Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to an Exploration Drilling Program in the Chukchi Sea, AK, 25730-25757 [2010-10880]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 75, Number 88 (Friday, May 7, 2010)]
[Notices]
[Pages 25730-25757]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2010-10880]



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Part III





Department of Commerce





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National Oceanic and Atmospheric Administration



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Takes of Marine Mammals Incidental to Specified Activities; Taking 
Marine Mammals Incidental to an Exploration Drilling Program in the 
Chukchi Sea, AK; Notice

Federal Register / Vol. 75, No. 88 / Friday, May 7, 2010 / Notices

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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XW14


Takes of Marine Mammals Incidental to Specified Activities; 
Taking Marine Mammals Incidental to an Exploration Drilling Program in 
the Chukchi Sea, AK

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

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

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SUMMARY: NMFS received an application from Shell Offshore Inc. (Shell) 
for an Incidental Harassment Authorization (IHA) to take marine 
mammals, by harassment, incidental to offshore exploration drilling on 
Outer Continental Shelf (OCS) leases 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 take, by Level B 
harassment only, 12 species of marine mammals during the specified 
activity.

DATES: Comments and information must be received no later than June 7, 
2010.

ADDRESSES: Comments on the application should be addressed to Michael 
Payne, Chief, Permits, Conservation and Education Division, Office of 
Protected Resources, National Marine Fisheries Service, 1315 East-West 
Highway, Silver Spring, MD 20910. The mailbox address for providing e-
mail comments is PR1.0648-XW14@noaa.gov. NMFS is not responsible for e-
mail comments sent to addresses other than the one provided here. 
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 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 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. The following associated 
documents are also available at the same Internet address: Shell's 2010 
Exploration Drilling Communication Plan Chukchi Sea, Alaska, and 
Shell's 2010 Plan of Cooperation (POC) Camden Bay, Alaska. Documents 
cited in this notice may also 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, ext 156.

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 U.S. can apply for an authorization to 
incidentally take small numbers of marine mammals by 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.
    Except with respect to certain activities not pertinent here, the 
MMPA defines ``harassment'' as:

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

Summary of Request

    NMFS received an application on May 26, 2009, from Shell for the 
taking, by harassment, of marine mammals incidental to offshore 
exploration drilling on OCS leases in the Chukchi Sea, Alaska. NMFS 
reviewed Shell's application and identified a number of issues 
requiring further clarification. After addressing comments from NMFS, 
Shell modified its application and submitted a revised application on 
December 11, 2009. However, after some additional discussions regarding 
certain activities, NMFS determined that a second revision to the 
application was warranted. The latest revised application was submitted 
to NMFS on April 14, 2010. NMFS carefully evaluated Shell's 
application, including their analyses, and determined that the 
application is complete and that it is appropriate to make the 
necessary preliminary determinations pursuant to the MMPA. The April 
14, 2010, application is the one available for public comment (see 
ADDRESSES) and considered by NMFS for this proposed IHA.
    Shell intends to drill up to three exploration wells at five 
possible drill sites on seven leases at the prospects known as Burger, 
Crackerjack, and Southwest (SW) Shoebill on OCS leases offshore in the 
Chukchi Sea, Alaska, during the 2010 Arctic open-water season (July 
through October). Impacts to marine mammals may occur from noise 
produced by the drillship and supporting vessels and aircraft. Shell 
has requested an authorization to take 13 marine mammal species by 
Level B harassment. However, the narwhal (Monodon monoceros) is not 
expected to be found in the activity area. Therefore, NMFS is proposing 
to authorize take of 12 marine mammal species, by Level B harassment, 
incidental to Shell's offshore exploration drilling in the Chukchi Sea. 
These species include: beluga whale (Delphinapterus leucas); bowhead 
whale (Balaena mysticetus); gray whale (Eschrichtius robustus); killer 
whale (Orcinus orca); minke whale (Balaenoptera acutorostrata); fin 
whale (Balaenoptera physalus); humpback whale (Megaptera novaeangliae); 
harbor porpoise (Phocoena phocoena); bearded

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seal (Erignathus barbatus); ringed seal (Phoca hispida); spotted seal 
(P. largha); and ribbon seal (Histriophoca fasciata).

