Taking and Importing Marine Mammals; Taking Marine Mammals Incidental to Geophysical Surveys in the Gulf of America

Table 2 lists all species with expected potential for occurrence in the GOA and summarizes information related to the population or stock, including potential biological removal (PBR). 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, is considered in concert with known sources of ongoing anthropogenic mortality (as described in NMFS' SARs). For status of species, we provide information regarding U.S. regulatory status under the MMPA and ESA.

In some cases, species are treated as guilds. In general ecological terms, a guild is a group of species that have similar requirements and play a similar role within a community. However, for purposes of stock assessment or density modeling, certain species may be treated together as a guild because they are difficult to distinguish visually and many observations are ambiguous. For example, NMFS' GOA SARs assess stocks of Mesoplodon spp. and Kogia spp. as guilds. Following this approach, we consider beaked whales and Kogia spp. as guilds. In this rule, reference to “beaked whales” includes the goose-beaked whale \5\ and Blainville's and Gervais' beaked whales, and reference to “Kogia spp.” includes both the dwarf and pygmy sperm whale.

\5\ Note that this species is referred to in NMFS' SARs as the “Cuvier's beaked whale.”

The use of guilds herein follows the best available density information (i.e., Garrison et al., 2023). The density models treat beaked whales and Kogia spp. as guilds and consolidate four species into an undifferentiated blackfish guild. These species include the melon-headed whale, false killer whale, pygmy killer whale, and killer whale. The model authors determined that, for this group of species, there were insufficient sightings of any individual species to generate a species-specific model (Garrison et al., 2023). Therefore, reference to blackfish hereafter includes the melon-headed whale, false killer whale, pygmy killer whale, and killer whale.\6\ Twenty-one species (with 24 managed stocks) have the potential to co-occur with the prospective survey activities. All managed stocks in this region are assessed in NMFS' U.S. Atlantic SARs. All values presented in table 2 are the most recent available. For more information, please see information presented in the SARs (available online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports).

\6\ This rule provides a single take estimate for the melon- headed whale, false killer whale, pygmy killer whale, and killer whale grouped together as the “blackfish.” This approach reflects the best available scientific information (Garrison et al., 2023). These species are encountered only occasionally during any given vessel survey, and these relatively infrequent encounters make it difficult to fit species-specific detection and habitat models. For each of these models, the authors detail analyses and decisions relevant to model development, as well as notes of caution regarding use of the models given the associated uncertainty resulting from development of a model based on few sightings. The Garrison et al. (2023) models are based on survey data from 2003 to 2019. Notably, surveys conducted after 2009 were conducted in “passing” mode, where the ship did not deviate from the trackline to approach and verify species identifications for detected marine mammal groups, resulting in an increase in observed marine mammal groups that could not be identified to species. As a result of these factors, the model authors determined it appropriate to develop a single spatial model based on sightings of unidentified blackfish, in addition to the relatively few sightings where species identification could be confirmed.

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In table 2 above, we report two sets of abundance estimates: those from NMFS' SARs and those predicted by habitat-based cetacean density models. Please see footnote 3 of table 2 for more detail. NMFS' SAR estimates are typically generated from the most recent shipboard and/or aerial surveys conducted. GOA oceanography is dynamic, and the spatial scale of the GOA is small relative to the ability of most cetacean species to travel. U.S. waters only comprise about 40 percent of the entire GOA, and 65 percent of GOA oceanic waters are south of the U.S. Exclusive Economic Zone (EEZ). Studies based on abundance and distribution surveys restricted to U.S. waters are unable to detect temporal shifts in distribution beyond U.S. waters that might account for any changes in abundance within U.S. waters. NMFS' SAR estimates also in some cases do not incorporate correction for detection bias. Therefore, for cryptic or long-diving species (e.g., beaked whales, Kogia spp., sperm whales), estimates should generally be considered underestimates (see footnotes 5 and 7 of table 2).

