler
    The Langseth will operate a sub-bottom profiler (SBP) continuously 
throughout the cruise with the MBES. An SBP operates at mid- to high 
frequencies and is generally used simultaneously with an MBES to 
provide information about the sedimentary features and bottom 
topography. SBP pulses are directed downward at typical frequencies of 
approximately 3 18 kHz. However, the dominant frequency component of 
the SBP is 3.5 kHz which is directed downward in a narrow beam by a 
hull-mounted transducer on the vessel. The SBP output varies with water 
depth from 50 watts in shallow water to 800 watts in deep water and has 
a normal source output (downward) of 200 dB re 1 microPa m and a 
maximum source level output (downward) of 204 dB re 1 microPa  
m.

[[Page 71608]]

    The SBP used aboard the Langseth uses seven beams simultaneously, 
with a beam spacing of up to 15 degrees ([deg]) and a fan width up to 
30[deg]. Pulse duration is 0.4 100 ms at intervals of 1 s; a common 
mode of operation is to broadcast five pulses at 1-s intervals followed 
by a 5-s pause.

Characteristics of Airgun Pulses

    Discussion of the characteristics of airgun pulses has been 
provided in Appendix B of L-DEO=s application and in previous Federal 
Register notices (see 69 FR 31792, June 7, 2004; 71 FR 58790, October 
5, 2006; 72 FR 71625, December 18, 2007; or 73 FR 52950, September 12, 
2008). Reviewers are referred to those documents for additional 
information.

Safety Radii

    To aid in estimating the number of marine mammals that are likely 
to be taken, pursuant to the MMPA, and in developing effective 
mitigation measures, NMFS applies certain acoustic thresholds that 
indicate the received level at which Level A or Level B harassment 
would occur in marine mammals were exposed, see Table 1.

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                                                                      Predicted RMS Distances (m)
        Source and Volume            Tow Depth (m)   -----------------------------------------------------------
                                                            190 dB              180 dB              160 dB
----------------------------------------------------------------------------------------------------------------
Single Bolt airgun 40 in\3\       9-12                12                  40                  385
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4 strings 36 airguns 6600 in\3\   9                   300                 950                 6000
                                 -------------------------------------------------------------------------------
                                  12                  340                 1120                6850
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Table 1. Predicted distances to which sound levels [gteqt] 190, 180, and 160 dB re 1 micro Pa might be received
  in deep (>1000 m; 3280 ft) water from the 36 airgun array during the seismic survey, January - February, 2009.

    The distance from the sound source at which an animal would be 
exposed to these different received sound levels may be estimated and 
is typically referred to as safety radii. These safety radii are 
specifically used to help NMFS estimate the number of marine mammals 
likely to be harassed by the proposed activity and in deciding how 
close a marine mammal may approach an operating sound source before the 
applicant will be required to power-down or shut down the sound source.
    During this study, all survey efforts will take place in deep 
(greater than 1000 m, 3820 ft) water. The L-DEO model does not allow 
for bottom interactions, and thus is most directly applicable to deep 
water and to relatively short ranges. L-DEO has summarized the modeled 
distances for the planned airgun configuration in Table 1 which shows 
the distances at which four rms sound levels (190 decibel (dB), 180 dB, 
and 160 dB) are expected to be received from the 36-airgun array and a 
single airgun operating in water greater than 1000 m (3,820 ft) in 
depth.
    The calculated distances are expected to overestimate the actual 
distances to the corresponding Sound Pressure Levels (SPL), given the 
deep-water results of Tolstoy et al. (2004a,b). Additional information 
regarding how the safety radii were calculated and how the empirical 
measurements were used to correct the modeled numbers may be found in 
Section I and Appendix A of L-DEO's application.
    The conclusion that the model predictions in Table 1 are 
precautionary, relative to actual 180 and 190 dB (rms) radii, is based 
on empirical data from the acoustic calibration of different airgun 
configurations than those used on the Langseth (cf. Tolstoy et al., 
2004a,b); that sound source verification study was done in the northern 
Gulf of Mexico. L-DEO has recently (late 2007/early 2008) conducted a 
more extensive acoustic calibration study of the Langseth's 36-airgun 
array, also in the northern Gulf of Mexico (LGL Ltd. 2006; Holst and 
Beland, 2008). Distances where various sound levels (e.g., 190, 180, 
and 160 dB re 1 microPa (rms) were received are being determined for 
various airgun configurations and water depths. Those results are not 
yet available. However, the empirical data from the 2007/2008 
calibration study will be used to refine the exclusion zones proposed 
above for use during survey, if the data are appropriate and available 
at the time of the survey.

Description of Marine Mammals in the Activity Area

    Twenty-nine marine mammal species may occur off the coast of Tonga, 
including 21 odontocetes (toothed cetaceans, such as dolphins), and 8 
mysticetes (baleen whales). Pinnipeds are unlikely to be encountered in 
or near the Lau Basin survey area where seismic operations will occur, 
and are, therefore, not addressed further in this document. Five of 
these species are listed as endangered under the U.S. Endangered 
Species Act (ESA), including the humpback (Megaptera novaeangelae), sei 
(Balaenoptera borealis), fin (Balenoptera physalus), blue (Balenoptera 
musculus), and sperm (Physeter macrocephalus) whales. This IHA will 
only address requested take authorizations for cetaceans as L-DEO does 
not expect to encounter pinnipeds that far offshore in the study area. 
Thus L-DEO is not requesting any takes for pinnipeds in this IHA.
    Table 2 below outlines the species, their habitat and abundance in 
the proposed survey area, and the requested number of takes by both 
instances and individuals.

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                                                                                                              Maximum Estimate of                         Best Estimate of
                                                                Abundance in the SW      Occurrence in the        Individuals        Best Estimate of        Exposures           Approx. % of
             Species                        Habitat                   Pacific               Survey Area      ---------------------     Individuals     --------------------- Regional Population
                                                                                                                    Request                                  Instances
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Mysticetes
---------------------------------
Humpback whale*                   Nearshore waters            6,200                   Rare                    3                    1                    3                    0.01
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Sei whale*                        Offshore, pelagic           12,000                  Common                  3                    1                    3                    0.01
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[[Page 71609]]

 
Fin whale*                        Pelagic, continental slope  3,031                   Uncommon                3                    1                    3                    0.03
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Blue whale*                       Pelagic, coastal            756                     Uncommon                3                    1                    3                    0.12
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Pygmy right whale                 Coastal, oceanic            0                       Common                  3                    1                    3                    N.A.
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Minke whale                       Pelagic, coastal            155,000                 Rare in Jan.            3                    1                    3                    0.001
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Dwarf minke whale                 Coastal                     N.A.                    N.A.                    3                    1                    3                    N.A.
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Bryde's whale                     Pelagic, coastal            16,500                  Common                  14                   4                    15                   0.02
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Odontocetes
---------------------------------
Sperm whale*                      Pelagic, deep seas          22,700                  Common                  22                   6                    22                   0.03
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Pygmy sperm whale                 Deep waters off the shelf   N.A.                    Common                  353                  96                   358                  N.A.
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Dwarf Sperm whale                 Deep waters off the shelf   11,200                  Uncommon                353                  96                   358                  0.85
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Cuvier's beaked whale             Pelagic                     20,000                  Common                  40                   17                   64                   0.09
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Southern bottlenose whale         Pelagic                     N.A.                    Rare                    0                    0                    0                    N.A.
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Longman's beaked whale            Pelagic                     N.A.                    Uncommon                16                   7                    26                   N.A.
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Blainville's beaked whale         Pelagic                     25,300                  Common                  40                   17                   64                   0.07
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Ginkgo-toothed beaked whale       Pelagic                     25,300                  Rare                    16                   7                    26                   0.03
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Rough-toothed dolphin             Deep water                  145,900                 Uncommon                1,649                857                  3,214                0.59
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Bottlenose dolphin                Coastal, oceanic            243,500                 Common                  330                  171                  643                  0.07
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Pantropical spotted dolphin       Coastal, pelagic            1,298,400               Uncommon                1,649                857                  3,214                0.07
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Spinner dolphin                   Coastal, pelagic            1,019,300               Rare                    3,298                1,714                6,428                0.17
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Striped dolphin                   Continental shelf           1,918,000               Rare                    330                  171                  643                  0.01
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Fraser's dolphin                  Waters > 1000 m             289,300                 Rare                    989                  514                  1,929                0.18
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Short-beaked common dolphin       Shelf, pelagic              2,210,900               Common                  330                  171                  643                  0.01
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Risso's dolphin                   Waters > 1000 m             175,800                 Common                  330                  171                  643                  0.10
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Melon-headed whale                Oceanic                     45,400                  Uncommon                152                  43                   163                  0.10
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Pygmy killer whale                Deep, pantropical           38,900                  Uncommon                30                   9                    33                   0.02
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False killer whale                Pelagic                     39,800                  Uncommon                91                   26                   98                   0.07
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Killer whale                      Widely distributed          8,500                   Common                  61                   17                   65                   0.20
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Short-finned pilot whale          Pelagic                     160,200                 Common                  61                   17                   65                   0.01
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[[Page 71610]]

 
Total                                                                                                         10,173               4,997                18,735               ...................
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Table 2. Abundance, preferred habitat, and commonness of the marine mammal species that may be encountered during the proposed survey within the Lau Basin survey area. The far right columns
  indicate the estimated number of each species that will be exposed to 160 dB based on best and maximum density estimates. NMFS believes that, when mitigation measures are taken into
  consideration, the activity is likely to result in take of numbers of animals less than those indicated by the column titled Maximum Estimate of Exposures - Request.
* Federally listed endangered species.

