# Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Site Characterization Surveys of Lease Areas OCS-A 0486, OCS-A 0487, and OCS-A 0500 > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A2019-15802 ## Record - **Collection:** Federal Register - **Document type:** Notice - **Published:** July 26, 2019 - **Citation:** 84 FR 36054 ## Text DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration RIN 0648-XG909 Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Site Characterization Surveys of Lease Areas OCS-A 0486, OCS-A 0487, and OCS-A 0500 AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce. ACTION: Notice; proposed incidental harassment authorization; request for comments. SUMMARY: NMFS has received an application from Orsted Wind Power LLC (Orsted) for an Incidental Harassment Authorization (IHA) to take marine mammals, by harassment, incidental to high-resolution geophysical (HRG) survey investigations associated with marine site characterization activities off the coast of Massachusetts and Rhode Island in the areas of Commercial Lease of Submerged Lands for Renewable Energy Development on the Outer Continental Shelf (OCS) currently being leased by the Applicant's affiliates Deepwater Wind New England, LLC and Bay State Wind LLC, respectively. These are identified as OCS-A 0486, OCS-A 0487, and OCS-A 0500 (collectively referred to as the Lease Areas). Orsted is also proposing to conduct marine site characterization surveys along one or more export cable route corridors (ECRs) originating from the Lease Areas and landing along the shoreline at locations from New York to Massachusetts, between Raritan Bay (part of the New York Bight) to Falmouth, Massachusetts (see Figure 1). Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting comments on its proposal to issue an IHA to Orsted to incidentally take, by Level B harassment only, small numbers of marine mammals during the specified activities. 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 August 26, 2019. 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.Pauline@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. Attachments to electronic comments will be accepted in Microsoft Word or Excel or Adobe PDF file formats only. All comments received are a part of the public record and will generally be posted online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-other-energy-activities-renewable 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: Rob Pauline, 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: https://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 such 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 such takings are set forth. National Environmental Policy Act (NEPA) 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 incidental harassment authorization) with respect to potential impacts on the human environment. Accordingly, NMFS is preparing an Environmental Assessment (EA) to consider the environmental impacts associated with the issuance of the proposed IHA. NMFS' [EIS or EA] [was or will be] made available at https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act. 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 March 8, 2019, NMFS received an application from Orsted for the taking of marine mammals incidental to HRG and geotechnical survey investigations in the OCS-A 0486, OCS-A 0487, and OCS-A 0500 Lease Areas, designated and offered by the Bureau of Ocean Energy Management (BOEM) as well as along one or more ECRs between the southern portions of the Lease Areas and shoreline locations from New York to Massachusetts, to support the development of an offshore wind project. Orsted's request is for take, by Level B harassment, of small numbers of 15 species or stocks of marine mammals. The application was considered adequate and complete on May 23, 2019. Neither Orsted nor NMFS expects serious injury or mortality to result from this activity and, therefore, an IHA is appropriate. NMFS previously issued two IHAs to both Bay State Wind (81 FR 56589, August 22, 2016; 83 FR 36539, July 30, 2018) and Deepwater Wind (82 FR 32230, July 13, 2017; 83 FR 28808, June 21, 2018) for similar activities. Orsted has complied with all the requirements ( e.g., mitigation, monitoring, and reporting) of the issued IHAs. Description of the Specified Activity Overview Orsted proposes to conduct HRG surveys in the Lease Area and ECRs to support the characterization of the existing seabed and subsurface geological conditions. This information is necessary to support the final siting, design, and installation of offshore project facilities, turbines and subsea cables within the project area as well as to collect the data necessary to support the review requirements associated with Section 106 of the National Historic Preservation Act of 1966, as amended. Underwater sound resulting from Orsted's proposed site characterization surveys has the potential to result in incidental take of marine mammals. This take of marine mammals is anticipated to be in the form of harassment and no serious injury or mortality is anticipated, nor is any authorized in this IHA. Dates and Duration HRG surveys are anticipated to commence in August, 2019. Orsted is proposing to conduct continuous HRG survey operations 24-hours per day (Lease Area and ECR Corridors) using multiple vessels. Based on the planned 24-hour operations, the survey activities for all survey segments would require 666 vessel days total if one vessel were surveying the entire survey line continuously. However, an estimated 5 vessels may be used simultaneously with a maximum of no more than 9 vessels. Therefore, all of the survey will be completed within one year. See Table 1 for the estimated number of vessel days for each survey segment. This is considered the total number of vessel days required, regardless of the number of vessels used. While actual survey duration would shorten given the use of multiple vessels, total vessel days provides an equivalent estimate of exposure for a given area. The estimated durations to complete survey activities do not include weather downtime. Surveys are anticipated to commence upon issuance of the requested IHA, if appropriate. Table 1—Summary of Proposed HRG Survey Segments Survey segment Total line km per day Total duration (vessel days) * Lease Area OCS-A 0486 70 79 Lease Area OCS-A 0487 140 Lease Area OCS-A 0500 94 ECR Corridor(s) 353 Total 666 * Estimate is based on total time for one (1) vessel to complete survey activities. Specified Geographic Region Orsted's survey activities will occur in the Lease Areas designated and offered by BOEM, located approximately 14 miles (mi) south of Martha's Vineyard, Massachusetts at its closest point, as well as within potential export cable route corridors off the coast of New York, Connecticut, Rhode Island, and Massachusetts shown in Figure 1. Water depth in these areas for the majority of the survey area is 1-55 m. However south of Long Island in the area we are surveying for cable routes, the maximum depth reaches 77 m in some locations. Also there is a very small area in the area north of the eastern end of Long Island that reaches a depth of 123 m. BILLING CODE 3510-22-P EN26JY19.000 BILLING CODE 3510-22-C Detailed Description of Specified Activities Marine site characterization surveys will include the following HRG survey activities: • Depth sounding (multibeam depth sounder) to determine water depths and general bottom topography (currently estimated to range from approximately 3 to 180 feet (ft), 1 to 55 m, in depth below mean lower low water); • Magnetic intensity measurements for detecting local variations in regional magnetic field from geological strata and potential ferrous objects on and below the seabed; • Seafloor imaging (sidescan sonar survey) for seabed sediment classification purposes, to identify natural and man-made acoustic targets resting on the bottom as well as any anomalous features; • Sub-bottom profiler to map the near surface stratigraphy; and • Ultra High Resolution Seismic (UHRS) equipment to map deeper subsurface stratigraphy as needed. Table 2 identifies the representative survey equipment that is being considered in support of the HRG survey activities. The make and model of the HRG equipment will vary depending on availability. The primary operating frequency is oftentimes defined by the HRG equipment manufacturer or HRG contractor. The pulse duration provided represents best engineering estimates of the RMS 90 values based on anticipated operator and sound source verification (SSV) reports of similar equipment (see Appendix E in Application). Orsted SSV reports also provide relevant information on anticipated settings. For most HRG sources, the midrange frequency is typically deemed appropriate for hydroacoustic assessment purposes. The SSV reports have also reasonably assumed that the HRG equipment were being operated at configurations deemed appropriate for the Survey Area. None of the proposed HRG survey activities will result in the disturbance of bottom habitat in the Survey Area. Table 2—Summary of Proposed HRG Survey Data Acquisition Equipment Representative HRG survey equipment Range of operating frequencies (kHz) Baseline source level a Representative RMS 90 pulse duration (millisec) Pulse repetition rate (Hz) Primary operating frequency (kHz) USBL & Global Acoustic Positioning System (GAPS) Transceiver Sonardyne Ranger 2 transponder b 19-34 200 dB RMS 300 1 26 Sonardyne Ranger 2 USBL HPT 5/7000 transceiver b 19 to 34 200 dB RMS 300 1 26 Sonardyne Ranger 2 USBL HPT 3000 transceiver b 19 to 34 194 dB RMS 300 3 26.5 Sonardyne Scout Pro transponder b 35 to 50 188 dB RMS 300 1 42.5 Easytrak Nexus 2 USBL transceiver b 18 to 32 192 dB RMS 300 1 26 IxSea GAPS transponder b 20 to 32 188 dB RMS 20 10 26 Kongsberg HiPAP 501/502 USBL transceiver b 21 to 31 190 dB RMS 300 1 26 Edgetech BATS II transponder b 17 to30 204 dB RMS 300 3 23.5 Shallow Sub-Bottom Profiler (Chirp) Edgetech 3200 c 2 to 16 212 dB RMS 150 5 9 EdgeTech 216 b 2 to 16 174 dB RMS 22 2 6 EdgeTech 424 b 4 to 24 176 dB RMS 3.4 2 12 EdgeTech 512 b 0.5 to 12 177 dB RMS 2.2 2 3 Teledyne Benthos Chirp III—TTV 170 b 2 to 7 197 dB RMS 5 to 60 4 3.5 GeoPulse 5430 A Sub-bottom Profiler b e 1.5 to 18 214 dB RMS 25 10 4.5 PanGeo LF Chirp b 2 to 6.5 195 dB RMS 481.5 0.06 3 PanGeo HF Chirp b 4.5 to 12.5 190 dB RMS 481.5 0.06 5 Parametric Sub-Bottom Profiler Innomar SES-2000 Medium 100 c 85 to 115 247 dB RMS 0.07 to 2 40 85 Innomar SES-2000 Standard & Plus b 85 to 115 236 dB RMS 0.07 to 2 60 85 Innomar SES-2000 Medium 70 b 60 to 80 241 dB RMS 0.1 to 2.5 40 70 Innomar SES-2000 Quattro b 85 to 115 245 dB RMS 0.07 to 1 60 85 PanGeo 2i Parametric b 90-115 239 dB RMS 0.33 40 102 Medium Penetration Sub-Bottom Profiler (Sparker) GeoMarine Geo-Source 400tip d 0.2 to 5 212 dB Peak ; 201 dB RMS 55 2 2 GeoMarine Geo-Source 600tip d 0.2 to 5 214 dB Peak ; 205 dB RMS 55 2 2 GeoMarine Geo-Source 800tip d 0.2 to 5 215 dB Peak ; 206 dB RMS 55 2 2 Applied Acoustics Dura-Spark 400 System d 0.3 to 1.2 225 dB Peak ; 214 dB RMS 55 0.4 1 GeoResources Sparker 800 System d 0.05 to 5 215 dB Peak ; 206 dB RMS 55 2.5 1.9 Medium Penetration Sub-Bottom Profiler (Boomer) Applied Acoustics S-Boom 1000J b 0.250 to 8 228 dB Peak ; 208 dB RMS 0.6 3 0.6 Applied Acoustics S-Boom 700J b 0.1 to 5 211 dB Peak ; 205 dB RMS 5 3 0.6 Notes: a Baseline source levels were derived from manufacturer-reported source levels (SL) when available either in the manufacturer specification sheet or from the SSV report. When manufacturer specifications were unavailable or unclear, Crocker and Fratantonio (2016) SLs were utilized as the baseline: b source level obtained from manufacturer specifications; c source level obtained from SSV-reported manufacturer SL; d source level obtained from Crocker and Fratantonio (2016); e unclear from manufacturer specifications and SSV whether SL is reported in peak or rms; however, based on SLpk source level reported in SSV, assumption is SLrms is reported in specifications. The transmit frequencies of sidescan and multibeam sonars for the 2019 marine site characterization surveys operate outside of marine mammal functional hearing frequency range. The deployment of HRG survey equipment, including the use of intermittent, impulsive sound-producing equipment operating below 200 kilohertz (kHz), has the potential to cause acoustic harassment to marine mammals. Based on the frequency ranges of the equipment to be used in support of the HRG survey activities (Table 2) and the hearing ranges of the marine mammals that have the potential to occur in the Survey Area during survey activities (Table 3), the noise produced by the ultrashort baseline (USBL) and global acoustic positioning system (GAPS) transceiver systems; sub-bottom profilers (parametric and chirp); sparkers; and boomers fall within the established marine mammal hearing ranges and have the potential to result in harassment of marine mammals. All HRG equipment proposed for use is shown in Table 2. Assuming a maximum survey track line to fully cover the Survey Area, the survey activities will be supported by vessels sufficient in size to accomplish the survey goals in specific survey areas and capable of maintaining both the required course and a survey speed to cover approximately 70.0 