The model-based abundance estimates represent the output of predictive models derived from multi-year observations and associated environmental parameters and incorporate corrections for detection bias (the same models and data from which the density estimates are derived). Incorporating more data over multiple years of observation can yield different results in either direction, as the result is not as readily influenced by fine-scale shifts in species habitat preferences or by the absence of a species in the study area during a given year. NMFS' SAR abundance estimates show substantial year-to-year variability in some cases. Incorporation of correction for detection bias should systematically result in greater abundance predictions. For these reasons, the model-based estimates are generally more realistic and, for the purposes of assessing estimated exposures relative to abundance--used in this case to understand the scale of the predicted takes compared to the population--NMFS generally believes that the model-based abundance predictions are the best available information and most appropriate because they were used to generate the exposure estimates and therefore provide the most relevant comparison.

As part of our evaluation of the environmental baseline, which is considered as part of the negligible impact analysis, we consider any known areas of importance as marine mammal habitat. We also consider other relevant information, such as unusual mortality events (UME) and the 2010 Deepwater Horizon oil spill.

Habitat--Important habitat areas may include areas of known importance for reproduction, feeding, or migration, or areas where small and resident populations are known to occur. They may have independent regulatory status such as designated critical habitat for ESA-listed species (as defined by section 3 of the ESA) or be identified through other means (e.g., recognized Biologically Important Areas (BIA)).

No critical habitat has yet been designated for the Rice's whale, though a proposed rule to do so was published (88 FR 47453, July 24, 2023). The proposal references the same supporting information discussed herein in suggesting that GOA continental slope waters between 100 and 400 m water depth be designated as critical habitat. In addition, a BIA has been recognized since 2015 (LaBrecque et al., 2015). A detailed description of available information relating to Rice's whale habitat was provided in the notice of proposed rulemaking (91 FR 9014, February 24, 2026). That information is not repeated here; please see that notice for further information.

In summary, available data indicates the presence of a core habitat area in the northeastern GOA (outside the geographic scope of this rule), and the presence of Rice's whales in western and central GOA waters. In particular, passive acoustic data provide evidence that waters 100-400 m deep in the central and western GOA are Rice's whale habitat and are being used by Rice's whales in all seasons, although it remains unknown whether animals are moving between the northwestern and the northeastern GOA or whether these represent different groups of animals (Soldevilla et al., 2022).

Additional recent data continues to show calling activity in the western GOA, with whales acoustically present between 20 and 50 percent of recording days across multiple sites off Texas (Debich et al., 2025a, b). Furthermore, updated photo-identification catalogs suggest potential movement of individuals in and out of the core area, though sightings outside this region remain rare (Aichinger Dias et al., 2025). While these data refine our understanding of the species' range, this information does not reveal information on range different from those previously analyzed.

The available information is consistent with the predictions of Rice's whale density modeling, on which basis NMFS has anticipated and evaluated the potential for and effects of takes of Rice's whale in western and central GOA waters. Little is known about the number of whales that may be present, the nature of these individuals' use of the habitat, or the timing, duration, or frequency of occurrence for individual whales. Conversely, the importance of northeastern GOA waters to Rice's whale recovery is clear (Rosel et al., 2016). A comparison of acoustic and sightings data from the central/western and eastern GOA, even acknowledging the limitations of those data, suggests that occurrence of whales in the northeastern GOA core habitat is

significantly greater and that the area provides the habitat of greatest importance to the species.

Deepwater Horizon Oil Spill--In 2010, the Macondo well blowout and explosion aboard the Deepwater Horizon drilling rig (also known as the Deepwater Horizon explosion, oil spill, and response; hereafter referred to as the DWH oil spill) caused oil, natural gas, and other substances to flow into the GOA for 87 days before the well was sealed. Total oil discharge was estimated at 3.19 million barrels (134 million gallons), resulting in the largest marine oil spill in history (DWH NRDA Trustees, 2016). In addition, the response effort involved extensive application of dispersants at the seafloor and at the surface, and controlled burning of oil at the surface was also used extensively as a response technique. The oil, dispersant, and burn residue compounds continue to present ecological challenges in the region. NMFS discussed the impacts of the DWH oil spill on marine mammals in detail in its 2018 notice of proposed rulemaking (83 FR 29212; June 22, 2018), and we refer the reader to that document for additional detail. The 2018 proposed rule provided detailed discussion of the DWH oil spill. Comprehensive monitoring programs (2020-2025) led by NMFS' Southeast Fisheries Science Center and partners have provided updated further insights into post-DWH cetacean distribution and density (Frasier et al., 2024a, b). Recent analysis indicates that many species continue to exhibit densities significantly below pre-spill levels, suggesting a lack of recovery for affected populations. Estimates of annual mortality for many stocks over the period 2014-2018 include mortality attributed to the effects of the DWH oil spill (see table 2) (Hayes et al., 2023), and these mortality estimates are considered as part of the environmental baseline. NMFS similarly treats the effects of the DWH oil spill as part of the baseline in considering the likely resilience of these populations to the effects of the activities considered in this final rule.

