Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Open Water Marine Seismic Survey in the Chukchi Sea, Alaska

DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XW13

Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Open Water Marine Seismic Survey in the Chukchi Sea, Alaska

AGENCY:

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

ACTION:

Notice; issuance of an incidental take authorization.

SUMMARY:

In accordance with the Marine Mammal Protection Act (MMPA) regulations, notification is hereby given that NMFS has issued an Incidental Harassment Authorization (IHA) to Statoil USA E&P Inc. (Statoil) to take, by harassment, small numbers of 12 species of marine mammals incidental to a marine seismic survey program in the Chukchi Sea, Alaska, during the 2010 Arctic open water season.

DATES:

Effective August 6, 2010, through November 30, 2010.

ADDRESSES:

Inquiry for information on the incidental take authorization 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. A copy of the application containing a list of the references used in this document, NMFS' Environmental Assessment (EA) and Finding of No Significant Impact (FONSI), and the IHA may be obtained by writing to the address specified above, telephoning the contact listed below (

see

FOR FURTHER INFORMATION CONTACT

), or visiting the Internet at:

http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications.

Documents cited in this notice may be viewed, by appointment, during regular business hours, at the aforementioned address.

FOR FURTHER INFORMATION CONTACT:

Shane Guan, 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 U.S. 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

NMFS received an application on December 24, 2009, from Statoil for the taking, by harassment, of marine mammals incidental to 3D and 2D marine seismic surveys in the Chukchi Sea, Alaska, during the 2010 open-water season. After addressing comments from NMFS, Statoil modified its application and submitted a revised application on April 12, 2010. The April 12, 2010, application was the one available for public comment (see

ADDRESSES

) and considered by NMFS for the IHA.

The marine seismic survey will use two towed airgun arrays consisting of 26 active (10 spare) airguns with a maximum discharge volume of 3,000 cubic inch (in

3

). The 3D survey will take place in a 915 mi

2

(2,370 km

2

) survey area approximately 150 mi (241 km) west of Barrow in water depth of approximately 100 to 165 ft (30 to 50 m). The seismic survey is designed to collect 3D data of the deep sub-surface in Statoil's Chukchi leases in support of future oil and gas development within the area of coverage. The data will help identify source rocks, migration pathways, and play types. In addition, a 2D tie line survey has been designed as a second priority program to acquire useful information in the region. The four stand alone 2D lines (with a total length of approximately 420 mi or 675 km) are designed to tie the details of the new high resolution 3D image to the surrounding regional geology to facilitate interpretation of more regional trends. The number of 2D km acquired will to some degree be dependent on the 2010 season's restrictive ice coverage and the 3D data acquisition progress.

Statoil intends to conduct these marine surveys during the 2010 Arctic open-water season (July through November). Impacts to marine mammals may occur from noise produced by airgun sources used in the surveys.

Description of the Specified Activity

Statoil plans to conduct geophysical data acquisition activities in the Chukchi Sea in the period late July through the end of November, 2010. Data acquisition is expected to take approximately 60 days (including anticipated downtime), but the total period for this request was from July 25 through November 30 to allow for unexpected downtime (the IHA became effective on August 6, 2010). The project area encompasses approximately 915 mi

2

(2,370 km

2

) in Statoil lease holdings in the Bureau of Ocean Energy Management, Regulation, and Enforcement's (BOEMRE) (formerly the Minerals Management Service) Outer Continental Shelf (OCS) Lease Sale 193 area in the northern Chukchi Sea (Figure 1 of the Statoil IHA application). The activities consist of 3D seismic data acquisition and a 2D tie line survey as a second priority program.

The entire 3D program, if it can be completed, will consist of approximately 3,100 mi (4,990 km) of production line, not including line turns. A total of four 2D well tie lines with a total length of approximately 420 mi (675 km) are included in the survey

plan as a second priority program. The 3D seismic data acquisition will be conducted from the M/V Geo Celtic. The M/V Geo Celtic will tow two identical airgun arrays at approximately 20 ft (6 m) depth and at a distance of about 902 ft (275 m) behind the vessel. Each array is composed of three strings for a total of 26 active G-guns (4×60 in

3

, 8×70 in

3

, 6×100 in

3

, 4×150 in

3

, and 4×250 in

3

) with a total discharge volume of 3000 in

3

. Each array also consists of 5 clusters of 10 inactive airguns that will be used as spares. One of the smallest guns in the array (60 in

3

) will be used as the mitigation gun. More details of the airgun array and its components are described in Appendix B of Statoil's IHA application. In addition to the airgun array, pinger systems (DigiRANGE II, or similar systems) will be used to position the streamer array relative to the vessel.

The estimated source level for the full 3000 in

3

array is 245 dB re 1 μPa (rms) at 1 m. The maximum distances to received levels of 190, 180 160, and 120 dB re 1 μPa (rms) from sound source verification (SSV) measurements of the 3,147 in

3

airgun array used in the Chukchi Sea during 2006-2008 were used to model the received levels at these distances, which show that the maximum distances are 700, 2,500, 13,000, and 120,000 m, respectively. The SSV tests will provide received sound measurements in 10-dB increments between 120-190-dB isopleths. NMFS does not consider marine mammals exposed to impulse sounds below the 160 dB received level to be taken. The sole purpose of measuring to the 120 dB distance is to assess how far the sound source attenuates in the Arctic for the proposed seismic survey and the resulting information has not been factored into NMFS' MMPA decision for the Statoil seismic activities.

The estimated source level of the mitigation gun (

i.e.,

the single 60 in

3

airgun noted above) is 230 dB re 1 μPa (rms) at 1 m, and the modeled distances to received levels of 190, 180 160, and 120 dB re 1 μPa (rms) are 75, 220, 1,800, and 50,000 m, respectively.

The DigiRANGE II pinger system produces very short pulses, occurring for 10 ms, with source levels of approximately 180 dB re 1 μPa (rms) at 1 m at 55 kHz, 188 dB re 1 μPa (rms) at 1 m at 75 kHz, and 184 dB re 1 μPa (rms) at 1 m at 95 kHz. One pulse is emitted on command from the operator aboard the source vessel, which under normal operating conditions is once every 10 s. Most of the energy in the sound pulses emitted by this pinger is between 50 and 100 kHz. The signal is omnidirectional. Using a simple spherical spreading modeling for sound propagation, the calculated distances to received levels of 180, 160, and 120 dB re 1 μPa (rms) are 2.5 m, 25 m, and 2,512 m, respectively. These distances are well within the radii for airgun arrays and that of a single mitigation gun.

The vessel will travel along pre-determined lines at a speed of about 4-5 knots while one of the airgun arrays discharges every 8-10 seconds (shot interval 61.52 ft [18.75 m]). The streamer hydrophone array will consist of twelve streamers of up to approximately 2.2 mi (4 km) in length, with a total of 20,000-25,000 hydrophones at 6.6 ft (2 m) spacing. This large hydrophone streamer receiver array, designed to maximize efficiency and minimize the number of source points, will receive the reflected signals from the airgun array and transfer the data to an on-board processing system.

A 2D tie line survey has been designed as a second priority program to allow the vessel to acquire useful information in the region. The four stand alone 2D lines have a total length of approximately 420 mi (675 km) and are designed to tie the details of the new high resolution 3D image to known surrounding regional geology.

The approximate boundaries of the total surface area are between 71°30′ N and 72°00′ N and between 165° W and 162°30′ W. The water depth in the survey area varies from 100 to 165 ft (30 to 50 m).

The vessels involved in the seismic survey activities will consist of at least three vessels as listed below. Specifications of these vessels (or equivalent vessels if availability changes) are provided in Appendix A of Statoil's IHA application.

• One (1) seismic source vessel, the M/V Geo Celtic or similar equipped vessel, to tow the two 3,000 in

3

airgun arrays and hydrophone streamer for the 3D (and 2D) seismic data acquisition and to serve as a platform for marine mammal monitoring;

• One (1) chase/monitoring vessel, the M/V Gulf Provider or similar equipped vessel, for marine mammal monitoring, crew transfer, support and supply duties.

• One (1) chase/monitoring vessel, the M/V Thor Alpha or similar equipped vessel, for marine mammal monitoring, support and supply duties.

The M/V Geo Celtic, or similar vessel, arrived in Dutch Harbor around mid July 2010. The vessels were resupplied and the crew changed at this port. All three vessels had departed Dutch Harbor at the end of July with an expected transit time of approximately 5 days (weather depending). Directly upon arrival in the 3D survey area, depending on ice conditions, the M/V Geo Celtic will deploy the airgun array and start operating their guns for the purpose of sound source verification measurements (see Statoil IHA application for more details). The startup date of seismic data acquisition is expected to be early/mid August but depends on local ice conditions.

Upon completion of these measurements the seismic data acquisition in the Chukchi Sea will start and, depending on the start date, is expected to be completed in the first half of October. This is based on an estimated duration of 60 days from first to last shot point (including anticipated downtime). The data acquisition is a 24-hour operation.

Comments and Responses

A notice of NMFS' proposal to issue an IHA to Statoil published in the

Federal Register

on June 8, 2010 (75 FR 32379). That notice described, in detail, Statoil's proposed activity, the marine mammal species that may be affected by the activity, and the anticipated effects on marine mammals. During the 30-day public comment period, NMFS received five comment letters from the following: The Marine Mammal Commission (Commission); the Alaska Eskimo Whaling Commission (AEWC); the North Slope Borough Office of the Mayor (NSB); and Alaska Wilderness League (AWL), Audubon Alaska, Center for Biological Diversity, Defenders of Wildlife, Earthjustice, Greenpeace, Natural Resources Defense Council, Northern Alaska Environmental Center, Ocean Conservancy, Oceana, Pacific Environment, Sierra Club, and World Wildlife Fund (collectively “AWL”), along with an attached letter from Dr. David E. Bain, a contract scientist for NMFS.

The AEWC submitted several journal articles as attachments to its comment letters. NMFS acknowledges receipt of these documents but does not intend to address the specific articles themselves in the responses to comments, since these articles are merely used as citations in AEWC's comments. AEWC also submitted copies of 2009 and 2010 Conflict Avoidance Agreement (CAA), since Statoil declined to sign the CAA. Dr. Bain also attached an in-review journal article he coauthored. Any comments specific to Statoil's application that address the statutory and regulatory requirements or findings NMFS must make to issue an IHA are addressed in this section of the

Federal Register

notice.

General Comments

Comment 1:

AEWC believes that NMFS should not issue incidental take authorizations for oil and gas-related activities given the current suspension of offshore drilling in Alaska and pending reorganization of the Minerals Management Service (MMS). AEWC points out that the harm caused by an oil spill is not the only risk to marine mammals posed by oil and gas activities on the OCS and that there are concerns regarding underwater noise from geophysical activities and the threats posed to marine mammals from noise and chemical pollution, as well as increased vessel traffic. AEWC further claims that many times, NMFS issued IHAs over the objections of the scientific and subsistence communities as well as the agencies' own scientists.

Response:

The legal requirements and underlying analysis for the issuance of an IHA concerning take associated with seismic activities are unrelated to the moratorium on offshore drilling and reorganization of the MMS. In order to issue an authorization pursuant to Section 101(a)(5)(D) of the MMPA, NMFS must determine that the taking by harassment of small numbers of marine mammals will have a negligible impact on affected species or stocks, and will not have an unmitigable adverse impact on the availability of affected species or stocks for taking for subsistence uses. If NMFS is able to make these findings, the Secretary is required to issue an IHA. In the case of Statoil's activities for 2010 (as described in the application, the notice of proposed IHA (75 FR 32379; June 8, 2010) and this document), NMFS determined that it was able to make the required MMPA findings. Additionally, as described later in this section and throughout this document, NMFS has determined that Statoil's activities will not result in injury or mortality of marine mammals, and no injury or mortality is authorized under the IHA.

As discussed in detail in the proposed IHA (75 FR 32379; June 18, 2010), the EA for the issuance of IHAs to Shell and Statoil for the proposed open water marine and seismic surveys, and this document, NMFS has conducted a thorough analysis of the potential impacts of underwater anthropogenic sound (especially sound from geophysical surveys) on marine mammals. We have cited multiple studies and research that support NMFS MMPA and National Environmental Policy Act (NEPA) determinations that the localized and short-term disturbance from seismic surveys, with strict mitigation and monitoring measures implemented, are likely to result in negligible impacts to marine mammals and their habitat and no significant impact to the human environment, respectively. Although issuance of the IHA may be of concern to certain members of the public, the proposed issuance of the IHA was carefully reviewed and analyzed by NMFS scientists at headquarters and through Endangered Species Act (ESA) section 7 consultation at NMFS Alaska Regional Office, and by an independent bioacoustics expert. Based on those reviews, NMFS staff in the Office of Protected Resources made appropriate changes to this document.

Comment 2:

The Commission requests that NMFS clarify whether the 3D and 2D seismic surveys will occur simultaneously or independent of one another and, if they will occur independently, recalculate the total exposed area and subsequent exposures for the 2D surveys.

Response:

As stated in Statoil's IHA application, the 3D and 2D seismic surveys will occur independently. The total exposed area and subsequent exposures for the 2D surveys are reported in Statoil's IHA application.

MMPA Concerns

Comment 3:

AEWC notes their disappointment in NMFS for releasing for public comment an incomplete application from Statoil that fails to provide the mandatory information required by the MMPA and NMFS' implementing regulations. AEWC requests that NMFS return Statoil's application as incomplete, or else the agency risks making arbitrary and indefensible determinations under the MMPA. The following is the information that AEWC believes to be missing from Statoil's application: (1) For several species, a thorough “description of the status, distribution, and seasonal distribution (when applicable) of the affected species or stocks of marine mammals likely to be affected” (50 CFR 216.104(a)(4)); (2) a description of the “age, sex, and reproductive condition” of the marine mammals that will be impacted, particularly in regard to bowhead whales (50 CFR 216.104(a)(6)); (3) an adequate detailing of “the anticipated impact of the activity upon the species or stock of marine mammals” (50 CFR 216.104(a)(7)); (4) the economic “availability and feasibility * * * of equipment, methods, and manner of conducting such activity or other means of effecting the least practicable adverse impact upon the affected species or stocks, their habitat, and on their availability for subsistence uses, paying particular attention to rookeries, mating grounds, and areas of similar significance” (50 CFR 216.104(a)(11)); and (5) suggested means of learning of, encouraging, and coordinating any research related activities (50 CFR 216.104(a)(14)). NSB also notes its concern about the lack of specificity regarding the timing and location of the proposed surveys, as well as the lack of specificity regarding the surveys themselves.

Response:

NMFS does not agree that it released an incomplete application for review during the public comment period. After NMFS' initial review of the application, NMFS submitted questions and comments to Statoil on its application. After receipt and review of Statoil's responses, which were incorporated into the final version of the IHA application that was released to the public for review and comment, NMFS made its determination of completeness and released the application, addenda, and the proposed IHA notice (75 FR 32379; June 8, 2010). Regarding the three specific pieces of information believed to be missing by AEWC, Statoil's original application included a description of the pieces of information that are required pursuant to 50 CFR 216.104(a)(12).