    Detailed information regarding the status and distribution of these 
marine mammals may be found in sections III and IV of L-DEO's 
application.

Potential Effects of the Proposed Activity on Marine Mammals

Summary of Potential Effects of Airgun Sounds on Marine Mammals

    The effects of sounds from airguns might include one or more of the 
following: tolerance, masking of natural sounds, behavioral 
disturbance, temporary or permanent hearing impairment, or non-auditory 
physical or physiological effects (Richardson et al., 1995; Gordon et 
al., 2004; Nowacek et al., 2007; Southall et al., 2007). Permanent 
hearing impairment, in the unlikely event that it occurred, would 
constitute injury, but temporary threshold shift (TTS) is not an injury 
(Southall et al., 2007). Although the possibility cannot be entirely 
excluded, it is unlikely that the project would result in any cases of 
temporary or permanent hearing impairment, or any significant non-
auditory physical or physiological effects. Some behavioral disturbance 
is expected, but is expected to be localized and short-term. These 
effects are discussed below, but also in further detail in Appendix B 
of L-DEO=s application.

Tolerance

    Numerous studies have shown that pulsed sounds from airguns are 
often readily detectable in the water at distances of many kilometers. 
A summary of the characteristics of airgun pulses, is provided in 
Appendix B of L-DEO's application. Several studies have also shown that 
marine mammals at distances more than a few kilometers from operating 
seismic vessels often show no apparent response (tolerance) (see 
Appendix B of L-DEO's application ). That is often true even in cases 
when the pulsed sounds must be readily audible to the animals based on 
measured received levels and the hearing sensitivity of that mammal 
group. Although various baleen whales, toothed whales, and (less 
frequently) pinnipeds have been shown to react behaviorally to airgun 
pulses under some conditions, at other times mammals of all three types 
have shown no overt reactions. In general, pinnipeds usually seem to be 
more tolerant of exposure to airgun pulses than cetaceans, with the 
relative responsiveness of baleen and toothed whales being variable.

Masking

    Introduced underwater sound may, through masking, reduce the 
effective communication distance of a marine mammal species if the 
frequency of the source is close to that used as a signal by the marine 
mammal, and if the anthropogenic sound is present for a significant 
fraction of the time (Richardson et al., 1995).
    Masking effects of pulsed sounds (even from large arrays of 
airguns) on marine mammal calls and other natural sounds are expected 
to be limited, although there are very few specific data on this. 
Because of the intermittent nature (one pulse every 180 seconds) and 
low duty cycle of seismic pulses, animals can emit and receive sounds 
in the relatively quiet intervals between pulses. However, in 
exceptional situations, reverberation occurs for much or 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). In the 
northeastern Pacific Ocean, blue whale calls have been recorded during 
a seismic survey off Oregon (McDonald et al., 1995). Among odontocetes, 
there has been one report that sperm whales ceased calling when exposed 
to pulses from a very distant seismic ship (Bowles et al., 1994), but 
more recent studies found that they continued calling in the presence 
of seismic pulses (Madsen et al., 2002c; Tyack et al., 2003; Smultea et 
al., 2004; Holst et al., 2006; Jochens et al., 2006). Dolphins and 
porpoises commonly are heard calling while airguns are operating (e.g., 
Gordon et al., 2004; Smultea et al., 2004; Holst et al., 2005a,b; 
Potter et al., 2007). The sounds important to small odontocetes are 
predominantly at much higher frequencies than are the dominant 
components of airgun sounds, thus limiting the potential for masking. 
In general, masking effects of seismic pulses are expected to be minor, 
given the normally intermittent nature of seismic pulses and the 
Langseth being the only seismic vessel operating in the area for a 
limited time. Masking effects on marine mammals are discussed further 
in Appendix B of L-DEO's application.

Disturbance Reactions

    Disturbance includes a variety of effects, including subtle to 
conspicuous changes in behavior, movement, and displacement. Based on 
NMFS (2001, p. 9293), NRC (2005), and Southall et al. (2007), we assume 
that simple exposure to sound, or brief reactions that do not disrupt 
behavioral patterns in a potentially significant manner, do not 
constitute harassment or ``taking''. By potentially significant, we 
mean ``in a manner that might have deleterious effects to the well-
being of individual marine mammals or their populations''.
    Reactions to sound, if any, depend on species, state of maturity, 
experience, current activity, reproductive state, time of day, and many 
other factors (Richardson et al., 1995; Wartzok et al., 2004; Southall 
et al., 2007). If a marine mammal does react briefly to an underwater 
sound by changing its behavior or moving a small distance, the impacts 
of the change are unlikely to be significant to the individual, let 
al.ne the stock or population. However, if a sound source displaces 
marine mammals from an important feeding or breeding area for a 
prolonged period, impacts on individuals and populations could be 
significant. Given the many uncertainties in predicting the quantity 
and types of impacts of noise on marine mammals, it is common practice 
to estimate how many mammals would be present within a particular 
distance of

[[Page 71611]]

industrial activities and exposed to a particular level of industrial 
sound. In most cases, this approach likely overestimates the numbers of 
marine mammals that would be affected in some biologically-important 
manner.
    The sound criteria used to estimate how many marine mammals might 
be disturbed to some biologically-important degree by a seismic program 
are based primarily on behavioral observations of a few species. 
Detailed studies have been done on humpback 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. Whales are often reported to show 
no overt reactions to pulses from large arrays of airguns at distances 
beyond a few kilometers, even though the airgun pulses remain well 
above ambient noise levels out to much longer distances. However, as 
reviewed in Appendix B of L-DEO's application, baleen whales exposed to 
strong noise pulses from airguns often react by deviating from their 
normal migration route and/or interrupting their feeding and moving 
away. In the cases of migrating gray and bowhead whales, the observed 
changes in behavior appeared to be of little or no biological 
consequence to the animals. They simply avoided the sound source by 
displacing their migration route to varying degrees, but within the 
natural boundaries of the migration corridors.
    Studies of gray (Eshrichtius robustus), bowhead (Balena 
mysticetes), and humpback whales have shown that seismic pulses with 
received levels of 160 170 dB re 1 microPa (rms) seem to cause obvious 
avoidance behavior in a substantial fraction of the animals exposed 
(Richardson et al., 1995). In many areas, seismic pulses from large 
arrays of airguns diminish to those levels at distances ranging from 4 
15 km (2.5-9.3 mi) from the source. A substantial proportion of the 
baleen whales within those distances may show avoidance or other strong 
behavioral reactions to the airgun array. Subtle behavioral changes 
sometimes become evident at somewhat lower received levels, and studies 
summarized in Appendix B of L-DEO's application have shown that some 
species of baleen whales, notably bowhead and humpback whales, at times 
show strong avoidance at received levels lower than 160 170 dB re 1 
microPa (rms).
    Responses of humpback whales to seismic surveys have been studied 
during migration, on summer feeding grounds, and on Angolan winter 
breeding grounds; there has also been discussion of effects on the 
Brazilian wintering grounds. McCauley et al. (1998, 2000a) studied the 
responses of humpback whales off Western Australia to a full-scale 
seismic survey with a 16-airgun, 2678-in\3\ array, and to a single 20-
in\3\ airgun with source level 227 dB re 1 microPa m (peak to peak). 
McCauley et al. (1998) documented that avoidance reactions began at 5-8 
km (3-5 mi) from the array, and that those reactions kept most pods 
approximately 3-4 km (1.8-2.5 mi) from the operating seismic boat. 
McCauley et al. (2000a) noted localized displacement during migration 
of 4-5 km (2.5-3.1 mi) by traveling pods and 7-12 km (4.3-7.5 mi) by 
more sensitive resting pods of cow-calf pairs. Avoidance distances with 
respect to the single airgun were smaller but consistent with the 
results from the full array in terms of the received sound levels. The 
mean received level for initial avoidance of an approaching airgun was 
140 dB re 1 microPa (rms) for humpback pods containing females, and at 
the mean closest point of approach distance the received level was 143 
dB re 1 microPa (rms). The initial avoidance response generally 
occurred at distances of 5-8 km (3.1-4.9 mi) from the airgun array and 
2 km (1.2 mi) from the single airgun. However, some individual humpback 
whales, especially males, approached within distances of 100-400 m 
(328-1312 ft), where the maximum received level was 179 dB re 1 microPa 
(rms).
    Humpback whales on their summer feeding grounds in southeast Alaska 
did not exhibit persistent avoidance when exposed to seismic pulses 
from a 1.64-L (100-in\3\) airgun (Malme et al., 1985). Malme et al. 
reported that some of the humpbacks seemed startled at received levels 
of 150 169 dB re 1 FPa and concluded that there was no clear evidence 
of avoidance, despite the possibility of subtle effects, at received 
levels up to 172 re 1 microPa on an approximate rms basis. It has been 
suggested that South Atlantic humpback whales wintering off Brazil may 
be displaced or even strand upon exposure to seismic surveys (Engel et 
al., 2004). The evidence for this was circumstantial and subject to 
alternative explanations (IAGC, 2004). Also, the evidence was not 
consistent with subsequent results from the same area of Brazil 
(Parente et al., 2006), or with direct studies of humpbacks exposed to 
seismic surveys in other areas and seasons. After allowance for data 
from subsequent years, there was ``no observable direct correlation'' 
between strandings and seismic surveys (IWC, 2007:236).
    Various species of Balaenoptera (blue, sei, fin, and minke whales) 
have occasionally been reported in areas ensonified by airgun pulses 
(Stone, 2003; MacLean and Haley, 2004; Stone and Tasker, 2006). 
Sightings by observers on seismic vessels off the United Kingdom from 
1997 to 2000 suggest that, during times of good sightability, sighting 
rates for mysticetes (mainly fin and sei whales) were similar when 
large arrays of airguns were shooting vs. silent (Stone, 2003; Stone 
and Tasker, 2006). However, these whales tended to exhibit localized 
avoidance, remaining significantly further (on average) from the airgun 
array during seismic operations compared with non-seismic periods 
(Stone and Tasker, 2006). In a study off Nova Scotia, Moulton and 
Miller (2005) found little difference in sighting rates (after 
accounting for water depth) and initial sighting distances of 
balaenopterid whales when airguns were operating versus silent. 
However, there were indications that these whales were more likely to 
be moving away when seen during airgun operations. Similarly, ship-
based monitoring studies of blue, fin, sei and minke whales offshore of 
Newfoundland (Orphan Basin and Laurentian Sub-basin) found no more than 
small differences in sighting rates and swim directions during seismic 
vs. non-seismic periods Moulton et al., 2005, 2006a,b).
    Data on short-term reactions by cetaceans to impulsive noises are 
not necessarily indicative of long-term or biologically significant 
effects. It is not known whether impulsive sounds affect reproductive 
rate or distribution and habitat use in subsequent days or years. 
However, gray whales have continued to migrate annually along the west 
coast of North America with substantial increases in the population 
over recent years, despite intermittent seismic exploration (and much 
ship traffic) in that area for decades (Appendix A in Malme et al., 
1984; Richardson et al., 1995; Angliss and Outlaw, 2008). The western 
Pacific gray whale population did not seem affected by a seismic survey 
in its feeding ground during a previous year (Johnson et al., 2007). 
Similarly, bowhead whales have continued to travel to the eastern 
Beaufort Sea each summer, and their numbers have increased notably, 
despite seismic exploration in their summer and autumn range for many