Hearing is the most important sensory modality for marine mammals underwater, and exposure to anthropogenic sound can have deleterious effects. To appropriately assess the potential effects of exposure to sound, it is necessary to understand the frequency ranges marine mammals are able to hear. Not all marine mammal species have equal hearing capabilities (e.g., Richardson et al., 1995; Wartzok and Ketten, 1999; Au and Hastings, 2008). To reflect this, Southall et al. (2007, 2019) recommended that marine mammals be divided into hearing groups based on directly measured (behavioral or auditory evoked potential techniques) or estimated hearing ranges (behavioral response data, anatomical modeling, etc.). Generalized hearing ranges were chosen based on the ~65 decibel (dB) threshold from composite audiograms, previous analyses in NMFS (2018), and/or data from Southall et al. (2007) and Southall et al. (2019). [GRAPHIC] [TIFF OMITTED] TR17AP26.033

For more detail concerning these groups and associated frequency ranges, please see NMFS (2024) for a review of available information.

Potential Effects of the Specified Activities on Marine Mammals and Their Habitat

In NMFS' notice of proposed rulemaking (91 FR 9014, February 24, 2026), this section (Potential Effects) included a comprehensive summary and discussion of the ways that the specified activity may impact marine mammals and their habitat, including general background information on sound and specific discussion of potential effects to marine mammals from noise produced through use of the acoustic sources considered herein. We do not repeat that discussion here,

instead referring the reader to the notice of proposed rulemaking.

The Estimated Take section that follows includes a quantitative analysis of the number of individuals that are expected to be taken by the specified activity. The Negligible Impact Analysis and Determinations section includes an analysis of how these activities will impact marine mammals and considers the analysis of Potential Effects presented in the notice of proposed rulemaking, the Estimated Take section, and the Mitigation section, to draw conclusions regarding the likely impacts of these activities on the reproductive success or survivorship of individuals and whether those impacts are reasonably expected to, or reasonably likely to, adversely affect the species or stock through effects on annual rates of recruitment or survival.

This section provides an estimate of the numbers and type of incidental takes that may be expected to occur under the specified activity, which informs NMFS' negligible impact determinations. Realized incidental takes would be determined by the actual levels of activity at specific times and places that occur under any issued LOAs and by the actual acoustic sources used. Take estimates are available for the three different airgun array configurations described previously. The highest modeled estimated take (annual and 5-year total) for each species is analyzed for the negligible impact analysis.

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). Harassment is the only type of take expected to result from these activities. It is unlikely that lethal takes would occur even in the absence of the mitigation and monitoring measures, and no such takes are anticipated or will be authorized.

Anticipated takes would primarily be by Level B harassment, as use of the described acoustic sources, particularly airgun arrays, is likely to disrupt behavioral patterns of marine mammals upon exposure to sound at certain levels. There is also some potential for auditory injury (Level A harassment) to result for LF and VHF species due to the size of the predicted auditory injury zones for those species, though none is predicted to occur for Rice's whales (the only LF cetacean in the GOA). NMFS does not expect auditory injury to occur for HF species. Detailed discussion of this determination was provided in the Estimated take section of the notice of proposed rulemaking (91 FR 9014, February 24, 2026), and is not repeated here.