Description of the Specified Activity

    Shell plans to conduct an offshore exploration drilling program on 
U.S. Department of the Interior, Minerals Management Service (MMS) 
Alaska OCS leases located greater than 60 mi (97 km) from the Chukchi 
Sea coast during the 2010 open-water season. The leases were acquired 
during the Chukchi Sea Oil and Gas Lease Sale 193 held in February 
2008. During the 2010 drilling program, Shell plans to drill up to 
three exploration wells at five possible drill sites on seven leases at 
the prospects known as Burger, Crackerjack, and SW Shoebill. See Figure 
1-1 in Shell's application for the lease block and drill site locations 
(see ADDRESSES). All drilling is planned to be vertical.
    All of the possible Chukchi Sea offshore drill sites are located 
between 64 and 124 mi (103 and 200 km) from the Chukchi coast in water 
depths between 142 and 149 ft (43.3 and 45.4 m). Table 2-1 in Shell's 
application provides the coordinates for the drill sites (see 
ADDRESSES). Shell plans to commence drilling at the Burger prospect as 
soon as ice, weather, and other conditions allow for safe drilling 
operations. In the event ice and weather conditions prevent the 
Discoverer from reaching the Burger prospect, Shell intends to mobilize 
its exploration operations to one of the alternative drill sites in the 
SW Shoebill or Crackerjack prospects.
    The ice reinforced drillship Discoverer will be used to drill the 
wells. The Discoverer is 514 ft (156.7 m) long with a maximum height 
(above keel) of 274 ft (83.7 m). Additional rig specifications for the 
Discoverer can be found in Attachment A of Shell's application (see 
ADDRESSES). While on location at the drill sites, the Discoverer will 
be affixed to the seafloor using eight 7-ton Stevpris anchors arranged 
in a radial array.
    During the 2010 drilling season, the Discoverer will be attended by 
a minimum of seven vessels that will be used for ice-management, anchor 
handling, oil spill response (OSR), refueling, resupply, and servicing 
of the drilling operations. The ice-management vessels will consist of 
an icebreaker and an anchor handler. Table 1-2 in Shell's application 
provides a list of the support vessels that will be used during the 
drilling program, as well as information about trip frequency and 
duration for each vessel.
    Primary resupply between the drill sites and logistics facilities 
at Dutch Harbor will use a coastwise qualified offshore supply vessel. 
Some minor resupply is also planned to be conducted between the drill 
sites and Wainwright with a shallow water landing craft. An ice-capable 
OSR vessel will be dedicated to Chukchi Sea operations and remain in 
the vicinity of the drillship when drilling into liquid hydrocarbon 
zones. An OSR barge, with an associated tug, will be staged in the 
nearshore zone, and an OSR tanker will be staged to respond to a 
discharge and provide storage capability for recovered liquids, if 
necessary.
    Shell's base plan is for the ice-management vessel, the M/V 
Vladimir Ignatjuk, and the anchor handler, the M/V Nordica, or similar 
vessels, to accompany the Discoverer traveling north from Dutch Harbor 
through the Bering Strait, on or about July 1, 2010, then into the 
Chukchi Sea, before arriving on location approximately July 4. 
Exploration drilling is expected to be complete by October 31. At the 
completion of the drilling season, one or two ice-management vessels, 
along with various support vessels, such as the OSR fleet, will 
accompany the Discoverer as it travels south out of the Chukchi Sea and 
through the Bering Strait to Dutch Harbor. Subject to ice conditions, 
alternate exit routes may be considered.
    Shell plans to cease drilling on or before October 31, after which 
the Discoverer will exit the Alaskan Chukchi Sea. Shell anticipates 
that the exploration drilling program will require approximately 37 
days per well, including mudline cellar construction. Therefore, if 
Shell is able to drill three exploration wells during the 2010 open-
water season, it would require a total of 111 days. These estimates do 
not include any downtime for weather or other operational delays. Shell 
also assumes approximately 10 additional days will be needed for 
transit, drillship mobilization and mooring, drillship moves between 
locations, and drillship demobilization.
    Activities associated with the 2010 Chukchi Sea exploration 
drilling program include operation of the Discoverer, associated 
support vessels, crew change support, and resupply. The Discoverer will 
remain at the location of the designated exploration drill sites except 
when mobilizing and demobilizing to and from the Chukchi Sea, 
transiting between drill sites, and temporarily moving off location if 
it is determined ice conditions require such a move to ensure the 
safety of personnel and/or the environment in accordance with Shell's 
Ice-management Plan (IMP). The anchor handler and OSR vessels will 
remain in close proximity to the drillship during drilling operations. 
The ice-management vessel will generally be working upwind of the 
drillship from 3-25 mi (4.8-40.2 km) away. Helicopters would be used to 
provide support for crew change, provision resupply, and any search-
and-rescue operations during the drilling season.
    Shell recognizes that the drilling program is located in an area 
that is characterized by active sea ice movement, ice scouring, and 
storm surges. In anticipation of potential ice hazards that may be 
encountered, Shell has developed and will implement an IMP to ensure 
real-time ice and weather forecasting is conducted in order to identify 
conditions that might put operations at risk and will modify its 
activities accordingly. The IMP also contains ice threat classification 
levels depending on the time available to suspend drilling operations, 
secure the well, and escape from advancing hazardous ice. Real-time ice 
and weather forecasting will be available to operations personnel for 
planning purposes and to alert the fleet of impending hazardous ice and 
weather conditions. Ice and weather forecasting is provided by Shell's 
Ice and Weather Advisory Center. The center is continuously manned by 
experienced personnel, who rely on a number of data sources for ice 
forecasting and tracking, including:
     Radarsat and Envisat data--satellites with Synthetic 
Aperture Radar, providing all-weather imagery of ice conditions with 
very high resolution;
     Moderate Resolution Imaging Spectroradiometer--a satellite 
providing lower resolution visual and near infrared imagery;
     Aerial reconnaissance--provided by specially deployed 
fixed wing or rotary wing aircraft for confirmation of ice conditions 
and position;
     Reports from ice specialists on the ice-management and 
anchor handling vessels and from the ice observer on the drillship;
     Incidental ice data provided by commercial ships 
transiting the area; and
     Information from NOAA ice centers and the University of 
Colorado.
    The ice-management/anchor handling vessels would manage the ice by 
deflecting any ice floes that could affect the Discoverer when it is 
drilling and would also handle the Discoverer's anchors during 
connection to and separation from the seafloor. The ice floe frequency 
and intensity are unpredictable and could range from no

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ice to ice sufficiently dense that the fleet has insufficient capacity 
to continue operating, and the Discoverer would need to disconnect from 
its anchors and move off site. If ice is present, ice-management 
activities may be necessary in early July and towards the end of 
operations in late October, but it is not expected to be needed 
throughout the proposed drilling season. Shell has indicated that when 
ice is present at the drill site, ice disturbance will be limited to 
the minimum needed to allow drilling to continue. First-year ice will 
be the type most likely to be encountered. The ice-management vessels 
will be tasked with managing the ice so that it will flow easily around 
and past the Discoverer without building up in front of it. This type 
of ice is managed by the ice-management vessel continually moving back 
and forth across the drift line, directly up-drift of the Discoverer 
and making turns at both ends. During ice-management, the vessel's 
propeller is rotating at approximately 15-20 percent of the vessel's 
propeller rotation capacity. Ice-management occurs with slow movements 
of the vessel using lower power and therefore slower propeller rotation 
speed (i.e., lower cavitation), allowing for fewer repositions of the 
vessel, thereby reducing cavitation effects in the water. Occasionally, 
there may be multi-year ice ridges that would be managed at a much 
slower speed than that used to manage first-year ice. Shell has 
indicated that they do not have any intention of breaking ice with the 
ice-management vessels but, rather, intend to push it out of the area 
as described here. Should ice become so prevalent in the drilling area 
that it is difficult to continue operations without the breaking of 
ice, Shell has indicated that they would stop operations and move off 
site instead of breaking ice (S. Childs, Shell, 2010, pers. comm.). 
Shell has indicated that ice breaking would only be conducted if the 
ice poses an immediate safety hazard at the drill sites.
    Potential impacts to marine mammals could occur from the noise 
produced by the drillship and its support vessels and aircraft. The 
drillship produces continuous noise into the marine environment. NMFS 
currently uses a threshold of 120 dB re 1 [mu]Pa (rms) for the onset of 
Level B harassment from continuous sound sources. Sound measurements 
from the Discoverer have not previously been conducted in the Arctic or 
elsewhere; however, sounds from a similar drillship, the Northern 
Explorer II, were measured at two different times and locations in the 
Beaufort Sea (Miles et al., 1987; Greene, 1987a,b). In both cases, a 
support vessel was present in the vicinity of the drillship, thus 
providing an aggregate source level for modeling the combined drilling 
activities. The underwater received sound pressure level (SPL) in the 
20-1,000 Hz band for drilling activity by the Northern Explorer II, 
including a nearby support vessel, was 134 dB re 1 [mu]Pa (rms) at 0.1 
mi (0.2 km; Greene, 1987b). The back-propagated source levels (175 dB 
re 1 [mu]Pa at 1 m) from these measurements were used as a proxy for 
modeling the sounds likely to be produced by drilling activities from 
the Discoverer. NMFS has determined that the sound measurements for the 
Northern Explorer II constitute a good proxy for estimating sound radii 
for the Discoverer. Sound propagation measurements will be performed on 
the Discoverer in 2010 once on location near the Chukchi Sea drill 
sites. The results of those measurements will be used during the 
drilling season to implement proposed mitigation measures described 
later in this document (see the ``Proposed Mitigation'' section).
    Although there will be several support vessels in the drilling 
operations area, NMFS considers the possibility of collisions with 
marine mammals highly unlikely. Once on location, the majority of the 
support vessels will remain in the area of the drillship throughout the 
2010 drilling season and will not be making trips between the shorebase 
and the offshore vessels. Aircraft travel would be controlled by 
Federal Aviation Administration approved flight paths. Shell has agreed 
to a flight altitude of 1,500 ft (457 m; except during takeoffs and 
landings or during emergencies) to minimize impacts on marine mammals. 
As the crew change/resupply activities are considered part of normal 
vessel traffic and are not anticipated to impact marine mammals in a 
manner that would rise to the level of taking, those activities are not 
considered further in this document. Additionally, ice-management 
activities are not anticipated to impact marine mammals in a manner 
that would rise to the level of taking. This is based on the fact that 
the propeller rotation (i.e., cavitation) will be similar to that of 
vessels under normal operations and will not be used at 100 percent 
power as is the case in other situations rising to the level of taking 
(e.g., thruster use for dynamic positioning at terminals).