Information required pursuant to 50 CFR 216.104(a)(4) and (6) requires that an applicant submit information on the “status, distribution, and seasonal distribution (when applicable) of the affected species or stocks of marine mammals likely to be affected” and “age, sex, and reproductive condition (if possible)” of the number of marine mammals that may be taken, respectively. In the application, Statoil described the species expected to be taken by harassment and provided estimates of how many of each species were expected to be taken during their activities. The status and distribution of these species are included in Section IV of Statoil's IHA application, the proposed IHA (75 FR 32379; June 8, 2010), and in this document. However, in most cases, it is difficult to estimate how many animals, especially cetaceans, of each age, sex, and reproductive condition will be taken or impacted by seismic surveys, because group composition of animals varies greatly by time and space.

In Section VII of Statoil's IHA application, the proposed IHA (75 FR 32379; June 8, 2010), and in this document, detailed discussion on the anticipated impacts from the proposed Statoil open water seismic survey in the Chukchi is provided, as required under 50 CFR 216.104(a)(7). The description of the anticipated impacts includes

discussions on potential effects from airgun noise and pinger signers.

Statoil also provided information on economic “availability and feasibility * * * of equipment, methods, and manner of conducting such activity or other means of effecting the least practicable adverse impact upon the affected species or stocks, their habitat, and on their availability for subsistence uses, paying particular attention to rookeries, mating grounds, and areas of similar significance” (50 CFR 216.104(a)(11)) in its IHA application. In its application, Statoil states that four main mitigations regarding the open water marine seismic survey in the Chukchi Sea are proposed: (1) Timing and locations for active survey acquisition work; (2) to configure airguns in a manner that directs energy primarily down to the seabed thus decreasing the range of horizontal spreading of noise; (3) using an energy source which is as small as possible while still accomplishing the survey objectives; and (4) curtailing active survey work when the marine mammal observers sight visually (from shipboard) the presence of marine mammals within identified ensonified zones. Details of these mitigation measures are discussed further in the 4MP that is included in Statoil's IHA application. In addition to these measures, NMFS' Notice of Proposed IHA (75 FR 32379; June 8, 2010) described mitigation measures proposed to be implemented by Statoil (outlined in the application), as well as additional measures proposed by NMFS for inclusion in an IHA.

Lastly, information required pursuant to 50 CFR 216.104(a)(14) was also included in Statoil's application. Statoil states that it will cooperate with any number of external entities, including other energy companies, agencies, universities, and NGOs, in its efforts to manage, understand, and fully communicate information about environmental impacts related to seismic activities. Statoil is a member of the OGP E&P Sound & Marine Life joint industry programme (JIP), which is an international consortium of oil and gas companies organized under the OGP in London. The objective of the JIP program is to obtain valid data on the effects of sounds produced by the gas exploration and production industry on marine life. Additionally, Statoil, Shell, and ConocoPhillips (CPAI) are jointly funding an extensive science program in the Chukchi Sea, which will be carried out by Olgoonik-Fairweather LLC to continue the acoustic monitoring programs of 2006-2009 with a total of 44 acoustic recorders distributed both broadly across the Chukchi lease area and nearshore environment and intensively on the Statoil, Burger (Shell), and Klondike (CPAI) lease holdings. Please refer to Statoil's IHA application and the proposed IHA (75 FR 32379; June 8, 2010) for a detailed description of the science program.

In conclusion, NMFS believes that Statoil provided all of the necessary information to proceed with publishing a proposed IHA notice in the

Federal Register

.

Comment 4:

AEWC and NSB state that NMFS failed to issue a draft authorization for public review and comment. The plain language of both the MMPA and NMFS' implementing regulations require that NMFS provide the opportunity for public comment on the “proposed incidental harassment authorization” (50 CFR 216.104(b)(1)(i); 16 U.S.C. 1371(a)(5)(D)(iii)) and not just on the application itself as NMFS has done here. Given Statoil's refusal to sign the CAA and without a complete draft authorization and accompanying findings, AEWC states that it cannot provide meaningful comments on Statoil's proposed activities, ways to mitigate the impacts of those activities on marine mammals, and measures that are necessary to protect subsistence uses and sensitive resources.

Response:

The June 8, 2010 proposed IHA notice (75 FR 32379) contained all of the relevant information needed by the public to provide comments on the proposed authorization itself. The notice contained the permissible methods of taking by harassment, means of effecting the least practicable impact on such species (

i.e.,

mitigation), measures to ensure no unmitigable adverse impact on the availability of the species or stock for taking for subsistence use, requirements pertaining to the monitoring and reporting of such taking, including requirements for the independent peer review of the proposed monitoring plan. The notice provided detail on all of these points, and, in NMFS' view, allowed the public to comment on the proposed authorization and inform NMFS' final decision. Additionally, the notice contained NMFS' preliminary findings of negligible impact and no unmitigable adverse impact.

The signing of a CAA is not a requirement to obtain an IHA. The CAA is a document that is negotiated between and signed by the industry participant, AEWC, and the Village Whaling Captains' Associations. NMFS has no role in the development or execution of this agreement. Although the contents of a CAA may inform NMFS' no unmitigable adverse impact determination for bowhead and beluga whales and ice seals, the signing of it is not a requirement. While a CAA has not been signed and a final version agreed to by industry participants, AEWC, and the Village Whaling Captains' Associations, NMFS was provided with a copy of the version ready for signature by AEWC. NMFS has reviewed the CAA and included several measures from the document which relate to marine mammals and avoiding conflicts with subsistence hunts in the IHA. Some of the conditions which have been added to the IHA include: (1) Avoiding concentrations of whales and reducing vessel speed when near whales; (2) conducting sound source verification measurements; and (3) participating in the Communication Centers. Despite the lack of a signed CAA for 2010 activities, NMFS is confident that the measures contained in the IHA will ensure no unmitigable adverse impact to subsistence users.

Comment 5:

AEWC and NSB argue that Statoil has not demonstrated that its proposed activities would take only “small numbers of marine mammals of a species or population stock,” resulting in no more than a “negligible impact” on a species or stock. In addition, NSB argues that NMFS has not adequately analyzed harassment associated with received levels of noise below 160 dB.

Response:

NMFS believes that it provided sufficient information in its proposed IHA notice (75 FR 32379; June 8, 2010) to make the small numbers and negligible impact determinations and that the best scientific information available was used to make those determinations. While some published articles indicate that certain marine mammal species may avoid seismic vessels at levels below 160 dB, NMFS does not consider that these responses rise to the level of a take as defined in the MMPA. While studies, such as Miller

et al.

(1999), have indicated that some bowhead whales may have started to deflect from their migratory path 35 km (21.7 mi) from the seismic vessel, it should be pointed out that these minor course changes are during migration and, as described in MMS' 2006 Final Programmatic Environmental Assessment (PEA), have not been seen at other times of the year and during other activities. To show the contextual nature of this minor behavioral modification, recent monitoring studies of Canadian seismic operations indicate that feeding, non-migratory bowhead whales do not move away from a noise source at an SPL of 160 dB. Therefore, while bowheads may avoid an area of 20 km (12.4 mi) around a noise source, when that determination requires a

post-survey computer analysis to find that bowheads have made a 1 or 2 degree course change, NMFS believes that does not rise to a level of a “take,” as the change in bearing is due to animals sensing the noise and avoiding passing through the ensonified area during their migration, and should not be considered as being displaced from their habitat. NMFS therefore continues to estimate “takings” under the MMPA from impulse noises, such as seismic, as being at a distance of 160 dB (re 1 μPa). As explained throughout this

Federal Register

notice, it is highly unlikely that marine mammals would be exposed to SPLs that could result in serious injury or mortality. The best scientific information indicates that an auditory injury is unlikely to occur, as apparently sounds need to be significantly greater than 180 dB for injury to occur (Southall

et al.

2007).

Regarding the small number issue raised by the AEWC and NSB, NMFS has developed a series of estimates for marine mammals that could be taken as a result of Statoil's proposed marine surveys, and the estimated takes from these proposed activities are all under five percent for any affected marine mammal species or stock (see Potential Number of Takes by Harassment section below).

Impacts to Marine Mammals

Comment 6:

AEWC notes that based on the density estimates, Statoil is predicting that an average of 2,253 and 4,234 individuals of Alaska ringed seals may be exposed to sound levels of 160 dB and above during the proposed 3D and 2D seismic surveys, respectively. AEWC and NSB state that these are by no means “small numbers” of marine mammals that will be subjected to impacts as a result of Statoil's operations.

Response:

NMFS determined that the small numbers requirement has been satisfied. Statoil has predicted that an average of 2,253 and 4,234 individuals of Alaska ringed seals may be exposed to sound levels of 160 dB and above as the result of Statoil's proposed 3D and 2D marine seismic surveys, respectively, and NMFS assumes that animals exposed to received levels above 160 dB are taken. However, because of the tendency of marine mammals to avoid the source to some degree, and the fact that both the marine mammals and the source are moving through an area, the majority of the exposures would likely occur at levels closer to 160 dB (not higher levels) and the impacts would be expected to be relatively low-level and not of a long duration. NMFS assesses “small numbers” in terms relative to the population/stock size. The Level B harassment take estimate of a total of 6,487 Alaska stock of ringed seals is a small number in relative terms, because of the nature of the anticipated responses and in that it represents only 2.81 percent of the regional stock size of that species (population > 230,000), if each “exposure” at 160 dB represents an individual ringed seal. Furthermore, as discussed below, exposure of marine mammals to received levels at 160 dB do not always constitute a “take.” Many animals may not respond to this level in a way that is considered biologically significant. Therefore, even though NMFS uses the 160 dB received level as the onset of Level B harassment for regulatory purposes, this does not mean that all animals exposed to this level or levels above 160 dB are “taken.” Additionally, NMFS believes the percentage would be even lower if animals move out of the seismic area. In these circumstances, animals that are outside of the ensonified zone (e.g., the 160 dB isopleth) would not be expected to be taken by Level B harassment.

Comment 7:

AWL, NSB, and AEWC noted that NMFS has acknowledged that permanent threshold shift (PTS) qualifies as a serious injury. Therefore, if an acoustic source at its maximum level has the potential to cause PTS and thus lead to serious injury, it would not be appropriate to issue an IHA for the activity (60 FR 28381; May 31, 1995). AEWC states that therefore an LOA is required here.

Response:

In the proposed rule to implement the process to apply for and obtain an IHA, NMFS stated that authorizations for harassment involving the “potential to injure” would be limited to only those that may involve non-serious injury (60 FR 28379; May 31, 1995). While the

Federal Register

notice cited by the commenters states that NMFS considered PTS to be a serious injury (60 FR 28379; May 31, 1995), our understanding of anthropogenic sound and the way it impacts marine mammals has evolved since then, and NMFS no longer considers PTS to be a serious injury. NMFS has defined “serious injury” in 50 CFR 216.3 as “* * * any injury that will likely result in mortality.” There are no data that suggest that PTS would be likely to result in mortality, especially the limited degree of PTS that could hypothetically be incurred through exposure of marine mammals to seismic airguns at the level and for the duration that are likely to occur in this action.

Further, as stated several times in this document and previous

Federal Register

notices for seismic activities, 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). PTS is thought to occur several decibels above that inducing mild temporary threshold shift (TTS), the mildest form of hearing impairment (a non-injurious effect). NMFS concluded that cetaceans and pinnipeds should not be exposed to pulsed underwater noise at received levels exceeding, respectively, 180 and 190 dB re 1 μPa (rms). The established 180 and 190 dB re 1 μPa (rms) criteria 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 later in this document, 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 Pa rms (Southall

et al.

2007). Additionally, NMFS has required monitoring and mitigation measures to negate the possibility of marine mammals being seriously injured as a result of Statoil's activities. In the proposed IHA, NMFS determined that Statoil's activities are unlikely to even result in TTS. Based on this determination and the explanation provided here, PTS is also not expected. Therefore, an IHA is appropriate.

Comment 8:

AWL, NSB, and AEWC state that NMFS has not adequately considered whether marine mammals may be harassed at received levels significantly lower than 160 dB and that NMFS did not use the best scientific evidence in setting the sound levels against which take was assessed. They state that NMFS calculated harassment from Statoil's proposed surveying based on the exposure of marine mammals to sounds at or above 160 dB and that this uniform approach to harassment does not take into account known reactions of marine mammals in the Arctic to levels of noise far below 160 dB. These comments state that bowhead, gray, killer, and beluga whales and harbor porpoise react to sounds lower than 160 dB.

Citing several papers on killer whales and harbor porpoise, Dr. Bain states that major behavioral changes of these animals appear to be associated with received levels of around 135 dB re 1 μPa, and that minor behavioral changes can occur at received levels from 90-110 dB re 1 μPa or lower. He also states that belugas have been observed to respond to icebreakers by swimming rapidly away at distances up to 80 km,

where received levels were between 94 and 105 dB re 1 μPa. Belugas exhibited minor behavioral changes such as changes in vocalization, dive patterns, and group composition at distances up to 50 km (NRC 2003), where received levels were likely around 120 dB.

The AWL states that harbor porpoises have been shown to be particularly responsive to sound, exhibiting behavioral changes, including exclusion from an area, at received levels of 90-110 dB or lower (with received levels around 70-90 dB), depending on experience with the noise source and environmental context. The AWL listed a number of papers but did not point out the source of its statement. The AWL also states that multiple studies confirm the sensitivity of beluga whales, and that they are known to alter their migration paths in response to icebreaker noise at received levels as low as 80 dB, and that belugas have been observed to respond to icebreakers by swimming rapidly away at distances up to 80 km.

AEWC also states that in conducting scoping on its national acoustic guidelines for marine mammals, NMFS noted that the existing system for determining take (i.e., the 160 dB mark) “considers only the sound pressure level of an exposure but not its other attributes, such as duration, frequency, or repetition rate, all of which are critical for assessing impacts on marine Mammals” and “also assumes a consistent relationship between rms (root-mean-square) and peak pressure values for impulse sounds, which is known to be inaccurate under certain (many) conditions” (70 FR 1871, 1873; January 11, 2005). Thus, NMFS itself has recognized that 160 dB (rms) is not an adequate measure. AEWC argues that current scientific research establishes that 120 dB (rms) is a more appropriate measure for impacts to marine mammals.

Response:

The best information available to date for reactions by bowhead whales to noise, such as seismic, is based on the results from the 1998 aerial survey (as supplemented by data from earlier years) as reported in Miller

et al.

(1999). In 1998, bowhead whales below the water surface at a distance of 20 km (12.4 mi) from an airgun array received pulses of about 117-135 dB re 1 μPa rms, depending upon propagation. Corresponding levels at 30 km (18.6 mi) were about 107-126 dB re 1 μPa rms. Miller

et al.

(1999) surmise that deflection may have begun about 35 km (21.7 mi) to the east of the seismic operations, but did not provide SPL measurements to that distance and noted that sound propagation has not been studied as extensively eastward in the alongshore direction, as it has northward, in the offshore direction. Therefore, while this single year of data analysis indicates that bowhead whales may make minor deflections in swimming direction at a distance of 30-35 km (18.6-21.7 mi), there is no indication that the SPL where deflection first begins is at 120 dB; it could be at another SPL lower or higher than 120 dB. Miller

et al.