kilometers (km) per day at a speed of 4 knots (7.4 km per hour) while acquiring survey lines. While survey tracks could shorten, the maximum survey track scenario has been selected to provide operational flexibility and to cover the possibility of multiple landfall locations and associated cable routes. Survey segments represent a maximum extent, and distances may vary depending on contractor used. Orsted has proposed to reduce the total duration of survey activities and minimize cost by conducting continuous HRG survey operations 24-hours per day for all survey segments. Total survey effort has been conservatively estimated to require up to a full year to provide survey flexibility on specific locations and vessel numbers to be utilized (likely between 5-9), which will be determined at the time of contractor selection. Orsted also proposes to complete the proposed survey quickly and efficiently by using multiple vessels of varying size depending on survey segment location. To reduce the total survey duration, simultaneous survey activities will occur across multiple vessels in respective survey segments, where appropriate. Additionally, Orsted may elect to use an autonomous surface vehicle (ASV) to support survey operations. Use of an ASV in combination with a mother vessel allows the project team to double the survey daily production. The ASV will capture data in water depths shallower than 26 ft (8 m), increasing the shallow end reach of the larger vessel. The ASV can be used for nearshore operations and shallow work (20 ft (6 m) and less) in a “manned” configuration. The ASV and mother vessel will acquire survey data in tandem and the ASV will be kept within sight of the mother vessel at all times. The ASV will operate autonomously along a parallel track to, and slightly ahead of, the mother vessel at a distance set to prevent crossed signaling of survey equipment (within 2,625 ft (800 m)) During data acquisition surveyors have full control of the data being acquired and have the ability to make changes to settings such as power, gain, range scale etc. in real time. 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 the Specified Activity 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 (SAR; https://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 ( https://www.fisheries.noaa.gov/find-species ). We expect that the species listed in Table 3 will potentially occur in the project area and will potentially be taken as a result of the proposed project. Table 3 summarizes information related to the population or stock, including regulatory status under the MMPA and ESA and potential biological removal (PBR), where known. For taxonomy, we follow Committee on Taxonomy (2018). 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' SARs). While no mortality is anticipated or authorized here, PBR is included here as a gross indicator 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 comprise 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. Atlantic Ocean SARs ( e.g., Hayes et al., 2018). All values presented in Table 3 are the most recent available at the time of publication and are available in the 2017 SARs (Hayes et al., 2018) and draft 2018 SARs (available online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/draft-marine-mammal-stock-assessment-reports ). Table 3—Marine Mammal Known to Occur in Survey Area Waters Common name Scientific name Stock ESA/MMPA status; strategic (Y/N) 1 Stock abundance (CV, N min , most recent abundance survey) 2 PBR Annual M/SI 3 Order Cetartiodactyla—Cetacea—Superfamily Mysticeti (baleen whales) Family Balaenidae: North Atlantic Right whale Eubalaena glacialis Western North Atlantic (WNA) E/D; Y 451 (0; 445; 2017) 0.9 5.56 Family Balaenopteridae (rorquals): Humpback whale Megaptera novaeangliae Gulf of Maine -/-; N 896 (0; 896; 2012) 14.6 9.7 Fin whale Balaenoptera physalus WNA E/D; Y 1,618 (0.33; 1,234; 2011) 2.5 2.5 Sei whale Balaenoptera borealis Nova Scotia E/D; Y 357 (0.52; 236) 0.5 0.8 Minke whale Balaenoptera acutorostrata Canadian East Coast -/-; N 2,591 (0.81; 1,425) 14 7.7 Superfamily Odontoceti (toothed whales, dolphins, and porpoises) Family Physeteridae: Sperm whale Physeter macrocephalus E; Y 2,288 (0.28; 1,815) North Atlantic 3.6 0.8 Family Delphinidae: Long-finned pilot whale Globicephala melas WNA -/-; Y 5,636 (0.63; 3,464) 35 38 Bottlenose dolphin Tursiops spp. WNA Offshore -/-; N 77,532 (0.40; 56053; 2016) 561 39.4 Short beaked common dolphin Delphinus delphis WNA -/-; N 70,184 (0.28; 55,690; 2011) 557 406 Atlantic white-sided dolphin Lagenorhynchus acutus WNA -/-; N 48,819 (0.61; 30,403; 2011) 304 30 Atlantic spotted dolphin Stenella frontalis WNA -/-: N 44,715 (0.43; 31,610; 2013) 316 0 Risso's dolphin Grampus griseus WNA -/-; N 18,250 (0.5; 12,619; 2011) 126 49.7 Family Phocoenidae (porpoises): Harbor porpoise Phocoena phocoena Gulf of Maine/Bay of Fundy -/-; N 79,833 (0.32; 61,415; 2011) 706 256 Order Carnivora—Superfamily Pinnipedia Family Phocidae (earless seals): Gray seal Halichoerus grypus -; N 27,131 (0.19; 23,158) W. North Atlantic 1,389 5,688 Harbor seal Phoca vitulina -; N 75,834 (0.15; 66,884) W. North Atlantic 345 333 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 online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports-region/. CV is coefficient of variation; Nmin is the minimum estimate of stock abundance. In some cases, CV is not applicable. 3 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, ship strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range. As described below, 15 species (with 15 managed stocks) temporally and spatially co-occur with the activity to the degree that take is reasonably likely to occur, and we have proposed authorizing it. The following subsections provide additional information on the biology, habitat use, abundance, distribution, and the existing threats to the non-ESA-listed and ESA-listed marine mammals that are both common in the waters of the outer continental shelf (OCS) of Southern New England and have the likelihood of occurring, at least seasonally, in the Survey Area. These species include the North Atlantic right, humpback, fin, sei, minke, sperm, and long finned pilot whale, bottlenose, short-beaked common, Atlantic white-sided, Atlantic spotted, and Risso's dolphins, harbor porpoise, and gray and harbor seals (BOEM 2014). Although the potential for interactions with long-finned pilot whales and Atlantic spotted and Risso's dolphins is minimal, small numbers of these species may transit the Survey Area and are included in this analysis. Cetaceans North Atlantic Right Whale The North Atlantic right whale ranges from the calving grounds in the southeastern United States to feeding grounds in New England waters and into Canadian waters (Waring et al., 2017). Right whales have been observed in or near southern New England during all four seasons; however, they are most common in the spring when they are migrating north and in the fall during their southbound migration (Kenney and Vigness-Raposa 2009). Surveys have demonstrated the existence of seven areas where North Atlantic right whales congregate seasonally, including north and east of the proposed survey area in Georges Bank, off Cape Cod, and in Massachusetts Bay (Waring et al., 2017). In addition modest late winter use of a region south of Martha's Vineyard and Nantucket Islands was recently described (Stone et al. 2017). A large increase in aerial surveys of the Gulf of St. Lawrence documented at least 36 and 117 unique individuals using the region, respectively, during the summers of 2015 and 2017 (NMFS unpublished data). In the late fall months ( e.g. October), right whales are generally thought to depart from the feeding grounds in the North Atlantic and move south to their calving grounds off Florida. However, recent research indicates our understanding of their movement patterns remains incomplete (Davis et al. 2017). A review of passive acoustic monitoring data from 2004 to 2014 throughout the western North Atlantic Ocean demonstrated nearly continuous year-round right whale presence across their entire habitat range, including in locations previously thought of as migratory corridors, suggesting that not all of the population undergoes a consistent annual migration (Davis et al. 2017). The number of North Atlantic right whale vocalizations detected in the proposed survey area were relatively constant throughout the year, with the exception of August through October when detected vocalizations showed an apparent decline (Davis et al. 2017). North Atlantic right whales are expected to be present in the proposed survey area during the proposed survey, especially during the summer months, with numbers possibly lower in the fall. The proposed survey area is part of a migratory Biologically Important Area (BIA) for North Atlantic right whales; this important migratory area is comprised of the waters of the continental shelf offshore the East Coast of the United States and extends from Florida through Massachusetts. A map showing designated BIAs is available at: https://cetsound.noaa.gov/biologically-important-area-map. NMFS' regulations at 50 CFR part 224.105 designated nearshore waters of the Mid-Atlantic Bight as Mid-Atlantic U.S. Seasonal Management Areas (SMA) for right whales in 2008. SMAs were developed to reduce the threat of collisions between ships and right whales around their migratory route and calving grounds. A portion of one SMA, overlaps spatially with a section of the proposed survey area. The SMA is active from November 1 through April 30 of each year. The western North Atlantic population demonstrated overall growth of 2.8 percent per year between 1990 to 2010, despite a decline in 1993, and no growth between 1997 and 2000 (Pace et al. 2017). However, since 2010 the population has been in decline, with a 99.99 percent probability of a decline of just under 1 percent per year (Pace et al. 2017). Between 1990 and 2015, calving rates varied substantially, with low calving rates coinciding with all three periods of decline or no growth (Pace et al. 2017). In 2018, no new North Atlantic right whale calves were documented in their calving grounds; this represented the first time since annual NOAA aerial surveys began in 1989 that no new right whale calves were observed. However, in 2019 at least seven right whale calves have been identified (Savio 2019). Data indicates that the number of adult females fell from 200 in 2010 to 186 in 2015 while males fell from 283 to 272 in the same time frame (Pace et al., 2017). In addition, elevated North Atlantic right whale mortalities have occurred since June 7, 2017. A total of 26 confirmed dead stranded whales (18 in Canada; 8 in the United States), have been documented to date. This event has been declared an Unusual Mortality Event (UME), with human interactions ( i.e., fishery-related entanglements and vessel strikes) identified as the most likely cause. More information is available online at: https://www.fisheries.noaa.gov/national/marine-life-distress/2017-2018-north-atlantic-right-whale-unusual-mortality-event. Humpback Whale Humpback whales are found worldwide in all oceans. Humpback whales were listed as endangered under the Endangered Species Conservation Act (ESCA) in June 1970. In 1973, the ESA replaced the ESCA, and humpbacks continued to be listed as endangered. NMFS recently evaluated the status of the species, and on September 8, 2016, NMFS divided the species into 14 distinct population segments (DPS), removed the current species-level listing, and in its place listed four DPSs as endangered and one DPS as threatened (81 FR 62259; September 8, 2016). The remaining nine DPSs were not listed. The West Indies DPS, which is not listed under the ESA, is the only DPS of humpback whale that is expected to occur in the survey area. The best estimate of population abundance for the West Indies DPS is 12,312 individuals, as described in the NMFS Status Review of the Humpback Whale under the Endangered Species Act (Bettridge et al., 2015). In New England waters, feeding is the principal activity of humpback whales, and their distribution in this region has been largely correlated to abundance of prey species, although behavior and bathymetry are factors influencing foraging strategy (Payne et al. 1986, 1990). Humpback whales are frequently piscivorous when in New England waters, feeding on herring ( Clupea harengus ), sand lance ( Ammodytes spp.), and other small fishes, as well as euphausiids in the northern Gulf of Maine (Paquet et al. 1997). During winter, the majority of humpback whales from North Atlantic feeding areas (including the Gulf of Maine) mate and calve in the West Indies, where spatial and genetic mixing among feeding groups occurs, though significant numbers of animals are found in mid- and high-latitude regions at this time and some individuals have been sighted repeatedly within the same winter season, indicating that not all humpback whales migrate south every winter (Waring et al., 2017). Other sightings of note include 46 sightings of humpbacks in the New York- New Jersey Harbor Estuary documented between 2011 and 2016 (Brown et al. 2017). Multiple humpbacks were observed feeding off Long Island during July of 2016 ( https://www.greateratlantic.fisheries.noaa.gov/mediacenter/2016/july/26_humpback_whales_visit_new_york.html, accessed 31 December, 2018) and there were sightings during November-December 2016 near New York City ( https://www.greateratlantic.fisheries.noaa.gov/mediacenter/2016/december/09_humans_and_humpbacks_of_new_york_2.html, accessed 31 December 2018). Since January 2016, elevated humpback whale mortalities have occurred along the Atlantic coast from Maine through Florida. The event has been declared a UME. Partial or full necropsy examinations have been conducted on approximately half of the 93 known cases. A portion of the whales have shown evidence of pre-mortem vessel strike; however, this finding is not consistent across all of the whales examined so more research is needed. NOAA is consulting with researchers that are conducting studies on the humpback whale populations, and these efforts may provide information on changes in whale distribution and habitat use that could provide additional insight into how these vessel interactions occurred. More detailed information is available at : https://www.fisheries.noaa.gov/national/marine-life-distress/2016-2018-humpback-whale-unusual-mortality-event-along-atlantic-coast#causes-of-the-humpback-whale-ume (accessed June 3, 2019). Three previous UMEs involving humpback whales have occurred since 2000, in 2003, 2005, and 2006. Fin Whale Fin whales are common in waters of the U. S. Atlantic Exclusive Economic Zone (EEZ), principally from Cape Hatteras northward (Waring et al., 2017). Fin whales are present north of 35-degree latitude in every season and are broadly distributed throughout the western North Atlantic for most of the year, though densities vary seasonally (Waring et al., 2017). The main threats to fin whales are fishery interactions and vessel collisions (Waring et al., 2017). New England waters represent a major feeding ground for fin whales. The proposed survey area would overlap spatially and temporally with a feeding BIA for fin whales. The important fin whale feeding area occurs from March through October and stretches from an area south of Montauk Point to south of Martha's Vineyard. Sei Whale The Nova Scotia stock of sei whales can be found in deeper waters of the continental shelf edge waters of the northeastern United States and northeastward to south of Newfoundland. NOAA Fisheries considers sei whales occurring from the U.S. East Coast to Cape Breton, Nova Scotia, and east to 42° W as the Nova Scotia stock of sei whales (Waring et al. 2016; Hayes et al. 2018). In the Northwest Atlantic, it is speculated that the whales migrate from south of Cape Cod along the eastern Canadian coast in June and July, and return on a southward migration again in September and October (Waring et al. 2014; 2017). Spring is the period of greatest abundance in U.S. waters, with sightings concentrated along the eastern margin of Georges Bank and into the Northeast Channel area, and along the southwestern edge of Georges Bank in the area of Hydrographer Canyon (Waring et al., 2015). Minke Whale Minke whales can be found in temperate, tropical, and high-latitude waters. The Canadian East Coast stock can be found in the area from the western half of the Davis Strait (45° W) to the Gulf of Mexico (Waring et al., 2017). This species generally occupies waters less than 100 m deep on the continental shelf. There appears to be a strong seasonal component to minke whale distribution in which spring to fall are times of relatively widespread and common occurrence, and when the whales are most abundant in New England waters, while during winter the species appears to be largely absent (Waring et al., 2017). Since January 2017, elevated minke whale strandings have occurred along the Atlantic coast from Maine through South Carolina, with highest numbers in Massachusetts, Maine, and New York. Partial or full necropsy examinations have been conducted on more than 60 percent of the 59 known cases. Preliminary findings in several of the whales have shown evidence of human interactions or infectious disease. These findings are not consistent across all of the whales examined, so more research is needed. As part of the UME investigation process, NOAA is assembling an independent team of scientists to coordinate with the Working Group on Marine Mammal Unusual Mortality Events to review the data collected, sample stranded whales, and determine the next steps for the investigation. More information is available at: www.fisheries.noaa.gov/national/marine-life-distress/2017-2018-minke-whale-unusual-mortality-event-along-atlantic-coast (accessed June 3, 2019). Sperm Whale The distribution of the sperm whale in the U.S. EEZ occurs on the continental shelf edge, over the continental slope, and into mid-ocean regions (Waring et al. 2014). The basic social unit of the sperm whale appears to be the mixed school of adult females plus their calves and some juveniles of both sexes, normally numbering 20-40 animals in all. Sperm whales are somewhat migratory; however, their migrations are not as specific as seen in most of the baleen whale species. In the North Atlantic, there appears to be a general shift northward during the summer, but there is no clear migration in some temperate areas (Rice 1989). In summer, the distribution of sperm whales includes the area east and north of Georges Bank and into the Northeast Channel region, as well as the continental shelf (inshore of the 100-m isobath) south of New England. In the fall, sperm whale occurrence south of New England on the continental shelf is at its highest level, and there remains a continental shelf edge occurrence in the mid-Atlantic bight. In winter, sperm whales are concentrated east and northeast of Cape Hatteras. Their distribution is typically associated with waters over the continental shelf break and the continental slope and into deeper waters (Whitehead et al. 1991). Sperm whale concentrations near drop-offs and areas with strong currents and steep topography are correlated with high productivity. These whales occur almost exclusively found at the shelf break, regardless of season. Long-Finned Pilot Whale Long-finned pilot whales are found from North Carolina and north to Iceland, Greenland and the Barents Sea (Waring et al., 2016). They are generally found along the edge of the continental shelf (a depth of 330 to 3,300 feet (100 to 1,000 meters)), choosing areas of high relief or submerged banks in cold or temperate shoreline waters. In the western North Atlantic, long-finned pilot whales are pelagic, occurring in especially high densities in winter and spring over the continental slope, then moving inshore and onto the shelf in summer and autumn following squid and mackerel populations (Reeves et al. 2002). They frequently travel into the central and northern Georges Bank, Great South Channel, and Gulf of Maine areas during the late spring and remain through early fall (May and October) (Payne and Heinemann 1993). Atlantic White-Sided Dolphin White-sided dolphins are found in temperate and sub-polar waters of the North Atlantic, primarily in continental shelf waters to the 100-m depth contour from central West Greenland to North Carolina (Waring et al., 2017). The Gulf of Maine stock is most common in continental shelf waters from Hudson Canyon to Georges Bank, and in the Gulf of Maine and lower Bay of Fundy. Sighting data indicate seasonal shifts in distribution (Northridge et al., 1997). During January to May, low numbers of white-sided dolphins are found from Georges Bank to Jeffreys Ledge (off New Hampshire), with even lower numbers south of Georges Bank, as documented by a few strandings collected on beaches of Virginia to South Carolina. From June through September, large numbers of white-sided dolphins are found from Georges Bank to the lower Bay of Fundy. From October to December, white-sided dolphins occur at intermediate densities from southern Georges Bank to southern Gulf of Maine (Payne and Heinemann 1990). Sightings south of Georges Bank, particularly around Hudson Canyon, occur year round but at low densities. Atlantic Spotted Dolphin Atlantic spotted dolphins are found in tropical and warm temperate waters ranging from southern New England, south to Gulf of Mexico and the Caribbean to Venezuela (Waring et al., 2014). This stock regularly occurs in continental shelf waters south of Cape Hatteras and in continental shelf edge and continental slope waters north of this region (Waring et al., 2014). There are two forms of this species, with the larger ecotype inhabiting the continental shelf and is usually found inside or near the 200 m isobaths (Waring et al., 2014). The smaller ecotype has less spots and occurs in the Atlantic Ocean, but is not known to occur in the Gulf of Mexico. Atlantic spotted dolphins are not listed under the ESA and the stock is not considered depleted or strategic under the MMPA. Common Dolphin The short-beaked common dolphin is found world-wide in temperate to subtropical seas. In the North Atlantic, short-beaked common dolphins are commonly found over the continental shelf between the 100-m and 2,000-m isobaths and over prominent underwater topography and east to the mid-Atlantic Ridge (Waring et al., 2016). This species is found between Cape Hatteras and Georges Bank from mid-January to May, although they migrate onto the northeast edge of Georges Bank in the fall where large aggregations occur (Kenney and Vigness-Raposa 2009), where large aggregations occur on Georges Bank in fall (Waring et al. 2007). Only the western North Atlantic stock may be present in the Survey Area. Bottlenose Dolphin There are two distinct bottlenose dolphin ecotypes in the western North Atlantic: The coastal and offshore forms (Waring et al., 2015). The migratory coastal morphotype resides in waters typically less than 65.6 ft (20 m) deep, along the inner continental shelf (within 7.5 km (4.6 miles) of shore), around islands, and is continuously distributed south of Long Island, New York into the Gulf of Mexico. This migratory coastal population is subdivided into 7 stocks based largely upon spatial distribution (Waring et al. 2015). Of these 7 coastal stocks, the Western North Atlantic migratory coastal stock is common in the coastal continental shelf waters off the coast of New Jersey (Waring et al. 2017). Generally, the offshore migratory morphotype is found exclusively seaward of 34 km (21 miles) and in waters deeper than 34 m (111.5 feet). This morphotype is most expected in waters north of Long Island, New York (Waring et al. 2017; Hayes et al. 2017; 2018). The offshore form is distributed primarily along the outer continental shelf and continental slope in the Northwest Atlantic Ocean from Georges Bank to the Florida Keys and is the only type that may be present in the survey area as the survey area is north of the northern extent of the range of the Western North Atlantic Northern Migratory Coastal Stock. Risso's Dolphins Risso's dolphins are distributed worldwide in tropical and temperate seas (Jefferson et al. 2008, 2014), and in the Northwest Atlantic occur from Florida to eastern Newfoundland (Leatherwood et al. 1976; Baird and Stacey 1991). Off the northeastern U.S. coast, Risso's dolphins are distributed along the continental shelf edge from Cape Hatteras northward to Georges Bank during spring, summer, and autumn (CETAP 1982; Payne et al. 1984) (Figure 1). In winter, the range is in the mid-Atlantic Bight and extends outward into oceanic waters (Payne et al. 1984). Harbor Porpoise In the Survey Area, only the Gulf of Maine/Bay of Fundy stock may be present. This stock is found in U.S. and Canadian Atlantic waters and is concentrated in the northern Gulf of Maine and southern Bay of Fundy region, generally in waters less than 150 m deep (Waring et al., 2017). During fall (October-December) and spring (April-June) harbor porpoises are widely dispersed from New Jersey to Maine. During winter (January to March), intermediate densities of harbor porpoises can be found in waters off New Jersey to North Carolina, and lower densities are found in waters off New York to New Brunswick, Canada They are seen from the coastline to deep waters (>1800 m; Westgate et al. 1998), although the majority of the population is found over the continental shelf (Waring et al., 2017). Harbor Seal Harbor seals are year-round inhabitants of the coastal waters of eastern Canada and Maine (Katona et al. 1993), and occur seasonally along the coasts from southern New England to New Jersey from September through late May. While harbor seals occur year-round north of Cape Cod, they only occur during winter migration, typically September through May, south of Cape Cod (Southern New England to New Jersey) (Waring et al. 2015; Kenney and Vigness-Raposa 2009). Gray Seal There are three major populations of gray seals found in the world; eastern Canada (western North Atlantic stock), northwestern Europe and the Baltic Sea. Gray seals in the survey area belong to the western North Atlantic stock. The range for this stock is thought to be from New Jersey to Labrador. Current population trends show that gray seal abundance is likely increasing in the U.S. Atlantic EEZ (Waring et al., 2017). Although the rate of increase is unknown, surveys conducted since their arrival in the 1980s indicate a steady increase in abundance in both Maine and Massachusetts (Waring et al., 2017). It is believed that recolonization by Canadian gray seals is the source of the U.S. population (Waring et al., 2017). Since July 2018, elevated numbers of harbor seal and gray seal mortalities have occurred across Maine, New Hampshire and Massachusetts. This event has been declared a UME. Additionally, seals showing clinical signs of stranding have occurred as far south as Virginia, although not in elevated numbers. Therefore the UME investigation now encompasses all seal strandings from Maine to Virginia. Between July 1, 2018 and June 26, 2019, a total of 2,593 seal strandings have been recorded as part of this designated Northeast Pinniped UME. Based on tests conducted so far, the main pathogen found in the seals is phocine distemper virus. Additional testing to identify other factors that may be involved in this UME are underway. 