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Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to a Low-Energy Geophysical Survey in the South Atlantic Ocean

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


Notice; Issuance of an Incidental Harassment Authorization.


In accordance with the regulations implementing the Marine Mammal Protection Act (MMPA) as amended, notification is hereby given that NMFS has issued an incidental harassment authorization (IHA) to the Scripps Institute of Oceanography (SIO) to incidentally harass, by Level B harassment only, marine mammals during a low-energy marine geophysical survey in the South Atlantic Ocean.


This Authorization is applicable from November 3, 2019 through November 2, 2020.

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Stephanie Egger, Office of Protected Resources, NMFS, (301) 427-8401. Electronic copies of the application and supporting documents, as well as a list of the references cited in this document, may be obtained online at:​permit/​incidental-take-authorizations-under-marine-mammal-protection-act. In case of problems accessing these documents, please call the contact listed above.

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The MMPA prohibits the “take” of marine mammals, with certain exceptions. Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) direct the Secretary of Commerce (as delegated to NMFS) to allow, upon request, the incidental, but not intentional, taking of small numbers of marine mammals by U.S. citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region if certain findings are made and either regulations are issued or, if the taking is limited to harassment, a notice of a proposed incidental take authorization may be provided to the public for review.

Authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s) and will not have an unmitigable adverse impact on the availability of the species or stock(s) for taking for subsistence uses (where relevant). Further, NMFS must prescribe the permissible methods of taking and other “means of effecting the least practicable adverse impact” on the affected species or stocks and their habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, and on the availability of such species or stocks for taking for certain subsistence uses (referred to in shorthand as “mitigation”); and requirements pertaining to the mitigation, monitoring and reporting of such takings are set forth.

Summary of Request

On May 15, 2019, NMFS received a request from SIO for an IHA to take marine mammals incidental to conducting a low-energy marine geophysical survey in the South Atlantic Ocean. The application was deemed adequate and complete on August 12, 2019. SIO's request was for take of a small number of 48 species of marine mammals by Level B harassment. Neither SIO nor NMFS expects serious injury or mortality to result from this activity and, therefore, an IHA is appropriate.

Description of Planned Activity

SIO plans to conduct low-energy marine seismic surveys in the South Atlantic Ocean during November-December 2019. The seismic surveys would be conducted to understand the volcanic and tectonic development of Walvis Ridge and Rio Grande Rise in the South Atlantic Ocean. The seismic surveys would be conducted in International Waters with water depths ranging from approximately 500 to 5700 m. The surveys would involve one source vessel, R/V Thomas G. Thompson (Thompson). The Thompson would deploy up to two 45-in 3 GI airguns at a depth of 2-4 m with a maximum total volume of ~90 in 3 along predetermined tracklines. Seismic surveys would occur in five survey areas including Libra Massif in the Southwest Atlantic and Valdivia Bank, Gough, Tristan, and Central survey areas in the Southeast Atlantic.

SIO proposes to conduct low-energy seismic surveys low-energy seismic surveys in five areas in the South Atlantic Ocean. Reconnaissance Surveys are planned for three survey areas (Gough, Tristan, Central) and High Quality Surveys are planned to take place along the planned seismic transect lines in the main survey area (Valdivia Bank) and Libra Massif survey area (Figure 1). However, High-Quality Surveys may be replaced by Reconnaissance Surveys depending on weather conditions and timing (e.g., 10 percent of survey effort at Valdivia Bank is expected to consist of Reconnaissance Surveys). All data acquisition in the Tristan survey area would occur in water >1000 m deep; all other survey areas have effort in intermediate (100-1,000 m) and deep (>1,000 m) water. Most of the survey effort (97 percent) would occur in water >1000 m deep. The planned surveys would be in support of a potential future International Ocean Discovery Program (IODP) project and to improve our understanding of volcanic and tectonic development of oceanic ridges and to enable the selection and analysis of potential future IODP drill sites. To achieve the program's goals, the Principal Investigators propose to collect low-energy, high-resolution multi-channel seismic (MCS) profiles. The planned cruise would consist of digital bathymetric, echosounding, and MCS surveys.Start Printed Page 60060

The highest-quality mode is carried out using a pair of 45-in3 airguns, with airguns spaced 2 m apart at a depth of 2-4 m, with a 400, 800, or 1,600 m hydrophone streamer and with the vessel traveling at to 5 knots (5 kn) to achieve high-quality seismic reflection data. The reconnaissance mode is carried out using either one or two 45-in 3 airguns, with airguns spaced 8 m apart (if 2 are being used) at a water depth of 2-4 m, with a 200 m hydrophone streamer and with the vessel traveling at 8 kn. The receiving system would consist of one hydrophone streamer, 200 to 1,600 m in length, as described below. As the airguns are towed along the survey lines, the hydrophone streamer would receive the returning acoustic signals and transfer the data to the on-board processing system.

In addition to the operations of the airgun array, a hull-mounted multibeam echosounder (MBES) and a sub-bottom profiler (SBP) would also be operated from the Thompson continuously throughout the seismic surveys, but not during transits to and from the project area. All planned data acquisition and sampling activities would be conducted by SIO and UW with on board assistance by the scientists who have planned the project. The vessel would be self-contained, and the crew would live aboard the vessel for the entire cruise.

For additional details on the planned activities, please refer to the notice of the proposed IHA that was published in the Federal Register on September 30, 2019 (84 FR 51886).

Planned mitigation, monitoring, and reporting measures are described in detail later in this document (please see Mitigation and Monitoring and Reporting sections).

Comments and Responses

A notice of NMFS's proposal to issue an IHA to SIO was published in the Federal Register on September 30, 2019 (84 FR 51886). That notice described, in detail, SIO's activity, the marine mammal species that may be affected by the activity, and the anticipated effects on marine mammals. During the 30-day public comment period, NMFS received a comment letter from the Marine Mammal Commission (Commission).

Comment: The Commission recommended the calculated Level A harassment takes should have been added to the authorized Level B harassment takes for the following species: 400 to 404 authorized takes by Level B harassment for both Antarctic and common minke whales; 3,414 to 3,718 authorized takes by Level B harassment for short beaked common dolphin; 17 to 18 authorized takes by Level B harassment for pygmy sperm whales; 12 to 13 authorized takes by Level B harassment for dwarf sperm whales; and 54 to 58 authorized takes by Level B harassment for hourglass dolphins.

Response: NMFS agreed and made those revisions to the authorized takes by Level B harassment. Instances of take by Level A and Level B harassment are independently calculated. The instances of take by Level A harassment are typically subtracted from the take by Level B harassment before being presented in the Estimated Take section to ensure they are not double-counted. Since the likelihood of take by Level A harassment was qualitatively ruled out, the calculated take by Level A harassment were previously deducted, but are now added back in to the authorized take by Level B harassment.

Comment: The Commission noted some minor errors of the monitoring requirements between the preamble and the draft IHA.

Response: NMFS agreed and made those corrections to ensure consistency with this final notice and the IHA.

Comment: The Commission recommended revising the group size for Clymene dolphins from 35 to 122 animals, killer whales from 5 to 8 animals, and false killer whales from 19 to 35 (Di Tullio et al., 2016) and making those appropriate changes to the authorized takes by Level B harassment for those species as their total takes were based on group size.

Response: NMFS agreed that the group sizes for Clymene dolphins, killer whales, and false killer whales from Di Tullio et al., 2016 were more recent that the previous group sizes cited and made those revisions to the authorized takes by Level B harassment.

Comment: In the context of a broader criticism of perceived modeling flaws, the Commission recommended NMFS specify why it believes that sound channels with downward refraction, as well as seafloor refractions, are not likely to occur during SIO's survey and the degree to which both of these parameters would affect the estimation (or underestimation) of Level B harassment zones in deep and intermediate water depths.

Response: The L-DEO approach to the modeling is generally conservative as supported by data collected from calibration and other field data along with modeling results. The L-DEO approach does not rely on incorporating every possible environmental factor in the marine environment and while sound channels with downward refraction or seafloor refractions could potentially occur, NMFS disagrees with the Commission that these features need be explicitly addressed through the model given the conservative approach taken. Published results from Tolstoy (2009), Diebold (2010), and Crone et al. (2014, 2017), along with nearly 20 years of PSO observations from previous NSF-funded seismic surveys in various water depths validate the approach. L-DEO has presented their modeling approach to NMFS and the Commission on several occasions. Given the information presented, numerous discussions, and observations from past NSF-funded seismic surveys that used the L-DEO modeling approach, NMFS remains confident that the methodology used is appropriate and conservatively protects marine mammals.

Comment: The Commission noted tables depicting source levels in both the IHA application and the Federal Register notice contained inadequate information and that the appendices of SIO's IHA application did not contain necessary information. The Commission recommended that NMFS ensure that all source levels, modified source levels, and related adjustment factors are specified and all relevant isopleth figures and user spreadsheet tables are included in all future NSF-funded and -affiliated applications prior to processing them.

Response: NMFS has added clarification on the tables noted by the Commission and provided the Commission the requested information. NMFS will ensure that all applications contain the necessary information required for adequate understanding of the acoustic modeling prior to publishing the notice of proposed IHA.

Comment: The Commission recommended that, instead of using the LDEO modeling described in the IHA application, NMFS require LDEO to re-estimate the Level A and Level B harassment zones and associated takes of marine mammals using (1) both operational (including number/type/spacing of airguns, tow depth, source level/operating pressure, operational volume) and site-specific environmental (including sound speed profiles, bathymetry, and sediment characteristics at a minimum) parameters, (2) a comprehensive source model (i.e., Gundalf Optimizer) and (3) an appropriate sound propagation model (i.e., BELLHOP). Specifically, the Commission reiterates that LDEO should be using the ray-tracing propagation model BELLHOP—which is a free, standard propagation code that readily incorporates all environmental inputs listed herein, rather than the Start Printed Page 60061limited, in-house MATLAB code currently in use, and recommends NMFS specify why it believes that LDEO's modeling approaches provide more accurate, realistic, and appropriate Level A and Level B harassment zones than BELLHOP. The Commission recommends that NMFS (1) specify why it believes that LDEO's model and other `modeling' approaches provide more accurate, realistic, and appropriate Level A and B harassment zones than BELLHOP and (2) explain, if LDEO's model and other `modeling' approaches are considered best available science, why other action proponents that conduct seismic surveys are not implementing similar methods particularly given their simplicity.

Response: We appreciate the Commission's input and direct the reader to our recent response to the same comment, which can be found in the final authorization for similar SIO activities in Argentina (84 FR 54849; October 11, 2019).

Comment: The Commission recommends that, in the next six months, NMFS develop a policy regarding how uncertainty should be incorporated in density estimates that have been extrapolated from other areas and other seasons and specify what adjustments (i.e., CVs, standard deviations, blanket correction factors) should be used for NSF-funded and -affiliated surveys.