(1999) also note that the received levels at 20-30 km (12.4-18.6 mi) were considerably lower in 1998 than have previously been shown to elicit avoidance in bowheads exposed to seismic pulses. However, the seismic airgun array used in 1998 was larger than the ones used in 1996 and 1997. Therefore, NMFS believes that it cannot scientifically support adopting any single SPL value below 160 dB and apply it across the board for all species and in all circumstances. Second, these minor course changes occurred during migration and, as indicated in MMS' 2006 PEA, have not been seen at other times of the year and during other activities. Third, as stated in the past, NMFS does not believe that minor course corrections during a migration equate to “take” under the MMPA. This conclusion is based on controlled exposure experiments conducted on migrating gray whales exposed to the U.S. Navy's low frequency sonar (LFA) sources (Tyack 2009). When the source was placed in the middle of the migratory corridor, the whales were observed deflecting around the source during their migration. However, such minor deflection is considered not to be biologically significant. To show the contextual nature of this minor behavioral modification, recent monitoring studies of Canadian seismic operations indicate that when, not migrating, but involved in feeding, bowhead whales do not move away from a noise source at an SPL of 160 dB. Therefore, while bowheads may avoid an area of 20 km (12.4 mi) around a noise source, when that determination requires a post-survey computer analysis to find that bowheads have made a 1 or 2 degree course change, NMFS believes that does not rise to a level of a “take.” NMFS therefore continues to estimate “takings” under the MMPA from impulse noises, such as seismic, as being at a distance of 160 dB (re 1 µPa). Although it is possible that marine mammals could react to any sound levels detectable above the ambient noise level within the animals' respective frequency response range, this does not mean that such animals would react in a biologically significant way. According to experts on marine mammal behavior, the degree of reaction which constitutes a “take,” i.e., a reaction deemed to be biologically significant that could potentially disrupt the migration, breathing, nursing, breeding, feeding, or sheltering, etc., of a marine mammal is complex and context specific, and it depends on several variables in addition to the received level of the sound by the animals. These additional variables include, but are not limited to, other source characteristics (such as frequency range, duty cycle, continuous vs. impulse vs. intermittent sounds, duration, moving vs. stationary sources, etc.); specific species, populations, and/or stocks; prior experience of the animals (naive vs. previously exposed); habituation or sensitization of the sound by the animals; and behavior context (whether the animal perceives the sound as predatory or simply annoyance), etc. (Southall

et al.

2007). Furthermore, the behavioral responses by harbor porpoises (pinger) and beluga whales (icebreaker) were to non-impulse noises. For non-impulse noise sources, research shows that in general, the threshold that induces behavioral responses among animals tends to be much lower. Therefore, NMFS uses 120 dB as the onset for behavioral harassment for non-impulse noises but 160 dB for impulse noises. The noises from the proposed marine seismic survey from airgun arrays are pulses.

The references cited in the comment letters address different source characteristics (continuous sound rather than impulse sound that are planned for the proposed seismic survey) or species (killer whales and harbor porpoises) that rarely occur in the proposed Arctic action area. Some information about the responses of bowhead and gray whales to seismic survey noises has been acquired through dedicated research and marine mammal monitoring studies conducted during prior seismic surveys. Detailed descriptions regarding behavioral responses of these marine mammals to seismic sounds are available (

e.g.,

Richardson

et al.

1995; review by Southall

et al.

2007), and are also discussed in this document. Additionally, as Statoil does not intend to use ice-breakers during its operations, statements regarding beluga reactions to icebreaker noise are not relevant to this activity.

Regarding the last point raised in this comment by AEWC, NMFS recognizes the concern. However, NMFS does not agree with AEWC's statement that current scientific research establishes that 120 dB (rms) is a more appropriate measure for impacts to marine mammals

for reasons noted above. Based on the information and data summarized in Southall

et al.

(2007), and on information from various studies, NMFS believes that the onset for behavioral harassment is largely context dependent, and there are many studies showing marine mammals do not show behavioral responses when exposed to multiple pulses at received levels above 160 dB re 1 μPa (e.g., Malme

et al.

1983; Malme

et al.

1984; Richardson

et al.

1986; Akamatsu

et al.

1993; Madsen and Møhl 2000; Harris

et al.

2001; Miller

et al.

2005). Therefore, although using a uniform SPL of 160-dB for the onset of behavioral harassment for impulse noises may not capture all of the nuances of different marine mammal reactions to sound, it is an appropriately conservative way to manage and regulate anthropogenic noise impacts on marine mammals. Therefore, unless and until an improved approach is developed and peer-reviewed, NMFS will continue to use the 160-dB threshold for determining the level of take of marine mammals by Level B harassment for impulse noise (such as from airguns).

Comment 9:

NSB and AWL note that this IHA, as currently proposed, is based on uncertainties that are not allowed under the MMPA. Citing comments made by NMFS on recent MMS Lease Sale Environmental Impact Statements, NSB notes that NMFS stated that without more current and thorough data on the marine mammals in the Chukchi Sea and their use of these waters, it would be difficult to make the findings required by the MMPA. AWL points out that NMFS specifically observed that activities “occurring near productive forage areas such as the Hanna Shoal” or “along migratory corridors” are most likely to encounter and impact marine mammals. AWL states that Statoil's proposed surveying will likely take place proximate to the Hanna Shoal, which is a feeding ground for gray whales and is within the pathway for migrating bowheads. AWL furthers states that the lack of information runs up against the precautionary nature of the MMPA, therefore, NMFS cannot claim the lack of available information justifies its decision, and that NMFS has an affirmative obligation to find that impacts are no more than “negligible” and limited to the harassment of only “small numbers of marine mammals.” NSB notes that NMFS noted that the “continued lack of basic audiometric data for key marine mammal species” that occur throughout the Chukchi Sea inhibits the “ability to determine the nature and biological significance of exposure to various levels of both continuous and impulsive oil and gas activity sounds.”

Response:

While there may be some uncertainty on the current status of some marine mammal species in the Chukchi Sea and on impacts to marine mammals from seismic surveys, the best available information supports our findings. NMFS is currently proposing to conduct new population assessments for Arctic pinniped species, and current information is available on-line through the Stock Assessment Reports (SARs). Moreover, NMFS has required the industry to implement a monitoring and reporting program to collect additional information concerning effects to marine mammals.

In regard to impacts, there is no indication that seismic survey activities are having a long-term impact on marine mammals. For example, apparently, bowhead whales continued to increase in abundance during periods of intense seismic activity in the Chukchi Sea in the 1980s (Raftery

et al.

1995; Angliss and Outlaw 2007), even without implementation of current mitigation requirements. As a result, NMFS believes that seismic survey noise in the Arctic will affect only small numbers of and have no more than a negligible impact on affected marine mammal species or stocks in the Chukchi Sea. As explained in this document and based on the best available information, NMFS has determined that Statoil's activities will affect only small numbers of marine mammal species or stocks, will have a negligible impact on affected species or stocks, and will not have an unmitigable adverse impact on subsistence uses of the affected species or stocks.

Comment 10:

AWL and NSB state that the standard for determining whether an IHA is appropriate is exceptionally protective. If there is even the possibility of serious injury, NMFS must establish that the “potential for serious injury can be negated through mitigation requirements” (60 FR 28380; May 31, 1995). Reports from previous surveys, however, indicate that, despite monitored exclusion zones, marine mammals routinely stray too close to the airguns. AEWC states that the safety radii proposed by Statoil do not negate injury.

Response:

As has already been stated in the

Federal Register

notice for the proposed IHA (75 FR 32379; June 8, 2010), recent scientific information has indicated that received noise levels need to be significantly higher than 190 dB to cause injury to marine mammals (see Southall

et al.

2007). Therefore, the 180- and 190-dB safety zones are conservative.

The source vessel will be traveling at speeds of about 1-5 knots (1.9-9.3 km/hr). With a 180-dB safety range of 160 m (525 ft), the vessel will have moved out of the safety zone within a few minutes. As a result, during underway survey operations, MMOs are instructed to concentrate on the area ahead of the vessel, not behind the vessel where marine mammals would need to be voluntarily swimming towards the vessel to enter the 180-dB zone. In fact, in some of NMFS' IHAs issued for scientific seismic operations, shutdown is not required for marine mammals that approach the vessel from the side or stern in order to ride the bow wave or rub on the seismic streamers deployed from the stern (and near the airgun array) as some scientists consider this a voluntary action on the part of an animal that is not being harassed or injured by seismic noise. While NMFS concurs that shutdowns are not likely warranted for these voluntary approaches, in the Arctic Ocean, all seismic surveys are shutdown or powered down for all marine mammal close approaches. Also, in all seismic IHAs, including Statoil's IHA, NMFS requires that the safety zone be monitored for 30 min prior to beginning ramp-up to ensure that no marine mammals are present within the safety zones. Implementation of ramp-up is required because it is presumed it would allow marine mammals to become aware of the approaching vessel and move away from the noise, if they find the noise annoying. Data from 2007 and 2008, when Shell had support boats positioned 1 km (0.62 mi) on each side of the 3D seismic vessel, suggest that marine mammals do in fact move away from an active source vessel. In those instances, more seals were seen from the support vessels than were seen from the source vessels during active seismic operations. Additionally, research has indicated that some species tend to avoid areas of active seismic operations (e.g., bowhead whales, see Richardson

et al.

1999).

NMFS has determined that an IHA is the proper authorization required to cover Statoil's survey. As described in other responses to comments in this document, NMFS does not believe that there is a risk of serious injury or mortality from these activities. The monitoring reports from 2006, 2007, 2008, and 2009 do not note any instances of serious injury or mortality (Patterson

et al.

2007; Funk

et al.

2008; Ireland

et al.

2009; Reiser

et al.

2010). Additionally, NMFS is confident it has met all of the requirements of section 101(a)(5)(D) of the MMPA (as described

throughout this document) and therefore can issue an IHA to Statoil for its survey operations in 2010.

Comment 11:

AEWC notes that stranded marine mammals or their carcasses are also a sign of injury. NMFS states in its notice that it “does not expect any marine mammal will * * * strand as a result of the proposed seismic survey” (75 FR 32379; June 8, 2010). In reaching this conclusion, NMFS claims that strandings have not been recorded for the Beaufort and Chukchi Seas. AEWC states that the Department of Wildlife Management of NSB has completed a study documenting 25 years worth of stranding data and showing that five dead whales were reported in 2008 alone in comparison with the five dead whales that were reported in the same area over the course of 25 years (Rosa 2009).

In light of the increase in seismic operations in the Arctic since 2006, AEWC says that NSB's study raises serious concerns about the impacts of these operations and their potential to injure marine mammals. AEWC states that while they think this study taken together with the June 2008 stranding of “melon headed whales off Madagascar that appears to be associated with seismic surveys” (75 FR 32379; June 8, 2010) demonstrate that seismic operations have the potential to injure marine mammals beyond beaked whales (and that Statoil needs to apply for an LOA for its operations), certainly NSB's study shows that direct injury of whales is on-going. AEWC states that these direct impacts must be analyzed and explanations sought out before additional activities with the potential to injure marine mammals are authorized, and that NMFS must explain how, in light of this new information, Statoil's application does not have the potential to injure marine mammals.

Response:

NMFS has reviewed the information provided by AEWC regarding marine mammal strandings in the Arctic. The Rosa (2009) paper cited by AEWC does not provide any evidence linking the cause of death for the bowhead carcasses reported in 2008 to seismic operations. Additionally, the increased reporting of carcasses in the Arctic since 2006 may also be a result of increased reporting effort and does not necessarily indicate that there were fewer strandings prior to 2008. Marine mammal observers (MMOs) aboard industry vessels in the Beaufort and Chukchi Seas have been required to report sightings of injured and dead marine mammals to NMFS as part of the IHA requirements only since 2006.

Regarding the June 2008 stranding of melon headed whales off Madagascar, information available to NMFS at this time indicates that the seismic airguns were not active around the time of the stranding. While the Rosa (2009) study does present information regarding the injury of whales in the Arctic, it does not link the cause of the injury to seismic survey operations. As NMFS has stated previously, the evidence linking marine mammal strandings and seismic surveys remains tenuous at best. Two papers, Taylor

et al.

(2004) and Engel

et al.

(2004) reference seismic signals as a possible cause for a marine mammal stranding.

Taylor

et al.

(2004) noted two beaked whale stranding incidents related to seismic surveys. The statement in Taylor

et al.

(2004) was that the seismic vessel was firing its airguns at 1300 hrs on September 24, 2004, and that between 1400 and 1600 hrs, local fishermen found live stranded beaked whales 22 km (12 nm) from the ship's location. A review of the vessel's trackline indicated that the closest approach of the seismic vessel and the beaked whales stranding location was 18 nm (33 km) at 1430 hrs. At 1300 hrs, the seismic vessel was located 25 nm (46 km) from the stranding location. What is unknown is the location of the beaked whales prior to the stranding in relation to the seismic vessel, but the close timing of events indicates that the distance was not less than 18 nm (33 km). No physical evidence for a link between the seismic survey and the stranding was obtained. In addition, Taylor

et al.

(2004) indicates that the same seismic vessel was operating 500 km (270 nm) from the site of the Galapagos Island stranding in 2000. Whether the 2004 seismic survey caused the beaked whales to strand is a matter of considerable debate (see Cox

et al.

2006). However, these incidents do point to the need to look for such effects during future seismic surveys. To date, follow up observations on several scientific seismic survey cruises have not indicated any beaked whale stranding incidents.

Engel

et al.

(2004), in a paper presented to the IWC in 2004 (SC/56/E28), mentioned a possible link between oil and gas seismic activities and the stranding of 8 humpback whales (7 off the Bahia or Espirito Santo States and 1 off Rio de Janeiro, Brazil). Concerns about the relationship between this stranding event and seismic activity were raised by the International Association of Geophysical Contractors (IAGC). The IAGC (2004) argues that not enough evidence is presented in Engel

et al.

(2004) to assess whether or not the relatively high proportion of adult strandings in 2002 is anomalous. The IAGC contends that the data do not establish a clear record of what might be a “natural” adult stranding rate, nor is any attempt made to characterize other natural factors that may influence strandings. As stated previously, NMFS remains concerned that the Engel

et al.

(2004) article appears to compare stranding rates made by opportunistic sightings in the past with organized aerial surveys beginning in 2001. If so, then the data are suspect.

Additionally, if bowhead and gray whales react to sounds at very low levels by making minor course corrections to avoid seismic noise, and mitigation measures require Statoil to ramp-up the seismic array to avoid a startle effect, strandings such as those observed in the Bahamas in 2000 are highly unlikely to occur in the Arctic Ocean as a result of seismic activity. Therefore, NMFS does not expect any marine mammals will incur serious injury or mortality as a result of Statoil's 2010 survey operations, so an LOA is not needed.

Lastly, Statoil is required to report all sightings of dead and injured marine mammals to NMFS and to notify the Marine Mammal Health and Stranding Response Network. However, Statoil is not permitted to conduct necropsies on dead marine mammals. Necropsies can only be performed by people authorized to do so under the Marine Mammal Health and Stranding Response Program MMPA permit. NMFS is currently considering different methods for marking carcasses to reduce the problem of double counting. However, a protocol has not yet been developed, so marking is not required in the IHA.

Comment 12:

AEWC, NSB, and Dr. Bain state that research is increasingly showing that marine mammals may remain within dangerous distances of seismic operations rather than leave a valued resource such as a feeding ground (see Richardson 2004). The International Whaling Commission (IWC) scientific committee has indicated that the lack of deflection by feeding whales in Camden Bay (during Shell Offshore Inc. and Shell Gulf of Mexico Inc.'s seismic activities) likely shows that whales will tolerate and expose themselves to potentially harmful levels of sound when needing to perform a biologically vital activity, such as feeding (mating, giving birth, etc.). Thus, the noise from Statoil's proposed operations could injure marine mammals if they are close enough to the source. NSB further states that NMFS has not adequately analyzed the potential for serious injury.

