# Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to a Geophysical Survey of the Queen Charlotte Fault > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A2021-11718 ## Record - **Collection:** Federal Register - **Document type:** Notice - **Published:** June 4, 2021 - **Citation:** 86 FR 30006 ## Text DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration [RTID 0648-XB083] Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to a Geophysical Survey of the Queen Charlotte Fault AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce. ACTION: Notice; proposed incidental harassment authorization; request for comments on proposed authorization and possible renewal. SUMMARY: NMFS has received a request from the Lamont-Doherty Earth Observatory of Columbia University (L-DEO) for authorization to take marine mammals incidental to a marine geophysical survey of the Queen Charlotte Fault in the Northeast Pacific Ocean. The proposed survey would be funded by the National Science Foundation (NSF). Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting comments on its proposal to issue an incidental harassment authorization (IHA) to incidentally take marine mammals during the specified activities. NMFS is also requesting comments on a possible one-time, one-year renewal that could be issued under certain circumstances and if all requirements are met, as described in Request for Public Comments at the end of this notice. NMFS will consider public comments prior to making any final decision on the issuance of the requested MMPA authorizations and agency responses will be summarized in the final notice of our decision. DATES: Comments and information must be received no later than July 6, 2021. ADDRESSES: Comments should be addressed to Jolie Harrison, Chief, Permits and Conservation Division, Office of Protected Resources, National Marine Fisheries Service. Physical comments should be sent to 1315 East-West Highway, Silver Spring, MD 20910 and electronic comments should be sent to ITP.Laws@noaa.gov. Instructions: NMFS is not responsible for comments sent by any other method, to any other address or individual, or received after the end of the comment period. Comments received electronically, including all attachments, must not exceed a 25-megabyte file size. All comments received are a part of the public record and will generally be posted online at www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act without change. All personal identifying information ( e.g., name, address) voluntarily submitted by the commenter may be publicly accessible. Do not submit confidential business information or otherwise sensitive or protected information. FOR FURTHER INFORMATION CONTACT: Ben Laws, Office of Protected Resources, NMFS, (301) 427-8401. Electronic copies of the application and supporting documents, as well as a list of the references cited in this document, may be obtained online at: www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act. In case of problems accessing these documents, please call the contact listed above. SUPPLEMENTARY INFORMATION: Background The MMPA prohibits the “take” of marine mammals, with certain exceptions. Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq. ) direct the Secretary of Commerce (as delegated to NMFS) 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 incidental take authorization may be 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) and will not have an unmitigable adverse impact on the availability of the species or stock(s) for taking for subsistence uses (where relevant). Further, NMFS must prescribe the permissible methods of taking and other “means of effecting the least practicable adverse impact” on the affected species or stocks and their habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, and on the availability of the species or stocks for taking for certain subsistence uses (referred to in shorthand as “mitigation”); and requirements pertaining to the mitigation, monitoring and reporting of the takings are set forth. The definitions of all applicable MMPA statutory terms cited above are included in the relevant sections below. National Environmental Policy Act To comply with the National Environmental Policy Act of 1969 (NEPA; 42 U.S.C. 4321 et seq. ) and NOAA Administrative Order (NAO) 216-6A, NMFS must review our proposed action ( i.e., the issuance of an IHA) with respect to potential impacts on the human environment. Accordingly, NMFS plans to adopt NSF's Environmental Assessment (EA), as we have preliminarily determined that it includes adequate information analyzing the effects on the human environment of issuing the IHA. NSF's EA is available at www.nsf.gov/geo/oce/envcomp/. We will review all comments submitted in response to this notice prior to concluding our NEPA process or making a final decision on the IHA request. Summary of Request On December 3, 2019, NMFS received a request from L-DEO for an IHA to take marine mammals incidental to a geophysical survey of the Queen Charlotte Fault (QCF) off of Alaska and British Columbia, Canada. L-DEO submitted a revised version of the application on April 2, 2020. On April 10, 2020, L-DEO informed NMFS that the planned survey would be deferred to 2021 as a result of issues related to the COVID-19 pandemic. L-DEO subsequently submitted revised versions of the application on October 22 and December 16, 2020, the latter of which was deemed adequate and complete. A final, revised version was submitted on January 11, 2021. L-DEO's request is for take of 21 species of marine mammals by Level B harassment. In addition, NMFS proposes to authorize take by Level A harassment for seven of these species. Description of Proposed Activity Overview Researchers from L-DEO, the University of New Mexico, and Western Washington University, with funding from NSF, propose to conduct a high-energy seismic survey from the Research Vessel (R/V) Marcus G. Langseth ( Langseth ) at the QCF in the northeast Pacific Ocean during late summer 2021. Other research collaborators include Dalhousie University, the Geological Survey of Canada, and the U.S. Geological Survey. The proposed two-dimensional (2-D) seismic survey would occur within the Exclusive Economic Zones (EEZ) of the United States and Canada, including in Canadian territorial waters. The survey would use a 36-airgun towed array with a total discharge volume of ~6,600 cubic inches (in 3 ) as an acoustic source, acquiring return signals using both a towed streamer as well as ocean bottom seismometers (OBSs). The proposed study would use 2-D seismic surveying to characterize crustal and uppermost mantle velocity structure, fault zone architecture and rheology, and seismicity of the QCF. The QCF system is an approximately 1,200 kilometer (km)-long onshore-offshore transform system connecting the Cascadia and Alaska-Aleutian subduction zones; the QCF is the approximately 900 km-long offshore component of the transform system. The purpose of the proposed study is to characterize an approximately 450-km segment of the fault that encompasses systematic variations in key parameters in space and time: (1) Changes in fault obliquity relative to Pacific-North American plate motion leading to increased convergence from north to south; (2) Pacific plate age and theoretical mechanical thickness decrease from north to south; and (3) a shift in Pacific plate motion at approximately 12-6 million years ago that may have increased convergence along the entire length of the fault, possibly initiating underthrusting in the southern portion of the study area. Current understanding of how these variations are expressed through seismicity, crustal-scale deformation, and lithospheric structure and dynamics is limited due to lack of instrumentation and modern seismic imaging. Dates and Duration The proposed survey is expected to last for approximately 36 days, including approximately 27 days of seismic operations, 3 days of equipment deployment/retrieval, 2 days of transits, and 4 contingency days (accounting for potential delays due to, e.g., weather). R/V Langseth would likely leave out of and return to port in Ketchikan, Alaska, during July-August 2021. Specific Geographic Region The proposed survey would occur within the area of approximately 52-57° N and approximately 131-137° W. Representative survey tracklines are shown in Figure 1. Some deviation in actual track lines, including the order of survey operations, could be necessary for reasons such as science drivers, poor data quality, inclement weather, or mechanical issues with the research vessel and/or equipment. The survey is proposed to occur within the EEZs of the United States and Canada, including Alaskan state waters and Canadian territorial waters, ranging in depth from 50-2,800 meters (m). Approximately 4,250 km of transect lines would be surveyed, with 13 percent of the transect lines in Canadian territorial waters. Most of the survey (69 percent) would occur in deep water (>1,000 m), 30 percent would occur in intermediate water (100-1,000 m deep), and approximately 1 percent would take place in shallow water <100 m deep. Note that the MMPA does not apply in Canadian territorial waters. L-DEO is subject only to Canadian law in conducting that portion of the survey. However, NMFS has calculated the expected level of incidental take in the entire activity area (including Canadian territorial waters) as part of the analysis supporting our determination under the MMPA that the activity will have a negligible impact on the affected species (see Estimated Take and Negligible Impact Analysis and Determination). BILLING CODE 3510-22-P EN04JN21.003 BILLING CODE 3510-22-C Detailed Description of Specific Activity The procedures to be used for the proposed survey would be similar to those used during previous seismic surveys by L-DEO and would use conventional seismic methodology. The surveys would involve one source vessel, the R/V Langseth. R/V Langseth would deploy an array of 36 airguns as an energy source with a total volume of 6,600 in 3 . The array consists of 36 elements, including 20 Bolt 1500LL airguns with volumes of 180 to 360 in 3 and 16 Bolt 1900LLX airguns with volumes of 40 to 120 in 3 . The airgun array configuration is illustrated in Figure 2-11 of NSF and USGS's Programmatic Environmental Impact Statement (PEIS; NSF-USGS, 2011). (The PEIS is available online at: www.nsf.gov/geo/oce/envcomp/usgs-nsf-marine-seismic-research/nsf-usgs-final-eis-oeis-with-appendices.pdf ). The vessel speed during seismic operations would be approximately 4.2 knots (kn) (~7.8 km/hour) during the survey and the airgun array would be towed at a depth of 12 m. The receiving system would consist of OBSs and a towed hydrophone streamer with a nominal length of 15 km (OBS and multi-channel seismic (MCS) shooting). As the airguns are towed along the survey lines, the hydrophone streamer would transfer the data to the on-board processing system, and the OBSs would receive and store the returning acoustic signals internally for later analysis. Approximately 60 short-period OBSs would be deployed and subsequently retrieved at a total of 123 sites in multiple phases from a second vessel, the Canadian Coast Guard ship John P. Tully (CCGS Tully ). Along OBS refraction lines, OBSs would be deployed by CCGS Tully at 10 km intervals, with a spacing of 5 km over the central 40 km of the fault zone for fault-normal crossings. Twenty-eight broadband OBS instruments would also collect data during the survey and would be deployed prior to the active-source seismic survey, depending on logistical constraints. When an OBS is ready to be retrieved, an acoustic release transponder (pinger) interrogates the instrument at a frequency of 8-11 kHz; a response is received at 11.5-13 kHz. The burn-wire release assembly is then activated, and the instrument is released from its 80-kg anchor to float to the surface. Take of marine mammals is not expected to occur incidental to L-DEO's use of OBSs. The airguns would fire at a shot interval of 50 m (approximately 23 s) during MCS shooting with the hydrophone streamer (approximately 42 percent of survey effort), at a 150-m interval (approximately 69 s) during refraction surveying to OBSs (approximately 29 percent of survey effort), and at a shot interval of every minute (approximately 130 m) during turns (approximately 29 percent of survey effort). Short-period OBSs would be deployed first along five OBS refraction lines by CCGS Tully. Two OBS lines run parallel to the coast, and three are perpendicular to the coast; one perpendicular line is located off Southeast Alaska, one is off Haida Gwaii, British Columbia, and another is located in Dixon Entrance. Please see Figure 1 for all location references. Following refraction shooting of a single line, short-period instruments on that line would be recovered, serviced, and redeployed on a subsequent refraction line while MCS data would be acquired by the Langseth. MCS lines would be acquired off Southeast Alaska, Haida Gwaii, and Dixon Entrance. The coast-parallel OBS refraction transect nearest to shore would only be surveyed once at OBS shot spacing. The other coast-parallel OBS refraction transect (on the ocean side) would be acquired twice, once during refraction and once during reflection surveys. In addition, portions of the three coast-perpendicular OBS refraction lines would also be surveyed twice, once for OBS shot spacing and once for MCS shot spacing. The coincident reflection/refraction profiles that run parallel to the coast would be acquired in multiple segments to ensure straight-line geometry. Sawtooth transits during which seismic data would be acquired would take place between transect lines when possible; otherwise, boxcar turns would be performed to save time. Both reflection and refraction surveys would use the same airgun array with the same discharge volume. There could be additional seismic operations associated with turns, airgun testing, and repeat coverage of any areas where initial data quality is sub-standard, and 25 percent has been added to the assumed survey line-kms to account for this potential. Note that the location of some tracklines has been modified from the original proposal as represented in Figure 1 and reflected in the take estimation analysis (see Estimated Take). However, these minor modifications do not substantively impact the location of survey effort or the proportion of survey effort in different depth bins and, therefore, the original take estimates remain accurate. In addition to the operations of the airgun array, a multibeam echosounder (MBES), a sub-bottom profiler (SBP), and an Acoustic Doppler Current Profiler (ADCP) would be operated from R/V Langseth continuously during the seismic surveys, but not during transit to and from the survey area. Take of marine mammals is not expected to occur incidental to use of the MBES, SBP, or ADCP because they will be operated only during seismic acquisition, and it is assumed that, during simultaneous operations of the airgun array and the other sources, any marine mammals close enough to be affected by the MBES, SBP, and ADCP would already be affected by the airguns. However, whether or not the airguns are operating simultaneously with the other sources, given the other sources' characteristics ( e.g., narrow downward-directed beam), marine mammals would experience no more than one or two brief ping exposures from them, if any exposure were to occur. Proposed mitigation, monitoring, and reporting measures are described in detail later in this document (please see Proposed Mitigation and Proposed Monitoring and Reporting). Description of Marine Mammals in the Area of Specified Activities Sections 3 and 4 of the application summarize available information regarding status and trends, distribution and habitat preferences, and behavior and life history, of the potentially affected species. Additional information regarding population trends and threats may be found in NMFS' Stock Assessment Reports (SARs; www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments ) and more general information about these species ( e.g., physical and behavioral descriptions) may be found on NMFS' website ( www.fisheries.noaa.gov/find-species ). Table 1 lists all species with expected potential for occurrence in the survey area and summarizes information related to the population or stock, including regulatory status under the MMPA and Endangered Species Act (ESA) and potential biological removal (PBR), where known. For taxonomy, we follow Committee on Taxonomy (2020). PBR is defined by the MMPA as the maximum number of animals, not including natural mortalities, that may be removed from a marine mammal stock while allowing that stock to reach or maintain its optimum sustainable population (as described in NMFS's SARs). While no mortality is anticipated or authorized here, PBR and annual serious injury and mortality from anthropogenic sources are included here as gross indicators of the status of the species and other threats. Marine mammal abundance estimates presented in this document represent the total number of individuals that make up a given stock or the total number estimated within a particular study or survey area. NMFS' stock abundance estimates for most species represent the total estimate of individuals within the geographic area, if known, that comprises that stock. For some species, this geographic area may extend beyond U.S. waters. All managed stocks in this region are assessed in NMFS' U.S. Pacific and Alaska SARs. All MMPA stock information presented in Table 1 is the most recent available at the time of publication and is available in the 2019 SARs (Caretta et al., 2020; Muto et al., 2020) and draft 2020 SARs (available online at: www.fisheries.noaa.gov/national/marine-mammal-protection/draft-marine-mammal-stock-assessment-reports ). Where available, abundance and status information is also presented for marine mammals in British Columbia waters. Twenty-one species (with 28 managed stocks) are considered to have the potential to occur in the proposed survey area. Species that could potentially occur in the proposed research area but are not likely to be harassed due to the rarity of their occurrence ( i.e., are considered extralimital or rare visitors to southeast Alaska/northern British Columbia) are described briefly but omitted from further analysis. These generally include species that do not normally occur in the area but for which there are one or more occurrence records that are considered beyond the normal range of the species. These species include pygmy sperm whale ( Kogia breviceps ), dwarf sperm whale ( K. sima ), Blainville's beaked whale ( Mesoplodon densirostris ), Hubbs' beaked whale ( Mesoplodon carlhubbsi ), false killer whale ( Pseudorca crassidens ), short-finned pilot whale ( Globicephala macrorhynchus ), common bottlenose dolphin ( Tursiops truncatus ), common dolphin ( Delphius delphis ), striped dolphin ( Stenella coeruleoalba ), and rough-toothed dolphin ( Steno bredanensis ), which are all typically distributed further south in the California Current ecosystem, and beluga whales ( Delphinapterus leucas ), which are found further north, with a population in Yakutat Bay. The North Pacific right whale ( Eubalaena japonica ) historically occurred across the North Pacific Ocean in subpolar to temperate waters, including waters off the coast of British Columbia (Scarff, 1986; Clapham et al., 2004). Sightings of this endangered species are now extremely rare, occurring primarily in the Okhotsk Sea and the eastern Bering Sea (Brownell et al., 2001; Shelden et al., 2005; Wade et al., 2006; Zerbini et al., 2010). In 2013, two North Pacific right whale sightings were made off the coast of British Columbia (U.S. Department of the Navy, 2015). There have also been four sightings, each of a single North Pacific right whale, in California waters within approximately the last 30 years (most recently in 2017) (Carretta et al., 1994; Brownell et al., 2001; Price, 2017). There is a very low probability of encountering this species in the action area, and it is not discussed further. There are eight killer whale stocks recognized in the U.S. Pacific, with Southern Resident killer whales being the only ESA-listed population. Southern Resident killer whales primarily occur in the southern Strait of Georgia, Strait of Juan de Fuca, Puget Sound, and the southern half of the west coast of Vancouver Island (Carretta et al., 2020). However, they have been observed in southeast Alaska. In 2007, whales from L-pod were sighted off Chatham Strait, Alaska, the farthest north they have ever been documented (Carretta et al., 2020). During the summer, Southern Resident killer whales typically spend their time within the inland waters of Washington and southern British Columbia, south of the proposed survey area. There is a very low probability of encountering this stock in the action area, and it is not discussed further. In addition, the northern sea otter ( Enhydra lutris kenyoni ) is found in coastal waters of Alaska. However, this species is managed by the U.S. Fish and Wildlife Service and is not considered further in this document. Table 1—Marine Mammals That Could Occur in the Survey Area Common name Scientific name Stock ESA/ MMPA status; strategic (Y/N) 1 Stock abundance (CV, N min , most recent abundance survey) 2 British Columbia abundance 3 PBR Annual M/SI 4 Order Cetartiodactyla—Cetacea—Superfamily Mysticeti (baleen whales) Family Eschrichtiidae: Gray whale Eschrichtius robustus Eastern North Pacific (ENP) * -; N 26,960 (0.05; 25,849; 2016) 801 131 Western North Pacific (WNP) * E/D; Y 290 (n/a; 271; 2016) 0.12 Unk Family Balaenopteridae (rorquals): Humpback whale Megaptera novaeangliae kuzira Central North Pacific (CNP) * E/D; Y 10,103 (0.3; 7,891; 2006) 1,029 83 26 Minke whale Balaenoptera acutorostrata scammoni Alaska * -; N Unknown 522 Undet. 0 Sei whale B. borealis borealis ENP E/D; Y 519 (0.4; 374; 2014) 0.75 ≥0.2 Fin whale B. physalus physalus Northeast Pacific * E/D; Y Unknown 329 Undet. 0.6 Blue whale B. musculus musculus ENP E/D; Y 1,496 (0.44; 1,050; 2014) 7 1.2 ≥19.4 Superfamily Odontoceti (toothed whales, dolphins, and porpoises) Family Physeteridae: Sperm whale Physeter macrocephalus North Pacific * E/D; Y Unknown Undet. 3.5 Family Ziphiidae (beaked whales): Cuvier's beaked whale Ziphius cavirostris Alaska * -; N Unknown Undet. 0 Baird's beaked whale Berardius bairdii Alaska * -; N Unknown Undet. 0 Stejneger's beaked whale Mesoplodon stejnegeri Alaska * -; N Unknown Undet. 0 Family Delphinidae: Pacific white-sided dolphin Lagenorhynchus obliquidens North Pacific 6 -; N 26,880 (n/a; 26,880; 1990) 22,160 Undet. 0 Northern right whale dolphin Lissodelphis borealis CA/OR/WA -; N 26,556 (0.44; 18,608; 2014) 179 3.8 Risso's dolphin Grampus griseus CA/OR/WA -; N 6,336 (0.32; 4,817; 2014) 46 ≥3.7 Killer whale Orcinus orca 5 ENP Offshore -; N 300 (0.1; 276; 2012) 371 2.8 0 ENP Gulf of Alaska, Aleutian Islands, and Bering Sea Transient -; N 587 (n/a; 2012) 5.9 0.8 ENP West Coast Transient -; N 349 (n/a; 2018) 3.5 0.4 ENP Alaska Resident -; N 2,347 (n/a; 2012) 24 1 Northern Resident -; N 302 (n/a; 2018) 2.2 0.2 Family Phocoenidae (porpoises): Harbor porpoise Phocoena phocoena vomerina Southeast Alaska * -; Y Unknown 8,091 Undet. 34 Dall's porpoise Phocoenoides dalli dalli Alaska 6 -; N 83,400 (0.097; n/a; 1991) 5,303 Undet. 38 Order Carnivora—Superfamily Pinnipedia Family Otariidae (eared seals and sea lions): Northern fur seal Callorhinus ursinus Pribilof Islands/Eastern Pacific D; Y 608,143 (0.2; 514,738; 2018) 11,067 387 California sea lion Zalophus californianus United States -/-; N 257,606 (N/A, 233,515, 2014) 14,011 ≥321 Steller sea lion Eumetopias jubatus jubatus Western U.S. * E/D; Y 52,932 (n/a; 2019) 15,348 318 255 E. j. monteriensis Eastern U.S. * -/-; N 43,201 (n/a; 2017) 2,592 112 Family Phocidae (earless seals): Harbor seal Phoca vitulina richardii Sitka/Chatham Strait -; N 13,289 (n/a; 11,883; 2015) 24,916 356 77 Dixon/Cape Decision -; N 23,478 (n/a; 21,453; 2015) 644 69 Clarence Strait -; N 27,659 (n/a; 24,854; 2015) 746 40 Northern elephant seal Mirounga angustirostris California Breeding -; N 179,000 (n/a; 81,368; 2010) 4,882 8.8 * Stocks marked with an asterisk are addressed in further detail in text below. 1 Endangered Species Act (ESA) status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed under the ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality exceeds PBR or which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed under the ESA is automatically designated under the MMPA as depleted and as a strategic stock. 2 NMFS marine mammal stock assessment reports at: www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments. CV is coefficient of variation; N min is the minimum estimate of stock abundance. In some cases, CV is not applicable. For most stocks of killer whales, the abundance values represent direct counts of individually identifiable animals; therefore there is only a single abundance estimate with no associated CV. For certain stocks of pinnipeds, abundance estimates are based upon observations of animals (often pups) ashore multiplied by some correction factor derived from knowledge of the species' (or similar species') life history to arrive at a best abundance estimate; therefore, there is no associated CV. In these cases, the minimum abundance may represent actual counts of all animals ashore. 3 Total abundance estimates for animals in British Columbia based on surveys of the Strait of Georgia, Johnstone Strait, Queen Charlotte Sound, Hecate Strait, and Dixon Entrance. This column represents estimated abundance of animals in British Columbia, where available, but does not necessarily represent additional stocks. Please see Best et al. (2015) and Pitcher et al. (2007) for additional information. 4 These values, found in NMFS's SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined ( e.g., commercial fisheries, subsistence hunting, ship strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value. All M/SI values are as presented in the draft 2020 SARs. 5 Transient and resident killer whales are considered unnamed subspecies (Committee on Taxonomy, 2020). 6 Abundance estimates for these stocks are not considered current. PBR is therefore considered undetermined for these stocks, as there is no current minimum abundance estimate for use in calculation. We nevertheless present the most recent abundance estimates, as these represent the best available information for use in this document. 7 This stock is known to spend a portion of time outside the U.S. EEZ. Therefore, the PBR presented here is the allocation for U.S. waters only and is a portion of the total. The total PBR for blue whales is 2.1 (7/12 allocation for U.S. waters). Annual M/SI presented for these species is for U.S. waters only. Table 1 denotes the status of species and stocks under the U.S. MMPA and ESA. We note also that under Canada's Species at Risk Act, the sei whale and blue whale are listed as endangered; the fin whale and northern resident, offshore, and transient populations of killer whales are listed as threatened; and the humpback whale, harbor porpoise, and Steller sea lion are considered species of special concern. Two populations of gray whales are recognized, eastern and western North Pacific (ENP and WNP). WNP whales are known to feed in the Okhotsk Sea and off of Kamchatka before migrating south to poorly known wintering grounds, possibly in the South China Sea. The two populations have historically been considered geographically isolated from each other; however, data from satellite-tracked whales indicate that there is some overlap between the stocks. Two WNP whales were tracked from Russian foraging areas along the Pacific rim to Baja California (Mate et al., 2011), and, in one case where the satellite tag remained attached to the whale for a longer period, a WNP whale was tracked from Russia to Mexico and back again (IWC, 2012). A number of whales are known to have occurred in the eastern Pacific through comparisons of ENP and WNP photo-identification catalogs (IWC, 2012; Weller et al., 2011; Burdin et al., 2011). Therefore, a portion of the WNP population is assumed to migrate, at least in some years, to the eastern Pacific during the winter breeding season. Based on guidance provided through interagency consultation under section 7 of the ESA, approximately 0.1 percent of gray whales occurring in southeast Alaska and northern British Columbia are likely to be from the Western North Pacific stock; the rest would be from the Eastern North Pacific stock. Prior to 2016, humpback whales were listed under the ESA as an endangered species worldwide. Following a 2015 global status review (Bettridge et al., 2015), NMFS delineated 14 distinct population segments (DPS) with different listing statuses (81 FR 62259; September 8, 2016) pursuant to the ESA. The DPSs that occur in U.S. waters do not necessarily equate to the existing stocks designated under the MMPA and shown in Table 1. In the eastern North Pacific, three humpback whale DPSs may occur: The Hawaii DPS (not listed), Mexico DPS (threatened), and Central America DPS (endangered). Individuals encountered in the proposed survey area would likely be from the Hawaii DPS, followed by the