# Takes of Marine Mammals Incidental to Specified Activities; Low-Energy Marine Geophysical Survey in the Southwest Pacific Ocean, East of New Zealand, May to June 2015 > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A2015-06261 ## Record - **Collection:** Federal Register - **Document type:** Notice - **Published:** March 20, 2015 - **Citation:** 80 FR 15060 ## Text DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration RIN 0648-XD727 Takes of Marine Mammals Incidental to Specified Activities; Low-Energy Marine Geophysical Survey in the Southwest Pacific Ocean, East of New Zealand, May to June 2015 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 the Scripps Institution of Oceanography (SIO), on behalf of SIO and the U.S. National Science Foundation (NSF), for an Incidental Harassment Authorization (IHA) to take marine mammals, by harassment, incidental to conducting a low-energy marine geophysical (seismic) survey in the Southwest Pacific Ocean, East of New Zealand, May to June 2015. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting comments on its proposal to issue an IHA to SIO to incidentally harass, by Level B harassment only, 32 species of marine mammals during the specified activity. DATES: Comments and information must be received no later than April 20, 2015. ADDRESSES: Comments on the application should be addressed to Jolie Harrison, Chief, Permits and Conservation Division, Office of Protected Resources, National Marine Fisheries Service, 1315 East-West Highway, Silver Spring, MD 20910. The mailbox address for providing email comments is ITP.Goldstein@noaa.gov. Please include 0648-XD727 in the subject line. NMFS is not responsible for email comments sent to addresses other than the one provided here. Comments sent via email, including all attachments, must not exceed a 25-megabyte file size. Instructions: All comments received are a part of the public record and will generally be posted to: http://www.nmfs.noaa.gov/pr/permits/incidental/ without change. All Personal Identifying Information (for example, name, address, etc.) voluntarily submitted by the commenter may be publicly accessible. Do not submit Confidential Business Information or otherwise sensitive or protected information. A copy of the IHA application may be obtained by writing to the address specified above, telephoning the contact listed here (see FOR FURTHER INFORMATION CONTACT ) or visiting the Internet at: http://www.nmfs.noaa.gov/pr/permits/incidental/. Documents cited in this notice may also be viewed by appointment, during regular business hours, at the aforementioned address. A “Draft Environmental Analysis of a Low-Energy Marine Geophysical Survey by the R/V Roger Revelle in the Southwest Pacific Ocean, East of New Zealand, May to June 2015” (Draft Environmental Analysis) in accordance with the National Environmental Policy Act (NEPA) and the regulations published by the Council of Environmental Quality (CEQ), has been prepared on behalf of NSF and SIO. It is posted at the foregoing site. NMFS has independently evaluated the Draft Environmental Analysis and has prepared a separate NEPA analysis titled “Draft Environmental Assessment on the Issuance of an Incidental Harassment Authorization to the Scripps Institution of Oceanography to Take Marine Mammals by Harassment Incidental to a Low-Energy Marine Geophysical Survey in the Southwest Pacific Ocean, East of New Zealand, May to June 2015.” Information in the SIO's IHA application, Draft Environmental Analysis, Draft EA and this notice of the proposed IHA collectively provide the environmental information related to proposed issuance of the IHA for public review and comment. NMFS will review all comments submitted in response to this notice as we complete the NEPA process, including a decision of whether to sign a Finding of No Significant Impact (FONSI), prior to a final decision on the IHA request. FOR FURTHER INFORMATION CONTACT: Howard Goldstein or Jolie Harrison, Office of Protected Resources, NMFS, 301-427-8401. SUPPLEMENTARY INFORMATION: Background Sections 101(a)(5)(A) and (D) of the MMPA, (16 U.S.C. 1361 et seq. ) direct the Secretary of Commerce (Secretary) to allow, upon request, the incidental, but not intentional, taking of small numbers of marine mammals by United States citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region if certain findings are made and either regulations are issued or, if the taking is limited to harassment, a notice of a proposed authorization is provided to the public for review. An authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s), will not have an unmitigable adverse impact on the availability of the species or stock(s) for subsistence uses (where relevant), and if the permissible methods of taking and requirements pertaining to the mitigation, monitoring and reporting of such takings are set forth. NMFS has defined “negligible impact” in 50 CFR 216.103 as “. . . an impact resulting from the specified activity that cannot be reasonably expected to, and is not reasonably likely to, adversely affect the species or stock through effects on annual rates of recruitment or survival.” Section 101(a)(5)(D) of the MMPA established an expedited process by which citizens of the United States can apply for an authorization to incidentally take small numbers of marine mammals by harassment. Section 101(a)(5)(D) of the MMPA establishes a 45-day time limit for NMFS's review of an application, followed by a 30-day public notice and comment period on any proposed authorizations for the incidental harassment of small numbers of marine mammals. Within 45 days of the close of the public comment period, NMFS must either issue or deny the authorization. Except with respect to certain activities not pertinent here, the MMPA defines “harassment” as: any act of pursuit, torment, or annoyance which (i) has the potential to injure a marine mammal or marine mammal stock in the wild [Level A harassment]; or (ii) has the potential to disturb a marine mammal or marine mammal stock in the wild by causing disruption of behavioral patterns, including, but not limited to, migration, breathing, nursing, breeding, feeding, or sheltering [Level B harassment]. Summary of Request On December 15, 2014, NMFS received an application from SIO, on behalf of SIO and NSF, requesting that NMFS issue an IHA for the take, by Level B harassment only, of small numbers of marine mammals incidental to conducting a low-energy marine seismic survey as well as heat-flow measurements in the Southwest Pacific Ocean, at three sites off the east coast of New Zealand, during May to June 2015. The sediment coring component of the proposed project, which was described in the IHA application and Draft Environmental Analysis, was not funded and no piston or gravity coring for seafloor samples would be conducted during the low-energy seismic survey. The low-energy seismic survey would take place within the Exclusive Economic Zone (EEZ) and outside the territorial waters of New Zealand. On behalf of SIO, the U.S. Department of State is seeking authorization from New Zealand for clearance to work within the EEZ. The research would be conducted by Oregon State University and funded by the U.S. National Science Foundation (NSF). SIO plan to use one source vessel, the R/V Roger Revelle ( Revelle ), and a seismic airgun array and hydrophone streamer to collect seismic data in the Southwest Pacific Ocean, East of New Zealand. SIO plans to use conventional low-energy, seismic methodology to perform marine-based studies in the Southwest Pacific Ocean (see Figure 1 of the IHA application). The studies would involve a low-energy seismic survey and heat-flow measurements from the seafloor to meet a number of research goals. In addition to the proposed operations of the seismic airgun array and hydrophone streamer, SIO intends to operate two additional acoustical data acquisition systems—a multi-beam echosounder and sub-bottom profiler continuously throughout the low-energy seismic survey. Acoustic stimuli ( i.e., increased underwater sound) generated during the operation of the seismic airgun array have the potential to cause behavioral disturbance for marine mammals in the proposed study area. This is the principal means of marine mammal taking associated with these activities, and SIO have requested an authorization to take 32 species of marine mammals by Level B harassment. Take is not expected to result from the use of the multi-beam echosounder and sub-bottom profiler, as the brief exposure of marine mammals to one pulse, or small numbers of signals, to be generated by these instruments in this particular case is not likely to result in the harassment of marine mammals. Also, NMFS does not expect take to result from collision with the source vessel because it is a single vessel moving at a relatively slow, constant cruise speed of 5 knots ([kts]; 9.3 kilometers per hour [km/hr]; 5.8 miles per hour [mph]) during seismic acquisition within the study area, for a relatively short period of time (approximately 27 operational days). It is likely that any marine mammal would be able to avoid the vessel. Description of the Proposed Specified Activity Overview SIO proposes to use one source vessel, the Revelle, a two GI airgun array and one hydrophone streamer to conduct the conventional seismic survey as part of the NSF-funded research project “Collaborative Research: The Thermal Regime of the Hikurangi Subduction Zone and Shallow Slow Slip Events, New Zealand.” In addition to the airguns, SIO intends to conduct a bathymetric survey and heat-flow measurements at three sites off the southwest coast of North Island and northeast coast of South Island, New Zealand from the Revelle during the proposed low-energy seismic survey. Proposed Dates and Duration The Revelle is expected to depart from Auckland, New Zealand on approximately May 18, 2015 and arrive at Napier, New Zealand on approximately June 18, 2015. Airgun operations would take approximately 135 hours in total, and the remainder of the time would be spent in transit and collecting heat-flow measurements and cores. The total distance the Revelle would travel in the region to conduct the proposed research activities ( i.e., seismic survey, bathymetric survey, and transit to heat-flow measurement locations) represents approximately 2,000 km (1,079.9 nmi). Some minor deviation from this schedule is possible, depending on logistics and weather ( e.g., the cruise may depart earlier or be extended due to poor weather; or there could be additional days of airgun operations if collected data are deemed to be of substandard quality). Proposed Specified Geographic Region The proposed project and survey sites are located off the southeast coast of North Island and northeast coast of the South Island, New Zealand in selected regions of the Southwest Pacific Ocean. The proposed survey sites are located between approximately 38.5 to 42.5° South and approximately 174 to 180° East off the east coast of New Zealand, in the EEZ of New Zealand and outside of territorial waters (see Figure 1 of the IHA Application). Water depths in the study area are between approximately 200 to 3,000 m (656.2 to 9,842.5 ft). The proposed low-energy seismic survey would be collected in a total of nine grids of intersecting lines of two sizes (see Figure 1 of the IHA application) at exact locations to be determined in the field during May to June 2015. Figure 1 also illustrates the general bathymetry of the proposed study area. The proposed low-energy seismic survey would be within an area of approximately 1,154 km 2 (336.5 nmi 2 ). This estimate is based on the maximum number of kilometers for the low-energy seismic survey (1,250 km) multiplied by the area ensonified around the planned tracklines (2 x 0.6 km in intermediate water depths and 2 x 0.4 km in deep water depths). The ensonified area is based on the predicted rms radii (m) based on modeling and empirical measurements (assuming 100% use of the two 45 in 3 GI airguns in 100 to 1,000 m or greater than 1,000 m water depths), which was calculated to be 600 m (1,968.5 ft) or 400 m (1,312.3 ft). BILLING CODE 3510-22-P EN20MR15.000 BILLING CODE 3510-22-C Detailed Description of the Proposed Specified Activity In support of a research project put forward by Oregon State University (OSU) and to be funded by NSF, SIO proposes to conduct a low-energy seismic survey in the Southwest Pacific Ocean, East of New Zealand, from May to June 2015. In addition to the low-energy seismic survey, scientific research activities would include conducting a bathymetric profile survey of the seafloor using transducer-based instruments such as a multi-beam echosounder and sub-bottom profiler; and heat-flow measurements from the seafloor using various methods and equipment at three sites off the southeast coast of North Island and northeast coast of South Island, New Zealand. Water depths in the survey area are approximately 200 to 3,000 meters (m) (656.2 to 9,842.5 feet [ft]). The proposed low-energy seismic survey is scheduled to occur for a total of approximately 135 hours over the course of the entire cruise, which would be for approximately 27 operational days in May to June 2015. The proposed low-energy seismic survey would be conducted during the day (from nautical twilight-dawn to nautical twilight-dusk) and night, and for up to approximately 72 hours of continuous operations at a time. The operation hours and survey length would include equipment testing, ramp-up, line changes, and repeat coverage. Some minor deviation from these dates would be possible, depending on logistics and weather. The Principal Investigators are Dr. R. N. Harris and Dr. A. Trehu of the OSU. The proposed surveys would allow the development of a process-based understanding of the thermal structure of the Hikurangi subduction zone, and the expansion of this understanding by using regional observations of gas hydrate-related bottom simulating reflections. To achieve the proposed project's goals, the Principal Investigators propose to collect low-energy, high-resolution multi-channel system profiles, heat-flow measurements, and sediment cores along transects seaward and landward of the Hikurangi deformation front. Heat-flow measurements would be made in well-characterized sites, increasing the number of publicly available heat-flow and thermal conductivity measurements from this continental margin by two orders of magnitude. Seismic survey data would be used to produce sediment structural maps and seismic velocities to achieve the project objectives. Data from sediment cores would detect and estimate the nature and sources of fluid flow through high permeability pathways in the overriding plate and along the subduction thrust; characterize the