Response:

If marine mammals, such as bowhead whales, remain near a seismic operation to perform a biologically vital activity, such as feeding, depending on the distance from the vessel and the size of the 160-dB radius, the animals may experience some Level B harassment. A detailed analysis on potential impacts of anthropogenic noise (including noise from seismic airguns and other active acoustic sources used in geophysical surveys) is provided in the proposed IHA (75 FR 32379; June 8, 2010) and in this document. Based on the analysis, NMFS believes that it is unlikely any animals exposed to noise from Statoil's proposed marine surveys would be exposed to received levels that could cause TTS (a non-injurious Level B harassment). Therefore, it is even less likely that marine mammals would be exposed to levels of sound from Statoil's activity that could cause PTS (a non-lethal Level A harassment).

In addition, depending on the distance of the animals from the vessel and the number of individual whales present, certain mitigation measures are required to be implemented. If an aggregation of 12 or more mysticete whales are detected within the 160-dB radius, then the airguns must be shutdown until the aggregation is no longer within that radius. Additionally, if any whales are sighted within the 180-dB radius or any pinnipeds are sighted within the 190-dB radius of the active airgun array, then either a power-down or shutdown must be implemented immediately. For the reasons stated throughout this document, NMFS has determined that Statoil's operations will not injure, seriously injure, or kill marine mammals.

Comment 13:

AEWC, AWL, and Dr. Bain state that NMFS does little to assess whether Level A harassment is occurring as a result of the deflection of marine mammals as a result of Statoil's proposed operations. Deflected marine mammals may suffer impacts due to masking of natural sounds including calling to others of their species, physiological damage from stress and other non-auditory effects, harm from pollution of their environment, tolerance, and hearing impacts (

see

Nieukirk

et al.

2004). Not only do these operations disrupt the animals' behavioral patterns, but they also create the potential for injury by causing marine mammals to miss feeding opportunities, expend more energy, and stray from migratory routes when they are deflected.

Response:

See the response to comment 8 regarding the potential for injury. The paper cited by AEWC (Nieukirk

et al.

2004) tried to draw linkages between recordings of fin, humpback, and minke whales and airgun signals in the western North Atlantic; however, the authors note the difficulty in assessing impacts based on the data collected. The authors also state that the effects of airgun activity on baleen whales is unknown and then cite to Richardson

et al.

(1995) for some possible effects, which AEWC lists in their comment. There is no statement in the cited study, however, about the linkage between deflection and these impacts. While deflection may cause animals to expend extra energy, there is no evidence that this deflection is causing a significant behavioral change that will adversely impact population growth. In fact, bowhead whales continued to increase in abundance during periods of intense seismic in the Chukchi Sea in the 1980s (Raftery

et al.

1995; Angliss and Outlaw 2007). Therefore, NMFS does not believe that injury will occur as a result of Statoil's activities. Additionally, Statoil's total data acquisition activities would only ensonify 531 km

2

of the Chukchi Sea to received levels above 160 dB (0.089% of the entire Chukchi Sea). Therefore, based on the small area of the Chukchi Sea where Statoil will utilize airguns, it is unlikely that marine mammals will need to expend much extra energy to locate prey, or will have reduced foraging opportunities.

Comment 14:

Citing Erbe (2002), AEWC notes that any sound at some level can cause physiological damage to the ear and other organs and tissues. Placed in a context of an unknown baseline of sound levels in the Chukchi Sea, it is critically important that NMFS take a precautionary approach to permitting additional noise sources in this poorly studied and understood habitat. Thus, the best available science dictates that NMFS use a more cautious approach in addressing impacts to marine mammals from seismic operations. AWL also states noise exposure is likely to result in stress, and stress can impair an animal's immune system.

Response:

The statement from Erbe (2002) does not take into account mitigation measures required in the IHA to reduce impacts to marine mammals. As stated throughout this document, based on the fact that Statoil will implement mitigation measures (

i.e.,

ramp-up, power-down, shutdown, etc.), NMFS does not believe that there will be any injury or mortality of marine mammals as a result of Statoil's operations.

Comment 15:

AEWC states that in making its negligible impact determination, NMFS failed to consider several impacts: (1) Displacing marine mammals from feeding areas; (2) non-auditory, physiological effects, namely stress; (3) the possibility of vessel strikes needs to be considered in light of scientific evidence of harm from ship traffic to marine mammals; (4) impacts to marine mammal habitat, including pollution of the marine environment and the risk of oil spills, toxic, and nontoxic waste being discharged; (5) impacts to fish and other food sources upon which marine mammals rely; and (6) specific marine mammals that will be taken, including their age, sex, and reproductive condition. The first issue was also raised by Dr. Bain.

Response:

NMFS does not agree that these impacts were not considered. First, the area that would be ensonified by Statoil's proposed open water seismic surveys represents a small fraction of the total habitat of marine mammals in the Chukchi Sea. In addition, as the survey vessel is constantly moving, the ensonified zone where the received levels exceed 160 dB re 1 μPa (rms), which is estimated to be approximately 531 km

2

at any given time, is constantly moving. Therefore, the duration during which marine mammals would potentially avoid the ensonified area would be brief. Therefore, NMFS does not believe marine mammals would be displaced from their customary feeding areas as a result of Statoil's proposed seismic surveys.

Second, non-auditory, physiological effects, including stress, were analyzed in the Notice of Proposed IHA (75 FR 32379; June 8, 2010). No single marine mammal is expected to be exposed to high levels of sound for extended periods based on the size of the airgun array to be used by Statoil and the fact that an animal would need to swim close to, parallel to, and at the same speed as the vessel to incur several high intensity pulses. This also does not take into account the mitigation measures described later in this document.

Third, impacts resulting from vessel strikes and habitat pollution and impacts to fish were fully analyzed in NMFS' 2010 Final EA for Shell and Statoil's open water marine and seismic activities (NMFS 2010). Additionally, the proposed IHA analyzed potential impacts to marine mammal habitat, including prey resources. That analysis noted that while mortality has been observed for certain fish species found in extremely close proximity to the airguns, Sætre and Ona (1996) concluded that mortality rates caused by

exposure to sounds are so low compared to natural mortality that issues relating to stock recruitment should be regarded as insignificant. For the sixth point, please see the response to comment 4. The age, sex, and reproductive condition must be provided when possible. However, this is often extremely difficult to predict. Additional mitigation measures for bowhead cow/calf pairs, such as monitoring the 120-dB radius and requiring shutdown when 4 or more cow/calf pairs enter that zone, were considered and required for this survey.

Comment 16:

Stating that airgun noise can cause direct injury to marine mammals, Dr. Bain points out that (1) “airgun arrays do not project noise equally in all directions,” and that “beams formed by the arrays can cause an animal moving from high exposure toward lower exposure to move toward the travel path of the seismic survey vessel, ultimately resulting in higher exposure;” (2) “the flight path of animals moving away is not always optimal. Animals may begin by swimming directly away from the array. However, if the array is moving toward them at faster than their sustained swimming speed, the array will approach them. After a while, animals may change tactics to moving orthogonal to the direction of array movement. While orthogonal movement will ultimately reduce the maximum noise level experienced, it allows the seismic survey vessel to close on their location faster. Shortly before the animals are orthogonal to the survey vessel, they may turn and head in the opposite direction of the survey vessel, briefly approaching it, but then increasing the distance between them at close to the highest possible rate;” (3) if pinnipeds do not move away, “the seismic survey vessel can approach them,” that “orienting behavior is interrupted with occasional swimming behavior. While the swims can increase the distance between the pinniped and the vessels track line, submerging exposes the ears to the full intensity of the received pulses”; (4) marine mammals may tolerate injury while feeding, because “[f]ishers and NMFS personnel have shot animals and used seal bombs to inflict pain in unsuccessful efforts to deter depredation,” and that “predators sometimes swallow hooks along with their prey.”

Response:

While NMFS recognizes that intense noise exposure can cause direct harm to marine mammals, as discussed in the

Federal Register

for the proposed IHA (75 FR 32379; June 8, 2010) and in this document, the intensities of received levels need to be significantly higher or the exposure duration be significantly longer than those at issue here to cause TTS, let alone injury. Please refer to these documents and the EA for a detailed discussion on the noise impacts to marine mammals. The points Dr. Bain made in his comment do not support his argument. Regarding the first point, Dr. Bain is correct that airgun arrays do not project noise equally in all directions. As an airgun is designed to project its impulse downward, most of its acoustic energy is confined in downward beams. Although there is a significant amount of energy being propagated horizontally, especially close by, the intensity of noise is much less when compared to downward acoustic intensities. As acoustic energy travels from its source outwards, an animal moving from higher received levels to lower received levels is generally moving away from the source (the seismic airgun). At long distances where certain higher received levels form due to multi-path propagation and refraction, movement from higher received levels to lower received levels may not necessarily mean that the animal is moving away from the source. However, at this long distance, the received levels are expected to be much lower (below 160 dB) and the distances are expected to be far beyond the zone of influence. This response also addresses part of Dr. Bain's second point regarding animal movement. In addition, the seismic vessel is prohibited from approaching marine mammals within specific safety zones (180 dB isopleths at 2,500 m for cetaceans and 190 dB isopleths at 700 m for pinnipeds). Therefore, to address Dr. Bain's second and third points, regardless of whether animals are moving or not, the seismic vessel is not allowed to approach marine mammals within the designated safety zones. Finally, Dr. Bain's last point regarding the use of seal bombs to inflict pain and “predators sometimes swallow hooks along with their prey,” is irrelevant to our MMPA findings for Statoil's seismic activities. Statoil's activities do not involve the use of seal bombs and there is no connection between predators swallowing hooks along with their prey and the use of seismic airguns.

Comment 17:

Dr. Bain states that “[b]ubble formation may be caused by moderate levels of noise. Rectified diffusion (Crum and Mao 1996) and decompression sickness (Jepson

et al.

2003) are two postulated mechanisms for this. In rectified diffusion, acoustic energy causes gas to diffuse from the blood into small bubbles. Since bubbles are smaller when compressed, and larger when rarified, the net diffusion is into the bubble, leading to bubble growth in blood, fat, or other tissues, to injurious size.” He also states that behaviorally mediated decompression sickness is considered more likely than rectified diffusion as the cause of bubble formation (Cox

et al.

2006).

Response:

Although it has been suggested that bubble formation due to nitrogen gas bubble growth, resulting in effects similar to decompression sickness in humans (Jepson

et al.

2003; Fernández

et al.

2004, 2005), may be the cause for at least some of the beaked whale mass strandings that occurred in association with mid-frequency active sonar operations, the hypothesis remains untested and the acoustic causative mechanism remains unknown today. In addition, the pathway concerning nitrogen supersaturation levels for deep-diving species of interest, including beaked whales, are based on theoretical models (Houser

et al.

2001; Southall

et al.

2007), and no unequivocal support for any of the pathways presently exists.

Finally, the suspected bubble formation by acoustic sources, and the induced atypical diving pattern that are theorized to cause decompression sickness in deep diving marine mammals (such as beaked whales), were mostly speculated to be caused by tactical mid-frequency sonar associated with military exercises, not by airgun impulses from seismic surveys.

Comment 18:

While discussing impacts specific to the Chukchi Sea, Dr. Bain states that displacement from feeding areas is an even greater concern for harbor porpoises. Dr. Bain adds his personal observations that due to their small size, going without food for a few days can be fatal to harbor porpoises; and that harbor porpoises in Juan de Fuca Strait and Haro Strait experienced a doubling of mortality rates following exposure to a series of mid-frequency sonar exercise.

Response:

Dr. Bain did not provide any details to support his observations in the comments, and NMFS is not aware of any studies that support Dr. Bain's claim. Because there is no information showing that the doubling of mortality rate in harbor porpoises in Juan de Fuca Strait and Haro Strait is related to the mid-frequency sonar exercise, a causative relationship between the two cannot be derived.

As discussed previously, due to the limited area (531 km

2

for an area ensonified by received levels higher than 160 dB) that would be ensonified by the seismic airguns and the relatively short duration of the surveys (total of 60 days), and the constant movement of the

seismic vessel, it is unlikely that harbor porpoises or any other marine mammals would be displaced for any significant amount of time by the proposed open water seismic surveys. Therefore, even if marine mammals temporarily avoid an area that might be their feeding ground due to the seismic survey, the duration of the displacement is expected to be short, so that animals will not lose feeding opportunities for more than a few hours up to a day. In addition, the majority of sound sources from airgun arrays are in the low-frequency range, which is outside harbor porpoises' sensitive hearing range. Therefore, even though the intensities of seismic impulses are high, these impulses may not be perceived as intense noise by harbor porpoises due to their high-frequency hearing.

Comment 19:

AEWC states that in assessing the level of take and whether it is negligible, NMFS relied on flawed density estimates that call into question all of NMFS' preliminary conclusions. AEWC states that density data are lacking or outdated for almost all marine mammals that may be affected by Statoil's operations in the Chukchi Sea. AEWC argues that NMFS' guess at the number of beluga and bowhead whales relies on a study from Moore

et al.

(2000), which was ten years old. AEWC says that the estimate is contrary to the best available scientific information on beluga whale presence in the Chukchi Sea. AEWC points out that the most recent Alaska Marine Mammal Stock Assessment dates from 2009 and was issued in February 2010 (Allen and Angliss 2010), but Statoil's IHA application relied on the 2008 Alaska Marine Mammal Stock Assessment (Angliss and Allen 2009). AEWC further states that Allen and Angliss (2010) likely underestimated the size of the eastern Chukchi Sea beluga whale stock.

AEWC also notes that the density of bowhead whales was derived from the same ten-year-old report (Moore

et al.

2000) as was used to calculate beluga whale densities. AEWC points out that NMFS makes no mention of the most recent Alaska Marine Mammal Stock Assessment which was released this year, and that the Assessment cites to a 2003 study that documented bowheads “in the Chukchi and Bering Seas in the summer” that are “thought to be a part of the expanding Western Arctic stock” (Allen and Angliss 2010). While a study published in 2003 still is not a sufficient basis for a 2009 density analysis, this study does show that additional information is available that indicates that the number of bowhead whales in the Chukchi may be higher than estimated by NMFS. NSB also points out that Statoil references aerial surveys conducted by Shell and ConocoPhilips between 2006 and 2008 occurred exclusively in nearshore areas and not within Statoil's proposed operation area.

Response:

As required by the MMPA implementing regulations at 50 CFR 216.102(a), NMFS has used the best scientific information available in assessing the level of take and whether the take by harassment will have a negligible impact on affect species or stocks. As far as the best scientific information is concerned, NMFS still considers Moore et al. (2000) to provide the best density estimate for the eastern Chukchi Sea population of beluga whales. The Alaska Marine Mammal Stock Assessment reports (Angliss and Allen 2009; Allen and Angliss 2010) do not report density estimates of the beluga whale population, they provide population estimates of marine mammal species and stocks. Furthermore, for the eastern Chukchi Sea stock of beluga whales, Allen and Angliss (2010) and Angliss and Allen (2009) provide the same average estimates of 3,710 individuals, therefore, even though Statoil used an earlier version of the Alaska Marine Mammal Stock Assessment Report, its number is the same as the 2010 report.