Description of Marine Mammals in the Area of the Specified Activity

    The Chukchi Sea supports a diverse assemblage of marine mammals, 
including: bowhead, gray, beluga, killer, minke, humpback, and fin 
whales; harbor porpoise; ringed, ribbon, spotted, and bearded seals; 
narwhals; polar bears (Ursus maritimus); and walruses (Odobenus 
rosmarus divergens; see Table 3-1 in Shell's application). The bowhead, 
humpback, and fin whales are listed as ``endangered'' under the 
Endangered Species Act (ESA) and as depleted under the MMPA. Certain 
stocks or populations of gray, beluga, and killer whales and spotted 
seals are listed as endangered or are proposed for listing under the 
ESA; however, none of those stocks or populations occur in the proposed 
activity area. Additionally, the ribbon seal is considered a ``species 
of concern'' under the ESA, and the bearded and ringed seals are 
``candidate species'' under the ESA, meaning they are currently being 
considered for listing. Both the walrus and the polar bear are managed 
by the U.S. Fish and Wildlife Service (USFWS) and are not considered 
further in this proposed IHA notice.
    Of these species, 12 are expected to occur in the area of Shell's 
proposed operations. These species include: the bowhead, gray, 
humpback, minke, fin, killer, and beluga whales; harbor porpoise; and 
the ringed, spotted, bearded, and ribbon seals. Beluga, bowhead, and 
gray whales, harbor porpoise, and ringed, bearded, and spotted seals 
are anticipated to be encountered more than the other marine mammal 
species mentioned here. The marine mammal species that is likely to be 
encountered most widely (in space and time) throughout the period of 
the proposed drilling program is the ringed seal. Encounters with 
bowhead and gray whales are expected to be limited to particular 
seasons, as discussed later in this document. Where available, Shell 
used density estimates from peer-reviewed literature in the 
application. In cases where density estimates were not readily 
available in the peer-reviewed literature, Shell used other methods to 
derive the estimates. NMFS reviewed the density estimate descriptions 
and articles from which estimates were derived and requested additional 
information to better explain the density estimates presented by Shell 
in its application. This additional information was included in the 
revised IHA application. The explanation for those derivations and the 
actual density estimates are described later in this

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document (see the ``Estimated Take by Incidental Harassment'' section).
    The narwhal occurs in Canadian waters and occasionally in the 
Alaskan Beaufort Sea and the Chukchi Sea, but it is considered 
extralimital in U.S. waters and is not expected to be encountered. 
There are scattered records of narwhal in Alaskan waters, including 
reports by subsistence hunters, where the species is considered 
extralimital (Reeves et al., 2002). Due to the rarity of this species 
in the proposed project area and the remote chance it would be affected 
by Shell's proposed Chukchi Sea drilling activities, this species is 
not discussed further in this proposed IHA notice.
    Shell's application contains information on the status, 
distribution, seasonal distribution, and abundance of each of the 
species under NMFS jurisdiction mentioned in this document. When 
reviewing the application, NMFS determined that the species 
descriptions provided by Shell correctly characterized the status, 
distribution, seasonal distribution, and abundance of each species. 
Please refer to the application for that information (see ADDRESSES). 
Additional information can also be found in the NMFS Stock Assessment 
Reports (SAR). The Alaska 2009 SAR is available at: https://www.nmfs.noaa.gov/pr/pdfs/sars/ak2009.pdf.

Brief Background on Marine Mammal Hearing

    When considering the influence of various kinds of sound on the 
marine environment, it is necessary to understand that different kinds 
of marine life are sensitive to different frequencies of sound. Based 
on available behavioral data, audiograms derived using auditory evoked 
potential techniques, anatomical modeling, and other data, Southall et 
al. (2007) designate ``functional hearing groups'' for marine mammals 
and estimate the lower and upper frequencies of functional hearing of 
the groups. The functional groups and the associated frequencies are 
indicated below (though, animals are less sensitive to sounds at the 
outer edge of their functional range and most sensitive to sounds of 
frequencies within a smaller range somewhere in the middle of their 
functional hearing range):
     Low frequency cetaceans (13 species of mysticetes): 
functional hearing is estimated to occur between approximately 7 Hz and 
22 kHz;
     Mid-frequency cetaceans (32 species of dolphins, six 
species of larger toothed whales, and 19 species of beaked and 
bottlenose whales): functional hearing is estimated to occur between 
approximately 150 Hz and 160 kHz;
     High frequency cetaceans (eight species of true porpoises, 
six species of river dolphins, Kogia, the franciscana, and four species 
of cephalorhynchids): functional hearing is estimated to occur between 
approximately 200 Hz and 180 kHz; and
     Pinnipeds in Water: functional hearing is estimated to 
occur between approximately 75 Hz and 75 kHz, with the greatest 
sensitivity between approximately 700 Hz and 20 kHz.
    As mentioned previously in this document, 12 marine mammal species 
(four pinniped and eight cetacean species) are likely to occur in the 
proposed drilling area. Of the eight cetacean species likely to occur 
in Shell's project area, five are classified as low frequency cetaceans 
(i.e., bowhead, gray, humpback, minke, and fin whales), two are 
classified as mid-frequency cetaceans (i.e., beluga and killer whales), 
and one is classified as a high-frequency cetacean (i.e., harbor 
porpoise) (Southall et al., 2007).

