Small Takes of Marine Mammals Incidental to Specified Activities; Marine Geophysical Survey of the Western Canada Basin, Chukchi Borderland and Mendeleev Ridge, Arctic Ocean, July - August, 2006, 43450-43470 [06-6616]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 71, Number 147 (Tuesday, August 1, 2006)]
[Notices]
[Pages 43450-43470]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 06-6616]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[I.D. 050306A]


Small Takes of Marine Mammals Incidental to Specified Activities; 
Marine Geophysical Survey of the Western Canada Basin, Chukchi 
Borderland and Mendeleev Ridge, Arctic Ocean, July - August, 2006

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

ACTION:  Notice; issuance of an incidental harassment authorization.

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SUMMARY:  In accordance with the Marine Mammal Protection Act (MMPA) 
regulations, notification is hereby given that NMFS has issued an 
Incidental Harassment Authorization (IHA) to University of Texas at 
Austin Institute for Geophysics (UTIG) for an Incidental Harassment 
Authorization (IHA) to take small numbers of marine mammals, by Level B 
Harassment, incidental to conducting a marine seismic survey in the 
Arctic Ocean from approximately July 15 - August 29, 2006.

DATES: Effective from July 15, 2006 through August 29, 2006.

ADDRESSES: A copy of the IHA and the application are available by 
writing 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, or by 
telephoning the contact listed here. A copy of the application 
containing a list of references used in this document may be obtained 
by writing to this address, by telephoning the contact listed here (FOR 
FURTHER INFORMATION CONTACT) or online at: https://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:  Jolie Harrison, Office of Protected 
Resources, NMFS, (301) 713-2289, ext 166.

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 U.S. 
citizens who engage in a specified activity (other than commercial 
fishing) within a specified geographical region if certain findings are 
made and either regulations are issued or, if the taking is limited to 
harassment, a notice of a proposed authorization is provided to the 
public for review.
    Authorization 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 
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 March 8, 2006, NMFS received an application from UTIG for the 
taking, by harassment, of several species of marine mammals incidental 
to conducting, with research funding from the National Science 
Foundation (NSF), a marine seismic survey in the Western Canada Basin, 
Chukchi Borderland and Mendeleev Ridge of the Arctic Ocean during July 
through August, 2006. The seismic survey will be operated in 
conjunction with a sediment coring project, which will obtain data 
regarding crustal structure. The purpose of this study is to collect 
seismic reflection and refraction data and sediment cores that reveal 
the crustal structure and composition of submarine plateaus in the 
western Amerasia Basin in the Arctic Ocean. Past studies have led many 
researchers to support the idea that the Amerasia Basin opened about a 
pivot point near the Mackenzie Delta. However, the crustal character of 
the Chukchi Borderlands could determine whether that scenario is 
correct, or whether more complicated tectonic scenarios must be devised 
to explain the presence of the Amerasia Basin. These data will assist 
in the determination of the tectonic evolution of the Amerasia Basin 
and Canada Basin which is fundamental to such basic concerns as sea 
level fluctuations and paleoclimate in the Mesozoic era.

Description of the Activity

    The Healy, a U.S. Coast Guard (USCG) Cutter ice-breaker, will 
rendezvous with the science party off Barrow on or around 15 July. The 
Healy will then sail north and arrive at the beginning of the seismic 
survey, which will start >150 km (93 mi) north of Barrow. The cruise 
will last for approximately 40 days, and it is estimated that the total 
seismic survey time will be approximately 30 days depending on ice 
conditions. Seismic survey work is scheduled to terminate west of 
Barrow about 25 August. The vessel will then sail south to Nome where 
the science party will disembark.
    The seismic survey and coring activities will take place in the 
Arctic Ocean. The overall area within which the seismic survey will 
occur is located approximately between 71[deg]36' and 79[deg]25' N., 
and between 151[deg]57' E. and

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177[deg]24' E. The bulk of the seismic survey will not be conducted in 
any country's territorial waters. The survey will occur within the 
Exclusive Economic Zone (EEZ) of the U.S. for approximately 563 km (350 
mi).
    The Healy will use a portable Multi-Channel Seismic (MCS) system to 
conduct the seismic survey. A cluster of eight airguns will be used as 
the energy source during most of the cruise, especially in deep water 
areas. The airgun array will have four 500-in\3\ Bolt airguns and four 
210-in\3\ G. guns for a total discharge volume of 2840 in\3\. In 
shallow water, occurring during the first and last portions of the 
cruise, a four 105 in\3\ GI gun array with a total discharge volume of 
420 in3 will be used. Other sound sources (see below) will also be 
employed during the cruise. The seismic operations during the survey 
will be used to obtain information on the history of the ridges and 
basins that make up the Arctic Ocean.
    The Healy will also tow a hydrophone streamer 100-150 m (328-492 
ft) behind the ship, depending on ice conditions. The hydrophone 
streamer will be up to 200 m (656 ft) long. As the source operates 
along the survey lines, the hydrophone receiving system will receive 
and record the returning acoustic signals. In addition to the 
hydrophone streamer, sea ice seismometers (SIS) will be deployed on ice 
floes ahead of the ship using a vessel-based helicopter, and then 
retrieved from behind the ship once it has passed the SIS locations. 
SISs will be deployed as much as 120 km (74 mi) ahead of the ship, and 
recovered when as much as 120 km (74 mi) behind the ship. The 
seismometers will be placed on top of ice floes with a hydrophone 
lowered into the water through a small hole drilled in the ice. These 
instruments will allow seismic refraction data to be collected in the 
heavily ice-covered waters of the region.
    The program will consist of a total of approximately 3625 km (2252 
mi) of surveys, not including transits when the airguns are not 
operating, plus scientific coring at least seven locations. Water 
depths within the study area are 40-3858 m (131-12,657 ft). Little more 
than 8 percent of the survey (approximately 300 km (186 mi)) will occur 
in water depths <100 m (328 ft), 23 percent of the survey 
(approximately 838 km (520 mi)) will be conducted in water 100-1000 m 
(328-3280 ft) deep, and most (69 percent) of the survey (approximately 
2486 km (1,544 mi)) will occur in water deeper than 1000 m (3280 ft). 
There will be additional seismic operations associated with airgun 
testing, start up, and repeat coverage of any areas where initial data 
quality is sub-standard. In addition to the airgun array, a multibeam 
sonar and sub-bottom profiler will be used during the seismic profiling 
and continuously when underway. A pinger may be used during coring to 
help direct the core bit.
    The coring operations will be conducted in conjunction with the 
seismic study from the Healy. Seismic operations will be suspended 
while the USCG Healy is on site for coring. Several more coring sites 
may be identified and sampled depending on the ability to deploy SISs 
given ice and weather conditions. The plan is to extract one core from 
six of the seven identified sample locations along the seismic survey, 
and two cores at the last site on the Chukchi Cap. The coring system to 
be used is a piston corer that is lowered to the sea floor via a deep 
sea winch. Coring is expected to occur in 400-4000-m (1,312-13,120-ft) 
water depths. The piston corer recovers a sample in PVC tubes of 10 cm 
(3.9-in) diameter. Most of the cores will be approximately 
(approximately) 5-10 m long (16.4-32.8 ft); maximum possible length 
will be approximately 24 m (79 ft). The core is designed to leave 
nothing in the ocean after recovery.