Similarly, the Alaska Marine Mammal Stock Assessment only reports the abundance and population size, it does not provide density estimates of marine mammals in the proposed project area. The 2003 study noted by AEWC in the bowhead whale Alaska Marine Mammal SAR discusses distribution, not density (Rugh

et al.

2003). It was not cited because it is not useful for deriving density estimates. Therefore, density estimates for bowhead and beluga whales using Moore

et al.

(2000) are based on the best available science.

Although most data used for marine mammal density are from Moore

et al.

(2000), information from other sources, wherever available, such as aerial surveys conducted by Shell and ConocoPhilips between 2006 and 2008 (Haley

et al.

2009), were also used to fill data gaps.

Comment 20:

AEWC states that NMFS fails to explain how and why it reaches various conclusions in calculating marine mammal densities and what the densities are actually estimated to be once calculated. One example is NMFS' reliance on Moore

et al.

(2000) in making its density determinations. This study documented sightings of marine mammals but did not estimate the total number of animals present. AEWC states that NMFS's practices have resulted in entirely arbitrary calculations of the level of take of marine mammals and whether such takes constitute “small numbers” or a “negligible impact” as a result of Statoil's proposal.

Response:

All densities used in calculating estimated take of marine mammals based on the described operations are shown in Tables 2 and 3 of Statoil's application. Moore

et al.

(2000) provides line transect effort and sightings from aerial surveys for cetaceans in the Chukchi Sea. Species specific correction factors for animals that were not at the surface or that were at the surface but were not sighted [g(0)] and animals not sighted due to distance from the survey trackline [f(0)] used in the equation were taken from reports or publications on the same species or similar species (if no values were available for a given species) that used the same survey platform. Additional explanations regarding the calculations of marine mammal densities are provided in Statoil's application and the

Federal Register

notice for the proposed IHA (75 FR 32379; June 8, 2010). Therefore, NMFS believes the methodology used in take calculations of the level of take of marine mammals is scientifically well supported.

Comment 21:

AEWC is opposed to NMFS using “survey data” gathered by industry while engaging in oil and gas related activities and efforts to document their take of marine mammals. AEWC points out that such industry “monitoring” is designed to document the level of take occurring from the operation (see 75 FR 32379 and Statoil's 4MP). AEWC argues that putting aside whether the methodologies employed are adequate for this purpose, they certainly are not adequate for assessing the density or presence of marine mammals that typically avoid such operations.

Response:

In making its determinations, NMFS uses the best scientific information available, as required by the MMPA implementing regulations. For some species, density estimates from sightings surveys, as well as from “industry surveys”, were provided in the text of Statoil's application and the Notice of Proposed IHA for purposes of comparison. However, where information was available from sightings surveys (e.g., Moore

et al.

2000; Bengtson

et al.

2005), those estimates were used to calculate take. Data collected on industry vessels were only used when no other information was available. Additionally, while some Arctic marine mammal species have shown fleeing responses to seismic airguns, data is also collected on

these vessels during periods when no active seismic data collection is occurring.

Comment 22:

AEWC states that as a general matter, when it comes to NMFS assessing the various stocks of marine mammals under the MMPA, it cannot use outdated data i.e., “abundance estimates older than 8 years” because of the “decline in confidence in the reliability of an aged abundance estimate” (Angliss and Allen 2009) and the agency is thus unable to reach certain conclusions. Similarly, here, where data are outdated or nonexistent, NMFS should decide it cannot reach the necessary determinations. AEWC argues that these flaws in NMFS' analysis render the agency's preliminary determinations about the level of harassment and negligible impacts completely arbitrary.

Response:

The statements quoted by AEWC from Angliss and Allen (2009) are contained in species SARs where abundance estimates are older than 8 years. However, the full statement reads as follows: “However, the 2005 revisions to the SAR guidelines (NMFS 2005) state that abundance estimates older than 8 years should not be used to calculate PBR due to a decline in confidence in the reliability of an aged abundance estimate.” Statoil's activities are not anticipated to remove any individuals from the stock or population. Therefore, a recent estimate of PBR is not needed for NMFS to make the necessary findings under Section 101(a)(5)(D) of the MMPA. Additionally, Statoil's application provides information (including data limitations) and references for its estimates of marine mammal abundance. Because AEWC has not provided information contrary to the data provided by Statoil, and NMFS does not have information that these estimates are not reliable, NMFS considers these data to be the best available.

Comment 23:

Dr. Bain states that standard terminology in the field of density estimates is not used in density estimates, specifically citing the use of f(0). Dr. Bain recommends that an f(0) should be calculated from the data when there is a reference to 891 “transect” sightings of bowheads and that these sightings should have been used in Distance to calculate an f(0) for bowheads and states that it is reasonable to assume this has already been done. Dr. Bain states that log-normal confidence limits should be used when calculating the densities and that the upper confidence limits should be used as the point estimate in the take calculations. Dr. Bain recommends that double-platform trials should be run in Distance to better estimate g(0).

Response:

The traditional f(0) parameter and terminology are used throughout the density estimate descriptions in Statoil's application.

However, there is no reference given for the 891 “transect” sightings which would allow an evaluation of whether or not the associated covariates suggested by Dr. Bain are available for the recommended analysis. Also, Dr. Bain did not provide a reference for the results of such an analysis that he suggests are reasonable to assume exist.

The equations for the calculation of log-normal confidence limits are provided and an example using “three point estimates of summertime density of bowhead whales” is shown. However, there is no indication of where the three point estimates of summertime densities came from and values in the application do not combine to replicate the estimate provided. Using the upper confidence limits of an estimate is an extremely conservative approach on top of already conservative assumptions regarding received sound levels. Maximum densities and associate take estimates provided in the application are meant to provide upper estimates similar to those suggested from using the upper confidence limits. Basing decisions on take estimates from the upper confidence limits is, as Dr. Bain points out, extremely precautionary, and NMFS does not believe it represents the best available scientific approach.

Since no reference is given for such double-platform data on bowheads. NMFS is not aware of the existence or availability of sufficient data from double-platform trials while surveying bowheads to do the recommended analysis. Collection of an adequate dataset would likely require multiple years of aerial surveys using two observers on each side of the aircraft that collect data independently of each other, which is impracticable due to the scope and scale of the research. Nevertheless, based on available data and analysis, NMFS believes that existing datasets are adequate to address the degrees and levels of potential impacts to marine mammals as a result of the proposed seismic surveys in the project vicinity.

Comment 24:

Dr. Bain points out that use of the statistical method for incorporating uncertainties is trivial. He further states that the data were inappropriately split to estimate densities and that the raw data should have been analyzed using multivariate modeling approaches available in Distance.

Response:

As suggested by Dr. Bain, incorporating uncertainty associated with various parameters in a density estimate is relatively easier when working with actual raw survey data by using the Distance software. However, data or analyses of the type suggested on the relevant species at the location and time of the proposed project are not available. Estimates of uncertainty are not necessarily available for all parameters found in the literature that were used to calculate estimated densities. Although incorporating all parameters and associated uncertainties into a single framework would indeed be a good approach, it would not be practical for an applicant to conduct analyses in such detail and large scale. As stated earlier, NMFS believes that existing datasets are adequate to address the degrees and levels of potential impacts to marine mammals as a result of the proposed seismic surveys in the project vicinity.

As for the final point, data “splits” used in the application were based on a published article and the necessary data to do the analysis as Dr. Bain suggested using Distance are not available.

Comment 25:

Commenting on Southall

et al.

(2007), Dr. Bain states that Southall

et al.'

s review relied on published reports, and they were selective for datasets reported in a way that fit their categorization scheme. Dr. Bain points out that other workers have access to raw data and can rescore behavioral responses using Southall

et al.'

s system (

e.g.,

Bain and Williams in review). Dr. Bain further states that he found that the approach of generalizing responsiveness based on morphological group, such as pinnipeds, high-frequency hearing specialists (small odontocetes), low-frequency specialists (mysticetes), etc., unlikely to be valid, as sibling species such as Dall's and harbor porpoises differed dramatically in their responses to noise from the same airguns in the same geographic area, and harbor porpoises appeared more responsive to airguns than low-frequency specialists like gray whales.

Response:

NMFS does not agree with Dr. Bain's assessment on Southall

et al.'

s review. First, the central purpose of the Southall

et al.

(2007) paper is to propose, for various marine mammal groups and sound types, levels above which there is a scientific basis for expecting that exposure would cause auditory injury to occur. Although behavioral or electrophysiological audiograms only exist for approximately 20 marine mammal species (of ~128 species and subspecies; Rice 1998), however, since physiological effects of

the auditory structure,

i.e.,

TTS or PTS, are closely related to the frequency ranges of acoustic signals that are sensitive to a particular audio-physiology mechanism, by combining audiograms of known marine mammal species with comparative anatomy, modeling, and response measured in ear tissues from species that are difficult to study, it is a valid approach to classify marine mammal hearing based on their functional hearing groups. Although the current classification of five functional hearing groups (

i.e.,

low-frequency cetacean, mid-frequency cetacean, high-frequency cetacean, pinnipeds in water, and pinnipeds in air) is still in its initial stage, and further improvements are no doubt needed as more scientific information becomes available, these improvements are likely to be focusing on refining the current groupings (

e.g.,

dividing pinnipeds into otariids and phocids). NMFS considers the use of these functional hearing groups in addressing physiological effects and hearing impairment a valid approach.

Second, as far as behavioral effects are concerned, Southall

et al.

(2007) admits that “the available data on behavioral responses do not converge on specific exposure conditions resulting in particular reactions, nor do they point to a common behavioral mechanism.” They further points out that “[i]t is clear that behavioral responses are strongly affected by the context of exposure and by the animal's experience, motivation, and conditioning.” Therefore, behavioral responses to external stimuli may not be able to be addressed just based on received levels. For example, in Bain and Williams (in review) it is stated that Dall's porpoises were “observed at received levels up to approximately 180 dB re 1 μPa p-p,” while harbor porpoises were “recorded at received levels up to 155 dB re 1 μPa p-p, and all individuals were moving away at this level,” it is possible that a major factor causing the harbor porpoises to move away was the researchers' vessel that was closely approaching the animals at approximately 20 km/h. We believe a more rigorously designed controlled exposure experiment or behavioral response study is required to obtain unbiased data to address behavioral responses of marine mammals to anthropogenic sound. For this reason, studies used in the Southall

et al.

(2007) review were carefully selected to include studies where “noise exposure (including source and received levels, frequency, duration, duty cycle, and other factors) was either directly reported or was reasonably estimated using simple sound propagation models deemed appropriate for the sources and operational environment” (Southall

et al.

2007).

Nevertheless, for regulatory purposes, NMFS has been using 160 dB re 1 μPa (rms) as the onset for behavioral harassment when exposed by impulse sources. The basis for choosing received levels corresponding to the onset of behavioral harassment came from many field observations and analyses (

see

review by Richardson

et al.

1995; Southall

et al.

2007) that NMFS considers representative in many situations.

Comment 26:

Dr. Bain states that changes in behavior resulting from noise exposure could lead to injury or death through a number of mechanisms, and he gave the example that “hearing loss due to PTS or TTS may prevent animals from detecting approaching vessels, leading to collisions between marine mammals and vessels,” and that such collisions are often ultimately fatal, and that hearing loss may also lead to entanglement and increased risk of predation. Dr. Bain states that hearing ability can also be impaired during exposure to low levels of noise, causing masking. Dr. Bain also points out that another behavioral response to noise is flight, and that “flight can result in stranding (NOAA and Navy 2001), or extreme exhaustion resulting in muscle damage or heart failure (Williams and Thorne 1996).”

Response:

NMFS agrees that it is possible that changes in behavior or auditory masking resulting from noise exposure could lead to injury in marine mammals under certain circumstances, such as the hypothesized atypical diving patterns that may be exhibited by beaked whales when exposed to military tactical mid-frequency sonar, as discussed earlier and in NOAA and Navy (2001) cited by Dr. Bain in his comment. However, in most cases, changes in behavior resulting from noise exposure do not lead to PTS or TTS as apparently assumed by Dr. Bain in his comment. Additionally, as discussed in the

Federal Register

notice for the proposed IHA and in this document, marine mammals exposed to the proposed Statoil seismic surveys are not expected to experience TTS or PTS with the implementation of appropriate monitoring and mitigation measures. Furthermore, the assumption that Dr. Bain made that “exhaustion from rapid flight leading to heart or other muscle damage” could account for mortality merely because of exposure to airgun noise has no scientific basis.

For issues regarding behavioral change and masking by the proposed Statoil seismic surveys, NMFS does not believe that received SPLs from the airgun arrays would cause drastic changes in behavior or auditory masking in marine mammals outside the safety zones. Unlike military sonar, seismic pulses have an extremely short duration (tens to hundreds of milliseconds) and relatively long intervals (several seconds) between pulses. Therefore, the sound energy levels from these acoustic sources and small airguns are far lower in a given time period. Second, the intervals between each short pulse would allow the animals to detect any biologically significant signals, and thus avoid or prevent auditory masking. Although airgun pulses at long distances (over kilometers) may be “stretched” in duration and become non-pulse due to multipath propagation, the intervals between the non-pulse noises would still allow biologically important signals to be detected by marine mammals. In addition, NMFS requires mitigation measures to ramp-up acoustic sources at a rate of no more than 6 dB per 5 min. This ramp-up would prevent marine mammals from being exposed to high levels of noise without warning, thereby eliminating the possibility that animals would dramatically alter their behavior (i.e. from a “startle” reaction).

Comment 27:

Citing research on long term adverse effects to whales and dolphins from whale watching activities (Trites and Bain 2000; Bain 2002; Lusseau

et al.

2009), Dr. Bain states that Level B behavioral harassment could be the primary threat to cetacean populations.

Response:

Although NMFS agrees that long-term, persistent, and chronic exposure to Level B harassment could have a profound and significant impact on marine mammal populations, such as described in the references cited by Dr. Bain, those examples do not reflect the impacts of seismic surveys to marine mammals for Statoil's project. First, whale watching vessels are intentionally targeting and making close approaches to cetacean species so the tourists onboard can have a better view of the animals. Some of these whale/dolphin watching examples cited by Dr. Bain occurred in the coastal waters of the Northwest Pacific between April and October and for extended periods of time (“[r]ecreational and scientific whale watchers were active by around 6 a.m., and some commercial whale watching continued until around sunset”). Thus multiple vessels have been documented to be in relatively close proximity to whales for about 12 hours a day, six months a year, not counting some “out of season” whale

watching activities and after dark commercial filming efforts. In addition, noise exposures to whales and dolphins from whale watching vessels are probably significant due to the vessels' proximity to the animals. To the contrary, Statoil's proposed seismic survey, along with existing industrial operations in the Arctic Ocean, does not intentionally approach marine mammals in the project areas. Statoil's survey locations are situated in a much larger Arctic Ocean Basin, which is far away from most human impacts. Therefore, the effects from each activity are remote and spread farther apart, as analyzed in NMFS' 2010 EA, as well as the MMS 2006 PEA. Statoil's seismic activities would only be conducted between late July and October for about 60 days, weather permitting. In addition, although studies and monitoring reports from previous seismic surveys have detected Level B harassment of marine mammals, such as avoidance of certain areas by bowhead and beluga whales during the airgun firing, no evidence suggests that such behavioral modification is biologically significant or non-negligible (Malme

et al.