Mexico DPS; individuals from the Central America DPS are unlikely to feed in northern British Columbia and Southeast Alaska (Ford et al., 2014). According to Wade (2017), in southeast Alaska and northern British Columbia, encountered whales are most likely to be from the Hawaii DPS (96.1 percent), but could be from the Mexico DPS (3.8 percent). Although no comprehensive abundance estimate is available for the Alaska stock of minke whales, recent surveys provide estimates for portions of the stock's range. A 2010 survey conducted on the eastern Bering Sea shelf produced a provisional abundance estimate of 2,020 (CV = 0.73) whales (Friday et al., 2013). This estimate is considered provisional because it has not been corrected for animals missed on the trackline, animals submerged when the ship passed, or responsive movement. Additionally, line-transect surveys were conducted in shelf and nearshore waters (within 30-45 nautical miles of land) in 2001-2003 between the Kenai Peninsula (150° W) and Amchitka Pass (178° W). Minke whale abundance was estimated to be 1,233 (CV = 0.34) for this area (also not been corrected for animals missed on the trackline) (Zerbini et al., 2006). The majority of the sightings were in the Aleutian Islands, rather than in the Gulf of Alaska, and in water shallower than 200 m. These estimates cannot be used as an estimate of the entire Alaska stock of minke whales because only a portion of the stock's range was surveyed. Similarly, although a comprehensive abundance estimate is not available for the northeast Pacific stock of fin whales, provisional estimates representing portions of the range are available. The same 2010 survey of the eastern Bering Sea shelf provided an estimate of 1,061 (CV = 0.38) fin whales (Friday et al., 2013). The estimate is not corrected for missed animals, but is expected to be robust as previous studies have shown that only small correction factors are needed for fin whales (Barlow, 1995). Zerbini et al. (2006) produced an estimate of 1,652 (95 percent CI: 1,142-2,389) fin whales for the area described above. Current and historical estimates of the abundance of sperm whales in the North Pacific are considered unreliable, and caution should be exercised in interpreting published estimates (Muto et al., 2017). However, Kato and Miyashita (1998) produced an abundance estimate of 102,112 (CV = 0.155) sperm whales in the western North Pacific (believed to be positively biased). The number of sperm whales occurring within Alaska waters is unknown. Very little information is available regarding beaked whale stocks in Alaska, with no reliable abundance estimates available for any stock. Sightings of all beaked whale species are rare in Alaska, and their presence and distribution have mostly been inferred from stranding data. During long-term passive acoustic monitoring conducted at five sites in the Gulf of Alaska from 2011-15, all three species were detected at three sites located on the continental slope and offshore seamounts (Rice et al., 2021). There was no clear diel or interannual pattern for any species at any site. However, a different species was predominant at each site and, when detected at the same locations, detection peaks were all seasonally offset, demonstrating some degree of habitat partitioning. The authors noted that detections for all three beaked whale species were low throughout the summer. Stranding records exist for all three species of beaked whale in the survey area. Using 2010-2012 survey data for the inland waters of southeast Alaska, Dahlheim et al. (2015) calculated a combined abundance estimate for harbor porpoise in the northern (including Cross Sound, Icy Strait, Glacier Bay, Lynn Canal, Stephens Passage, and Chatham Strait) and southern (including Frederick Sound, Sumner Strait, Wrangell and Zarembo Islands, and Clarence Strait as far south as Ketchikan) regions of the inland waters of 975 (95 percent CI = 857-1,109). This abundance estimate was subsequently corrected for detection biases, which are expected to be high for harbor porpoise (Muto et al., 2020). The resulting abundance estimates are 553 harbor porpoise (CV = 0.13) in the northern inland waters and 801 harbor porpoise (CV = 0.15) in the southern inland waters (Muto et al., 2020). The Steller sea lion ranges from Japan, through the Okhotsk and Bering Seas, to central California. It consists of two morphologically, ecologically, and behaviorally separate DPSs: The Eastern, which includes sea lions in southeast Alaska, British Columbia, Washington, Oregon, and California; and the Western, which includes sea lions in all other regions of Alaska, as well as Russia and Japan. At the time of their initial listing under the ESA, Steller sea lions were considered a single population listed as threatened. In 1997, following a status review, NMFS established two DPSs of Steller sea lions, and issued a final determination to list the Western DPS as endangered under the ESA. The Eastern DPS of Steller sea lion was delisted in 2013. According to Hastings et al. (2020), approximately 2.2 percent of Steller sea lions occurring in the proposed action area are likely to be from the Western DPS; the rest would be from the Eastern DPS. Important Habitat Several biologically important areas (BIA) for marine mammals are recognized in southeast Alaska, and critical habitat is designated in southeast Alaska for the Steller sea lion (58 FR 45269; August 27, 1993) and the Mexico DPS of humpback whale (86 FR 21082; April 21, 2021). Note that although the eastern DPS of Steller sea lion was delisted in 2013, the change in listing status does not affect the designated critical habitat. Critical habitat is defined by section 3 of the ESA as (1) the specific areas within the geographical area occupied by the species, at the time it is listed, on which are found those physical or biological features (a) essential to the conservation of the species and (b) which may require special management considerations or protection; and (2) specific areas outside the geographical area occupied by the species at the time it is listed, upon a determination by the Secretary that such areas are essential for the conservation of the species. Mexico DPS humpback whale critical habitat includes marine waters in Washington, Oregon, California, and Alaska. Only the areas designated in southeast Alaska fall within the survey area. The relevant designated critical habitat (Unit 10) extends from 139°24′ W, southeastward to the U.S. border with Canada. The area also extends offshore to a boundary drawn along the 2,000-m isobath. The essential feature for Mexico DPS humpback whale critical habitat is prey species, primarily euphausiids and small pelagic schooling fishes of sufficient quality, abundance, and accessibility within humpback whale feeding areas to support feeding and population growth. This area was drawn to encompass well-established feeding grounds in southeast Alaska and an identified feeding BIA (86 FR 21082; April 21, 2021). Humpback whales occur year-round in this unit, with highest densities occurring in summer and fall (Baker et al., 1985, 1986). Critical habitat for humpback whales has been designated under Canadian law in four locations in British Columbia (DFO, 2013), including in the waters of the survey area off Haida Gwaii (Langara Island and Southeast Moresby Island). These areas show persistent aggregations of humpback whales and have features such as prey availability, suitable acoustic environment, water quality, and physical space that allow for feeding, foraging, socializing, and resting (DFO, 2013). Designated Steller sea lion critical habitat includes terrestrial, aquatic, and air zones that extend 3,000 ft (0.9 km) landward, seaward, and above each major rookery and major haul-out in Alaska. Within the survey area, critical habitat is located on islands off the coast of southeast Alaska ( e.g., Sitka, Coronation Island, Noyes Island, and Forrester Island). The physical and biological features identified for the aquatic areas of Steller sea lion designated critical habitat that occur within the survey area are those that support foraging, such as adequate prey resources and available foraging habitat. The proposed survey tracklines do not directly overlap any areas of Steller sea lion critical habitat, though the extent of the estimated ensonified area associated with the survey would overlap with units of Steller sea lion critical habitat. However, the brief duration of ensonification for any critical habitat unit leads us to conclude that any impacts on Steller sea lion habitat would be insignificant and would not affect the conservation value of the critical habitat. For humpback whales, seasonal feeding BIAs for spring (March-May), summer (June-August), and fall (September-November) are recognized in southeast Alaska (Ferguson et al., 2015). It should be noted that the aforementioned designated critical habitat in the survey area was based in large part on the same information that informed an understanding of the BIAs. Though the BIAs are not synonymous with critical habitat designated under the ESA, they were regarded by the humpback whale critical habitat review team as an important source of information and informative to their review of areas that meet the definition of critical habitat for humpback whales (86 FR 21082; April 21, 2021). The aforementioned southeast Alaska unit of designated critical habitat encompasses the BIAs, with the offshore and nearshore boundaries corresponding with the BIA boundary. A separate feeding BIA is recognized in southeast Alaska for gray whales. Once considered only a migratory pathway, the Gulf of Alaska is now known to provide foraging and overwintering habitat for ENP gray whales (Ferguson et al., 2015). Based on the regular occurrence of feeding gray whales (including repeat sightings of individuals across years) off southeast Alaska, an area off of Sitka is recognized. The greatest densities of gray whales on the feeding area in southeast Alaska occur from May to November. However, this area is located to the north of the proposed survey area and would not be expected to be meaningfully impacted by the survey activities. A separate migratory BIA is recognized as extending along the continental shelf throughout the Gulf of Alaska. During their annual migration, most gray whales pass through the Gulf of Alaska in the fall (November through January; southbound) and again in the spring (March through May; northbound) (Ferguson et al., 2015). Therefore, the planned survey would not be expected to impact gray whale migratory habitat due to the timing of the survey in late summer. No important behaviors of gray whales in either the feeding or migratory BIAs are expected to be affected. For more information on BIAs, please see Ferguson et al. (2015) or visit https://oceannoise.noaa.gov/biologically-important-areas. Unusual Mortality Events (UME) A UME is defined under the MMPA as “a stranding that is unexpected; involves a significant die-off of any marine mammal population; and demands immediate response.” For more information on UMEs, please visit: www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-unusual-mortality-events. There is a currently ongoing UME affecting gray whales throughout their migratory range. Since January 1, 2019, elevated gray whale strandings have occurred along the west coast of North America from Mexico through Alaska. As of May 6, 2021, there have been a total of 454 whales reported in the event, with approximately 218 dead whales in Mexico, 218 whales in the United States (62 in California; 10 in Oregon; 53 in Washington, 93 in Alaska), and 18 whales in British Columbia, Canada. For the United States, the historical 18-year 5-month average (Jan-May) is 14.8 whales for the four states for this same time-period. Several dead whales have been emaciated with moderate to heavy whale lice (cyamid) loads. Necropsies have been conducted on a subset of whales with additional findings of vessel strike in three whales and entanglement in one whale. In Mexico, 50-55 percent of the free-ranging whales observed in the lagoons in winter have been reported as “skinny” compared to the annual average of 10-12 percent “skinny” whales normally seen. The cause of the UME is as yet undetermined. For more information, please visit: www.fisheries.noaa.gov/national/marine-life-distress/2019-2020-gray-whale-unusual-mortality-event-along-west-coast-and. Another recent, notable UME involved large whales and occurred in the western Gulf of Alaska and off of British Columbia, Canada. Beginning in May 2015, elevated large whale mortalities (primarily fin and humpback whales) occurred in the areas around Kodiak Island, Afognak Island, Chirikof Island, the Semidi Islands, and the southern shoreline of the Alaska Peninsula. Although most carcasses have been non-retrievable as they were discovered floating and in a state of moderate to severe decomposition, the UME is likely attributable to ecological factors, i.e., the 2015 El Niño, “warm water blob,” and the Pacific Coast domoic acid bloom. The UME was closed in 2016. More information is available online at www.fisheries.noaa.gov/national/marine-life-distress/2015-2016-large-whale-unusual-mortality-event-western-gulf-alaska. Marine Mammal Hearing Hearing is the most important sensory modality for marine mammals underwater, and exposure to anthropogenic sound can have deleterious effects. To appropriately assess the potential effects of exposure to sound, it is necessary to understand the frequency ranges marine mammals are able to hear. Current data indicate that not all marine mammal species have equal hearing capabilities ( e.g., Richardson et al., 1995; Wartzok and Ketten, 1999; Au and Hastings, 2008). To reflect this, Southall et al. (2007) recommended that marine mammals be divided into functional hearing groups based on directly measured or estimated hearing ranges on the basis of available behavioral response data, audiograms derived using auditory evoked potential techniques, anatomical modeling, and other data. Note that no direct measurements of hearing ability have been successfully completed for mysticetes ( i.e., low-frequency cetaceans). Subsequently, NMFS (2018) described generalized hearing ranges for these marine mammal hearing groups. Generalized hearing ranges were chosen based on the approximately 65 decibel (dB) threshold from the normalized composite audiograms, with the exception for lower limits for low-frequency cetaceans where the lower bound was deemed to be biologically implausible and the lower bound from Southall et al. (2007) retained. Marine mammal hearing groups and their associated