Vessel Specifications

    The Healy has a length of 128 m (420 ft), a beam of 25 m (82 ft), 
and a full load draft of 8.9 m (29 ft). The Healy is capable of 
traveling at 5.6 km/h (3 knots) through 1.4 m (4.6 ft) of ice. A 
``Central Power Plant'', four Sultzer 12Z AU40S diesel generators, 
provides electric power for propulsion and ship's services through a 60 
Hz, 3-phase common bus distribution system. Propulsion power is 
provided by two electric AC Synchronous, 11.2 MW drive motors, fed from 
the common bus through a Cycloconverter system, that turn two fixed-
pitch, four-bladed propellers. The operation speed during seismic 
acquisition is expected to be approximately 6.5 km/h (3.5 knots). When 
not towing seismic survey gear or breaking ice, the Healy cruises at 22 
km/h (12 knots) and has a maximum speed of 31.5 km/h (17 knots). It has 
a normal operating range of about 29,650 km (18,423 mi) at 23.2 km/hr 
(12.5 knots).

Seismic Source Description

    A portable MCS system will be installed on the Healy for this 
cruise. The source vessel will tow along predetermined lines one of two 
different airgun arrays (an 8-airgun array with a total discharge 
volume of 2840 in3 or a four GI gun array with a total discharge volume 
of 420 in3), as well as a hydrophone streamer. Seismic pulses will be 
emitted at intervals of approximately 60 s and recorded at a 2 ms 
sampling rate. The 60-second spacing corresponds to a shot interval of 
approximately 120 m (394 t) at the anticipated typical cruise speed.
    As the airgun array is towed along the survey line, the towed 
hydrophone array receives the reflected signals and transfers the data 
to the on-board processing system. The SISs will store returning 
signals on an internal datalogger and also relay them in real-time to 
the Healy via a radio transmitter, where they will be recorded and 
processed.
    The 8-airgun array will be configured as a four-G. gun cluster with 
a total discharge volume of 840 in\3\ and a four Bolt airgun cluster 
with a total discharge volume of 2000 in\3\. The source output is from 
246-253 dB re 1 microPa m. The two clusters are four meters apart. The 
clusters will be operated simultaneously for a total discharge volume 
of 2840 in\3\. The 4-GI gun array will be configured the same as the 
four G. gun portion of the 8-airgun array. The energy source (source 
level 239-245 dB re 1 microPa m) will be towed as close to the stern as 
possible to minimize ice interference. The 8-airgun array will be towed 
below a depressor bird at a depth of 7-20 m (23-66 ft) depending on ice 
conditions; the preferred depth is 8-10 m (26-33 ft).
    The highest sound level measurable at any location in the water 
from the airgun arrays would be slightly less than the nominal source 
level because the actual source is a distributed source rather than a 
point source. The depth at which the source is towed has a major impact 
on the maximum near-field output, and on the shape of its frequency 
spectrum. In this case, the source is expected to be towed at a 
relatively deep depth of up to 9 m (30 ft).
    The rms (root mean square) received sound levels that are used as 
impact criteria for marine mammals are not directly comparable to the 
peak or peak-to-peak values normally used to characterize source levels 
of airguns. The measurement units used to describe airgun sources, peak 
or peak-to-peak dB, are always higher than the rms dB referred to in 
much of the biological literature. A measured received level of 160 dB 
rms in the far field would typically correspond to a peak measurement 
of about 170 to 172 dB, and to a peak-to-peak measurement of about 176 
to 178 decibels, as measured for the same pulse received at the same 
location (Greene, 1997; McCauley et al., 1998, 2000). The precise 
difference between rms and peak or peak-to-peak

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values for a given pulse depends on the frequency content and duration 
of the pulse, among other factors. However, the rms level is always 
lower than the peak or peak-to-peak level for an airgun-type source. 
Additional discussion of the characteristics of airgun pulses is 
included in Appendix A of UTIG's application.

