Small Takes of Marine Mammals Incidental to Specified Activities; Open-water Marine Survey Program in the Chukchi Sea, Alaska, During 2009-2010, 26217-26234 [E9-12659]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 74, Number 103 (Monday, June 1, 2009)]
[Notices]
[Pages 26217-26234]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E9-12659]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XP00


Small Takes of Marine Mammals Incidental to Specified Activities; 
Open-water Marine Survey Program in the Chukchi Sea, Alaska, During 
2009-2010

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 Shell Offshore Inc. and 
Shell Gulf of Mexico Inc., collectively known as Shell, for an 
Incidental Harassment Authorization (IHA) to take marine mammals 
incidental to an open-water marine survey program, which includes 
shallow hazards and site

[[Page 26218]]

clearance work and strudel scour surveys, in the Chukchi Sea, Alaska. 
Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting 
comments on its proposal to issue an IHA to Shell to incidentally take, 
by harassment, small numbers of several species of marine mammals 
during the Arctic open-water seasons between August 2009, and July, 
2010, during the aforementioned activity.

DATES: Comments and information must be received no later than July 1, 
2009.

ADDRESSES: Comments on the application should be addressed to P. 
Michael Payne, Chief, Permits, Conservation and Education Division, 
Office of Protected Resources, National Marine Fisheries Service, 1315 
East-West Highway, Silver Spring, MD 20910-3225. The mailbox address 
for providing email comments is PR1.0648-XP00@noaa.gov. Comments sent 
via e-mail, including all attachments, must not exceed a 10-megabyte 
file size.
    Instructions: All comments received are a part of the public record 
and will generally be posted to https://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications without change. All Personal Identifying 
Information (for example, name, address, etc.) voluntarily submitted by 
the commenter may be publicly accessible. Do not submit Confidential 
Business Information or otherwise sensitive or protected information.
    A copy of the application containing a list of the references used 
in this document may be obtained by writing to the address specified 
above, telephoning the contact listed below (see FOR FURTHER 
INFORMATION CONTACT), or visiting the Internet at: https://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications.
    Documents cited in this notice may be viewed, by appointment, 
during regular business hours, at the aforementioned address.

FOR FURTHER INFORMATION CONTACT: Candace Nachman, Office of Protected 
Resources, NMFS, (301) 713-2289 or Brad Smith, NMFS, Alaska Region, 
(907) 271-3023.

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 small numbers 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 for incidental takings 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 (where 
relevant), 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 the authorization.

Summary of Request

    On December 15, 2008, NMFS received an application from Shell for 
the taking, by Level B harassment only, of small numbers of several 
species of marine mammals incidental to conducting an open-water marine 
survey program during the 2009/2010 Arctic open-water season in the 
Chukchi Sea. Shell plans to conduct site clearance and shallow hazards 
surveys and a strudel scour survey in the Chukchi Sea. These surveys 
are a continuation of those conducted by Shell in the Chukchi Sea in 
2008. Shell's December 2008, application also requested MMPA coverage 
for site clearance and shallow hazards surveys, an ice gouge survey, 
and a strudel scour survey in the Beaufort Sea and an ice gouge survey 
in the Chukchi Sea for the 2009/2010 season. However, in an addendum to 
the IHA application submitted to NMFS on March 10, 2009, Shell 
indicated that it has cancelled all of the planned survey programs for 
the Beaufort Sea and the ice gouge survey for the Chukchi Sea in 2009. 
Therefore, this Federal Register Notice only describes the potential 
effects of conducting site clearance and shallow hazards surveys and a 
strudel scour survey in the Chukchi Sea for the 2009/2010 open-water 
season. Shell submitted a second addendum to its application on May 19, 
2009, indicating that Shell now plans to use a 40 in\3\ airgun array 
instead of the 20 in\3\ array (see the ``Description of the Specified 
Activity'' section later in this document for more detail on the 
specifics of the project).
    Site clearance and shallow hazards surveys will evaluate the 
seafloor and shallow sub-seafloor at prospective exploration drilling 
locations, focusing on the depth to seafloor, topography, the potential 
for shallow faults or gas zones, and the presence of archaeological 
features. The types of equipment used to conduct these surveys use low 
level energy sources focused on limited areas in order to characterize 
the footprint of the seafloor and shallow sub-seafloor at prospective 
drilling locations.
    NMFS issued an IHA to Shell on August 20, 2008, to conduct its 
marine seismic survey program in the Beaufort and Chukchi Seas for the 
2008/2009 Arctic open-water season. This IHA is valid through August 
19, 2009, or until a new IHA is issued to Shell, whichever is earlier.

Description of the Specified Activity

Chukchi Site Clearance and Shallow Hazards Surveys

    Site clearance and shallow hazards surveys of potential proposed 
locations for exploration drilling will be executed as required by the 
Minerals Management Service's (MMS) regulations. These surveys gather 
data on: (1) bathymetry; (2) seabed topography and other seabed 
characteristics (e.g., boulder patches); (3) potential geohazards 
(e.g., shallow faults and shallow gas zones); and (4) the presence of 
any archeological features (e.g., shipwrecks). Site clearance and 
shallow hazards surveys can be accomplished by one vessel with acoustic 
sources. No other vessels are necessary to accomplish the proposed 
work.
    The Chukchi Sea site clearance and shallow hazards surveys will be