hearing ranges are provided in Table 2. Table 2—Marine Mammal Hearing Groups [NMFS, 2018] Hearing group Generalized hearing range * Low-frequency (LF) cetaceans (baleen whales) 7 Hz to 35 kHz. Mid-frequency (MF) cetaceans (dolphins, toothed whales, beaked whales, bottlenose whales) 150 Hz to 160 kHz. High-frequency (HF) cetaceans (true porpoises, Kogia, river dolphins, cephalorhynchid, Lagenorhynchus cruciger & L. australis ) 275 Hz to 160 kHz. Phocid pinnipeds (PW) (underwater) (true seals) 50 Hz to 86 kHz. Otariid pinnipeds (OW) (underwater) (sea lions and fur seals) 60 Hz to 39 kHz. * Represents the generalized hearing range for the entire group as a composite ( i.e., all species within the group), where individual species' hearing ranges are typically not as broad. Generalized hearing range chosen based on ~65 dB threshold from normalized composite audiogram, with the exception for lower limits for LF cetaceans (Southall et al. 2007) and PW pinniped (approximation). The pinniped functional hearing group was modified from Southall et al. (2007) on the basis of data indicating that phocid species have consistently demonstrated an extended frequency range of hearing compared to otariids, especially in the higher frequency range (Hemilä et al., 2006; Kastelein et al., 2009; Reichmuth and Holt, 2013). For more detail concerning these groups and associated frequency ranges, please see NMFS (2018) for a review of available information. Twenty-one marine mammal species (16 cetacean and 5 pinniped (3 otariid and 2 phocid) species) are considered herein. Of the cetacean species that may be present, six are classified as low-frequency cetaceans ( i.e., all mysticete species), eight are classified as mid-frequency cetaceans ( i.e., all delphinid and ziphiid species and the sperm whale), and two are classified as high-frequency cetaceans ( i.e., porpoises). Potential Effects of Specified Activities on Marine Mammals and Their Habitat This section includes a summary of the ways that L-DEO's specified activity may impact marine mammals and their habitat. Detailed descriptions of the potential effects of similar specified activities have been provided in other recent Federal Register notices, including for survey activities using the same methodology and over a similar amount of time, and affecting similar species ( e.g., 83 FR 29212, June 22, 2018; 84 FR 14200, April 9, 2019; 85 FR 19580, April 7, 2020). No significant new information is available, and we refer the reader to these documents for additional detail. The Estimated Take section includes a quantitative analysis of the number of individuals that are expected to be taken by L-DEO's activity. The Negligible Impact Analysis and Determination section considers the potential effects of the specified activity, the Estimated Take section, and the Proposed Mitigation section, to draw conclusions regarding the likely impacts of these activities on the reproductive success or survivorship of individuals and how those impacts on individuals are likely to impact marine mammal species or stocks. Background on Active Acoustic Sound Sources and Acoustic Terminology This section contains a brief technical background on sound, on the characteristics of certain sound types, and on metrics used in this proposal inasmuch as the information is relevant to the specified activity and to the discussion of the effects of the specified activity on marine mammals in this document. For general information on sound and its interaction with the marine environment, please see, e.g., Au and Hastings (2008); Richardson et al. (1995); Urick (1983). Sound travels in waves, the basic components of which are frequency, wavelength, velocity, and amplitude. Frequency is the number of pressure waves that pass by a reference point per unit of time and is measured in hertz or cycles per second. Wavelength is the distance between two peaks or corresponding points of a sound wave (length of one cycle). Higher frequency sounds have shorter wavelengths than lower frequency sounds, and typically attenuate (decrease) more rapidly, except in certain cases in shallower water. Amplitude is the height of the sound pressure wave or the “loudness” of a sound and is typically described using the relative unit of the decibel. A sound pressure level (SPL) in dB is described as the ratio between a measured pressure and a reference pressure (for underwater sound, this is 1 microPascal (μPa)), and is a logarithmic unit that accounts for large variations in amplitude. Therefore, a relatively small change in dB corresponds to large changes in sound pressure. The source level (SL) represents the SPL referenced at a distance of 1 m from the source (referenced to 1 μPa), while the received level is the SPL at the listener's position (referenced to 1 μPa). Root mean square (rms) is the quadratic mean sound pressure over the duration of an impulse. Root mean square is calculated by squaring all of the sound amplitudes, averaging the squares, and then taking the square root of the average (Urick, 1983). Root mean square accounts for both positive and negative values; squaring the pressures makes all values positive so that they may be accounted for in the summation of pressure levels (Hastings and Popper, 2005). This measurement is often used in the context of discussing behavioral effects, in part because behavioral effects, which often result from auditory cues, may be better expressed through averaged units than by peak pressures. Sound exposure level (SEL; represented as dB re 1 μPa2-s) represents the total energy in a stated frequency band over a stated time interval or event and considers both intensity and duration of exposure. The per-pulse SEL is calculated over the time window containing the entire pulse ( i.e., 100 percent of the acoustic energy). SEL is a cumulative metric; it can be accumulated over a single pulse, or calculated over periods containing multiple pulses. Cumulative SEL represents the total energy accumulated by a receiver over a defined time window or during an event. Peak sound pressure (also referred to as zero-to-peak sound pressure or 0-pk) is the maximum instantaneous sound pressure measurable in the water at a specified distance from the source and is represented in the same units as the rms sound pressure. When underwater objects vibrate or activity occurs, sound-pressure waves are created. These waves alternately compress and decompress the water as the sound wave travels. Underwater sound waves radiate in a manner similar to ripples on the surface of a pond and may be either directed in a beam or beams or may radiate in all directions (omnidirectional sources), as is the case for sound produced by the pile driving activity considered here. The compressions and decompressions associated with sound waves are detected as changes in pressure by aquatic life and man-made sound receptors such as hydrophones. Even in the absence of sound from the specified activity, the underwater environment is typically loud due to ambient sound, which is defined as environmental background sound levels lacking a single source or point (Richardson et al., 1995). The sound level of a region is defined by the total acoustical energy being generated by known and unknown sources. These sources may include physical ( e.g., wind and waves, earthquakes, ice, atmospheric sound), biological ( e.g., sounds produced by marine mammals, fish, and invertebrates), and anthropogenic ( e.g., vessels, dredging, construction) sound. A number of sources contribute to ambient sound, including wind and waves, which are a main source of naturally occurring ambient sound for frequencies between 200 hertz (Hz) and 50 kilohertz (kHz) (Mitson, 1995). In general, ambient sound levels tend to increase with increasing wind speed and wave height. Precipitation can become an important component of total sound at frequencies above 500 Hz, and possibly down to 100 Hz during quiet times. Marine mammals can contribute significantly to ambient sound levels, as can some fish and snapping shrimp. The frequency band for biological contributions is from approximately 12 Hz to over 100 kHz. Sources of ambient sound related to human activity include transportation (surface vessels), dredging and construction, oil and gas drilling and production, geophysical surveys, sonar, and explosions. Vessel noise typically dominates the total ambient sound for frequencies between 20 and 300 Hz. In general, the frequencies of anthropogenic sounds are below 1 kHz and, if higher frequency sound levels are created, they attenuate rapidly. The sum of the various natural and anthropogenic sound sources that comprise ambient sound at any given location and time depends not only on the source levels (as determined by current weather conditions and levels of biological and human activity) but also on the ability of sound to propagate through the environment. In turn, sound propagation is dependent on the spatially and temporally varying properties of the water column and sea floor, and is frequency-dependent. As a result of the dependence on a large number of varying factors, ambient sound levels can be expected to vary widely over both coarse and fine spatial and temporal scales. Sound levels at a given frequency and location can vary by 10-20 dB from day to day (Richardson et al., 1995). The result is that, depending on the source type and its intensity, sound from the specified activity may be a negligible addition to the local environment or could form a distinctive signal that may affect marine mammals. Details of source types are described in the following text. Sounds are often considered to fall into one of two general types: Pulsed and non-pulsed (defined in the following). The distinction between these two sound types is important because they have differing potential to cause physical effects, particularly with regard to hearing ( e.g., Ward, 1997 in Southall et al., 2007). Please see Southall et al. (2007) for an in-depth discussion of these concepts. The distinction between these two sound types is not always obvious, as certain signals share properties of both pulsed and non-pulsed sounds. A signal near a source could be categorized as a pulse, but due to propagation effects as it moves farther from the source, the signal duration becomes longer ( e.g., Greene and Richardson, 1988). Pulsed sound sources ( e.g., airguns, explosions, gunshots, sonic booms, impact pile driving) produce signals that are brief (typically considered to be less than one second), broadband, atonal transients (ANSI, 1986, 2005; Harris, 1998; NIOSH, 1998; ISO, 2003) and occur either as isolated events or repeated in some succession. Pulsed sounds are all characterized by a relatively rapid rise from ambient pressure to a maximal pressure value followed by a rapid decay period that may include a period of diminishing, oscillating maximal and minimal pressures, and generally have an increased capacity to induce physical injury as compared with sounds that lack these features. Non-pulsed sounds can be tonal, narrowband, or broadband, brief or prolonged, and may be either continuous or intermittent (ANSI, 1995; NIOSH, 1998). Some of these non-pulsed sounds can be transient signals of short duration but without the essential properties of pulses ( e.g., rapid rise time). Examples of non-pulsed sounds include those produced by vessels, aircraft, machinery operations such as drilling or dredging, vibratory pile driving, and active sonar systems. The duration of such sounds, as received at a distance, can be greatly extended in a highly reverberant environment. Airgun arrays produce pulsed signals with energy in a frequency range from about 10-2,000 Hz, with most energy radiated at frequencies below 200 Hz. The amplitude of the acoustic wave emitted from the source is equal in all directions ( i.e., omnidirectional), but airgun arrays do possess some directionality due to different phase delays between guns in different directions. Airgun arrays are typically tuned to maximize functionality for data acquisition purposes, meaning that sound transmitted in horizontal directions and at higher frequencies is minimized to the extent possible. Summary on Specific Potential Effects of Acoustic Sound Sources Underwater sound from active acoustic sources can include one or more of the following: Temporary or permanent hearing impairment, non-auditory physical or physiological effects, behavioral disturbance, stress, and masking. The degree of effect is intrinsically related to the signal characteristics, received level, distance from the source, and duration of the sound exposure. Marine mammals exposed to high-intensity sound, or to lower-intensity sound for prolonged periods, can experience hearing threshold shift (TS), which is the loss of hearing sensitivity at certain frequency ranges (Finneran, 2015). TS can be permanent (PTS), in which case the loss of hearing sensitivity is not fully recoverable, or temporary (TTS), in which case the animal's hearing threshold would recover over time (Southall et al., 2007). Due to the characteristics of airgun arrays as a distributed sound source, maximum estimated Level A harassment isopleths for species of certain hearing groups are assumed to fall within the near field of the array. For these species, i.e., mid-frequency cetaceans and all pinnipeds, animals in the vicinity of L-DEO's proposed seismic survey activity are unlikely to incur PTS. For low-frequency cetaceans and high-frequency cetaceans, potential exposures sufficient to cause low-level PTS may occur on the basis of cumulative exposure level and instantaneous exposure to peak pressure levels, respectively. However, when considered in conjunction with the potential for aversive behavior, relative motion of the exposed animal and the sound source, and the anticipated efficacy of the proposed mitigation requirements, a reasonable conclusion may be drawn that PTS is not a likely outcome for any species. However, we propose to authorize take by Level A harassment, where indicated by the quantitative exposure analysis, for species from the low- and high-frequency cetacean hearing groups. Please see Estimated Take and Proposed Mitigation for further discussion. Behavioral disturbance may include a variety of effects, including subtle changes in behavior ( e.g., minor or brief avoidance of an area or changes in vocalizations), more conspicuous changes in similar behavioral activities, and more sustained and/or potentially severe reactions, such as displacement from or abandonment of high-quality habitat. Behavioral responses to sound are highly variable and context-specific and any reactions depend on numerous