[[Page 71612]]

years (Richardson et al., 1987; Angliss and Outlaw, 2008).
Toothed Whales
    Little systematic information is available about reactions of 
toothed whales to noise pulses. Few studies similar to the more 
extensive baleen whale/seismic pulse work summarized above and (in more 
detail) in Appendix B of L-DEO's application have been reported for 
toothed whales. However, there are recent systematic studies on sperm 
whales (Jochens et al., 2006; Miller et al., 2006), and there is an 
increasing amount of information about responses of various odontocetes 
to seismic surveys based on monitoring studies (e.g., Stone, 2003; 
Smultea et al., 2004; Moulton and Miller, 2005; Bain and Williams, 
2006; Holst et al., 2006; Stone and Tasker, 2006; Potter et al., 2007; 
Weir, 2008).
    Seismic operators and marine mammal observers on seismic vessels 
regularly see dolphins and other small toothed whales near operating 
airgun arrays, but in general there is a tendency for most delphinids 
to show some avoidance of operating seismic vessels (e.g., Goold, 
1996a,b,c; Calambokidis and Osmek, 1998; Stone, 2003; Moulton and 
Miller, 2005; Holst et al., 2006; Stone and Tasker, 2006; Weir, 2008). 
Some dolphins seem to be attracted to the seismic vessel and floats, 
and some ride the bow wave of the seismic vessel even when large arrays 
of airguns are firing (e.g., Moulton and Miller, 2005). Nonetheless, 
small toothed whales more often tend to head away, or to maintain a 
somewhat greater distance from the vessel, when a large array of 
airguns is operating than when it is silent (e.g., Stone and Tasker, 
2006; Weir, 2008). In most cases the avoidance radii for delphinids 
appear to be small, on the order of 1 km less, and some individuals 
show no apparent avoidance. The beluga (Delphinapterus leucas) is a 
species that (at 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 20 km (6.2-12.4 mi) compared with 
20 30 km (12.4-18.6 mi) from an operating airgun array, and observers 
on seismic boats in that area rarely see belugas (Miller et al., 2005; 
Harris et al., 2007).
    Captive bottlenose dolphins (Tursiops truncates) and beluga whales 
exhibited changes in behavior when exposed to strong pulsed sounds 
similar in duration to those typically used in seismic surveys 
(Finneran et al., 2000, 2002, 2005). However, the animals tolerated 
high received levels of sound before exhibiting aversive behaviors.
    Results for porpoises depend on species. The limited available data 
suggest that harbor porpoises (Phocoena phocoena) show stronger 
avoidance of seismic operations than do Dall's porpoises (Phocoenoides 
dalli) (Stone, 2003; MacLean and Koski, 2005; Bain and Williams, 2006; 
Stone and Tasker, 2006). Dall's porpoises seem relatively tolerant of 
airgun operations (MacLean and Koski, 2005; Bain and Williams, 2006), 
although they too have been observed to avoid large arrays of operating 
airguns (Calambokidis and Osmek, 1998; Bain and Williams, 2006). This 
apparent difference in responsiveness of these two porpoise species is 
consistent with their relative responsiveness to boat traffic and some 
other acoustic sources (Richardson et al., 1995; Southall et al., 
2007).
    Most studies of sperm whales exposed to airgun sounds indicate that 
the sperm whale shows considerable tolerance of airgun pulses (e.g., 
Stone, 2003; Moulton et al., 2005, 2006a; Stone and Tasker, 2006; Weir, 
2008). In most cases the whales do not show strong avoidance, and they 
continue to call (see Appendix B of L-DEO's application for review). 
However, controlled exposure experiments in the Gulf of Mexico indicate 
that foraging behavior was altered upon exposure to airgun sound 
(Jochens et al., 2006).
    There are almost no specific data on the behavioral reactions of 
beaked whales to seismic surveys. However, northern bottlenose whales 
(Hyperoodon ampullatus) continued to produce high-frequency clicks when 
exposed to sound pulses from distant seismic surveys (Laurinolli and 
Cochrane, 2005; Simard et al., 2005). Most beaked whales tend to avoid 
approaching vessels of other types (e.g., Wursig et al., 1998). They 
may also dive for an extended period when approached by a vessel (e.g., 
Kasuya, 1986). Thus, it is likely that beaked whales would also show 
strong avoidance of an approaching seismic vessel, although this has 
not been documented explicitly.
    There are increasing indications that some beaked whales tend to 
strand when naval exercises involving mid-frequency sonar operation are 
ongoing nearby (e.g., Simmonds and Lopez-Jurado, 1991; Frantzis, 1998; 
NOAA and USN, 2001; Jepson et al., 2003; Hildebrand, 2005; Barlow and 
Gisiner, 2006; see also the ``Strandings and Mortality'' subsection, 
later). These strandings are apparently at least in part a disturbance 
response, although auditory or other injuries or other physiological 
effects may also be involved. Whether beaked whales would ever react 
similarly to seismic surveys is unknown (see ``Strandings and 
Mortality'', below). Seismic survey sounds are quite different from 
those of the sonar in operation during the above-cited incidents.
    Odontocete reactions to large arrays of airguns are variable and, 
at least for delphinids and Dall's porpoises, seem to be confined to a 
smaller radius than has been observed for the more responsive of the 
mysticetes, belugas, and harbor porpoises (refer to Appendix B in L-
DEO's application).