Safety Radii

    NMFS has determined that for acoustic effects, using acoustic 
thresholds in combination with corresponding safety radii is the most 
effective way to consistently both apply measures to avoid or minimize 
the impacts of an action and to quantitatively estimate the effects of 
an action. Thresholds are used in two ways: (1) To establish a 
mitigation shut-down or power down zone, i.e., if an animal enters an 
area calculated to be ensonified above the level of an established 
threshold, a sound source is powered down or shut down; and (2) to 
calculate take, in that a model may be used to calculate the area 
around the sound source that will be ensonified to that level or above, 
then, based on the estimated density of animals and the distance that 
the sound source moves, NMFS can estimate the number of marine mammals 
that may be ``taken''. NMFS believes that to avoid permanent 
physiological damage (Level A Harassment), cetaceans and pinnipeds 
should not be exposed to pulsed underwater noise at received levels 
exceeding, respectively, 180 and 190 dB re 1 microPa (rms). NMFS also 
assumes that cetaceans or pinnipeds exposed to levels exceeding 160 dB 
re 1 microPa (rms) may experience Level B Harassment.
    In order to implement shut-down zones, or to estimate how many 
animals may potentially be exposed to a particular sound level using 
the acoustic thresholds described above, it is necessary to understand 
how sound will propagate in a particular situation. Models may be used 
to estimate at what distance from the sound source the water will be 
ensonified to a particular level. Safety radii represent the estimated 
distance from the sound source at which the received level of sound 
would correspond to the acoustic thresholds of 190, 180, and 160 dB. 
Many models have been field tested in the water. Field verification has 
shown that some of the predictions are close to being accurate, and 
some are not.
    UTIG originally proposed to base the safety radii for the Healy 
cruise on a model created by the Lamont-Doherty Earth Observatory and 
field tested in the Gulf of Mexico. Subsequently, UTIG proposed to 
enlarge some of the safety radii that relate to shut-down zones to 
provide further protection for marine mammals that may be in the area 
during seismic operations. The model utilized by UTIG to develop their 
safety radii is described below.
Safety Radii Proposed by UTIG
    Received sound fields have been modeled by Lamont-Doherty Earth 
Observatory (L-DEO) for the 8-airgun and 4-GI gun arrays that will be 
used during this survey. Predicted sound fields were modeled using 
sound exposure level (SEL) units (dB re 1 microPa\2\ s), because a 
model based on those units tends to produce more stable output when 
dealing with mixed-gun arrays like the one to be used during this 
survey. The predicted SEL values can be converted to rms received 
pressure levels, in dB re 1 microPa (as used in NMFS' impact criteria 
for pulsed sounds) by adding approximately 15 dB to the SEL value 
(Greene, 1997; McCauley et al., 1998, 2000). The rms pressure is an 
average over the pulse duration. This is the measure commonly used in 
studies of marine mammal reactions to airgun sounds, and in NMFS 
guidelines concerning levels above which ``taking'' might occur. The 
rms level of a seismic pulse is typically about 10 dB less than its 
peak level.
    The empirical data concerning 190, 180, and 160 dB (rms) distances 
in deep and shallow water acquired for various airgun array 
configurations during the acoustic verification study conducted by L-
DEO in the northern Gulf of Mexico. Tolstoy et al., (2004a, b) 
demonstrate that L-DEO's model tends to overestimate the distances 
applied in deep water. UTIG's study area will occur mainly in water 
approximately 40-3858 m (131-12,657 ft) deep, with only approximately 8 
percent of the survey lines in shallow (<100 m (<328 ft)) water and 
approximately 23 percent of the trackline in intermediate water depths 
(100-1000 m (328-3,280 ft)). The calibration-study results showed that 
radii around the airguns where the received level would be 180 dB re 1 
microPa (rms), the safety criterion applicable to cetaceans (NMFS 
2000), vary with water depth. Similar depth-related variation is likely 
in the 190-dB distances applicable to pinnipeds.
    UTIG has applied the empirical data collected during the Gulf of 
Mexico verification study to the L-DEO model in the manner described 
below to develop the safety radii listed in Table 1:
     The empirical data indicate that, for deep water (>1000 
m), the L-DEO model tends to overestimate the received sound levels at 
a given distance (Tolstoy et al., 2004a,b). However, to be 
precautionary pending acquisition of additional empirical data, UTIG 
will use the values predicted by L-DEO's modeling in deep water, after 
conversion from SEL to rms (Table 1).
     Empirical measurements were not conducted for intermediate 
depths (100-1000 m). On the expectation that results would be 
intermediate between those from shallow and deep water, a 1.5 
correction factor is applied to the estimates provided by the model for 
deep water situations
     Empirical measurements were not made for the 4 GI guns 
that will be employed during the proposed survey in shallow water (<100 
m). (The 8-airgun array will not be used in shallow water.) The 
empirical data on operations of two 105 in\3\ GI guns in shallow water 
showed that modeled values underestimated the distance to the actual 
160 dB sound level radii in shallow water by a factor of approximately 
3 (Tolstoy et al., 2004b). Sound level measurements for the 2 GI guns 
were not available for distances <0.5 km (.31 mi)(from the source. The 
radii estimated here for the 4 GI guns operating in shallow water are 
derived from the L-DEO model, with the same adjustments for depth-
related differences between modeled and measured sound levels as were 
used for 2 GI guns in earlier applications. Correction factors for the 
different sound level radii are approximately 12x the model estimate 
for the 190 dB radius in shallow water, approximately 7x for the 180 dB 
radius and approximately 4x for the 170 dB radius [Tolstoy 2004a,b]).
    As mentioned previously, subsequent to the submission of their 
application, UTIG proposed expanded safety radii, as they apply to the 
powerdown and shutdown zones for marine mammals, and these will be used 
in this project and are indicated in Table 1.

Other Acoustic Devices

    Along with the airgun operations, additional acoustical systems 
will be operated during much of or the entire cruise. The ocean floor 
will be mapped with a multibeam sonar, and a sub-bottom profiler will 
be used. These two systems are commonly operated simultaneously with an 
airgun system. An acoustic Doppler current profiler will also be used 
through the course of the project, as well as a pinger.
Multibeam Echosounder (SeaBeam 2112)
    A SeaBeam 2112 multibeam 12 kHz bathymetric sonar system will be 
used on the Healy, with a maximum source output of 237 dB re 1 microPa 
at one meter.

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 The transmit frequency is a very narrow band, less than 200 Hz, and 
centered at 12 kHz. Pulse lengths range from less than one millisecond 
to 12 ms. The transmit interval ranges from 1.5 s to 20 s, depending on 
the water depth, and is longer in deeper water. The SeaBeam system 
consists of a set of underhull projectors and hydrophones. The 
transmitted beam is narrow (approximately 2[deg]) in the fore-aft 
direction but broad (approximately 132[deg]) in the cross-track 
direction. The system combines this transmitted beam with the input 
from an array of receiving hydrophones oriented perpendicular to the 
array of source transducers, and calculates bathymetric data (sea floor 
depth and some indications about the character of the seafloor) with an 
effective 2[deg] by 2[deg] foot print on the seafloor. The SeaBeam 2112 
system on the Healy produces a useable swath width of slightly
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    more than 2 times the water depth. This is narrower than normal 
because of the ice-protection features incorporated into the system on 
the Healy.
Hydrographic Sub-bottom Profiler (Knudsen 320BR)
    The Knudsen 320BR will provide information on sedimentary layering, 
down to between 20 and 70 m, depending on bottom type and slope. It 
will be operated with the multibeam bathymetric sonar system that will 
simultaneously map the bottom topography.
    The Knudsen 320BR sub-bottom profiler is a dual-frequency system 
with operating frequencies of 3.5 and 12 kHz:
    Low frequency - Maximum output power into the transducer array, as 
wired on the Healy (125 ohms), at 3.5 kHz is approximately 6000 watts 
(electrical), which results in a maximum source level of 221 dB re 1 
microPa at 1 m downward. Pulse lengths range from 1.5 to 24 ms with a 
bandwidth of 3 kHz (FM sweep from 3 kHz to 6 kHz). The repetition rate 
is range dependent, but the maximum is a 1-percent duty cycle. Typical 
repetition rate is between 1/2 second (in shallow water) to 8 seconds 
in deep water.
    High frequency - The Knudsen 320BR is capable of operating at 12 
kHz; but the higher frequency is rarely used because it interferes with 
the SeaBeam 2112 multibeam sonar, which also operates at 12 kHz. The 
calculated maximum source level (downward) is 215 dB re 1 microPa at 1 
m (3.28 ft). The pulse duration is typically 1.5 to 5 ms with the same 
limitations and typical characteristics as the low frequency channel.
    A single 12 kHz transducer and one 3.5 kHz, low frequency (sub-
bottom) transducer array, consisting of 16 elements in a 4 by 4 array 
will be used for the Knudsen 320BR. The 12 kHz transducer (TC-12/34) 
emits a conical beam with a width of 30[deg] and the 3.5 kHz transducer 
(TR109) emits a conical beam with a width of 26[deg].
12-kHz Pinger (Benthos 2216)
    A Benthos 12-kHz pinger may be used during coring operations, to 
monitor the depth of the corer relative to the sea floor. The pinger is 
a battery-powered acoustic beacon that is attached to the coring 
mechanism. The pinger produces an omnidirectional 12 kHz signal with a 
source output of approximately 192 dB re 1 microPa m at a one pulse per 
second rate. The pinger produces a single pulse of 0.5, 2 or 10 ms 
duration (hardware selectable within the unit) every second.