intrinsic and extrinsic factors ( e.g., species, state of maturity, experience, current activity, reproductive state, auditory sensitivity, time of day), as well as the interplay between factors. Available studies show wide variation in response to underwater sound; therefore, it is difficult to predict specifically how any given sound in a particular instance might affect marine mammals perceiving the signal. In addition, sound can disrupt behavior through masking, or interfering with, an animal's ability to detect, recognize, or discriminate between acoustic signals of interest ( e.g., those used for intraspecific communication and social interactions, prey detection, predator avoidance, navigation). Masking occurs when the receipt of a sound is interfered with by another coincident sound at similar frequencies and at similar or higher intensity, and may occur whether the sound is natural ( e.g., snapping shrimp, wind, waves, precipitation) or anthropogenic ( e.g., shipping, sonar, seismic exploration) in origin. Sound may affect marine mammals through impacts on the abundance, behavior, or distribution of prey species ( e.g., crustaceans, cephalopods, fish, zooplankton) ( i.e., effects to marine mammal habitat). Prey species exposed to sound might move away from the sound source, experience TTS, experience masking of biologically relevant sounds, or show no obvious direct effects. The most likely impacts (if any) for most prey species in a given area would be temporary avoidance of the area. Surveys using active acoustic sound sources move through an area relatively quickly, limiting exposure to multiple pulses. In all cases, sound levels would return to ambient once a survey ends and the noise source is shut down and, when exposure to sound ends, behavioral and/or physiological responses are expected to end relatively quickly. Finally, the survey equipment will not have significant impacts to the seafloor and does not represent a source of pollution. Vessel Strike Vessel collisions with marine mammals, or ship strikes, can result in death or serious injury of the animal. These interactions are typically associated with large whales, which are less maneuverable than are smaller cetaceans or pinnipeds in relation to large vessels. The severity of injuries typically depends on the size and speed of the vessel, with the probability of death or serious injury increasing as vessel speed increases (Knowlton and Kraus, 2001; Laist et al., 2001; Vanderlaan and Taggart, 2007; Conn and Silber, 2013). Impact forces increase with speed, as does the probability of a strike at a given distance (Silber et al., 2010; Gende et al., 2011). The chances of a lethal injury decline from approximately 80 percent at 15 kn to approximately 20 percent at 8.6 kn. At speeds below 11.8 kn, the chances of lethal injury drop below 50 percent (Vanderlaan and Taggart, 2007). Ship strikes generally involve commercial shipping, which is much more common in both space and time than is geophysical survey activity and which typically involves larger vessels moving at faster speeds. Jensen and Silber (2004) summarized ship strikes of large whales worldwide from 1975-2003 and found that most collisions occurred in the open ocean and involved large vessels ( e.g., commercial shipping). Commercial fishing vessels were responsible for 3 percent of recorded collisions, while no such incidents were reported for geophysical survey vessels during that time period. For vessels used in geophysical survey activities, vessel speed while towing gear is typically only 4-5 kn. At these speeds, both the possibility of striking a marine mammal and the possibility of a strike resulting in serious injury or mortality are so low as to be discountable. At average transit speed for geophysical survey vessels (approximately 10 kn), the probability of serious injury or mortality resulting from a strike (if it occurred) is less than 50 percent (Vanderlaan and Taggart, 2007; Conn and Silber, 2013). However, the likelihood of a strike actually happening is again low given the smaller size of these vessels and generally slower speeds. We anticipate that vessel collisions involving seismic data acquisition vessels towing gear, while not impossible, represent unlikely, unpredictable events for which there are no preventive measures. Given the required mitigation measures, the relatively slow speeds of vessels towing gear, the presence of bridge crew watching for obstacles at all times (including marine mammals), the presence of marine mammal observers, and the small number of seismic survey cruises relative to commercial ship traffic, we believe that the possibility of ship strike is discountable and, further, that were a strike of a large whale to occur, it would be unlikely to result in serious injury or mortality. No incidental take resulting from ship strike is anticipated or proposed for authorization, and this potential effect of the specified activity will not be discussed further in the following analysis. The potential effects of L-DEO's specified survey activity are expected to be limited to Level B harassment consisting of behavioral harassment and/or temporary auditory effects and, for certain species of low- and high-frequency cetaceans only, low-level permanent auditory effects. No permanent auditory effects for any species belonging to other hearing groups, or significant impacts to marine mammal habitat, including prey, are expected. Estimated Take This section provides an estimate of the number of incidental takes proposed for authorization through this IHA, which will inform both NMFS' consideration of “small numbers” and the negligible impact determination. Harassment is the only type of take expected to result from these activities. Except with respect to certain activities not pertinent here, section 3(18) of 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). Authorized takes would primarily be by Level B harassment, as use of seismic airguns has the potential to result in disruption of behavioral patterns or temporary auditory effects for individual marine mammals. There is also some potential for auditory injury (Level A harassment) for low-frequency ( i.e., mysticetes) and high-frequency cetaceans ( i.e., porpoises). The proposed mitigation and monitoring measures are expected to minimize the severity of such taking to the extent practicable. As described previously, no serious injury or mortality is anticipated or proposed to be authorized for this activity. Below we describe how the take is estimated. Generally speaking, we estimate take by considering: (1) Acoustic thresholds above which NMFS believes the best available science indicates marine mammals will be behaviorally harassed or incur some degree of permanent hearing impairment; (2) the area or volume of water that will be ensonified above these levels in a day; (3) the density or occurrence of marine mammals within these ensonified areas; and, (4) and the number of days of activities. We note that while these basic factors can contribute to a basic calculation to provide an initial prediction of takes, additional information that can qualitatively inform take estimates is also sometimes available ( e.g., previous monitoring results or average group size). Below, we describe the factors considered here in more detail and present the proposed take estimate. Acoustic Thresholds NMFS uses acoustic thresholds that identify the received level of underwater sound above which exposed marine mammals would be reasonably expected to be behaviorally harassed (equated to Level B harassment) or to incur PTS of some degree (equated to Level A harassment). Level B Harassment —Though significantly driven by received level, the onset of behavioral disturbance from anthropogenic noise exposure is also informed to varying degrees by other factors related to the source ( e.g., frequency, predictability, duty cycle), the environment ( e.g., bathymetry), and the receiving animals (hearing, motivation, experience, demography, behavioral context) and can be difficult to predict (Southall et al., 2007, Ellison et al., 2012). NMFS uses a generalized acoustic threshold based on received level to estimate the onset of behavioral harassment. NMFS predicts that marine mammals may be behaviorally harassed ( i.e., Level B harassment) when exposed to underwater anthropogenic noise above received levels of 160 dB re 1 μPa (rms) for the impulsive sources ( i.e., seismic airguns) evaluated here. Level A Harassment —NMFS' Technical Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammal Hearing (Version 2.0) (Technical Guidance, 2018) identifies dual criteria to assess auditory injury (Level A harassment) to five different marine mammal groups (based on hearing sensitivity) as a result of exposure to noise from two different types of sources (impulsive or non-impulsive). L-DEO's proposed seismic survey includes the use of impulsive (seismic airguns) sources. These thresholds are provided in the table below. The references, analysis, and methodology used in the development of the thresholds are described in NMFS 2018 Technical Guidance, which may be accessed at www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance . Table 3—Thresholds Identifying the Onset of Permanent Threshold Shift Hearing group PTS onset acoustic thresholds * (received level) Impulsive Non-impulsive Low-Frequency (LF) Cetaceans Cell 1: L pk,flat : 219 dB; L , E,LF,24h : 183 dB Cell 2: L , E,LF,24h : 199 dB. Mid-Frequency (MF) Cetaceans Cell 3: L pk,flat : 230 dB; L , E,MF,24h : 185 dB Cell 4: L , E,MF,24h : 198 dB. High-Frequency (HF) Cetaceans Cell 5: L pk,flat : 202 dB; L , E,HF,24h : 155 dB Cell 6: L , E,HF,24h : 173 dB. Phocid Pinnipeds (PW) (Underwater) Cell 7: L pk,flat : 218 dB; L , E,PW,24h : 185 dB Cell 8: L , E,PW,24h : 201 dB. Otariid Pinnipeds (OW) (Underwater) Cell 9: L pk,flat : 232 dB; L , E,OW,24h : 203 dB Cell 10: L , E,OW,24h : 219 dB. * Dual metric acoustic thresholds for impulsive sounds: Use whichever results in the largest isopleth for calculating PTS onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure level thresholds associated with impulsive sounds, these thresholds should also be considered. Note: Peak sound pressure ( L pk ) has a reference value of 1 μPa, and cumulative sound exposure level ( L E ) has a reference value of 1μPa 2 s. In this Table, thresholds are abbreviated to reflect American National Standards Institute standards (ANSI 2013). However, peak sound pressure is defined by ANSI as incorporating frequency weighting, which is not the intent for this Technical Guidance. Hence, the subscript “flat” is being included to indicate peak sound pressure should be flat weighted or unweighted within the generalized hearing range. The subscript associated with cumulative sound exposure level thresholds indicates the designated marine mammal auditory weighting function (LF, MF, and HF cetaceans, and PW and OW pinnipeds) and that the recommended accumulation period is 24 hours. The cumulative sound exposure level thresholds could be exceeded in a multitude of ways ( i.e., varying exposure levels and durations, duty cycle). When possible, it is valuable for action proponents to indicate the conditions under which these acoustic thresholds will be exceeded. Ensonified Area Here, we describe operational and environmental parameters of the activity and other relevant information that will feed into identifying the area ensonified above the acoustic thresholds. L-DEO's modeling methodologies are described in greater detail in Appendix A of L-DEO's IHA application. The proposed 2D survey would acquire data using the 36-airgun array with a total discharge volume of 6,600 in 3 at a maximum tow depth of 12 m. L-DEO's modeling approach uses ray tracing for the direct wave traveling from the array to the receiver and its associated source ghost (reflection at the air-water interface in the vicinity of the array), in a constant-velocity half-space (infinite homogeneous ocean layer, unbounded by a seafloor). To validate the model results, L-DEO measured propagation of pulses from the 36-airgun array at a tow depth of 6 m in the Gulf of Mexico, for deep water (~1,600 m), intermediate water depth on the slope (~600-1,100 m), and shallow water (~50 m) (Tolstoy et al., 2009; Diebold et al., 2010). L-DEO collected a MCS data set from R/V Langseth (array towed at 9 m depth) on an 8-km streamer in 2012 on the shelf of the Cascadia Margin off of Washington in water up to 200 m deep that allowed Crone et al. (2014) to analyze the hydrophone streamer data (>1,100 individual shots). These empirical data were then analyzed to determine in situ sound levels for shallow and upper intermediate water depths. These data suggest that modeled radii were 2-3 times larger than the measured radii in shallow water. Similarly, data collected by Crone et al. (2017) during a survey off New Jersey in 2014 and 2015 confirmed that in situ measurements collected by the R/V Langseth hydrophone streamer were 2-3 times smaller than the predicted radii. L-DEO model results are used to determine the assumed radial distance to the 160-dB rms threshold for these arrays in deep water (>1,000 m) (down to a maximum water depth of 2,000 m). Water depths in the project area may be up to 2,800 m, but marine mammals in the region are generally not anticipated to dive below 2,000 m ( e.g., Costa and Williams, 1999). L-DEO typically derives estimated distances for intermediate water depths by applying a correction factor of 1.5 to the model results for deep water. In this case, the estimated radial distance for intermediate (100-1,000 m) and shallow (<100 m) water depths is taken from Crone et al. (2014), as these empirical data were collected in the same region as this proposed survey. A correction factor of 1.15 was applied to account for differences in array tow depth. The estimated distances to the Level B harassment isopleths for the array are shown in Table 4. Table 4—Predicted Radial Distances to Isopleths Corresponding to Level B Harassment Threshold Source and volume Tow depth (m) Water depth (m) Level B harassment zone (m) 36 airgun array; 6,600 in 3 12 >1000 1 6,733 100-1000 2 9,468 <100 2 12,650 1 Distance based on L-DEO model results. 