Potential Effects of the Specified Activity on Marine Mammals

    Potential effects of Shell's proposed drilling program in the 
Chukchi Sea on marine mammals would most likely be acoustic in nature. 
Petroleum development and associated activities introduce sound into 
the marine environment. Potential acoustic effects on marine mammals 
relate to sound produced by drilling activity, vessels, and aircraft. 
The potential effects of sound from the proposed exploratory drilling 
program might include one or more of the following: tolerance; masking 
of natural sounds; behavioral disturbance; non-auditory physical 
effects; and, at least in theory, temporary or permanent hearing 
impairment (Richardson et al., 1995a). However, for reasons discussed 
later in this document, it is unlikely that there would be any cases of 
temporary, or especially permanent, hearing impairment resulting from 
these activities. 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., 1995a):
    (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 but 
potentially for longer periods of time;
    (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 a 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.

Drilling Sounds

    Exploratory drilling will be conducted from a vessel specifically 
designed for such operations in the Arctic. Underwater sound 
propagation results from the use of generators, drilling machinery, and 
the rig itself. Received sound levels during vessel-based operations 
may fluctuate depending on the specific type of activity at a given

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time and aspect from the vessel. Underwater sound levels may also 
depend on the specific equipment in operation. Lower sound levels have 
been reported during well logging than during drilling operations 
(Greene, 1987b), and underwater sound appeared to be lower at the bow 
and stern aspects than at the beam (Greene, 1987a).
    Most drilling sounds generated from vessel-based operations occur 
at relatively low frequencies below 600 Hz although tones up to 1,850 
Hz were recorded by Greene (1987a) during drilling operations in the 
Beaufort Sea. At a range of 558 ft (170 m) the 20-1000 Hz band level 
was 122-125 dB for the drillship Explorer I. Underwater sound levels 
were slightly higher (134 dB) during drilling activity from the 
Northern Explorer II at a range of 656 ft (200 m), although tones were 
only recorded below 600 Hz. Underwater sound measurements from the 
Kulluk at 0.62 mi (1 km) were higher (143 dB) than from the other two 
vessels. Shell used the measurements from the Northern Explorer II to 
model the various sound radii (which are discussed later in this 
document) for the Discoverer. Once on location at the drill sites in 
the Chukchi Sea, Shell plans to take measurements of the Discoverer to 
quantify the absolute sound levels produced by drilling and to monitor 
their variations with time, distance, and direction from the drillship. 
Based on the similarities of the two drillships, NMFS has preliminarily 
determined that the radii produced by the Discoverer would be similar 
to those recorded for the Northern Explorer II.

Vessel Sounds

    In addition to the drillship, various types of vessels will be used 
in support of the operations, including ice-management vessels, anchor 
handlers, and oil-spill response vessels. Sounds from boats and vessels 
have been reported extensively (Greene and Moore, 1995; Blackwell and 
Greene, 2002, 2005, 2006). Numerous measurements of underwater vessel 
sound have been performed in support of recent industry activity in the 
Chukchi and Beaufort seas. Results of these measurements were reported 
in various 90-day and comprehensive reports since 2007 (e.g., Aerts et 
al., 2008; Hauser et al., 2008; Brueggeman, 2009; Ireland et al., 
2009). For example, Garner and Hannay (2009) estimated sound pressure 
levels of 100 dB at distances ranging from approximately 1.5 to 2.3 mi 
(2.4 to 3.7 km) from various types of barges. MacDonald et al. (2008) 
estimated higher underwater SPLs from the seismic vessel Gilavar of 120 
dB at approximately 13 mi (21 km) from the source, although the sound 
level was only 150 dB at 85 ft (26 m) from the vessel. Like other 
industry-generated sound, underwater sound from vessels is generally at 
relatively low frequencies.
    The primary sources of sounds from all vessel classes are propeller 
cavitation, propeller singing, and propulsion or other machinery. 
Propeller cavitation is usually the dominant noise source for vessels 
(Ross, 1976). Propeller cavitation and singing are produced outside the 
hull, whereas propulsion or other machinery noise originates inside the 
hull. There are additional sounds produced by vessel activity, such as 
pumps, generators, flow noise from water passing over the hull, and 
bubbles breaking in the wake. Icebreakers contribute greater sound 
levels during ice-breaking activities than ships of similar size during 
normal operation in open water (Richardson et al., 1995a). This higher 
sound production results from the greater amount of power and propeller 
cavitation required when operating in thick ice.
    Sound levels during ice-management activities would not be as 
intense as during icebreaking, and the resulting effects to marine 
species would be less significant in comparison. During ice-management, 
the vessel's propeller is rotating at approximately 15-20 percent of 
the vessel's propeller rotation capacity. Instead of actually breaking 
ice, during ice-management, the vessel redirects and repositions the 
ice by pushing it away from the direction of the drillship at slow 
speeds so that the ice floe does not slip past the vessel bow. 
Basically, ice-management occurs at slower speed, lower power, and 
slower propeller rotation speed (i.e., lower cavitation), allowing for 
fewer repositions of the vessel, thereby reducing cavitation effects in 
the water compared to those that would occur during icebreaking. Once 
on location at the drill sites in the Chukchi Sea, Shell plans to 
measure the sound levels produced by vessels operating in support of 
drilling operations. These vessels will include crew change vessels, 
tugs, ice-management vessels, and spill response vessels.