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Acoustic Doppler Current Profiler (150 kHz)
    The 150 kHz acoustic Doppler current profiler (ADCP ) has a minimum 
ping rate of 0.65 ms. There are four beam sectors, and each beamwidth 
is 3[deg]. The pointing angle for each beam is 30[deg] off from 
vertical with one each to port, starboard, forward and aft. The four 
beams do not overlap. The 150 kHz ADCP's maximum depth range is 300 m.
Acoustic Doppler Current Profiler (RD Instruments Ocean Surveyor 75)
    The Ocean Surveyor 75 is an ADCP operating at a frequency of 75 
kHz, producing a ping every 1.4 s. The system is a four-beam phased 
array with a beam angle of 30[deg]. Each beam has a width of 4[deg], 
and there is no overlap. Maximum output power is 1 kW with a maximum 
depth range of 700 m (2,297 ft).

Description of Habitat and Marine Mammals Affected by the Activity

    A description of the Beaufort and Chukchi sea ecosystems and their 
associated marine mammals can be found in several documents (Corps of 
Engineers, 1999; NMFS, 1999; Minerals Management Service (MMS), 2006, 
1996 and 1992). MMS' Programmatic Environmental Assessment (PEA) - 
Arctic Ocean Outer Continental Shelf Seismic Surveys - 2006 may be 
viewed at: https://www.mms.gov/alaska/.

Marine Mammals

    A total of 8 cetacean species, 4 species of pinnipeds, and 1 marine 
carnivore are known to or may occur in or near UTIG's study area (Table 
2). Two of these species, the bowhead and fin whale, are listed as 
``Endangered'' under the ESA, but the fin whale is unlikely to be 
encountered along the planned trackline.
    The marine mammals that occur in the survey area belong to three 
taxonomic groups: odontocetes (toothed cetaceans, such as beluga whale 
and narwhal whale), mysticetes (baleen whales), and carnivora 
(pinnipeds and polar bears). Cetaceans and pinnipeds (except walrus) 
are the subject of the IHA Application to NMFS; in the U.S., the walrus 
and polar bear are managed by the USFWS.
    The marine mammal species most likely to be encountered during the 
seismic survey include one or perhaps two cetacean species (beluga and 
perhaps bowhead whale), three pinniped species (ringed seal, bearded 
seal, and walrus), and the polar bear. However, most of these will 
occur in low numbers and encounters with most species are likely to be 
most common within 100 km (62 mi) of shore where no seismic work is 
planned to take place. The marine mammal most likely to be encountered 
throughout the cruise is the ringed seal. Concentrations of walruses 
might also be encountered in certain areas, depending on the location 
of the edge of the pack ice relative to their favored shallow-water 
foraging habitat. The most widely distributed marine mammals are 
expected to be the beluga, ringed seal, and polar bear.
    Three additional cetacean species, the gray whale, minke whale and 
fin whale, could occur in the project area. It is unlikely that gray 
whales will be encountered near the trackline; if encountered at all, 
gray whales would be found closer to the Alaska coastline where no 
seismic work is planned. Minke and fin whales are extralimital in the 
Chukchi Sea and will not likely be encountered as the trackline borders 
their known range. Two additional pinniped species, the harbor and 
spotted seal, are also unlikely to be seen.
    Table 2 also shows the estimated abundance and densities of the 
marine mammals likely to be encountered during the Healy's Arctic 
cruise. Additional information regarding the distribution of these 
species and how the estimated densities were calculated may be found in 
UTIG's application and NMFS' Updated Species Reports at: (https://
www.nmfs.noaa.gov/pr/readingrm/MMSARS/2005alaskasummarySARs.pdf).
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Potential Effects on Marine Mammals

Potential Effects of Airguns

    The effects of sounds from airguns might include one or more of the 
following: tolerance, masking of natural sounds, behavioral 
disturbance, and at least in theory, temporary or permanent hearing 
impairment, or non-auditory physical effects (Richardson et al., 1995). 
Because the airgun sources planned for use during the present project 
involve only 4 or 8 airguns, the effects are anticipated to be less 
than would be the case with a large array of airguns. It is very 
unlikely that there would be any cases of temporary or especially 
permanent hearing impairment, or non-auditory physical effects. Also, 
behavioral disturbance is expected to be limited to relatively short 
distances.
Tolerance
    Numerous studies have shown that pulsed sounds from airguns are 
often readily detectable in the water at distances of many kilometers. 
Numerous studies have shown that marine mammals at distances more than 
a few kilometers from operating seismic vessels often show no apparent 
response (see Appendix A (e) of 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, small 
odontocetes, and sea otters seem to be more tolerant of exposure to 
airgun pulses than are baleen whales.
Masking
    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 of relevance. 
Some whales are known to continue calling in the presence of seismic 
pulses. Their calls can be heard between the seismic pulses (e.g., 
Richardson et al., 1986; McDonald et al., 1995; Greene et al., 1999; 
Nieukirk et al., 2004). Although there has been one report that sperm 
whales cease calling when exposed to pulses from a very distant seismic 
ship (Bowles et al., 1994), a more recent study reports that sperm 
whales off northern Norway continued calling in the presence of seismic 
pulses (Madsen et al., 2002). That has also been shown during recent