hydrocarbon and gas hydrate system to assist with estimates of heat flow from Bottom Simulating Reflectors (BSR)s, their role in slope stability, and fluid source; and elucidate the response of microbes involved in carbon cycling to changes in methane flux. The low-energy seismic survey would be collected in a total of 9 grids of intersecting lines of two sizes (see Figure 1 of the IHA application) at exact locations to be determined in the field. The water depths would be very similar to those at the nominal survey locations shown in Figure 1 of the IHA application. The northern and middle sites off the North Island would be the primary study areas, and the southern site off the South Island would be a contingency area that would only be surveyed if time permits. SIO's calculations assume that 7 grids at the primary areas and two grids at the southern site would be surveyed. The total trackline distance of the low-energy seismic survey would be approximately 1,250 km (including the two South Island contingency sites), almost all in water depths greater than 1,000 m. The procedures to be used for the survey would be similar to those used during previous low-energy seismic surveys by SIO and NSF and would use conventional seismic methodology. The proposed survey would involve one source vessel, the Revelle. SIO would deploy a two Sercel Generator Injector (GI) airgun array (each with a discharge volume of 45 in 3 [290.3 cm 3 ], in one string, with a total volume of 90 in 3 [580.6 cm 3 ]) as an energy source, at a tow depth of up to 2 m (6.6 ft) below the surface (more information on the airguns can be found in SIO's IHA application). The airguns in the array would be spaced approximately 8 m (26.2 ft) apart and 21 m (68.9 ft) astern of the vessel. The receiving system would consist of one 600 m (1,968.5 ft) long, 48-channel hydrophone streamer(s) towed behind the vessel. Data acquisition is planned along a series of predetermined lines, almost all (approximately 95%) of which would be in water depths greater than 1,000 m. As the GI airguns are towed along the survey lines, the hydrophone streamer would receive the returning acoustic signals and transfer the data to the onboard processing system. The seismic surveys would be conducted while the heat-flow probe is being recharged. All planned seismic data acquisition activities would be conducted by technicians provided by SIO, with onboard assistance by the scientists who have proposed the study. The vessel would be self-contained, and the crew would live aboard the vessel for the entire cruise. The planned seismic survey (including equipment testing, start-up, line changes, repeat coverage of any areas, and equipment recovery) would consist of approximately 1,250 kilometers (km) (674.9 nautical miles [nmi]) of transect lines (including turns) in the study area in the Southwest Pacific Ocean (see Figures 1 of the IHA application). Approximately 95% of the low-energy seismic survey would occur in water depths greater than 1,000 m. In addition to the operation of the airgun array and heat-flow measurements, a multi-beam echosounder and a sub-bottom profiler would also likely be operated from the Revelle continuously throughout the cruise. There would be additional airgun operations associated with equipment testing, ramp-up, and possible line changes or repeat coverage of any areas where initial data quality is sub-standard. In SIO's estimated take calculations, 25% has been added for those additional operations. Table 1—Proposed Low-Energy Seismic Survey Activities in the Southwest Pacific Ocean, East of New Zealand Survey length (km) Total duration (hr) 1 Airgun array total volume Time between airgun shots (distance) Streamer length (m) 1,250 (674.9 nmi) ~135 2 × 45 = 90 in 3 (2 × 1474.8 cm 3 ) 6 to 10 seconds (18.5 to 31 m or 60.7 to 101.7 ft) 600 (1,968.5 ft) 1 Airgun operations are planned for no more than approximately 72 continuous hours at a time. Vessel Specifications The Revelle, a research vessel owned by the U.S. Navy and operated by SIO of the University of California San Diego, would tow the two GI airgun array, as well as the hydrophone streamer. When the Revelle is towing the airgun array and the relatively short hydrophone streamer, the turning rate of the vessel while the gear is deployed is approximately 20 degrees per minute, which is much higher than the limit of 5 degrees per minute for a seismic vessel towing a streamer of more typical length (much greater than 1 km [0.5 nmi]). Thus, the maneuverability of the vessel would not be limited much during operations with the streamer. The U.S.-flagged vessel, built in 1996, has a length of 83 m (272.3 ft); a beam of 16.0 m (52.5 ft); a maximum draft of 5.2 m (19.5 ft); and a gross tonnage of 3,180. The ship is powered by two 3,000 horsepower (hp) Propulsion General Electric motors) and a 1,180 hp azimuthing jet bowthruster. The GI airgun compressor onboard the vessel is manufactured by Price Air Compressors. The Revelle's operation speed during seismic acquisition is typically approximately 9.3 km/hr (5 kts) (varying between 7.4 to 11.1 km/hr [4 to 6 kts]). When not towing seismic survey gear, the Revelle typically cruises at 22.2 to 23.1 km/hr (12 to 12.5 kts) and has a maximum speed of 27.8 km/hr (15 kts). The Revelle has an operating range of approximately 27,780 km (15,000 nmi) (the distance the vessel can travel without refueling), which is approximately 70 to 75 days. The vessel can accommodate 37 scientists and 22 crew members. The vessel also has two observation station locations from which Protected Species Observers (PSO) would watch for marine mammals before and during the proposed airgun operations on the Revelle. Observing stations would be at the 02 level, with a PSO's eye level approximately 10.4 m (34 ft) above sea level—one forward on the 02 deck commanding a forward-centered, approximately 240° view around the vessel, and one atop the aft hangar, with an aft-centered view that includes the radii around the airguns. The eyes on the bridge watch would be at a height of approximately 15 m (49 ft); PSOs would work on the enclosed bridge and adjoining aft steering station during any inclement weather. More details of the Revelle can be found in the IHA application and online at: https://scripps.ucsd.edu/ships/revelle. Acoustic Source Specifications—Seismic Airguns The Revelle would deploy an airgun array, consisting of two 45 in 3 Sercel GI airguns as the primary energy source and a 600 m streamer(s) containing hydrophones. The airgun array would have a supply firing pressure of 1,750 pounds per square inch (psi). Seismic pulses for the GI airguns would be emitted at intervals of approximately 6 to 10 seconds. There would be a maximum of approximately 360 shots per hour. The number of shots per hour would vary based upon the vessel speed over ground during the low-energy seismic survey. During firing, a brief (approximately 20 millisecond) pulse sound would be emitted; the airguns would be silent during the intervening periods. The dominant frequency components would range from 0 to 188 Hertz (Hz). The GI airguns would fire the compressed air volume in unison in “true GI” mode. The GI airguns would be used in “true GI” mode, that is, the volume of the injector chamber (I) (105 in 3 [1721 cm 3 ]) of each GI airgun is greater to that of its generator chamber (G) (45 in 3 [737 cm 3 ]) for each airgun. The generator chamber of each GI airgun (45 in 3 ) would be the primary source and the one responsible for introducing the sound pulse into the ocean. The larger (105 in 3 ) injector chamber injects air into the previously-generated bubble to maintain its shape, and would not introduce more sound into the water. The two GI airguns would be spaced approximately 8 m (26.2 ft) apart, side-by-side, 21 m (68.9 ft) behind the Revelle, at a depth of up to 2 m during the low-energy seismic survey. The Nucleus modeling software used at Lamont-Doherty Earth Observatory of Columbia University (L-DEO) does not include GI airguns as part of its airgun library, however signatures and mitigation models have been obtained for two 45 in 3 G airguns that are close approximations. For the two 45 in 3 airgun array, the source output (downward) is 230.6 dB re 1 μPam 0-to-peak and 235.8 dB re 1 μPam for peak-to-peak. The dominant frequency range would be 0 to 188 Hz for a pair of GI airguns towed at 2 m depth. During the low-energy seismic survey, the vessel would attempt to maintain a constant cruise speed of approximately 5 knots. The airguns would operate continuously for no more than approximately 72 hours at a time based on operational constraints. The total duration of the airgun operations would not exceed 135 hours. The relatively short, 48-channel hydrophone streamer would provide operational flexibility to allow the low-energy seismic survey to proceed along the designated cruise tracklines. The design of the seismic equipment is to achieve high-resolution images with the ability to correlate to the ultra-high frequency sub-bottom profiling data and provide cross-sectional views to pair with the seafloor bathymetry. Metrics Used in This Document This section includes a brief explanation of the sound measurements frequently used in the discussions of acoustic effects in this document. Sound pressure is the sound force per unit area, and is usually measured in micropascals (μPa), where 1 pascal (Pa) is the pressure resulting from a force of one newton exerted over an area of one square meter. Sound pressure level (SPL) is expressed as the ratio of a measured sound pressure and a reference level. The commonly used reference pressure level in underwater acoustics is 1 μPa, and the units for SPLs are dB re 1 μPa. SPL (in decibels [dB]) = 20 log (pressure/reference pressure). SPL is an instantaneous measurement and can be expressed as the peak, the peak-to-peak (p-p), or the root mean square (rms). Root mean square, which is the square root of the arithmetic average of the squared instantaneous pressure values, is typically used in discussions of the effects of sounds on vertebrates and all references to SPL in this document refer to the root mean square unless otherwise noted. SPL does not take the duration of a sound into account. Characteristics of the Airgun Pulses Airguns function by venting high-pressure air into the water, which creates an air bubble. The pressure signature of an individual airgun consists of a sharp rise and then fall in pressure, followed by several positive and negative pressure excursions caused by the oscillation of the resulting air bubble. The oscillation of the air bubble transmits sounds downward through the seafloor, and the amount of sound transmitted in the near horizontal directions is reduced. However, the airgun array also emits sounds that travel horizontally toward non-target areas. The nominal downward-directed source levels of the airgun arrays used by SIO on the Revelle do not represent actual sound levels that can be measured at any location in the water. Rather, they represent the level that would be found 1 m (3.3 ft) from a hypothetical point source emitting the same total amount of sound as is emitted by the combined GI airguns. The actual received level at any location in the water near the GI airguns would not exceed the source level of the strongest individual source. In this case, that would be about 224.6 dB re 1 µPam peak or 229.8 dB re 1 µPam peak-to-peak for the two 45 in 3 airgun array. However, the difference between rms and peak or peak-to-peak values for a given pulse depends on the frequency content and duration of the pulse, among other factors. Actual levels experienced by any organism more than 1 m from either GI airgun would be significantly lower. Accordingly, L-DEO has predicted and modeled the received sound levels in relation to distance and direction from the two GI airgun array. These are the nominal source levels applicable to downward propagation. A detailed description of L-DEO's modeling for this survey's marine seismic source arrays for protected species mitigation is provided in the “Programmatic Environmental Impact Statement/Overseas Environmental Impact Statement prepared for Marine Seismic Research that is funded by the National Science Foundation and conducted by the U.S. Geological Survey” (NSF/USGS PEIS, 2011). The NSF/USGS PEIS discusses the characteristics of the airgun pulses. NMFS refers the reviewers to that document for additional information. Predicted Sound Levels for the Airguns To estimate takes and determine mitigation ( i.e., buffer and exclusion) zones for the airgun array to be used, received sound levels have been modeled by L-DEO for a number of airgun configurations, including two 45 in 3 G airguns, in relation to distance and direction from the airguns (see Figure 2 of the IHA application). The model does not allow for bottom interactions, and is most directly applicable to deep water. Because the model results are for G airguns, which have more energy than GI airguns of the same size, those distances overestimate (by approximately 10%) the distances for the two 45 in 3 GI airguns. Although the distances are overestimated, no adjustments for this have been made to the radii distances in Table 2 (below). Based on the modeling, estimates of the maximum distances from the GI airguns where sound levels of 190, 180, and 160 dB re 1 µPa (rms) are predicted to be received in intermediate and deep water are shown in Table 2 (see Table 1 of the IHA application). Empirical data concerning the 190, 180, and 160 dB (rms) distances were acquired for various airgun arrays based on measurements during the acoustic verification studies conducted by L-DEO in the northern Gulf of Mexico (GOM) in 2003 (Tolstoy et al., 2004) and 2007 to 2008 (Tolstoy et al., 2009; Diebold et al., 2010). Results of the 18 and 36 airgun array are not relevant for the two GI airguns to be used in the proposed low-energy seismic survey because the airgun arrays are not the same size or volume. The empirical data for the 6, 10, 12, and 20 airgun arrays indicate that, for deep water, the L-DEO model tends to overestimate the received sound levels at a given distance (Tolstoy et al., 2004). For the two G airgun array, measurements were obtained only in shallow water. When compared to measurements in acquired in deep water, mitigation radii provided by the L-DEO model for the proposed airgun operations were found to be conservative. The acoustic verification surveys also showed that distances to given received levels vary with water depth; these are larger in shallow water, while intermediate/slope environments show characteristics intermediate between those of shallow water and those of deep water environments, and documented the influence of a sloping