2 Based on empirical data from Crone et al. (2014) with scaling. Predicted distances to Level A harassment isopleths, which vary based on marine mammal hearing groups, were calculated based on modeling performed by L-DEO using the NUCLEUS source modeling software program and the NMFS User Spreadsheet, described below. The acoustic thresholds for impulsive sounds ( e.g., airguns) contained in the Technical Guidance were presented as dual metric acoustic thresholds using both SEL cum and peak sound pressure metrics (NMFS 2018). As dual metrics, NMFS considers onset of PTS (Level A harassment) to have occurred when either one of the two metrics is exceeded ( i.e., metric resulting in the largest isopleth). The SEL cum metric considers both level and duration of exposure, as well as auditory weighting functions by marine mammal hearing group. In recognition of the fact that the requirement to calculate Level A harassment ensonified areas could be more technically challenging to predict due to the duration component and the use of weighting functions in the new SEL cum thresholds, NMFS developed an optional User Spreadsheet that includes tools to help predict a simple isopleth that can be used in conjunction with marine mammal density or occurrence to facilitate the estimation of take numbers. The values for SEL cum and peak SPL for the Langseth airgun arrays were derived from calculating the modified far-field signature. The farfield signature is often used as a theoretical representation of the source level. To compute the farfield signature, the source level is estimated at a large distance below the array ( e.g., 9 km), and this level is back projected mathematically to a notional distance of 1 m from the array's geometrical center. However, when the source is an array of multiple airguns separated in space, the source level from the theoretical farfield signature is not necessarily the best measurement of the source level that is physically achieved at the source (Tolstoy et al., 2009). Near the source (at short ranges, distances <1 km), the pulses of sound pressure from each individual airgun in the source array do not stack constructively, as they do for the theoretical farfield signature. The pulses from the different airguns spread out in time such that the source levels observed or modeled are the result of the summation of pulses from a few airguns, not the full array (Tolstoy et al., 2009). At larger distances, away from the source array center, sound pressure of all the airguns in the array stack coherently, but not within one time sample, resulting in smaller source levels (a few dB) than the source level derived from the farfield signature. Because the farfield signature does not take into account the large array effect near the source and is calculated as a point source, the modified farfield signature is a more appropriate measure of the sound source level for distributed sound sources, such as airgun arrays. L-DEO used the acoustic modeling methodology as used for estimating Level B harassment distances with a small grid step of 1 m in both the inline and depth directions. The propagation modeling takes into account all airgun interactions at short distances from the source, including interactions between subarrays, which are modeled using the NUCLEUS software to estimate the notional signature and MATLAB software to calculate the pressure signal at each mesh point of a grid. In order to more realistically incorporate the Technical Guidance's weighting functions over the seismic array's full acoustic band, unweighted spectrum data for the Langseth' s airgun array (modeled in 1 Hz bands) was used to make adjustments (dB) to the unweighted spectrum levels, by frequency, according to the weighting functions for each relevant marine mammal hearing group. These adjusted/weighted spectrum levels were then converted to pressures (μPa) in order to integrate them over the entire broadband spectrum, resulting in broadband weighted source levels by hearing group that could be directly incorporated within the User Spreadsheet ( i.e., to override the Spreadsheet's more simple weighting factor adjustment). Using the User Spreadsheet's “safe distance” methodology for mobile sources (described by Sivle et al., 2014) with the hearing group-specific weighted source levels, and inputs assuming spherical spreading propagation and information specific to the planned survey ( i.e., the 2.2 m/s source velocity and (worst-case) 23-s shot interval), potential radial distances to auditory injury zones were then calculated for SEL cum thresholds. Inputs to the User Spreadsheets in the form of estimated source levels are shown in Appendix A of L-DEO's application. User Spreadsheets used by L-DEO to estimate distances to Level A harassment isopleths for the airgun arrays are also provided in Appendix A of the application. Outputs from the User Spreadsheets in the form of estimated distances to Level A harassment isopleths for the survey are shown in Table 5. As described above, NMFS considers onset of PTS (Level A harassment) to have occurred when either one of the dual metrics (SEL cum and Peak SPL flat ) is exceeded ( i.e., metric resulting in the largest isopleth). Table 5—Modeled Radial Distances ( m ) to Isopleths Corresponding to Level A Harassment Thresholds Source (volume) Threshold Level A harassment zone (m) LF cetaceans MF cetaceans HF cetaceans Phocids Otariids 36-airgun array (6,600 in 3 ) SEL cum 320 0 1 10 0 Peak 39 14 268 44 11 Note that because of some of the assumptions included in the methods used ( e.g., stationary receiver with no vertical or horizontal movement in response to the acoustic source), isopleths produced may be overestimates to some degree, which will ultimately result in some degree of overestimation of Level A harassment. However, these tools offer the best way to predict appropriate isopleths when more sophisticated modeling methods are not available, and NMFS continues to develop ways to quantitatively refine these tools and will qualitatively address the output where appropriate. For mobile sources, such as the proposed seismic survey, the User Spreadsheet predicts the closest distance at which a stationary animal would not incur PTS if the sound source traveled by the animal in a straight line at a constant speed. Auditory injury is unlikely to occur for mid-frequency cetaceans, otariid pinnipeds, and phocid pinnipeds given very small modeled zones of injury for those species (all estimated zones less than 15 m for mid-frequency cetaceans and otariid pinnipeds, up to a maximum of 44 m for phocid pinnipeds), in context of distributed source dynamics. The source level of the array is a theoretical definition assuming a point source and measurement in the far-field of the source (MacGillivray, 2006). As described by Caldwell and Dragoset (2000), an array is not a point source, but one that spans a small area. In the far-field, individual elements in arrays will effectively work as one source because individual pressure peaks will have coalesced into one relatively broad pulse. The array can then be considered a “point source.” For distances within the near-field, i.e., approximately 2-3 times the array dimensions, pressure peaks from individual elements do not arrive simultaneously because the observation point is not equidistant from each element. The effect is destructive interference of the outputs of each element, so that peak pressures in the near-field will be significantly lower than the output of the largest individual element. Here, the relevant peak isopleth distances would in all cases be expected to be within the near-field of the array where the definition of source level breaks down. Therefore, actual locations within this distance of the array center where the sound level exceeds the relevant peak SPL thresholds would not necessarily exist. In general, Caldwell and Dragoset (2000) suggest that the near-field for airgun arrays is considered to extend out to approximately 250 m. In order to provide quantitative support for this theoretical argument, we calculated expected maximum distances at which the near-field would transition to the far-field (Table 5). For a specific array one can estimate the distance at which the near-field transitions to the far-field by: EN04JN21.004 with the condition that D >> λ, and where D is the distance, L is the longest dimension of the array, and λ is the wavelength of the signal (Lurton, 2002). Given that λ can be defined by: EN04JN21.005 where f is the frequency of the sound signal and v is the speed of the sound in the medium of interest, one can rewrite the equation for D as: EN04JN21.006 and calculate D directly given a particular frequency and known speed of sound (here assumed to be 1,500 meters per second in water, although this varies with environmental conditions). To determine the closest distance to the arrays at which the source level predictions in Table 5 are valid ( i.e., maximum extent of the near-field), we calculated D based on an assumed frequency of 1 kHz. A frequency of 1 kHz is commonly used in near-field/far-field calculations for airgun arrays (Zykov and Carr, 2014; MacGillivray, 2006; NSF and USGS, 2011), and based on representative airgun spectrum data and field measurements of an airgun array used on the Langseth, nearly all (greater than 95 percent) of the energy from airgun arrays is below 1 kHz (Tolstoy et al., 2009). Thus, using 1 kHz as the upper cut-off for calculating the maximum extent of the near-field should reasonably represent the near-field extent in field conditions. If the largest distance to the peak sound pressure level threshold was equal to or less than the longest dimension of the array ( i.e., under the array), or within the near-field, then received levels that meet or exceed the threshold in most cases are not expected to occur. This is because within the near-field and within the dimensions of the array, the source levels specified in Appendix A of L-DEO's application are overestimated and not applicable. In fact, until one reaches a distance of approximately three or four times the near-field distance the average intensity of sound at any given distance from the array is still less than that based on calculations that assume a directional point source (Lurton, 2002). The 6,600-in 3 airgun array planned for use during the proposed survey has an approximate diagonal of 28.8 m, resulting in a near-field distance of 138.7 m at 1 kHz (NSF and USGS, 2011). Field measurements of this array indicate that the source behaves like multiple discrete sources, rather than a directional point source, beginning at approximately 400 m (deep site) to 1 km (shallow site) from the center of the array (Tolstoy et al., 2009), distances that are actually greater than four times the calculated 140-m near-field distance. Within these distances, the recorded received levels were always lower than would be predicted based on calculations that assume a directional point source, and increasingly so as one moves closer towards the array (Tolstoy et al., 2009). Given this, relying on the calculated distance (138.7 m) as the distance at which we expect to be in the near-field is a conservative approach since even beyond this distance the acoustic modeling still overestimates the actual received level. Within the near-field, in order to explicitly evaluate the likelihood of exceeding any particular acoustic threshold, one would need to consider the exact position of the animal, its relationship to individual array elements, and how the individual acoustic sources propagate and their acoustic fields interact. Given that within the near-field and dimensions of the array source levels would be below those assumed here, we believe exceedance of the peak pressure threshold would only be possible under highly unlikely circumstances. In consideration of the received sound levels in the near-field as described above, we expect the potential for Level A harassment of mid-frequency cetaceans, otariid pinnipeds, and phocid pinnipeds to be de minimis, even before the likely moderating effects of aversion and/or other compensatory behaviors ( e.g., Nachtigall et al., 2018) are considered. We do not believe that Level A harassment is a likely outcome for any mid-frequency cetacean, otariid pinniped, or phocid pinniped and do not propose to authorize any Level A harassment for these species. Marine Mammal Occurrence In this section we provide the information about the presence, density, and group dynamics of marine mammals that will inform the take calculations. The Navy's Marine Species Density Database (DoN, 2019, 2021) is currently the most comprehensive compendium for density data available for the Gulf of Alaska (GOA) and is the only source of density data available for southeast Alaska. Habitat-based stratified marine mammal densities developed by the U.S. Navy for assessing potential impacts of training activities in the GOA (DoN, 2021; Rone et al., 2014, 2017) and at Behm Canal in southeast Alaska (DoN, 2019) represent the best available information for estimating potential marine mammal exposures. The Navy's GOA Temporary Marine Activities Area (TMAA) is situated south of Prince William Sound and east of Kodiak Island. The northern boundary of the TMAA is approximately 24 nautical miles south of the Kenai Peninsula. Behm Canal is approximately 45 km east of Ketchikan, AK, inshore of the proposed survey area in the same general part of southeast Alaska. In general, GOA density values were used for offshore (deep water depths) portions of the survey area, and Behm Canal density values were used for inshore (shallow and intermediate water depths) portions. For some species, no Behm Canal density information is available, and the GOA density value was applied to all water depths. Density values are provided in Table 6 and discussed in greater detail below. Table 6—Estimated Density Values by Water Depth [#/km 2 ] Species Shallow depth (<100 m) 1 Intermediate depth (100-1,000 m) 1 Deep depth (>1,000 m) 1 Gray whale 4 0.0486 0.0486 0 Humpback whale 3 0.0117 3 0.0117 4 0.0010 Blue whale 4 0.0001 0.0001 0.0005 Fin whale 3 0.0001 3 0.0001 4 0.0160 Sei whale 4 0.0004 0.0004 0.0004 Minke whale 3 0.0008 3 0.0008 4 0.0006 Sperm whale 4 0 0.0020 0.0013 Baird's beaked whale 4 0 0 0.0005 Stejneger's beaked whale 4 0 0 0.0021 Cuvier's beaked whale 4 0 0 0.0020 Pacific white-sided dolphin 3 0.0075 3 0.0075 4 0.0200 Northern right whale dolphin 5 0.0110 0.0276 0.0367 Risso's dolphin 2 0.0000 0.0000 0.0000 Killer whale 3 0.0057 3 0.0057 4 0.0020 Dall's porpoise 3 0.1210 3 0.1210 4 0.0370 Harbor porpoise 6 0.0330 0.0330 0 Northern fur seal 4 0.0661 0.0661 0.0661 California sea lion 3 0.0288 0.0288 0.0065 Steller sea lion 3 0.3162 4 0.0570 0 Northern elephant seal 4 0.0779 0.0779 0.0779 Harbor seal 3 0.7811 4 0.1407 0 1 A zero value indicates the species is not expected to occur in that depth stratum. 2 Nominal density value of 0.00001 applied to Risso's dolphin. 