Response: NMFS appreciates and thanks the Commission's for its recommendation and will take it under consideration.

Comment: The Commission noted that monitoring and reporting requirements adopted need to be sufficient to provide a reasonably accurate assessment of the manner of taking and the numbers of animals taken incidental to the specified activity. Those assessments should account for all animals in the various survey areas, including those animals directly on the trackline that are not detected and how well animals are detected based on the distance from the observer which is achieved by incorporating g(0) and f(0) values. The Commission recommended that NMFS require SIO to use the Commission's method as described in the Commission's Addendum to its May 1, 2019 letter to better estimate the numbers of marine mammals taken by Level B harassment for the incidental harassment authorization. The Commission stated that all other NSF-affiliated entities and all seismic operators should use this method as well.

Response: We thank the Commission for their recommendation. NMFS is in the process of determining the appropriate method for deriving post-survey estimates of the total number of animals taken by activities such as Scripps' marine geophysical survey.

Comment: The Commission recommended NMFS require SIO to specify in the final monitoring report (1) the number of days the survey occurs and the array is active and (2) the percentage of time and total time the array is active during daylight vs nighttime hours (including dawn and dusk).

Response: NMFS will require SIO to include this information in their final monitoring report.

Comment: The Commission recommended that NMFS refrain from using the renewal process for SIO's authorization based on the complexity of analysis and potential for impacts on marine mammals, and the potential burden on reviewers of reviewing key documents and developing comments quickly. Additionally, the Commission recommends that NMFS use the IHA renewal process sparingly and selectively for activities expected to have the lowest levels of impacts to marine mammals and that require less complex analysis.

Response: We appreciate the Commission's input and direct the reader to our recent response to the same comment, which can be found at 84 FR 52464 (October 2, 2019), pg. 52466. If and when SIO requests a Renewal, we will consider the Commission's comment further and address the concerns specific to this project. We will consider this comment further when and if SIO requests a renewal.

Comment: The Commission noted that the planned surveys are scheduled to three days after the public comment period closes and expressed concern that NMFS did not have adequate time to consider public comments before issuing the IHA. The Commission recommended NMFS more thoroughly review applications, draft Federal Register notices, and draft proposed authorizations prior to submitting any proposed authorizations to the Federal Register, as well as require earlier submission of applications and other documentation to ensure sufficient time to prepare the proposed authorization and consider comments received from the public. In addition, Commission recommends that NMFS require NSF-funded and -affiliated applications and other documentation to be submitted at least eight months in advance of the vessel leaving port so that NMFS has sufficient time to review and provide comments on the adequacy and accuracy of the application, allow action proponents to make necessary revisions or additions to the application, draft its proposed authorization, and consider the comments received from the public.

Response: We appreciate the Commission's input and direct the reader to our recent response to the same comment, which can be found in the final authorization for similar SIO activities in Argentina (84 FR 54849; October 11, 2019).

Changes From Proposed to Final IHA

Minor corrections have been made to the estimated take table (see Table 9). As described in the Comments and Response section, calculated Level A harassment takes were added to Authorized Level B harassment takes (to ensure the correct total takes) for six species. In addition, group sizes were adjusted for three species based on Di Tullio et al. (2016) and therefore changes were made to the authorized take by Level B harassment for those species.

Description of Marine Mammals in the Area of Specified Activities

Section 4 of the application summarize available information regarding status and trends, distribution and habitat preferences, and behavior and life history, of the potentially affected species. Additional information about these species (e.g., physical and behavioral descriptions) may be found on NMFS's website (​find- species).

The populations of marine mammals considered in this document do not occur within the U.S. EEZ and are therefore not assigned to stocks and are not assessed in NMFS' Stock Assessment Reports (SAR). As such, information on potential biological removal (PBR; defined by the MMPA as the maximum number of animals, not including natural mortalities, that may be removed from a marine mammal stock while allowing that stock to reach or maintain its optimum sustainable population) and on annual levels of serious injury and mortality from anthropogenic sources are not available for these marine mammal populations. Abundance estimates for marine mammals in the survey location are lacking; therefore estimates of abundance presented here are based on a variety of proxy sources including International Whaling Commission population estimates (IWC 2019), the U.S. Atlantic SARs (Hayes et al., 2018) for a few dolphin species, and various literature estimates (see IHA application for further detail), as this is considered the best available information on Start Printed Page 60062potential abundance of marine mammals in the area. However, as described above, the marine mammals encountered by the planned survey are not assigned to stocks. All abundance estimate values presented in Table 1 are the most recent available at the time of publication and are available in the 2018 U.S. Atlantic SARs (e.g., Hayes et al. 2018) available online at:​national/​marine-mammal-protection/​marine-mammal-stock-assessments, except where noted otherwise.

Table 1 lists all species with expected potential for occurrence in the Argentine Basin, Southwest Atlantic Ocean, and summarizes information related to the population, including regulatory status under the MMPA and ESA. For taxonomy, we follow Committee on Taxonomy (2018).

Table 1—Marine Mammal Species Potentially Present in the Project Area Expected To Be Affected by the Specified Activities

Common nameScientific nameStock 1ESA/MMPA status; strategic (Y/N) 2AbundancePBRRelative occurrence in project area
Order Cetartiodactyla—Cetacea—Superfamily Mysticeti (baleen whales)
Family Balaenidae
Southern right whaleEubalaena australisn/aE/D; N12,000 3 3,3005N.A.Uncommon.
Family Cetotheriidae
Pygmy right whaleCaperea marginatan/aN.A.N.A.Rare.
Family Balaenopteridae (rorquals)
Blue whaleBalaenoptera musculusn/aE/D; Y2,300 true 4 1,500 pygmy 6N.A.Rare.
Fin whaleBalaenoptera physalusn/aE/D; Y15,000 6N.A.Uncommon.
Sei whaleBalaenoptera borealisn/aE10,000 6N.A.Uncommon.
Common minke whaleBalaenoptera acutorostratan/a515,000 3 6N.A.Common.
Antarctic minke whaleBalaenoptera bonaerensisn/a515,000 3 6N.A.Common.
Humpback whaleMegaptera novaeangliaen/a42,000 3N.A.Rare.
Bryde's whaleBalaenoptera edeni/brydein/a48,109 7N.A.Common.
Superfamily Odontoceti (toothed whales, dolphins, and porpoises)
Family Physeteridae
Sperm whalePhyseter macrocephalusn/aE12,069 10N.A.Uncommon.
Family Kogiidae
Pygmy sperm whaleKogia brevicepsn/aN.A.N.A.Rare.
Dwarf sperm whaleKogia siman/aN.A.N.A.Uncommon.
Family Ziphiidae (beaked whales)
Arnoux's beaked whaleBerardius arnuxiin/a599,300 11N.A.Uncommon.
Cuvier's beaked whaleZiphius cavirostrisn/a599,300 11N.A.Uncommon.
Southern bottlenose whaleHyperoodon planifronsn/a599,300 11N.A.Uncommon.
Shepherd's beaked whaleTasmacetus sheperdin/aN.A.N.A.Uncommon.
Blainville's beaked whaleMesoplodon densirostrisn/aN.A.N.A.Rare.
Gray's beaked whaleMesoplodon grayin/a599,300 11N.A.Uncommon.
Gervais' beaked whaleMesoplodon europaeusn/aN.A.N.A.Rare.
Hector's beaked whaleMesoplodon hectorin/aN.A.N.A.Rare.
True's beaked whaleMesoplodon mirusn/aN.A.N.A.Rare.
Strap-toothed beaked whaleMesoplodon layardiin/a599,300 11N.A.Uncommon.
Andrews' beaked whaleMesoplodon bowdoinin/aN.A.N.A.Rare.
Spade-toothed beaked whaleMesoplodon traversiin/aN.A.N.A.Rare.
Family Delphinidae
Risso's dolphinGrampus griseusn/a18,250 12N.A.Common.
Rough-toothed dolphinSteno bredanensisn/aN.A.N.A.Common.
Common bottlenose dolphinTursiops truncatusn/a77,532 12N.A.Uncommon.
Pantropical spotted dolphinStenella attenuatan/a3,333 12N.A.Common.
Atlantic spotted dolphinStenella frontalisn/a44,715 12N.A.Rare.
Spinner dolphinStenella longirostrisn/aN.A.N.A.Uncommon.
Clymene dolphinStenella clymenen/aN.A.N.A.Rare.
Striped dolphinStenella coeruleoalban/a54,807 12N.A.Uncommon.
Short-beaked common dolphinDelphinus delphisn/a70,184 10N.A.Uncommon.
Fraser's dolphinLagenodelphis hosein/aN.A.N.A.Uncommon.
Dusky dolphinLagenorhynchus obscurusn/a7,252 12N.A.Rare.
Hourglass dolphinLagenorhynchus crucigern/a150,000 6N.A.Rare.
Southern right whale dolphinLissodelphis peroniin/aN.A.N.A.Uncommon.
Killer whaleOrcinus orcan/a25,000 14N.A.Uncommon.
Short-finned pilot whaleGlobicephala macrorhynchusn/a200,000 6N.A.Uncommon.
Long-finned pilot whaleGlobicephala melasn/a200,000 6N.A.Uncommon.
False killer whalePseudorca crassidensn/aN.A.N.A.Uncommon.
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Pygmy killer whaleFeresa attenuatan/aN.A.N.A.Uncommon.
Melon-headed whalePeponocephala electran/aN.A.N.A.Uncommon.
Order Carnivora—Superfamily Pinnipedia
Family Otariidae (eared seals and sea lions)
Cape fur sealArctocephalus pusillus pusillusn/aApproximately 2 million 16N.A.Uncommon.
Subantarctic fur sealArctocephalus tropicalisn/a400,000 15N.A.Uncommon.
Family Phocidae (earless seals)
Crabeater sealLobodon carcinophagan/a5—10 million 17N.A.Rare.
Leopard sealHydrurga leptonyxn/a222,000—440,000 18N.A.Rare.
Southern elephant sealMirounga leoninan/a750,000 19N.A.Uncommon.
N.A. = Data not available. NL = Not listed.
1 U.S. Endangered Species Act (NOAA 2019): EN = Endangered.
2 International Union for the Conservation of Nature (IUCN) Red List of Threatened Species (IUCN 2019): EN = Endangered; NT = Near Threatened; VU = Vulnerable; LC = Least Concern; DD = Data Deficient
3 Convention on International Trade in Endangered Species of Wild Fauna and Flora (UNEP-WCMC 2017): Appendix I = Threatened with extinction; Appendix II = not necessarily threatened with extinction but may become so unless trade is closely controlled.
4 Southern Hemisphere (IWC 2019).
5 Southwest Atlantic (IWC 2019).
6 Antarctic (Boyd 2002).
7 Southern Hemisphere (IWC 1981).
8 Dwarf and Antarctic minke whales combined.
9 There are 14 distinct population segments (DPSs) of humpback whales recognized under the ESA; the Brazil and Gabon/Southwest Africa DPSs are not listed (NOAA 2019).
10 Estimate for the Antarctic, south of 60°S (Whitehead 2002).
11 All beaked whales south of the Antarctic Convergence; mostly southern bottlenose whales (Kasamatsu and Joyce 1995).
12 Estimate for the western North Atlantic (Hayes et al. 2018).
13 Estimate for Patagonian coast (Dans et al. 1997).
14 Minimum estimate for Southern Ocean (Branch and Butterworth 2001).
15 Global population (Hofmeyr and Bester 2018).
16 Butterworth et al. (1995 in Kirkman and Arnould 2018).
17 Global population (Bengtson and Stewart 2018).
18 Global population (Rogers 2018).
19 Total world population (Hindell et al. 2016).