Below, we summarize how the take that may be authorized was estimated using acoustic thresholds, sound field modeling, and marine mammal density data. In addition to discussion provided below, please see associated companion documents available on NMFS' website, for additional detail (Zeddies et al., 2015, 2017a; Weirathmueller et al., 2022). A summary overview of the take estimation process, as well as full discussion related to the development of estimated take numbers, is provided below.

NMFS uses acoustic thresholds that identify the received level of underwater sound above which exposed marine mammals generally would be reasonably expected to exhibit disruption of behavioral patterns (Level B harassment) or to incur AUD INJ of some degree (Level A harassment).

Level B Harassment--NMFS carries forward the approach to evaluation of potential take by Level B harassment used for the 2021 and 2024 final rules. Based on the practical need to use a relatively simple threshold based on available information that is both predictable and measurable for most activities, NMFS typically uses a generalized acoustic threshold based on received level to estimate the onset of Level B harassment (e.g., the historical 160 dB rms threshold for intermittent sources, which include the impulsive sources evaluated herein). In this case, NMFS identified a more complex probabilistic risk function for use in evaluating the potential effects of the specified activity. This function, first described in Wood et al. (2012), differs from the single-step 160 dB rms criterion primarily by acknowledging the potential for Level B harassment at exposures to received levels below 160 dB rms as well as the potential that animals exposed to received levels above 160 dB rms will not respond in ways constituting Level B harassment. The approach described by Wood et al. (2012) also accounts for differential hearing sensitivity by incorporating the Type I frequency-weighting functions described by Southall et al. (2007). The broader Type I filters are appropriately retained for use in evaluating potential behavioral disturbance in conjunction with the probabilistic response function. The criteria are described in table 4. [GRAPHIC] [TIFF OMITTED] TR17AP26.034

Level A harassment--Modeling supporting the 2021 and 2024 final rules relied on NMFS' Revised Technical Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammal Hearing (Version 2.0; NMFS, 2018) (table 5). Since issuance of those rules, NMFS completed Updated Technical Guidance (NMFS, 2024) (table 6). Both versions of the technical guidance identify dual criteria, using the cumulative sound exposure level metric and peak sound pressure level metric, 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). This final rule carries forward the modeling and resulting take estimates (as updated for the 2024 rule) based on the 2018 Technical Guidance (NMFS, 2018), based on our determination that those estimates of Level A harassment remain sufficiently representative of any incidents of Level A harassment that

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These thresholds are provided in tables 5 and 6. The references, analysis, and methodology used in the development of the thresholds are described in NMFS' 2018 Revised Technical Guidance and NMFS' 2024 Updated Technical Guidance, both of which may be accessed at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance. The specified activity considered herein includes the use of impulsive seismic sources (i.e., airguns). [GRAPHIC] [TIFF OMITTED] TR17AP26.036

In summary, the peak pressure threshold for LF cetaceans increased by 3 dB, while the cumulative SEL threshold (upon which estimates of potential AUD INJ for LF cetaceans is based in this case) is unchanged. As discussed below, no Level A harassment is likely to occur for HF cetaceans, though we note that the cumulative SEL threshold for the hearing group increased by 8 dB. The peak pressure threshold for VHF cetaceans (upon which estimates of potential AUD INJ are based in this case) is unchanged, while the cumulative SEL threshold increased by 4 dB (see tables 5 and 6). Regarding the underlying frequency sensitivities, the generalized hearing range for LF cetaceans remains essentially the same (currently estimated as 7 Hz-36 kHz versus 7 Hz-35 kHz in the 2018 Technical Guidance), while the current HF cetacean hearing range is unchanged from that estimated for the previously named mid-frequency hearing group. The current VHF cetacean hearing range was changed more significantly, from 275 Hz-160 kHz (for the previously named HF hearing group) to 200 Hz-165 kHz (see table 3). However, because the potential for Level A harassment is best predicted by exposures above the peak pressure threshold for VHF cetaceans, the change to estimated hearing range, and changes to the auditory weighting function, are not relevant, i.e., frequency weighting is not a factor in evaluating exposures to peak pressure output from

airgun arrays. As the peak pressure threshold for this hearing group is unchanged, no change would be expected to the previously estimated instances of Level A harassment.