[[Page 43456]]

work in the Gulf of Mexico (Tyack et al., 2003). Masking effects of 
seismic pulses are expected to be negligible in the case of the smaller 
odontocete cetaceans, given the intermittent nature of seismic pulses. 
Also, the sounds important to small odontocetes are predominantly at 
much higher frequencies than are airgun sounds. For more information on 
masking effects, see Appendix A (d) of the application.
Disturbance Reactions
    Disturbance includes a variety of effects, including subtle changes 
in behavior, more conspicuous changes in activities, and displacement. 
Reactions to sound, if any, depend on species, state of maturity, 
experience, current activity, reproductive state, time of day, and many 
other factors. If a marine mammal does react briefly to an underwater 
sound by changing its behavior or moving a small distance, the impacts 
of the change are unlikely to be significant to the individual, let 
alone the stock or the species as a whole. Alternatively, if a sound 
source displaces marine mammals from an important feeding or breeding 
area for a prolonged period, impacts on the animals are most likely 
significant. There are some uncertainties in predicting the quantity 
and types of impacts of noise on marine mammals. When attempting to 
quantify potential take for an authorization, NMFS estimates how many 
mammals were likely within a certain distance of sound level that 
equates to the received sound level.
    The sound criteria used to estimate how many marine mammals might 
be disturbed to some biologically-important degree by a seismic program 
are based on behavioral observations during studies of several species. 
However, information is lacking for many species. Detailed studies have 
been done on humpback, gray, and bowhead whales, and on ringed seals. 
Less detailed data are available for some other species of baleen 
whales, sperm whales, small toothed whales, and sea otters.
    Baleen Whales: Baleen whales generally tend to avoid operating 
airguns, but avoidance radii are quite variable. Whales are often 
reported to show no overt reactions to pulses from large arrays of 
airguns at distances beyond a few kilometers, even though the airgun 
pulses remain well above ambient noise levels out to much longer 
distances. However, as reviewed in Appendix A (e) of the 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 case of the 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, bowhead, and humpback whales have determined that 
received levels of pulses in the 160-170 dB re 1 microPa rms range seem 
to cause obvious avoidance behavior in a substantial fraction of the 
animals exposed. In many areas, seismic pulses from large arrays of 
airguns diminish to those levels at distances ranging from 4.5 to 14.5 
km (2.8-9 mi) from the source. A substantial proportion of the baleen 
whales within those distances may show avoidance or other strong 
disturbance reactions to the airgun array. Subtle behavioral changes 
sometimes become evident at somewhat lower received levels, and recent 
studies reviewed in Appendix A (e) of the 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. Bowhead whales migrating west across the Alaskan 
Beaufort Sea in autumn, in particular, are unusually responsive, with 
substantial avoidance occurring out to distances of 20-30 km (12.4-18.6 
mi) from a medium-sized airgun source (Miller et al., 1999; Richardson 
et al., 1999). More recent research on bowhead whales (Miller et al., 
2005), however, suggests that during the summer feeding season (during 
which the project will take place) bowheads are not nearly as sensitive 
to seismic sources and can be expected to react to the more typical 
160-170 dB re 1 Pa rms range.
    Malme et al. (1986, 1988) studied the responses of feeding eastern 
gray whales to pulses from a single 100 in3 airgun off St. Lawrence 
Island in the northern Bering Sea. They estimated, based on small 
sample sizes, that 50 percent of feeding gray whales ceased feeding at 
an average received pressure level of 173 dB re 1 microPa on an 
(approximate) rms basis, and that 10 percent of feeding whales 
interrupted feeding at received levels of 163 dB. Those findings were 
generally consistent with the results of experiments conducted on 
larger numbers of gray whales that were migrating along the California 
coast.
    Data on short-term reactions (or lack of reactions) of cetaceans to 
impulsive noises do not necessarily provide information about long-term 
effects. It is not known whether impulsive noises affect reproductive 
rate or distribution and habitat use in subsequent days or years. 
However, gray whales continued to migrate annually along the west coast 
of North America despite intermittent seismic exploration and much ship 
traffic in that area for decades (Appendix A in Malme et al.,1984). 
Bowhead whales continued to travel to the eastern Beaufort Sea each 
summer despite seismic exploration in their summer and autumn range for 
many years (Richardson et al.,1987). Populations of both gray whales 
and bowhead whales grew substantially during this time. In any event, 
the brief exposures to sound pulses from the Healy's airgun source are 
highly unlikely to result in prolonged effects.
    Toothed Whales: Little systematic information is available about 
reactions of toothed whales to noise pulses. Few studies similar to the 
more extensive baleen whale/seismic pulse work summarized above and in 
Appendix A of the application have been reported for toothed whales. 
However, systematic work on sperm whales is underway (Tyack et al., 
2003), 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).
    Seismic operators sometimes see dolphins and other small toothed 
whales near operating airgun arrays, but in general there seems to be a 
tendency for most delphinids to show some limited avoidance of seismic 
vessels operating large airgun systems. However, 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. Nonetheless, there have been indications that small toothed 
whales sometimes move away, or maintain a somewhat greater distance 
from the vessel, when a large array of airguns is operating than when 
it is silent (e.g., Goold, 1996a,b,c; Calambokidis and Osmek, 1998; 
Stone, 2003). Aerial surveys during seismic operations in the 
southeastern Beaufort Sea recorded much lower sighting rates of beluga 
whales within 10-20 km (6.2-12.4 mi) of an active seismic vessel. These 
results were consistent with the low number of beluga sightings 
reported by observers aboard the seismic vessel, suggesting that some 
belugas might be avoiding the seismic operations at distances of 10-20 
km (6.2-12.4 mi) (Miller et al., 2005).
    Similarly, captive bottlenose dolphins and (of some relevance in 
this project) beluga whales exhibit changes in