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 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. The functional groups and the associated frequencies are indicated below (note that these frequency ranges correspond to the range for the composite group, with the entire range not necessarily reflecting the capabilities of every species within that group): • Low-frequency cetaceans (mysticetes): Generalized hearing is estimated to occur between approximately 7 Hertz (Hz) and 35 kHz; • Mid-frequency cetaceans (larger toothed whales, beaked whales, and most delphinids): Generalized hearing is estimated to occur between approximately 150 Hz and 160 kHz; • High-frequency cetaceans (porpoises, river dolphins, and members of the genera Kogia and Cephalorhynchus; including two members of the genus Lagenorhynchus, on the basis of recent echolocation data and genetic data): Generalized hearing is estimated to occur between approximately 275 Hz and 160 kHz. • Pinnipeds in water; Phocidae (true seals): Generalized hearing is estimated to occur between approximately 50 Hz to 86 kHz; • Pinnipeds in water; Otariidae (eared seals): Generalized hearing is estimated to occur between 60 Hz and 39 kHz. 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. Fifteen marine mammal species (thirteen cetacean and two pinniped (both phocid) species) have the reasonable potential to co-occur with the proposed survey activities. Please refer to Table 2. Of the cetacean species that may be present, five are classified as low-frequency cetaceans ( i.e., all mysticete species), seven are classified as mid-frequency cetaceans ( i.e., all delphinid species and the sperm whale), and one is classified as high-frequency cetacean ( i.e., harbor porpoise). Potential Effects of the Specified Activity on Marine Mammals and Their Habitat This section includes a summary and discussion of the ways that components of the specified activity may impact marine mammals and their habitat. The Estimated Take by Incidental Harassment section later in this document includes a quantitative analysis of the number of individuals that are expected to be taken by this activity. The Negligible Impact Analysis and Determination section considers the content of this section, the Estimated Take by Incidental Harassment 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 Sound Sound is a physical phenomenon consisting of minute vibrations that travel through a medium, such as air or water, and is generally characterized by several variables. Frequency describes the sound's pitch and is measured in Hz or kHz, while sound level describes the sound's intensity and is measured in dB. Sound level increases or decreases exponentially with each dB of change. The logarithmic nature of the scale means that each 10-dB increase is a 10-fold increase in acoustic power (and a 20-dB increase is then a 100-fold increase in power). A 10-fold increase in acoustic power does not mean that the sound is perceived as being 10 times louder, however. Sound levels are compared to a reference sound pressure (micro-Pascal) to identify the medium. For air and water, these reference pressures are “re: 20 micro pascals (µPa)” and “re: 1 µPa,” respectively. Root mean square (RMS) is the quadratic mean sound pressure over the duration of an impulse. RMS is calculated by squaring all of the sound amplitudes, averaging the squares, and then taking the square root of the average (Urick, 1975). RMS 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. 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 rather than by peak pressures. Acoustic Impacts HRG survey equipment use during the geophysical surveys may temporarily impact marine mammals in the area due to elevated in-water sound levels. Marine mammals are continually exposed to many sources of sound. Naturally occurring sounds such as lightning, rain, sub-sea earthquakes, and biological sounds ( e.g., snapping shrimp, whale songs) are widespread throughout the world's oceans. Marine mammals produce sounds in various contexts and use sound for various biological functions including, but not limited to: (1) Social interactions; (2) foraging; (3) orientation; and (4) predator detection. Interference with producing or receiving these sounds may result in adverse impacts. Audible distance, or received levels of sound depend on the nature of the sound source, ambient noise conditions, and the sensitivity of the receptor to the sound (Richardson et al., 1995). Type and significance of marine mammal reactions to sound are likely dependent on a variety of factors including, but not limited to, (1) the behavioral state of the animal ( e.g., feeding, traveling, etc.); (2) frequency of the sound; (3) distance between the animal and the source; and (4) the level of the sound relative to ambient conditions (Southall et al., 2007). When sound travels (propagates) from its source, its loudness decreases as the distance traveled by the sound increases. Thus, the loudness of a sound at its source is higher than the loudness of that same sound a kilometer away. Acousticians often refer to the loudness of a sound at its source (typically referenced to one meter from the source) as the source level and the loudness of sound elsewhere as the received level ( i.e., typically the receiver). For example, a humpback whale 3 km from a device that has a source level of 230 dB may only be exposed to sound that is 160 dB loud, depending on how the sound travels through water ( e.g., spherical spreading (6 dB reduction with doubling of distance) was used in this example). As a result, it is important to understand the difference between source levels and received levels when discussing the loudness of sound in the ocean or its impacts on the marine environment. As sound travels from a source, its propagation in water is influenced by various physical characteristics, including water temperature, depth, salinity, and surface and bottom properties that cause refraction, reflection, absorption, and scattering of sound waves. Oceans are not homogeneous and the contribution of each of these individual factors is extremely complex and interrelated. The physical characteristics that determine the sound's speed through the water will change with depth, season, geographic location, and with time of day (as a result, in actual active sonar operations, crews will measure oceanic conditions, such as sea water temperature and depth, to calibrate models that determine the path the sonar signal will take as it travels through the ocean and how strong the sound signal will be at a given range along a particular transmission path). As sound travels through the ocean, the intensity associated with the wavefront diminishes, or attenuates. This decrease in intensity is referred to as propagation loss, also commonly called transmission loss. Hearing Impairment Marine mammals may experience temporary or permanent hearing impairment when exposed to loud sounds. Hearing impairment is classified by temporary threshold shift (TTS) and permanent threshold shift (PTS). There are no empirical data for onset of PTS in any marine mammal; therefore, PTS-onset must be estimated from TTS-onset measurements and from the rate of TTS growth with increasing exposure levels above the level eliciting TTS-onset. PTS is considered auditory injury (Southall et al., 2007) and occurs in a specific frequency range and amount. Irreparable damage to the inner or outer cochlear hair cells may cause PTS; however, other mechanisms are also involved, such as exceeding the elastic limits of certain tissues and membranes in the middle and inner ears and resultant changes in the chemical composition of the inner ear fluids (Southall et al., 2007). Given the higher level of sound, longer durations of exposure necessary to cause PTS as compared with TTS, and the small zone within which sound levels would exceed criteria for onset of PTS, it is unlikely that PTS would occur during the proposed HRG surveys. Temporary Threshold Shift TTS is the mildest form of hearing impairment that can occur during exposure to a loud sound (Kryter, 1985). While experiencing TTS, the hearing threshold rises and a sound must be stronger in order to be heard. At least in terrestrial mammals, TTS can last from minutes or hours to (in cases of strong TTS) days, can be limited to a particular frequency range, and can occur to varying degrees ( i.e., a loss of a certain number of dBs of sensitivity). For sound exposures at or somewhat above the TTS threshold, hearing sensitivity in both terrestrial and marine mammals recovers rapidly after exposure to the noise ends. Marine mammal hearing plays a critical role in communication with conspecifics and in interpretation of environmental cues for purposes such as predator avoidance and prey capture. Depending on the degree (elevation of threshold in dB), duration ( i.e., recovery time), and frequency range of TTS and the context in which it is experienced, TTS can have effects on marine mammals ranging from discountable to serious. For example, a marine mammal may be able to readily compensate for a brief, relatively small amount of TTS in a non-critical frequency range that takes place during a time when the animals is traveling through the open ocean, where ambient noise is lower and there are not as many competing sounds present. Alternatively, a larger amount and longer duration of TTS sustained during a time when communication is critical for successful mother/calf interactions could have more serious impacts if it were in the same frequency band as the necessary vocalizations and of a severity that it impeded communication. The fact that animals exposed to levels and durations of sound that would be expected to result in this physiological response would also be expected to have behavioral responses of a comparatively more severe or sustained nature is also notable and potentially of more importance than the simple existence of a TTS. Currently, TTS data only exist for four species of cetaceans (bottlenose dolphin, beluga whale, harbor porpoise, and Yangtze finless porpoise) and three species of pinnipeds (northern elephant seal, harbor seal, and California sea lion) exposed to a limited number of sound sources ( i.e., mostly tones and octave-band noise) in laboratory settings ( e.g., Finneran et al., 2002 and 2010; Nachtigall et al., 2004; Kastak et al., 2005; Lucke et al., 2009; Mooney et al., 2009; Popov et al., 2011; Finneran and Schlundt, 2010). In general, harbor seals (Kastak et al., 2005; Kastelein et al., 2012a) and harbor porpoises (Lucke et al., 2009; Kastelein et al., 2012b) have a lower TTS onset than other measured pinniped or cetacean species. However, even for these animals, which are better able to hear higher frequencies and may be more sensitive to higher frequencies, exposures on the order of approximately 170 dB RMS or higher for brief transient signals are likely required for even temporary (recoverable) changes in hearing sensitivity that would likely not be categorized as physiologically damaging (Lucke et al., 2009). Additionally, the existing marine mammal TTS data come from a limited number of individuals within these species. There are no data available on noise-induced hearing loss for mysticetes (of note, the source operating characteristics of some of Orsted's proposed HRG survey equipment— i.e., the equipment positioning systems—are unlikely to be audible to mysticetes). For summaries of data on TTS in marine mammals or for further discussion of TTS onset thresholds, please see NMFS (2018), Southall et al. (2007), Finneran and Jenkins (2012), and Finneran (2015). Scientific literature highlights the inherent complexity of predicting TTS onset in marine mammals, as well as the importance of considering exposure duration when assessing potential impacts (Mooney et al., 2009a, 2009b; Kastak et al., 2007). Generally, with sound exposures of equal energy, quieter sounds (lower sound pressure level (SPL)) of longer duration were found to induce TTS onset more than louder sounds (higher SPL) of shorter duration (more similar to sub-bottom profilers). For intermittent sounds, less threshold shift will occur than from a continuous exposure with the same energy (some recovery will occur between intermittent exposures) (Kryter et al., 1966; Ward, 1997). For sound exposures at or somewhat above the TTS-onset threshold, hearing