Although the operable cumulative SEL threshold for LF cetaceans is unchanged, frequency weighting is relevant to evaluations of potential exposure above the threshold. Changes to the LF cetacean weighting function would be expected to result in slight increases to estimated isopleth distances associated with the AUD INJ threshold, though these would remain smaller than the shutdown distance for Rice's whales (see Mitigation). The existing take estimates, which NMFS used for these ITRs, predict that no Level A harassment will occur for Rice's whales. Given the very low likelihood of injurious exposure for Rice's whales, in context of the mitigation requirements, NMFS has determined that the minor changes to the acoustic thresholds as a result of the 2024 Technical Guidance for LF cetaceans do not affect the likelihood of Level A harassment and, therefore, there is no need to update related quantitative estimates. There are no changes to the existing estimates of potential Level A harassment for any species.

Zeddies et al. (2015, 2017a) provided estimates of the annual marine mammal acoustic exposures exceeding the aforementioned criteria caused by sounds from geophysical survey activity in the GOA for 10 years of notional activity levels, using 8,000-in\3\ airguns and other sources, as well as full detail regarding the original acoustic exposure modeling conducted in support of BOEM's 2016 petition and NMFS' analysis in support of the 2021 final rule. Zeddies et al. (2017b) provided information regarding source and propagation modeling related to the 4,130-in\3\ airgun array, and Weirathmueller et al. (2022) provide detail regarding the modeling performed for the 5,110- in\3\ airgun array. For full details of the modeling effort, see the reports (available online at: https://www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-gulf-mexico) and review additional, detailed discussion provided in the notice of proposed rulemaking (91 FR 9014, February 24, 2026), which we do not repeat.

The modeling effort produced exposure estimates computed from modeled sound levels as received by animats in a specific modeling area. The GOA was divided into seven modeling zones with six survey types simulated within each zone to estimate the potential effects of each survey: shelf and slope waters were divided into eastern, central, and western zones, plus a single deep-water zone, to account for both the geospatial dependence of acoustic fields and the geographic variations of animal distributions. Survey types included deep penetration surveys using a large airgun array (2D, 3D NAZ, 3D WAZ, and coil survey types), shallow penetration surveys using a single airgun, and high resolution surveys. We do not discuss HRG surveys further, as they are not considered likely to result in incidental take of marine mammals.

The results from each zone were summed to provide GOA-wide estimates of take for each marine mammal species for each survey type for each notional year. To get these annual aggregate exposure estimates, 24-hr average exposure estimates from each survey type were multiplied by the number of expected survey days from BOEM's effort projections. Because these projections are not season-specific, surveys were assumed to be equally likely to occur at any time of the year and at any location within a given zone.

Marine Mammal Density Information--The best available scientific information was considered in conducting marine mammal exposure estimates (the basis for estimating take). This information consists of habitat-based cetacean density models produced by NMFS' Southeast Fisheries Science Center (Garrison et al., 2023). These models incorporate survey data from 2003 through 2019 including data from survey effort conducted during winter, allowing for increased temporal resolution of model predictions relative to previously available marine mammal density data. In addition, these are the first density models that incorporate survey data collected after the DWH oil spill. New models were produced for all taxa other than Fraser's dolphin and rough-toothed dolphin, as the model authors determined that there were too few detections of these species to support model development. Therefore, we rely on previously available models (Roberts et al., 2016) for these two species.

For species occurring in oceanic waters, the density models are based upon data collected during vessel surveys conducted in 2003-2004, 2009, and 2017-2018 (and surveys conducted in 2019 for Rice's whale). Survey effort was generally conducted in a survey region bounded by the shelf break (approximately the 200-m isobath) to the north and the boundary of the U.S. EEZ to the south. Separate models were created for species occurring in shelf waters (Atlantic spotted dolphin and bottlenose dolphin) based on seasonal aerial surveys conducted in 2011- 2012 and 2017-2018. Based on water depth, the shelf models were used to predict acoustic exposures for these two species in zones 2 and 3 (with zone 1 no longer part of the specified geographical region), and the oceanic models were used to predict exposures in zones 4-7.