seafloor. The only measurements obtained for intermediate depths during either survey were for the 36-airgun array in 2007 to 2008 (Diebold et al., 2010). Following results obtained at this site and earlier practice, a correction factor of 1.5, irrespective of distance to the airgun array, is used to derive intermediate-water radii from modeled deep-water radii. Measurements were not made for a two GI airgun array in intermediate and deep water; however, SIO proposes to use the buffer and exclusion zones predicted by L-DEO's model for the proposed GI airgun operations in intermediate and deep water, although they are likely conservative given the empirical results for the other arrays. Using the L-DEO model, Table 2 (below) shows the distances at which three rms sound levels are expected to be received from the two GI airguns. The 160 dB re 1 μPam (rms) isopleth is the threshold specified by NMFS for potential Level B (behavioral) harassment from impulsive noise for both cetaceans and pinnipeds. The 180 and 190 dB re 1 μPam (rms) isopleths are the thresholds currently used to estimate potential Level A harassment as specified by NMFS (2000) and are applicable to cetaceans and pinnipeds, respectively. Table 2 summarizes the predicted distances at which sound levels (160, 180, and 190 dB [rms]) are expected to be received from the two airgun array (each 45 in 3 ) operating in intermediate water (100 to 1,000 m [328.1 to 3,280 ft]) and deep water (>1,000 m) depths. Table 2—Predicted and Modeled (Two 45 in 3 GI Airgun Array) Distances to Which Sound Levels ≥160, 180, and 190 dB re 1 μPa (rms) Could Be Received in Intermediate and Deep Water During the Proposed Low-Energy Seismic Survey in the Southwest Pacific Ocean, East of New Zealand, May to June 2015 Source and total volume Tow depth (m) Water depth (m) Predicted RMS radii distances (m) for 2 GI airgun array 160 dB 180 dB 190 dB Two 45 in 3 GI Airguns (90 in 3 ) 2 Intermediate (100 to 1,000) 600 (1,968.5 ft) 100 (328.1 ft) 15 (49.2 ft) *100 would be used for pinnipeds as described in NSF/USGS PEIS* Two 45 in 3 GI Airguns (90 in 3 ) 2 Deep (>1,000) 400 (1,312.3 ft) 100 (328.1 m) 10 (32.8 ft) *100 would be used for pinnipeds as described in NSF/USGS PEIS* Based on the NSF/USGS PEIS and Record of Decision, for situations which incidental take of marine mammals is anticipated, proposed exclusion zones of 100 m for cetaceans and pinnipeds for all low-energy acoustic sources in water depths greater than 100 m would be implemented. NMFS expects that acoustic stimuli resulting from the proposed operation of the two GI airgun array has the potential to harass marine mammals. NMFS does not expect that the movement of the Revelle, during the conduct of the low-energy seismic survey, has the potential to harass marine mammals because the relatively slow operation speed of the vessel (approximately 5 kts; 9.3 km/hr; 5.8 mph) during seismic data acquisition should allow marine mammals to avoid the vessel. Bathymetric Survey Along with the low-energy airgun operations, two additional geophysical (detailed swath bathymetry) measurements focused on a specific study area within the Southwest Pacific Ocean would be made using hull-mounted sonar system instruments from the Revelle for operational and navigational purposes. The ocean floor would be mapped with the Kongsberg EM 122 multi-beam echosounder and a Knudsen Chirp 3260 sub-bottom profiler. During bathymetric survey operations, when the vessel is not towing seismic equipment, its average speed would be approximately 10.1 kts (18.8 km/hr). In cases where higher resolution bathymetric data is sought, the average speed may be as low as 5 kts (9.3 km/hr). These sound sources would be operated continuously from the Revelle throughout the cruise. Operating characteristics for the instruments to be used are described below. Multi-Beam Echosounder (Kongsberg EM 122)—The hull-mounted multi-beam sonar would be operated continuously during the cruise to map the ocean floor. This instrument would operate at a frequency of 10.5 to 13 (usually 12) kilohertz (kHz) and would be hull-mounted. The transmitting beamwidth would be 1 or 2° fore to aft and 150° athwartship (cross-track). The estimated maximum source energy level would be 242 dB re 1μPa (rms). Each `ping' of eight (in water greater than 1,000 m or four (in water less than 1,000 m) successive fan-shaped transmissions, each ensonifying a sector that extends 1° fore to aft. Continuous-wave signals increase from 2 to 15 milliseconds (ms) in water depths up to 2,600 m (8,530 ft), and FM chirp signals up to 100 ms long would be used in water greater than 2,600 m. The successive transmission span an overall cross-track angular extent of about 150°, with 2 ms gaps between the pings for successive sectors. Sub-Bottom Profiler—The Revelle would operate a Knudsen 3260 sub-bottom profiler continuously throughout the cruise simultaneously to map and provide information about the seafloor sedimentary features and bottom topography that is mapped simultaneously with the multi-beam echosounder. The beam of the sub-bottom profiler would be transmitted as a 27° cone, directed downward by a 3.5 kHz transducer in the hull of the Revelle . The nominal power output would be 10 kilowatt (kW), but the actual maximum radiated power would be 3 kW or 222 dB (rms). The ping duration would be up to 64 ms, and the ping interval would be 1 second. A common mode of operation is a broadcast five pulses at 1 second intervals followed by a 5 second pause. The sub-bottom profiler would be capable of reaching depths of 10,000 m (32,808.4 ft). Acoustic Locator (Pinger)—A pinger would be deployed with certain instruments and equipment ( e.g., heat-flow probe) so these devices can be located in the event they become detached from their lines. The pinger used in the heat-flow measurement activities would be the Datasonics model BFP-312HP. A pinger typically operates at a frequency of 32.8 kHz, generates a 5 ms pulse per second (10 pulses over a 10 second period), and has an acoustical output of 210 dB re 1 μPa (rms). The pinger would be used during heat-flow measurement operations only. It would operate continuously during each heat-flow probe deployment. Each heat-flow probe measurement would last approximately 24 hours. Heat-Flow Probe Deployment Heat-flow measurements would be made using a “violin-bow” probe with 11 thermistors that provides real time (analog) telemetry of the thermal gradient and in-situ thermal conductivity. The heat-flow probe that would be used on the Revelle consists of a lance 6 centimeter (cm) (2.4 in) in diameter and 3.5 m (11.5 ft) long, a sensor tube housing thermistors and heater wires, and a 560 kg (1,234.6 lb) weight stand. The probe would be lowered to the bottom, and a 12 kHz pinger attached to the wire approximately 50 m (164 ft) above the instrument would monitor the distance between the probe and bottom. The probe would be driven into the sediment by gravity, and temperatures within the sediment would be measured with equally spaced thermistors. On completion of a measurement, the instrument would be hoisted 100 to 500 m (328.1 to 1,640.4 ft) above the sediment, the ship is maneuvered to a new position, and the process is repeated. Heat-flow measurements can generally be made at a rate of 1 to 2 hours per measurement, approximately 15 minutes for the actual measurement and 45 to 90 minutes to reposition the ship and probe. Internal power allows 20 to 24 measurements during a single lowering of the tool, with profiles lasting as long as 48 hours. Proposed heat-flow measurements would have a nominal spacing of 0.5 to 1 km (0.3 to 0.5 nmi), which would be decreased in areas of significant basement relief or of large changes in gradient. Heat flow transect locations are shown in Figure 1 of the IHA application, and details of the probe and its deployment are given in Section (f) of the IHA application. In total, approximately 200 heat-flow measurements would be made. Description of the Marine Mammals in the Specified Geographic Area of the Proposed Specified Activity Few scientific systematic surveys for marine mammals have been conducted in the waters of New Zealand, and these mainly consist of single-species surveys in shallow coastal waters ( e.g., Dawson et al., 2004; Slooten et al., 2004, 2006). Large-scale, multi-species marine mammal surveys are lacking. Various sources for data on sightings in the proposed study area were used to describe the occurrence of marine mammals in the waters of New Zealand, such as opportunistic sighting records presented in previous reports (including the New Zealand Department of Conservation marine mammals sighting database) considered in evaluating potential marine mammals in the proposed action area. New Zealand is considered a “hotspot” for marine mammal species richness (Kaschner et al., 2011). The marine mammals that generally occur in the proposed action area belong to three taxonomic groups: Mysticetes (baleen whales), odontocetes (toothed whales), and pinnipeds (seals and sea lions). The marine mammal species that could potentially occur within the Southwest Pacific Ocean in proximity to the proposed action area East of New Zealand include 30 species of cetaceans (21 odontocetes and 9 mysticetes) and 2 species of pinnipeds (32 total species of marine mammals). Marine mammal species likely to be encountered in the proposed study area that are listed as endangered under the U.S. Endangered Species Act of 1973 (ESA; 16 U.S.C. 1531 et seq. ), includes the southern right ( Eubalaena australis ), humpback ( Megaptera novaeangliae ), sei ( Balaenoptera borealis ), fin ( Balaenoptera physalus ), blue ( Balaenoptera musculus ), and sperm ( Physeter macrocephalus ) whale. The Maui's dolphin ( Cephalorhynchus hectori maui ) and New Zealand sea lion ( Phocartos hookeri ) are two other species are ranked as “nationally critical” in New Zealand (Baker et al., 2010). Maui's dolphin is only found along the west coast of the North Island. The northern range of the New Zealand sea lion is not expected to extend to the proposed study area based on New Zealand's National Aquatic Biodiversity Information System (NABIS, 2014) and is not considered further. In addition to the marine mammal species known to occur in the Southwest Pacific Ocean off the east coast of New Zealand, there are 18 species of marine mammals (12 cetacean and 6 pinniped species) with ranges that are known to potentially occur in the waters of the proposed study area, but they are categorized as “vagrant” under the New Zealand Threat Classification System (Baker et al., 2010). These include: Dwarf sperm whale ( Kogia sima ), Arnoux's beaked whale ( Berardius arnouxi ), ginkgo-toothed beaked whale ( Mesoplodon ginkgodens ), pygmy beaked whale ( Mesoplodon peruvianis ), Type B, C, and D killer whale ( Orcinus orca ), melon-headed whale ( Peponocephala electra ), Risso's dolphin ( Grampus griseus ), Fraser's dolphin ( Lagenodelphis hosei ), pantropical spotted dolphin ( Stenella attenuata ), striped dolphin ( Stenella coeruleoalba ), rough-toothed dolphin ( Steno bredanensis ), spectacled porpoise ( Phocoena dioptrica ), Antarctic fur seal ( Arctocephalus gazelle ), Subantarctic fur seal ( Arctocephalus tropicalis ), crabeater seal ( Lobodon carcinophagus ), leopard seal ( Hydrurga leptonyx ), Ross seal ( Ommatophoca rossi ), and Weddell seal ( Leptonychotes weddellii ). According to Jefferson et al. (2008), the distributional range of Hubb's beaked whale ( Mesoplodon carlhubbsi ) and True's beaked whale ( Mesoplodon mirus ) may also include New Zealand waters. There are no records of Hubb's beaked whale in New Zealand, and only a single record of True's beaked whale, which stranded on the west coast of South Island in November 2011 (Constantine et al., 2014). The spinner dolphin's ( Stenella longirostris ) range includes tropical and subtropical zones 40° North to 40° South, but would be considered vagrant as well. However, these species are not expected to occur where the proposed activities would take place. These species are not considered further in this document. Table 3 (below) presents information on the habitat, occurrence, distribution, abundance, population, and conservation status of the species of marine mammals that may occur in the proposed study area during May to June 2015. Table 3—The Habitat, Occurrence, Range, Regional Abundance, and Conservation Status of Marine Mammals That May Occur in or Near the Proposed Low-Energy Seismic Survey Area in the Southwest Pacific Ocean, East of New Zealand [See text and tables 2 in SIO's IHA application for further details] Species Habitat Occurrence Range Population estimate ESA 1 MMPA 2 Mysticetes Southern right whale ( Eubalaena australis ) Coastal, shelf, pelagic Common Circumpolar 20 to 55° South 8,000 3 to 15,000 4 —Worldwide 12,000 12 —Southern Hemisphere 2,700 12 —Sub-Antarctic New Zealand EN D Pygmy right whale ( Caperea marginata ) Pelagic and coastal Rare Circumpolar 30 to 55° South NA NL NC Humpback whale ( Megaptera novaeangliae ) Pelagic, nearshore waters, and banks Common Cosmopolitan Migratory 35,000 to 42,000 3 12 —Southern Hemisphere EN D Minke whale ( Balaenoptera acutorostrata including dwarf sub-species) Pelagic and coastal Uncommon Circumpolar—Southern Hemisphere to 65° South 720,0000 to 750,000 12 14 15 —Southern Hemisphere NL NC Antarctic minke whale ( Balaenoptera bonaerensis ) Pelagic, ice floes, coastal Uncommon 7° South to ice edge (usually 20 to 65° South) 720,000 to 750,000 12 14 15 —Southern Hemisphere NL NC Bryde's whale ( Balaenoptera edeni ) Pelagic and coastal Rare Circumglobal—Tropical and Subtropical Zones At least 30,000 to 40,000 3 —Worldwide 21,000 12 —Northwestern Pacific Ocean 48,109 13 NL NC Sei whale ( Balaenoptera borealis ) Primarily offshore, pelagic Uncommon Migratory, Feeding Concentration 40 to 50° South 80,000 3 —Worldwide 10,000 14 —South of Antarctic Convergence EN D Fin whale ( Balaenoptera physalus ) Continental slope, pelagic Uncommon Cosmopolitan, Migratory 140,000 3 —Worldwide 15,000 14 —South of Antarctic Convergence EN D Blue whale ( Balaenoptera musculus; including pygmy blue whale [ Balaenoptera musculus brevicauda ]) Pelagic, shelf, coastal Uncommon Migratory Pygmy blue whale—North of Antarctic Convergence 55° South 8,000 to 9,000 3 —Worldwide 2,300 12 —True Southern Hemisphere 1,500 14 —Pygmy EN D Odontocetes Sperm whale ( Physeter macrocephalus ) Pelagic, deep sea Common Cosmopolitan, Migratory 360,000 3 —Worldwide 30,000 13 —South of Antarctic Convergence EN D Dwarf sperm whale ( Kogia sima ) Shelf, Pelagic Vagrant Circumglobal—Tropical and Temperate Zones NA NL NC Pygmy sperm whale ( Kogia breviceps ) Shelf, Pelagic Uncommon Circumglobal—Temperate Zones NA NL NC Arnoux's beaked