[[Page 43457]]

behavior when exposed to strong pulsed sounds similar in duration to 
those typically used in seismic surveys (Finneran et al., 2000, 2002). 
However, the animals tolerated high received levels of sound (pk-pk 
level >200 dB re 1 microPa) before exhibiting aversive behaviors. With 
the presently-planned source, such levels would be found within 
approximately 400 m (1,312 ft) of the 4 GI guns operating in shallow 
water.
    Odontocete reactions to large arrays of airguns are variable and, 
at least for small odontocetes, seem to be confined to a smaller radius 
than has been observed for mysticetes. UTIG proposed using a 170-dB 
acoustic threshold for behavioral disturbance of delphinids and 
pinnipeds in lieu of the 160-dB NMFS currently uses as the standard 
threshold. However, NMFS does not believe there is enough data to 
support changing the threshold at this time and will utilize the 160 dB 
safety radii. NMFS is currently developing new taxa-specific acoustic 
criteria and they are scheduled to be made available to the public 
within the next two years.
    Pinnipeds: Pinnipeds are not likely to show a strong avoidance 
reaction to the medium-sized airgun sources that will be used. Visual 
monitoring from seismic vessels has shown only slight (if any) 
avoidance of airguns by pinnipeds, and only slight (if any) changes in 
behavior-see Appendix A (e) of the application. Those studies show that 
pinnipeds frequently do not avoid the area within a few hundred meters 
of operating airgun arrays (e.g., Miller et al., 2005; Harris et al., 
2001). However, initial telemetry work suggests that avoidance and 
other behavioral reactions to small airgun sources may at times be 
stronger than evident to date from visual studies of pinniped reactions 
to airguns (Thompson et al., 1998). Even if reactions of the species 
occurring in the present study area are as strong as those evident in 
the telemetry study, reactions are expected to be confined to 
relatively small distances and durations, with no long-term effects on 
pinniped individuals or populations.
Hearing Impairment and Other Physical Effects
    Temporary or permanent hearing impairment is a possibility when 
marine mammals are exposed to very strong sounds, but there has been no 
specific documentation of this for marine mammals exposed to sequences 
of airgun pulses. Current NMFS practice regarding exposure of marine 
mammals to high-level sounds is to establish mitgation that will avoid 
cetaceans and pinnipeds exposure to impulsive sounds 180 and 190 dB re 
1 Pa (rms), respectively (NMFS, 2000). Those criteria have been used in 
defining the safety (shut down) radii planned for UTIG's seismic 
survey. As summarized here,
     The 180 dB criterion for cetaceans may be lower than 
necessary to avoid temporary threshold shift (TTS), let alone permanent 
auditory injury, at least for belugas and delphinids.
     The minimum sound level necessary to cause permanent 
hearing impairment is higher, by a variable and generally unknown 
amount, than the level that induces barely-detectable TTS.
     The level associated with the onset of TTS is often 
considered to be a level below which there is no danger of permanent 
damage.
    NMFS is presently developing new noise exposure criteria for marine 
mammals that account for the now-available scientific data on TTS and 
other relevant factors in marine and terrestrial mammals.
    Several aspects of the required monitoring and mitigation measures 
for this project are designed to detect marine mammals occurring near 
the airguns (and multi-beam bathymetric sonar), and to avoid exposing 
them to sound pulses that might, at least in theory, cause hearing 
impairment (see Mitigation). In addition, many cetaceans are likely to 
show some avoidance of the area with high received levels of airgun 
sound (see above). 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 theoretically might 
occur in mammals close to a strong sound source include stress, 
neurological effects, bubble 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 and 
beaked whales do not occur in the present study area. It is unlikely 
that any effects of these types would occur during the present project 
given the brief duration of exposure of any given mammal, and the 
planned monitoring and mitigation measures (see below). The following 
subsections discuss in somewhat more detail the possibilities of TTS, 
permanent threshold shift (PTS), and non-auditory physical effects.
    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. 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 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.
    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., 2005, 2002). Given the 
available data, the received level of a single seismic pulse might need 
to be approximately 210 dB re 1 Pa rms (approximately 221-226 dB pk-pk) 
in order to produce brief, mild TTS. Exposure to several seismic pulses 
at received levels near 200-205 dB (rms) might result in slight TTS in 
a small odontocete, assuming the TTS threshold is (to a first 
approximation) a function of the total received pulse energy. Seismic 
pulses with received levels of 200-205 dB or more are usually 
restricted to a radius of no more than 200 m around a seismic vessel 
operating a large array of airguns.
    For baleen whales, there are no data, direct or indirect, on levels 
or properties of sound that are required to induce TTS. However, no 
cases of TTS are expected given the moderate size of the source, and 
the strong likelihood that baleen whales would avoid the approaching 
airguns (or vessel) before being exposed to levels high enough for 
there to be any possibility of TTS.
    In pinnipeds, TTS thresholds associated with exposure to brief 
pulses (single or multiple) of underwater sound have not been measured. 
Initial evidence from prolonged exposures suggested that some pinnipeds 
may incur TTS at somewhat lower received levels than do small 
odontocetes exposed for similar durations (Kastak et al., 1999; Ketten 
et al., 2001; cf. Au et al., 2000).
    A marine mammal within a radius of 100 m (328 ft) around a typical 
large array of operating airguns might be exposed to a few seismic 
pulses with levels of 205 dB, and possibly more pulses if the mammal 
moved with the

[[Page 43458]]