As discussed above, the density modeling effort treats beaked whales and Kogia spp. as guilds, as sightings of these species are typically difficult to resolve to the species level. In addition, the model authors determined there to be too few sightings and/or too few sightings resolved to species level for the melon-headed whale, false killer whale, pygmy killer whale, and killer whale to produce individual species models. Instead, a single blackfish model was developed to produce guild-level predictions for these species (Garrison et al., 2023). Take Estimates

Exposure estimates above Level A and Level B harassment criteria, originally developed by Zeddies et al. (2015, 2017a, 2017b) and updated by Weirathmueller et al. (2022) in association with the activity projections for the various annual effort scenarios, were generated based on the specific modeling scenarios (including source and survey geometry), i.e., 2D survey (1 x source array), 3D NAZ survey (2 x source array), 3D WAZ survey (4 x source array), coil survey (4 x source array).

Level A Harassment--Here, we summarize acoustic exposure modeling results related to Level A harassment. Overall, there is a low likelihood of take by Level A harassment for any species, though the degree of this low likelihood is primarily influenced by the specific hearing group. For HF and VHF cetaceans, potential auditory injury would be expected to occur on the basis of instantaneous exposure to peak pressure output from an airgun array while for LF cetaceans, potential auditory injury would occur on the basis of the accumulation of energy output over time by an airgun array. Importantly, the modeled exposure estimates do not account for either aversion or the beneficial impacts of the required mitigation measures.

Of even greater import for HF cetaceans is that the small calculated Level A harassment zone size in conjunction with the properties of sound fields produced by arrays in the near field versus far field leads to a

logical conclusion that Level A harassment is so unlikely for species in this hearing group as to be discountable.

For HF cetaceans, the only potential injury zones will be based on the peak pressure metric, as such zones will be larger than those calculated on the basis of the cumulative SEL metric (which are essentially non-existent for HF and VHF cetaceans). The estimated zone size for the 230 dB peak threshold for HF cetaceans is only 18 m. In a theoretical modeling scenario, it is possible for animats to engage with such a small assumed zone around a notional point source and, subsequently, for these interactions to scale to predictions of real- world exposures given a sufficient number of predicted 24-hr survey days in confluence with sufficiently high predicted real-world animal densities. However, this is not a realistic outcome, as described in detail in the notice of proposed rulemaking (91 FR 9014, 9045, February 24, 2026).

As a result, for all HF cetaceans, following evaluation of the available scientific literature regarding the auditory sensitivity of HF cetaceans and the properties of airgun array sound fields, NMFS does not expect any reasonable potential for Level A harassment to occur. NMFS expects the potential for Level A harassment of HF cetaceans to be discountable, even before the likely moderating effects of aversion and mitigation are considered (e.g., Nachtigall et al., 2018), and NMFS does not believe that Level A harassment is a likely outcome for any HF cetacean. The modeling results provided by Weirathmueller et al. (2022) and relied upon herein account for this by assuming that any estimated exposures above Level A harassment thresholds for HF cetaceans resulted instead in Level B harassment (as reflected in table 7).

For LF and VHF species, NMFS carries forward its assumptions regarding the effects of aversion and the same approach and specific offset factor used in the 2021 final rule to adjust estimated instances of Level A harassment as a reasonable and likely conservative approach to addressing the issue of aversion. This adjustment was incorporated into the modeling results provided by Weirathmueller et al. (2022) and reflected in table 7. This approach and associated considerations are discussed in detail in the notice of proposed rulemaking (91 FR 9014, 9046, February 24, 2026).

For purposes of the negligible impact analyses, NMFS uses the maximum of the species-specific exposure modeling results from the three airgun array configurations/sizes. Specifically, for all species other than Rice's whale, these results are associated with the 8,000- in\3\ array. For the Rice's whale, modeling associated with the 5,110- in\3\ array produced larger exposure estimates (discussed below). These species-specific maximum estimates provide the upper bound of take that may be authorized under the rule, while actual take authorized through LOAs would be determined based on the appropriate source proxy (i.e., either 90-in\3\ single airgun or 4,130-, 5,110-, or 8,000-in\3\ airgun array).