sensitivity recovers rapidly after exposure to the sound ends; intermittent exposures recover faster in comparison with continuous exposures of the same duration (Finneran et al., 2010). NMFS considers TTS as Level B harassment that is mediated by physiological effects on the auditory system. Marine mammals in the Survey Area during the HRG survey are unlikely to incur TTS hearing impairment due to the characteristics of the sound sources, which include low source levels (208 to 221 dB re 1 µPa-m) and generally very short pulses and duration of the sound. Even for high-frequency cetacean species ( e.g., harbor porpoises), which may have increased sensitivity to TTS (Lucke et al., 2009; Kastelein et al., 2012b), individuals would have to make a very close approach and also remain very close to vessels operating these sources in order to receive multiple exposures at relatively high levels, as would be necessary to cause TTS. Intermittent exposures—as would occur due to the brief, transient signals produced by these sources—require a higher cumulative SEL to induce TTS than would continuous exposures of the same duration ( i.e., intermittent exposure results in lower levels of TTS) (Mooney et al., 2009a; Finneran et al., 2010). Moreover, most marine mammals would more likely avoid a loud sound source rather than swim in such close proximity as to result in TTS. Kremser et al. (2005) noted that the probability of a cetacean swimming through the area of exposure when a sub-bottom profiler emits a pulse is small—because if the animal was in the area, it would have to pass the transducer at close range in order to be subjected to sound levels that could cause temporary threshold shift and would likely exhibit avoidance behavior to the area near the transducer rather than swim through at such a close range. Further, the restricted beam shape of the sub-bottom profiler and other HRG survey equipment makes it unlikely that an animal would be exposed more than briefly during the passage of the vessel. Boebel et al. (2005) concluded similarly for single and multibeam echosounders, and more recently, Lurton (2016) conducted a modeling exercise and concluded similarly that likely potential for acoustic injury from these types of systems is negligible, but that behavioral response cannot be ruled out. Animals may avoid the area around the survey vessels, thereby reducing exposure. Any disturbance to marine mammals is likely to be in the form of temporary avoidance or alteration of opportunistic foraging behavior near the survey location. Masking Masking is the obscuring of sounds of interest to an animal by other sounds, typically at similar frequencies. Marine mammals are highly dependent on sound, and their ability to recognize sound signals amid other sound is important in communication and detection of both predators and prey (Tyack, 2000). Background ambient sound may interfere with or mask the ability of an animal to detect a sound signal even when that signal is above its absolute hearing threshold. Even in the absence of anthropogenic sound, the marine environment is often loud. Natural ambient sound includes contributions from wind, waves, precipitation, other animals, and (at frequencies above 30 kHz) thermal sound resulting from molecular agitation (Richardson et al., 1995). Background sound may also include anthropogenic sound, and masking of natural sounds can result when human activities produce high levels of background sound. Conversely, if the background level of underwater sound is high ( e.g., on a day with strong wind and high waves), an anthropogenic sound source would not be detectable as far away as would be possible under quieter conditions and would itself be masked. Ambient sound is highly variable on continental shelves (Thompson, 1965; Myrberg, 1978; Desharnais et al., 1999). This results in a high degree of variability in the range at which marine mammals can detect anthropogenic sounds. Although masking is a phenomenon which may occur naturally, the introduction of loud anthropogenic sounds into the marine environment at frequencies important to marine mammals increases the severity and frequency of occurrence of masking. For example, if a baleen whale is exposed to continuous low-frequency sound from an industrial source, this would reduce the size of the area around that whale within which it can hear the calls of another whale. The components of background noise that are similar in frequency to the signal in question primarily determine the degree of masking of that signal. In general, little is known about the degree to which marine mammals rely upon detection of sounds from conspecifics, predators, prey, or other natural sources. In the absence of specific information about the importance of detecting these natural sounds, it is not possible to predict the impact of masking on marine mammals (Richardson et al., 1995). In general, masking effects are expected to be less severe when sounds are transient than when they are continuous. Masking is typically of greater concern for those marine mammals that utilize low-frequency communications, such as baleen whales, and from sources of lower frequency, because of how far low-frequency sounds propagate. Marine mammal species, including ESA-listed species, that may be exposed to survey noise are widely dispersed. As such, only a very small percentage of the population is likely to be within the radius of masking at any given time. Richardson et al. (1995) concludes broadly that, although further data are needed, localized or temporary increases in masking probably cause few problems for marine mammals, with the possible exception of populations highly concentrated in an ensonified area. While some number of marine mammals may be subject to occasional masking as a result of survey activity, temporary shifts in calling behavior to reduce the effects of masking, on the scale of no more than a few minutes, are not likely to result in failure of an animal to feed successfully, breed successfully, or complete its life history. Furthermore, marine mammal communications would not likely be masked appreciably by sound from most HRG survey equipment given the narrow beam widths, directionality of the signal, relatively small ensonified area, and the brief period when an individual mammal is likely to be exposed to sound from the HRG survey equipment. Marine mammal communications would not likely be masked appreciably by the sub-profiler or pingers' signals given the directionality of the signal and the brief period when an individual mammal is likely to be within its beam, as well as the higher frequencies. Non-Auditory Physical Effects (Stress) Classic stress responses begin when an animal's central nervous system perceives a potential threat to its homeostasis. That perception triggers stress responses regardless of whether a stimulus actually threatens the animal; the mere perception of a threat is sufficient to trigger a stress response (Moberg, 2000; Seyle, 1950). Once an animal's central nervous system perceives a threat, it mounts a biological response or defense that consists of a combination of the four general biological defense responses: Behavioral responses, autonomic nervous system responses, neuroendocrine responses, or immune responses. In the case of many stressors, an animal's first and sometimes most economical (in terms of biotic costs) response is behavioral avoidance of the potential stressor or avoidance of continued exposure to a stressor. An animal's second line of defense to stressors involves the sympathetic part of the autonomic nervous system and the classical “fight or flight” response which includes the cardiovascular system, the gastrointestinal system, the exocrine glands, and the adrenal medulla to produce changes in heart rate, blood pressure, and gastrointestinal activity that humans commonly associate with “stress.” These responses have a relatively short duration and may or may not have significant long-term effect on an animal's welfare. An animal's third line of defense to stressors involves its neuroendocrine systems; the system that has received the most study has been the hypothalamus-pituitary-adrenal system (also known as the HPA axis in mammals or the hypothalamus-pituitary-interrenal axis in fish and some reptiles). Unlike stress responses associated with the autonomic nervous system, virtually all neuro-endocrine functions that are affected by stress—including immune competence, reproduction, metabolism, and behavior—are regulated by pituitary hormones. Stress-induced changes in the secretion of pituitary hormones have been implicated in failed reproduction (Moberg, 1987; Rivier, 1995), altered metabolism (Elasser et al., 2000), reduced immune competence (Blecha, 2000), and behavioral disturbance. Increases in the circulation of glucocorticosteroids (cortisol, corticosterone, and aldosterone in marine mammals; see Romano et al., 2004) have been equated with stress for many years. The primary distinction between stress (which is adaptive and does not normally place an animal at risk) and distress is the biotic cost of the response. During a stress response, an animal uses glycogen stores that can be quickly replenished once the stress is alleviated. In such circumstances, the cost of the stress response would not pose a risk to the animal's welfare. However, when an animal does not have sufficient energy reserves to satisfy the energetic costs of a stress response, energy resources must be diverted from other biotic function, which impairs those functions that experience the diversion. For example, when mounting a stress response diverts energy away from growth in young animals, those animals may experience stunted growth. When mounting a stress response diverts energy from a fetus, an animal's reproductive success and its fitness will suffer. In these cases, the animals will have entered a pre-pathological or pathological state which is called “distress” (Seyle, 1950) or “allostatic loading” (McEwen and Wingfield, 2003). This pathological state will last until the animal replenishes its biotic reserves sufficient to restore normal function. Note that these examples involved a long-term (days or weeks) stress response exposure to stimuli. Relationships between these physiological mechanisms, animal behavior, and the costs of stress responses have also been documented fairly well through controlled experiments; because this physiology exists in every vertebrate that has been studied, it is not surprising that stress responses and their costs have been documented in both laboratory and free-living animals (for examples see, Holberton et al., 1996; Hood et al., 1998; Jessop et al., 2003; Krausman et al., 2004; Lankford et al., 2005; Reneerkens et al., 2002; Thompson and Hamer, 2000). Information has also been collected on the physiological responses of marine mammals to exposure to anthropogenic sounds (Fair and Becker, 2000; Romano et al., 2002). For example, Rolland et al. (2012) found that noise reduction from reduced ship traffic in the Bay of Fundy was associated with decreased stress in North Atlantic right whales. In a conceptual model developed by the Population Consequences of Acoustic Disturbance (PCAD) working group, serum hormones were identified as possible indicators of behavioral effects that are translated into altered rates of reproduction and mortality. Studies of other marine animals and terrestrial animals would also lead us to expect some marine mammals to experience physiological stress responses and, perhaps, physiological responses that would be classified as “distress” upon exposure to high frequency, mid-frequency and low-frequency sounds. For example, Jansen (1998) reported on the relationship between acoustic exposures and physiological responses that are indicative of stress responses in humans (for example, elevated respiration and increased heart rates). Jones (1998) reported on reductions in human performance when faced with acute, repetitive exposures to acoustic disturbance. Trimper et al. (1998) reported on the physiological stress responses of osprey to low-level aircraft noise while Krausman et al. (2004) reported on the auditory and physiology stress responses of endangered Sonoran pronghorn to military overflights. Smith et al. (2004a, 2004b), for example, identified noise-induced physiological transient stress responses in hearing-specialist fish ( i.e., goldfish) that accompanied short- and long-term hearing losses. Welch and Welch (1970) reported physiological and behavioral stress responses that accompanied damage to the inner ears of fish and several mammals. Hearing is one of the primary senses marine mammals use to gather information about their environment and to communicate with conspecifics. Although empirical information on the relationship between sensory impairment (TTS, PTS, and acoustic masking) on marine mammals remains limited, it seems reasonable to assume that reducing an animal's ability to gather information about its environment and to communicate with other members of its species would be stressful for animals that use hearing as their primary sensory mechanism. Therefore, we assume that acoustic exposures sufficient to trigger onset PTS or TTS would be accompanied by physiological stress