seismic vessel. The sound level radius would be similar (100 m) around 
the 8-airgun array while surveying in intermediate depths (100-1000 m). 
This would occur for <23 percent (approximately 838 km (520 mi)) of the 
survey when the survey will be conducted in intermediate depths. Also, 
the PIs propose using the 4 GI guns for some of the intermediate-depth 
survey, which would greatly reduce the 205 dB sound radius. (As noted 
above, most cetacean species tend to avoid operating airguns, although 
not all individuals do so.) However, several of the considerations that 
are relevant in assessing the impact of typical seismic surveys with 
arrays of airguns are not directly applicable here:
     ``Ramping up'' (soft start) is standard operational 
protocol during startup of large airgun arrays. Ramping up involves 
starting the airguns in sequence, usually commencing with a single 
airgun and gradually adding additional airguns. This practice will be 
employed when either airgun array is operated.
     It is unlikely that cetaceans would be exposed to airgun 
pulses at a sufficiently high level for a sufficiently long period to 
cause more than mild TTS, given the relative movement of the vessel and 
the marine mammal. In this project, most of the seismic survey will be 
in deep water where the radius of influence and duration of exposure to 
strong pulses is smaller.
     With a large array of airguns, TTS would be most likely in 
any odontocetes that bow-ride or otherwise linger near the airguns. In 
the present project, the anticipated 180-dB distances in deep and 
intermediate-depth water are 716 m (2,349 ft) and 1074 m (3,524 ft), 
respectively, for the 8-airgun gun system (Table 1) and 246 m (840 ft) 
and 369 m (1,207 ft), respectively for the 4-GI gun system. The 
waterline at the bow of the Healy will be approximately 123 m (404 ft) 
ahead of the airgun. However, no species that occur within the project 
area are expected to bow-ride.
    The predicted 180 and 190 dB distances for the airguns operated by 
UTIG vary with water depth. They are estimated to be 716 m (2,349 ft) 
and 230 m (754 ft), respectively, in deep water for the 8-airgun 
system, and 246 m (807 ft) and 75 m (246 ft), respectively, in deep 
water for the 4-GI gun system. In intermediate depths, these distances 
are predicted to increase to 1074 m (3,523 ft) and 345 m (1,131 ft), 
respectively for the 8-airgun system, and 369 m (1,210 ft) and 113 m 
(371 ft), respectively for the 4-GI gun system. The predicted 180 and 
190 dB distances for the 4-GI gun system in shallow water are 1822 m 
(5,978 ft) and 938 m (3,077 ft), respectively (Table 1). The 8-airgun 
array will not be operated in shallow water. Shallow water (<100 m (328 
ft)) will occur along only 300 km (186 mi) (approximately 8 percent) of 
the planned trackline. Furthermore, those sound levels are not 
considered to be the levels above which TTS might occur. Rather, they 
are the received levels above which, in the view of a panel of 
bioacoustics specialists convened by NMFS before TTS measurements for 
marine mammals started to become available, one could not be certain 
that there would be no injurious effects, auditory or otherwise, to 
marine mammals. As summarized above, data that are now available imply 
that TTS is unlikely to occur unless odontocetes are exposed to airgun 
pulses much stronger than 180 dB re 1 ~Pa rms and since no bow-riding 
species occur in the study area, it is unlikely such exposures will 
occur.
    PTS: When PTS occurs, there is physical damage to the sound 
receptors in the ear. In some cases, there can be total or partial 
deafness, whereas in other cases, the animal has an impaired ability to 
hear sounds in specific frequency ranges.
    There is no specific evidence that exposure to pulses of airgun 
sound can cause PTS in any marine mammal, even with large arrays of 
airguns. However, given the possibility that mammals close to an airgun 
array might incur TTS, there has been further speculation about the 
possibility that some individuals occurring very close to airguns might 
incur PTS. Single or occasional occurrences of mild TTS are not 
indicative of permanent auditory damage in terrestrial mammals. 
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 the strong sound pulses with very rapid rise time-see 
Appendix A (f) of the application.
    It is highly unlikely that marine mammals could receive sounds 
strong enough (and over a sufficient duration) to cause permanent 
hearing impairment during a project employing the medium-sized airgun 
sources planned here. In UTIG's project, marine mammals are unlikely to 
be exposed to received levels of seismic pulses strong enough to cause 
TTS, as they would probably need to be within 100-200 m (328-656 ft) of 
the airguns for that to occur. Given the higher level of sound 
necessary to cause PTS, it is even less likely that PTS could occur. In 
fact, even the levels immediately adjacent to the airgun may not be 
sufficient to induce PTS, especially because a mammal would not be 
exposed to more than one strong pulse unless it swam immediately 
alongside the airgun for a period longer than the inter-pulse interval. 
Baleen whales generally avoid the immediate area around operating 
seismic vessels. The planned monitoring and mitigation measures, 
including visual monitoring, power downs, and shut downs of the airguns 
when mammals are seen within the ``safety radii'', will minimize the 
already-minimal 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, and other types of organ or tissue damage. 
However, studies examining such effects are very limited. If any such 
effects do occur, they probably would be limited to unusual situations 
when animals might be exposed at close range for unusually long 
periods. It is doubtful that any single marine mammal would be exposed 
to strong seismic sounds for sufficiently long that significant 
physiological stress would develop. That is especially so in the case 
of this project where the airgun configuration is moderately sized, the 
ship is moving at 3-4 knots (5.5-7.4 km/hr), and for the most part, the 
tracklines will not ``double back'' through the same area.
    Until recently, it was assumed that diving marine mammals are not 
subject to the bends or air embolism. This possibility was first 
explored at a workshop (Gentry [ed.], 2002) held to discuss whether the 
stranding of beaked whales in the Bahamas in 2000 (Balcomb and 
Claridge, 2001; NOAA and USN, 2001) might have been related to bubble 
formation in tissues caused by exposure to noise from naval sonar. 
However, the opinions were inconclusive. Jepson et al. (2003) first 
suggested a possible link between mid-frequency sonar activity and 
acute and chronic tissue damage that results from the formation in vivo 
of gas bubbles, based on the beaked whale stranding in the Canary 
Islands in 2002 during naval exercises. Fernandez et al. (2005a) showed 
those beaked whales did indeed have gas bubble-associated lesions as 
well as fat embolisms. Fernandez et al. (2005b) also found evidence of 
fat embolism in three beaked whales that stranded 100 km north of the 
Canaries in 2004 during naval exercises. Examinations of several other 
stranded

[[Page 43459]]

species have also revealed evidence of gas and fat embolisms (e.g., 
Arbelo et al., 2005; Jepson et al., 2005a; Mendez et al., 2005). Most 
of the afflicted species were deep divers. There is speculation that 
gas and fat embolisms may occur if cetaceans ascend unusually quickly 
when exposed to aversive sounds, or if sound in the environment causes 
the destabilization of existing bubble nuclei (Potter, 2004; Arbelo et 
al., 2005; Fernandez et al., 2005a; Jepson et al., 2005b). Even if gas 
and fat embolisms can occur during exposure to mid-frequency sonar, 
there is no evidence that that type of effect occurs in response to 
airgun sounds. Also, most evidence for such effects have been in beaked 
whales, which do not occur in UTIG's study area.
    In general, little is known about the potential for seismic survey 
sounds to cause auditory impairment or other physical effects in marine 
mammals. Available data suggest that such effects, if they occur at 
all, would be limited to short distances and probably to projects 
involving large arrays of airguns. However, the available data do not 
allow for 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 (including belugas), and some 
pinnipeds, are especially unlikely to incur auditory impairment or 
other physical effects. Also, the planned monitoring and mitigation 
measures include shut downs of the airguns, which will reduce any such 
effects that might otherwise occur.
Strandings and Mortality
    Marine mammals close to underwater detonations of high explosive 
can be killed or severely injured, and the auditory organs are 
especially susceptible to injury (Ketten et al., 1993; Ketten, 1995). 
Airgun pulses are less energetic and have slower rise times, and there 
is no proof 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, 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. Appendix A (g) 
of the application provides additional details.
    Seismic pulses and mid-frequency sonar pulses are quite different. 
Sounds produced by airgun arrays are broadband with most of the energy 
below 1 kHz. Typical military mid-frequency sonars operate at 
frequencies of 2-10 kHz, generally with a relatively narrow bandwidth 
at any one time. 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 pulses can, in 
special circumstances, lead to physical damage and mortality (NOAA and 
USN, 2001; Jepson et al., 2003; Fernandez et al., 2005a), even if only 
indirectly, suggests that caution is warranted when dealing with 
exposure of marine mammals to any high-intensity pulsed sound.
    In May 1996, 12 Cuvier's beaked whales stranded along the coasts of 
Kyparissiakos Gulf in the Mediterranean Sea. That stranding was 
subsequently linked to the use of low- and medium-frequency active 
sonar by a North Atlantic Treaty Organization (NATO) research vessel in 
the region (Frantzis, 1998). In March 2000, a population of Cuvier's 
beaked whales being studied in the Bahamas disappeared after a U.S. 
Navy task force using mid-frequency tactical sonars passed through the 
area; some beaked whales stranded (Balcomb and Claridge, 2001; NOAA and 
USN, 2001).
    In September 2002, a total of 14 beaked whales of various species 
stranded coincident with naval exercises in the Canary Islands (Martel, 
n.d.; Jepson et al., 2003; Fernandez et al., 2003). Also in September 
2002, there was a stranding of two Cuvier's beaked whales in the Gulf 
of California, Mexico, when the L-DEO vessel Maurice Ewing was 
operating a 20 airgun, 8490 in\3\ array in the general area. The link 
between the stranding and the seismic surveys was inconclusive and not 
based on any physical evidence (Hogarth, 2002; Yoder, 2002). 
Nonetheless, that plus the incidents involving beaked whale strandings 
near naval exercises suggests a need for caution in conducting seismic 
surveys in areas occupied by beaked whales. However, no beaked whales 
are found within this project area and the planned monitoring and 
mitigation measures are expected to minimize any possibility for 
mortality of other species.