All species that could potentially occur in the planned survey areas are included in Table 1. As described below, all 48 species temporally and spatially co-occur with the activity to the degree that take is reasonably likely to occur, and we have authorized it.

A detailed description of the species likely to be affected by the planned geophysical surveys, including brief introductions to the species and relevant stocks as well as available information regarding population trends and threats, information regarding local occurrence, and marine mammal hearing were provided in the Federal Register notice for the proposed IHA (84 FR 51886; September 30, 2019). Since that time, we are not aware of any changes in the status of these species and stocks; therefore, detailed descriptions are not provided here. Please refer to that Federal Register notice for these descriptions. Please also refer to NMFS's website (​find-species) for generalized species accounts.

Potential Effects of Specified Activities on Marine Mammals and Their Habitat

The effects from underwater noise from SIO's planned geophysical surveys have the potential to result in harassment of marine mammals in the vicinity of the action area. The Federal Register notice for the proposed IHA (84 FR 51886; September 30, 2019) included a discussion of the effects of anthropogenic noise on marine mammals and their habitat, therefore that information is not repeated here; please refer to that Federal Register notice (84 FR 51886; September 30, 2019) for that information. No instances of serious injury or mortality are expected as a result of the planned activities.

Estimated Take

This section provides an estimate of the number of incidental takes authorized through this IHA, which will inform both NMFS' consideration of “small numbers” and the negligible impact determination.

Harassment is the only type of take expected to result from these activities. Except with respect to certain activities not pertinent here, section 3(18) of the MMPA defines “harassment” as any act of pursuit, torment, or annoyance, which (i) has the potential to injure a marine mammal or marine mammal stock in the wild (Level A harassment); or (ii) has the potential to disturb a marine mammal or marine mammal stock in the wild by causing disruption of behavioral patterns, including, but not limited to, migration, breathing, nursing, breeding, feeding, or sheltering (Level B harassment).

Authorized takes would be by Level B harassment only, as use of the acoustic sources (i.e., seismic airgun) has the potential to result in disruption of behavioral patterns for individual marine mammals. Based on the nature of the activity and the anticipated effectiveness of the mitigation measures (i.e., marine mammal exclusion zones) discussed in detail below in Mitigation section, Level A harassment is neither anticipated nor authorized. As described previously, no mortality is anticipated or authorized for this activity. Below we describe how the take is estimated.

Generally speaking, we estimate take by considering: (1) Acoustic thresholds Start Printed Page 60064above which NMFS believes the best available science indicates marine mammals will be behaviorally harassed or incur some degree of permanent hearing impairment; (2) the area or volume of water that will be ensonified above these levels in a day; (3) the density or occurrence of marine mammals within these ensonified areas; and, (4) and the number of days of activities. We note that while these basic factors can contribute to a basic calculation to provide an initial prediction of takes, additional information that can qualitatively inform take estimates is also sometimes available (e.g., previous monitoring results or average group size). Below, we describe the factors considered here in more detail and present the authorized take estimate.

Acoustic Thresholds

Using the best available science, NMFS has developed acoustic thresholds that identify the received level of underwater sound above which exposed marine mammals would be reasonably expected to be behaviorally harassed (equated to Level B harassment) or to incur PTS of some degree (equated to Level A harassment).

Level B Harassment for non-explosive sources—Though significantly driven by received level, the onset of behavioral disturbance from anthropogenic noise exposure is also informed to varying degrees by other factors related to the source (e.g., frequency, predictability, duty cycle), the environment (e.g., bathymetry), and the receiving animals (hearing, motivation, experience, demography, behavioral context) and can be difficult to predict (Southall et al., 2007; Ellison et al., 2012). Based on what the available science indicates, and the practical need to use a threshold based on a factor that is both predictable and measurable for most activities, NMFS uses a generalized acoustic threshold based on received level to estimate the onset of behavioral harassment. NMFS predicts that marine mammals are likely to be behaviorally harassed in a manner we consider Level B harassment when exposed to underwater anthropogenic noise above received levels of 120 dB re 1 μPa (rms) for continuous (e.g., vibratory pile-driving, drilling) and above 160 dB re 1 μPa (rms) for non-explosive impulsive (e.g., seismic airguns) or intermittent (e.g., scientific sonar) sources.

SIO's planned activity includes the use of impulsive seismic sources, and therefore the 160 dB re 1 μPa (rms) is applicable.

Level A harassment for non-explosive sources—NMFS' Technical Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammal Hearing (Version 2.0) (Technical Guidance) (NMFS, 2018) identifies dual criteria to assess auditory injury (Level A harassment) to five different marine mammal groups (based on hearing sensitivity) as a result of exposure to noise from two different types of sources (impulsive or non-impulsive). SIO's planned activity includes the use of impulsive seismic sources.

These thresholds are provided in Table 2 below. The references, analysis, and methodology used in the development of the thresholds are described in NMFS 2018 Technical Guidance, which may be accessed at​national/​marine-mammal-protection/​marine-mammal-acoustic-technical-guidance.

Table 2—Thresholds Identifying the Onset of Permanent Threshold Shift

PTS Onset acoustic thresholds * (received level)
Hearing groupImpulsiveNon-impulsive
Low-Frequency (LF) CetaceansCell 1: L pk,flat : 219 dB; L E , LF,24h : 183 dBCell 2: L E , LF,24h : 199 dB
Mid-Frequency (MF) CetaceansCell 3: L pk,flat : 230 dB L E , MF,24h : 185 dBCell 4: L E , MF,24h : 198 dB
High-Frequency (HF) CetaceansCell 5: L pk,flat : 202 dB L E , HF,24h : 155 dBCell 6: L E , HF,24h : 173 dB
Phocid Pinnipeds (PW) (Underwater)Cell 7: L pk,flat : 218 dB L E , PW,24h : 185 dBCell 8: L E , PW,24h : 201 dB
Otariid Pinnipeds (OW) (Underwater)Cell 9: L pk,flat : 232 dB L E , OW,24h : 203 dBCell 10: L E , OW,24h : 219 dB
* Dual metric acoustic thresholds for impulsive sounds: Use whichever results in the largest isopleth for calculating PTS onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure level thresholds associated with impulsive sounds, these thresholds should also be considered.
Note: Peak sound pressure (L pk) has a reference value of 1 µPa, and cumulative sound exposure level (L E) has a reference value of 1μPa2 s. In this Table, thresholds are abbreviated to reflect American National Standards Institute standards (ANSI 2013). However, peak sound pressure is defined by ANSI as incorporating frequency weighting, which is not the intent for this Technical Guidance. Hence, the subscript “flat” is being included to indicate peak sound pressure should be flat weighted or unweighted within the generalized hearing range. The subscript associated with cumulative sound exposure level thresholds indicates the designated marine mammal auditory weighting function (LF, MF, and HF cetaceans, and PW and OW pinnipeds) and that the recommended accumulation period is 24 hours. The cumulative sound exposure level thresholds could be exceeded in a multitude of ways (i.e., varying exposure levels and durations, duty cycle). When possible, it is valuable for action proponents to indicate the conditions under which these acoustic thresholds will be exceeded.

Ensonified Area

Here, we describe operational and environmental parameters of the activity that will feed into identifying the area ensonified above the acoustic thresholds, which include source levels and transmission loss coefficient.

The planned survey would entail the use of a 2-airgun array with a total discharge of 90 in3 at a two depth of 2-4 m. Lamont-Doherty Earth Observatory (LDEO) model results are used to determine the 160 dBrms radius for the 2-airgun array in deep water (>1,000 m) down to a maximum water depth of 2,000 m. Received sound levels were predicted by LDEO's model (Diebold et al., 2010) as a function of distance from the airguns, for the two 45 in3 airguns. This modeling approach uses ray tracing for the direct wave traveling from the array to the receiver and its associated source ghost (reflection at the air-water interface in the vicinity of the array), in a constant-velocity half-space (infinite homogenous ocean layer, unbounded by a seafloor). In addition, propagation measurements of pulses from a 36-airgun array at a tow depth of 6 m have been reported in deep water (~1,600 m), intermediate water depth on the slope (~600-1,100 m), and shallow water (~50 m) in the Gulf of Mexico in 2007-2008 (Tolstoy et al., 2009; Diebold et al., 2010).

For deep and intermediate water cases, the field measurements cannot be used readily to derive the Level A and Level B harassment isopleths, as at those sites the calibration hydrophone was located at a roughly constant depth of 350-550 m, which may not intersect Start Printed Page 60065all the SPL isopleths at their widest point from the sea surface down to the maximum relevant water depth (~2,000 m) for marine mammals. At short ranges, where the direct arrivals dominate and the effects of seafloor interactions are minimal, the data at the deep sites are suitable for comparison with modeled levels at the depth of the calibration hydrophone. At longer ranges, the comparison with the model—constructed from the maximum SPL through the entire water column at varying distances from the airgun array—is the most relevant.

In deep and intermediate water depths, comparisons at short ranges between sound levels for direct arrivals recorded by the calibration hydrophone and model results for the same array tow depth are in good agreement (see Figures 12 and 14 in Appendix H of NSF-USGS 2011). Consequently, isopleths falling within this domain can be predicted reliably by the LDEO model, although they may be imperfectly sampled by measurements recorded at a single depth. At greater distances, the calibration data show that seafloor-reflected and sub-seafloor-refracted arrivals dominate, whereas the direct arrivals become weak and/or incoherent. Aside from local topography effects, the region around the critical distance is where the observed levels rise closest to the model curve. However, the observed sound levels are found to fall almost entirely below the model curve. Thus, analysis of the Gulf of Mexico calibration measurements demonstrates that although simple, the LDEO model is a robust tool for conservatively estimating isopleths.

The planned surveys would acquire data with two 45-in3 guns at a tow depth of 2-4 m. For deep water (>1,000 m), we use the deep-water radii obtained from LDEO model results down to a maximum water depth of 2,000 m for the airgun array with 2-m and 8-m airgun separation. The radii for intermediate water depths (100-1,000 m) are derived from the deep-water ones by applying a correction factor (multiplication) of 1.5, such that observed levels at very near offsets fall below the corrected mitigation curve (see Figure 16 in Appendix H of NSF-USGS 2011).