3 Source: DoN, 2019; 4 Source DoN, 2021; 5 Source: Becker et al. (2016); 6 Hobbs and Waite (2010). The Navy conducted comprehensive marine mammal surveys in theTMAA in 2009 and 2013. Additional survey effort was conducted in 2015. These surveys used systematic line-transect survey protocols including visual and acoustic detection methods (Rone et al., 2010, 2014, 2017). The data were collected in four strata that were designed to encompass the four distinct habitats within the TMAA and greater GOA: Inshore: All waters <1,000 m deep; Slope: From 1,000 m water depth to the Aleutian trench/subduction zone; Offshore: Waters offshore of the Aleutian trench/subduction zone; Seamount: Waters within defined seamount areas. Density values for the slope and seamount regions of the TMAA are not relevant for the survey area considered herein. There were insufficient sightings data from the 2009, 2013, and 2015 line-transect surveys to calculate reliable density estimates for certain cetacean species in the GOA. In these cases, other available information supported development of density estimates. Additional sources of information include summer 2003 cetacean surveys near the Kenai Peninsula, within Prince William Sound and around Kodiak Island (Waite, 2003 in DoN, 2021), summer 2010-2012 line-transect data collected over a broad area north of 40° N, south of the Aleutian Islands, and between 170° E and 135° W during the International Whaling Commission-Pacific Ocean Whale and Ecosystem Research cruises (Hakamada et al., 2017), and analysis of acoustic data from the 2013 Navy-funded survey effort in the TMAA (Yack et al., 2015). See DoN (2021) for additional detail. When seasonal densities were available, the calculated exposures were based on summer densities, which are most representative of the proposed survey timing. Pinniped numbers are commonly assessed by counting individuals at haul-outs or the number of pups weaned at rookeries. Translating these numbers to in-water densities presents challenges unique to pinnipeds. No in-water line transect survey data were available for harbor seal, Steller sea lion, or California sea lion in the GOA. Surveys conducted by Rone et al. (2014) recorded sightings of northern elephant seal and northern fur seal in the TMAA; however, these data were insufficient to estimate a density for northern elephant seal, and were not used for northern fur seal due to the availability of more recent data. To account for the lack of in-water survey data for pinnipeds, published abundance estimates used in the density calculations were adjusted using a species-specific haul-out factor to estimate an in-water abundance for each species based on haul-out behavior. The calculated in-water abundance and an area of distribution specific to each species was used to estimate a density. See DoN (2021) for additional information. For pinnipeds, where monthly density estimates were available, the highest value from July or August was applied as most representative of the proposed survey timing. Due to a lack of sighting data specific to the Behm Canal area, the Navy derived density estimates based on data collected from various surveys (cetaceans) and shore counts (pinnipeds) conducted within southeast Alaska and GOA. Pinniped density estimates for the Behm Canal region were additionally derived from publications, NMFS SARs, and consultation with subject matter experts (DoN, 2019). Systematic ship surveys conducted in southeast Alaska waters from 1991 to 2012 provided data to develop stratified line-transect density estimates for harbor porpoise and Dall's porpoise in regions overlapping a portion of the Behm Canal area (Dahlheim et al., 2015). Density information for the Behm Canal area is available for the following species: Minke whale, fin whale, humpback whale, Pacific white-sided dolphin, killer whale, harbor porpoise, Dall's porpoise, and for all potentially affected pinniped species. The general approach for cetaceans of applying Behm Canal density estimates to survey effort in shallow and intermediate depth strata and GOA offshore density estimates to the deep depth stratum was applied for species for which appropriate estimates were available: Humpback whale, fin whale, minke whale, Pacific white-sided dolphin, killer whale, and Dall's porpoise. Note that, for killer whales, Behm Canal densities are provided specific to transient and resident whales. We apply the higher transient killer whale density value to estimate killer whale exposures in shallow and intermediate water depths. Behm Canal pinniped densities would be expected to overestimate pinniped occurrence off the coast, and so were not used for intermediate-depth waters, but were applied to shallow waters where available. Certain species are not expected to occur in Behm Canal: Gray whale, blue whale, sei whale, sperm whale, beaked whales, northern fur seal, and northern elephant seal. For these species, we applied appropriate GOA density values to all depth strata ( i.e., inshore GOA values to shallow and intermediate water depths and offshore GOA density values to deep water depths). Note that, while DoN (2021) provides an inshore density estimate for sperm whales, that stratum corresponds to water depths <1,000 m. We assume here that sperm whales do not occur in shallow water depths (<100 m). Gray whale densities are provided for two zones, nearshore (0-2.25 nmi from shore) and offshore (from 2.25-20 nmi from shore), based on density information in Carretta et al. (2000) and zones based on data from Shelden and Laake (2002). DoN (2021) assumes that gray whales do not occur in the region >20 nmi from shore. The nearshore density is used here to represent shallow and intermediate water (<1,000 m deep). This approach assumes a higher density of gray whales across a larger area and is used as a precautionary approach. Harbor porpoise densities in DoN (2021) were derived from survey data collected in summer 1997 in southeast Alaska and 1998 in the Gulf of Alaska and included correction factors for both perception and availability bias (Hobbs and Waite, 2010). L-DEO proposed to use density information from Hobbs and Waite (2010) specific to southeast Alaska, which better represents the survey area than the GOA information presented for harbor porpoise in DoN (2021). Following DoN (2021), we assume harbor porpoise will not occur in deep water (>1,000 m). No regional density information is available for the northern right whale dolphin. Becker et al. (2016) used line-transect survey data collected between 1991 and 2009 to develop predictive habitat-based models of cetacean densities in the California Current Ecosystem (the region from Baja California to southern British Columbia). The modeled density estimates were available on the scale of 7 km by 10 km grid cells off California, Oregon, and Washington, and values were averaged for grid cells across Washington and Oregon corresponding with L-DEO's shallow, intermediate, and deep water survey strata. These density values were applied to the portion of the survey area off Canada to calculate estimated exposures, as northern right whale dolphins do not typically occur beyond the California Current. The Risso's dolphin is only rarely observed in or near the Navy's GOA survey area, and does not occur in Behm Canal, so minimal densities were used to represent their potential presence (DoN, 2021). For California sea lion, density data is available in DoN (2021); however, it is likely that these values would underestimate presence of California sea lions in the proposed survey area. Therefore, information available in DoN (2019) for the Offshore Northwest Training and Testing (NWTT) Area (off Washington/Oregon) in the month of August was used; densities for 0-40 km from shore were applied to shallow and intermediate water depths, and the density for 0-450 km from shore was used for deep water. The density for 40-70 km from shore was the lowest and was therefore not used. In British Columbia, several systematic surveys have been conducted in coastal waters ( e.g., Williams and Thomas 2007; Ford et al., 2010; Best et al., 2015; Harvey et al., 2017). Surveys in coastal as well as offshore waters were conducted by Fisheries and Oceans Canada (DFO) during 2002 to 2008. However, density estimates for the survey areas outside the U.S. EEZ, i.e., in the Canadian EEZ, were not readily available, so density estimates for U.S. waters were applied to the entire survey area. Take Calculation and Estimation Here we describe how the information provided above is brought together to produce a quantitative take estimate. In order to estimate the number of marine mammals predicted to be exposed to sound levels that would result in Level A or Level B harassment, radial distances from the airgun array to predicted isopleths corresponding to the Level A harassment and Level B harassment thresholds are calculated, as described above. Those radial distances are then used to calculate the area(s) around the airgun array predicted to be ensonified to sound levels that exceed the Level A and Level B harassment thresholds. The distance for the 160-dB threshold (based on L-DEO model results) was used to draw a buffer around every transect line in GIS to determine the total ensonified area in each depth category. Estimated incidents of exposure above Level A and Level B harassment criteria are presented in Table 7. For additional details regarding calculations of ensonified area, please see Appendix D of L-DEO's application. As noted previously, L-DEO has added 25 percent in the form of operational days, which is equivalent to adding 25 percent to the proposed line-kms to be surveyed. This accounts for the possibility that additional operational days are required, but likely results in an overestimate of actual exposures. As previously noted, NMFS cannot authorize incidental take under the MMPA that may occur within the territorial seas of foreign nations (from 0-12 nmi (22.2 km) from shore), as the MMPA does not apply in those waters. However, NMFS has still calculated the estimated level of incidental take in the entire activity area (including Canadian territorial waters) as part of the analysis supporting our determination under the MMPA that the activity will have a negligible impact on the affected species. The total estimated take in U.S. and Canadian waters is presented in Table 8 (see Negligible Impact Analysis and Determination). The estimated marine mammal exposures above harassment thresholds are generally assumed here to equate to take, and the estimates form the basis for our proposed take authorization numbers. For the species for which NMFS does not expect there to be a reasonable potential for take by Level A harassment to occur, i.e., mid-frequency cetaceans and all pinnipeds, the estimated exposures above Level A harassment thresholds have been added to the estimated exposures above the Level B harassment threshold to produce a total number of incidents of take by Level B harassment that is proposed for authorization. Estimated exposures and proposed take numbers for authorization are shown in Table 7. Regarding humpback whale take numbers, we assume that whales encountered will follow Wade (2017), i.e., that 96.1 percent of takes would accrue to the Hawaii DPS and 3.8 percent to the Mexico DPS. Of the estimated take of gray whales, and based on guidance provided through interagency consultation under section 7 of the ESA, we assume that 0.1 percent of encountered whales would be from the WNP stock and propose to authorize take accordingly. For Steller sea lions, 2.2 percent are assumed to belong to the western DPS (Hastings et al., 2020). Table 7—Estimated Taking by Level A and Level B Harassment, and Percentage of Population Species Stock 1 Estimated Level B harassment Estimated Level A harassment Proposed Level B harassment Proposed Level A harassment Total take Percent of stock 1 Gray whale WNP ENP 1,450 45 2 1,448 0 45 2 1,493 0.7 5.5 Humpback whale 403 14 403 14 417 4.1 Blue whale 31 1 31 1 32 2.1 Fin whale 2 873 44 873 44 917 n/a Sei whale 34 1 34 1 35 6.7 Minke whale 2 57 2 57 2 59 n/a Sperm whale 2 131 0 131 0 131 n/a Baird's beaked whale 2 29 0 29 0 29 n/a Stejneger's beaked whale 2 120 0 120 0 120 n/a Cuvier's beaked whale 2 114 0 114 0 114 n/a Pacific white-sided dolphin 1,371 3 1,374 0 1,374 5.1 Northern right whale dolphin 922 5 927 0 927 3.5 Risso's dolphin 3 1 0 22 0 22 0.3 Killer whale Offshore 290 0 290 0 290 96.7 GOA/BSAI Transient 49.4 WC Transient 83.1 AK Resident 12.4 Northern Resident 96.0 Dall's porpoise 5,661 178 5,661 178 5,839 7.0 Harbor porpoise 990 26 990 26 1,016 n/a Northern fur seal 5,804 8 5,812 0 5,812 1.0 California sea lion 1,256 1 1,258 0 1,258 0.5 Steller sea lion WDPS EDPS 2,433 2 54 2,381 0 0 54 2,381 0.1 5.5 Northern elephant seal 6,811 39 6,850 0 6,850 3.8 Harbor seal Sitka/Chatham Strait 5,992 21 6,012 0 6,012 45.2 Dixon/Cape Decision 25.6 Clarence Strait 21.7 1 In most cases, where multiple stocks are being affected, for the purposes of calculating the percentage of the stock impacted, the take is being analyzed as if all proposed takes occurred within each stock. Where necessary, additional discussion is provided in the Small Numbers section. 2 As noted in Table 1, there is no estimate of abundance available for these species. 