Hearing Impairment and Other Physical Effects

    Temporary or permanent hearing impairment is a possibility when 
marine mammals are exposed to very strong sounds, and temporary 
threshold shift (TTS) has been demonstrated and studied in certain 
captive odontocetes and pinnipeds exposed to strong sounds (reviewed in 
Southall et al., 2007). However, there has been no specific 
documentation of TTS let al.ne permanent hearing damage, i.e., 
permanent threshold shift (PTS), in free-ranging marine mammals exposed 
to sequences of airgun pulses during realistic field conditions. To 
avoid the potential for injury, NMFS has determined that cetaceans and 
pinnipeds should not be exposed to pulsed underwater noise at received 
levels exceeding, respectively, 180 and 190 dB re 1 
microParms. As summarized above, data that are now available 
imply that TTS is unlikely to occur unless odontocetes (and probably 
mysticetes as well) are exposed to airgun pulses stronger than 180 dB 
re 1 microPa (rms).
    Several aspects of the planned monitoring and mitigation measures 
for this project are designed to detect marine mammals occurring near 
the airgun array, and to avoid exposing them to sound pulses that 
might, at least in theory, cause hearing impairment. In addition, many 
cetaceans and (to a limited degree) pinnipeds and sea turtles are 
likely to show some avoidance or the area with high received levels of 
airgun sound. In those cases, the avoidance responses of the animals 
themselves will reduce or (most likely) avoid any possibility of 
hearing impairment.
    Non-auditory physical effects might also occur in marine mammals 
exposed to strong underwater pulsed sound. Possible types of non-
auditory physiological effects or injuries that might (in theory) occur 
in mammals close to a strong sound source include stress, neurological 
effects, bubble

[[Page 71613]]

formation, and other types of organ or tissue damage. It is possible 
that some marine mammal species (i.e., beaked whales) may be especially 
susceptible to injury and/or stranding when exposed to strong pulsed 
sounds. However, as discussed below, there is no definitive evidence 
that any of these effects occur even for marine mammals in close 
proximity to large arrays of airguns. It is unlikely that any effects 
of these types would occur during the proposed project given the brief 
duration of exposure of any given mammal, the deep water in the survey 
area, and the planned monitoring and mitigation measures (see below). 
The following subsections discuss in somewhat more detail the 
possibilities of TTS, PTS, and non-auditory physical effects.
Temporary Threshold Shift (TTS)
    TTS is the mildest form of hearing impairment that can occur during 
exposure to a strong sound (Kryter, 1985). While experiencing TTS, the 
hearing threshold rises and a sound must be stronger in order to be 
heard. At least in terrestrial mammals, TTS can last from minutes or 
hours to (in cases of strong TTS) days. For sound exposures at or 
somewhat above the TTS threshold, hearing sensitivity in both 
terrestrial and marine mammals recovers rapidly after exposure to the 
noise ends. Few data on sound levels and durations necessary to elicit 
mild TTS have been obtained for marine mammals, and none of the 
published data concern TTS elicited by exposure to multiple pulses of 
sound. Available data on TTS in marine mammals are summarized in 
Southall et al. (2007).
    For toothed whales exposed to single short pulses, the TTS 
threshold appears to be, to a first approximation, a function of the 
energy content of the pulse (Finneran et al., 2002, 2005). Sound 
exposure level (SEL), which takes into account the duration of the 
sound, is the metric used to measure energy and uses the units dB re 1 
microPa\2\s, as opposed to SPL, which is the pressure metric 
used in the rest of this document (units - dB re 1 microPa). Given the 
available data, the received energy level of a single seismic pulse 
(with no frequency weighting) might need to be approximately 186 dB re 
1 microPa\2\s (i.e., 186 dB SEL or approximately 196 201 dB re 
1 microPa (rms)) in order to produce brief, mild TTS. Exposure to 
several strong seismic pulses that each have received levels near 190 
dB re 1 microPa (rms) might result in cumulative exposure of 
approximately 186 dB SEL and thus slight TTS in a small odontocete, 
assuming the TTS threshold is (to a first approximation) a function of 
the total received pulse energy. The distances from the Langseth's 
airguns at which the received energy level (per pulse, flat-weighted) 
would be expected to be 190 dB re 1 microPa (rms) or above, are shown 
in Table 1. Levels 190 dB re 1 microPa (rms) or above are expected to 
be restricted to radii no more than 340 m (1115.5 ft) (Table 1) from 
the 36-airgun array. For an odontocete closer to the surface, the 
maximum radius with 190 dB re 1 microPa (rms) or above, would be 
smaller.
    The above TTS information for odontocetes is derived from studies 
on the bottlenose dolphin and beluga. There is no published TTS 
information for other types of cetaceans. However, preliminary evidence 
from a harbor porpoise exposed to airgun sound suggests that its TTS 
threshold may have been lower (Lucke et al., 2007).
    For baleen whales, there are no data, direct or indirect, on levels 
or properties of sound that are required to induce TTS. The frequencies 
to which baleen whales are most sensitive are assumed to be lower than 
those to which odontocetes are most sensitive, and natural background 
noise levels at those low frequencies tend to be higher. As a result, 
auditory thresholds of baleen whales within their frequency band of 
best hearing are believed to be higher (less sensitive) than are those 
of odontocetes at their best frequencies (Clark and Ellison, 2004). 
From this, it is suspected that received levels causing TTS onset may 
also be higher in baleen whales (Southall et al., 2007). In any event, 
no cases of TTS are expected given three considerations: (1) the low 
abundance of baleen whales in most parts of the planned study area; (2) 
the strong likelihood that baleen whales would avoid the approaching 
airguns (or vessel) before being exposed to levels high enough for TTS 
to occur; and (3) the mitigation measures that are planned.
    In pinnipeds, TTS thresholds associated with exposure to brief 
pulses (single or multiple) of underwater sound have not been measured. 
Initial evidence from more prolonged (non-pulse) exposures suggested 
that some pinnipeds (harbor seals in particular) incur TTS at somewhat 
lower received levels than do small odontocetes exposed for similar 
durations (Kastak et al., 1999, 2005; Ketten et al., 2001). The TTS 
threshold for pulsed sounds has been indirectly estimated as being an 
SEL of approximately 171 dB re 1 microPa\2\s (Southall et al., 
2007), which would be equivalent to a single pulse with received level 
of approximately 181 186 dB re 1 FPa (rms), or a series of pulses for 
which the highest rms values are a few dB lower. However, pinnipeds are 
not expected to occur in or near the planned study area.
Permanent Threshold Shift (PTS)
    When PTS occurs, there is physical damage to the sound receptors in 
the ear. In severe cases, there can be total or partial deafness, while 
in other cases; the animal has an impaired ability to hear sounds in 
specific frequency ranges (Kryter, 1985). There is no specific evidence 
that exposure to pulses of airgun sound can cause PTS in any marine 
mammal, even with large arrays of airguns. However, given the 
possibility that mammals close to an airgun array might incur at least 
mild TTS, there has been further speculation about the possibility that 
some individuals occurring very close to airguns might incur PTS 
(Richardson et al., 1995, p. 372ff). Single or occasional occurrences 
of mild TTS are not indicative of permanent auditory damage. 
Relationships between TTS and PTS thresholds have not been studied in 
marine mammals, but are assumed to be similar to those in humans and 
other terrestrial mammals. PTS might occur at a received sound level at 
least several decibels above that inducing mild TTS if the animal were 
exposed to strong sound pulses with rapid rise time-see Appendix B of 
L-DEO's application. Based on data from terrestrial mammals, a 
precautionary assumption is that the PTS threshold for impulse sounds 
(such as airgun pulses as received close to the source) is at least 6 
dB higher than the TTS threshold on a peak-pressure basis, and probably 
greater than 6 dB (Southall et al., 2007). On an SEL basis, Southall et 
al. (2007:441-4) estimated that received levels would need to exceed 
the TTS threshold by at least 15 dB for there to be risk of PTS. Thus, 
for cetaceans they estimate that the PTS threshold might be a mammal-
weighted (M-weighted) SEL (for the sequence of received pulses) of 
approximately 198 dB re 1 microPa\2\s (15 dB higher than the 
TTS threshold for an impulse), where the SEL value is accumulated over 
the sequence of pulses. Additional assumptions had to be made to derive 
a corresponding estimate for pinnipeds, as the only available data on 
TTS-thresholds in pinnipeds pertain to non-impulse sound. Southall et 
al. (2007) estimate that the PTS threshold could be a cumulative 
Mpw-weighted SEL of approximately 186 dB re 1 
microPa2s in the harbor seal exposed to impulse sound. The PTS 
threshold for the California sea lion and northern elephant seal the 
PTS threshold would probably be higher, given the higher TTS thresholds 
in those species.