LDEO's modeling methodology is described in greater detail in SIO's IHA application. The estimated distances to the Level B harassment isopleths for the two planned airgun configurations in each water depth category are shown in Table 3.

Table 3—Predicted Radial Distances From R/V Thompson Seismic Source to Isopleths Corresponding to Level B Harassment Threshold

Airgun configurationWater depth (m)Predicted distances (m) to 160 dB received sound level
Two 45 in3 guns, 2-m separation>1,000 (deep)a 539
100-1,000 (intermediate)b 809
Two 45 in3 guns, 8-m separation> 1,000 (deep)a 578
100-1,000 (intermediate)b 867
a Distance based on LDEO model results.
b Distance based on LDEO model results with a 1.5 x correction factor between deep and intermediate water depths.
c Distance based on empirically derived measurements in the Gulf of Mexico with scaling applied to account for differences in tow depth.

Predicted distances to Level A harassment isopleths, which vary based on marine mammal hearing groups, were calculated based on modeling performed by LDEO using the NUCLEUS software program and the NMFS User Spreadsheet, described below. The updated acoustic thresholds for impulsive sounds (e.g., airguns) contained in the Technical Guidance were presented as dual metric acoustic thresholds using both SELcum and peak sound pressure metrics (NMFS 2018). As dual metrics, NMFS considers onset of PTS (Level A harassment) to have occurred when either one of the two metrics is exceeded (i.e., metric resulting in the largest isopleth). The SELcum metric considers both level and duration of exposure, as well as auditory weighting functions by marine mammal hearing group. In recognition of the fact that the requirement to calculate Level A harassment ensonified areas could be more technically challenging to predict due to the duration component and the use of weighting functions in the new SELcum thresholds, NMFS developed an optional User Spreadsheet that includes tools to help predict a simple isopleth that can be used in conjunction with marine mammal density or occurrence to facilitate the estimation of take numbers.

The SELcum for the 2-GI airgun array is derived from calculating the modified farfield signature. The farfield signature is often used as a theoretical representation of the source level. To compute the farfield signature, the source level is estimated at a large distance (right) below the array (e.g., 9 km), and this level is back projected mathematically to a notional distance of 1 m from the array's geometrical center. However, it has been recognized that the source level from the theoretical farfield signature is never physically achieved at the source when the source is an array of multiple airguns separated in space (Tolstoy et al., 2009). Near the source (at short ranges, distances <1 km), the pulses of sound pressure from each individual airgun in the source array do not stack constructively as they do for the theoretical farfield signature. The pulses from the different airguns spread out in time such that the source levels observed or modeled are the result of the summation of pulses from a few airguns, not the full array (Tolstoy et al., 2009). At larger distances, away from the source array center, sound pressure of all the airguns in the array stack coherently, but not within one time sample, resulting in smaller source levels (a few dB) than the source level derived from the farfield signature. Because the farfield signature does not take into account the interactions of the two airguns that occur near the source center and is calculated as a point source (single airgun), the modified farfield signature is a more appropriate measure of the sound source level for large arrays. For this smaller array, the modified farfield changes will be correspondingly smaller as well, but we use this method for consistency across all array sizes.

SIO used the same acoustic modeling as Level B harassment with a small grid step in both the inline and depth Start Printed Page 60066directions to estimate the SELcum and peak SPL. The propagation modeling takes into account all airgun interactions at short distances from the source including interactions between subarrays using the NUCLEUS software to estimate the notional signature and the MATLAB software to calculate the pressure signal at each mesh point of a grid. For a more complete explanation of this modeling approach, please see Appendix A: Determination of Mitigation Zones in SIO's IHA application.

Table 4—Modeled Source Levels (dB) for R/V Thompson 90 in3 Airgun Arrays

Functional hearing group8-kn survey with 8-m airgun separation: Peak SPLflat8-kn survey with 8-m airgun separation: SELcum5-kn survey with 2-m airgun separation: Peak SPLflat5-kn survey with 2-m airgun separation: SELcum
Low frequency cetaceans (L pk,flat : 219 dB; L E , LF,24h : 183 dB)228.8207232.8206.7
Mid frequency cetaceans (L pk,flat : 230 dB ; L E , MF,24h : 185 dB)1 N/A206.7229.8206.9
High frequency cetaceans (L pk,flat : 202 dB; L E , HF,24h : 155 dB)233207.6232.9207.2
Phocid Pinnipeds (Underwater) (L pk,flat : 218 dB ; L E , HF,24h : 185 dB)230206.7232.8206.9
Otariid Pinnipeds (Underwater) (L pk,flat : 232 dB ; L E , HF,24h : 203 dB)1 N/A203225.6207.4
1 N/A indicates source level not applicable or not available. There are no values for the 2 x 45 at 4m depth with an 8m separation for the MF cetaceans and Otariids (maximum peak value is 221dB so less than 230 or 232dB). Therefore, we cannot provide any radial distance or modified peak farfield values for these two hearing groups.

In order to more realistically incorporate the Technical Guidance's weighting functions over the seismic array's full acoustic band, unweighted spectrum data for the Thompson's airgun array (modeled in 1 Hz bands) was used to make adjustments (dB) to the unweighted spectrum levels, by frequency, according to the weighting functions for each relevant marine mammal hearing group. These adjusted/weighted spectrum levels were then converted to pressures (μPa) in order to integrate them over the entire broadband spectrum, resulting in broadband weighted source levels by hearing group that could be directly incorporated within the User Spreadsheet (i.e., to override the Spreadsheet's more simple weighting factor adjustment). Using the User Spreadsheet's “safe distance” methodology for mobile sources (described by Sivle et al., 2014) with the hearing group-specific weighted source levels, and inputs assuming spherical spreading propagation and source velocities and shot intervals provided in SIO's IHA application, potential radial distances to auditory injury zones were calculated for SELcum thresholds, for both array configurations.

Inputs to the User Spreadsheet in the form of estimated SLs are shown in Table 4. User Spreadsheets used by SIO to estimate distances to Level A harassment isopleths for the two potential airgun array configurations are shown in Tables A-4 and A-5 in Appendix A of SIO's IHA application. Outputs from the User Spreadsheet in the form of estimated distances to Level A harassment isopleths are shown in Table 5. As described above, NMFS considers onset of PTS (Level A harassment) to have occurred when either one of the dual metrics (SELcum or Peak SPLflat) is exceeded (i.e., metric resulting in the largest isopleth).

Table 5—Modeled Radial Distances to Isopleths Corresponding to Level A Harassment Thresholds

Functional Hearing Group (Level A harassment thresholds)8-kn survey with 8-m airgun separation: Peak SPLflat8-kn survey with 8-m airgun separation: SELcum5-kn survey with 2-m airgun separation: Peak SPLflat5-kn survey with 2-m airgun separation: SELcum
Low frequency cetaceans (L pk,flat : 219 dB ; L E , LF,24h : 183 dB)
Mid frequency cetaceans (L pk,flat : 230 dB ; L E , MF,24h : 185 dB)000.980
High frequency cetaceans (L pk,flat : 202 dB ; L E , HF,24h : 155 dB)34.84034.620
Phocid Pinnipeds (Underwater) (L pk,flat : 218 dB ; L E , HF,24h : 185 dB)4.0205.510.1
Otariid Pinnipeds (Underwater) (L pk,flat : 232 dB ; L E , HF,24h : 203 dB)000.480

Note that because of some of the assumptions included in the methods used, isopleths produced may be overestimates to some degree, which will ultimately result in some degree of overestimate of take by Level A harassment. However, these tools offer the best way to predict appropriate isopleths when more sophisticated 3D modeling methods are not available, and NMFS continues to develop ways to quantitatively refine these tools and will qualitatively address the output where appropriate. For mobile sources, such as the planned seismic survey, the User Spreadsheet predicts the closest distance at which a stationary animal would not incur PTS if the sound source traveled by the animal in a straight line at a constant speed.

Marine Mammal Occurrence

In this section we provide the information about the presence, density, or group dynamics of marine mammals that will inform the take calculations.

SIO determined that the preferred source of density data for marine mammal species that might be encountered in the planned survey areas in the South Atlantic Ocean was Di Tullio et al. (2016). The rationale for using these data was that these surveys were conducted offshore along the continental slope at the same latitudes as the planned seismic surveys and so come from a similar season, water depth category, and climatic region in the southern Atlantic Ocean. When data for species expected to occur in the planned seismic survey areas were not available in Di Tullio et al. (2016), data from White et al. (2002) was used as Start Printed Page 60067calculated in LGL/NSF (2019) because they came from an area which was slightly south of the planned project area but well north of the AECOM/NSF (2014) study area. An exception was made for the southern right whale, for which densities from AECOM/NSF (2014) were higher and thus more conservative. Next data came from AECOM/NSF (2014); although they come from an area south of the planned project area, they were the next best data available for those species. For species not included in these sources stated above, data came from from de Boer (2010), Garaffo et al. (2011), NOAA-SWFSC LOA (2013 in AECOM/NSF 2014), Wedekin et al. (2014), Bradford et al. (2017), and Mannocci et al. (2017). When densities were not directly available from the above studies, they were estimated using sightings and effort reported in those sources. Densities calculated from de Boer (2010) come from LGL/NSF (2016); densities from White et al. (2002), Garaffo et al. (2011), and Wedekin et al. (2014) are from LGL/NSF (2019). Data sources and density calculations are described in detail in Appendix B of SIO's IHA application. For some species, the densities derived from past surveys may not be representative of the densities that would be encountered during the planned seismic surveys. However, the approach used is based on the best available data. Estimated densities used to inform take estimates are presented in Table 6.

Table 6—Marine Mammal Densities in the Planned Survey Area

SpeciesEstimated density (#/km2) a
LF Cetaceans
Southern right whale0.007965
Pygmy right whaleN.A.
Blue whale0.000051
Fin whale0.000356
Sei whale0.000086
Bryde's whale0.000439
Common (dwarf) minke whale0.077896
Antarctic minke whale0.077896
Humpback whale0.000310
MF Cetaceans
Sperm whale0.005975
Arnoux's beaked whale0.011379
Cuvier's beaked whale0.000548
Southern bottlenose whale0.007906
Shepherd's beaked whale0.009269
Blainville's beaked whale0.000053
Gray's beaked whale0.001885
Hector's beaked whale0.000212
Gervais' beaked whale0.001323
True's beaked whale0.000053
Strap-toothed beaked whale0.000582
Andrew's beaked whale0.000159
Spade-toothed beaked whale0.000053
Risso's dolphin0.010657
Rough-toothed dolphin0.005954
Common bottlenose dolphin0.040308
Pantropical spotted dolphin0.003767
Atlantic spotted dolphin0.213721
Spinner dolphin0.040720
Clymene dolphin0.006800
Striped dolphin0.004089
Short-beaked common dolphin0.717166
Fraser's dolphin0.021040
Dusky dolphin0.012867
Southern right whale dolphin0.006827
Killer whale0.000266
Short-finned pilot whale0.002085
Long-finned pilot whale0.021379
False killer whale0.000882
Pygmy killer whale0.000321
Melon-headed whale0.003540
HF Cetaceans
Pygmy sperm whale0.003418
Dwarf sperm whale0.002582
Hourglass dolphin0.011122
Subantarctic fur seal0.00274
Cape fur sealN.A.
Crabeater seal0.00649
Leopard seal0.00162
Southern elephant seal0.00155
N.A. indicates density estimate is not available.
Species in italics are listed under the ESA as endangered.
a See Appendix B in SIO's IHA application for density sources.