1986; 1988; Richardson

et al.

1987; 1999; Miller

et al.

1999; 2005), as compared to marine mammals exposed to chronic sound from whale watching vessels, as cited by Dr. Bain. Therefore, NMFS believes that potential impacts to marine mammals in the Chukchi Sea by seismic surveys would be limited to Level B harassment only, and due to the limited scale and remoteness of the project in relation to a large area, such adverse effects would not accumulate to the point where biologically significant effects would be realized.

Comment 28:

Dr. Bain notes that NMFS uses different thresholds for continuous and pulsed sounds, and that “NMFS based its use of a 120 dB contour for continuous sounds primarily on studies of bowheads and gray whales.” Dr. Bain observes that “these studies were conducted based on whales close to noise sources,” and the “120 dB contour was commonly the level at which 50% of the animals exposed to noise showed observable changes in behavior, such as deflection of the travel path away from the source.” Dr. Bain states that there are two problems with this interpretation of the data: (1) This implies that 50% of the whales observed responded to levels lower than 120 dB. That is, 120 dB is not a threshold for a species but a median value of thresholds of individuals. The likelihood that individuals will be taken by exposure to noise levels below 120 dB declines with received level, but does not approach 0 until the received level approaches the limit of audibility; and (2) individuals that responded to levels much lower than 120 dB were not included in these studies, as they did not approach close enough to be observed. NSB also states that bowhead whales showed almost total avoidance of an area around seismic surveys where received sound levels were greater than 120 dB (LGL Ltd. and Greenridge Sciences 1999), and that since the ensonified area for 120 dB is huge, the entire bowhead population could be affected.

Response:

Since Dr. Bain did not provide any reference in his comment, the validity of his notes and observation cannot be verified. However, NMFS is not aware of the “use of a 120 dB contour for continuous sounds” on any marine mammal species. The basis for choosing received levels corresponding to the onset of behavioral harassment came from many field observations and analyses (

see

review by Richardson

et al.

1995; Southall

et al.

2007) on measured avoidance responses in whales in the wild. It is also important to know that NMFS uses different received levels for behavioral harassment caused by impulse and non-impulse noises (i.e., received level at 160 dB re 1 µPa for impulse and 120 dB re 1 μPa for non-impulse). To be specific, the 160 dB re 1 μPa (rms) threshold was derived from data for mother-calf pairs of migrating gray whales (Malme

et al.

1983; 1984) and bowhead whales (Richardson

et al.

1985; Richardson

et al.

1986) responding when exposed to seismic airguns (impulsive sound source). The 120 dB re 1 μPa (rms) threshold also originates from research on baleen whales, specifically migrating gray whales (Malme

et al.

1984; predicted 50% probability of avoidance) and bowhead whales reacting when exposed to industrial (i.e., drilling and dredging) activities (non-impulsive sound source) (Richardson

et al.

1990).

Second, Dr. Bain confused “take” under the MMPA with any observed behavioral response. A “take” by Level B harassment is defined as “any act of pursuit, torment, or annoyance which * * * 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” (emphasis added). A brief startling response without subsequent change of the animal's ongoing behavioral pattern, for example, does not constitute a “take” under the definition of MMPA. Therefore, marine mammals that briefly respond to certain received noise levels may not be “taken,” as long as there is no disruption of their behavioral patterns.

Finally, as stated above, received levels at 160 dB re 1 μPa is currently used by NMFS as the onset of behavioral harassment for impulses, and source characteristics from airgun arrays are classified as impulses. Therefore, the 120 dB continuous noise discussion in Dr. Bain's comment is inapplicable.

Comment 29:

Citing works by Calambokidis

et al.

(1998) and Bain and Williams (in review) on impacts of marine mammal behavioral by seismic surveys, Dr. Bain states that harbor porpoises are more likely to be affected by lower received levels than other cetaceans. Dr. Bain states that he believes “the segregation of population by noise tolerance (and physical ability to avoid the noise source) provides an explanation for why some studies detect marine mammals close to noise sources, and other show responses to received levels in the neighborhood of 90 dB or less at great distance.” Dr. Bain further states that future work will be needed to elucidate nuances of how those probabilities are influenced by non-noise factors such as location, activity state, or individual factors like age, sex, reproductive status, health status, group composition, and previous experience with noise exposure. Dr. Bain concludes that “bowhead and gray whales can be expected to respond out to the 120 dB contour, with more sensitive individuals perhaps responding at the 105 dB contour. Killer whales and belugas would be expected to respond at the 105 dB contour, with the need for social cohesion resulting in less variability in response than seen in bowheads and grays. Harbor porpoises are likely to exhibit responses out to the level of detection, as they have been shown to respond to received noise below 90 dB in quiet water.”

Response:

NMFS agrees that behavioral responses by marine mammals to noise sources vary with species, population, behavioral context, age, sex, and source characteristics, etc., and NMFS has been looking into these factors and is supporting research such as behavioral response studies (BRS) at the Atlantic Undersea Test and Evaluation Center (AUTEC) in the Bahamas, the Mediterranean Sea, and off southern California to elucidate factors that could induce behavioral responses on cetaceans by various noise sources, particularly by military sonar. Nevertheless, at the current stage, as stated above, NMFS still uses the 120 dB and 160 dB re 1 μPa as the threshold for the onset of behavioral harassment

for non-impulse and impulse noise sources, respectively. Based on many field studies and observations (

see

review by Richardson

et al.

1995; Southall

et al.

2007), NMFS believes that these thresholds are conservative and can provide relatively fair estimates of marine mammals potentially subject to harassment.

Dr. Bain did not provide any reference to support his claim that “bowhead and gray whales can be expected to respond out to the 120 dB contour, with more sensitive individuals perhaps responding at the 105 dB contour. Killer whales and belugas would be expected to respond at the 105 dB contour, with the need for social cohesion resulting in less variability in response than seen in bowheads and grays. Harbor porpoises are likely to exhibit responses out to the level of detection, as they have been shown to respond to received noise below 90 dB in quiet water.” Additionally, Dr. Bain did not provide what these responses are and whether they meet the definition of “takes” under the MMPA.

Comment 30:

Citing his manuscript (Bain and Williams, in review) on effects of large airgun arrays on the behavior of marine mammals at long distances in the waters of British Columbia, Canada and Washington State, USA, Dr. Bain argues that marine mammals can be taken at much lower received levels, and states that NMFS underestimated take numbers of marine mammals.

Response:

NMFS reviewed Dr. Bain's attached manuscript (Bain and Williams, in review), which was attached with his comments. The paper examines the effects of large airgun arrays on behavior of marine mammals in the waters of British Columbia, Canada and Washington State, USA, using a small boat to monitor out to long ranges (1 to > 70 km from the seismic source vessel), and contains some information concerning marine mammals that were apparently affected by the seismic survey. The paper, which was originally presented at the IWC meeting in 2006, concludes that a significant relationship was observed between the magnitude of behavioral response and peak-to-peak received level and the long distances at which behavioral responses were observed (> 60 km for harbor porpoise), along with counter-productive behavior that occasionally brought individuals into higher-intensity acoustic zones. However, there are potential design flaws in this study. First, the paper states a launch carried aboard the seismic receiver vessel was placed in the water to perform received level measurements near marine mammals. When making acoustic measurements, the launch “travelled along a line at approximately 20 km/h until either marine mammals were closely approached, or the launch had travelled 10 km.” Therefore, it is highly likely that behavioral reactions from observed marine mammals were caused by the high-speed, close-approach of the launch, rather than from distant seismic airguns. This experiment design may explain the authors' observation of “counter-productive behavioral responses” that animals are moving into higher-intensity acoustic zones, which probably indicates that behavioral changes caused by Bain's launch greatly exceeded any behavioral change resulting from exposure to seismic airgun noise. Second, the authors of the paper also expressed “methodological concerns due to the subjectivity of observers.” Nevertheless, this study (Bain and Williams, in review) concludes that harbor seal individuals were generally moving away from the airguns at exposure levels above 170 dB re 1 μPa (p-p) and that gray whales were observed at received levels up to approximately 170 dB re 1 μPa (p-p) exhibiting no obvious behavioral response. These observations contradict Mr. Bain's earlier comments that major behavioral effects result from noise in the 105—125 dB range.

Finally, Bain and Williams (in review) also state that the study “found that while airguns concentrated their sound output at low frequencies, substantial high frequency energy (to at least 100 kHz) was also present.” However, the paper provides no explanation as to how this conclusion was made. The accompanying power density spectrum (Figure 2 in Bain and Williams, in review) of the paper fails to show evidence that the frequencies above 1 kHz were mostly contributed from seismic airguns, and there was no indication at what distance this recording was made. Therefore, Bain and Williams (in review) cannot be used to interpret marine mammal behavioral reactions to long distance seismic sources because it fails to provide a valid argument that the behavioral reactions by observed marine mammals are from seismic noises and that the acoustic energy of the recorded broadband received levels (up to 100 kHz) is entirely from seismic airguns.

Comment 31:

Stating marine mammal takes could occur at received levels at 90 dB, Dr. Bain claims that he used the applicant's equation of RL = 157.2 − 35.3 LOG (R/10000) − 0.0000064 (R − 10000) to estimate the distance to the 135 dB, 120 dB, 105 dB, and 90 dB contours, and showed that the best fit distances of these isopleths to be 42000, 110000, 270000, and 620000 (no units given), respectively, with relative areas at 10, 72, 431, and 2274 (no units given), respectively; the 90th percentile distances of these isopleths to be 45000, 116000, 285000, and 650000 (no units given), respectively, and the relative areas of these isopleths to be 12, 80, 311, and 2500 (no units given), respectively. In comparison, Statoil's estimated received level at 120-dB isopleths is 70-120 km from the source (75 FR 32379; June 8, 2010).

Response:

First, Statoil did not use the equation in Dr. Bain's comment for the estimates of distances to safety zones (180-dB and 190-dB re 1 μPa for cetaceans and pinnipeds, respectively) and zone of influence (160-dB re 1 μPa isopleths). As stated in Statoil's IHA application and in the

Federal Register

notice for the proposed IHA (75 FR 32379; June 8, 2010), the basis for the estimation of distances to the four received sound levels (190 dB, 180 dB, 160 dB, and 120 dB re 1 μPa) from the proposed 3000 in

3

airgun array operating at a depth of 20 ft (6 m) are the 2006, 2007 and 2008 sound source verification (SSV) measurements in the Chukchi Sea of a similar array, towed at a similar depth. The measured airgun array had a total discharge volume of 3,147 in

3

and was composed of three identically-tuned Bolt airgun sub-arrays, totaling 24 airguns (6 clusters of 2 airguns and 12 single airguns). The proposed 3,000 in

3

array is also composed of three strings with a total of 26 active airguns in 13 clusters (five clusters of 10 airguns are inactive and will be used as spares). The difference in discharge volume would lead to an expected loss of less than 0.2 dB and is neglected in this assessment. The estimated source level for the full 3,000 in

3

array is 245 dB re 1 μPa (rms). Before SSV tests could be conducted for the 3,000 in

3

array that would be used for the proposed seismic survey, it is reasonable to adopt the maximum distances obtained from a similar array during previous measurements in the Chukchi Sea. Therefore, the distances to received levels of 190, 180 160, and 120 dB re 1 μPa (rms) are conservatively estimated at 700, 2,500, 13,000, and 70,000-120,000 m, respectively. The only propagation equation Statoil used in estimating the zones of different isopleths is the one used to calculate the safety zones and zone of influence for the 60 in

3

mitigation gun, which was adjusted by adding 3 dB. The term of the equation is:

RL = 226.6 − 21.2log(R) − 0.00022R, where R is distance in m.

Second, based on the equation Dr. Bain provided, NMFS calculated the distances to 190 and 180-dB received levels at 1,180 m and 2,260 m, respectively, which are very different from what Dr. Bain reported at 370 and 1,100 (units not given), respectively, for “best fit”, and 450 and 1,400 (units not given), respectively, for “90th percentile.” Finally, without field measurements, NMFS does not know, and Dr. Bain did not explain, how the “best fit” and “90th percentile” were calculated.

Comment 32:

Dr. Bain states that recent declines in gray whale populations have resulted in the population dropping below the level at which they were delisted, and that emaciation has been observed in many gray whales that have stranded this year, so exclusion from potential feeding grounds is of extra concern this year. Further, Dr. Bain states that harbor porpoises can be affected at large distances from noise sources, and hence large numbers would be expected to be affected by this and other activities. He points out that although NMFS currently recognizes only a single, large stock whose range includes the project area, genetic and movement studies in other parts of the harbor porpoise range have shown that stocks tend to be much smaller and have limited ranges. Finally, Dr. Bain points out that cumulative effects on belugas and other species are likely to have been underestimated because the “greater range at which they are likely to be affected and the potential for greater overlap between the project activities and migration through the area than considered by NMFS for this and the shallow water survey make this the case.”

Response:

Systematic counts of Eastern Pacific gray whales migrating south along the central California coast have been conducted by shore-based observers at Granite Canyon most years since 1967. The most recent abundance estimates are based on counts made during the 1997-98, 2000-01, and 2001-02 southbound migrations. Analyses of these data resulted in abundance estimates of 29,758 for 1997-98, 19,448 for 2000-01, and 18,178 for 2001-02 (Rugh

et al.

2005). NMFS is aware of the 2000-01 and 2001-02 population drops in the gray whales, nevertheless, to a certain degree, variations in estimates may be due in part to undocumented sampling variation or to differences in the proportion of the gray whale stock migrating as far as the central California coast each year (Hobbs and Rugh 1999). The decline in the 2000-01 and 2001-02 abundance estimates may be an indication that the abundance was responding to environmental limitations as the population approaches the carrying capacity of its environment (Allen and Angliss 2010). Low encounter rates in 2000-01 and 2001-02 may have been due to an unusually high number of whales that did not migrate as far south as Granite Canyon or the abundance may have actually declined following high mortality rates observed in 1999 and 2000 (Gulland

et al.

2005). Visibly emaciated whales (LeBoeuf

et al.

2000; Moore

et al.

2001) suggest a decline in food resources, perhaps associated with unusually high sea temperatures in 1997 (Minobe 2002). Several factors since this mortality event suggest that the high mortality rate was a short-term, acute event and not a chronic situation or trend: (1) Counts of stranded dead gray whales dropped to levels below those seen prior to this event, (2) in 2001 living whales no longer appeared to be emaciated, and (3) calf counts in 2001-02, a year after the event ended, were similar to averages for previous years (Rugh

et al.

2005). Though it is impractical to exclude the proposed Statoil seismic survey entirely from the gray whale feeding areas (such as areas near Hanna Shoal), as discussed in the

Federal Register

notice for the proposed IHA (75 FR 32379; June 8, 2010) and in this document, the potential impacts to gray whales (and other marine mammals) is expected to be negligible. In addition, mitigation and monitoring measures described below would further reduce the potential impacts. Lastly, Statoil's surveys are not expected to destroy or result in any permanent impact on habitats used by gray whales or to their prey resources or to jeopardize the continued existence of the species.

Since delisting gray whales in 1994, NMFS has continued to monitor the status of the population consistent with its responsibilities under the ESA and the MMPA. In 1999, a NMFS review of the status of the eastern North Pacific stock of gray whales recommended the continuation of this stock's classification as nonthreatened (Rugh

et al.