Aircraft Sound

    Helicopters may be used for personnel and equipment transport to 
and from the drillship, as well as any search-and-rescue operations 
that may be necessary. Under calm conditions, rotor and engine sounds 
are coupled into the water within a 26[deg] cone beneath the aircraft. 
Some of the sound will transmit beyond the immediate area, and some 
sound will enter the water outside the 26[deg] area when the sea 
surface is rough. However, scattering and absorption will limit lateral 
propagation in the shallow water.
    Dominant tones in noise spectra from helicopters are generally 
below 500 Hz (Greene and Moore, 1995). Harmonics of the main rotor and 
tail rotor usually dominate the sound from helicopters; however, many 
additional tones associated with the engines and other rotating parts 
are sometimes present.
    Because of doppler shift effects, the frequencies of tones received 
at a stationary site diminish when an aircraft passes overhead. The 
apparent frequency is increased while the aircraft approaches and is 
reduced while it moves away.
    Aircraft flyovers are not heard underwater for very long, 
especially when compared to how long they are heard in air as the 
aircraft approaches an observer. Helicopters flying to and from the 
drillship will generally maintain straight-line routes at altitudes of 
at least 1,000 ft (305 m), thereby limiting the received levels at and 
below the surface.

Tolerance

    Numerous studies have shown that underwater sounds from industry 
activities are often readily detectable by marine mammals in the water 
at distances of many kilometers. Numerous studies have also shown that 
marine mammals at distances more than a few kilometers away often show 
no apparent response to industry activities of various types (Miller et 
al., 2005). This is often true even in cases when the 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 underwater sound such as airgun pulses or 
vessels under some conditions, at other times mammals of all three 
types have shown no overt reactions (e.g., Malme et al., 1986; 
Richardson et al., 1995; Madsen and Mohl, 2000; Croll et al., 2001; 
Jacobs and Terhune, 2002; Madsen et al., 2002; Miller et al., 2005). In 
general, pinnipeds and small odontocetes seem to be more tolerant of 
exposure to some types of underwater sound than are baleen whales. 
Richardson et al. (1995a) found that vessel noise does not seem to 
strongly affect pinnipeds that are already in the water. Richardson et 
al. (1995a) went on to explain that seals on haul-outs sometimes 
respond strongly to the presence of vessels and at other times appear 
to show considerable

[[Page 25735]]

tolerance of vessels, and (Brueggeman et al., 1992; cited in Richardson 
et al., 1995a) observed ringed seals hauled out on ice pans displaying 
short-term escape reactions when a ship approached within 0.25-0.5 mi 
(0.4-0.8 km).

Masking

    The term ``masking'' refers to the obscuring of sounds of interest 
by interfering sounds, generally at similar frequencies. Masking 
effects of underwater sounds on marine mammal calls and other natural 
sounds are expected to be limited. For example, beluga whales primarily 
use high-frequency sounds to communicate and locate prey; therefore, 
masking by low-frequency sounds associated with drilling activities is 
not expected to occur (Gales, 1982, as cited in Shell, 2009). If the 
distance between communicating whales does not exceed their distance 
from the drilling activity, the likelihood of potential impacts from 
masking would be low (Gales, 1982, as cited in Shell, 2009). At 
distances greater than 660-1,300 ft (200-400 m), recorded sounds from 
drilling activities did not affect behavior of beluga whales, even 
though the sound energy level and frequency were such that it could be 
heard several kilometers away (Richardson et al., 1995b). This exposure 
resulted in whales being deflected from the sound energy and changing 
behavior. These minor changes are not expected to affect the beluga 
whale population (Richardson et al., 1991; Richard et al., 1998). 
Brewer et al. (1993) observed belugas within 2.3 mi (3.7 km) of the 
drilling unit Kulluk during drilling; however, the authors do not 
describe any behaviors that may have been exhibited by those animals. 
Please refer to the Arctic Multiple-Sale Draft Environmental Impact 
Statement (USDOI MMS, 2008), available on the Internet at: https://www.mms.gov/alaska/ref/EIS%20EA/ArcticMultiSale_209/_DEIS.htm, for 
more detailed information.
    There is evidence of other marine mammal species continuing to call 
in the presence of industrial activity. For example, bowhead whale 
calls are frequently detected in the presence of seismic pulses, 
although the number of calls detected may sometimes be reduced 
(Richardson et al., 1986; Greene et al., 1999; Blackwell et al., 2009). 
Additionally, annual acoustical monitoring near BP's Northstar 
production facility during the fall bowhead migration westward through 
the Beaufort Sea has recorded thousands of calls each year (for 
examples, see Richardson et al., 2007; Aerts and Richardson, 2008). 
Construction, maintenance, and operational activities have been 
occurring from this facility for nearly 10 years. To compensate and 
reduce masking, some mysticetes may alter the frequencies of their 
communication sounds (Richardson et al., 1995a; Parks et al., 2007). 
Masking processes in baleen whales are not amenable to laboratory 
study, and no direct measurements on hearing sensitivity are available 
for these species. It is not currently possible to determine with 
precision the potential consequences of temporary or local background 
noise levels. However, Parks et al. (2007) found that right whales 
altered their vocalizations, possibly in response to background noise 
levels. For species that can hear over a relatively broad frequency 
range, as is presumed to be the case for mysticetes, a narrow band 
source may only cause partial masking. Richardson et al. (1995a) note 
that a bowhead whale 12.4 mi (20 km) from a human sound source, such as 
that produced during oil and gas industry activities, might hear strong 
calls from other whales within approximately 12.4 mi (20 km), and a 
whale 3.1 mi (5 km) from the source might hear strong calls from whales 
within approximately 3.1 mi (5 km). Additionally, masking is more 
likely to occur closer to a sound source, and distant anthropogenic 
sound is less likely to mask short-distance acoustic communication 
(Richardson et al., 1995a).
    Cummings et al. (1984) subjected breeding ringed seals to 
recordings of industrial sounds. The authors did not document any 
impacts to ringed seal vocalizations as a result of exposure to the 
recordings.
    Although some masking by marine mammal species in the area may 
occur, the extent of the masking interference will depend on the 
spatial relationship of the animal and Shell's activity. If, as 
described later in this document, certain species avoid the proposed 
drilling locations, impacts from masking will be low.