[[Page 26219]]

conducted on leases that were acquired in Outer Continental Shelf (OCS) 
Lease Sale 193. Site clearance surveys are confined to small specific 
areas within OCS blocks. Actual locations of site clearance and shallow 
hazards surveys have not been definitively set as of this date, 
although the surveys will occur within the Chukchi Sea marine survey 
area of OCS lease blocks shown in Figure 1 of Shell's application. 
These surveys will occur more than 113 km (70 mi) or more offshore of 
the Alaska coast. Before the commencement of operations, survey 
location information will be supplied to MMS as ancillary activities 
authorizations and provided to other interested agencies as it becomes 
available.
    Shell anticipates shooting approximately 480 km (298 mi) of survey 
lines (plus approximately 120 km (74.6 mi) of mitigation gun activity 
between survey lines) from August through October, 2009, exposing 
approximately 900 km\2\ (347.5 mi\2\) of water to sounds of 160 dB 
(rms) or greater. The operation will be active 24 hr/day and use a 
single vessel to collect the geophysical data.
    The vessel that will be conducting the site clearance and shallow 
hazards surveys may also be used in the deployment and retrieval of 
underwater Ocean Bottom Hydrophones (OBHs) as described in the Marine 
Mammal Monitoring and Mitigation Plan (4MP) in Attachment A of Shell's 
application and also later in this document. These OBHs are anchored 
underwater buoys that record marine mammal vocalizations and other 
underwater sounds.
    These surveys are confined to small specific areas within OCS 
blocks. At this time, Shell has indicated that the R/V Norseman II will 
be used to conduct the activity. The R/V Norseman II is a diesel 
powered vessel, 35.05 m (115 ft) long, 8.66 m (28.4 ft) wide, with a 
4.08 m (13.4 ft) draft. In the event the R/V Norseman II is 
unavailable, Shell would utilize a similar vessel to conduct the 
activities.
    It is proposed that the following acoustic instrumentation, or 
something similar, will be used: (1) dual-frequency side scan sonar (2-
7 kHz or 8-23 kHz), or similar; (2) single beam Echo Sounder (33-210 
kHz), or similar; (3) multibeam Echo Sounder (200 kHz), or similar; (4) 
high resolution multi-channel two-dimensional (2D) system, 40 in\3\ (4 
x 10) airgun array (0-150 Hz), or similar; (5) shallow sub-bottom 
profiler (SBP; 1-12 kHz), or similar; and (6) medium penetration SBP 
(400-800 Hz), or similar.
    This activity is proposed to occur during August-October 2009, and, 
as proposed, the total program will last a maximum of 50 days of active 
data acquisition, excluding downtime due to weather and other 
unforeseen delays. This vessel may also be used to perform other 
activities, such as deploying and retrieving the OBHs. The time for 
deploying and retrieving the OBHs is not included in the 50-day 
estimate.

Chukchi Strudel Scour Survey

    During the early melt, the rivers begin to flow and discharge water 
over the coastal sea ice near the river deltas. That water rushes down 
holes in the ice (``strudels'') and scours the seafloor. These 
erosional areas are called ``strudel scours''. Information on these 
features is required for prospective pipeline planning. Two proposed 
activities are required to gather this information: aerial survey via 
helicopter overflights during the melt to locate the strudels and 
strudel scour marine surveys to gather bathymetric data. The 
overflights investigate possible sources of overflood water and will 
survey local streams that discharge in the vicinity of potential 
pipeline shore crossings. These helicopter overflights will occur 
during mid-May/early June 2010 and, weather permitting, should take no 
more than four days. There are no planned landings during these 
overflights other than at local airports. Areas that have strudel scour 
identified during the aerial survey will be verified and surveyed with 
a marine vessel after the breakup of nearshore ice. This proposed 
activity, i.e., marine surveys to gather bathymetric data, is not 
anticipated to take more than 10 days to conduct, excluding downtime 
due to weather and other unforeseen delays. It is anticipated to occur 
in July through mid-August 2010. This is a daylight only operation. The 
specific locations for pipeline shore crossings have not yet been 
identified. This vessel will use the following equipment: multi-beam 
bathymetric sonar, or similar; side-scan sonar system, or similar; and 
single beam bathymetric sonar, or similar.
    The vessel has not been contracted; however, it is anticipated that 
it will be the diesel-powered R/V Annika Marie which has been utilized 
from 2006-2008 and measures 13.1 m (43 ft) long, or similar vessel. 
Only one vessel is needed to complete the survey, and the acoustic 
sources will be deployed from that vessel.

Marine Mammals Affected by the Activity

    Marine mammals that occur in the proposed survey areas belong to 
three taxonomic groups: (1) odontocetes (toothed cetaceans), (2) 
mysticetes (baleen whales), and (3) carnivora (pinnipeds and polar 
bears). Cetaceans and pinnipeds (except walrus) are the subject of this 
IHA request to NMFS. In the U.S., the walrus and polar bear are managed 
by the U.S. Fish and Wildlife Service (USFWS). A separate permit 
application for this survey has been submitted to USFWS for incidental 
``takes'' specific to walruses and polar bears, and these species are 
not discussed further in Shell's application or this Federal Register 
Notice.
    Marine mammal species under the jurisdiction of NMFS which are 
known to or may occur in the open-water marine survey area of the 
Chukchi Sea include eight cetacean species and four species of 
pinnipeds (see Table 4-1 in Shell's application). Three of these 
species, the bowhead, humpback and fin whales, are listed as 
``endangered'' under the Endangered Species Act (ESA). The bowhead 
whale is more common in the survey area than other endangered species. 
Based on a small number of sightings, the fin whale is unlikely to be 
encountered along the planned trackline in the Chukchi Sea. Humpback 
whales normally are not found in the Chukchi Sea; however, several 
humpback sightings were recorded during vessel-based surveys in the 
Chukchi Sea in 2007 (Reiser et al., 2008).
    The marine mammal species under NMFS jurisdiction that are most 
likely to occur in the survey area include four cetacean species 
(beluga, bowhead, and gray whales and harbor porpoise), and three 
pinniped species (ringed, bearded, and spotted seals). Most encounters 
are likely to occur in nearshore shelf habitats or along the ice edge. 
Animal densities are generally expected to be lower in deep water and 
at locations far-offshore. The marine mammal species that is likely to 
be encountered most widely (in space and time) throughout the survey 
period is the ringed seal. Encounters with bowhead and gray whales are 
expected to be limited to particular regions and seasons, as discussed 
in Shell's application.
    Four additional cetacean species and one pinniped species-the 
killer, minke, humpback, and fin whales and ribbon seals-could occur in 
the project area, but each of these species is uncommon or rare in the 
survey area and relatively few encounters with these species are 
expected during the open-water marine survey program. Descriptions of 
the biology, distribution, and population status of the marine mammal 
species under NMFS' jurisdiction can be found in Shell's application 
and the NMFS

[[Page 26220]]

Stock Assessment Reports (SARS). The Alaska SAR is available at: https://www.nmfs.noaa.gov/pr/pdfs/sars/ak2008.pdf. Please refer to those 
documents for information on these species.