Take Calculation and Estimation

Here we describe how the information provided above is brought together to produce a quantitative take estimate. In order to estimate the number of marine mammals predicted to be exposed to sound levels that would result in Level A harassment or Level B harassment, radial distances from the airgun array to predicted isopleths corresponding to the Level A harassment and Level B harassment thresholds are calculated, as described above. Those radial distances are then used to calculate the area(s) around the airgun array predicted to be ensonified to sound levels that exceed the Level A harassment and Level B harassment thresholds. The area estimated to be ensonified in a single day of the survey is then calculated (Table 7), based on the areas predicted to be ensonified around the array and the estimated trackline distance traveled per day. This number is then multiplied by the number of survey days. The product is then multiplied by 1.25 to account for the additional 25 percent contingency. This results in an estimate of the total area (km2) expected to be ensonified to the Level A and Level B harassment thresholds for each survey type (Table 7).

Table 7—Areas (km2) To Be Ensonified to Level A and Level B Harassment Thresholds

Survey typeCriteriaRelevant isopleth (m)Daily ensonified area (km2)Total survey days25 percent increaseTotal ensonified area (km2)
5-kn surveyLevel B Harassment (160 dB)
Intermediate water80914.67101.25183.34
Deep water539231.31101.252891.42
Level A Harassment
LF cetacean6.52.89101.2536.125
MF cetacean10.44101.255.55
HF cetacean34.615.37101.25192.13
Start Printed Page 60068
8-kn surveyLevel B Harassment (160 dB)
Intermediate water86725.9541.25129.75
Deep water578395.8841.251979.38
Level A Harassment
LF cetacean3.12.2141.2511.04
MF cetacean0041.250
HF cetacean34.824.7841.25124

The total ensonified areas (km2) for each criteria presented in Table 7 were summed to determine the total ensonified area for all survey activities (Table 8).

Table 8—Total Ensonified Areas (km2) for All Surveys

CriteriaTotal ensonified area (km2) for all surveys
160 dB Level B (all depths)5183.89
160 dB Level B (intermediate water)313.09
160 dB Level B (deep water)4870.80
LF cetacean Level A47.11
MF cetacean Level A5.55
HF cetacean Level A316.04
Phocids Level A44.77
Otariids Level A2.77

The marine mammals predicted to occur within these respective areas, based on estimated densities (Table 6), are assumed to be incidentally taken. While some takes by Level A harassment have been estimated, based on the nature of the activity and in consideration of the planned mitigation measures (see Mitigation section below), Level A take is not expected to occur and has not been authorized. Estimated exposures for the planned survey are shown in Table 9.

Table 9—Calculated and Authorized Level A and Level B Exposures, and Percentage of Population Exposed

SpeciesCalculated take 1Authorized take 4Percent of population 5
Level B harassment 2Level A harassment 3Level B harassment only
LF Cetaceans:
Southern right whale410411.3
Pygmy right whaleN.A.N.A.5 2N.A.
Blue whale0036<0.1
Fin whale2046<0.1
Sei whale0036<0.1
Bryde's whale2020 5<0.1
Common (dwarf) minke whale4004404<0.1
Antarctic minke whale4004404<0.1
Humpback whale2020 350
MF Cetaceans:
Sperm whale310310.3
Arnoux's beaked whale59059<0.1
Cuvier's beaked whale303<0.1
Southern bottlenose whale41041<0.1
Shepherd's beaked whale48048N.A.
Blainville's beaked whale007 6N.A.
Gray's beaked whale10010<0.1
Hector's beaked whale102 6N.A.
Gervais' beaked whale707N.A.
True's beaked whale002 6N.A.
Strap-toothed beaked whale303<0.1
Andrew's beaked whale102 6N.A.
Spade-toothed beaked whale002 6N.A.
Start Printed Page 60069
Risso's dolphin55078 60.3
Rough-toothed dolphin31055 6N.A.
Common bottlenose dolphin20902090.3
Pantropical spotted dolphin200104 60.6
Atlantic spotted dolphin1108011082.5
Spinner dolphin2110315 6N.A.
Clymene dolphin350122 6N.A.
Striped dolphin210110 5<0.1
Short-beaked common dolphin3714437185.3
Fraser's dolphin1090283 6N.A.
Dusky dolphin670670.9
Southern right whale dolphin35035N.A.
Killer whale108 6<0.1
Short-finned pilot whale11041 6<0.1
Long-finned pilot whale11101110.1
False killer whale5035 6N.A.
Pygmy killer whale2026 6N.A.
Melon-headed whale180170 6N.A.
HF Cetaceans:
Pygmy sperm whale17118N.A.
Dwarf sperm whale12113N.A.
Hourglass dolphin54458<0.1
Subantarctic fur seal14014<0.1
Cape fur sealN.A.N.A.20 7N.A.
Crabeater seal34034<0.1
Leopard seal808<0.1
Southern elephant seal808<0.1
Species in italics are listed under the ESA as endangered. N.A. (-) is not available.
1 Take using NMFS daily method for calculating ensonified area: Estimated density multiplied by the daily ensonified area to levels ≥160 dB re 1 µParms on one selected day multiplied by the number of survey days, times 1.25 (see Appendix C); daily ensonified area = full 160-dB area minus ensonified area for the appropriate PTS threshold.
2 Level B harassment takes, based on the 160-dB criterion, excluding exposures to sound levels equivalent to PTS thresholds.
3 Level A harassment takes if there were no mitigation measures.
4 Authorized take by Level B harassment are the Level B harassment calculated takes, unless otherwise indicated. For those species where Level A harassment takes were calculated, those takes were added to the Authorized Level B harassment takes. Level A harassment is unlikely due to size of the calculated PTS isopleths (very small) and the mitigation measures (i.e., shutdown zones).
5 Authorized take (Level B harassment only) increased to maximum group size from Jefferson et al. (2015).
6 Authorized take (Level B harassment only) increased to mean group size from Di Tullio et al. (2016).
7 Authorized take (Level B harassment only) increased to 20 individuals, as no densities available.

It should be noted that the planned take numbers shown in Table 9 are expected to be conservative for several reasons. First, in the calculations of estimated take, 25 percent has been added in the form of operational survey days to account for the possibility of additional seismic operations associated with airgun testing and repeat coverage of any areas where initial data quality is sub-standard, and in recognition of the uncertainties in the density estimates used to estimate take as described above. Additionally, marine mammals would be expected to move away from a loud sound source that represents an aversive stimulus, such as an airgun array, potentially reducing the likelihood of takes by Level A harassment. However, the extent to which marine mammals would move away from the sound source is difficult to quantify and is, therefore, not accounted for in the take estimates.


In order to issue an IHA under Section 101(a)(5)(D) of the MMPA, NMFS must set forth the permissible methods of taking pursuant to such activity, and other means of effecting the least practicable impact on such species or stock and its habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, and on the availability of such species or stock for taking for certain subsistence uses (latter not applicable for this action). NMFS regulations require applicants for incidental take authorizations to include information about the availability and feasibility (economic and technological) of equipment, methods, and manner of conducting such activity or other means of effecting the least practicable adverse impact upon the affected species or stocks and their habitat (50 CFR 216.104(a)(11)).

In evaluating how mitigation may or may not be appropriate to ensure the least practicable adverse impact on species or stocks and their habitat, as well as subsistence uses where applicable, we carefully consider two primary factors:

(1) The manner in which, and the degree to which, the successful implementation of the measure(s) is expected to reduce impacts to marine mammals, marine mammal species or stocks, and their habitat. This considers the nature of the potential adverse Start Printed Page 60070impact being mitigated (likelihood, scope, range). It further considers the likelihood that the measure will be effective if implemented (probability of accomplishing the mitigating result if implemented as planned), the likelihood of effective implementation (probability implemented as planned); and

(2) The practicability of the measures for applicant implementation, which may consider such things as cost, impact on operations, and, in the case of a military readiness activity, personnel safety, practicality of implementation, and impact on the effectiveness of the military readiness activity.

SIO has reviewed mitigation measures employed during seismic research surveys authorized by NMFS under previous incidental harassment authorizations, as well as recommended best practices in Richardson et al. (1995), Pierson et al. (1998), Weir and Dolman (2007), Nowacek et al. (2013), Wright (2014), and Wright and Cosentino (2015), and has incorporated a suite of required mitigation measures into their project description based on the above sources.

To reduce the potential for disturbance from acoustic stimuli associated with the activities, SIO is required to implement mitigation measures for marine mammals. Mitigation measures that must be adopted during the planned surveys include (1) Vessel-based visual mitigation monitoring; (2) Establishment of a marine mammal exclusion zone (EZ) and buffer zone; (3) shutdown procedures; (4) ramp-up procedures; and (4) vessel strike avoidance measures.

Vessel-Based Visual Mitigation Monitoring

Visual monitoring requires the use of trained observers (herein referred to as visual PSOs) to scan the ocean surface visually for the presence of marine mammals. PSO(s) must be on duty and conducting visual observations at all times during daylight hours (i.e., from 30 minutes prior to sunrise through 30 minutes following sunset). Visual monitoring must begin not less than 30 minutes prior to ramp-up, including for nighttime ramp-ups of the airgun array, and must continue until one hour after use of the acoustic source ceases or until 30 minutes past sunset. Following a shutdown for any reason, observations must occur for at least 30 minutes prior to the planned start of airgun operations. Observations must also occur for 60 minutes after airgun operations cease for any reason (except after sunset). Observations must also be made during daytime periods when the Thompson is underway without seismic operations, such as during transits, to allow for comparison of sighting rates and behavior with and without airgun operations and between acquisition periods. Airgun operations must be suspended when marine mammals are observed within, or about to enter, the designated EZ (as described below).

During seismic operations, three visual PSOs must be based aboard the Thompson. PSOs must be appointed by SIO with NMFS approval. One dedicated PSO must monitor the EZ during all daytime seismic operations. PSO(s) must be on duty in shifts of duration no longer than 4 hours. Other vessel crew must also be instructed to assist in detecting marine mammals and in implementing mitigation requirements (if practical). Before the start of the seismic survey, the crew must be given additional instruction in detecting marine mammals and implementing mitigation requirements.