1999). Workshop participants determined the stock was not in danger of extinction, nor was it likely to become so in the foreseeable future. In 2001 several organizations and individuals petitioned NMFS to re-list the eastern North Pacific gray whale population. NMFS concluded that there were several factors that may be affecting the gray whale population but there was no information indicating that the population may be in danger of extinction or likely to become so in the foreseeable future. Wade and Perryman (2002) and Punt

et al.

(2004) (cited in the 2008 SAR, Angliss and Allen 2009) found that the stock is within its optimum sustainable population level and that the population is likely close to or above its unexploited equilibrium level. NMFS continues to monitor the abundance of the stock through the MMPA stock assessment process, especially as it approaches its carrying capacity. If new information suggests a reevaluation of the eastern North Pacific gray whales' listing status is warranted, NMFS will complete the appropriate reviews.

Without scientific support, NMFS does not agree with Dr. Bain's assumption that “harbor porpoises can be affected at large distances from noise sources, and hence large numbers would be expected to be affected by this and other activities.” Due to the lack of robust field studies and observations, behavioral responses of harbor porpoises (a species in the “high-frequency cetacean” functional hearing group) to impulse noise sources such as those generated by airguns are poorly known. Given that they are high-frequency cetaceans, harbor porpoises are not considered to be sensitive to low frequency noise sources when compared to bowhead whales (which are “low-frequency cetaceans” species). However, NMFS currently uses 160 dB re 1 μPa (rms) as the threshold for the onset of behavioral harassment for all marine mammals. Therefore, NMFS believes its method for calculating takes of harbor porpoises using 160 dB re 1 μPa (rms) is reasonable.

Whether harbor porpoises occurring in Alaska waters belong to one single, large stock is still under scientific debate. Nevertheless, at this time, no data are available to reflect stock structure for harbor porpoise in Alaska, and for management purposes, NMFS Alaska Marine Mammal Stock Assessment reports consider only one Alaska stock of harbor porpoise (Allen and Angliss 2010). Should new information on harbor porpoise stocks become available, the harbor porpoise Stock Assessment Reports will be updated.

Finally, cumulative effects on beluga whales and other species are analyzed in NMFS 2010 EA for the proposed Shell and Statoil's marine and seismic surveys in the Beaufort and Chukchi Seas. The take calculation, which takes into considerations of seasonal and spatial distributions of marine mammals

in the proposed survey areas, is provided in Statoil's IHA application and in the

Federal Register

notice for the proposed IHA (75 FR 32379; June 8, 2010) and in this document.

Comment 33:

Dr. Bain states that humpback whales are endangered and the stock inhabiting Northern Alaska has a small PBR. Due to uncertainty over the exact amount of human-caused mortality, it is unknown whether ongoing human-caused mortality exceeds potential biological removal (PBR). Although humpback use of the project area is likely to be minimal, any impact on humpbacks poses threats at both the individual and population level. The story is the same for fin whales, except that ongoing human-caused mortality is believed to be near zero if one does not consider ship strikes. Dr. Bain further states that the PBR for the Eastern Chukchi beluga stock is undetermined, because no recent population data are available. If PBR were estimated from old data, it would be 74; with an average annual subsistence harvest of 59, this leaves 15 individuals for other human-caused mortality, which is smaller than many aggregations of belugas. That is, if seismic surveys had lethal effects on a single group of belugas, it could put human-caused mortality over PBR. Finally, Dr. Bain states that killer whales have been observed in the project area, but the stock(s) present is unknown. They are most likely members of the Gulf of Alaska, Aleutian Islands, and Bering Sea Transient Stock, which has a PBR of 3.1, some of which is caused by fishery interactions. A little less likely to be present are members of the Eastern North Pacific Alaska Resident Stock, which has a PBR of 11.2, with an existing human-caused mortality of 1.5 per year. For members of either stock, lethal effects of noise to a single group would exceed PBR.

Response:

Regarding humpback, fin, and killer whales, their occurrence in the proposed project area is rare, and NMFS take estimates show that only 2 individuals of each of these species would be taken by Level B behavioral harassment as a result of the proposed Statoil seismic survey in the Chukchi Sea. Although a total of 184 Eastern Chukchi Sea beluga whales are estimated to be taken by Level B behavioral harassment, these numbers represent less than 5 percent of the total Eastern Chukchi Sea beluga whales population. As mentioned in the

Federal Register

notice (75 FR 32379; June 8, 2010) and in this document, no takes by Level A harassment (injury) and death are expected or authorized for the proposed seismic activities. Therefore, the discussion of PBR is inapplicable to this action.

Comment 34:

AWL notes that Statoil's closely spaced survey lines and large cross-track distances will result in the “repeated exposure of the same area of waters.” AWL further states that although the area of overlap for 160-dB does not directly apply to the smaller 180- and 190-dB safety zones, the logic employed does reveal the potential for non-migratory species to encounter Statoil's surveying a number of times over its duration, since NMFS considers repeated exposure to sound levels that potentially cause TTS to potentially risk causing PTS.

Response:

Repeated exposure may cause a marine mammal to exhibit diminished 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, which will not be the case with Statoil's seismic survey. Additionally, the relatively short crosstrack distance of the 180- and 190-dB radius associated with Statoil's seismic survey result in small areas of overlap of exposed waters during the survey.

Moreover, as explained in detail elsewhere in this document, marine mammals will need to be closer to the seismic source and be exposed to SPLs greater than 190 dB to be exposed to sound levels that could cause TTS. In order for a marine mammal to receive multiple exposures (and thereby incur PTS), the animal would: (1) Need to be close to the vessel and not detected during the period of multiple exposures; (2) be swimming in approximately the same direction and speed as the vessel; and (3) not be deflected away from the vessel as a result of the noise from the seismic array. Preliminary model simulations for seismic surveys in the Gulf of Mexico indicate that marine mammals are unlikely to incur single or multiple exposure levels that could result in PTS, as the seismic vessel would be moving at about 4-5 knots, while the marine mammals would not likely be moving within the zone of potential auditory injury in the same direction and speed as the vessel, especially for those marine mammals that take measures to avoid areas of seismic noise.

Comment 35:

NSB indicates that Statoil's approach to estimating densities of beluga and bowhead whales is problematic. The best available scientific data show that most marine mammals move considerable distances over the course of the open water period and are not confined to a small area. This movement occurs throughout the open water period and is most intense during the autumn (late August through November) when marine mammals are migrating south through the Chukchi Sea. NSB requests that NMFS use the most appropriate methods for estimating takes.

AWL also questions the use of a “density” measure in determining take in the Chukchi Sea during the bowhead migration. AWL states that NMFS has recognized in the past that using density is inappropriate for determining bowhead take from seismic activities in the Beaufort Sea during the fall. AWL and NSB point out that Statoil used a density approach which assumes animals remain relatively stationary from one day to the next, but this assumption is inapplicable for surveying that will take place within a migratory corridor. AWL points out that the proposed IHA does not indicate the rationale for using an approach that ignores the fact that bowhead whales will pass through the Chukchi Sea in the fall. Dr. Bain notes that properly taking the bowhead migration into account, along with an appropriate sound threshold for harassment, could dramatically increase the estimate of harassed whales.

Response:

Statoil's density estimates for bowhead and beluga whales are based on the best scientific information available, which is the standard required by the MMPA implementing regulations at 50 CFR 216.102(a). The alternative method referred to by AWL for estimating take of migrating bowhead whales was only used for seismic operations in the Beaufort Sea for Shell's site clearance and seismic surveys (75 FR 22708; May 18, 2010). This method has not been applied to activities in the Chukchi Sea. Because the migration corridor is narrower and better defined in the Beaufort Sea than the Chukchi Sea, this method was deemed appropriate by NMFS for seismic operations in the Beaufort. However, the migratory path taken by bowhead whales once they enter the Chukchi Sea is not as well understood. Moreover, the migratory route is not as narrowly defined in the Chukchi. Additionally, if these species avoid areas of active seismic operations at levels lower than 160 dB re 1 μPa (rms), as noted by several of the commenters, then fewer animals will occur in the area of Statoil's operations. After careful evaluation of the methods used by Statoil to estimate take, NMFS has determined that Statoil used the best

scientific information available in calculating the take estimates.

Comment 36:

Citing George and Suydam (1998), NSB states that killer whales and ribbon seals occur regularly in the Chukchi Sea and are thus not extralimital, as Statoil described in its IHA application. NSB points out that NMFS should consider ribbon seals, killer whales, and minke whales to occur regularly in the survey area, to be conservative.

Response:

NMFS based its population assessment on the Alaska Marine Mammal Stock Assessment Reports (Allen and Angliss 2010), peer-reviewed or other technical articles, and prior year monitoring reports of seismic surveys to estimate the likelihood of their occurrence and calculate the take numbers for the species. Although George and Suydam (1998) reported in their paper on killer whale predation in the northeastern Chukchi and western Beaufort Seas, they acknowledged that “[k]iller whales (

Orcinus orca

) are infrequently reported from the northeastern Chukchi and western Beaufort Seas.” Based on the available information, NMFS does not expect that these species are likely to be taken in numbers representing more than a chance occurrence, as specified in the

Federal Register

notice for the proposed IHA (75 FR 32379; June 8, 2010).

Comment 37:

NSB points out that Statoil's application does not provide information about the movements of the Beaufort Sea stock of beluga whales through the Chukchi Sea, and that these beluga whales do migrate through the Chukchi Sea during the fall, when Statoil may be conducting seismic activities. NSB further points out that the minimum population estimate of 3,700 in NMFS' Alaska Marine Mammal Stock Assessment Reports (Angliss and Allen 2009) may be an underestimate of the actual population.

Response:

Statoil does state in the IHA application that “[i]n the fall, beluga whale densities in the Chukchi Sea are expected to be somewhat higher than in the summer because individuals of the eastern Chukchi Sea stock and the Beaufort Sea stock will be migrating south to their wintering grounds in the Bering Sea.” The take estimates of marine mammals are based on the densities of animals in particular areas (

e.g.,

Moore

et al.

2000), and calculated to yield the number of animals that are likely to be “taken” within modeled zones of influence, as described in details in Statoil's IHA application. Therefore, the calculation of marine mammal take estimation is relevant to its population size. However, stock or population size of a marine mammal species is used in determining whether the number of takes affect a “small number” of marine mammals. For a given level of “take,” a species with a small population is expected to experience larger impact than a species with a larger population size. Therefore, contrary to what NSB states, using the minimum population estimate (since the best population estimate is unknown) of eastern Chukchi Sea beluga to calculate the percentage of take is actually a conservative measure to assess takes of marine mammals.

Subsistence Issues

Comment 38:

AEWC states that the nondiscretionary congressional directive that there will be no more than a negligible impact to marine mammals and no unmitigable adverse impact on the availability of marine mammals for subsistence taking is consistent with the MMPA's overall treatment of both marine mammal and subsistence protections. AEWC further states that Congress has set a “moratorium on the taking * * * of marine mammals,” 16 U.S.C. 1371(a), with the sole exemption provided for the central role of subsistence hunting by Alaska Natives. Thus, AEWC concludes that Congress has given priority to subsistence takes of marine mammals over all other exceptions to the moratorium, which may be applied for and obtained only if certain statutory and regulatory requirements are met. However, AEWC states that incidental harassment authorizations are available only for specified activities for which the Secretary makes the mandated findings. Thus, the pursuit of those activities is subordinated, by law, to the critical subsistence uses that sustain Alaska's coastal communities. AWL and NSB further states that NMFS has not adequately demonstrated that the proposed activities will not have “an unmitigable adverse impact on the availability of such species or stock for taking for subsistence uses.”

Response:

The MMPA does not prohibit an activity from having an adverse impact on the availability of marine mammals for subsistence uses; rather, the MMPA requires NMFS to ensure the activity does not have an unmitigable adverse impact on the availability of such species or stocks for taking for subsistence uses. NMFS has defined “unmitigable adverse impact” in 50 CFR 216.103 as an impact resulting from the specified activity: (1) That is likely to reduce the availability of the species to a level insufficient for a harvest to meet subsistence needs by: (i) Causing the marine mammals to abandon or avoid hunting areas; (ii) directly displacing subsistence users; or (iii) placing physical barriers between the marine mammals and the subsistence hunters; and (2) that cannot be sufficiently mitigated by other measures to increase the availability of marine mammals to allow subsistence needs to be met.

For the determination of the unmitigable adverse impact analysis, NMFS, other government agencies, and affected stakeholder agencies and communities were provided a copy of the POC in May 2010, which outlined measures Statoil would implement to ensure no unmitigable adverse impact to subsistence uses. The POC specifies times and areas to avoid in order to minimize possible conflicts with traditional subsistence hunts by North Slope villages for transit and open-water activities. Statoil waited to begin activities until the close of the spring beluga hunt in the village of Point Lay. Statoil has also developed a Communication Plan and will implement the plan before initiating the 2010 program to coordinate activities with local subsistence users as well as Village Whaling Associations in order to minimize the risk of interfering with subsistence hunting activities, and keep current as to the timing and status of the bowhead whale migration, as well as the timing and status of other subsistence hunts. The Communication Plan includes procedures for coordination with Communication and Call Centers to be located in coastal villages along the Chukchi Sea during Statoil's program in 2010.

Based on the measures contained in the IHA (and described later in this document), NMFS has determined that mitigation measures are in place to ensure that Statoil's operations do not have an unmitigable adverse impact on the availability of marine mammal species or stocks for subsistence uses.

Comment 39:

AWL points out that the importance of bowhead and beluga whales to coastal communities and their acknowledged sensitivity to noise impacts strongly favor a precautionary approach, and that to implement such an approach, NMFS should first undertake a comprehensive assessment of traditional ecological knowledge.

Response:

NMFS recognizes the importance of bowhead whales and other marine mammals to coastal communities and thus is taking a precautionary approach in evaluating the potential impacts that may rise from Statoil's seismic surveys. NMFS has prepared an Environmental Assessment (EA) and Finding of No Significant Impact for the issuance of IHAs to Statoil and Shell to take marine

mammals incidental to the proposed seismic and marine surveys in the 2010 open water season in the Beaufort and Chukchi Seas (NMFS 2010). The EA provides a comprehensive review of the traditional ecological knowledge and assessed the potential impacts to the subsistence life in the Arctic from the proposed survey activities.

Mitigation and Monitoring Concerns

Comment 40:

NSB and Dr. Bain are concerned that MMOs cannot see animals at the surface when it is dark or during the day because of fog, glare, rough seas, the small size of animals such as seals, and the large portion of time that animals spend submerged. NSB also notes that Statoil has acknowledged that reported sightings are only “minimum” estimates of the number of animals potentially affected by surveying.

Response:

NMFS recognizes the limitations of visual monitoring in darkness and other inclement weather conditions. Therefore, in the IHA to Statoil, NMFS requires that no seismic airgun can be ramped up when the entire safety zones are not visible. However, Statoil's operations will occur in an area where periods of darkness do not begin until early September. Beginning in early September, there will be approximately 1-3 hours of darkness each day, with periods of darkness increasing by about 30 min each day. By the end of the survey period, there will be approximately 8 hours of darkness each day. These conditions provide MMOs favorable monitoring conditions for most of the time.