whale ( Berardius arnuxii ) Pelagic Vagrant Circumpolar in Southern Hemisphere, 24 to 78° South NA NL NC Cuvier's beaked whale ( Ziphius cavirostris ) Pelagic Uncommon Cosmopolitan 600,000 14 16 NL NC Southern bottlenose whale ( Hyperoodon planifrons ) Pelagic Rare Circumpolar—30° South to ice edge 500,000 3 —South of Antarctic Convergence 600,000 14 16 NL NC Shepherd's beaked whale ( Tasmacetus shepherdi ) Pelagic Rare Circumpolar—Cold temperate waters Southern Hemisphere 600,000 14 16 NL NC Andrew's beaked whale ( Mesoplodon bowdoini ) Pelagic Rare Circumpolar—temperate waters of Southern Hemisphere, 32 to 55° South 600,000 14 16 NL NC Blainville's beaked whale ( Mesoplodon densirostris ) Pelagic Rare Circumglobal—tropical and temperate waters 600,000 14 16 NL NC Ginkgo-toothed beaked whale ( Mesoplodon ginkgodens ) Pelagic Vagrant Tropical and Temperate waters—Indo-Pacific Ocean NA NL NC Gray's beaked whale ( Mesoplodon grayi ) Pelagic Common 30° South to Antarctic waters 600,000 14 16 NL NC Hector's beaked whale ( Mesoplodon hectori ) Pelagic Rare Circumpolar—cool temperate waters of Southern Hemisphere 600,000 14 16 NL NC Hubb's beaked whale ( Mesoplodon carlhubbsi ) Pelagic Vagrant North Pacific Ocean NA NL NC Pygmy beaked whale ( Mesoplodon peruvianis ) Pelagic Vagrant 28° North to 30° South in Pacific Ocean NA NL NC Spade-toothed beaked whale ( Mesoplodon traversii ) Pelagic Rare Circumantarctic 600,000 14 16 NL NC Strap-toothed beaked whale ( Mesoplodon layardii ) Pelagic Uncommon 30° South to Antarctic Convergence 600,000 14 16 NL NC True's beaked whale ( Mesoplodon mirus ) Pelagic Vagrant Anti-tropical in Northern and Southern Hemisphere NA NL NC Killer whale ( Orcinus orca ) Pelagic, shelf, coastal, pack ice Common Cosmopolitan 80,000 3 —South of Antarctic Convergence NL NC False killer whale ( Pseudorca crassidens ) Pelagic, shelf, coastal Uncommon Circumglobal—tropical and warmer temperate water NA NL NC Long-finned pilot whale ( Globicephala melas ) Pelagic, shelf, coastal Common Circumpolar—19 to 68° South in Southern Hemisphere 200,000 3 5 14 —South of Antarctic Convergence NL NC Short-finned pilot whale ( Globicephala macrocephalus ) Pelagic, shelf, coastal Uncommon Circumglobal—50° North to 40° South At least 600,000 3 —Worldwide NL NC Melon-headed whale ( Peponocephala electra ) Pelagic, shelf, coastal Vagrant Circumglocal—40° North to 35° South 45,000 3 —Eastern Tropical Pacific Ocean NL NC Bottlenose dolphin ( Tursiops truncatus ) Coastal, shelf, offshore Common 45° North to 45° South At least 614,000 3 —Worldwide NL, *C NC Dusky dolphin ( Lagenorhynchus obscurus ) Shelf, slope Common Temperate waters—Southern Hemisphere 12,000 to 20,000 17 —New Zealand NL NC Fraser's dolphin ( Lagenodelphis hosei ) Pelagic Vagrant Pantropical—30° North to 30° South 289,000 3 —Eastern Tropical Pacific Ocean NL NC Hector's dolphin ( Cephalorhynchus hectori; including Maui's dolphin subspecies [ C. h. maui ]) Nearshore Rare Shallow coastal waters—New Zealand (Maui's dolpin—west North Island) 7,400 17 C NC Hourglass dolphin ( Lagenorhynchus cruciger ) Pelagic, ice edge Uncommon 33° South to pack ice 144,000 3 to 150,000 14 —South of Antarctic Convergence NL NC Pantropical spotted dolphin ( Stenella attenuata ) Coastal, shelf, slope Vagrant Circumglobal—40° North to 40° South At least 2,000,000 3 —Worldwide NL NC Spinner dolphin ( Stenella longirostris ) Mainly nearshore Vagrant Circumglobal—40° North to 40° South At least 1,200,000 3 —Worldwide NL NC Striped dolphin ( Stenella coeruleoalba ) Off continental shelf, convergence zones, upwelling Vagrant Circumglobal—50 to 40 South At least 1,100,000 3 —Worldwide NL NC Risso's dolphin ( Grampus griseus ) Slope, Pelagic Vagrant Circumglobal—Tropical and Temperate waters At least 330,000 3 —Worldwide NL NC Rough-toothed dolphin ( Steno bredanensis ) Pelagic Vagrant Circumglobal—40° North to 35° South NA NL NC Short-beaked common dolphin ( Delphinus delphis ) Pelagic Common Circumglobal—tropical and warm temperate waters At least 3,500,000 3 —Worldwide NL NC Southern right whale dolphin ( Lissodelphis peronii ) Pelagic Uncommon 12 to 65° South NA NL NC Spectacled porpoise ( Phocoena dioptrica ) Coastal, pelagic Vagrant Circumpolar—Southern Hemisphere NA NL NC Pinnipeds Crabeater seal ( Lobodon carcinophaga ) Coastal, pack ice Vagrant Circumpolar—Antarctic 5,000,000 to 15,000,000 3 6 —Worldwide NL NC Leopard seal ( Hydrurga leptonyx ) Pack ice, sub-Antarctic islands Vagrant Sub-Antarctic islands to pack ice 220,000 to 440,000 3 7 —Worldwide NL NC Ross seal ( Ommatophoca rossii ) Pack ice, smooth ice floes, pelagic Vagrant Circumpolar—Antarctic 130,000 3 20,000 to 220,000 11 —Worldwide NL NC Weddell seal ( Leptonychotes weddellii ) Fast ice, pack ice, sub-Antarctic islands Vagrant Circumpolar—Southern Hemisphere 500,000 to 1,000,000 3 8 —Worldwide NL NC Southern elephant seal ( Mirounga leonina ) Coastal, pelagic, sub-Antarctic waters Uncommon Circumpolar—Antarctic Convergence to pack ice 640,000 9 to 650,000 3 —Worldwide 470,000—South Georgia Island 11 607,000 17 NL NC Antarctic fur seal ( Arctocephalus gazella ) Shelf, rocky habitats Vagrant Sub-Antarctic islands to pack ice edge 1,600,000 10 to 3,000,000 3 —Worldwide NL NC New Zealand fur seal ( Arctocephalus forsteri ) Rocky habitats, sub-Antarctic islands Common North and South Islands, New Zealand Southern and Western Australia 135,000 3 —Worldwide 50,000 to 100,000 18 —New Zealand NL NC Subantarctic fur seal ( Arctocephalus tropicalis ) Shelf, rocky habitats Vagrant Subtropical front to sub-Antarctic islands and Antarctica Greater than 310,000 3 —Worldwide NL NC New Zealand sea lion ( Phocarctos hookeri ) Shelf, rocky habitats Rare Sub-Antarctic islands south of New Zealand 12,500 3 NL NC NA = Not available or not assessed. * Fjordland population. 1 U.S. Endangered Species Act: EN = Endangered, T = Threatened, DL = Delisted, NL = Not listed, C = Candidate. 2 U.S. Marine Mammal Protection Act: D = Depleted, S = Strategic, NC = Not Classified. 3 Jefferson et al., 2008. 4 Kenney, 2009. 5 Olson, 2009. 6 Bengston, 2009. 7 Rogers, 2009. 8 Thomas and Terhune, 2009. 9 Hindell and Perrin, 2009. 10 Arnould, 2009. 11 Academic Press, 2009. 12 IWC, 2014. 13 IWC, 1981. 14 Boyd, 2002. 15 Dwarf and Antarctic minke whale combined. 16 All Antarctic beaked whales combined. 17 New Zealand Department of Conservation. 18 Suisted and Neale, 2004. Refer to sections 3 and 4 of SIO's IHA application for detailed information regarding the abundance and distribution, population status, and life history and behavior of these marine mammal species and their occurrence in the proposed action area. The IHA application also presents how SIO calculated the estimated densities for the marine mammals in the proposed study area. NMFS has reviewed these data and determined them to be the best available scientific information for the purposes of the proposed IHA. Potential Effects of the Proposed Specified Activity on Marine Mammals This section includes a summary and discussion of the ways that the types of stressors associated with the specified activity ( e.g., seismic airgun operation, vessel movement, and gear deployment) have been thought to impact marine mammals. This discussion may also include reactions that we consider to rise to the level of a take and those that we do not consider to rise to the level of take (for example, with acoustics, we may include a discussion of studies that showed animals not reacting at all to sound or exhibiting barely measureable avoidance). This section is intended as a background of potential effects and does not consider either the specific manner in which this activity would be carried out or the mitigation that would be implemented, and how either of those would shape the anticipated impacts from this specific activity. The “Estimated Take by Incidental Harassment” section later in this document would include a quantitative analysis of the number of individuals that are expected to be taken by this activity. The “Negligible Impact Analysis” section will include the analysis of how this specific activity will impact marine mammals and will consider the content of this section, the “Estimated Take by Incidental Harassment” section, the “Proposed Mitigation” section, and the “Anticipated Effects on Marine Mammal Habitat” section to draw conclusions regarding the likely impacts of this activity on the reproductive success or survivorship of individuals and from that on the affected marine mammal populations or stocks. When considering the influence of various kinds of sound on the marine environment, it is necessary to understand that different kinds of marine life are sensitive to different frequencies of sound. Based on available behavioral data, audiograms have been derived using auditory evoked potentials, anatomical modeling, and other data, Southall et al. (2007) designate “functional hearing groups” for marine mammals and estimate the lower and upper frequencies of functional hearing of the groups. The functional groups and the associated frequencies are indicated below (though animals are less sensitive to sounds at the outer edge of their functional range and most sensitive to sounds of frequencies within a smaller range somewhere in the middle of their functional hearing range): • Low-frequency cetaceans (13 species of mysticetes): Functional hearing is estimated to occur between approximately 7 Hz and 30 kHz; • Mid-frequency cetaceans (32 species of dolphins, six species of larger toothed whales, and 19 species of beaked and bottlenose whales): Functional hearing is estimated to occur between approximately 150 Hz and 160 kHz; • High-frequency cetaceans (eight species of true porpoises, six species of river dolphins, Kogia spp., the franciscana [ Pontoporia blainvillei ], and four species of cephalorhynchids): Functional hearing is estimated to occur between approximately 200 Hz and 180 kHz; and • Phocid pinnipeds in water: Functional hearing is estimated to occur between approximately 75 Hz and 100 kHz; • Otariid pinnipeds in water: Functional hearing is estimated to occur between approximately 100 Hz and 40 kHz. As mentioned previously in this document, 32 marine mammal species (30 cetacean and 2 pinniped species) are likely to occur in the proposed low-energy seismic survey area. Of the 30 cetacean species likely to occur in SIO's proposed action area, 9 are classified as low-frequency cetaceans (southern right, pygmy right, humpback, minke, Antarctic minke, Bryde's, sei, fin, and blue whale), 20 are classified as mid-frequency cetaceans (sperm, Cuvier's beaked, Shepherd's beaked, southern bottlenose, Andrew's beaked, Blainville's beaked, Gray's beaked, Hector's beaked, spade-toothed beaked, strap-toothed beaked, killer, false killer, long-finned pilot, and short-finned pilot whale, and bottlenose, dusky, Hector's, hourglass, short-beaked common, and southern right whale dolphin), and 1 is classified as high-frequency cetaceans (pygmy sperm whale) (Southall et al., 2007). Of the 2 pinniped species likely to occur in SIO's proposed action area, 1 is classified as phocid (southern elephant seal) and 1 is classified as otariid (New Zealand fur seal) (Southall et al., 2007). A species functional hearing group is a consideration when we analyze the effects of exposure to sound on marine mammals. Acoustic stimuli generated by the operation of the airguns, which introduce sound into the marine environment, have the potential to cause Level B harassment of marine mammals in the proposed study area. The effects of sounds from airgun operations might include one or more of the following: Tolerance, masking of natural sounds, behavioral disturbance, temporary or permanent hearing impairment, or non-auditory physical or physiological effects (Richardson et al., 1995; Gordon et al., 2004; Nowacek et al., 2007; Southall et al., 2007). Permanent hearing impairment, in the unlikely event that it occurred, would constitute injury, but temporary threshold shift (TTS) is not an injury (Southall et al., 2007; Le Prell, 2012). Although the possibility cannot be entirely excluded, it is unlikely that the proposed project would result in any cases of temporary or permanent hearing impairment, or any significant non-auditory physical or physiological effects. Based on the available data and studies described here, some behavioral disturbance is expected. A more comprehensive review of these issues can be found in the NSF/USGS PEIS (2011) and L-DEO's “Final Environmental Assessment of a Marine Geophysical Survey by the R/V Marcus G. Langseth in the Atlantic Ocean off Cape Hatteras, September to October 2014.” Tolerance Richardson et al. (1995) defines tolerance as the occurrence of marine mammals in areas where they are exposed to human activities or man-made noise. In many cases, tolerance develops by the animal habituating to the stimulus ( i.e., the gradual waning of responses to a repeated or ongoing stimulus) (Richardson et al., 1995; Thorpe, 1963), but because of ecological or physiological requirements, many marine animals may need to remain in areas where they are exposed to chronic stimuli (Richardson et al., 1995). Numerous studies have shown that pulsed sounds from airguns are often readily detectable in the water at distances of many kilometers (Nieukirk et al., 2012). Several studies have shown that marine mammals at distances more than a few kilometers from operating seismic vessels often show no apparent response. That is often true even in cases when the pulsed sounds must be readily audible to the animals based on measured received levels and the hearing sensitivity of the marine mammal group. Although various baleen whales and toothed whales, and (less frequently) pinnipeds have been shown to react behaviorally to airgun pulses under some conditions, at other times marine mammals of all three types have shown no overt reactions. The relative responsiveness of baleen and toothed whales are quite variable. Masking The term masking refers to the inability of a subject to recognize the occurrence of an acoustic stimulus as a result of the interference of another acoustic stimulus (Clark et al., 2009). Introduced underwater sound may, through masking, reduce the effective communication distance of a marine mammal species if the frequency of the source is close to that used as a signal by the marine mammal, and if the anthropogenic sound is present for a significant fraction of the time (Richardson et al., 1995). The airguns for the proposed low-energy seismic survey have dominant frequency components of 0 to 188 Hz. This frequency range fully overlaps the lower part of the frequency range of odontocete calls and/or functional hearing (full range about 150 Hz to 180 kHz). Airguns also produce a small portion