Estimated instances of take, i.e., scenario-specific acoustic exposure estimates incorporating the adjustments to Level A harassment exposure estimates discussed here, are shown in table 7. This information regarding total number of takes (with Level A harassment takes based on assumptions relating to HF cetaceans in general as well as aversion), on an annual basis for 5 years, provides the bounds within which LOAs may be issued in association with this regulatory framework.

Typically, and especially in cases where PTS is predicted, NMFS anticipates that some number of individuals may incur temporary threshold shift (TTS). However, it is not necessary to separately quantify those takes, as it is unlikely that an individual marine mammal would be exposed at the levels and duration necessary to incur TTS without also being exposed to the levels associated with potential disruption of behavioral patterns (i.e., Level B harassment). As such, NMFS expects any potential TTS takes to be captured by the estimated Level B harassment takes associated with behavioral disturbance (discussed below). BILLING CODE 3510-22-P

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Modeling for the smaller, 5,110-in\3\ array illustrated that the larger array is not necessarily always more impactful. Free-field beam patterns are different for the arrays as are the tow depths. The 5,110- in\3\ array was specified as being towed at 12 m depth (following typical usage observed by NMFS through review of LOA applications), while the other arrays are assumed to use an 8-m tow depth (assumptions regarding source specifications were made by BOEM as part of its original petition for rulemaking). The depth at which a source is placed influences the interference pattern caused by the direct and sea-surface reflected paths (the “Lloyd's mirror” effect). The destructive interference from the sea-surface reflection is generally greater for shallow tow depths compared to deeper tow depths. In addition, interactions

between source depth, beam pattern geometry, source frequency content, the environment (e.g., bathymetry and sound velocity profile), and different animat seeding depths and behaviors can give unexpected results. For example, while the larger array may have the longest range for a particular isopleth (sound contour), the overall sound field coverage area was found to have greater asymmetry as a result of the above-mentioned interactions.

While the larger array did produce greater predicted exposures for all species, with the exception of Rice's whales, the differences between predicted exposure estimates for the two larger arrays are not as great as may have been expected on the basis of total array volume alone. The 5,110- and 8,000-in\3\ arrays are often similar in terms of predicted exposures, although the beam patterns are quite different. For arrays of airgun sources, the chamber volume or the total array volume is not the only meaningful variable. Although it is true that a source with a larger volume is generally louder, in practice this only applies largely to single sources or small arrays of sources and was not the case for the considered arrays. As discussed above, array configuration, tow depth, and bathymetry were significant factors. For example, the 8,000-in\3\ array generally had a more directional beam pattern than the 4,130- or 5,110-in\3\ arrays. The vertical structure of the sound field combined with different species' dive depth and surface intervals was important as well.

NMFS has determined the values shown in table 7 are a reasonable estimate of the maximum potential instances of take that may occur in each year of the regulations based on projected effort (more specifically, each of these “takes” represents a day in which one individual is exposed above the Level B harassment criteria, even if only for minutes). However, these take numbers do not represent the number of individuals expected to be taken, as they do not consider the fact that certain individuals may be exposed above harassment thresholds on multiple days. Accordingly, NMFS developed a “scalar ratio” approach to inform two important parts of the analyses: understanding a closer approximation of the number of individuals of each species or stock that may be taken within a survey, and understanding the degree to which individuals of each species or stock may be more likely to be repeatedly taken across multiple days within a year.

In order to determine more realistic exposure probabilities for individuals across multiple days, modeled results were compared for a 30-day period versus the aggregation of 24-hr population reset intervals to determine a species-typical offset of modeled daily exposures. When conducting computationally-intensive modeling over the full assumed 30-day survey period (versus aggregating the smaller 24-hr periods for 30 days), results showed about 10-45 percent of the total number of takes calculated using a 24-hr reset of the population, with differences relating to species-typical movement and residency patterns. Given that many of the evaluated survey activities occur for 30-day or longer periods, particularly some of the larger surveys for which the majority of the modeled exposures occur, using such a scaling process is appropriate in order to evaluate the likely severity of the predicted exposures.