[[Page 71614]]

    Southall et al. (2007) also note that, regardless of the SEL, there 
is concern about the possibility of PTS if a cetacean or pinniped 
received one or more pulses with peak pressure exceeding 230 or 218 dB 
re 1 FPa (peak), respectively. A peak pressure of 230 dB re 1 microPa 
(3.2 barm, 0-peak) would only be found within a few meters of 
the largest (360 in\3\) airgun in the planned airgun array (Caldwell 
and Dragoset, 2000). A peak pressure of 218 dB re 1 microPa could be 
received somewhat farther away; to estimate that specific distance, one 
would need to apply a model that accurately calculates peak pressures 
in the nearfield around an array of airguns.
    Given the higher level of sound necessary to cause PTS as compared 
with TTS, it is considerably less likely that PTS would occur. Baleen 
whales generally avoid the immediate area around operating seismic 
vessels, as do some other marine mammals and sea turtles. The planned 
monitoring and mitigation measures, including visual monitoring, PAM, 
power downs, and shut downs of the airguns when mammals are seen within 
or approaching the exclusion zones, will further reduce the probability 
of exposure of marine mammals to sounds strong enough to induce PTS.
Non-auditory Physiological Effects
    Non-auditory physiological effects or injuries that theoretically 
might occur in marine mammals exposed to strong underwater sound 
include stress, neurological effects, bubble formation, resonance, and 
other types of organ or tissue damage (Cox et al., 2006; Southall et 
al., 2007). Studies examining such effects are limited. However, 
resonance (Gentry, 2002) and direct noise-induced bubble formation 
(Crum et al., 2005) are not expected in the case of an impulsive source 
like an airgun array. If seismic surveys disrupt diving patterns of 
deep-diving species, this might perhaps result in bubble formation and 
a form of the bends, as speculated to occur in beaked whales exposed to 
sonar. However, there is no specific evidence of this upon exposure to 
airgun pulses.
    In general, very little is known about the potential for seismic 
survey sounds (or other types of strong underwater sounds) to cause 
non-auditory physical effects in marine mammals. Such effects, if they 
occur at all, would presumably be limited to short distances and to 
activities that extend over a prolonged period. The available data do 
not allow identification of a specific exposure level above which non-
auditory effects can be expected (Southall et al., 2007), or any 
meaningful quantitative predictions of the numbers (if any) of marine 
mammals that might be affected in those ways. Marine mammals that show 
behavioral avoidance of seismic vessels, including most baleen whales, 
some odontocetes, and some pinnipeds, are especially unlikely to incur 
non-auditory physical effects. Also, the planned mitigation measures, 
including shut downs of the airguns, will reduce any such effects that 
might otherwise occur.

Strandings and Mortality

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

[[Page 71615]]

vessel before being exposed to high sound levels; (2) the proposed 
monitoring and mitigation measures; and (3) differences between the 
sound sources operated by L-DEO and those involved in the naval 
exercises associated with strandings.

Possible Effects of Multibeam Echosounder (MBES) Signals

    The Simrad EM120 12-kHz MBES will be operated from the source 
vessel continuously during the planned study. Sounds from the MBES are 
very short pulses, occurring for 2 15 ms once every 5 20 s, depending 
on water depth. Most of the energy in the sound pulses emitted by this 
MBES is at frequencies near 12 kHz, and the maximum source level is 242 
dB re 1 microPam (rms). The beam is narrow (1[deg]) in fore-aft 
extent and wide (150[deg]) in the cross-track extent. Each ping 
consists of nine successive fan-shaped transmissions (segments) at 
different cross-track angles. Any given mammal at depth near the 
trackline would be in the main beam for only one or two of the nine 
segments. Also, marine mammals that encounter the Simrad EM120 are 
unlikely to be subjected to repeated pulses because of the narrow fore 
aft width of the beam and will receive only limited amounts of pulse 
energy because of the short pulses. Animals close to the ship (where 
the beam is narrowest) are especially unlikely to be ensonified for 
more than one 2-15 ms pulse (or two pulses if in the overlap area). 
Similarly, Kremser et al. (2005) noted that the probability of a 
cetacean swimming through the area of exposure when an MBES emits a 
pulse is small. The animal would have to pass the transducer at close 
range and be swimming at speeds similar to the vessel in order to 
receive the multiple pulses that might result in sufficient exposure to 
cause TTS.
    Navy sonars that have been linked to avoidance reactions and 
stranding of cetaceans: (1) generally have longer pulse duration than 
the Simrad EM120, and (2) are often directed close to omnidirectionally 
versus more downward for the Simrad EM120. The area of possible 
influence of the MBES is much smaller a narrow band below the source 
vessel. The duration of exposure for a given marine mammal can be much 
longer for naval sonar.
    Marine mammal communications will not be masked appreciably by the 
MBES signals given the low duty cycle of the echosounder and the brief 
period when an individual mammal is likely to be within its beam. 
Furthermore, in the case of baleen whales, the MBES signals (12 kHz) do 
not overlap with the predominant frequencies in the calls, which would 
avoid any significant masking.
    Behavioral reactions of free-ranging marine mammals to sonar, 
echosounders, and other sound sources appear to vary by species and 
circumstance. Observed reactions have included silencing and dispersal 
by sperm whales (Watkins et al., 1985), increased vocalizations and no 
dispersal by pilot whales (Globicephala spp.) (Rendell and Gordon, 
1999), and the previously-mentioned beachings by beaked whales. During 
exposure to a 21 25 kHz sonar with a source level of 215 dB re 1 
microPam, gray whales reacted by orienting slightly away from 
the source and being deflected from their course by approximately 200 m 
(Frankel, 2005). When a 38-kHz echosounder and a 150-kHz acoustic 
Doppler current profiler were transmitting during studies in the 
Eastern Tropical Pacific, baleen whales showed no significant 
responses, while spotted and spinner dolphins were detected slightly 
more often and beaked whales less often during visual surveys 
(Gerrodette and Pettis, 2005).
    Captive bottlenose dolphins exhibited changes in behavior when 
exposed to 1-s tonal signals at frequencies similar to those that will 
be emitted by the MBES used by L-DEO, and to shorter broadband pulsed 
signals. Behavioral changes typically involved what appeared to be 
deliberate attempts to avoid the sound exposure (Schlundt et al., 2000; 
Finneran et al., 2002; Finneran and Schlundt, 2004). The relevance of 
those data to free-ranging odontocetes is uncertain, and in any case, 
the test sounds were quite different in duration as compared with those 
from an MBES.
    Because of the unlikelihood of an animal being exposed to more than 
one or two very brief pulses, NMFS does not expect the operation of the 
MBES to result in the harassment of any marine mammals.

Possible Effects of the Sub-bottom Profiler Signals

    An SBP may be operated from the source vessel at times during the 
planned study. Sounds from the sub-bottom profiler are very short 
pulses, occurring for 1 4 ms once every second. Most of the energy in 
the sound pulses emitted by the SBP is at 3.5 kHz, and the beam is 
directed downward in a narrow beam with a spacing of up to 15 and a fan 
width up to 30 . The sub-bottom profiler on the Langseth has a maximum 
source level of 204 dB re 1 microPam. Kremser et al. (2005) 
noted that the probability of a cetacean swimming through the area of 
exposure when a bottom profiler emits a pulse is small-even for an SBP 
more powerful than that on the Langseth if the animal was in the area, 
it would have to pass the transducer at close range and in order to be 
subjected to sound levels that could cause TTS.
    Marine mammal communications will not be masked appreciably by the 
sub-bottom profiler signals given their directionality and the brief 
period when an individual mammal is likely to be within its beam. 
Furthermore, in the case of most baleen whales, the SBP signals do not 
overlap with the predominant frequencies in the calls, which would 
avoid significant masking.
    Marine mammal behavioral reactions to other pulsed sound sources 
are discussed above, and responses to the SBP are likely to be similar 
to those for other pulsed sources if received at the same levels. 
However, the pulsed signals from the SBP are considerably weaker than 
those from the MBES. Therefore, behavioral responses would not be 
expected unless marine mammals were to approach very close to the 
source. This is not expected to occur because of the mitigation 
measures and the likely avoidance behaviors of marine mammals.
    It is unlikely that the SBP produces pulse levels strong enough to 
cause hearing impairment or other physical injuries even in an animal 
that is (briefly) in a position near the source. The SBP is usually 
operated simultaneously with other higher-power acoustic sources. Many 
marine mammals will move away in response to the approaching higher-
power sources or the vessel itself before the mammals would be close 
enough for there to be any possibility of effects from the less intense 
sounds from the SBP. In the case of mammals that do not avoid the 
approaching vessel and its various sound sources, mitigation measures 
that would be applied to minimize effects of other sources would 
further reduce or eliminate any minor effects of the SBP.

Possible Effects of the Acoustic Release Signals

    The acoustic release transponder used to communicate with the OBS 
uses frequencies of 9 13 kHz. Once the OBS is ready to be retrieved, an 
acoustic release transponder interrogates the OBS at a frequency of 9 
11 kHz, and a response is received at a frequency of 9 13 kHz. These 
signals will be used very intermittently. The source level of the 
release signal is 190 dB (re 1 microPa at 1 m). An animal would have to 
pass by the OBS at close range when the signal is emitted in order to 
be exposed to any

[[Page 71616]]

pulses at that level. The sound is expected to undergo a spreading loss 
of approximately 40 dB in the first 100 m (328 ft). Thus, any animals 
located 100 m (328 ft) or more from the signal will be exposed to very 
weak signals (less than 150 dB) that are not expected to have any 
effects. The signal is used only for short intervals to interrogate and 
trigger the release of the OBS and consists of pulses rather than a 
continuous sound. Given the short duration use of this signal and rapid 
attenuation in seawater it is unlikely that the acoustic release 
signals would significantly affect marine mammals or sea turtles 
through masking, disturbance, or hearing impairment. Any effects likely 
would be negligible given the brief exposure at presumable low levels.