of their sound at mid and high frequencies that overlap most, if not all, frequencies produced by odontocetes. While it is assumed that mysticetes can detect acoustic impulses from airguns and vessel sounds (Richardson et al., 1995a), sub-bottom profilers, and most of the multi-beam echosounders would likely be detectable by some mysticetes based on presumed mysticete hearing sensitivity. Odontocetes are presumably more sensitive to mid to high frequencies produced by the multi-beam echosounders and sub-bottom profilers than to the dominant low frequencies produced by the airguns and vessel. A more comprehensive review of the relevant background information for odontocetes appears in Section 3.6.4.3, Section 3.7.4.3 and Appendix E of the NSF/USGS PEIS (2011). Masking effects of pulsed sounds (even from large arrays of airguns) on marine mammal calls and other natural sounds are expected to be limited. Because of the intermittent nature and low duty cycle of seismic airgun pulses, animals can emit and receive sounds in the relatively quiet intervals between pulses. However, in some situations, reverberation occurs for much or the entire interval between pulses ( e.g., Simard et al., 2005; Clark and Gagnon, 2006) which could mask calls. Situations with prolonged strong reverberation are infrequent. However, it is common for reverberation to cause some lesser degree of elevation of the background level between airgun pulses (Gedamke, 2011; Guerra et al., 2011, 2013), and this weaker reverberation presumably reduces the detection range of calls and other natural sound to some degree. Guerra et al. (2013) reported that ambient noise levels between seismic pulses were elevated because of reverberation at ranges of 50 km (27 nmi) from the seismic source. Based on measurements in deep water of the Southern Ocean, Gedamke (2011) estimated that the slight elevation of background levels during intervals between pulses reduced blue and fin whale communication space by as much as 36 to 51% when a seismic survey was operating 450 to 2,800 km (243 to 1,511.9 nmi) away. Based on preliminary modeling, Wittekind et al. (2013) reported that airgun sounds could reduce the communication range of blue and fin whales 2,000 km (1,079.9 nmi) from the seismic source. Klinck et al. (2012) also found reverberation effects between pulses. Nieukirk et al. (2012) and Blackwell et al. (2013) noted the potential for masking effects from seismic surveys on large whales. Some baleen and toothed whales are known to continue calling in the presence of seismic pulses, and their calls can usually be heard between the seismic pulses ( e.g., Richardson et al., 1986; McDonald et al., 1995; Greene et al., 1999; Nieukirk et al., 2004, 2012; Smultea et al., 2004; Holst et al., 2005a,b, 2006; and Dunn and Hernandez, 2009). However, Clark and Gagnon (2006) reported that fin whales in the North Atlantic Ocean went silent for an extended period starting soon after the onset of a seismic survey in the area. Similarly, there has been one report that sperm whales ceased calling when exposed to pulses from a very distant seismic ship (Bowles et al., 1994). However, more recent studies found that they continued calling in the presence of seismic pulses (Madsen et al., 2002; Tyack et al., 2003; Smultea et al., 2004; Holst et al., 2006; and Jochens et al., 2008). Cerchio et al. (2014) suggested that the breeding display of humpback whales off Angola could have been disrupted by seismic sounds, as singing activity declined with increasing received levels. In addition, some cetaceans are known to change their calling rates, shift their peak frequencies, or otherwise modify their vocal behavior in response to airgun sounds (Di Iorio and Clark, 2010; Castellote et al., 2012; Blackwell et al., 2013). Di Iorio and Clark (2009) found evidence of increased calling by blue whales during operations by a lower-energy seismic source ( i.e., sparker). The hearing systems of baleen whales are undoubtedly more sensitive to low-frequency sounds than are the ears of small odontocetes that have been studied directly (MacGillivary et al., 2013). Dolphins and porpoises commonly are heard calling while airguns are operating ( e.g., Gordon et al., 2004; Smultea et al., 2004; Holst et al., 2005a, b; and Potter et al., 2007). The sounds important to small odontocetes are predominantly at much higher frequencies than are the dominant components of airgun sounds, thus limiting the potential for masking. Pinnipeds have the most sensitive hearing and/or produce most of their sounds in frequencies higher than the dominant components of airgun sound, but there is some overlap in the frequencies of the airgun pulses and the calls. However, the intermittent nature of airgun pules presumably reduces the potential for masking. Marine mammals are thought to be able to compensate for masking by adjusting their acoustic behavior through shifting call frequencies, increasing call volume, and increasing vocalization rates. For example blue whales are found to increase call rates when exposed to noise from seismic surveys in the St. Lawrence Estuary (Di Iorio and Clark, 2009). The North Atlantic right whales ( Eubalaena glacialis ) exposed to high shipping noise increased call frequency (Parks et al., 2007), while some humpback whales respond to low-frequency active sonar playbacks by increasing song length (Miller et al., 2000). In general, NMFS expects the masking effects of seismic pulses to be minor, given the normally intermittent nature of seismic pulses. Behavioral Disturbance Marine mammals may behaviorally react to sound when exposed to anthropogenic noise. Disturbance includes a variety of effects, including subtle to conspicuous changes in behavior, movement, and displacement. Reactions to sound, if any, depend on species, state of maturity, experience, current activity, reproductive state, time of day, and many other factors (Richardson et al., 1995; Wartzok et al., 2004; Southall et al., 2007; Weilgart, 2007; Ellison et al., 2012). These behavioral reactions are often shown as: Changing durations of surfacing and dives, number of blows per surfacing, or moving direction and/or speed; reduced/increased vocal activities; changing/cessation of certain behavioral activities (such as socializing or feeding); visible startle response or aggressive behavior (such as tail/fluke slapping or jaw clapping); avoidance of areas where noise sources are located; and/or flight responses ( e.g., pinnipeds flushing into the water from haul-outs or rookeries). If a marine mammal does react briefly to an underwater sound by changing its behavior or moving a small distance, the impacts of the change are unlikely to be significant to the individual, let alone the stock or population (New et al., 2013). However, if a sound source displaces marine mammals from an important feeding or breeding area for a prolonged period, impacts on individuals and populations could be significant ( e.g., Lusseau and Bejder, 2007; Weilgart, 2007). The biological significance of many of these behavioral disturbances is difficult to predict, especially if the detected disturbances appear minor. However, the consequences of behavioral modification could be expected to be biologically significant if the change affects growth, survival, and/or reproduction. Some of these significant behavioral modifications include: • Change in diving/surfacing patterns (such as those thought to be causing beaked whale stranding due to exposure to military mid-frequency tactical sonar); • Habitat abandonment due to loss of desirable acoustic environment; and • Cessation of feeding or social interaction. The onset of behavioral disturbance from anthropogenic noise depends on both external factors (characteristics of noise sources and their paths) and the receiving animals (hearing, motivation, experience, demography) and is also difficult to predict (Richardson et al., 1995; Southall et al., 2007). Given the many uncertainties in predicting the quantity and types of impacts of noise on marine mammals, it is common practice to estimate how many mammals would be present within a particular distance of industrial activities and/or exposed to a particular level of sound. In most cases, this approach likely overestimates the numbers of marine mammals that would be affected in some biologically-important manner. Baleen Whales —Baleen whales generally tend to avoid operating airguns, but avoidance radii are quite variable (reviewed in Richardson et al., 1995; Gordon et al., 2004). Whales are often reported to show no overt reactions to pulses from large arrays of airguns at distances beyond a few kilometers, even though the airgun pulses remain well above ambient noise levels out to much longer distances. However, baleen whales exposed to strong noise pulses from airguns often react by deviating from their normal migration route and/or interrupting their feeding and moving away. In the cases of migrating gray ( Eschrichtius robustus ) and bowhead ( Balaena mysticetus ) whales, the observed changes in behavior appeared to be of little or no biological consequence to the animals (Richardson et al., 1995). They simply avoided the sound source by displacing their migration route to varying degrees, but within the natural boundaries of the migration corridors (Malme et al., 1984; Malme and Miles, 1985; Richardson et al., 1995). Studies of gray, bowhead, and humpback whales have shown that seismic pulses with received levels of 160 to 170 dB re 1 μPa (rms) seem to cause obvious avoidance behavior in a substantial fraction of the animals exposed (Malme et al., 1986, 1988; Richardson et al., 1995). In many areas, seismic pulses from large arrays of airguns diminish to those levels at distances ranging from 4 to 15 km (2.2 to 8.1 nmi) from the source. A substantial proportion of the baleen whales within those distances may show avoidance or other strong behavioral reactions to the airgun array. Subtle behavioral changes sometimes become evident at somewhat lower received levels, and studies have shown that some species of baleen whales, notably bowhead, gray, and humpback whales, at times, show strong avoidance at received levels lower than 160 to 170 dB re 1 μPa (rms). Researchers have studied the responses of humpback whales to seismic surveys during migration, feeding during the summer months, breeding while offshore from Angola, and wintering offshore from Brazil. McCauley et al. (1998, 2000a) studied the responses of humpback whales off western Australia to a full-scale seismic survey with a 16 airgun array (2,678 in 3 ) and to a single airgun (20 in 3 ) with source level of 227 dB re 1 μPa (p-p). In the 1998 study, they documented that avoidance reactions began at 5 to 8 km (2.7 to 4.3 nmi) from the array, and that those reactions kept most pods approximately 3 to 4 km (1.6 to 2.2 nmi) from the operating seismic boat. In the 2000 study, they noted localized displacement during migration of 4 to 5 km (2.2 to 2.7 nmi) by traveling pods and 7 to 12 km (3.8 to 6.5 nmi) by more sensitive resting pods of cow-calf pairs. Avoidance distances with respect to the single airgun were smaller but consistent with the results from the full array in terms of the received sound levels. The mean received level for initial avoidance of an approaching airgun was 140 dB re 1 μPa (rms) for humpback pods containing females, and at the mean closest point of approach distance the received level was 143 dB re 1 μPa (rms). The initial avoidance response generally occurred at distances of 5 to 8 km (2.7 to 4.3 nmi) from the airgun array and 2 km (1.1 nmi) from the single airgun. However, some individual humpback whales, especially males, approached within distances of 100 to 400 m (328 to 1,312 ft), where the maximum received level was 179 dB re 1 μPa (rms). Studies examining the behavioral responses of humpback whales to airguns are currently underway off eastern Australia (Cato et al., 2011, 2012, 2013). Data collected by observers during several seismic surveys in the Northwest Atlantic showed that sighting rates of humpback whales were significantly greater during non-seismic periods compared with periods when a full array was operating (Moulton and Holst, 2010). In addition, humpback whales were more likely to swim away and less likely to swim towards a vessel during seismic vs. non-seismic periods (Moulton and Holst, 2010). Humpback whales on their summer feeding grounds in southeast Alaska did not exhibit persistent avoidance when exposed to seismic pulses from a 1.64-L (100 in 3 ) airgun (Malme et al., 1985). Some humpbacks seemed “startled” at received levels of 150 to 169 dB re 1 μPa. Malme et al. (1985) concluded that there was no clear evidence of avoidance, despite the possibility of subtle effects, at received levels up to 172 dB re 1 μPa (rms). However, Moulton and Holst (2010) reported that humpback whales monitored during seismic surveys in the Northwest Atlantic had lower sighting rates and were most often seen swimming away from the vessel during seismic periods compared with periods when airguns were silent. Studies have suggested that South Atlantic humpback whales wintering off Brazil may be displaced or even strand upon exposure to seismic surveys (Engel et al., 2004). The evidence for this was circumstantial and subject to alternative explanations (IAGC, 2004). Also, the evidence was not consistent with subsequent results from the same area of Brazil (Parente et al., 2006), or with direct studies of humpbacks exposed to seismic surveys in other areas and seasons. After allowance for data from subsequent years, there was “no observable direct correlation” between strandings and seismic surveys (IWC, 2007: 236). There are no reactions of right whales to seismic surveys. However, Rolland et al. (2012) suggested that ship noise causes increased stress in right whales; they showed that baseline levels of stress-related fecal hormone metabolites decreased in North Atlantic right whales with a 6 dB decrease in underwater noise from vessels. Wright et al. (2011) also reported that sound could be a potential source of stress for marine mammals. Results from bowhead whales show that their responsiveness can be quite variable depending on their activity (migrating versus feeding). Bowhead whales migrating west across the Alaskan Beaufort Sea in autumn, in particular, are unusually responsive, with substantial avoidance occurring out to distances of 20 to 30 km (10.8 to 16.2 nmi) from a medium-sized airgun source (Miller et al., 1999; Richardson et al., 1999). However, more recent research on bowhead whales corroborates earlier evidence that, during the summer feeding season, bowheads are not as sensitive to seismic sources (Miller et al., 2005). Nonetheless, Robertson et al. (2013) showed