Potential Effects of Survey Activities on Marine Mammals

    The only anticipated impacts to marine mammals associated with 
Shell's proposed activities (primarily resulting from noise 
propagation) are from vessel movements and airgun operations. Aircraft 
may provide a potential secondary source of sound. The physical 
presence of vessels and aircraft could also potentially lead to non-
acoustic effects on marine mammals involving visual or other cues.
    The effects of sounds from airguns might include one or more of the 
following: tolerance, masking of natural sounds, behavioral 
disturbance, and temporary or permanent hearing impairment or non-
auditory effects (Richardson et al., 1995). As outlined in previous 
NMFS documents, the effects of noise on marine mammals are highly 
variable, and can be categorized as follows (based on Richardson et 
al., 1995):
    (1) The noise may be too weak to be heard at the location of the 
animal (i.e., lower than the prevailing ambient noise level, the 
hearing threshold of the animal at relevant frequencies, or both);
    (2) The noise may be audible but not strong enough to elicit any 
overt behavioral response;
    (3) The noise may elicit reactions of variable conspicuousness and 
variable relevance to the well being of the marine mammal; these can 
range from temporary alert responses to active avoidance reactions such 
as vacating an area at least until the noise event ceases;
    (4) Upon repeated exposure, a marine mammal may exhibit diminishing 
responsiveness (habituation), or disturbance effects may persist; the 
latter is most likely with sounds that are highly variable in 
characteristics, infrequent, and unpredictable in occurrence, and 
associated with situations that a marine mammal perceives as a threat;
    (5) Any anthropogenic noise that is strong enough to be heard has 
the potential to reduce (mask) the ability of a marine mammal to hear 
natural sounds at similar frequencies, including calls from 
conspecifics, and underwater environmental sounds such as surf noise;
    (6) If mammals remain in an area because it is important for 
feeding, breeding, or some other biologically important purpose even 
though there is chronic exposure to noise, it is possible that there 
could be noise-induced physiological stress; this might in turn have 
negative effects on the well-being or reproduction of the animals 
involved; and
    (7) Very strong sounds have the potential to cause temporary or 
permanent reduction in hearing sensitivity. In terrestrial mammals, and 
presumably marine mammals, received sound levels must far exceed the 
animal's hearing threshold for there to be any temporary threshold 
shift (TTS) in its hearing ability. For transient sounds, the sound 
level necessary to cause TTS is inversely related to the duration of 
the sound. Received sound levels must be even higher for there to be 
risk of permanent hearing impairment. In addition, intense acoustic or 
explosive events may cause trauma to tissues associated with organs 
vital for hearing, sound production, respiration and other functions. 
This trauma may include minor to severe hemorrhage.

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. 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 and small odontocetes seem to be more tolerant of 
exposure to airgun pulses than baleen whales.

Masking

    Masking effects of pulsed sounds will be limited relative to 
continuous sound sources. Bowhead whales are known to continue calling 
in the presence of marine survey sounds, and their calls can be heard 
between sound pulses, although at reduced rates (Greene et al., 1999; 
Richardson et al., 1986). Masking effects are expected to be minimal to 
nonexistent in the case of belugas given that sounds important to that 
species are predominantly at much higher frequencies than are airgun 
sounds.

Behavioral Effects

    Any impacts to marine mammals associated with sound propagation 
from vessel movements and survey operations would be non-lethal, 
temporary, and, at most, may result in short-term displacement of 
whales and seals from within the ensonified zones produced by such 
sound sources. The following discussion of potential behavioral 
deflection of whales or seals pertains to observations of behavior 
during relatively large scale seismic programs, such as deep 3D seismic 
sound sources. As Shell's planned 2009/2010 open-water marine survey 
program in the Chukchi Sea only includes small-scale sound sources used 
to perform site clearance and shallow hazards and strudel scour 
surveys, NMFS anticipates any effects to marine mammals to be similar 
to or less than those described next.
    Any impacts on the whale and seal populations in the vicinity of 
Shell's Chukchi Sea operations are expected to be non-lethal, short-
term, and transitory in nature arising from the temporary displacement 
of individuals or small groups from locations they may occupy at the 
time they are exposed to sounds between 160 dB to 190 dB (rms) received 
levels. In the case of migrating bowhead whales, displacement may take 
the form of deflection from their swim path away from (seaward of) 
received sound levels lower than 160 dB (rms; Richardson et al., 1999). 
While it is not presently known at what distance after passing the 
sound source bowhead whales return to their previous migration route, 
any deflection is expected to be only temporary and does not appear to 
adversely impact the whales or materially affect their successful 
completion of the migration to the winter calving grounds.
    Results from the 1996-1998 BP and Western Geophysical seismic 
monitoring programs in the Beaufort Sea indicate that most fall 
migrating bowhead whales deflected seaward to avoid an area within 
about 20 km (12.4 mi) of an active nearshore seismic operation, with 
the exception of a few close sightings when there was an island or very 
shallow water between the seismic operations and the whales (Miller et 
al., 1998, 1999). The available data do not provide an unequivocal 
estimate of the distance (and received sound levels) at which 
approaching bowheads begin to deflect, but this may be on the order of 
35 km (21.7 mi). Any deflection as a result of being exposed to seismic 
operations would be temporary and would not adversely impact the whales 
or materially affect

[[Page 26221]]

the whales' successful completion of the migration to winter calving 
grounds.
    When the received levels of sound exceed some threshold, cetaceans 
are expected to exhibit behavioral disturbance reactions. The levels, 
frequencies, and types of sound that will elicit a response vary 
between and within species, individuals, locations, and seasons. 
Behavioral changes may be subtle alterations in surface, respiration, 
and dive cycles. More conspicuous responses include changes in activity 
or aerial displays, movement away from the sound source, or complete 
avoidance of the area. The reaction threshold and degree of response 
also are related to the activity of the animal at the time of the 
disturbance. Whales engaged in active behaviors, such as feeding, 
socializing, or mating, appear less likely than resting animals to 
exhibit overt behavioral reactions, unless the disturbance is perceived 
as directly threatening.