responses because terrestrial animals exhibit those responses under similar conditions (NRC, 2003). More importantly, marine mammals might experience stress responses at received levels lower than those necessary to trigger onset TTS. Based on empirical studies of the time required to recover from stress responses (Moberg, 2000), we also assume that stress responses are likely to persist beyond the time interval required for animals to recover from TTS and might result in pathological and pre-pathological states that would be as significant as behavioral responses to TTS. In general, there are few data on the potential for strong, anthropogenic underwater sounds to cause non-auditory physical effects in marine mammals. Such effects, if they occur at all, would presumably be limited to short distances and to activities that extend over a prolonged period. The available data do not allow identification of a specific exposure level above which non-auditory effects can be expected (Southall et al., 2007). There is no definitive evidence that any of these effects occur even for marine mammals in close proximity to an anthropogenic sound source. In addition, marine mammals that show behavioral avoidance of survey vessels and related sound sources, are unlikely to incur non-auditory impairment or other physical effects. NMFS does not expect that the generally short-term, intermittent, and transitory HRG surveys would create conditions of long-term, continuous noise and chronic acoustic exposure leading to long-term physiological stress responses in marine mammals. Behavioral Disturbance Behavioral responses to sound are highly variable and context-specific. Many different variables can influence an animal's perception of and response to (nature and magnitude) an acoustic event. An animal's prior experience with a sound or sound source affects whether it is less likely (habituation) or more likely (sensitization) to respond to certain sounds in the future (animals can also be innately pre-disposed to respond to certain sounds in certain ways) (Southall et al., 2007). Related to the sound itself, the perceived nearness of the sound, bearing of the sound (approaching vs. retreating), similarity of a sound to biologically relevant sounds in the animal's environment ( i.e., calls of predators, prey, or conspecifics), and familiarity of the sound may affect the way an animal responds to the sound (Southall et al., 2007, DeRuiter et al., 2013). Individuals (of different age, gender, reproductive status, etc.) among most populations will have variable hearing capabilities, and differing behavioral sensitivities to sounds that will be affected by prior conditioning, experience, and current activities of those individuals. Often, specific acoustic features of the sound and contextual variables ( i.e., proximity, duration, or recurrence of the sound or the current behavior that the marine mammal is engaged in or its prior experience), as well as entirely separate factors such as the physical presence of a nearby vessel, may be more relevant to the animal's response than the received level alone. Studies by DeRuiter et al. (2012) indicate that variability of responses to acoustic stimuli depends not only on the species receiving the sound and the sound source, but also on the social, behavioral, or environmental contexts of exposure. Ellison et al. (2012) outlined an approach to assessing the effects of sound on marine mammals that incorporates contextual-based factors. The authors recommend considering not just the received level of sound, but also the activity the animal is engaged in at the time the sound is received, the nature and novelty of the sound ( i.e., is this a new sound from the animal's perspective), and the distance between the sound source and the animal. They submit that this “exposure context,” as described, greatly influences the type of behavioral response exhibited by the animal. This sort of contextual information is challenging to predict with accuracy for ongoing activities that occur over large spatial and temporal expanses. However, distance is one contextual factor for which data exist to quantitatively inform a take estimate. Other factors are often considered qualitatively in the analysis of the likely consequences of sound exposure, where supporting information is available. Exposure of marine mammals to sound sources can result in, but is not limited to, no response or any of the following observable response: Increased alertness; orientation or attraction to a sound source; vocal modifications; cessation of feeding; cessation of social interaction; alteration of movement or diving behavior; habitat abandonment (temporary or permanent); and, in severe cases, panic, flight, stranding, potentially resulting in death (Southall et al., 2007). A review of marine mammal responses to anthropogenic sound was first conducted by Richardson (1995). More recent reviews (Nowacek et al., 2007; DeRuiter et al., 2012 and 2013; Ellison et al., 2012) address studies conducted since 1995 and focused on observations where the received sound level of the exposed marine mammal(s) was known or could be estimated. Southall et al. (2016) states that results demonstrate that some individuals of different species display clear yet varied responses, some of which have negative implications, while others appear to tolerate high levels, and that responses may not be fully predicable with simple acoustic exposure metrics ( e.g., received sound level). Rather, the authors state that differences among species and individuals along with contextual aspects of exposure ( e.g., behavioral state) appear to affect response probability. Changes in dive behavior can vary widely. They may consist of increased or decreased dive times and surface intervals as well as changes in the rates of ascent and descent during a dive. Variations in dive behavior may reflect interruptions in biologically significant activities ( e.g., foraging) or they may be of little biological significance. Variations in dive behavior may also expose an animal to potentially harmful conditions ( e.g., increasing the chance of ship-strike) or may serve as an avoidance response that enhances survivorship. The impact of a variation in diving resulting from an acoustic exposure depends on what the animal is doing at the time of the exposure and the type and magnitude of the response. Avoidance is the displacement of an individual from an area as a result of the presence of a sound. Richardson et al. (1995) noted that avoidance reactions are the most obvious manifestations of disturbance in marine mammals. Avoidance is qualitatively different from the flight response, but also differs in the magnitude of the response ( i.e., directed movement, rate of travel, etc.). Oftentimes avoidance is temporary, and animals return to the area once the noise has ceased. However, longer term displacement is possible and can lead to changes in abundance or distribution patterns of the species in the affected region if they do not become acclimated to the presence of the sound (Blackwell et al., 2004; Bejder et al., 2006; Teilmann et al., 2006). Acute avoidance responses have been observed in captive porpoises and pinnipeds exposed to a number of different sound sources (Kastelein et al., 2001; Finneran et al., 2003; Kastelein et al., 2006a; Kastelein et al., 2006b). Southall et al. (2007) reviewed the available literature on marine mammal hearing and behavioral and physiological responses to human-made sound with the goal of proposing exposure criteria for certain effects. This peer-reviewed compilation of literature is very valuable, though Southall et al. (2007) note that not all data are equal, some have poor statistical power, insufficient controls, and/or limited information on received levels, background noise, and other potentially important contextual variables—such data were reviewed and sometimes used for qualitative illustration but were not included in the quantitative analysis for the criteria recommendations. All of the studies considered, however, contain an estimate of the received sound level when the animal exhibited the indicated response. For purposes of analyzing responses of marine mammals to anthropogenic sound and developing criteria, NMFS (2018) differentiates between pulse (impulsive) sounds (single and multiple) and non-pulse sounds. For purposes of evaluating the potential for take of marine mammals resulting from underwater noise due to the conduct of the proposed HRG surveys (operation of USBL positioning system and the sub-bottom profilers), the criteria for Level A harassment (PTS onset) from impulsive noise was used as prescribed in NMFS (2018) and the threshold level for Level B harassment (160 dB RMS re 1 µPa) was used to evaluate takes from behavioral harassment. Studies that address responses of low-frequency cetaceans to sounds include data gathered in the field and related to several types of sound sources, including: Vessel noise, drilling and machinery playback, low-frequency M-sequences (sine wave with multiple phase reversals) playback, tactical low-frequency active sonar playback, drill ships, and non-pulse playbacks. These studies generally indicate no (or very limited) responses to received levels in the 90 to 120 dB re: 1µPa range and an increasing likelihood of avoidance and other behavioral effects in the 120 to 160 dB range. As mentioned earlier, though, contextual variables play a very important role in the reported responses and the severity of effects do not increase linearly with received levels. Also, few of the laboratory or field datasets had common conditions, behavioral contexts, or sound sources, so it is not surprising that responses differ. The studies that address responses of mid-frequency cetaceans to sounds include data gathered both in the field and the laboratory and related to several different sound sources, including: Pingers, drilling playbacks, ship and ice-breaking noise, vessel noise, Acoustic harassment devices (AHDs), Acoustic Deterrent Devices (ADDs), mid-frequency active sonar, and non-pulse bands and tones. Southall et al. (2007) were unable to come to a clear conclusion regarding the results of these studies. In some cases animals in the field showed significant responses to received levels between 90 and 120 dB, while in other cases these responses were not seen in the 120 to 150 dB range. The disparity in results was likely due to contextual variation and the differences between the results in the field and laboratory data (animals typically responded at lower levels in the field). The studies that address the responses of mid-frequency cetaceans to impulse sounds include data gathered both in the field and the laboratory and related to several different sound sources, including: Small explosives, airgun arrays, pulse sequences, and natural and artificial pulses. The data show no clear indication of increasing probability and severity of response with increasing received level. Behavioral responses seem to vary depending on species and stimuli. The studies that address responses of high-frequency cetaceans to sounds include data gathered both in the field and the laboratory and related to several different sound sources, including: Pingers, AHDs, and various laboratory non-pulse sounds. All of these data were collected from harbor porpoises. Southall et al. (2007) concluded that the existing data indicate that harbor porpoises are likely sensitive to a wide range of anthropogenic sounds at low received levels (around 90 to 120 dB), at least for initial exposures. All recorded exposures above 140 dB induced profound and sustained avoidance behavior in wild harbor porpoises (Southall et al., 2007). Rapid habituation was noted in some but not all studies. The studies that address the responses of pinnipeds in water to sounds include data gathered both in the field and the laboratory and related to several different sound sources, including: AHDs, various non-pulse sounds used in underwater data communication, underwater drilling, and construction noise. Few studies exist with enough information to include them in the analysis. The limited data suggest that exposures to non-pulse sounds between 90 and 140 dB generally do not result in strong behavioral responses of pinnipeds in water, but no data exist at higher received levels (Southall et al., 2007). The studies that address the responses of pinnipeds in water to impulse sounds include data gathered in the field and related to several different sources, including: Small explosives, impact pile driving, and airgun arrays. Quantitative data on reactions of pinnipeds to impulse sounds is limited, but a general finding is that exposures in the 150 to 180 dB range generally have limited potential to induce avoidance behavior (Southall et al., 2007). 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) (Richardson et al., 1995; Erbe and Farmer, 2000; Tyack, 2000; Erbe et al., 2016). 