that bowheads on their summer feeding grounds showed subtle but statistically significant changes in surfacing-respiration-dive cycles during exposure to seismic sounds, including shorter surfacing intervals, shorter dives, and decreased number of blows per surface interval. Bowhead whale calls detected in the presence and absence of airgun sounds have been studied extensively in the Beaufort Sea. Bowheads continue to produce calls of the usual types when exposed to airgun sounds on their summering grounds, although number of calls detected are significantly lower in the presence than in the absence of airgun pulses; Blackwell et al. (2013) reported that calling rates in 2007 declined significantly where received SPLs from airgun sounds were 116 to 129 dB re 1 μPa. Thus, bowhead whales in the Beaufort Sea apparently decrease their calling rates in response to seismic operations, although movement out of the area could also contribute to the lower call detection rate (Blackwell et al., 2013). A multivariate analysis of factors affecting the distribution of calling bowhead whales during their fall migration in 2009 noted that the southern edge of the distribution of calling whales was significantly closer to shore with increasing levels of airgun sound from a seismic survey a few hundred kms to the east of the study area ( i.e., behind the westward-migrating whales; McDonald et al., 2010, 2011). It was not known whether this statistical effect represented a stronger tendency for quieting of the whales farther offshore in deeper water upon exposure to airgun sound, or an actual inshore displacement of whales. Reactions of migrating and feeding (but not wintering) gray whales to seismic surveys have been studied. Malme et al. (1986, 1988) studied the responses of feeding eastern Pacific gray whales to pulses from a single 100 in 3 airgun off St. Lawrence Island in the northern Bering Sea. They estimated, based on small sample sizes, that 50 percent of feeding gray whales stopped feeding at an average received pressure level of 173 dB re 1 μPa on an (approximate) rms basis, and that 10 percent of feeding whales interrupted feeding at received levels of 163 dB re 1 μPa (rms). Those findings were generally consistent with the results of experiments conducted on larger numbers of gray whales that were migrating along the California coast (Malme et al., 1984; Malme and Miles, 1985), and western Pacific gray whales feeding off Sakhalin Island, Russia (Wursig et al., 1999; Gailey et al., 2007; Johnson et al., 2007; Yazvenko et al., 2007a, b), along with data on gray whales off British Columbia (Bain and Williams, 2006). Various species of Balaenoptera (blue, sei, fin, and minke whales) have occasionally been seen in areas ensonified by airgun pulses (Stone, 2003; MacLean and Haley, 2004; Stone and Tasker, 2006), and calls from blue and fin whales have been localized in areas with airgun operations ( e.g., McDonald et al., 1995; Dunn and Hernandez, 2009; Castellote et al., 2010). Sightings by observers on seismic vessels off the United Kingdom from 1997 to 2000 suggest that, during times of good sightability, sighting rates for mysticetes (mainly fin and sei whales) were similar when large arrays of airguns were shooting versus silent (Stone, 2003; Stone and Tasker, 2006). However, these whales tended to exhibit localized avoidance, remaining significantly further (on average) from the airgun array during seismic operations compared with non-seismic periods (Stone and Tasker, 2006). Castellote et al. (2010, 2012) reported that singing fin whales in the Mediterranean moved away from an operating airgun array, and their song notes had low bandwidths during periods with versus without airgun sounds. Ship-based monitoring studies of baleen whales (including blue, fin, sei, minke, and humpback whales) in the Northwest Atlantic found that overall, this group had lower sighting rates during seismic vs. non-seismic periods (Moulton and Holst, 2010). Baleen whales as a group were also seen significantly farther from the vessel during seismic compared with non-seismic periods, and they were more often seen to be swimming away from the operating seismic vessel (Moulton and Holst, 2010). Blue and minke whales were initially sighted significantly farther from the vessel during seismic operations compared to non-seismic periods; the same trend was observed for fin whales (Moulton and Holst, 2010). Minke whales were most often observed to be swimming away from the vessel when seismic operations were underway (Moulton and Holst, 2010). Data on short-term reactions by cetaceans to impulsive noises are not necessarily indicative of long-term or biologically significant effects. It is not known whether impulsive sounds affect reproductive rate or distribution and habitat use in subsequent days or years. However, gray whales have continued to migrate annually along the west coast of North America with substantial increases in the population over recent years, despite intermittent seismic exploration (and much ship traffic) in that area for decades (Appendix A in Malme et al., 1984; Richardson et al., 1995; Allen and Angliss, 2010). The western Pacific gray whale population did not seem affected by a seismic survey in its feeding ground during a previous year (Johnson et al., 2007). Similarly, bowhead whales have continued to travel to the eastern Beaufort Sea each summer, and their numbers have increased notably, despite seismic exploration in their summer and autumn range for many years (Richardson et al., 1987; Allen and Angliss, 2010). Toothed Whales —Little systematic information is available about reactions of toothed whales to noise pulses. Few studies similar to the more extensive baleen whale/seismic pulse work summarized above have been reported for toothed whales. However, there are recent systematic studies on sperm whales ( e.g., Gordon et al., 2006; Madsen et al., 2006; Winsor and Mate, 2006; Jochens et al., 2008; Miller et al., 2009). There is an increasing amount of information about responses of various odontocetes to seismic surveys based on monitoring studies ( e.g., Stone, 2003; Smultea et al., 2004; Moulton and Miller, 2005; Bain and Williams, 2006; Holst et al., 2006; Stone and Tasker, 2006; Potter et al., 2007; Hauser et al., 2008; Holst and Smultea, 2008; Weir, 2008; Barkaszi et al., 2009; Richardson et al., 2009; Moulton and Holst, 2010). Seismic operators and PSOs on seismic vessels regularly see dolphins and other small toothed whales near operating airgun arrays, but in general there is a tendency for most delphinids to show some avoidance of operating seismic vessels ( e.g., Goold, 1996a,b,c; Calambokidis and Osmek, 1998; Stone, 2003; Moulton and Miller, 2005; Holst et al., 2006; Stone and Tasker, 2006; Weir, 2008; Richardson et al., 2009; Barkaszi et al., 2009; Moulton and Holst, 2010; Barry et al., 2012). Some dolphins seem to be attracted to the seismic vessel and floats, and some ride the bow wave of the seismic vessel even when large arrays of airguns are firing ( e.g., Moulton and Miller, 2005). Nonetheless, small toothed whales more often tend to head away, or to maintain a somewhat greater distance from the vessel, when a large array of airguns is operating than when it is silent ( e.g., Stone and Tasker, 2006; Weir, 2008; Barry et al., 2010; Moulton and Holst, 2010). In most cases, the avoidance radii for delphinids appear to be small, on the order of one km or less, and some individuals show no apparent avoidance. Captive bottlenose dolphins ( Tursiops truncatus ) and beluga whales ( Delphinapterus leucas ) exhibited changes in behavior when exposed to strong pulsed sounds similar in duration to those typically used in seismic surveys (Finneran et al., 2000, 2002, 2005). However, the animals tolerated high received levels of sound before exhibiting aversive behaviors. Preliminary findings of a monitoring study of narwhals ( Monodon monoceros ) in Melville Bay, Greenland (summer and fall 2012) showed no short-term effects of seismic survey activity on narwhal distribution, abundance, migration timing, and feeding habits (Heide-Jorgensen et al., 2013a). In addition, there were no reported effects on narwhal hunting. These findings do not seemingly support a suggestion by Heide-Jorgensen et al. (2013b) that seismic surveys in Baffin Bay may have delayed the migration timing of narwhals, thereby increasing the risk of narwhals to ice entrapment. Results of porpoises depend on species. The limited available data suggest that harbor porpoises ( Phocoena phocoena ) show stronger avoidance of seismic operations than do Dall's porpoises ( Phocoenoides dalli ) (Stone, 2003; MacLean and Koski, 2005; Bain and Williams, 2006; Stone and Tasker, 2006). Thompson et al. (2013) reported decreased densities and reduced acoustic detections of harbor porpoise in response to a seismic survey in Moray Firth, Scotland, at ranges of 5 to 10 km (2.7 to 5.4 nmi) (SPLs of 165 to 172 dB re 1 μPa; sound exposure levels (SELs) of 145 to 151 dB μPa 2 s); however, animals returned to the area within a few hours. Dall's porpoises seem relatively tolerant of airgun operations (MacLean and Koski, 2005; Bain and Williams, 2006), although they too have been observed to avoid large arrays of operating airguns (Calambokidis and Osmek, 1998; Bain and Williams, 2006). This apparent difference in responsiveness of these two porpoise species is consistent with their relative responsiveness to boat traffic and some other acoustic sources (Richardson et al., 1995; Southall et al., 2007). Most studies of sperm whales exposed to airgun sounds indicate that the sperm whale shows considerable tolerance of airgun pulses ( e.g., Stone, 2003; Moulton et al., 2005, 2006a; Stone and Tasker, 2006; Weir, 2008). In most cases the whales do not show strong avoidance, and they continue to call. However, controlled exposure experiments in the Gulf of Mexico indicate that foraging behavior was altered upon exposure to airgun sound (Jochens et al., 2008; Miller et al., 2009; Tyack, 2009). There are almost no specific data on the behavioral reactions of beaked whales to seismic surveys. However, some northern bottlenose whales ( Hyperoodon ampullatus ) remained in the general area and continued to produce high-frequency clicks when exposed to sound pulses from distant seismic surveys (Gosselin and Lawson, 2004; Laurinolli and Cochrane, 2005; Simard et al., 2005). Most beaked whales tend to avoid approaching vessels of other types ( e.g., Wursig et al., 1998). They may also dive for an extended period when approached by a vessel ( e.g., Kasuya, 1986), although it is uncertain how much longer such dives may be as compared to dives by undisturbed beaked whales, which also are often quite long (Baird et al., 2006; Tyack et al., 2006). Based on a single observation, Aguilar-Soto et al. (2006) suggested that foraging efficiency of Cuvier's beaked whales may be reduced by close approach of vessels. In any event, it is likely that most beaked whales would also show strong avoidance of an approaching seismic vessel, although this has not been documented explicitly. In fact, Moulton and Holst (2010) reported 15 sightings of beaked whales during seismic studies in the Northwest Atlantic; seven of those sightings were made at times when at least one airgun was operating. There was little evidence to indicate that beaked whale behavior was affected by airgun operations; sighting rates and distances were similar during seismic and non-seismic periods (Moulton and Holst, 2010). There are increasing indications that some beaked whales tend to strand when naval exercises involving mid-frequency sonar operation are ongoing nearby ( e.g., Simmonds and Lopez-Jurado, 1991; Frantzis, 1998; NOAA and USN, 2001; Jepson et al., 2003; Hildebrand, 2005; Barlow and Gisiner, 2006; see also the “Stranding and Mortality” section in this notice). These strandings are apparently a disturbance response, although auditory or other injuries or other physiological effects may also be involved. Whether beaked whales would ever react similarly to seismic surveys is unknown. Seismic survey sounds are quite different from those of the sonar in operation during the above-cited incidents. Odontocete reactions to large arrays of airguns are variable and, at least for delphinids, seem to be confined to a smaller radius than has been observed for the more responsive of some mysticetes. However, other data suggest that some odontocete species, including harbor porpoises, may be more responsive than might be expected given their poor low-frequency hearing. Reactions at longer distances may be particularly likely when sound propagation conditions are conducive to transmission of the higher frequency components of airgun sound to the animals' location (DeRuiter et al., 2006; Goold and Coates, 2006; Tyack et al., 2006; Potter et al., 2007). Pinnipeds —Pinnipeds are not likely to show a strong avoidance reaction to the airgun array. Visual monitoring from seismic vessels has shown only slight (if any) avoidance of airguns by pinnipeds, and only slight (if any) changes in behavior. In the Beaufort Sea, some ringed seals avoided an area of 100 m to (at most) a few hundred meters around seismic vessels, but many seals remained within 100 to 200 m (328 to 656 ft) of the trackline as the operating airgun array passed by ( e.g., Harris et al., 2001; Moulton and Lawson, 2002; Miller et al., 2005.). Ringed seal ( Pusa hispida ) sightings averaged somewhat farther away from the seismic vessel when the airguns were operating than when they were not, but the difference was small (Moulton and Lawson, 2002). Similarly, in Puget Sound, sighting distances for harbor seals ( Phoca vitulina ) and California sea lions ( Zalophus californianus ) tended to be larger when airguns were operating (Calambokidis and Osmek, 1998). Previous telemetry work suggests that avoidance and other behavioral reactions by two other species of seals to small airgun sources may be stronger than evident to date from visual studies of pinnipeds reactions to airguns (Thompson et al., 1998). During seismic exploration off Nova Scotia, gray seals ( Halichoerus grypus ) exposed to noise from airguns and linear explosive charges did not react strongly (J. Parsons in Greene et al., 1985). Pinnipeds in both water and air, sometimes tolerate strong noise pulses from non-explosive and explosive scaring devices, especially if attracted to the area for feeding and reproduction (Mate and Harvey, 1987; Reeves et al., 1996). Thus pinnipeds are expected to be rather tolerant of, or habituate to, repeated underwater sounds from distant seismic sources, at least when the animals are strongly attracted to the area. Hearing Impairment and Other Physical Effects Exposure