Behavioral Disturbance Reactions

    Behavioral responses to sound are highly variable and context-
specific. Many different variables can influence an animal's perception 
of and response to (in both nature and magnitude) an acoustic event. An 
animal's prior experience with a sound or sound source affects whether 
it is less likely (habituation) or more likely (sensitization) to 
respond to certain sounds in the future (animals can also be innately 
pre-disposed to respond to certain sounds in certain ways; Southall et 
al., 2007). Related to the sound itself, the perceived nearness of the 
sound, bearing of the sound (approaching vs. retreating), similarity of 
a sound to biologically relevant sounds in the animal's environment 
(i.e., calls of predators, prey, or conspecifics), and familiarity of 
the sound may affect the way an animal responds to the sound (Southall 
et al., 2007). Individuals (of different age, gender, reproductive 
status, etc.) among most populations will have variable hearing 
capabilities and differing behavioral sensitivities to sounds that will 
be affected by prior conditioning, experience, and current activities 
of those individuals. Often, specific acoustic features of the sound 
and contextual variables (i.e., proximity, duration, or recurrence of 
the sound or the current behavior that the marine mammal is engaged in 
or its prior experience), as well as entirely separate factors such as 
the physical presence of a nearby vessel, may be more relevant to the 
animal's response than the received level alone.
    Exposure of marine mammals to sound sources can result in (but is 
not limited to) no response or any of the following observable 
responses: increased alertness; orientation or attraction to a sound 
source; vocal modifications; cessation of feeding; cessation of social 
interaction; alteration of movement or diving behavior; avoidance; 
habitat abandonment (temporary or permanent); and, in severe cases, 
panic, flight, stampede, or stranding, potentially resulting in death 
(Southall et al., 2007). On a related note, many animals perform vital 
functions, such as feeding, resting, traveling, and socializing, on a 
diel cycle (24-hr cycle). Behavioral reactions to noise exposure (such 
as disruption of critical life functions, displacement, or avoidance of 
important habitat) are more likely to be significant if they last more 
than one diel cycle or recur on subsequent days (Southall et al., 
2007). Consequently, a behavioral response lasting less than one day 
and not recurring on subsequent days is not considered particularly 
severe unless it could directly affect reproduction or survival 
(Southall et al., 2007).
    Detailed studies regarding responses to anthropogenic sound have 
been conducted on humpback, gray, and bowhead whales and ringed seals. 
Less detailed data are available for some other species of baleen 
whales, sperm whales, small toothed whales, and sea otters. The 
following sub-sections provide examples of behavioral responses that 
provide an idea of the variability that would be expected given the 
different sensitivities of marine

[[Page 25736]]

mammal species to sound and the wide range of potential acoustic 
sources to which a marine mammal may be exposed.
    Baleen Whales--Baleen whale responses to pulsed sound (e.g., 
seismic airguns) have been studied more thoroughly than responses to 
continuous sound (e.g., drillships). 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 
greater distances (Miller et al., 2005). However, baleen whales exposed 
to strong noise pulses often react by deviating from their normal 
migration route (Richardson et al., 1999). Migrating gray and bowhead 
whales were observed avoiding the sound source by displacing their 
migration route to varying degrees but within the natural boundaries of 
the migration corridors (Schick and Urban, 2000; Richardson et al., 
1999; Malme et al., 1983).
    Richardson et al. (1995b) reported changes in surfacing and 
respiration behavior and the occurrence of turns during surfacing in 
bowhead whales exposed to playback of underwater sound from drilling 
activities. These behavioral effects were localized and occurred at 
distances up to 1.2-2.5 mi (2-4 km). Some bowheads appeared to divert 
from their migratory path after exposure to projected icebreaker 
sounds. Other bowheads, however, tolerated projected icebreaker sound 
at levels 20 dB and more above ambient sound levels. The source level 
of the projected sound, however, was much less than that of an actual 
icebreaker, and reaction distances to actual ice breaking may be much 
greater than those reported here for projected sounds.
    Brewer et al. (1993) and Hall et al. (1994) reported numerous 
sightings of marine mammals including bowhead whales in the vicinity of 
offshore drilling operations in the Beaufort Sea. One bowhead whale 
sighting was reported within approximately 1,312 ft (400 m) of a 
drilling vessel although other sightings were at much greater 
distances. Few bowheads were recorded near industrial activities by 
aerial observers, but observations by surface observers suggested that 
bowheads may have been closer to industrial activities than was 
suggested by results of aerial observations.
    Richardson et al. (2008) reported a slight change in the 
distribution of bowhead whale calls in response to operational sounds 
on BP's Northstar Island. The southern edge of the call distribution 
ranged from 0.47 to 1.46 mi (0.76 to 2.35 km) farther offshore, 
apparently in response to industrial sound levels. This result, 
however, was only achieved after intensive statistical analyses, and it 
is not clear that this represented a biologically significant effect.
    Patenaude et al. (2002) reported fewer behavioral responses to 
aircraft overflights by bowhead compared to beluga whales. Behaviors 
classified as reactions consisted of short surfacings, immediate dives 
or turns, changes in behavior state, vigorous swimming, and breaching. 
Most bowhead whale reactions resulted from exposure to helicopter 
activity and little response to fixed-wing aircraft was observed. Most 
reactions occurred when the helicopter was at altitudes <=492 ft (150 
m) and lateral distances <=820 ft (250 m; Nowacek et al., 2007). 
Restriction on aircraft altitude will be part of the proposed 
mitigation measures (described in the ``Proposed Mitigation'' section 
later in this document) during the proposed drilling activities, and 
overflights are likely to have little or no disturbance effects on 
baleen whales. Any disturbance that may occur would likely be temporary 
and localized.
    Southall et al. (2007, Appendix C) reviewed a number of papers 
describing the responses of marine mammals to non-pulsed sound, such as 
that produced during exploratory drilling operations. In general, 
little or no response was observed in animals exposed at received 
levels from 90-120 dB re 1 [mu]Pa (rms). Probability of avoidance and 
other behavioral effects increased when received levels were from 120-
160 dB re 1 [mu]Pa (rms). Some of the relevant reviews contained in 
Southall et al. (2007) are summarized next.
    Baker et al. (1982) reported some avoidance by humpback whales to 
vessel noise when received levels were 110-120 dB (rms) and clear 
avoidance at 120-140 dB (sound measurements were not provided by Baker 
but were based on measurements of identical vessels by Miles and Malme, 
1983).
    Malme et al. (1983, 1984) used playbacks of sounds from helicopter 
overflight and drilling rigs and platforms to study behavioral effects 
on migrating gray whales. Received levels exceeding 120 dB induced 
avoidance reactions. Malme et al. (1984) calculated 10 percent, 50 
percent, and 90 percent probabilities of gray whale avoidance reactions 
at received levels of 110, 120, and 130 dB, respectively. Malme et al. 
(1986) observed the behavior of feeding gray whales during four 
experimental playbacks of drilling sounds (50 to 315 Hz; 21-min overall 
duration and 10 percent duty cycle; source levels of 156-162 dB). In 
two cases for received levels of 100-110 dB, no behavioral reaction was 
observed. However, avoidance behavior was observed in two cases where 
received levels were 110-120 dB.
    Richardson et al. (1990) performed 12 playback experiments in which 
bowhead whales in the Alaskan Arctic were exposed to drilling sounds. 
Whales generally did not respond to exposures in the 100 to 130 dB 
range, although there was some indication of minor behavioral changes 
in several instances.
    McCauley et al. (1996) reported several cases of humpback whales 
responding to vessels in Hervey Bay, Australia. Results indicated clear 
avoidance at received levels between 118 to 124 dB in three cases for 
which response and received levels were observed/measured.
    Palka and Hammond (2001) analyzed line transect census data in 
which the orientation and distance off transect line were reported for 
large numbers of minke whales. The authors developed a method to 
account for effects of animal movement in response to sighting 
platforms. Minor changes in locomotion speed, direction, and/or diving 
profile were reported at ranges from 1,847 to 2,352 ft (563 to 717 m) 
at received levels of 110 to 120 dB.
    Biassoni et al. (2000) and Miller et al. (2000) reported behavioral 
observations for humpback whales exposed to a low-frequency sonar 
stimulus (160- to 330-Hz frequency band; 42-s tonal signal repeated 
every 6 min; source levels 170 to 200 dB) during playback experiments. 
Exposure to measured received levels ranging from 120 to 150 dB 
resulted in variability in humpback singing behavior. Croll et al. 
(2001) investigated responses of foraging fin and blue whales to the 
same low frequency active sonar stimulus off southern California. 
Playbacks and control intervals with no transmission were used to 
investigate behavior and distribution on time scales of several weeks 
and spatial scales of tens of kilometers. The general conclusion was 
that whales remained feeding within a region for which 12 to 30 percent 
of exposures exceeded 140 dB.
    Frankel and Clark (1998) conducted playback experiments with 
wintering humpback whales using a single speaker producing a low-
frequency ``M-sequence'' (sine wave with multiple-phase reversals) 
signal in the 60 to 90 Hz band with output of 172 dB at 1 m. For 11 
playbacks, exposures were