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. Currently, NMFS' practice regarding exposure of 
marine mammals to high-level sounds is that cetaceans and pinnipeds 
should not be exposed to impulsive sound pressure levels (SPLs) greater 
than 180 and 190 dB re 1 microPa (rms), respectively (NMFS, 2000). 
Those criteria have been used in defining the safety (shutdown) radii 
planned for the proposed survey activities. However, those criteria 
were established before there were any data on the minimum received 
levels of sounds necessary to cause temporary auditory impairment in 
marine mammals. The precautionary nature of these criteria are 
summarized here:
     The 180 dB criterion for cetaceans is precautionary (i.e., 
lower than necessary to avoid TTS, let alone permanent auditory injury, 
at least for belugas and delphinids) as it was established prior to 
empirical research on marine mammals that now indicate that permanent 
auditory injury would not occur until significantly higher SPLs were 
encountered.
     The minimum sound level necessary to cause permanent 
hearing impairment is higher, by a variable and generally unknown 
amount, than the level that induces 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.
    Several aspects of the planned monitoring and mitigation measures 
for this project are designed to detect marine mammals occurring near 
the airguns to avoid exposing them to sound pulses that might cause 
hearing impairment. 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) prevent 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. 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 proposed project area. It is unlikely that 
such effects would occur during Shell's proposed surveys given the 
brief duration of exposure and the planned monitoring and mitigation 
measures described later in this document. The following sections 
discuss the possibilities of TTS, permanent threshold shift (PTS), and 
non-auditory physical effects in more detail.
    (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.
    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). Given the 
available data, the received 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 sound exposure level [SEL]) in order 
to produce brief, mild TTS. Exposure to several strong seismic pulses 
that each have received levels near 175-180 dB SEL 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. For 
Shell's proposed survey activities, the distance at which the received 
energy level (per pulse) would be expected to be [gteqt]175-180 dB SEL 
is the distance to the 190 dB re 1 microPa (rms) isopleth (given that 
the rms level is approximately 10-15 dB higher than the SEL value for 
the same pulse). Seismic pulses with received energy levels [gteqt]175-
180 dB SEL (190 dB re 1 microPa (rms)) are expected to be restricted to 
radius of approximately 50 m (164 ft) around the airgun array. For an 
odontocete closer to the surface, the maximum radius with [gteqt]175-
180 dB SEL or [gteqt]190 dB re 1 microPa (rms) would be smaller.
    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 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. However, no cases of TTS are expected given 
the small size of the airguns proposed to be used and the strong 
likelihood that baleen whales (especially migrating bowheads) 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, 2005; 
Ketten et al., 2001; cf. Au et al., 2000). However, more recent 
indications are that TTS onset in the most sensitive pinniped species 
studied (harbor seal, which is closely related to

[[Page 26222]]

the ringed seal) may occur at a similar SEL as in odontocetes (Kastak 
et al., 2004).
    NMFS (1995, 2000) concluded that cetaceans and pinnipeds should not 
be exposed to pulsed underwater noise at received levels exceeding, 
respectively, 180 and 190 dB re 1 microPa (rms). The established 180- 
and 190-dB re 1 microPa (rms) criteria 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 bow-riding odontocetes are exposed to airgun 
pulses much stronger than 180 dB re 1 microPa rms (Southall et al., 
2007).
    No cases of TTS are expected as a result of Shell's proposed 
activities given the small size of the source, the strong likelihood 
that baleen whales (especially migrating bowheads) would avoid the 
approaching airguns (or vessel) before being exposed to levels high 
enough for there to be any possibility of TTS, and the mitigation 
measures proposed to be implemented during the survey described later 
in this document.
    (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 empirical evidence that exposure to pulses of airgun 
sound can cause PTS in any marine mammal, even with large arrays of 
airguns (see Southall et al., 2007). 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 is exposed to the strong sound pulses with very rapid 
rise time.
    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 airgun sources 
planned here (i.e., an airgun array with a total discharge volume of 40 
in\3\). In the proposed project, marine mammals are unlikely to be 
exposed to received levels of seismic pulses strong enough to cause 
more than slight TTS. 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, and 
belugas as well, generally avoid the immediate area around operating 
seismic vessels. The planned monitoring and mitigation measures, 
including visual monitoring, power-downs, and shutdowns 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 an extended period such that significant 
physiological stress would develop. Only individuals swimming close to, 
parallel to, and at the same speed as the vessel would incur a number 
of high intensity sounds. The small airgun array proposed to be used by 
Shell would only have 190 and 180 dB distances of 50 and 160 m (164 and 
525 ft), respectively.
    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 or more likely to projects 
involving large airgun arrays. 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 (described later in this document) include shutdowns of the 
airguns, which will reduce any such effects that might otherwise occur.

Stranding and Mortality

    In numerous past IHA notices for seismic surveys, commenters have 
referenced two stranding events allegedly associated with seismic 
activities, one off Baja California and a second off Brazil. NMFS has 
addressed this concern several times, and, without new information, 
does not believe that this issue warrants further discussion. For 
information relevant to strandings of marine mammals, readers are 
encouraged to review NMFS' response to comments on this matter found in 
69 FR 74905 (December 14, 2004), 71 FR 43112 (July 31, 2006), 71 FR 
50027 (August 24, 2006), and 71 FR 49418 (August 23, 2006). In 
addition, a June, 2008, stranding of 30-40 melon-headed whales off 
Madagascar that appears to be associated with seismic surveys is 
currently under investigation. One report indicates that the stranding 
began prior to seismic surveys starting.
    It should be noted that strandings have not been recorded for 
marine mammal species in the Beaufort and Chukchi seas. NMFS notes that 
in the Beaufort Sea, aerial surveys have been conducted by MMS and 
industry during periods of industrial activity (and by MMS during times 
with no activity). No strandings or marine mammals in distress have 
been observed during these surveys and none have been reported by North 
Slope Borough inhabitants. Additionally, if bowhead and gray whales 
react to sounds at very low levels and therefore move away from the 
source and outside of the safety radii, then strandings would be 
unlikely to occur in the Arctic Ocean since a reaction or physical 
impact that could potentially lead to serious injury or mortality would 
not likely occur. As a result, NMFS does not expect any marine mammals 
will incur serious injury or mortality in the Arctic Ocean or strand as 
a result of the proposed survey.