3 Estimated exposure of one Risso's dolphin increased to group size of 22 (Barlow, 2016). Proposed Mitigation In order to issue an IHA under Section 101(a)(5)(D) of the MMPA, NMFS must set forth the permissible methods of taking pursuant to the activity, and other means of effecting the least practicable impact on the species or stock and its habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, and on the availability of the species or stock for taking for certain subsistence uses (latter not applicable for this action). NMFS regulations require applicants for incidental take authorizations to include information about the availability and feasibility (economic and technological) of equipment, methods, and manner of conducting the activity or other means of effecting the least practicable adverse impact upon the affected species or stocks and their habitat (50 CFR 216.104(a)(11)). In evaluating how mitigation may or may not be appropriate to ensure the least practicable adverse impact on species or stocks and their habitat, as well as subsistence uses where applicable, we carefully consider two primary factors: (1) The manner in which, and the degree to which, the successful implementation of the measure(s) is expected to reduce impacts to marine mammals, marine mammal species or stocks, and their habitat. This considers the nature of the potential adverse impact being mitigated (likelihood, scope, range). It further considers the likelihood that the measure will be effective if implemented (probability of accomplishing the mitigating result if implemented as planned), the likelihood of effective implementation (probability implemented as planned); and (2) The practicability of the measures for applicant implementation, which may consider such things as cost, impact on operations, and, in the case of a military readiness activity, personnel safety, practicality of implementation, and impact on the effectiveness of the military readiness activity. In order to satisfy the MMPA's least practicable adverse impact standard, NMFS has evaluated a suite of basic mitigation protocols for seismic surveys that are required regardless of the status of a stock. Additional or enhanced protections may be required for species whose stocks are in particularly poor health and/or are subject to some significant additional stressor that lessens that stock's ability to weather the effects of the specified activities without worsening its status. We reviewed seismic mitigation protocols required or recommended elsewhere ( e.g., HESS, 1999; DOC, 2013; IBAMA, 2018; Kyhn et al., 2011; JNCC, 2017; DEWHA, 2008; BOEM, 2016; DFO, 2008; GHFS, 2015; MMOA, 2016; Nowacek et al., 2013; Nowacek and Southall, 2016), recommendations received during public comment periods for previous actions, and the available scientific literature. We also considered recommendations given in a number of review articles ( e.g., Weir and Dolman, 2007; Compton et al., 2008; Parsons et al., 2009; Wright and Cosentino, 2015; Stone, 2015b). This exhaustive review and consideration of public comments regarding previous, similar activities has led to development of the protocols included here. Vessel-Based Visual Mitigation Monitoring Visual monitoring requires the use of trained observers (herein referred to as visual protected species observers (PSOs)) to scan the ocean surface for the presence of marine mammals. The area to be scanned visually includes primarily the exclusion zone (EZ), within which observation of certain marine mammals requires shutdown of the acoustic source, but also a buffer zone and, to the extent possible depending on conditions, the surrounding waters. The buffer zone means an area beyond the EZ to be monitored for the presence of marine mammals that may enter the EZ. During pre-start clearance monitoring ( i.e., before ramp-up begins), the buffer zone also acts as an extension of the EZ in that observations of marine mammals within the buffer zone would also prevent airgun operations from beginning ( i.e., ramp-up). The buffer zone encompasses the area at and below the sea surface from the edge of the 0-500 m EZ, out to a radius of 1,000 m from the edges of the airgun array (500-1,000 m). This 1,000-m zone (EZ plus buffer) represents the pre-start clearance zone. Visual monitoring of the EZ and adjacent waters is intended to establish and, when visual conditions allow, maintain zones around the sound source that are clear of marine mammals, thereby reducing or eliminating the potential for injury and minimizing the potential for more severe behavioral reactions for animals occurring closer to the vessel. Visual monitoring of the buffer zone is intended to (1) provide additional protection to naïve marine mammals that may be in the area during pre-start clearance, and (2) during airgun use, aid in establishing and maintaining the EZ by alerting the visual observer and crew of marine mammals that are outside of, but may approach and enter, the EZ. L-DEO must use dedicated, trained, NMFS-approved PSOs. The PSOs must have no tasks other than to conduct observational effort, record observational data, and communicate with and instruct relevant vessel crew with regard to the presence of marine mammals and mitigation requirements. PSO resumes shall be provided to NMFS for approval. At least one of the visual and two of the acoustic PSOs (discussed below) aboard the vessel must have a minimum of 90 days at-sea experience working in those roles, respectively, with no more than 18 months elapsed since the conclusion of the at-sea experience. One visual PSO with such experience shall be designated as the lead for the entire protected species observation team. The lead PSO shall serve as primary point of contact for the vessel operator and ensure all PSO requirements per the IHA are met. To the maximum extent practicable, the experienced PSOs should be scheduled to be on duty with those PSOs with appropriate training but who have not yet gained relevant experience. During survey operations ( e.g., any day on which use of the acoustic source is planned to occur, and whenever the acoustic source is in the water, whether activated or not), a minimum of two visual PSOs must be on duty and conducting visual observations at all times during daylight hours ( i.e., from 30 minutes prior to sunrise through 30 minutes following sunset). Visual monitoring of the pre-start clearance zone must begin no less than 30 minutes prior to ramp-up, and monitoring must continue until one hour after use of the acoustic source ceases or until 30 minutes past sunset. Visual PSOs shall coordinate to ensure 360° visual coverage around the vessel from the most appropriate observation posts, and shall conduct visual observations using binoculars and the naked eye while free from distractions and in a consistent, systematic, and diligent manner. PSOs shall establish and monitor the exclusion and buffer zones. These zones shall be based upon the radial distance from the edges of the acoustic source (rather than being based on the center of the array or around the vessel itself). During use of the acoustic source ( i.e., anytime airguns are active, including ramp-up), detections of marine mammals within the buffer zone (but outside the EZ) shall be communicated to the operator to prepare for the potential shutdown of the acoustic source. Visual PSOs will immediately communicate all observations to the on duty acoustic PSO(s), including any determination by the PSO regarding species identification, distance, and bearing and the degree of confidence in the determination. Any observations of marine mammals by crew members shall be relayed to the PSO team. During good conditions ( e.g., daylight hours; Beaufort sea state (BSS) 3 or less), visual PSOs shall conduct observations when the acoustic source is not operating for comparison of sighting rates and behavior with and without use of the acoustic source and between acquisition periods, to the maximum extent practicable. Visual PSOs may be on watch for a maximum of 4 consecutive hours followed by a break of at least one hour between watches and may conduct a maximum of 12 hours of observation per 24-hour period. Combined observational duties (visual and acoustic but not at same time) may not exceed 12 hours per 24-hour period for any individual PSO. Passive Acoustic Monitoring Acoustic monitoring means the use of trained personnel (sometimes referred to as passive acoustic monitoring (PAM) operators, herein referred to as acoustic PSOs) to operate PAM equipment to acoustically detect the presence of marine mammals. Acoustic monitoring involves acoustically detecting marine mammals regardless of distance from the source, as localization of animals may not always be possible. Acoustic monitoring is intended to further support visual monitoring (during daylight hours) in maintaining an EZ around the sound source that is clear of marine mammals. In cases where visual monitoring is not effective ( e.g., due to weather, nighttime), acoustic monitoring may be used to allow certain activities to occur, as further detailed below. PAM would take place in addition to the visual monitoring program. Visual monitoring typically is not effective during periods of poor visibility or at night, and even with good visibility, is unable to detect marine mammals when they are below the surface or beyond visual range. Acoustic monitoring can be used in addition to visual observations to improve detection, identification, and localization of cetaceans. The acoustic monitoring would serve to alert visual PSOs (if on duty) when vocalizing cetaceans are detected. It is only useful when marine mammals vocalize, but it can be effective either by day or by night, and does not depend on good visibility. It would be monitored in real time so that the visual observers can be advised when cetaceans are detected. The R/V Langseth will use a towed PAM system, which must be monitored by at a minimum one on duty acoustic PSO beginning at least 30 minutes prior to ramp-up and at all times during use of the acoustic source. Acoustic PSOs may be on watch for a maximum of 4 consecutive hours followed by a break of at least one hour between watches and may conduct a maximum of 12 hours of observation per 24-hour period. Combined observational duties (acoustic and visual but not at same time) may not exceed 12 hours per 24-hour period for any individual PSO. Survey activity may continue for 30 minutes when the PAM system malfunctions or is damaged, while the PAM operator diagnoses the issue. If the diagnosis indicates that the PAM system must be repaired to solve the problem, operations may continue for an additional 5 hours without acoustic monitoring during daylight hours only under the following conditions: • Sea state is less than or equal to BSS 4; • No marine mammals (excluding delphinids) detected solely by PAM in the applicable EZ in the previous 2 hours; • NMFS is notified via email as soon as practicable with the time and location in which operations began occurring without an active PAM system; and • Operations with an active acoustic source, but without an operating PAM system, do not exceed a cumulative total of 5 hours in any 24-hour period. Establishment of Exclusion and Pre-Start Clearance Zones An EZ is a defined area within which occurrence of a marine mammal triggers mitigation action intended to reduce the potential for certain outcomes, e.g., auditory injury, disruption of critical behaviors. The PSOs would establish a minimum EZ with a 500-m radius. The 500-m EZ would be based on radial distance from the edge of the airgun array (rather than being based on the center of the array or around the vessel itself). With certain exceptions (described below), if a marine mammal appears within or enters this zone, the acoustic source would be shut down. The pre-start clearance zone is defined as the area that must be clear of marine mammals prior to beginning ramp-up of the acoustic source, and includes the EZ plus the buffer zone. Detections of marine mammals within the pre-start clearance zone would prevent airgun operations from beginning ( i.e., ramp-up). The 500-m EZ is intended to be precautionary in the sense that it would be expected to contain sound exceeding the injury criteria for all cetacean hearing groups, (based on the dual criteria of SEL cum and peak SPL), while also providing a consistent, reasonably observable zone within which PSOs would typically be able to conduct effective observational effort. Additionally, a 500-m EZ is expected to minimize the likelihood that marine mammals will be exposed to levels likely to result in more severe behavioral responses. Although significantly greater distances may be observed from an elevated platform under good conditions, we believe that 500 m is likely regularly attainable for PSOs using the naked eye during typical conditions. The pre-start clearance zone simply represents the addition of a buffer to the EZ, doubling the EZ size during pre-clearance. An extended EZ of 1,500 m must be enforced for all beaked whales. No buffer of this extended EZ is required. Pre-Start Clearance and Ramp-Up Ramp-up (sometimes referred to as “soft start”) means the gradual and systematic increase of emitted sound levels from an airgun array. Ramp-up begins by first activating a single airgun of the smallest volume, followed by doubling the number of active elements in stages until the full complement of an array's airguns are active. Each stage should be approximately the same duration, and the total duration should not be less than approximately 20 minutes. The intent of pre-start clearance observation (30 minutes) is to ensure no protected species are observed within the pre-clearance zone (or extended EZ, for beaked whales) prior to the beginning of ramp-up. During pre-start clearance period is the only time observations of marine mammals in the buffer zone would prevent operations ( i.e., the beginning of ramp-up). The intent of ramp-up is to warn marine mammals of pending seismic operations and to allow sufficient time for those animals to leave the immediate vicinity. A ramp-up procedure, involving a step-wise increase in the number of airguns firing and total array volume until all operational airguns are activated and the full volume is achieved, is required at all times as part of the activation of the acoustic source. All operators must adhere to the following pre-start clearance and ramp-up requirements: • The operator must notify a designated PSO of the planned start of ramp-up as agreed upon with the lead PSO; the notification time should not be less than 60 minutes prior to the planned ramp-up in order to allow the PSOs time to monitor the pre-start clearance zone (and extended EZ) for 30 minutes prior to the initiation of ramp-up (pre-start clearance); • Ramp-ups shall be scheduled so as to minimize the time spent with the source activated prior to reaching the designated run-in; • One of the PSOs conducting pre-start clearance observations must be notified again immediately prior to initiating ramp-up procedures and the operator must receive confirmation from the PSO to proceed; • Ramp-up may not be initiated if any marine mammal is within the applicable exclusion or buffer zone. If a marine mammal is observed within the pre-start clearance zone (or extended EZ, for beaked whales) during the 30 minute pre-start clearance period, ramp-up may not begin until the animal(s) has been observed exiting the zones or until an additional time period has elapsed with no further sightings (15 minutes for small odontocetes and pinnipeds, and 30 minutes for all mysticetes and all other odontocetes, including sperm whales, beaked whales, and large delphinids, such as killer whales); • Ramp-up shall begin by activating a single airgun of the smallest volume in the array and shall continue in stages by doubling the number of active elements at the commencement of each stage, with each stage of approximately the same du [Text truncated at 120,000 characters. The full text is on the page linked above.] --- Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2021-11718. Public record. Not legal advice.