The Thompson is a suitable platform from which PSOs would watch for marine mammals. Standard equipment for marine mammal observers must be 7 x 50 reticule binoculars and optical range finders. At night, night-vision equipment must be available. The observers must be in communication with ship's officers on the bridge and scientists in the vessel's operations laboratory, so they can advise promptly of the need for avoidance maneuvers or seismic source shutdown.

The PSOs must have no tasks other than to conduct observational effort, record observational data, and communicate with and instruct relevant vessel crew with regard to the presence of marine mammals and mitigation requirements. PSO resumes shall be provided to NMFS for approval. At least one PSO must have a minimum of 90 days at-sea experience working as PSOs during a seismic survey. One “experienced” visual PSO will be designated as the lead for the entire protected species observation team. The lead will serve as primary point of contact for the vessel operator.

Exclusion Zone and Buffer Zone

An EZ is a defined area within which occurrence of a marine mammal triggers mitigation action intended to reduce the potential for certain outcomes, e.g., auditory injury, disruption of critical behaviors. The PSOs must establish a minimum EZ with a 100 m radius for the airgun array. The 100-m EZ must be based on radial distance from any element of the airgun array (rather than being based on the center of the array or around the vessel itself). With certain exceptions (described below), if a marine mammal appears within, enters, or appears on a course to enter this zone, the acoustic source must be shut down (see Shutdown Procedures below).

The 100-m radial distance of the standard EZ is precautionary in the sense that it would be expected to contain sound exceeding injury criteria for all marine mammal hearing groups (Table 5) while also providing a consistent, reasonably observable zone within which PSOs would typically be able to conduct effective observational effort. In this case, the 100-m radial distance would also be expected to contain sound that would exceed the Level A harassment threshold based on sound exposure level (SELcum) criteria for all marine mammal hearing groups (Table 5). In the 2011 Programmatic Environmental Impact Statement for marine scientific research funded by the National Science Foundation or the U.S. Geological Survey (NSF-USGS 2011), Alternative B (the Preferred Alternative) conservatively applied a 100-m EZ for all low-energy acoustic sources in water depths >100 m, with low-energy acoustic sources defined as any towed acoustic source with a single or a pair of clustered airguns with individual volumes of ≤250 in3. Thus the 100-m EZ planned for this survey is consistent with the PEIS.

Our intent in prescribing a standard EZ distance is to (1) encompass zones within which auditory injury could occur on the basis of instantaneous exposure; (2) provide additional protection from the potential for more severe behavioral reactions (e.g., panic, antipredator response) for marine mammals at relatively close range to the acoustic source; (3) provide consistency for PSOs, who need to monitor and implement the EZ; and (4) define a distance within which detection probabilities are reasonably high for most species under typical conditions.

PSOs will also establish and monitor a 200-m buffer zone. During use of the acoustic source, occurrence of marine mammals within the buffer zone (but outside the EZ) will be communicated to the operator to prepare for potential shutdown of the acoustic source. The buffer zone is discussed further under Ramp Up Procedures below.

An extended EZ of 500 m must be enforced for all beaked whales, Kogia species, and Southern right whales. SIO must also enforce a 500-m EZ for aggregations of six or more large whales (i.e., sperm whale or any baleen whale) that does not appear to be traveling (e.g., feeding, socializing, etc.) or a large Start Printed Page 60071whale with a calf (calf defined as an animal less than two-thirds the body size of an adult observed to be in close association with an adult).

Shutdown Procedures

If a marine mammal is detected outside the EZ but is likely to enter the EZ, the airguns must be shut down before the animal is within the EZ. Likewise, if a marine mammal is already within the EZ when first detected, the airguns must be shut down immediately.

Following a shutdown, airgun activity must not resume until the marine mammal has cleared the 100-m EZ. The animal must be considered to have cleared the 100-m EZ if the following conditions have been met:

  • It is visually observed to have departed the 100-m EZ;
  • it has not been seen within the 100-m EZ for 15 min in the case of small odontocetes and pinnipeds; or
  • it has not been seen within the 100-m EZ for 30 min in the case of mysticetes and large odontocetes (including sperm whales), and also pygmy sperm whales, dwarf sperm whales, pilot whales, beaked whales, and Risso's dolphins.

This shutdown requirement must be in place for all marine mammals, with the exception of small delphinoids under certain circumstances. As defined here, the small delphinoid group is intended to encompass those members of the Family Delphinidae most likely to voluntarily approach the source vessel for purposes of interacting with the vessel and/or airgun array (e.g., bow riding). This exception to the shutdown requirement would apply solely to specific genera of small dolphins—Delphinus, Lagenodelphis, Lagenorhynchus, Lissodelphis, Stenella, Steno, and Tursiops—and would only apply if the animals were traveling, including approaching the vessel. If, for example, an animal or group of animals is stationary for some reason (e.g., feeding) and the source vessel approaches the animals, the shutdown requirement applies. An animal with sufficient incentive to remain in an area rather than avoid an otherwise aversive stimulus could either incur auditory injury or disruption of important behavior. If there is uncertainty regarding identification (i.e., whether the observed animal(s) belongs to the group described above) or whether the animals are traveling, the shutdown must be implemented.

We include this small delphinoid exception because shutdown requirements for small delphinoids under all circumstances represent practicability concerns without likely commensurate benefits for the animals in question. Small delphinoids are generally the most commonly observed marine mammals in the specific geographic region and would typically be the only marine mammals likely to intentionally approach the vessel. As described above, auditory injury is extremely unlikely to occur for mid-frequency cetaceans (e.g., delphinids), as this group is relatively insensitive to sound produced at the predominant frequencies in an airgun pulse while also having a relatively high threshold for the onset of auditory injury (i.e., permanent threshold shift).

A large body of anecdotal evidence indicates that small delphinoids commonly approach vessels and/or towed arrays during active sound production for purposes of bow riding, with no apparent effect observed in those delphinoids (e.g., Barkaszi et al., 2012). The potential for increased shutdowns resulting from such a measure would require the Thompson to revisit the missed track line to reacquire data, resulting in an overall increase in the total sound energy input to the marine environment and an increase in the total duration over which the survey is active in a given area. Although other mid-frequency hearing specialists (e.g., large delphinoids) are no more likely to incur auditory injury than are small delphinoids, they are much less likely to approach vessels. Therefore, retaining a power-down/shutdown requirement for large delphinoids would not have similar impacts in terms of either practicability for the applicant or corollary increase in sound energy output and time on the water. We do anticipate some benefit for a shutdown requirement for large delphinoids in that it simplifies somewhat the total range of decision-making for PSOs and may preclude any potential for physiological effects other than to the auditory system as well as some more severe behavioral reactions for any such animals in close proximity to the source vessel.

Shutdown of the acoustic source is also required upon observation of a species for which authorization has not been granted, or a species for which authorization has been granted but the authorized number of takes are met, observed approaching or within the Level A or Level B harassment zones.

Ramp-up Procedures

Ramp-up of an acoustic source is intended to provide a gradual increase in sound levels following a shutdown, enabling animals to move away from the source if the signal is sufficiently aversive prior to its reaching full intensity. Ramp-up is required after the array is shut down for any reason for longer than 15 minutes. Ramp-up would begin with the activation of one 45 in3 airgun, with the second 45 in3 airgun activated after 5 minutes.

Two PSOs are required to monitor during ramp-up. During ramp up, the PSOs must monitor the EZ, and if marine mammals were observed within the EZ or buffer zone, a shutdown must be implemented as though the full array were operational. If airguns have been shut down due to PSO detection of a marine mammal within or approaching the 100 m EZ, ramp-up must not be initiated until all marine mammals have cleared the EZ, during the day or night. Criteria for clearing the EZ would be as described above.

Thirty minutes of pre-clearance observation are required prior to ramp-up for any shutdown of longer than 30 minutes (i.e., if the array were shut down during transit from one line to another). This 30-minute pre-clearance period may occur during any vessel activity (i.e., transit). If a marine mammal were observed within or approaching the 100 m EZ during this pre-clearance period, ramp-up must not be initiated until all marine mammals cleared the EZ. Criteria for clearing the EZ would be as described above. If the airgun array has been shut down for reasons other than mitigation (e.g., mechanical difficulty) for a period of less than 30 minutes, it may be activated again without ramp-up if PSOs have maintained constant visual observation and no detections of any marine mammal have occurred within the EZ or buffer zone. Ramp-up must be planned to occur during periods of good visibility when possible. However, ramp-up is allowed at night and during poor visibility if the 100 m EZ and 200 m buffer zone have been monitored by visual PSOs for 30 minutes prior to ramp-up.

The operator is required to notify a designated PSO of the planned start of ramp-up as agreed-upon with the lead PSO; the notification time should not be less than 60 minutes prior to the planned ramp-up. A designated PSO must be notified again immediately prior to initiating ramp-up procedures and the operator must receive confirmation from the PSO to proceed. The operator must provide information to PSOs documenting that appropriate procedures were followed. Following deactivation of the array for reasons other than mitigation, the operator is required to communicate the near-term operational plan to the lead PSO with Start Printed Page 60072justification for any planned nighttime ramp-up.

Vessel Strike Avoidance Measures

Vessel strike avoidance measures are intended to minimize the potential for collisions with marine mammals. These requirements do not apply in any case where compliance would create an imminent and serious threat to a person or vessel or to the extent that a vessel is restricted in its ability to maneuver and, because of the restriction, cannot comply.

The required measures include the following: Vessel operator and crew must maintain a vigilant watch for all marine mammals and slow down or stop the vessel or alter course to avoid striking any marine mammal. A visual observer aboard the vessel must monitor a vessel strike avoidance zone around the vessel according to the parameters stated below. Visual observers monitoring the vessel strike avoidance zone may be either third-party observers or crew members, but crew members responsible for these duties must be provided sufficient training to distinguish marine mammals from other phenomena. Vessel strike avoidance measures must be followed during surveys and while in transit.

The vessel must maintain a minimum separation distance of 100 m from large whales (i.e., baleen whales and sperm whales). If a large whale is within 100 m of the vessel, the vessel must reduce speed and shift the engine to neutral, and must not engage the engines until the whale has moved outside of the vessel's path and the minimum separation distance has been established. If the vessel is stationary, the vessel must not engage engines until the whale(s) has moved out of the vessel's path and beyond 100 m. The vessel must maintain a minimum separation distance of 50 m from all other marine mammals (with the exception of delphinids of the genera Delphinus, Lagenodelphis, Lagenorhynchus, Lissodelphis, Stenella, Steno, and Tursiops that approach the vessel, as described above). If an animal is encountered during transit, the vessel must attempt to remain parallel to the animal's course, avoiding excessive speed or abrupt changes in course. Vessel speeds must be reduced to 10 kn or less when mother/calf pairs, pods, or large assemblages of cetaceans are observed near the vessel.