Possible Effects from Sonar Equipment

    While the sonar equipment proposed to be used for this project 
generates high sound energy, the equipment operates at frequencies 
(>100 kHz) beyond the effective hearing range of most marine mammals 
likely to be encountered

[[Page 26223]]

during the proposed activities (Richardson et al., 1995). The equipment 
proposed for the seismic profiling operate at a frequency range and 
sound level that could affect marine mammal behavior if they occur 
within a relatively close distance to the sound source (Richardson et 
al., 1995). However, given the direct downward beam pattern of these 
sonar systems coupled with the high-frequency characteristics of the 
signals, the horizontal received levels of 180 and 190 dB re 1 microPa 
(rms) would be much smaller when compared to those from the low-
frequency airguns with similar source levels. Therefore, NMFS believes 
that effects of signals from sonar equipment to marine mammals will be 
negligible.

Estimated Take of Marine Mammals

    The anticipated harassments from the activities described above may 
involve temporary changes in behavior. There is no evidence that the 
planned activities could result in serious injury or mortality, for 
example due to collisions with vessels or strandings. Disturbance 
reactions, such as avoidance, are very likely to occur amongst marine 
mammals in the vicinity of the source vessel. The mitigation and 
monitoring measures proposed to be implemented (described later in this 
document) during this survey are based on Level B harassment criteria 
and will minimize any potential risk of injury.
    The sections below describe methods to estimate ``take by 
harassment'' and present estimates of the numbers of marine mammals 
that might be affected during the proposed site clearance and shallow 
hazards program in the Chukchi Sea. The estimates are based on data 
obtained during marine mammal surveys in and near the proposed survey 
area and on estimates of the sizes of the areas where effects could 
potentially occur. In some cases, these estimates were made from data 
collected in regions, habitats, or seasons that differ from those in 
the proposed survey areas. Adjustments to reported population or 
density estimates were made to account for these differences insofar as 
possible.
    Although several systematic surveys of marine mammals have been 
conducted in the southern Beaufort Sea, few data (systematic or 
otherwise) are available on the distribution and numbers of marine 
mammals in the Chukchi Sea beyond the 200 m (656 ft) bathymetry 
contour. The main sources of distributional and numerical data used in 
deriving the estimates are described below and in Shell's application. 
While there is some uncertainty related to the use of regional 
population densities for applications that are local in focus, these 
estimates are based on the best available scientific data and 
represents standard practice.

Marine Mammal Density Estimates

    This section provides estimates of the number of individuals 
potentially exposed to sound levels at or above 160 dB re 1 microPa 
(rms). The estimates are based on a consideration of the number of 
marine mammals that might be disturbed appreciably by operations in the 
Chukchi Sea.
    For the Chukchi Sea, cetacean densities during the summer (July-
August) were estimated from effort and sightings data in Moore et al. 
(2000b) while pinniped densities were estimated from Bengtson et al. 
(2005). Because few data are available on the densities of marine 
mammals other than large cetaceans in the Chukchi Sea in the fall 
(September-October), density estimates from the summer period have been 
adjusted to reflect the expected ratio of summer-to-fall densities 
based on the natural history characteristic of each species. 
Alternatively, some densities from data collected aboard industry 
vessels in 2006 and 2007 in the Chukchi Sea have been used.
    As noted above, there is some uncertainty about the 
representativeness of the data and assumptions used in the 
calculations. To provide some allowance for the uncertainties, 
``maximum estimates'' as well as ``average estimates'' of the numbers 
of marine mammals potentially affected have been derived and provided 
by Shell in their application. For a few marine mammal species, several 
density estimates were available, and in those cases, the average and 
maximum estimates were calculated from the survey data. In other cases, 
only one, or no applicable estimate was available so correction factors 
were used to arrive at ``average'' and ``maximum'' estimates. These are 
described in detail in Shell's application and the following 
subsections. Except where noted, the ``maximum'' estimates have been 
calculated as twice the ``average'' estimates. The densities presented 
are believed to be similar to, or in most cases higher than, the 
densities that will actually be encountered during the survey.
    Detectability bias, quantified in part by [f(0)], is associated 
with diminishing sightability with increasing lateral distance from the 
survey trackline. Availability bias [g(0)] refers to the fact that 
there is less than 100 percent probability of sighting an animal that 
is present along the survey trackline. These correction factors were 
applied to the data from Moore et al. (2000b) and were already included 
in data provided by Richardson and Thompson (2002) on beluga and 
bowhead whales, and where possible were applied to the available data 
for other species.
    Estimated densities of marine mammals in the Chukchi Sea during the 
``summer'' (July and August) site clearance and shallow hazards survey 
are presented in Table 6-1 of Shell's application. Densities of marine 
mammals estimated for the ``fall'' period of Shell's proposed 
activities in the Chukchi Sea (September and possibly October) are 
presented in Table 6-2 of the application. Both ``average'' and 
``maximum'' densities are provided in the tables. Unless otherwise 
noted by Shell in the application, maximum densities are twice the 
average densities. However, since Shell did not provide a rationale 
regarding the maximum estimate, NMFS has decided that the average 
density data of marine mammal populations will be used to calculate 
estimated take numbers because these numbers are based on surveys and 
monitoring of marine mammals in the vicinity of the proposed project 
area. NMFS only used the ``maximum'' estimates for marine mammal 
species that are considered rare in the project area and for which 
little to no density information exists (i.e., killer, fin, humpback, 
and minke whales and ringed seals).
(1) Cetaceans
    Nine species of cetaceans are known to occur in the Chukchi Sea 
project area. Only four of these (bowhead, beluga, and gray whales and 
harbor porpoise) are expected to be encountered in meaningful numbers 
during the proposed survey. Three of the nine species (bowhead, fin, 
and humpback whales) are listed as endangered under the ESA.
    Beluga Whales - Summer densities of beluga whales in offshore 
waters are expected to be very low. Aerial surveys have recorded very 
few belugas in the offshore Chukchi Sea during the summer months (Moore 
et al., 2000b). Additionally, no belugas were observed during more than 
42,000 km (26,100 mi) of useable visual effort from industry vessels 
operating in the Chukchi Sea in 2006 and 2007 (Ireland et al., 2007a,b; 
Patterson et al., 2007; Reiser et al., 2008). Shallow hazards and site 
clearance survey activities in 2009 will largely be restricted to open-
water areas as were the 2006 and 2007 surveys. Expected densities have 
been calculated from data in Moore et al. (2000b; see Table 6-1 in 
Shell's application).