to high intensity sound for a sufficient duration may result in auditory effects such as a noise-induced threshold shift—an increase in the auditory threshold after exposure to noise (Finneran, Carder, Schlundt, and Ridgway, 2005). Factors that influence the amount of threshold shift include the amplitude, duration, frequency content, temporal pattern, and energy distribution of noise exposure. The magnitude of hearing threshold shift normally decreases over time following cessation of the noise exposure. The amount of threshold shift just after exposure is called the initial threshold shift. If the threshold shift eventually returns to zero ( i.e., the threshold returns to the pre-exposure value), it is called temporary threshold shift (TTS) (Southall et al., 2007). Researchers have studied TTS in certain captive odontocetes and pinnipeds exposed to strong sounds (reviewed in Southall et al., 2007). However, there has been no specific documentation of TTS, let alone permanent hearing damage, i.e., permanent threshold shift (PTS), in free-ranging marine mammals exposed to sequences of airgun pulses during realistic field conditions. Temporary Threshold Shift —TTS is the mildest form of hearing impairment that can occur during exposure to a strong sound (Kryter, 1985). While experiencing TTS, the hearing threshold rises and a sound must be stronger in order to be heard. At least in terrestrial mammals, TTS can last from minutes or hours to (in cases of strong TTS) days. For sound exposures at or somewhat above the TTS threshold, hearing sensitivity in both terrestrial and marine mammals recovers rapidly after exposure to the noise ends. Few data on sound levels and durations necessary to elicit mild TTS have been obtained for marine mammals, and none of the published data concern TTS elicited by exposure to multiple pulses of sound. Available data on TTS in marine mammals are summarized in Southall et al. (2007). Table 2 (above) presents the estimated distances from the Revelle' s airguns at which the received energy level (per pulse, flat-weighted) would be expected to be greater than or equal to 180 and 190 dB re 1 μPa (rms). The established 180 and 190 dB (rms) criteria are not considered to be the levels above which TTS might occur. Rather, they are the received levels above which, in the view of a panel of bioacoustics specialists convened by NMFS before TTS measurements for marine mammals started to become available, one could not be certain that there would be no injurious effects, auditory or otherwise, to marine mammals. NMFS also assumes that cetaceans and pinnipeds exposed to levels exceeding 160 dB re 1 μPa (rms) may experience Level B harassment. For toothed whales, researchers have derived TTS information for odontocetes from studies on the bottlenose dolphin and beluga. The experiments show that exposure to a single impulse at a received level of 207 kPa (or 30 psi, peak-to-peak), which is equivalent to 228 dB re 1 Pa (peak-to-peak), resulted in a 7 and 6 dB TTS in the beluga whale at 0.4 and 30 kHz, respectively. Thresholds returned to within 2 dB of the pre-exposure level within 4 minutes of the exposure (Finneran et al., 2002). For the one harbor porpoise tested, the received level of airgun sound that elicited onset of TTS was lower (Lucke et al., 2009). If these results from a single animal are representative, it is inappropriate to assume that onset of TTS occurs at similar received levels in all odontocetes ( cf. Southall et al., 2007). Some cetaceans apparently can incur TTS at considerably lower sound exposures than are necessary to elicit TTS in the beluga or bottlenose dolphin. For baleen whales, there are no data, direct or indirect, on levels or properties of sound that are required to induce TTS. The frequencies to which baleen whales are most sensitive are assumed to be lower than those to which odontocetes are most sensitive, and natural background noise levels at those low frequencies tend to be higher. As a result, auditory thresholds of baleen whales within their frequency band of best hearing are believed to be higher (less sensitive) than are those of odontocetes at their best frequencies (Clark and Ellison, 2004). From this, it is suspected that received levels causing TTS onset may also be higher in baleen whales than those of odontocetes (Southall et al., 2007). In pinnipeds, researchers have not measured TTS thresholds associated with exposure to brief pulses (single or multiple) of underwater sound. Initial evidence from more prolonged (non-pulse) exposures suggested that some pinnipeds (harbor seals in particular) incur TTS at somewhat lower received levels than do small odontocetes exposed for similar durations (Kastak et al., 1999, 2005; Ketten et al., 2001). The TTS threshold for pulsed sounds has been indirectly estimated as being an SEL of approximately 171 dB re 1 μPa 2 ·s (Southall et al., 2007) which would be equivalent to a single pulse with a received level of approximately 181 to 186 dB re 1 μPa (rms), or a series of pulses for which the highest rms values are a few dB lower. Corresponding values for California sea lions and northern elephant seals ( Mirounga angustirostris ) are likely to be higher (Kastak et al., 2005). Additional data are needed to determine the received levels at which small odontocetes would start to incur TTS upon exposure to repeated, low-frequency pulses of airgun sounds with variable received levels. To determine how close an airgun array would need to approach in order to elicit TTS, one would (as a minimum) need to allow for the sequence of distances at which airgun pulses would occur, and for the dependence of received SEL on distance in the region of the airgun operation (Breitzke and Bohlen, 2010; Laws, 2012). At the present state of knowledge, it can be assumed that the effect is directly related to total receive energy, although there is recent evidence that auditory effects in a given animal are not a simple function of received acoustic energy. Frequency, duration of the exposure and occurrence of gaps within the exposure can also influence the auditory effect (Finneran and Schlundt, 2010, 2011, 2013; Finneran et al., 2010a,b; Finneran 2012; Ketten, 2012; Kastelein et al., 2013a). The assumption that, in marine mammals, the occurrence and magnitude of TTS is a function of cumulative acoustic energy (SEL) is probably an oversimplification (Finneran, 2012). Popov et al. (2011) examined the effects of fatiguing noise on the hearing threshold of Yangtze finless porpoises ( Neophocaena phocaenoides ) when exposed to frequencies of 32 to 128 kHz at 140 to 160 dB re 1 μPa for 1 to 30 minutes. They found that an exposure of higher level and shorter duration produced a higher TTS than an exposure of equal SEL but of lower level and longer duration. Kastelein et al. (2012a,b; 2013b) also reported that the equal-energy model is not valid for predicting TTS in harbor porpoises or harbor seals. Recent data have shown that the SEL required for TTS onset to occur increases with intermittent exposures, with some auditory recovery during silent periods between (Finneran et al., 2010b; Finneran and Schlundt, 2011). Schlundt et al. (2013) reported that the potential for seismic surveys using airguns to cause auditory effects on dolphins could be lower than previously thought. Based on behavioral tests, Finneran et al. (2011) and Schlundt et al. (2013) reported no measurable TTS in bottlenose dolphins after exposure to 10 impulses from a seismic airgun with a cumulative SEL of approximately 195 dB re 1 μPa 2 s; results from auditory evoked potential measurements were more variable (Schlundt et al., 2013). Recent studies have also shown that the SEL necessary to elicit TTS can depend substantially on frequency, with susceptibility to TTS increasing with increasing frequency above 3 kHz (Finneran and Schlundt, 2010, 2011; Finneran, 2012). When beluga whales were exposed to fatiguing noise with sound levels of 165 dB re 1 μPa for durations of 1 to 30 minutes at frequencies of 11.2 to 90 kHz, the highest TTS with the longest recovery time was produced by lower frequencies (11.2 and 22.5 kHz); TTS effects also gradually increased with prolonged exposure time (Popov et al., 2013a). Popov et al. (2013b) also reported that TTS produced by exposure to a fatiguing noise was larger during the first session (or naïve subject state) with a beluga whale than TTS that resulted from the same sound in subsequent sessions (experienced subject state). Therefore, Supin et al. (2013) reported that SEL may not be a valid metric for examining fatiguing sounds on beluga whales. Similarly, Nachtigall and Supin (2013) reported that false killer whales are able to change their hearing sensation levels when exposed to loud sounds, such as warning signals or echolocation sounds. It is inappropriate to assume that onset of TTS occurs at similar received levels in all cetaceans (Southall et al., 2007). Some cetaceans could incur TTS at lower sound exposures than are necessary to elicit TTS in the beluga or bottlenose dolphin. Based on the best available information, Southall et al. (2007) recommended a TTS threshold for exposure to a single or multiple pulses of 183 dB re 1 μPa 2 s. Tougaard et al. (2013) proposed a TTS criterion of 165 dB re 1 μPa 2 s for porpoises based on data from two recent studies. Gedamke et al. (2011), based on preliminary simulation modeling that attempted to allow for various uncertainties in assumptions and variability around population means, suggested that some baleen whales whose closest point of approach to a seismic vessel is 1 km or more could experience TTS. Permanent Threshold Shift —When PTS occurs, there is physical damage to the sound receptors in the ear. In severe cases, there can be total or partial deafness, whereas in other cases, the animal has an impaired ability to hear sounds in specific frequency ranges (Kryter, 1985). There is no specific evidence that exposure to pulses of airgun sound can cause PTS in any marine mammal, even with large arrays of airguns. However, given the possibility that mammals close to an airgun array might incur at least mild TTS, there has been further speculation about the possibility that some individuals occurring very close to airguns might incur PTS ( e.g., Richardson et al., 1995, p. 372 ff; Gedamke et al., 2008). Single or occasional occurrences of mild TTS are not indicative of permanent auditory damage, but repeated or (in some cases) single exposures to a level well above that causing TTS onset might elicit PTS. Relationships between TTS and PTS thresholds have not been studied in marine mammals but are assumed to be similar to those in humans and other terrestrial mammals (Southall et al., 2007). PTS might occur at a received sound level at least several dBs above that inducing mild TTS if the animal were exposed to strong sound pulses with rapid rise times. Based on data from terrestrial mammals, a precautionary assumption is that the PTS threshold for impulse sounds (such as airgun pulses as received close to the source) is at least 6 dB higher than the TTS threshold on a peak-pressure basis, and probably greater than 6 dB (Southall et al., 2007). Given the higher level of sound necessary to cause PTS as compared with TTS, it is considerably less likely that PTS would occur. Baleen whales generally avoid the immediate area around operating seismic vessels, as do some other marine mammals. Non-auditory Physiological Effects —Non-auditory physiological effects or injuries that theoretically might occur in marine mammals exposed to strong underwater sound include stress, neurological effects, bubble formation, resonance, and other types of organ or tissue damage (Cox et al., 2006; Southall et al., 2007). Studies examining such effects are limited. However, resonance effects (Gentry, 2002) and direct noise-induced bubble formations (Crum et al., 2005) are implausible in the case of exposure to an impulsive broadband source like an airgun array. If seismic surveys disrupt diving patterns of deep-diving species, this might perhaps result in bubble formation and a form of the bends, as speculated to occur in beaked whales exposed to sonar. However, there is no specific evidence of this upon exposure to airgun pulses. In general, very little is known about the potential for seismic survey sounds (or other types of strong 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), or any meaningful quantitative predictions of the numbers (if any) of marine mammals that might be affected in those ways. Marine mammals that show behavioral avoidance of seismic vessels, including most baleen whales, some odontocetes, and some pinnipeds, are especially unlikely to incur non-auditory physical effects. There is no definitive evidence that any of these effects occur even for marine mammals in close proximity to large airgun arrays. However, Gray and Van Waerebeek (2011) have suggested a cause-effect relationship between a seismic survey off Liberia in 2009 and the erratic movement, postural instability, and akinesia in a pantropical spotted dolphin based on spatially and temporally close association with the airgun array. Additionally, a few cases of strandings in the general area where a seismic survey was ongoing have led to speculation concerning a possible link between seismic surveys and strandings (Castellote and Llorens, 2013). Stranding and Mortality —When a living or dead marine mammal swims or floats onto shore and becomes “beached” or incapable of returning to sea, the event is termed a “stranding” (Geraci et al., 1999; Perrin and Geraci, 2002; Geraci and Lounsbury, 2005; NMFS, 2007). The legal definition for a stranding under the MMPA is that “(A) a marine mammal is dead and is (i) on a beach or shore of the United States; or (ii) in waters under the jurisdiction of the United States (including any navigable waters); or (B) a marine mammal is alive and is (i) on a beach or shore of the United States and is unable to return to the water; (ii) on a beach or shore of the United States and, although able to return to the water is in need of apparent medical attention; or (iii) in the waters under the jurisdiction of the United States (including any navigable waters), but is unable to return to its natural habitat under its own power or without assistance.” Marine mammals are known to strand for a variety of reasons, such as infectious agents, biotoxicosis, starvation, fishery interaction, ship strike, unusual oceanographic or weather events, sound exposure, or combinations of these stressors sustained concurrently or in series. However, the cause or causes of most strandings are unknown (Geraci et al., 1976; Eaton, 1979; Odell et al., 1980; Best, 1982). Numerous studies suggest that the physiology, behavior, habitat