Proposed Monitoring and Mitigation Measures

Monitoring

    L-DEO proposes to sponsor marine mammal monitoring during the 
present project, in order to implement the proposed mitigation measures 
that require real-time monitoring, and to satisfy the anticipated 
monitoring requirements of the IHA. L-DEO's proposed Monitoring Plan is 
described below this section. L-DEO understands that this monitoring 
plan will be subject to review by NMFS, and that refinements may be 
required. The monitoring work described here has been planned as a 
self-contained project independent of any other related monitoring 
projects that may be occurring simultaneously in the same regions. L-
DEO is prepared to discuss coordination of its monitoring program with 
any related work that might be done by other groups insofar as this is 
practical and desirable.
Vessel-based Visual Monitoring
    Marine mammal observers (MMOs) will be based aboard the seismic 
source vessel and will watch for marine mammals and turtles near the 
vessel during daytime airgun operations and during any start-ups at 
night. The MMOs will also watch for marine mammals and turtles near the 
seismic vessel for at least 30 minutes (min) prior to the start of 
airgun operations after an extended shut down. When feasible, MMOs will 
also observe during daytime periods when the seismic system is not 
operating for comparison of sighting rates and behavior with versus 
without airgun operations. Based on MMOs' observations, the airguns 
will be powered down or shut down when marine mammals are observed 
within or about to enter a designated exclusion zone (EZ). The EZ is a 
region in which a possibility exists of adverse effects on animal 
hearing or other physical effects.
    During seismic operations in the Lau Basin, at least three MMOs 
will be based aboard the Langseth. MMOs will be appointed by L-DEO with 
NMFS' concurrence. At least one MMO, and when practical two MMOs, will 
monitor marine mammals and turtles near the seismic vessel during 
ongoing daytime operations and nighttime start ups of the airguns. Use 
of two simultaneous observers will increase the proportion of the 
animals present near the source vessel that are detected. MMOs will be 
on duty in shifts of duration no longer than 4 hours (h). Other crew 
will also be instructed to assist in detecting marine mammals and 
turtles and implementing mitigation requirements (if practical). Before 
the start of the seismic survey the crew will be given additional 
instruction regarding how to do so.
    The Langseth is a suitable platform for marine mammal and turtle 
observations. When stationed on the observation platform, the eye level 
will be approximately 18 m (59 ft) above sea level, and the observer 
will have a good view around the entire vessel. During daytime, the 
MMOs will scan the area around the vessel systematically with reticle 
binoculars (e.g., 7 50 Fujinon), Big-eye binoculars (25 150), and with 
the naked eye. During darkness, night vision devices (NVDs) will be 
available (ITT F500 Series Generation 3 binocularimage intensifier or 
equivalent), when required. Laser rangefinding binoculars (Leica LRF 
1200 laser rangefinder or equivalent) will be available to assist with 
distance estimation. Those are useful in training observers to estimate 
distances visually, but are generally not useful in measuring distances 
to animals directly; that is done primarily with the reticles in the 
binoculars.
    The vessel-based monitoring will provide data to estimate the 
numbers of marine mammals exposed to various received sound levels, to 
document any apparent disturbance reactions or lack thereof, and thus 
to estimate the numbers of mammals potentially ``taken'' by harassment. 
It will also provide the information needed in order to power down or 
shut down the airguns at times when mammals and turtles are present in 
or near the safety radii. When a sighting is made, the following 
information about the sighting will be recorded:
    1. Species, group size, age/size/sex categories (if determinable), 
behavior when first sighted and after initial sighting, heading (if 
consistent), bearing and distance from seismic vessel, sighting cue, 
apparent reaction to the airguns or vessel (e.g., none, avoidance, 
approach, paralleling, etc.), and behavioral pace.
    2. Time, location, heading, speed, activity of the vessel, sea 
state, visibility, and sun glare.
    The data listed under (2) will also be recorded at the start and 
end of each observation watch, and during a watch whenever there is a 
change in one or more of the variables.
    All observations and power-downs or shut downs will be recorded in 
a standardized format. Data will be entered into a custom database 
using a notebook computer. The accuracy of the data entry will be 
verified by computerized validity data checks as the data are entered 
and by subsequent manual checking of the database. Preliminary reports 
will be prepared during the field program and summaries forwarded to 
the operating institution's shore facility and to NSF weekly or more 
frequently.
    Results from the vessel-based observations will provide:
    1. The basis for real-time mitigation (airgun power-down or shut-
down).
    2. Information needed to estimate the number of marine mammals 
potentially taken by harassment, which must be reported to NMFS per 
terms of MMPA authorizations or regulations.
    3. Data on the occurrence, distribution, and activities of marine 
mammals and turtles in the area where the seismic study is conducted.
    4. Data on the behavior and movement patterns of marine mammals and 
turtles seen at times with and without seismic activity.
Passive Acoustic Monitoring
    Passive acoustic monitoring (PAM) will take place to complement the 
visual monitoring program. Visual monitoring typically is not effective 
during periods of bad weather or at night, and even with good 
visibility, is unable to detect marine mammals when they are below the 
surface or beyond visual range. Acoustical monitoring can be used in 
addition to visual observations to improve detection, identification, 
localization, and tracking of cetaceans. The acoustic monitoring will 
serve to alert visual observers (if on duty) when vocalizing cetaceans 
are detected. It is only useful when marine mammals call, but it can be 
effective either by day or by night, and does not depend on good 
visibility. It will be monitored in real time so that the visual 
observers can be advised when cetaceans are detected. When bearings 
(primary and mirror-

[[Page 71617]]

image) to calling cetacean(s) are determined, the bearings will be 
relayed to the visual observer to help him/her sight the calling 
animal(s).
    The PAM system consists of hardware (i.e., hydrophones) and 
software. The ``wet end'' of the system consists of a low-noise, towed 
hydrophone array that is connected to the vessel by a ``hairy'' faired 
cable. The array will be deployed from a winch located on the back 
deck. A deck cable will connect from the winch to the main computer lab 
where the acoustic station and signal conditioning and processing 
system will be located. The lead-in from the hydrophone array is 
approximately 400 m (1312 ft) long, and the active part of the 
hydrophone array is approximately 56 m (184 ft) long. The hydrophone 
array is typically towed at depths less than 20 m (66 ft).
    The towed hydrophones will be monitored 24 h per day while at the 
seismic survey area during airgun operations, and during most periods 
when the Langseth is underway while the airguns are not operating. One 
MMO will monitor the acoustic detection system at any one time, by 
listening to the signals from two channels via headphones and/or 
speakers and watching the real-time spectrographic display for 
frequency ranges produced by cetaceans. MMOs monitoring the acoustical 
data will be on shift for 1 6 h at a time. Besides the visual MMOs, an 
additional MMO with primary responsibility for PAM will also be aboard. 
All MMOs are expected to rotate through the PAM position, although the 
most experienced with acoustics will be on PAM duty more frequently.
    When a vocalization is detected while visual observations are in 
progress, the acoustic MMO will contact the visual MMO immediately, to 
alert him/her to the presence of cetaceans (if they have not already 
been seen), and to allow a power down or shut down to be initiated, if 
required. The information regarding the call will be entered into a 
database. The data to be entered include an acoustic encounter 
identification number, whether it was linked with a visual sighting, 
date, time when first and last heard and whenever any additional 
information was recorded, position and water depth when first detected, 
bearing if determinable, species or species group (e.g., unidentified 
dolphin, sperm whale), types and nature of sounds heard (e.g., clicks, 
continuous, sporadic, whistles, creaks, burst pulses, strength of 
signal, etc.), and any other notable information. The acoustic 
detection can also be recorded for further analysis.