Based on our evaluation of the applicant's required measures, NMFS has determined that the planned mitigation measures provide the means effecting the least practicable impact on the affected species or stocks and their habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance.

Monitoring and Reporting

In order to issue an IHA for an activity, Section 101(a)(5)(D) of the MMPA states that NMFS must set forth requirements pertaining to the monitoring and reporting of such taking. The MMPA implementing regulations at 50 CFR 216.104(a)(13) indicate that requests for authorizations must include the suggested means of accomplishing the necessary monitoring and reporting that will result in increased knowledge of the species and of the level of taking or impacts on populations of marine mammals that are expected to be present in the planned action area. Effective reporting is critical both to compliance as well as ensuring that the most value is obtained from the required monitoring.

Monitoring and reporting requirements prescribed by NMFS should contribute to improved understanding of one or more of the following:

  • Occurrence of marine mammal species or stocks in the area in which take is anticipated (e.g., presence, abundance, distribution, density);
  • Nature, scope, or context of likely marine mammal exposure to potential stressors/impacts (individual or cumulative, acute or chronic), through better understanding of: (1) Action or environment (e.g., source characterization, propagation, ambient noise); (2) affected species (e.g., life history, dive patterns); (3) co-occurrence of marine mammal species with the action; or (4) biological or behavioral context of exposure (e.g., age, calving or feeding areas);
  • Individual marine mammal responses (behavioral or physiological) to acoustic stressors (acute, chronic, or cumulative), other stressors, or cumulative impacts from multiple stressors;
  • How anticipated responses to stressors impact either: (1) long-term fitness and survival of individual marine mammals; or (2) populations, species, or stocks;
  • Effects on marine mammal habitat (e.g., marine mammal prey species, acoustic habitat, or other important physical components of marine mammal habitat); and
  • Mitigation and monitoring effectiveness.

SIO described marine mammal monitoring and reporting plan within their IHA application. Monitoring that is designed specifically to facilitate mitigation measures, such as monitoring of the EZ to inform potential shutdowns of the airgun array, are described above and are not repeated here. SIO's monitoring and reporting plan includes the following measures:

Vessel-Based Visual Monitoring

As described above, PSO observations must take place during daytime airgun operations and nighttime start-ups (if applicable) of the airguns. During seismic operations, three visual PSOs must be based aboard the Thompson. PSOs must be appointed by SIO with NMFS approval. The PSOs must have successfully completed relevant training, including completion of all required coursework and passing a written and/or oral examination developed for the training program, and must have successfully attained a bachelor's degree from an accredited college or university with a major in one of the natural sciences and a minimum of 30 semester hours or equivalent in the biological sciences and at least one undergraduate course in math or statistics. The educational requirements may be waived if the PSO has acquired the relevant skills through alternate training, including (1) secondary education and/or experience comparable to PSO duties; (2) previous work experience conducting academic, commercial, or government-sponsored marine mammal surveys; or (3) previous work experience as a PSO; the PSO should demonstrate good standing and consistently good performance of PSO duties.

During the majority of seismic operations, one PSO is required to monitor for marine mammals around the seismic vessel. PSOs must be on duty in shifts of duration no longer than 4 hours. Other crew must also be instructed to assist in detecting marine mammals and in implementing mitigation requirements (if practical). During daytime, PSOs must scan the area around the vessel systematically with reticle binoculars (e.g., 7 × 50 Fujinon) and with the naked eye. At night, PSOs must be equipped with night-vision equipment.

PSOs must record data to estimate the numbers of marine mammals exposed to various received sound levels and to document apparent disturbance reactions or lack thereof. Data must be used to estimate numbers of animals potentially `taken' by harassment (as defined in the MMPA). They must also provide information needed to order a shutdown of the airguns when a marine mammal is within or near the EZ. When a sighting is made, the following information about the sighting must be recorded:Start Printed Page 60073

(1) Species, group size, age/size/sex categories (if determinable), behavior when first sighted and after initial sighting, heading (if consistent), bearing and distance from seismic vessel, sighting cue, apparent reaction to the airguns or vessel (e.g., none, avoidance, approach, paralleling, etc.), and behavioral pace; and

(2) Time, location, heading, speed, activity of the vessel, sea state, visibility, and sun glare.

All observations and shutdowns must be recorded in a standardized format. Data must be entered into an electronic database. The accuracy of the data entry must be verified by computerized data validity checks as the data are entered and by subsequent manual checking of the database. These procedures allow initial summaries of data to be prepared during and shortly after the field program and facilitate transfer of the data to statistical, graphical, and other programs for further processing and archiving. The time, location, heading, speed, activity of the vessel, sea state, visibility, and sun glare must also be recorded at the start and end of each observation watch, and during a watch whenever there is a change in one or more of the variables.

Results from the vessel-based observations must provide:

(1) The basis for real-time mitigation (e.g., airgun shutdown);

(2) Information needed to estimate the number of marine mammals potentially taken by harassment, which must be reported to NMFS;

(3) Data on the occurrence, distribution, and activities of marine mammals in the area where the seismic study is conducted;

(4) Information to compare the distance and distribution of marine mammals relative to the source vessel at times with and without seismic activity; and

(5) Data on the behavior and movement patterns of marine mammals seen at times with and without seismic activity.


A draft report must be submitted to NMFS within 90 days after the end of the survey. The report must describe the operations that were conducted and sightings of marine mammals near the operations. The report must provide full documentation of methods, results, and interpretation pertaining to all monitoring and must summarize the dates and locations of seismic operations, including percentage of time and total time the array is active during daylight versus nighttime hours (including dawn and dusk), and all marine mammal sightings (dates, times, locations, activities, associated seismic survey activities). The report must also include estimates of the number and nature of exposures that occurred above the harassment threshold based on PSO observations, including an estimate of those that were not detected in consideration of both the characteristics and behaviors of the species of marine mammals that affect detectability, as well as the environmental factors that affect detectability.

The draft report shall also include geo-referenced time-stamped vessel tracklines for all time periods during which airguns were operating. Tracklines should include points recording any change in airgun status (e.g., when the airguns began operating, when they were turned off, or when they changed from full array to single gun or vice versa). GIS files shall be provided in ESRI shapefile format and include the UTC date and time, latitude in decimal degrees, and longitude in decimal degrees. All coordinates shall be referenced to the WGS84 geographic coordinate system. In addition to the report, all raw observational data shall be made available to NMFS. The draft report must be accompanied by a certification from the lead PSO as to the accuracy of the report, and the lead PSO may submit directly NMFS a statement concerning implementation and effectiveness of the required mitigation and monitoring. A final report must be submitted within 30 days following resolution of any comments on the draft report.

Negligible Impact Analysis and Determination

NMFS has defined negligible impact 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 (50 CFR 216.103). A negligible impact finding is based on the lack of likely adverse effects on annual rates of recruitment or survival (i.e., population-level effects). An estimate of the number of takes alone is not enough information on which to base an impact determination. In addition to considering estimates of the number of marine mammals that might be “taken” through harassment, NMFS considers other factors, such as the likely nature of any responses (e.g., intensity, duration), the context of any responses (e.g., critical reproductive time or location, migration), as well as effects on habitat, and the likely effectiveness of the mitigation. We also assess the number, intensity, and context of estimated takes by evaluating this information relative to population status. Consistent with the 1989 preamble for NMFS's implementing regulations (54 FR 40338; September 29, 1989), the impacts from other past and ongoing anthropogenic activities are incorporated into this analysis via their impacts on the environmental baseline (e.g., as reflected in the regulatory status of the species, population size and growth rate where known, ongoing sources of human-caused mortality, or ambient noise levels).

To avoid repetition, our analysis applies to all the species listed in Table 1, given that NMFS expects the anticipated effects of the planned seismic survey to be similar in nature. Where there are meaningful differences between species or stocks, or groups of species, in anticipated individual responses to activities, impact of expected take on the population due to differences in population status, or impacts on habitat, NMFS has identified species-specific factors to inform the analysis.

NMFS does not anticipate that serious injury or mortality would occur as a result of SIO's planned seismic survey, even in the absence of planned mitigation. Thus the authorization does not authorize any mortality. As discussed in the Potential Effects section, neither stranding nor vessel strike are expected to occur.

No takes by Level A harassment are authorized. The 100-m exclusion zone encompasses the Level A harassment isopleths for all marine mammal hearing groups, and is expected to prevent animals from being exposed to sound levels that would cause PTS. Also, as described above, we expect that marine mammals would be likely to move away from a sound source that represents an aversive stimulus, especially at levels that would be expected to result in PTS, given sufficient notice of the Thompson's approach due to the vessel's relatively low speed when conducting seismic surveys. We expect that any instances of take would be in the form of short-term Level B behavioral harassment in the form of temporary avoidance of the area or short-term decreased foraging (if such activity were occurring), reactions that are considered to be of low severity and with no lasting biological consequences (e.g., Southall et al., 2007).

Potential impacts to marine mammal habitat were discussed previously in this document (see Potential Effects of the Specified Activity on Marine Mammals and their Habitat). Marine mammal habitat may be impacted by Start Printed Page 60074elevated sound levels, but these impacts would be temporary. Prey species are mobile and are broadly distributed throughout the project area; therefore, marine mammals that may be temporarily displaced during survey activities are expected to be able to resume foraging once they have moved away from areas with disturbing levels of underwater noise.

Because of the temporary nature of the disturbance, the availability of similar habitat and resources in the surrounding area, and the lack of important or unique marine mammal habitat, the impacts to marine mammals and the food sources that they utilize are not expected to cause significant or long-term consequences for individual marine mammals or their populations. In addition, there are no feeding, mating or calving areas known to be biologically important to marine mammals within the planned project area.

As described above, marine mammals in the survey area are not assigned to NMFS stocks. The activity is expected to impact a very small percentage of all marine mammal populations, most cases 0.1 percent or less that would be affected by SIO's planned survey (less than 5.3 percent each for all marine mammal populations where abundance estimates exist). Additionally, the acoustic “footprint” of the planned survey would be very small relative to the ranges of all marine mammals that would potentially be affected. Sound levels would increase in the marine environment in a relatively small area surrounding the vessel compared to the range of the marine mammals within the planned survey area. The seismic array would be active 24 hours per day throughout the duration of the planned survey. However, the very brief overall duration of the planned survey (14 days) would further limit potential impacts that may occur as a result of the planned activity.

The required mitigation measures are expected to reduce the number and/or severity of takes by allowing for detection of marine mammals in the vicinity of the vessel by visual and acoustic observers, and by minimizing the severity of any potential exposures via shutdowns of the airgun array. The required mitigation (in combination with the small Level A harassment zones) will be effective in preventing PTS in all species and none is authorized.