Comment 41:

NSB and AEWC note that Statoil asserts that mitigation measures are designed to protect animals from injurious takes, but it is not clear that these mitigation measures are effective in protecting marine mammals or subsistence hunters. AEWC states that data previously presented by Shell and ConocoPhillips from their seismic activities made clear that MMOs failed to detect many marine mammals that encroached within the designated safety zones. AEWC also states that laser rangefinding binoculars are not useful in measuring distances to animals directly.

Response:

NMFS believes that the required monitoring and mitigation measures are effective and are an adequate means of effecting the least practicable impact to marine mammals and their habitats. The monitoring reports from 2006, 2007, 2008, and 2009 do not note any instances of serious injury or mortality (Patterson

et al.

2007; Funk

et al.

2008; Ireland

et al.

2009; Reiser

et al.

2010). Additionally, the fact that a power-down or shutdown is required does not indicate that marine mammals are not being detected or that they are incurring serious injury. As discussed elsewhere in this document and in the Notice of Proposed IHA (75 FR 32379; June 8, 2010), the received level of a single seismic pulse (with no frequency weighting) might need to be approximately 186 dB re 1 μPa

2

-s (

i.e.,

186 dB sound exposure level [SEL]) in order to produce brief, mild TTS (a non-injurious, Level B harassment) in odontocetes. 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 Statoil's proposed survey activities, the distance at which the received energy level (per pulse) would be expected to be ≥ 175-180 dB SEL is the distance to the 190 dB re 1 μPa (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 ≥ 175-180 dB SEL (190 dB re 1 μPa (rms)) are modeled to be restricted to a radius of approximately 700 m around the airgun array, but are likely to be smaller due to the larger airgun array used in modeling.

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.

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). However, more recent indications are that TTS onset in the most sensitive pinniped species studied (harbor seal, which is closely related to the ringed seal) may occur at a similar SEL as in odontocetes (Kastak

et al.

2004).

NMFS concluded that cetaceans and pinnipeds should not be exposed to pulsed underwater noise at received levels exceeding, respectively, 180 and 190 dB re 1 μPa (rms). The established 180- and 190-dB re 1 μPa (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 μPa rms (Southall

et al.

2007). No cases of TTS are expected as a result of Statoil'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.

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). 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. Given the higher level of sound necessary to cause PTS, it is even less likely that PTS could occur. In fact, even the sound 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.

NMFS does not believe that MMOs failed to detect many marine mammals that encroached within the designated safety zones. As indicated in the monitoring reports for prior years' open water seismic surveys, marine mammals were routinely detected before and

during seismic surveys using airgun arrays. Although the reports reveal that a few marine mammals entered the designated safety zone without being detected immediately, these events occurred very infrequently and shutdowns were called for immediately when a marine mammal was found within the safety zone. Despite these rare occurrences, NMFS does not believe animals would have experienced TTS or injury because, as noted throughout this document, the 180 dB and 190 dB thresholds for injury are conservative and the best available science indicates animals need to be exposed to significantly higher received levels or for much longer duration to experience TTS, let alone injury, which was very unlikely in the cases documented in prior years' surveys.

NMFS acknowledges that night-time monitoring by using night vision devices is not nearly as effective as visual observation during daylight hours. Therefore, the IHA issued to Statoil prohibits start up of seismic airguns when the entire safety zone cannot be effectively monitored during the night-time hours. Therefore, if Statoil has a shutdown of its seismic airgun array during low-light hours, it will have to wait till daylight to start ramping up the airguns.

Comment 42:

Citing the report from the peer review panel created for the 2010 Open Water meeting, AWL points out that the report stated that Statoil's “proposed methods would not be sufficient for adequate monitoring of the area within the safety radii when the radii are far from the vessel.” NSB also questions the ability of MMOs to detect marine mammals within the 2,500 m safety radii of 180-dB isopleths. AWL further points out that the proposed IHA needs to clarify how marine mammal observers on the support vessels will assist in monitoring safety zones, because the peer review comments noted that even with the addition of two support vessels, Statoil “will be able to monitor only a limited area.”

Response:

First, the comment by the peer review panel in March 2010 during the Open Water meeting in Anchorage, Alaska, was based on a draft version of the Statoil's IHA application, which did not include monitoring measures such as the use of “Big Eye” binoculars (25 x 50). In working with Statoil, NMFS has required the applicant to include the use of “Big Eye” binoculars as a standard device for marine mammal monitoring. In addition, NMFS has also included a number of recommendations from the peer review panel as requirements in the IHA to improve marine mammal monitoring during Statoil's seismic survey. These recommendations, which are discussed in more detail below, include: (1) The use of “big eyes” paired with searching with the naked eye; (2) use of the best possible positions for observing (e.g., outside and as high on the vessel as possible); and (3) pairing experienced MMOs with MMOs who are lacking experience. Further, the estimated safety radii for 180-dB and 190-dB isopleths are at 2,500 m and 700 m from the seismic airgun source, respectively, based on modeling of a large airgun array (3,147 in

3

) and adjusted upward. The empirically measured distances from this bigger airgun array from 2006-2009 were 460 m, 550 m, and 610 m for the 190-dB isopleths, and 1,400 m, 2,470 m, and 2,000 m for the 180-dB isopleths. All these safety radii are smaller than the estimated ones for the smaller airgun array. Therefore, NMFS expects that the empirically measured safety radii for the airgun array used in Statoil's proposed seismic survey would be much smaller than currently modeled, which would reduce the distance to be monitored.

Regarding the use of support vessels to assist in monitoring safety zones and zones of influence, the lead MMO on the seismic source vessel (or his/her designee) will work with the seismic contractor and/or the Captain to identify areas that will be ensonified to levels ≥ 160 dB during the next 24- to 48-hour time period. Based on this information MMOs on the source vessel will communicate that information to MMOs and the Captains of support vessels. Statoil will have two support vessels (

Tanux I

and

Norseman I

) assisting the seismic source vessel with this monitoring and other project-related activities. Monitoring routes within the ≥ 160 dB are often a series of zig-zags, or a racetrack pattern. The goal is to maximize monitoring coverage within the ≥ 160 dB zone as dictated by support vessel availability, daylight, and survey conditions to ensure that aggregates of non-migratory baleen whales are not present within the zone. Support vessels will transit to and begin monitoring of these locations while maintaining routine communications with the source vessel MMOs to report monitoring status and any relevant sightings.

Comment 43:

AWL and Dr. Bain note that NMFS appears to simply presume that marine mammals will naturally avoid airguns when they are operating (even when limited to the single mitigation gun), removing the need for monitoring when conditions prevent observers from effectively watching for intrusions into the exclusion zones. AWL and NSB point out that the requirement for ramp ups rests on the same foundation—that marine mammals will leave an affected area as a result of increasing noise. Citing a report by the Joint Subcommittee on Ocean Science and Technology (JSOST 2009), AWL questions the efficacy of ramp up. NSB also questions the ability of power down and shutdown to protect marine mammals.

Response:

NMFS recognizes that uncertainties regarding marine mammal responses to seismic airgun noise still exist, including avoidance, behavioral reactions, temporary displacement, etc. However, there are many field studies and observations indicating that animals are not likely to occur within an area where sound levels could cause impairment to their auditory apparatus (

see

review by Richardson

et al.

1995; Southall

et al.

2007). In addition, monitoring reports during prior years' seismic surveys all record more marine mammal sightings in the vicinity of the seismic vessel when airguns are off than when airguns are on (Patterson

et al.

2007; Funk

et al.

2008; Ireland

et al.

2009; Reiser

et al.

2010).

For the time period of Statoil's seismic surveys, daylight will occur for 24 h/day until mid-August. Until that date MMOs will automatically be observing during the 30-minute period preceding a ramp up. Later in the season when visibility becomes low, MMOs will be called out at night to observe prior to and during any ramp up using night vision devices (Generation 3 binocular image intensifiers, or equivalent units). Nevertheless, in the IHA NMFS requires that no airgun can be started for ramp up if the entire safety zones cannot be visually observed for at least 30 minutes.

NMFS recognizes that the efficacy of ramp-up has not been well studied. However, before additional scientific information becomes available to show its lack of effectiveness in warning away marine mammals, the employment of ramp up will be required. To help evaluate the utility of ramp-up procedures, NMFS will require observers to record and report their observations during any ramp-up period. An analysis of these observations may lead to new information regarding the effectiveness of ramp-up and should be included in the monitoring report for the 2010 Statoil seismic survey.

Nevertheless, NMFS is confident about the efficacy of power down and especially shutdown in protecting marine mammals from Level A and B harassment from seismic noise sources. By shutting down the airgun array, there will be no seismic noise produced, therefore, marine mammals are unlikely

be taken by Level A and B harassment from noise exposure. Similarly, by powering down the acoustic source, the safety zones will be reduced, and marine mammals that were in these zones will now be placed outside the zones ensonified by a smaller airgun source.

Comment 44:

The Commission recommends NMFS require the applicant to collect data on the behavior and movements of any marine mammals present during all ramp-up and power-down procedures to help evaluate the effectiveness of these procedures as mitigation measures; and (2) undertake or prompt others to undertake studies needed to resolve questions regarding the effectiveness of ramp-up and power-down as mitigation measures. NSB also questions the effectiveness of ramp-up measures.

Response:

In order to issue an incidental take authorization (ITA) under Sections 101(a)(5)(A) and (D) of the MMPA, NMFS must, where applicable, set forth the permissible methods of taking pursuant to such activity, and other means of effecting the least practicable impact on such species or stock and its habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, and on the availability of such species or stock for taking for certain subsistence uses (where relevant). For Statoil's proposed open water seismic surveys, a series of mitigation and monitoring measures are required under the IHA. These mitigation measures include: (1) Sound source measurements to determine safety zones more accurately, (2) establishment of safety and disturbance zones to be monitored by MMOs on the seismic vessel, (3) a power-down when a marine mammal is detected approaching a safety zone and a shutdown when a marine mammal is observed within a zone, (4) ramp-up of the airgun array, and (5) a requirement that vessels reduce speed when within 274 m (300 yards) of whales and steer around those whales if possible.

The basic rationale for these mitigation measures is (a) to avoid exposing marine mammals to intense seismic airgun noises at received levels that could cause TTS (for mitigation measures listed as (1) through (4)); and (b) to avoid vessel strike of marine mammals (mitigation measure (5)). Although limited research in recent years shows that noise levels that could induce TTS in odontocetes and pinnipeds are much higher than current NMFS safety thresholds (i.e., 180 dB and 190 dB re 1 μPa (rms) for cetaceans and pinnipeds, respectively), mitigation measures listed in (1) through (3) provide very conservative measures to ensure that no marine mammals are exposed to noise levels that would result in TTS. The power-down measure listed in (3) requires Statoil to reduce the firing airguns accordingly so that a marine mammal that is detected approaching the safety zone will be further away from the reduced safety radius (as a result of power-down).

Regarding mitigation measures requiring ramp-ups and power-down, while scientific research built around the question on whether ramp-up is effective has not been conducted, several studies on the effects of anthropogenic noise on marine mammals indicate that many marine mammals will move away from a sound source that they find annoying (

e.g.

Malme

et al.

1984; Miller

et al.

1999; others reviewed in Richardson

et al.

1995). In particular, three species of baleen whales have been the subject of tests involving exposure to sounds from a single airgun, which is equivalent to the first stage of ramp-up. All three species were shown to move away at the onset of a single airgun operation (Malme

et al.

1983; 1984; 1985; 1986; Richardson

et al.

1986; McCauley

et al.

1998; 2000). From this research, it can be presumed that if a marine mammal finds a noise source annoying or disturbing, it will move away from the source prior to sustaining an injury, unless some other over-riding biological activity keeps the animal from vacating the area. This is the premise supporting NMFS' and others' belief that ramp-up is effective in preventing injury to marine mammals. However, to what degree ramp-up protects marine mammals from exposure to intense noises is unknown. For power-down, the rationale is that by powering down airgun arrays, marine mammals that are exposed to received noise levels that could induce TTS will be exposed to lower levels of sound due to the reduction in the output of the airgun source. Nevertheless, NMFS will require industry applicants that will conduct marine or seismic surveys in the 2010 open water season to collect, record, analyze, and report MMO observations during any ramp-up and power-down periods.

Comment 45:

Citing Thomas

et al.

(2002), Dr. Bain states that the effective strip half-width (µ, the point at which the number of animals sighted beyond that distance equals the number missed inside) is the maximum distance at which the species of interest can be sighted (w), then the number of animals missed closer to the vessel than µ equals the number of animals sighted between µ and w. Dr. Bain further assumes that µ is the distance to the 180 dB contour (isopleths, the approximate value of µ in Figure 15.3 of Richardson and Thomas (2002) for Beaufort 0-3) and w is the distance to the 160 dB contour (isopleths), and points out that if one whale is seen in the outer zone (radius of 13 km for the 160-dB isopleths) “where the sighting probability is say 9% or less,” that would suggest that one whale was missed in the inner zone (radius of 2.5 km for the 180-dB isopleths), and 10 were missed in the outer zone. Dr. Bain concludes that “the sighting of a single whale outside the strip half-width would be strong evidence that 12 are present.” Dr. Bain thus summarizes that “if a whale is sighted in the inner zone, the airguns would shut down per the 180 dB rule. If a whale is sighted in the outer zone, that would imply that 12 are present within the 160 dB contour, and hence the airguns should shut down per the 160 dB rule. That is, sighting a single bowhead or gray whale, regardless of distance, is evidence the shutdown criteria have been met.” Dr. Bain further states that even if no whales are seen, the shutdown criteria may have been meet, as he states that from high observation platforms (11-27 m in eye height), a pair of observers has about a 60% chance of detecting a mysticete whale at the 180-dB isopleths (2.5 km), and that for the paired observation team plots, where sample size is larger, the observers are estimated to have about a 50% chance of seeing a whale at 2.5 km. That is, Dr. Bain concludes, “a whale can be in the zone where there is a risk of immediate injury or death and have only a 50% chance of triggering a shutdown under ideal conditions.” Dr. Bain then applies the same logic for seals and states that “a high proportion of seals within the 190 dB contour will fail to trigger a shutdown.”

Response:

While NMFS agrees with Dr. Bain's assessment in principle, NMFS disagrees with a number of assumptions being made in his comments. First, the reference Dr. Bain used to extrapolate the effective strip half-width (µ = 2.5 km) and sighting probability (9%) addresses correction factors that were used for aerial surveys. Although aerial surveys are conducted at higher platforms than vessel surveys, the speed of an aircraft (approximately 100 knots) does not allow adequate time for scanning a particular area, and thus may miss marine mammals if they happen to be underwater. Therefore, using an aerial sighting probability of 9% to address vessel surveys may not be appropriate. Second, Dr. Bain's

hypothetical 9% sighting probability is based on the assumption of using one survey platform only. For Statoil's proposed seismic survey, multiple vessels besides the source vessel will be employed for marine mammal monitoring, and these chase/monitoring vessels are able to fill the sighting gaps that MMOs from the source vessel may miss. Third, using sighting probability for the entire survey tracklines may not be a realistic way to predict the number of animals in the vicinity of the survey area, which tends to be moving constantly. Unless the animals congregate in a large group, sighting probability at an instantaneous location should be interpreted as the percentage of probability of detecting a single animal, instead of the percentage of a group of animals in the area. Therefore, it does not seem reasonable to call for a shutdown of seismic airguns when a whale is detected in the 160-dB zone of influence.

Regarding Dr. Bain's second comment that a whale has a 50% chance of facing the risk of immediate injury or death when

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