Mitigation

    L-DEO's mitigation procedures are based on protocols used during 
previous L-DEO seismic research cruises as approved by NMFS, and on 
best practices recommended in Richardson et al. (1995), Pierson et al. 
(1998), and Weir and Dolman (2007). The measures are described in 
detail below this section.
Proposed Safety Zones
    As noted earlier, L-DEO modeled received sound levels for the 36-
airgun array and for a single 1900LL 40-in\3\ airgun (which will be 
used during power downs), in relation to distance and direction from 
the airguns. Based on the modeling for deep water, the distances from 
the source where sound levels are predicted to be 190, 180, and 160 dB 
re 1 FPa (rms) were determined (Table 1). The 180- and 190-dB radii 
vary with tow depth of the airgun array and range up to 1120 m and 340 
m, respectively. The 180- and 190-dB levels are shut-down criteria 
applicable to cetaceans and pinnipeds, respectively, as specified by 
NMFS (2000); these levels were used to establish the safety zones. If 
the MMO detects marine mammal(s) or turtle(s) within or about to enter 
the appropriate safety radii, the airguns will be powered down (or shut 
down if necessary) immediately (see below).
Mitigation During Operations
    Mitigation measures that will be adopted during the L-DEO survey 
include: (1) speed or course alteration, provided that doing so will 
not compromise operational safety requirements; (2) power-down 
procedures; (3) shut-down procedures; (4) ramp-up procedures; and (5) 
special procedures for species of particular concern.
    Speed or Course Alteration - If a marine mammal or sea turtle is 
detected outside the safety zone and, based on its position and the 
relative motion, is likely to enter the safety zone, the vessel's speed 
and/or direct course may be changed. This would be done if practicable 
while minimizing the effect on the planned science objectives. The 
activities and movements of the marine mammal or sea turtle (relative 
to the seismic vessel) will then be closely monitored to determine 
whether the animal is approaching the applicable safety zone. If the 
animal appears likely to enter the safety zone, further mitigative 
actions will be taken, i.e., either further course alterations or a 
power down or shut down of the airguns. Typically, during seismic 
operations that use hydrophone streamers, the source vessel is unable 
to change speed or course and one or more alternative mitigation 
measures (see below) will need to be implemented.
    Power-down Procedures - A power-down involves decreasing the number 
of airguns in use such that the radius of the 180-dB (or 190-dB) zone 
is decreased to the extent that marine mammals or turtles are no longer 
in or about to enter the safety zone. A power-down of the airgun array 
can also occur when the vessel is moving from one seismic line to 
another. During a power-down for mitigation, one airgun will be 
operated. The continued operation of one airgun is intended to alert 
marine mammals and turtles to the presence of the seismic vessel in the 
area. In contrast, a shut-down occurs when all airgun activity is 
suspended.
    If a marine mammal or turtle is detected outside the safety zone 
but is likely to enter the safety radius, and if the vessel's speed 
and/or course cannot be changed to avoid having the animal enter the 
safety radius, the airguns will be powered down before the animal is 
within the safety radius. Likewise, if a mammal or turtle is already 
within the safety zone when first detected, the airguns will be powered 
down immediately. During a power-down of the airgun array, the 40-in\3\ 
airgun will be operated. If a marine mammal or turtle is detected 
within or near the smaller safety radius around that single airgun 
(Table 1), it will be shut down (see next subsection).
    Following a power-down, airgun activity will not resume until the 
marine mammal or turtle has cleared the safety zone. The animal will be 
considered to have cleared the safety zone if it: (1) is visually 
observed to have left the safety zone; or (2) has not been seen within 
the zone for 15 min in the case of small odontocetes; or (3) has not 
been seen within the zone for 30 min in the case of mysticetes and 
large odontocetes, including sperm, pygmy sperm, dwarf sperm, and 
beaked whales; or (4) the vessel has moved outside the safety zone for 
turtles, i.e., approximately 5 to 20 min, depending on the sighting 
distance, vessel speed, and tow-depth.
    Shut-down Procedures - During a power down, the operating airgun(s) 
will be shut down if a marine mammal or turtle is seen within or 
approaching the exclusion zone for a single airgun. Shut-downs will be 
implemented (1) if an animal enters the exclusion zone of the single 
airgun after a power-down has been initiated, or (2) if an animal is 
initially seen within the exclusion zone of a single airgun when more 
than one airgun (typically the full array) is

[[Page 71618]]

operating. Airgun activity will not resume until the marine mammal or 
turtle has cleared the EZ, or until the visual marine mammal observer 
(MMVO) is confident that the animal has left the vicinity of the 
vessel. Criteria for judging that the animal has cleared the EZ will be 
as described in the preceding subsection.
    Ramp-up Procedures - A ramp-up procedure will be followed when the 
airgun array begins operating after a specified period without airgun 
operations or when a power-down has exceeded that period. It is 
proposed that, for the present cruise, this period would be 
approximately 9 min. This period is based on the largest modeled 180-dB 
radius for the 36-airgun array (see Table 1) in relation to the planned 
speed of the Langseth while shooting the airguns. Similar periods 
(approximately 8 10 min) were used during previous L-DEO surveys.
    Ramp-up will begin with the smallest gun in the array (40 in\3\). 
Airguns will be added in a sequence such that the source level of the 
array will increase in steps not exceeding 6 dB per 5-min period over a 
total duration of about 35 min. During ramp-up, the MMOs will monitor 
the safety zone and if marine mammals or turtles are sighted, a course/
speed change, power down, or shut down will be implemented as though 
the full array were operational.
    If the complete safety zone has not been visible for at least 30 
min prior to the start of operations in either daylight or nighttime, 
ramp-up will not commence unless at least one airgun (40 in\3\ or 
similar) has been operating during the interruption of seismic survey 
operations. Given these provisions, it is likely that the airgun array 
will not be ramped up from a complete shut-down at night or in thick 
fog, because the outer part of the safety zone for that array will not 
be visible during those conditions. If one airgun has operated during a 
power-down period, ramp-up to full power will be permissible at night 
or in poor visibility, on the assumption that marine mammals and 
turtles will be alerted to the approaching seismic vessel by the sounds 
from the single airgun and could move away if they choose. Ramp-up of 
the airguns will not be initiated if a sea turtle or marine mammal is 
sighted within or near the applicable safety zones during the day or 
close to the vessel at night.
    Shutdown if Injured or Dead Whale is Found - In the unanticipated 
event that any cases of marine mammal injury or mortality are found and 
are judged likely to have resulted from these activities, L-DEO will 
cease operating seismic airguns and report the incident to the Office 
of Protected Resources, NMFS immediately.

Reporting

    L-DEO will submit a report to NMFS within 90 days after the end of 
the cruise. The report will describe the operations that were conducted 
and sightings of marine mammals and turtles near the operations. The 
report will provide full documentation of methods, results, and 
interpretation pertaining to all monitoring. The 90-day report will 
summarize the dates and locations of seismic operations, and all marine 
mammal and turtle sightings (dates, times, locations, activities, 
associated seismic survey activities). The report will also include 
estimates of the number and nature of exposures that could result in 
``takes'' of marine mammals by harassment or in other ways.
    All injured or dead marine mammals (regardless of cause) must be 
reported to NMFS as soon as practicable. Report should include species 
or description of animal, condition of animal, location, time first 
found, observed behaviors (if alive) and photo or video, if available.

Estimated Take by Incidental Harassment

    Because of the mitigation measures that will be required and the 
likelihood that some cetaceans will avoid the area around the operating 
airguns of their own accord, NMFS does not expect any marine mammals to 
approach the sound source close enough to be injured (Level A 
harassment). All anticipated takes would be ``takes by Level B 
harassment'', as described previously, involving temporary behavioral 
modifications or low-level physiological effects.
    Estimates of the numbers of marine mammals that might be affected 
are based on consideration of the number of marine mammals that could 
be disturbed appreciably by approximately 3,650 km of seismic surveys 
during the proposed seismic program in the Lau Basin, Tonga. Few 
systematic aircraft- or ship-based surveys have been conducted for 
marine mammals in offshore waters of the South Pacific Ocean, and the 
species of marine mammals that occur there are not well known. L-DEO's 
estimates are based on species accounts in part derived from Reeves et 
al. (1999), who summarized distribution information from the area 
served by the South Pacific Regional Environment Programme (SPREP). The 
SPREP region covers a vast area of the Pacific Ocean between the Tropic 
of Capricorn and the Equator from Papua New Guinea (140[deg] E) to 
Pitcairn Island (130[deg] W).
    It should be noted that the estimates of exposures to various sound 
levels assume that the surveys will be completed; in fact, the planned 
number of line-kilometers has been increased by 25 percent to 
accommodate lines that may need to be repeated, equipment testing, etc. 
Furthermore, any marine mammal sightings within or near the designated 
safety zone will result in the power or shut down of seismic operations 
as a mitigation measure. Thus, the following estimates of the numbers 
of marine mammals potentially exposed to 160-dB sounds are 
precautionary, and probably overestimate the actual numbers of marine 
mammals that might be involved. These estimates assume that there will 
be no weather, equipment, or mitigation delays, which is highly 
unlikely.
    The anticipated radii of influence of the MBES and SBP are less 
than those for the airgun array. It is assumed that, during 
simultaneous operations of the airgun array and the other sources, any 
marine mammals close enough to be affected by the MBES or 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 (see Possible Effects 
of Multibeam Echosounder Signals and Possible Effects of the Sub-bottom 
Profiler Signals). Such reactions are not considered to constitute 
``taking'' (NMFS 2001). Therefore, no additional allowance is included 
for animals that might be affected by sound sources other than airguns.

Density Estimates

    The basis for estimating the densities of marine mammals in the 
proposed study area is discussed in section VII of L-DEO's application. 
The density estimates used in this assessment are from one of 
Longhurst's (2007) biogeographic provinces north of the survey area 
that is oceanographically similar to the province in which the seismic 
activities will take place. Some of the surveys conducted by Ferguson 
and Barlow (2001) in the Eastern Tropical Pacific (ETP) during 1986 
1996 are in Longhurst's (2007) North Pacific Tropical Gyre Province, 
which is similar to the South Pacific Subtropical Gyre (SPSG), in which 
the proposed seismic survey will occur. The similarities are: (1) they 
are both low-nitrate, low-

[[Page 71619]]

chlorophyll regions of the oceans with numerous coral reefs, and (2) 
upwelled nutrients by islands are used by corals and do not increase 
pelagic productivity. The species assemblages that occur in the 
southwest Pacific Ocean will be different than those sighted during the 
surveys in the ETP. However, the overall abundance of species groups 
with generally similar habitat requirements are expected to be roughly 
similar.