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. The ability of a noise source to mask biologically important sounds depends on the characteristics of both the noise source and the signal of interest ( e.g., signal-to-noise ratio, temporal variability, direction), in relation to each other and to an animal's hearing abilities ( e.g., sensitivity, frequency range, critical ratios, frequency discrimination, directional discrimination, age or TTS hearing loss), and existing ambient noise and propagation conditions. Masking these acoustic signals can disturb the behavior of individual animals, groups of animals, or entire populations. Under certain circumstances, marine mammals experiencing significant masking could also be impaired from maximizing their performance fitness in survival and reproduction. Therefore, when the coincident (masking) sound is man-made, it may be considered harassment when disrupting or altering critical behaviors. The frequency range of the potentially masking sound is important in determining any potential behavioral impacts. For example, low-frequency signals may have less effect on high-frequency echolocation sounds produced by odontocetes but are more likely to affect detection of mysticete communication calls and other potentially important natural sounds such as those produced by surf and some prey species. The masking of communication signals by anthropogenic noise may be considered as a reduction in the communication space of animals ( e.g., Clark et al., 2009; Matthews et al., 2016) and may result in energetic or other costs as animals change their vocalization behavior ( e.g., Miller et al., 2000; Foote et al., 2004; Parks et al., 2007; Di Iorio and Clark, 2009; Holt et al., 2009). Marine mammals are likely to avoid the HRG survey activity, especially harbor porpoises, while the harbor seals might be attracted to them out of curiosity. However, because the sub-bottom profilers and other HRG survey equipment operate from a moving vessel, and the predicted maximum distance to the 160 dB RMS re 1µPa isopleth (Level B harassment criteria) is 178 m, the area and time that this equipment would be affecting a given location is very small. Further, once an area has been surveyed, it is not likely that it will be surveyed again, therefore reducing the likelihood of repeated HRG-related impacts within the survey area. A number of cetacean mass stranding events have been linked to use of military active sonar. We considered the potential for HRG equipment to result in standings or indirect injury or mortality based on the 2008 mass stranding of approximately one hundred melon-headed whales in a Madagascar lagoon system. An investigation of the event indicated that use of a high-frequency mapping system (12-kHz multibeam echosounder) was the most plausible and likely initial behavioral trigger of the event, while providing the caveat that there is no unequivocal and easily identifiable single cause (Southall et al., 2013). The investigatory panel's conclusion was based on (1) very close temporal and spatial association and directed movement of the survey with the stranding event; (2) the unusual nature of such an event coupled with previously documented apparent behavioral sensitivity of the species to other sound types (Southall et al., 2006; Brownell et al., 2009); and (3) the fact that all other possible factors considered were determined to be unlikely causes. Specifically, regarding survey patterns prior to the event and in relation to bathymetry, the vessel transited in a north-south direction on the shelf break parallel to the shore, ensonifying large areas of deep-water habitat prior to operating intermittently in a concentrated area offshore from the stranding site; this may have trapped the animals between the sound source and the shore, thus driving them towards the lagoon system. The investigatory panel systematically excluded or deemed highly unlikely nearly all potential reasons for these animals leaving their typical pelagic habitat for an area extremely atypical for the species ( i.e., a shallow lagoon system). Notably, this was the first time that such a system has been associated with a stranding event. The panel also noted several site- and situation-specific secondary factors that may have contributed to the avoidance responses that led to the eventual entrapment and mortality of the whales. Specifically, shoreward-directed surface currents and elevated chlorophyll levels in the area preceding the event may have played a role (Southall et al., 2013). The report also notes that prior use of a similar system in the general area may have sensitized the animals and also concluded that, for odontocete cetaceans that hear well in higher frequency ranges where ambient noise is typically quite low, high-power active sonars operating in this range may be more easily audible and have potential effects over larger areas than low frequency systems that have more typically been considered in terms of anthropogenic noise impacts. It is, however, important to note that the relatively lower output frequency, higher output power, and complex nature of the system implicated in this event, in context of the other factors noted here, likely produced a fairly unusual set of circumstances that indicate that such events would likely remain rare and are not necessarily relevant to use of lower-power, higher-frequency systems more commonly used for HRG survey applications. The risk of similar events recurring may be very low, given the extensive use of active acoustic systems used for scientific and navigational purposes worldwide on a daily basis and the lack of direct evidence of such responses previously reported. Tolerance Numerous studies have shown that underwater sounds from industrial activities are often readily detectable by marine mammals in the water at distances of many kilometers. However, other studies have shown that marine mammals at distances more than a few kilometers away often show no apparent response to industrial activities of various types (Miller et al., 2005). This is often true even in cases when the sounds must be readily audible to the animals based on measured received levels and the hearing sensitivity of that mammal group. Although various baleen whales, toothed whales, and (less frequently) pinnipeds have been shown to react behaviorally to underwater sound from sources such as airgun pulses or vessels under some conditions, at other times, mammals of all three types have shown no overt reactions ( e.g., Malme et al., 1986; Richardson et al., 1995; Madsen and Mohl, 2000; Croll et al., 2001; Jacobs and Terhune, 2002; Madsen et al., 2002; Miller et al., 2005). In general, pinnipeds seem to be more tolerant of exposure to some types of underwater sound than are baleen whales. Richardson et al. (1995) found that vessel sound does not seem to strongly affect pinnipeds that are already in the water. Richardson et al. (1995) went on to explain that seals on haulouts sometimes respond strongly to the presence of vessels and at other times appear to show considerable tolerance of vessels, and Brueggeman et al. (1992) observed ringed seals ( Pusa hispida ) hauled out on ice pans displaying short-term escape reactions when a ship approached within 0.16-0.31 mi (0.25-0.5 km). Due to the relatively high vessel traffic in the Survey Area it is possible that marine mammals are habituated to noise from project vessels in the area. Vessel Strike Ship strikes of marine mammals can cause major wounds, which may lead to the death of the animal. An animal at the surface could be struck directly by a vessel, a surfacing animal could hit the bottom of a vessel, or a vessel's propeller could injure an animal just below the surface. The severity of injuries typically depends on the size and speed of the vessel (Knowlton and Kraus, 2001; Laist et al., 2001). The most vulnerable marine mammals are those that spend extended periods of time at the surface in order to restore oxygen levels within their tissues after deep dives ( e.g., the sperm whale). In addition, some baleen whales, such as the North Atlantic right whale, seem generally unresponsive to vessel sound, making them more susceptible to vessel collisions (Nowacek et al., 2004). These species are primarily large, slow moving whales. Smaller marine mammals ( e.g., bottlenose dolphin) move quickly through the water column and are often seen riding the bow wave of large ships. Marine mammal responses to vessels may include avoidance and changes in dive pattern (NRC, 2003). An examination of all known ship strikes from all shipping sources (civilian and military) indicates vessel speed is a principal factor in whether a vessel strike results in death (Knowlton and Kraus, 2001; Laist et al., 2001; Jensen and Silber, 2003; Vanderlaan and Taggart, 2007). In assessing records with known vessel speeds, Laist et al. (2001) found a direct relationship between the occurrence of a whale strike and the speed of the vessel involved in the collision. The authors concluded that most deaths occurred when a vessel was traveling in excess of 24.1 km/h (14.9 mph; 13 knots). Given the slow vessel speeds and predictable course necessary for data acquisition, ship strike is unlikely to occur during the geophysical and geotechnical surveys. Most marine mammals would be able to easily avoid vessels and are likely already habituated to the presence of numerous vessels in the area. Further, Orsted shall implement measures ( e.g., vessel speed restrictions and separation distances; see Proposed Mitigation Measures ) set forth in the BOEM Lease to reduce the risk of a vessel strike to marine mammal species in the Survey Area. Finally, survey vessels will travel at slow speeds (approximately 4 knots) during the survey, which reduces the risk of injury in the unlikely the event a survey vessel strikes a marine mammal. Effects on Marine Mammal Habitat Bottom disturbance associated with the HRG activities may include grab sampling to validate the seabed classification obtained from the multibeam echosounder/sidescan sonar data. This will typically be accomplished using a Mini-Harmon Grab with 0.1 m 2 sample area or the slightly larger Harmon Grab with a 0.2 m 2 sample area. This limited and highly localized impact to habitat in relation to the comparatively vast area of surrounding open ocean, would not be expected to result in any effects to prey availability. The HRG survey equipment itself will not disturb the seafloor. There are no feeding areas, rookeries, or mating grounds known to be biologically important to marine mammals within the proposed project area with the exception of a feeding BIA for fin whales and migratory BIA for North Atlantic right whales which were described previously. There is also no designated critical habitat for any ESA-listed marine mammals. NMFS' regulations at 50 CFR part 224 designated the nearshore waters of the Mid-Atlantic Bight as the Mid-Atlantic U.S. Seasonal Management Area (SMA) for right whales in 2008. Mandatory vessel speed restrictions are in place in that SMA from November 1 through April 30 to reduce the threat of collisions between ships and right whales around their migratory route and calving grounds. We are not aware of any available literature on impacts to marine mammal prey species from HRG survey equipment. However, because the HRG survey equipment introduces noise to the marine environment, there is the potential for avoidance of the area around the HRG survey activities by marine mammal prey species. Any avoidance of the area on the part of marine mammal prey species would be expected to be short term and temporary. Because of the temporary nature of the disturbance, the availability of similar habitat and resources ( e.g., prey species) in the surrounding area, and the lack of important or unique marine mammal habitat, the impacts to marine mammals and the food sources that they utilize are not expected to cause significant or long-term consequences for individual marine mammals or their populations. Impacts on marine mammal habitat from the proposed activities will be temporary, insignificant, and discountable. 