Of the marine mammal species under our jurisdiction that are likely to occur in the project area, the following species are listed as endangered under the ESA: Fin, sei, blue, sperm, and southern right whales. We are proposing to authorize very small numbers of takes for these species (Table 9), relative to their population sizes (again, for species where population abundance estimates exist), therefore we do not expect population-level impacts to any of these species. There is no known biological important areas for any of the species listed in Table 9. The other marine mammal species that may be taken by harassment during SIO's seismic survey are not listed as threatened or endangered under the ESA. There is no designated critical habitat for any ESA-listed marine mammals within the project area; of the non-listed marine mammals for which we propose to authorize take, none are considered “depleted” or “strategic” by NMFS under the MMPA.

NMFS concludes that exposures to marine mammal species due to SIO's planned seismic survey would result in only short-term (temporary and short in duration) effects of Level B harassment to individuals exposed. Marine mammals may temporarily avoid the immediate area, but are not expected to permanently abandon the area. Major shifts in habitat use, distribution, or foraging success are not expected. NMFS does not anticipate the authorized take estimates to impact annual rates of recruitment or survival.

In summary and as described above, the following factors primarily support our determination that the impacts resulting from this activity are not expected to adversely affect the species or stock through effects on annual rates of recruitment or survival:

  • No mortality is anticipated or authorized;
  • No take by Level A harassment is anticipated or authorized;
  • The anticipated impacts of the planned activity on marine mammals would primarily be temporary behavioral changes due to avoidance of the area around the survey vessel. The relatively short duration of the planned survey (14 days) would further limit the potential impacts of any temporary behavioral changes that would occur;
  • The availability of alternate areas of similar habitat value for marine mammals to temporarily vacate the survey area during the planned survey to avoid exposure to sounds from the activity;
  • The planned project area does not contain areas of significance for feeding, mating or calving;
  • The potential adverse effects on fish or invertebrate species that serve as prey species for marine mammals from the planned survey would be temporary and spatially limited; and
  • The planned mitigation measures, including visual and acoustic monitoring and shutdowns, are expected to minimize potential impacts to marine mammals.

Based on the analysis contained herein of the likely effects of the specified activity on marine mammals and their habitat, and taking into consideration the implementation of the required monitoring and mitigation measures, NMFS finds that the total marine mammal take from the planned activity will have a negligible impact on all affected marine mammal species or stocks.

Small Numbers

As noted above, only small numbers of incidental take may be authorized under Sections 101(a)(5)(A) and (D) of the MMPA for specified activities other than military readiness activities. The MMPA does not define small numbers and so, in practice, where estimated numbers are available, NMFS compares the number of individuals taken to the most appropriate estimation of abundance of the relevant species or stock in our determination of whether an authorization is limited to small numbers of marine mammals. Additionally, other qualitative factors may be considered in the analysis, such as the temporal or spatial scale of the activities.

The numbers of marine mammals that we authorize to be taken would be considered small relative to the relevant populations (less than 5.3 percent for all species) for the species for which abundance estimates are available. No known current worldwide or regional population estimates are available for 16 species under NMFS jurisdiction that could be incidentally taken as a result of the planned survey: the pygmy right whale, pygmy sperm whale, dwarf sperm whale, Shepherd's beaked whale, Blainville's beaked whale, Hector's beaked whale, Gervais' beaked whale, True's beaked whale, Andrew's beaked whale, spade-toothed beaked whale, rough-toothed dolphin, spinner dolphin, Clymene dolphin, Fraser's dolphin, southern right whale dolphin, false killer whale, pygmy killer whale, and Melon-headed whale and Cape fur seal.

NMFS has reviewed the geographic distributions and habitat preferences of these species in determining whether the numbers of takes authorized herein are likely to represent small numbers. Pygmy right whales have a circumglobal distribution and occur throughout coastal and oceanic waters in the Southern Hemisphere (between 30 to 55° S) (Jefferson et al. 2015; Kemper Start Printed Page 600752018). Pygmy and dwarf sperm whales occur in deep waters on the outer continental shelf and slope in tropical to temperate waters of the Atlantic, Indian, and Pacific Oceans, but their precise distributions are unknown because much of what we know of the species comes from strandings (McAlpine, 2018). Based on stranding records and the known habitat preferences of beaked whales in general, Shepherd's beaked whales are assumed to have a circumpolar distribution in deep, cold temperate waters of the Southern Ocean (Pitman et al., 2006; Mead 2018). Blainville's beaked whale is the most widely distributed beaked Mesoplodon species with sightings and stranding records throughout the North and South Atlantic Ocean (MacLeod et al., 2006; Pitman, 2018). Hector's beaked whales are found in cold temperate waters throughout the southern hemisphere between 35° S and 55° S (Zerbini and Secchi, 2001; Pitman, 2018). True's beaked whale has a disjunct, antitropical distribution (Jefferson et al., 2015). In the Southern Hemisphere, it is known to occur in South Africa, South America, and Australia (Findlay et al. 1992; Souza et al., 2005; MacLeod and Mitchell 2006; MacLeod et al., 2006; Best et al., 2009). Andrew's beaked whales have a circumpolar distribution north of the Antarctic Convergence to 32° S (MacLeod et al., 2006; Pitman, 2018). Andrew's beaked whale is known only from stranding records between 32° S and 55° S, with more than half of the strandings occurring in New Zealand (Jefferson et al., 2015). Gervais' beaked whale is generally considered to be a North Atlantic species, it likely occurs in deep waters of the temperate and tropical Atlantic Ocean in both the northern and southern hemispheres (Jefferson et al., 2015). The southernmost stranding record was reported for São Paulo, Brazil, possibly expanding the known distributional range of this species southward (Santos et al., 2003), but the distribution range of Gervais' beaked whale is not generally known to extend as far south as the planned project area. The spade-toothed beaked whale is considered relatively rare and is known from only four records, three from New Zealand and one from Chile (Thompson et al., 2012). The rough-toothed dolphin is distributed worldwide in tropical and subtropical waters (Jefferson et al., 2015). Rough-toothed dolphins are generally seen in deep, oceanic water, although it is known to occur in coastal waters of Brazil (Jefferson et al., 2015; Cardoso et al., 2019). The Clymene dolphin only occurs in tropical and subtropical waters of the Atlantic Ocean (Jefferson et al., 2015). Clymeme dolphins inhabits areas where water depths are 700-4,500 m or deeper (Fertl et al., 2003). Fraser's dolphins are distributed in tropical oceanic waters worldwide, between 30° N and 30° S and generally inhabits deeper, offshore water (Moreno et al., 2003, Dolar 2018). The southern right whale dolphin is distributed between the Subtropical and Antarctic convergences in the Southern Hemisphere, generally between ~30° S and 65° S (Jefferson et al., 2015; Lipsky and Brownell, 2018). The false killer whale is found worldwide in tropical and temperate waters, generally between 50 ° N and 50° S (Odell and McClune, 1999). It is widely distributed, but not abundant anywhere (Carwardine, 1995). The false killer whale generally inhabits deep, offshore waters, but sometimes is found over the continental shelf and occasionally moves into very shallow water (Jefferson et al., 2015; Baird, 2018b). The pygmy killer whale has a worldwide distribution in tropical and subtropical waters, generally not ranging south of 35° S (Jefferson et al. 2015). The melon-headed whale is an oceanic species found worldwide in tropical and subtropical waters from ~40° N to 35° S (Jefferson et al., 2015). The Cape fur seal currently breeds at 40 colonies along the coast of South Africa, Namibia, and Angola, including on the mainland and nearshore islands (Kirkman et al., 2013). There have been several new breeding colonies established in recent years, as the population has shifted northward (Kirkman et al., 2013). More than half of the seal population occurs in Namibia (Wickens et al., 1991). High densities have been observed between 30 and 60 nm from shore, with densities dropping farther offshore (Thomas and Schülein, 1988).

Based on the broad spatial distributions and habitat preferences of these species relative to the areas where SIO's planned survey will occur, NMFS concludes that the authorized take of these species likely represent small numbers relative to the affected species' overall population sizes, though we are unable to quantify the take numbers as a percentage of population.

Based on the analysis contained herein of the planned activity (including the required mitigation and monitoring measures) and the anticipated take of marine mammals, NMFS finds that small numbers of marine mammals will be taken relative to the population size of the affected species or stocks.

Unmitigable Adverse Impact Analysis and Determination

There are no relevant subsistence uses of the affected marine mammal stocks or species implicated by this action. Therefore, NMFS has determined that the total taking of affected species or stocks would not have an unmitigable adverse impact on the availability of such species or stocks for taking for subsistence purposes.

National Environmental Policy Act

To comply with the National Environmental Policy Act of 1969 (NEPA; 42 U.S.C. 4321 et seq.) and NOAA Administrative Order (NAO) 216-6A, NMFS must review our action (i.e., the issuance of an incidental harassment authorization) with respect to potential impacts on the human environment.

This action is consistent with categories of activities identified in Categorical Exclusion B4 (incidental harassment authorizations with no anticipated serious injury or mortality) of the Companion Manual for NOAA Administrative Order 216-6A, which do not individually or cumulatively have the potential for significant impacts on the quality of the human environment and for which we have not identified any extraordinary circumstances that would preclude this categorical exclusion. Accordingly, NMFS has determined that the issuance of the IHA qualifies to be categorically excluded from further NEPA review.

Endangered Species Act (ESA)

Section 7(a)(2) of the Endangered Species Act of 1973 (ESA: 16 U.S.C. 1531 et seq.) requires that each Federal agency insure that any action it authorizes, funds, or carries out is not likely to jeopardize the continued existence of any endangered or threatened species or result in the destruction or adverse modification of designated critical habitat. To ensure ESA compliance for the issuance of IHAs, NMFS consults internally, in this case with the ESA Interagency Cooperation Division, whenever we propose to authorize take for endangered or threatened species.

The NMFS Office of Protected Resources Interagency Cooperation Division issued a Biological Opinion on October 29, 2019, under section 7 of the ESA, on the issuance of an IHA to SIO under section 101(a)(5)(D) of the MMPA by the NMFS Permits and Conservation Division. The Biological Opinion concluded that the proposed action is not likely to jeopardize the continued existence of fin whale, sei whale, blue Start Printed Page 60076whale, sperm whale, and southern right whale, and is not likely to destroy or modify critical habitat of listed species because no critical habitat exists for these species in the action area.


As a result of these determinations, NMFS has issued an IHA to SIO for conducting a marine geophysical survey in the South Atlantic Ocean in November and December 2019, provided the previously mentioned mitigation, monitoring, and reporting requirements are incorporated.

Start Signature

Dated: November 1, 2019.

Donna S. Wieting,

Director, Office of Protected Resources, National Marine Fisheries Service.

End Signature End Supplemental Information

[FR Doc. 2019-24265 Filed 11-6-19; 8:45 am]