[[Page 26224]]

    In the fall, beluga whale densities in the Chukchi Sea are expected 
to be higher than in the summer because individuals of the Beaufort Sea 
stock will be migrating south to their wintering grounds in the Bering 
Sea (Angliss and Outlaw, 2008). Densities are assumed to be similar in 
open-water and ice-margin areas although they are probably somewhat 
higher along the edge of the pack ice than in open-water areas where 
shallow hazards and site clearance surveys will be conducted. Densities 
derived from survey results in the northern Chukchi Sea in Moore et al. 
(2000b) were used as the average density for open-water and ice-margin 
fall estimates (see Table 6-2 in Shell's application).
    Bowhead Whales - By July, most bowhead whales are northeast of the 
Chukchi Sea, within or migrating toward their summer feeding grounds in 
the eastern Beaufort Sea resulting in low density estimates for the 
Chukchi Sea (Moore et al., 2000b). The summer estimate in the Chukchi 
Sea was calculated by assuming there was one bowhead sighting during 
the 10,684 km (6,639 mi) of survey effort in the Chukchi Sea during the 
summer months reported in Moore et al. (2000b), although, no bowheads 
were actually observed during those surveys. During the autumn, bowhead 
whales that summered in the Beaufort Sea and Amundsen Gulf are 
migrating west and south to their wintering grounds in the Bering Sea 
making it more likely that bowheads will be encountered in the Chukchi 
Sea. However, a tagging study of two bowhead whales from 2006 showed 
that both whales occurred together along the northern Chukotka coast in 
November of that year, indicating that perhaps they traveled through 
the northern Chukchi Sea to reach Russian waters (Quakenbush, 2007). A 
correction factor of \x\0.05 has been used to adjust the observed 
autumn densities from the Beaufort Sea (Richardson and Thomson, 2002) 
to estimated densities in the Chukchi Sea, for the following reasons: 
(1) the migration corridor is narrower in the Beaufort Sea where 
available data have been obtained; (2) bowheads sometimes linger to 
feed for extended periods in the Beaufort Sea but extended feeding has 
not been documented in the central and eastern Chukchi Sea in autumn; 
and (3) most bowheads will travel through the Chukchi Sea north of the 
shallow hazards and site clearance survey area after activities are 
expected to be completed in 2009.
    Gray Whales - Gray whale densities were estimated from summer 
aerial surveys by Moore et al. (2000b). Moore et al. (2000b) found 
large summer concentrations of gray whales off the Seward Peninsula, 
far to the south of Shell's planned open-water marine surveys. The 
distribution of gray whales in the proposed survey area was scattered 
and limited to nearshore areas where most whales were observed in water 
less than 35 m (115 ft) deep (Moore et al., 2000b). A density 
calculated from effort and sightings in Moore et al. (2000b) in water 
greater than 35 m (115 ft) in depth was used as the average estimate 
for the Chukchi Sea during the summer period. In the autumn, gray 
whales may be dispersed more widely through the northern Chukchi Sea 
(in the area of the survey), and densities are expected to be slightly 
higher. A density calculated from effort and sightings in water greater 
than 35 m (115 ft) deep during autumn in Moore et al. (2000b) was used 
as the average estimate for the Chukchi Sea during the fall period.
    Harbor Porpoise - Harbor porpoise densities were estimated from 
industry data collected during 2006 activities in the Chukchi Sea. 
Prior to 2006, no reliable estimates were available for the Chukchi 
Sea, and harbor porpoise presence was expected to be very low and 
limited to nearshore regions. Observers on industry vessels in 2006, 
however, commonly recorded sightings throughout the Chukchi Sea during 
the summer and early autumn months. A density estimate from these data 
has been used for the summer period. No sightings were recorded during 
the majority of the fall period, so minimal values have been used for 
that time period.
    The remaining four cetacean species that could be encountered in 
the Chukchi Sea during Shell's proposed open-water marine survey 
include the humpback, killer, minke, and fin whales. Although there is 
evidence of the occasional occurrence of these species in the Chukchi 
Sea, it is unlikely that individuals will be encountered during the 
proposed survey. George and Suydam (1998) reported killer whales, 
Brueggeman et al. (1990) reported one minke whale, Suydam and George 
(1992) and Ireland et al. (2008) reported harbor porpoise, and Gambell 
(1985) recorded the northern extent of fin whales to be in the Chukchi 
Sea. Small numbers of minke and humpback whales were observed during 
industry activities in 2006 and 2007 (Ireland et al., 2008).
(2) Pinnipeds
    Four species of pinnipeds may be encountered in the Chukchi Sea 
area of Shell's proposed shallow hazards and site clearance program: 
ringed, bearded, spotted, and ribbon seals. Each of these species, 
except the spotted seal, is associated with both the ice margin and the 
nearshore area. The ice margin is considered preferred habitat (as 
compared to the nearshore areas) during most seasons. Spotted seals are 
often considered to be predominantly a coastal species except in the 
spring when they may be found in the southern margin of the retreating 
sea ice, before they move to shore. However, satellite tagging has 
shown that they sometimes undertake long excursions into offshore 
waters, as far as 120 km (74.6 mi) off the Alaskan coast in the eastern 
Chukchi Sea, during summer (Lowry et al., 1994, 1998). Ribbon seals 
have been reported in very small numbers within the Chukchi Sea by 
observers on industry vessels (Ireland et al., 2007a; Patterson et al., 
2007) so minimal values have been used for expected densities.
    Ringed and Bearded Seals - For ringed and bearded seals both 
``average'' and ``maximum'' summer densities are available in Bengtson 
et al. (2005) from spring surveys in the offshore pack ice zone of the 
northern Chukchi Sea (see Tables 6-1 and 6-2 in Shell's application). 
The ringed seal density estimates calculated from data collected during 
2006 and 2007 industry operations were 0.262 and 0.041seals/km\2\, 
respectively (Jankowski et al., 2007; Reiser et al., 2008), and are 
lower than those estimated by Bengtson et al. (2005). The fall density 
of ringed seals in the Chukchi Sea has been estimated as two-thirds the 
summer densities because at that time of year, ringed seals reoccupy 
nearshore fast ice areas as the fast ice forms.
    Spotted Seals - Very little information on spotted seal densities 
in offshore areas of the Chukchi Sea is available because of the 
difficulty in estimating their density when at sea. Spotted seal 
densities were estimated by multiplying the bearded seal density from 
Bengtson et al. (2005) by 0.2 based on the ratio of abundance estimates 
of spotted seal to bearded seal.