relationships, age, or condition of cetaceans may cause them to strand or might pre-dispose them to strand when exposed to another phenomenon. These suggestions are consistent with the conclusions of numerous other studies that have demonstrated that combinations of dissimilar stressors commonly combine to kill an animal or dramatically reduce its fitness, even though one exposure without the other does not produce the same result (Chroussos, 2000; Creel, 2005; DeVries et al., 2003; Fair and Becker, 2000; Foley et al., 2001; Moberg, 2000; Relyea, 2005a, 2005b; Romero, 2004; Sih et al., 2004). Strandings Associated With Military Active Sonar —The proposed action is not a military readiness activity or using military active sonar (non-pulse). Several sources have published lists of mass stranding events of cetaceans in an attempt to identify relationships between those stranding events and military active sonar (Hildebrand, 2004; IWC, 2005; Taylor et al., 2004). For example, based on a review of stranding records between 1960 and 1995, the International Whaling Commission (2005) identified ten mass stranding events and concluded that, out of eight stranding events reported from the mid-1980s to the summer of 2003, seven had been coincident with the use of mid-frequency active sonar and most involved beaked whales. Over the past 12 years, there have been five stranding events coincident with military mid-frequency active sonar use in which exposure to sonar is believed to have been a contributing factor to strandings: Greece (1996); the Bahamas (2000); Madeira (2000); Canary Islands (2002); and Spain (2006). Refer to Cox et al. (2006) for a summary of common features shared by the strandings events in Greece (1996), Bahamas (2000), Madeira (2000), and Canary Islands (2002); and Fernandez et al., (2005) for an additional summary of the Canary Islands 2002 stranding event. Potential for Stranding From Seismic Surveys —Marine mammals close to underwater detonations of high explosives can be killed or severely injured, and the auditory organs are especially susceptible to injury (Ketten et al., 1993; Ketten, 1995). However, explosives are no longer used in marine waters for commercial seismic surveys or (with rare exceptions) for seismic research. These methods have been replaced entirely by airguns or related non-explosive pulse generators. Airgun pulses are less energetic and have slower rise times, and there is no specific evidence that they can cause serious injury, death, or stranding even in the case of large airgun arrays. However, the association of strandings of beaked whales with naval exercises involving mid-frequency active sonar (non-pulse sound) and, in one case, the regional co-occurrence of an L-DEO seismic survey (Malakoff, 2002; Cox et al., 2006), has raised the possibility that beaked whales exposed to strong “pulsed” sounds could also be susceptible to injury and/or behavioral reactions that can lead to stranding ( e.g., Hildebrand, 2005; Southall et al., 2007). Specific sound-related processes that lead to strandings and mortality are not well documented, but may include: (1) Swimming in avoidance of a sound into shallow water; (2) A change in behavior (such as a change in diving behavior) that might contribute to tissue damage, gas bubble formation, hypoxia, cardiac arrhythmia, hypertensive hemorrhage or other forms of trauma; (3) A physiological change such as a vestibular response leading to a behavioral change or stress-induced hemorrhagic diathesis, leading in turn to tissue damage; and (4) Tissue damage directly from sound exposure, such as through acoustically-mediated bubble formation and growth or acoustic resonance of tissues. Some of these mechanisms are unlikely to apply in the case of impulse sounds. However, there are indications that gas-bubble disease (analogous to “the bends”), induced in supersaturated tissue by a behavioral response to acoustic exposure, could be a pathologic mechanism for the strandings and mortality of some deep-diving cetaceans exposed to sonar. The evidence for this remains circumstantial and associated with exposure to naval mid-frequency sonar, not seismic surveys (Cox et al., 2006; Southall et al., 2007). Seismic pulses and mid-frequency sonar signals are quite different, and some mechanisms by which sonar sounds have been hypothesized to affect beaked whales are unlikely to apply to airgun pulses. Sounds produced by airgun arrays are broadband impulses with most of the energy below one kHz. Typical military mid-frequency sonar emits non-impulse sounds at frequencies of 2 to 10 kHz, generally with a relatively narrow bandwidth at any one time. A further difference between seismic surveys and naval exercises is that naval exercises can involve sound sources on more than one vessel. Thus, it is not appropriate to expect that the same effects to marine mammals would result from military sonar and seismic surveys. However, evidence that sonar signals can, in special circumstances, lead (at least indirectly) to physical damage and mortality ( e.g., Balcomb and Claridge, 2001; NOAA and USN, 2001; Jepson et al., 2003; Fernández et al., 2004, 2005; Hildebrand 2005; Cox et al., 2006) suggests that caution is warranted when dealing with exposure of marine mammals to any high-intensity sound. There is no conclusive evidence of cetacean strandings or deaths at sea as a result of exposure to seismic surveys, but a few cases of strandings in the general area where a seismic survey was ongoing have led to speculation concerning a possible link between seismic surveys and strandings. Suggestions that there was a link between seismic surveys and strandings of humpback whales in Brazil (Engel et al., 2004) were not well founded (IAGC, 2004; IWC, 2007). In September 2002, there was a stranding of two Cuvier's beaked whales in the Gulf of California, Mexico, when the L-DEO vessel R/V Maurice Ewing was operating a 20 airgun (8,490 in 3 ) array in the general region. The link between the stranding and the seismic surveys was inconclusive and not based on any physical evidence (Hogarth, 2002; Yoder, 2002). Nonetheless, the Gulf of California incident plus the beaked whale strandings near naval exercises involving use of mid-frequency sonar suggests a need for caution in conducting seismic surveys in areas occupied by beaked whales until more is known about effects of seismic surveys on those species (Hildebrand, 2005). No injuries of beaked whales are anticipated during the proposed study because of: (1) The high likelihood that any beaked whales nearby would avoid the approaching vessel before being exposed to high sound levels, and (2) Differences between the sound sources to be used in the proposed study and operated by SIO and those involved in the naval exercises associated with strandings. Potential Effects of Other Acoustic Devices and Sources Multi-Beam Echosounder SIO would operate the Kongsberg EM 122 multi-beam echosounder from the source vessel during the planned study. Sounds from the multi-beam echosounder are very short pulses, occurring for approximately 2 to 15 ms once every 5 to 20 seconds, depending on water depth. Most of the energy in the sound pulses emitted by the multi-beam echosounder is at frequencies near 12 kHz (10.5 to 13), and the maximum source level is 242 dB re 1 μPa (rms). The beam is narrow (1 to 2°) in fore-aft extent and wide (150°) in the cross-track extent. Each ping consists of eight (in water greater than 1,000 m deep) or four (in water less than 1,000 m) consecutive successive fan-shaped transmissions (segments) at different cross-track angles. Any given marine mammal at depth near the trackline would be in the main beam for only one or two of the eight segments. Also, marine mammals that encounter the Kongsberg EM 122 are unlikely to be subjected to repeated pulses because of the narrow fore-aft width of the beam and would receive only limited amounts of pulse energy because of the short pulses. Animals close to the ship (where the beam is narrowest) are especially unlikely to be ensonified for more than one 2 to 15 ms pulse (or two pulses if in the overlap area). Similarly, Kremser et al. (2005) noted that the probability of a cetacean swimming through the area of exposure when a multi-beam echosounder emits a pulse is small. The animal would have to pass the transducer at close range and be swimming at speeds similar to the vessel in order to receive the multiple pulses that might result in sufficient exposure to cause TTS. Navy sonars that have been linked to avoidance reactions and stranding of cetaceans: (1) Generally have longer pulse duration than the Kongsberg EM 122; and (2) are often directed close to horizontally, as well as omnidirectional, versus more downward and narrowly for the multi-beam echosounder. The area of possible influence of the multi-beam echosounder is much smaller—a narrow band below the source vessel. Also, the duration of exposure for a given marine mammal can be much longer for naval sonar. During SIO's operations, the individual pulses would be very short, and a given mammal would not receive many of the downward-directed pulses as the vessel passes by. Possible effects of a multi-beam echosounder on marine mammals are described below. Stranding —In 2013, an International Scientific Review Panel investigated a 2008 mass stranding of approximately 100 melon-headed whales in a Madagascar lagoon system (Southall et al., 2013) associated with the use of a high-frequency mapping system. The report indicated that the use of a 12 kHz multi-beam echosounder was the most plausible and likely initial behavioral trigger of the mass stranding event. This was the first time that a relatively high-frequency mapping sonar system has been associated with a stranding event. However, the report also notes that there were several site- and situation-specific secondary factors that may have contributed to the avoidance responses that lead to the eventual entrapment and mortality of the whales within the Loza Lagoon system ( e.g., the survey vessel transiting in a north-south direction on the shelf break parallel to the shore may have trapped the animals between the sound source and the shore driving them towards the Loza Lagoon). The report concluded that for odontocete cetaceans that hear well in the 10 to 50 kHz range, 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 (Southall et al., 2013). However, the risk may be very low given the extensive use of these systems worldwide on a daily basis and the lack of direct evidence of such responses previously (Southall et al., 2013). It is noted that leading scientific experts on multi-beam echosounders have expressed concerns about the independent scientific review panel analyses and findings (Bernstein, 2013). Masking —Marine mammal communications would not be masked appreciably by the multi-beam echosounder signals, given the low duty cycle of the echosounder and the brief period when an individual mammal is likely to be within its beam. Furthermore, in the case of baleen whales, the multi-beam echosounder signals (12 kHz) generally do not overlap with the predominant frequencies in the calls (16 Hz to less than 12 kHz), which would avoid any significant masking (Richardson et al., 1995). Behavioral Responses —Behavioral reactions of free-ranging marine mammals to sonars, echosounders, and other sound sources appear to vary by species and circumstance. Observed reactions have included silencing and dispersal by sperm whales (Watkins et al., 1985), increased vocalizations and no dispersal by pilot whales (Rendell and Gordon, 1999), and the previously-mentioned beachings by beaked whales. During exposure to a 21 to 25 kHz “whale-finding” sonar with a source level of 215 dB re 1 μPa, gray whales reacted by orienting slightly away from the source and being deflected from their course by approximately 200 m (656.2 ft) (Frankel, 2005). When a 38 kHz echosounder and a 150 kHz ADCP were transmitting during studies in the Eastern Tropical Pacific, baleen whales showed no significant responses, while spotted and spinner dolphins were detected slightly more often and beaked whales less often during visual surveys (Gerrodette and Pettis, 2005). Captive bottlenose dolphins and a beluga whale exhibited changes in behavior when exposed to 1 second tonal signals at frequencies similar to those that would be emitted by the multi-beam echosounder used by SIO, and to shorter broadband pulsed signals. Behavioral changes typically involved what appeared to be deliberate attempts to avoid the sound exposure (Schlundt et al., 2000; Finneran et al., 2002; Finneran and Schlundt, 2004). The relevance of those data to free-ranging odontocetes is uncertain, and in any case, the test sounds were quite different in duration as compared with those from a multi-beam echosounder. Risch et al. (2012) found a reduction in humpback whale song in the Stellwagen Bank National Marine Sanctuary during Ocean Acoustic Waveguide Remote Sensing (OAWRS) activities that were carried out approximately 200 km (108 nmi) away. The OAWRS used three frequency-modulated pulses centered at frequencies of 415, 734, and 949 Hz with received levels in the sanctuary of 88 to 110 dB re 1 μPa. Deng et al. (2014) measured the spectral properties of pulses transmitted by three 200 kHz echosounders, and found that they generated weaker sounds at frequencies below the center frequency (90 to 130 kHz). These sounds are within the hearing range of some marine mammals, and the authors suggested that they could be strong enough to elicit behavioral responses within close proximity to the sources, although they would be well below potentially harmful levels. Hearing Impairment and Other Physical Effects —Given several stranding events that have been associated with the operation of naval sonar in specific circumstances, there is concern that mid-frequency sonar sounds can cause serious impacts to marine mammals (see above). However, the multi-beam echosounder proposed for use by SIO is quite different than sonar used for Navy operations. Pulse duration of the multi-beam echosounder is very short relative to the naval sonar. Also, at any given location, an individual marine mammal would be in the beam of the multi-beam echosounder for much less time, given the generally downward orientation of the beam and its narrow fore-aft beamwidth; Navy sonar often uses near-horizontally-directed sound and have higher duty cycles. Those factors would all reduce the sound energy received from the multi-beam echosounder rather drastically relative to that from naval sonar. NMFS believes that the brief exposure of marine mammals to one puls [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%3A2015-06261. Public record. Not legal advice.