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, 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 be by Level B harassment only, in the form of disruption of behavioral patterns for individual marine mammals resulting from exposure to sound from HRG equipment. Based on the nature of the activity and the anticipated effectiveness of the mitigation measures ( i.e., shutdown—discussed in detail below in Proposed Mitigation section), Level A harassment is neither anticipated nor proposed to be authorized. As described previously, no 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 Using the best available science, NMFS has developed 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 for non-explosive sources —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., 2011). Based on what the available science indicates and the practical need to use a threshold based on a factor that is both predictable and measurable for most activities, NMFS uses a generalized acoustic threshold based on received level to estimate the onset of behavioral harassment. NMFS predicts that marine mammals are likely to be behaviorally harassed in a manner we consider Level B harassment when exposed to underwater anthropogenic noise above received levels of 120 dB re 1 μPa (rms) for continuous ( e.g., vibratory pile-driving, drilling) and above 160 dB re 1 μPa (rms) for non-explosive impulsive ( e.g., seismic airguns) or intermittent ( e.g., scientific sonar) sources. Orsted's proposed activities include the use of intermittent impulsive (HRG Equipment) sources, and therefore the 160 dB re 1 μPa (rms) threshold is applicable. Level A harassment for non-explosive sources —NMFS' Technical Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammal Hearing (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). These thresholds are provided in Table 4 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: http://www.nmfs.noaa.gov/pr/acoustics/guidelines.htm . Table 4—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 that will feed into identifying the area ensonified above the acoustic thresholds, which include source levels and transmission loss coefficient. When NMFS' Acoustic Technical Guidance (2016) was published, in recognition of the fact that ensonified area/volume could be more technically challenging to predict because of the duration component of the new thresholds, NMFS developed an optional User Spreadsheet that includes tools to help predict takes. We note that because of some of the assumptions included in the methods used for these tools, we anticipate that isopleths produced are typically going to be overestimates of some degree, which will result in some degree of overestimate of Level A take. However, these tools offer the best way to predict appropriate isopleths when more sophisticated 3D 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 HRG survey equipment proposed for use in Orsted's activity, 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. Orsted conducted field verification tests on different types of HRG equipment within the proposed Lease Areas during previous site characterization survey activities. NMFS is proposing to authorize take in these same three Lease Areas listed below. • OCS-A 0486 & OCS-A 0487: Marine Acoustics, Inc. (MAI), under contract to Oceaneering International completed an underwater noise monitoring program for the field verification for equipment to be used to survey the Skipjack Windfarm Project (MAI 2018a; 2018b). • OCS-A 0500 Lease Area: The Gardline Group (Gardline), under contract to Alpine Ocean Seismic Survey, Inc., completed an underwater noise monitoring program for the field verification within the Lease Area prior to the commencement of the HRG survey which took place between August 14 and October 6, 2016 (Gardline 2016a, 2016b, 2017). Additional field verifications were completed by the RPS Group, under contract to Terrasond prior to commencement of the 2018 HRG field survey campaign (RPS 2018). Field Verification results are shown in Table 5. The purpose of the field verification programs was to determine distances to the regulatory thresholds for injury/mortality and behavior disturbance of marine mammals that were established during the permitting process. As part of their application, Orsted collected field verified source levels and calculated the differential between the averaged measured field verified source levels versus manufacturers' reported source levels for each tested piece of HRG equipment. The results of the field verification studies were used to derive the variability in source levels based on the extrapolated values resulting from regression analysis. These values were used to further calibrate calculations for a specific suite of HRG equipment of similar type. Orsted stated that the calculated differential accounts for both the site specific environmental conditions and directional beam width patterns and can be applied to similar HRG equipment within one of the specified equipment categories ( e.g., USBL & GAPS Transceivers, Shallow Sub-Bottom Profilers (SBP), Parametric SBP, Medium Penetration SBP (Sparker), and Medium Penetration SBP (Boomer)). For example, the manufacturer of the Geosource 800J medium penetration SBP reported a source level of 206 dB RMS. The field verification study measured a source level of 189 dB RMS (Gardline 2016a, 2017). Therefore, the differential between the manufacturer and field verified SL is −17 dB RMS. Orsted proposed to apply this differential (−17 dB) to other HRG equipment in the medium penetration SBP (sparker) category with an output of approximately 800 joules. Orsted employed this methodology for all non-field verified equipment within a specific equipment category. These new differential-based proxy SLs were inserted into the User Spreadsheet and used to calculate the Level A and Level B harassment isopleths for the various hearing groups. Table 5 shows the field verified equipment SSV results as well as applicable non-verified equipment broken out by equipment category. Table 5—Summary of Field Verified HRG Equipment SSV Results and Applicable HRG Devices Grouped by Category Type Representative HRG survey equipment Operating frequencies Baseline source level (dB re 1 μPa) Source level measured during Ørsted FV surveys (dB re 1 μPa) 2019 HRG survey data acquisition equipment USBL & GAPS Transponder and Transceiver a Sonardyne Ranger 2 19 to 34 kHz 200 dB RMS 166 dB RMS Sonardyne Ranger 2 USBL HPT 5/7000; Sonardyne Ranger 2 USBL HPT 3000; Sonardyne Scout Pro; Easytrak Nexus 2 USBL; IxSea GAPS System; Kongsberg HiPAP 501/502 USBL; Edgetech BATS II. Shallow Sub-Bottom Profilers (Chirp) a c GeoPulse 5430 A Sub-bottom Profiler 1.5 to 18 kHz 214 dB RMS 173 dB RMS Edgetech 3200; Teledyne Benthos Chirp III—TTV 170. EdgeTech 512 0.5 to 12 kHz 177 dB RMS 166 dB RMS PanGeo LF Chirp; PanGeo HF Chirp; EdgeTech 216; EdgeTech 424. Parametric Sub-Bottom Profiler d Innomar SES-2000 Medium 100 85 to 115 247 dB RMS 187 dB RMS Innomar SES-2000 Standard & Plus; Innomar SES-2000 Medium 70; Innomar SES-2000 Quattro; PanGeo 2i Parametric. Medium Penetration Sub-Bottom Profiler (Sparker) a Geo-Resources Geo-Source 600 J 0.05 to 5 kHz 214 dB Peak ; 205 dB RMS 206 dB Peak ; 183 dB RMS GeoMarine Geo-Source 400tip; Applied Acoustics Dura-Spark 400 System. Geo-Resources Geo-Source 800 J 0.05 to 5 kHz 215 dB Peak ; 206 dB RMS 212 dB Peak ; 189 dB RMS GeoMarine Geo-Source 800. Medium Penetration Sub-Bottom Profiler (Boomer) b c Applied Acoustics S-Boom Triple Plate Boomer (700J) 0.1 to 5 211 dB Peak ; 205 dB RMS 195 dB Peak ; 173 dB RMS Not used for any other equipment. Applied Acoustics S-Boom Triple Plate Boomer (1000J) 0.250 to 8 kHz 228 dB Peak ; 208 dB RMS 215 dB Peak ; 198 dB RMS Not used for any other equipment. Sources: a Gardline 2016a, 2017; b RPS 2018; c MAI 2018a; d Subacoustech 2018 After careful consideration, NMFS concluded that the use of differentials to derive proxy SLs is not appropriate or acceptable. NMFS determined that when field verified measurements are compared to the source levels measured in a controlled experimental setting ( i.e., Crocker and Fratantonio, 2016), there are significant discrepancies in isopleth distances for the same equipment that cannot be explained solely by absorption and scattering of acoustic energy. There are a number of variables, including potential differences in propagation rate, operating frequency, beam width, and pulse width that make us question whether SL differential values can be universally applied across different pieces of equipment, even if they fall within the same equipment category. Therefore, NMFS did not employ Orsted's proposed use of differentials to determine Level A and Level B harassment isopleths or proposed take estimates. As noted above, much of the HRG equipment proposed for use during Orsted's survey has not been field-verified. NMFS employed an alternate approach in which data reported by Crocker and Fratantonio (2016) was used to establish injury and behavioral harassment zones. If Crocker and Fratantonio (2016) did not provide data on a specific piece of equipment within a given equipment category, the SLs reported in the study for measured equipment are used to represent all the other equipment within that category, regardless of whether any of the devices has been field verified. If SSV data from Crocker and Fratantonio (2016) is not available across an entire equipment category, NMFS instead adopted the field verified results from equipment that had been tested. Here, the largest field verified SL was used to represent the entire equipment category. These values were applied to the User Spreadsheet to calculate distances for each of the proposed HRG equipment categories that might result in harassment of marine mammals. Inputs to the User Spreadsheet are shown in Table 6. The source levels used in Table 6 are from field verified values shown in Table 5. However, source levels for the EdgeTech 512 (177 dB RMS) and Applied Acoustics S-Boom Triple Plate Boomer (1,000j) (203 dB RMS) were derived from Crocker and Fratantonio (2016). Table 7 depicts isopleths that could result in injury to a specific hearing group. Table 6—Inputs to the User Spreadsheet Spreadsheet tab used USBL D: Mobile source: Non-impulsive, intermittent Shallow penetration SBP-chirp D: Mobile source: Non-impulsive, intermittent Shallow penetration SBP-chirp D: Mobile source: Non-impulsive, intermittent Parametric SBP D: Mobile source: Non-impulsive, intermittent Medium penetration SBP—sparker F: Mobile source: impulsive, intermittent Medium penetration SBP—boomer F: Mobile source: impulsive, intermittent HRG Equipment Sonardyne Ranger 2 GeoPulse 5430 A Sub-bottom Profiler EdgeTech 512 Innomar SES 2000 Medium 100 GeoMarine Geo-Source 800 J Applied Acoustics S-Boom Triple Plate Boomer (1,000j). Source Level (dB RMS SPL) 166 173 177 * 187 212 Pk; 189 RMS 209 Pk; 203 RMS.* Weighting Factor Adjustment (kHz) 26 4.5 3 42 2 0.6. Source Velocity (m/s) 2.045 2.045 2.045 2.045 2.045 2.045. Pulse Duration (seconds) 0.3 0.025 0.0022 0.001 0.055 0.0006. 1/Repetition rate ‸ (seconds) 1 0.1 0.50 0.025 0.5 0.333. Source Level (PK SPL) 212 215. Propagation (xLogR) 20 20 20 20 20 20. * Crocker and Fratantonio (2016). Table 7—Maximum Distances to Level A Harassment Isopleths Based on Data From Field Verification Studies and Crocker and Fratantonio (2016) (Where Available) Representative HRG survey equipment Marine mammal group PTS onset Lateral distance (m) USBL/GAPS Positioning Systems Sonardyne Ranger 2 LF cetaceans 199 dB SEL cum MF cetaceans 198 dB SEL cum HF cetaceans 173 dB SEL cum <1 Phocid pinnipeds 201 dB SEL cum Shallow Sub-Bottom Profiler (Chirp) Edgetech 512 LF cetaceans 199 dB SEL cum MF cetaceans 198 dB SEL cum HF cetaceans 173 dB SEL cum Phocid pinnipeds 201 dB SEL cum GeoPulse 5430 A Sub-bottom Profiler LF cetaceans 199 dB SEL cum MF cetaceans 198 dB SEL cum HF cetaceans 173 dB SEL cum Phocid pinnipeds 201 dB SEL cum Parametric Sub-bottom Profiler Innomar SES-2000 Medium 100 LF cetaceans 199 dB SEL cum MF cetaceans 198 dB SEL cum HF cetaceans 173 dB SEL cum <2 Phocid pinnipeds 201 dB SEL cum Medium Penetration Sub-Bottom Profiler (Sparker) GeoMarine Geo-Source 800tip LF cetaceans 219 dBpeak, 183 dB SEL cum —, < 1 MF cetaceans 230 dBpeak, 185 dB SEL cum HF cetaceans 202 dBpeak, 155 dB SEL cum <4, <1 Phocid pinnipeds 218 dBpeak, 185 dB SEL cum —, <1 Medium Penetration Sub-Bottom Profiler (Boomer) Applied Acoustics S-Boom Triple Plate Boomer (1000j) LF cetaceans 219 dBpeak, 183 dB SEL cum —, <1 MF cetaceans 230 dBpeak, 185 dB SEL cum HF cetaceans 202 dBpeak, 155 dB SEL cum <3, — Phocid pinnipeds 218 dBpeak, 185 dB SEL cum In the absence of Crocker and Fratantonio (2016) data, as noted above, NMFS determined that field verified SLs could be used to delineate Level A harassment isopleths which can be used to represent all of the HRG equipment within that specific category. While there is some uncertainty given that the SLs associated with assorted HRG equipment are variable within a given category, all of the predicted distances based on the field-verified source level are small enough to support a prediction that Level A harassment is unlikely to occur. While it is possible that Level A harassment isopleths of non-verified equipment would be larger than those shown in Table 7, it is unlikely that such zones would be substantially greater in size such that take by Level A harassment would be expected. Therefore, NMFS is not proposing to authorize any take from Level A harassment. The methodology described above was also applied to calculate Level B harassment isopleths as shown in Table 8. Note that the spherical spreading propagation model (20logR) was used to derive behavioral harassment isopleths for equipment measured by Crocker and Fratantonio (2016) data. However, the practical spreading model (15logR) was used to conservatively assess distances to Level B harassment thresholds for equipment not tested by Crocker and Fratantonio (2016). Table 8 shows calculated Level B harassment isopleths for specific equipment tested by Crocker and Fratantonio (2016) which is applied to all devices within a given category. In cases where Crocker and Fratantonio (2016) collected measurement on more than one device, the largest calculated isopleth is used to represent the entire category. Table 8 also shows field-verified SLs and associated Level B harassment isopleths for equipment categories that lack relevant Crocker & Fratantonio (2016) measurements. Additionally, Table 8 also references the specific field verification studies that were used to develop the isople [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%3A2019-15802. Public record. Not legal advice.