[[Page 25737]]

between 120 and 130 dB re 1 [mu]Pa (rms) and included sufficient 
information regarding individual responses. During eight of the trials, 
there were no measurable differences in tracks or bearings relative to 
control conditions, whereas on three occasions, whales either moved 
slightly away from (n = 1) or towards (n = 2) the playback speaker 
during exposure. The presence of the source vessel itself had a greater 
effect than did the M-sequence playback.
    Finally, Nowacek et al. (2004) used controlled exposures to 
demonstrate behavioral reactions of northern right whales to various 
non-pulse sounds. Playback stimuli included ship noise, social sounds 
of conspecifics, and a complex, 18-min ``alert'' sound consisting of 
repetitions of three different artificial signals. Ten whales were 
tagged with calibrated instruments that measured received sound 
characteristics and concurrent animal movements in three dimensions. 
Five out of six exposed whales reacted strongly to alert signals at 
measured received levels between 130 and 150 dB (i.e., ceased foraging 
and swam rapidly to the surface). Two of these individuals were not 
exposed to ship noise, and the other four were exposed to both stimuli. 
These whales reacted mildly to conspecific signals. Seven whales, 
including the four exposed to the alert stimulus, had no measurable 
response to either ship sounds or actual vessel noise.
    Toothed Whales--Most toothed whales have the greatest hearing 
sensitivity at frequencies much higher than that of baleen whales and 
may be less responsive to low-frequency sound commonly associated with 
oil and gas industry exploratory drilling activities. Richardson et al. 
(1995b) reported that beluga whales did not show any apparent reaction 
to playback of underwater drilling sounds at distances greater than 
656-1,312 ft (200-400 m). Reactions included slowing down, milling, or 
reversal of course after which the whales continued past the projector, 
sometimes within 164-328 ft (50-100 m). The authors concluded (based on 
a small sample size) that the playback of drilling sounds had no 
biologically significant effects on migration routes of beluga whales 
migrating through pack ice and along the seaward side of the nearshore 
lead east of Pt. Barrow in spring.
    At least six of 17 groups of beluga whales appeared to alter their 
migration path in response to underwater playbacks of icebreaker sound 
(Richardson et al., 1995b). Received levels from the icebreaker 
playback were estimated at 78-84 dB in the \1/3\-octave band centered 
at 5,000 Hz, or 8-14 dB above ambient. If beluga whales reacted to an 
actual icebreaker at received levels of 80 dB, reactions would be 
expected to occur at distances on the order of 6.2 mi (10 km). Finley 
et al. (1990) also reported beluga avoidance of icebreaker activities 
in the Canadian High Arctic at distances of 22-31 mi (35-50 km). In 
addition to avoidance, changes in dive behavior and pod integrity were 
also noted. However, while the Vladimir Ignatjuk (an icebreaker) is 
anticipated to be one of the vessels attending the Discoverer, it will 
only be conducting ice-management activities (which were described in 
the ``Description of the Specified Activity'' section earlier in this 
document) and not physical breaking of ice. Thus, NMFS does not 
anticipate that marine mammals would exhibit the types of behavioral 
reactions as those noted in the aforementioned studies.
    Patenaude et al. (2002) reported that beluga whales appeared to be 
more responsive to aircraft overflights than bowhead whales. Changes 
were observed in diving and respiration behavior, and some whales 
veered away when a helicopter passed at <=820 ft (250 m) lateral 
distance at altitudes up to 492 ft (150 m). However, some belugas 
showed no reaction to the helicopter. Belugas appeared to show less 
response to fixed-wing aircraft than to helicopter overflights.
    In reviewing responses of cetaceans with best hearing in mid-
frequency ranges, which includes toothed whales, Southall et al. (2007) 
reported that combined field and laboratory data for mid-frequency 
cetaceans exposed to non-pulse sounds did not lead to a clear 
conclusion about received levels coincident with various behavioral 
responses. In some settings, individuals in the field showed profound 
(significant) behavioral responses to exposures from 90 to 120 dB, 
while others failed to exhibit such responses for exposure to received 
levels from 120 to 150 dB. Contextual variables other than exposure 
received level, and probable species differences, are the likely 
reasons for this variability. Context, including the fact that captive 
subjects were often directly reinforced with food for tolerating noise 
exposure, may also explain why there was great disparity in results 
from field and laboratory conditions--exposures in captive settings 
generally exceeded 170 dB before inducing behavioral responses. A 
summary of some of the relevant material reviewed by Southall et al. 
(2007) is next.
    LGL and Greeneridge (1986) and Finley et al. (1990) documented 
belugas and narwhals congregated near ice edges reacting to the 
approach and passage of ice-breaking ships. Beluga whales responded to 
oncoming vessels by (1) fleeing at speeds of up to 12.4 mi/hr (20 km/
hr) from distances of 12.4-50 mi (20-80 km), (2) abandoning normal pod 
structure, and (3) modifying vocal behavior and/or emitting alarm 
calls. Narwhals, in contrast, generally demonstrated a ``freeze'' 
response, lying motionless or swimming slowly away (as far as 23 mi [37 
km] down the ice edge), huddling in groups, and ceasing sound 
production. There was some evidence of habituation and reduced 
avoidance 2 to 3 days after onset.
    The 1982 season observations by LGL and Greeneridge (1986) involved 
a single passage of an icebreaker with both ice-based and aerial 
measurements on June 28, 1982. Four groups of narwhals (n = 9 to 10, 7, 
7, and 6) responded when the ship was 4 mi (6.4 km) away (received 
levels of approximately 100 dB in the 150- to 1,150-Hz band). At a 
later point, observers sighted belugas moving away from the source at 
more than 12.4 mi (20 km; received levels of approximately 90 dB in the 
150- to 1,150-Hz band). The total number of animals observed fleeing 
was about 300, suggesting approximately 100 independent groups (of 
three individuals each). No whales were sighted the following day, but 
some were sighted on June 30, with ship noise audible at spectrum 
levels of approximately 55 dB/Hz (up to 4 kHz).
    Observations during 1983 (LGL and Greeneridge, 1986) involved two 
ice-breaking ships with aerial survey and ice-based observations during 
seven sampling periods. Narwhals and belugas generally reacted at 
received levels ranging from 101 to 121 dB in the 20- to 1,000-Hz band 
and at a distance of up to 40.4 mi (65 km). Large numbers (100s) of 
beluga whales moved out of the area at higher received levels. As noise 
levels from icebreaking operations diminished, a total of 45 narwhals 
returned to the area and engaged in diving and foraging behavior. 
During the final sampling period, following an 8-h quiet interval, no 
reactions were seen from 28 narwhals and 17 belugas (at received levels 
ranging up to 115 dB).
    The final season (1984) reported in LGL and Greeneridge (1986) 
involved aerial surveys before, during, and after the passage of two 
ice-breaking ships. During operations, no belugas and few narwhals were 
observed in an area approximately 16.8 mi (27 km) ahead of the vessels, 
and all whales sighted over 12.4-50 mi (20-80 km) from the ships