Potential Number of Exposures to Sound Levels at or above 160 dB

    L-DEO's ``best estimate'' of the potential number of exposures of 
cetaceans, absent any mitigation measures, to seismic sounds with 
received levels at or above 160 dB re 1 microPa (rms) is 18,735 (Table 
2). L-DEO's ``maximum estimate'' of the potential number of exposures 
of cetaceans, with mitigation measures, to seismic sounds with received 
levels at or above 160 dB re 1 microPa(rms) is 10,173 (Table 2). It is 
assumed that marine mammals exposed to airgun sounds this strong might 
change their behavior sufficiently to be considered ``taken by 
harassment''.
    The number of potential exposures to sound levels at or above 160 
dB re 1 microPa (rms) were calculated by multiplying the expected 
average species density (see section VII of L-DEO's application) times 
the anticipated minimum area (17,525 km\2\, 10,889 mi2) to be 
ensonified to that level during airgun operations including overlap.
    The area expected to be ensonified was determined by entering the 
planned survey lines into a MapInfo Geographic Information System 
(GIS), using the GIS to identify the relevant areas by ``drawing'' the 
applicable 160-dB buffer around each seismic line, and then calculating 
the total area within the buffers. Areas where overlap occurred 
(because of closely-spaced lines) were included when estimating the 
number of exposures.

Number of Individual Cetaceans Exposed to Sound Levels at or above 160 
dB

    L-DEO's ``best estimate'' of the potential number of different 
individuals that could be exposed to airgun sounds with received levels 
at or above 160 dB re 1 microPa (rms) on one or more occasions is 
4,997. That total includes 11 baleen whales, four of which are 
considered endangered under the ESA: one humpback whale, one blue 
whale, one sei whale, and one fin whale, which would represent small 
numbers of the regional populations (Table 2). In addition, six sperm 
whales (also listed as endangered under the ESA) could be exposed 
during the survey, as well as 48 beaked whales (Table 2).
    The spinner dolphin is estimated to be the most common species in 
the area, with a best estimate of 1,714 spinner dolphins exposed to 
sound levels at or above 160 dB re 1 microPa(rms).
    Based on numbers of animals encountered during previous L-DEO 
seismic surveys, the likelihood of the successful implementation of the 
required mitigation measures, and the likelihood that some animals will 
avoid the area around the operating airguns, NMFS believes that L-DEOs 
airgun seismic testing program may result in the Level B harassment of 
some lower number of individual marine mammals (a few times each) than 
is indicated by the column titled, Maximum Estimate of Exposures - 
Request, in Table 2. L-DEO has asked for authorization for take of 
their ``maximum estimate'' of numbers for each species. Though NMFS 
believes that take of the requested numbers is unlikely, we still find 
these numbers small relative to the population sizes.

Potential Effects on Habitat

    The proposed seismic survey will not result in any permanent impact 
on habitats used by marine mammals, or to the food sources they use. 
The main impact issue associated with the proposed activity will be 
temporarily elevated noise levels and the associated direct effects on 
marine mammals.
    The Langseth will deploy and retrieve approximately 55-64 OBS. The 
OBS anchors will remain upon equipment recovery. Although OBS placement 
will disrupt a very small area of seafloor habitat and may disturb 
benthic invertebrates, the impacts are expected to be localized and 
transitory. The vessel will deploy the OBS in such a way that creates 
the least disturbance to the area. Thus, it is not expected that the 
placement of OBS would have adverse effects beyond naturally occurring 
changes in this environment, and any effects of the planned activity on 
marine mammal habitats and food resources are expected to be 
negligible.
    Effects on Fish and Invertebrates - 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 and invertebrate populations is very 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 
sublethal injury. Physiological effects involve temporary and permanent 
primary and secondary stress responses, such as changes in levels of 
enzymes and proteins. Behavioral effects refer to temporary and (if 
they occur) permanent changes in exhibited behavior (e.g., startle and 
avoidance behavior). The three categories are interrelated in complex 
ways. For example, it is possible that certain physiological and 
behavioral changes 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. This makes drawing conclusions about impacts on fish problematic 
because, ultimately, the most important issues concern effects on 
marine fish populations, their viability, and their availability to 
fisheries.
    The existing body of information on the impacts of seismic survey 
sound on marine invertebrates is also very limited. However, benthic 
invertebrates in the Lau Basin are not expected to be affected by 
seismic operations, as sound levels from the airguns will diminish 
dramatically by the time the sound reaches the ocean floor at a depth 
of approximately 2250 m (7382 ft).
    There is some unpublished and very limited evidence of the 
potential for adverse effects on invertebrates. 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

[[Page 71620]]

viability, including availability to fisheries. More detailed 
information on studies of potential impacts of sounds on fish and 
invertebrates is provided in Appendix E of L-DEO's application.

Negligible Impact Determination

    NMFS has preliminarily determined, provided that the aforementioned 
mitigation and monitoring measures are implemented, that the impact of 
conducting a seismic program in the southwest Pacific Ocean may result, 
at worst, in a temporary modification in behavior and/or low-level 
physiological effects (Level B Harassment) of small numbers of certain 
species of marine mammals. While behavioral and avoidance reactions may 
be made by these species in response to the resultant noise from the 
airguns, these behavioral changes are expected to have a negligible 
impact on the affected species and stocks of marine mammals.
    While the number of potential incidental harassment takes will 
depend on the distribution and abundance of marine mammals in the area 
of seismic operations, the number of potential harassment takings is 
estimated to be relatively small in light of the population size (see 
Table 2). NMFS anticipates the actual take of individuals to be lower 
than the numbers depicted in the table, because those numbers do not 
reflect either the implementation of the mitigation numbers or the fact 
that some animals will avoid the sound at levels lower than those 
expected to result in harassment. Additionally, mitigation measures 
require that the Langseth avoid any areas where marine mammals are 
concentrated.
    In addition, no take by death and/or serious injury is anticipated, 
and the potential for temporary or permanent hearing impairment will be 
avoided through the incorporation of the required mitigation measures 
described in this document. This conclusion is supported by: (1) the 
likelihood that, given sufficient notice through slow ship speed and 
ramp-up of the seismic array, marine mammals are expected to move away 
from a noise source that it is annoying prior to its becoming 
potentially injurious; (2) TTS is unlikely to occur, especially in 
odontocetes, until levels above 180 dB re 1 microPa (rms) are reached; 
(3) the fact that injurious levels of sound are only likely very close 
to the vessel; and (4) the monitoring program developed to avoid injury 
will be sufficient to detect (using visual detection and PAM), with 
reasonable certainty, all marine mammals within or entering the 
identified safety zones.

Endangered Species Act (ESA)

    Under section 7 of the ESA, the National Science Foundation (NSF) 
has begun consultation on this proposed seismic survey. NMFS will also 
consult internally on the issuance of an IHA under section 101(a)(5)(D) 
of the MMPA for this activity. Consultation will be concluded prior to 
a determination on the issuance of an IHA.

National Environmental Policy Act (NEPA)

    On September 22, 2005 (70 FR 55630), NSF published a notice of 
intent to prepare a Programmatic Environmental Impact Statement/
Overseas Environmental Impact Statement (EIS/OES) to evaluate the 
potential environmental impacts associated with the use of seismic 
sources in support of NSF-funded research by U.S. academic scientists. 
NMFS agreed to be a cooperating agency in the preparation of the EIS/
OEIS. This EIS/OEIS has not been completed. Therefore, in order to meet 
NSF's and NMFS' NEPA requirements for the proposed activity and 
issuance of an IHA to L-DEO, the NSF has prepared an Environmental 
Assessment of a Marine Geophysical Survey by the Langseth in the 
southwest Pacific Ocean off the coast of Tonga. NMFS is reviewing that 
document and will either adopt NSF's EA or conduct a separate NEPA 
analysis, as necessary, prior to making a determination of the issuance 
of the IHA. NMFS has posted NSF's EA on its website at http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications.

Preliminary Conclusions

    Based on the preceding information, and provided that the proposed 
mitigation and monitoring are incorporated, NMFS has preliminarily 
concluded that the proposed activity will incidentally take, by level B 
behavioral harassment only, small numbers of marine mammals. The 
provision requiring that the activities not have an unmitigable adverse 
impact on the availability of the affected species or stock for 
subsistence uses does not apply for this proposed action. No take by 
Level A harassment (injury) or death is anticipated and harassment 
takes should be at the lowest level practicable due to incorporation of 
the mitigation measures proposed in this document.

Proposed Authorization

    NMFS proposes to issue an IHA to L-DEO for a marine seismic survey 
in the southwest Pacific Ocean during January February, 2009, provided 
the previously mentioned mitigation, monitoring, and reporting 
requirements are incorporated.

    Dated: November 18, 2008.
James H. Lecky,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. E8-27895 Filed 11-25-08; 8:45 am]
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