Potential Effects of Other Acoustic Devices

Bathymetric Sonar Signals
    A SeaBeam 2112 multibeam 12 kHz bathymetric sonar system will be 
operated from the source vessel essentially continuously during the 
planned study. Sounds from the multibeam are very short pulses, 
depending on water depth. Most of the energy in the sound pulses 
emitted by the multibeam is at moderately high frequencies, centered at 
12 kHz. The beam is narrow (approximately 2[deg]) in fore-aft extent 
and wide (approximately 130[deg]) in the cross-track extent. Any given 
mammal at depth near the trackline would be in the main beam for only a 
fraction of a second. Therefore, marine mammals that encounter the 
SeaBeam 2112 at close range 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. Similarly, Kremser et al. (2005) noted that the probability of 
a cetacean swimming through the area of exposure when a multibeam sonar 
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 
be subjected to sound levels that could cause TTS.
    Navy sonars that have been linked to avoidance reactions and 
stranding of cetaceans (1) generally are more powerful than the SeaBeam 
2112 sonar, (2) have a longer pulse duration, (3) are directed close to 
horizontally vs. downward for the SeaBeam 2112, and (4) have a wider 
beam width. The area of possible influence of the bathymetric sonar is 
much smaller, a narrow band oriented in the cross-track direction below 
the source vessel. Marine mammals that encounter the bathymetric sonar 
at close range are unlikely to be subjected to repeated pulses because 
of the narrow fore-aft width of the beam, and will receive only small 
amounts of pulse energy because of the short pulses. In assessing the 
possible impacts of a similar multibeam system (the 15.5 kHz Atlas 
Hydrosweep multibeam bathymetric sonar), Boebel et al. (2004) noted 
that the critical sound pressure level at which TTS may occur is 203.2 
dB re 1 microPa (rms). The critical region included an area of 43 m 
(141 ft) in depth, 46 m (151 ft) wide athwartship, and 1 m (3.3 ft) 
fore-and-aft (Boebel et al., 2004). In the more distant parts of that 
(small) critical region, only slight TTS could potentially be incurred. 
This area is included within the 160 dB isopleth for airguns, in which 
Level B Harassment is already assumed to occur when th airguns are 
operating.
    Behavioral reactions of free-ranging marine mammals to military and 
other sonars 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

[[Page 43460]]

by pilot whales (Rendell and Gordon, 1999), and the previously-
mentioned beachings by beaked whales. Also, Navy personnel have 
described observations of dolphins bow-riding adjacent to bow-mounted 
mid-frequency sonars during sonar transmissions. During exposure to a 
21-25 kHz whale-finding sonar with a source level of 215 dB re 1 
microPa m, gray whales showed slight avoidance (approximately 200 m 
(656 ft)) behavior (Frankel, 2005).
    However, all of those observations are of limited relevance to the 
present situation. Pulse durations from the Navy sonars were much 
longer than those of the bathymetric sonars to be used during this 
study, and a given mammal would have received many pulses from the 
naval sonars. During UTIG's operations, the individual pulses will be 
very short, and a given mammal would rarely receive more than one of 
the downward-directed pulses as the vessel passes by.
    Captive bottlenose dolphins and a white whale exhibited changes in 
behavior when exposed to 1 second of pulsed sounds at frequencies 
similar to those that will be emitted by the bathymetric sonar to be 
used by UTIG, 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 either duration or bandwidth as compared with those 
from a bathymetric sonar.
    We are not aware of any data on the reactions of pinnipeds to sonar 
sounds at frequencies similar to those of the multibeam sonar (12 kHz). 
Based on observed pinniped responses to other types of pulsed sounds, 
and the likely brevity of exposure to the bathymetric sonar sounds, 
pinniped reactions to the sonar sounds are expected to be limited to 
startle or otherwise brief responses of no lasting consequence to the 
animals.
Sub-bottom Profiler Signals
    A Knudsen 320BR sub-bottom profiler will be operated from the 
source vessel at nearly all times during the planned study. The Knudsen 
320BR produces sound pulses with lengths of up to 24 ms every 0.5 to 
approximately 8 s, depending on water depth. The energy in the sound 
pulses emitted by this sub-bottom profiler is at mid- to moderately 
high frequency, depending on whether the 3.5 or 12 kHz transducer is 
operating. The conical beamwidth is either 26[deg], for the 3.5 kHz 
transducer, or 30[deg], for the 12 kHz transducer, and is directed 
downward.
    Source levels for the Knudsen 320 operating at 3.5 and 12 kHz have 
been measured as a maximum of 221 and 215 dB re 1 Pa m, respectively. 
Received levels would diminish rapidly with increasing depth. Assuming 
circular spreading, received level directly below the transducer(s) 
would diminish to 180 dB re 1 microPa at distances of about