[[Page 25738]]

were swimming strongly away. Additional observations confirmed the 
spatial extent of avoidance reactions to this sound source in this 
context.
    Buckstaff (2004) reported elevated dolphin whistle rates with 
received levels from oncoming vessels in the 110 to 120 dB range in 
Sarasota Bay, Florida. These hearing thresholds were apparently lower 
than those reported by a researcher listening with towed hydrophones. 
Morisaka et al. (2005) compared whistles from three populations of 
Indo-Pacific bottlenose dolphins. One population was exposed to vessel 
noise with spectrum levels of approximately 85 dB/Hz in the 1- to 22-
kHz band (broadband received levels approximately 128 dB) as opposed to 
approximately 65 dB/Hz in the same band (broadband received levels 
approximately 108 dB) for the other two sites. Dolphin whistles in the 
noisier environment had lower fundamental frequencies and less 
frequency modulation, suggesting a shift in sound parameters as a 
result of increased ambient noise.
    Morton and Symonds (2002) used census data on killer whales in 
British Columbia to evaluate avoidance of non-pulse acoustic harassment 
devices (AHDs). Avoidance ranges were about 2.5 mi (4 km). Also, there 
was a dramatic reduction in the number of days ``resident'' killer 
whales were sighted during AHD-active periods compared to pre- and 
post-exposure periods and a nearby control site.
    Awbrey and Stewart (1983) played back semi-submersible drillship 
sounds (source level: 163 dB) to belugas in Alaska. They reported 
avoidance reactions at 984 and 4,921 ft (300 and 1,500 m) and approach 
by groups at a distance of 2.2 mi (3.5 km; received levels 
approximately 110 to 145 dB over these ranges assuming a 15 log R 
transmission loss). Similarly, Richardson et al. (1990) played back 
drilling platform sounds (source level: 163 dB) to belugas in Alaska. 
They conducted aerial observations of eight individuals among 
approximately 100 spread over an area several hundred meters to several 
kilometers from the sound source and found no obvious reactions. 
Moderate changes in movement were noted for three groups swimming 
within 656 ft (200 m) of the sound projector.
    Two studies deal with issues related to changes in marine mammal 
vocal behavior as a function of variable background noise levels. Foote 
et al. (2004) found increases in the duration of killer whale calls 
over the period 1977 to 2003, during which time vessel traffic in Puget 
Sound, and particularly whale-watching boats around the animals, 
increased dramatically. Scheifele et al. (2005) demonstrated that 
belugas in the St. Lawrence River increased the levels of their 
vocalizations as a function of the background noise level (the 
``Lombard Effect'').
    Harbor porpoise off Vancouver Island, British Columbia, were found 
to be sensitive to the simulated sound of a 2-megawatt offshore wind 
turbine (Koschinski et al., 2003). The porpoises remained significantly 
further away from the sound source when it was active, and this effect 
was seen out to a distance of 60 m (197 ft). The device used in that 
study produced sounds in the frequency range of 30 to 800 Hz, with peak 
source levels of 128 dB re 1 [micro]Pa at 1 m at the 80- and 160-Hz 
frequencies.
    Kastelein et al. (2005) exposed two captive harbor porpoise (a 
high-frequency cetacean) to various non-pulse sounds in an 
approximately 111.5 x 65.6 ft (34 x 20 m) enclosure. The frequency 
range of the four test sounds fell into the \1/3\-octave bands 8, 10, 
12.5, and 16 kHz, with a source level range of 116 to 130 [plus or 
minus 3] dB, depending on the sound source. Each session lasted for 30 
minutes (15-min period of baseline [no sound emission] followed 
immediately by 15-min test period [sound emission]). The researchers 
measured the distance between the underwater transducer and the 
surfacing area of the porpoises to determine the deterrent effect and 
the number of respirat