Exposure Calculations of Marine Mammals

    Numbers of marine mammals that might be present and potentially 
disturbed as a result of the site clearance and shallow hazards survey 
are estimated below based on available data about mammal distribution 
and densities at different locations and times of the year, as 
described in the previous subsections. The proposed survey would take 
place in the Chukchi Sea over two different seasons (i.e., half in the 
summer, August, and half in the fall,

[[Page 26225]]

September). The estimates of marine mammal densities have therefore 
been separated both spatially and temporally in an attempt to represent 
the distribution of animals expected to be encountered over the 
duration of the survey.
    The number of individuals of each species potentially exposed to 
received sound levels at or above 160 dB re 1 microPa (rms) within the 
survey region, time period, and habitat zone was estimated by 
multiplying:
     The expected species density (as provided in Tables 6-1 
and 6-2 of Shell's application); by
     The anticipated area to be ensonified to the specified 
level in the survey region (900 km\2\), time period, and habitat zone 
to which that density applies.
    The numbers of potential individuals exposed were then summed for 
each species across the survey regions, seasons, and habitat zones. 
Some of the animals estimated to be exposed, particularly migrating 
bowhead whales, might show avoidance reactions before being exposed to 
160 dB re 1 microPa (rms). Thus, these calculations actually estimate 
the number of individuals potentially exposed to sound at or above 160 
dB (rms) that would occur if there were no avoidance of the area 
ensonified to that level.
    The area of water potentially exposed to received levels at or 
above 160 dB (rms) by the proposed operations was calculated by 
multiplying the planned trackline distance by the cross-track distance 
of the sound propagation measured during previous field seasons. For 
site clearance and shallow hazards surveys in 2008 in the Chukchi Sea, 
the 160 dB radius from the Cape Flattery's four 10 in\3\ airguns 
measured in 2008 was 1,400 m (0.87 mi), and the single 10 in\3\ airgun 
was 440 m (0.27 mi).
    Closely spaced survey lines and large cross-track distances of the 
160 dB radii can result in repeated exposure of the same area of water. 
Excessive amounts of repeated exposure can lead to overestimation of 
the number of animals potentially exposed through double counting. 
However, the relatively short cross-track distances of the 160 dB radii 
associated with the site clearance and shallow hazards surveys result 
in little overlap of exposed waters during the survey, so multiple 
exposures due to overlap of ensonified areas have not been removed from 
the area calculations.
    Shallow hazards and site clearance surveys in the Chukchi Sea are 
planned to occur along approximately 480 km (298 mi) of survey lines 
(plus approximately 120 km (74.6 mi) of mitigation gun activity between 
survey lines) from August-September exposing approximately 900 km\2\ 
(347.5 mi\2\) of water to sounds at or above 160 dB (rms).
    Density estimates in the Chukchi Sea have been derived for two time 
periods, the summer period (August) and the fall period (September). 
Animal densities encountered in the Chukchi Sea during both of these 
time periods will further depend on the habitat zone within which the 
source vessel is operating: (1) open-water; or (2) ice margin. The 
survey vessel is not an icebreaker and cannot tow survey equipment 
through pack ice. Under this assumption, densities of marine mammals 
expected to be observed in or near ice margin areas have been applied 
to 10 percent of the proposed survey trackline. Densities of marine 
mammals expected to occur in open-water areas have been applied to the 
remaining 90 percent of the survey trackline.
    Approximately half of the proposed Chukchi Sea site clearance and 
shallow hazards survey is planned to be completed in August, so the 
summer density estimates have been applied to 50 percent of the 
trackline falling within each habitat zone. The other half of the 
trackline is planned to be surveyed in September, so the fall marine 
mammal densities have also been applied to 50 percent of the trackline 
in each habitat zone.
    Based on the operational plans and marine mammal densities 
described above, the estimates of marine mammals potentially exposed to 
sounds at or above 160 dB (rms) in the Chukchi Sea are presented in 
Table 6-7 of Addendum 2 to Shell's application. A discussion of the 
number of potential exposures is summarized by species in the following 
subsections.
(1) Cetaceans
    Based on density estimates, one ESA-listed cetacean species (the 
bowhead whale) is expected to be exposed to received sound levels at or 
above 160 dB (rms) unless bowheads avoid the survey vessel before the 
received levels reach 160 dB. Migrating bowheads are likely to avoid 
the survey vessel, though many of the bowheads engaged in other 
activities, particularly feeding and socializing may not. Using average 
density estimates, Shell estimates that one bowhead whale may 
potentially be exposed to sounds at or above 160 dB (rms) in the 
Chukchi Sea project area during the site clearance and shallow hazards 
survey (see Table 6-7 of Addendum 2 to Shell's application). Two other 
cetacean species listed as endangered under the ESA that may be 
encountered in the project area (fin and humpback whales) are unlikely 
to be exposed given their low ``average'' density estimates in the 
area. However, Shell has estimated that a ``maximum'' of five humpback 
whales and five fin whales may be exposed to sound levels at or above 
160 dB (rms) during the proposed survey (see Table 6-7 in Addendum 2). 
NMFS' reasoning for using the ``maximum'' estimate for these species 
was explained earlier in this document.
    Most of the cetaceans exposed to survey sounds with received levels 
greater than or equal to 160 dB (rms) would involve mysticetes (bowhead 
and gray whales), monodontids (beluga whales), and porpoise (harbor 
porpoise). Average and maximum estimates of the number of exposures of 
cetaceans other than bowheads are beluga whale (10 and 19, 
respectively), gray whale (19 and 37, respectively), and harbor 
porpoise (6 and 11, respectively). Average estimates for the other 
cetacean species are zero (see Table 6-7 in Addendum 2 to Shell's 
application) since accurate density estimates are not possible given 
the paucity of sightings. However, maximum estimates are provided for 
these species (see Table 6-7).
    For the common species, the requested numbers are calculated as 
described previously in this document and based on the average 
densities from the data reported in the different studies mentioned 
previously.
(2) Pinnipeds
    The ringed seal is the most widespread and abundant pinniped in 
ice-covered Arctic waters, and there is a great deal of annual 
variation in population size and distribution of these marine mammals. 
Ringed seals account for the vast majority of marine mammals expected 
to be encountered and hence exposed to airgun sounds with received 
levels greater than or equal to 160 dB re 1 microPa (rms) during the 
proposed site clearance and shallow hazards survey. The average (and 
maximum) exposure estimate is that 692 (1,078) ringed seals might be 
exposed to marine survey sounds with received levels at or above 160 dB 
(rms).
    Two additional pinniped species (other than Pacific walrus) are 
expected to be encountered. They are the bearded seal (31 and 43, 
average and maximum estimates, respectively) and the spotted seal (6 
and 11, average and maximum estimates, respectively; Table 6-7 in 
Addendum 2 to Shell's application). Survey activities near spotted seal 
haulouts at Icy Cape in the Chukchi Sea will remain more than 8 km (5 
mi) from shore and be timed to minimize the

[[Page 26226]]

chance of disturbance to hauled out seals. The ribbon seal is unlikely 
to be encountered. Therefore, only a maximum estimate (5) has been 
provided for this species based on the minimal density data and 
extremely low density estimates for this species in the Chukchi Sea. 
NMFS' reasoning for using the ``maximum'' estimate for this species was 
explained earlier in this document.

Conclusions

(1) Cetaceans
    Most of the bowhead whales encountered during the summer will 
likely show overt disturbance (avoidance) if they receive airgun sounds 
with levels at or above 160 dB re 1 microPa (rms). The small airgun 
array proposed for use in this survey greatly limits the size of the 
160 dB zone around the ship (1,400 m (0.87 mi)). The use of this 
smaller airgun array will result in fewer bowhead whales being 
disturbed by the survey when compared to the use of larger airgun 
arrays.
    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 delphinds to show some limited avoidance of 
operating seismic vessels (Stone, 2003; Moulton and Miller, 2005; Holst 
et al., 2006; Stone and Tasker, 2006). Studies that have reported cases 
of small toothed whales close to the operating airguns include Duncan 
(1985), Arnold (1996), Stone (2003), and Holst et al. (2006). However, 
at least when in the Canadian Beaufort Sea in summer, belugas appear to 
be fairly responsive to seismic energy, with few being sighted within 
10-20 km (6.2-12.4 mi) of seismic vessels during aerial surveys. 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). The study conducted by Miller et 
al. (2005) was aboard a vessel conducting a 3D seismic survey, 
utilizing two identical 2,250 in\3\ airgun arrays with each array 
containing 24 guns. Since the acoustic sources proposed to be used 
during Shell's survey are significantly smaller (40 in\3\ array) than 
the ones described in the Miller et al. (2005) study, deflections of 
that magnitude are not expected. Belugas will likely occur in small 
numbers in the Chukchi Sea during the survey period and few will likely 
be affected by the survey activity.
    Taking into account the mitigation measures that are planned, 
effects on cetaceans are generally expected to be restricted to 
avoidance of a limited area around the survey operation and short-term 
changes in behavior, falling within the MMPA definition of ``Level B 
harassment''. Furthermore, the estimated numbers of animals potentially 
exposed to sound levels sufficient to cause appreciable disturbance are 
relatively low percentages of the population sizes in the Bearing-
Chukchi-Beaufort seas, as described next.
    Based on the 160 dB (rms) disturbance criterion, the best (average) 
estimates of the numbers of cetacean exposures to sounds at or above 
160 dB re 1 microPa (rms) represent varying proportions of the 
populations of each species in the Chukchi Sea and adjacent waters (cf. 
Table 6-1 in Shell's application). For species listed as endangered 
under the ESA, Shell's estimates suggest it is unlikely that fin whales 
or humpback whales will be exposed to received levels greater than or 
equal to 160 dB rms, but that approximately one bowhead may be exposed 
at this level. The latter is less than 0.01 percent of the Bering-
Chukchi-Beaufort population of greater than 13,779 individuals assuming 
3.4 percent annual population growth from the 2001 estimate of 10,545 
animals (Zeh and Punt, 2005).
    Beluga whales may be exposed to sounds produced by the airgun 
arrays during the proposed survey, and the numbers p