This approach was evaluated using six representative species/ guilds: Rice's whale, sperm whale, beaked whales, bottlenose dolphin, Kogia spp., and short-finned pilot whale. For purposes of this analysis, bottlenose dolphin was used as a proxy for other small dolphin species, and short-finned pilot whale was used as a proxy for other large delphinids. Information regarding the number of modeled animals receiving exposure above criteria for average 24-hr sliding windows scaled to the full 30-day duration and percent change in comparison to the same number evaluated when modeling the full 30-day duration was used to derive the aforementioned 30-day scalar ratios which, when applied to the total instances of take given in table 7, captures repeated takes of individuals at a 30-day sampling level. Scalar ratios are as follows: Rice's whale, 0.189; sperm whale, 0.423; beaked whales, 0.101; bottlenose dolphin, 0.287; Kogia spp., 0.321; and short-finned pilot whale, 0.295. Application of the re-scaling method reduced the overall magnitude of modeled takes for all species by slightly more than double to up to ten-fold (table 8).

In summary, comparing the results of modeling simulations that more closely match longer survey durations (30 days) to the results of 24- hour take estimates scaled up to 30 days (as the instances of take in table 7 were calculated) provides the comparative ratios of the numbers of individuals taken/calculated (within a 30-day survey) to instances of take, in order to better understand the comparative distribution of exposures across individuals of different species. These products are used to inform a better understanding of the nature in which individuals are taken across the multiple days of a longer duration survey given the different behaviors that are represented in the animat modeling and may appropriately be used in combination with the calculated instances of take to predict the number of individuals taken for surveys of similar duration, in order to support evaluation of take estimates in requests for LOAs under the “small numbers” standard, which is based on the number of individuals taken. Application of the scaling method reduced the overall magnitude of modeled takes for all species by a range of slightly more than double up to tenfold (table 8).

These adjusted take numbers, representing a closer approximation of the number of individuals taken (shown in table 8), provide a more realistic basis upon which to evaluate severity of the expected taking. Please see the Negligible Impact Analysis and Determinations section later in this document for additional detail. It is important to recognize that while these scaled numbers better reflect the number of individuals likely to be taken within a single 30-day survey than the number of instances in table 7, they will still overestimate the number of individuals taken across the aggregated GOA activities, because they do not correct for (i.e., further reduce take to account for) individuals exposed to multiple surveys or fully correct for individuals exposed to surveys significantly longer than 30 days.

As noted in the beginning of this section and in the Small Numbers section, using modeled instances of take (table 7) and the method used here to scale those numbers allows one to more accurately predict the number of individuals that will be taken as a result of exposure to one survey and, therefore, these scaled predictions are more appropriate to consider in requests for LOAs to assess whether a resulting LOA would meet the small numbers standard. However, for the purposes of ensuring that the total taking authorized pursuant to all issued LOAs is within the scope of the analysis conducted to support the negligible impact finding in this rule, authorized instances of take (which are the building blocks of the analysis) also must be assessed. Specifically, reflecting table 7 and what has been analyzed, the total instances of take that may be authorized for any given species or stock over the course of the 5 years covered under these regulations must not, and are not expected to, exceed the sum of the 5 years of take indicated for the 5 years in that table. Additionally, in any given

year, the instances of take of any species must not, and are not expected to, exceed the highest annual take listed in table 7 for any of the 5 years for a given species. [GRAPHIC] [TIFF OMITTED] TR17AP26.038

Under section 101(a)(5)(A) of the MMPA, NMFS must set forth the permissible methods of taking pursuant to such activity, and other means of effecting the LPAI 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 subsistence uses, often referred to in shorthand as “mitigation.” NMFS does not have a regulatory definition for LPAI. However, NMFS' implementing 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 LPAI upon the affected species or stocks and their habitat (50 CFR 216.104(a)(11)). In the Mitigation section of the 2021 final rule, NMFS included a detailed description of our interpretation of the LPAI standard (including its relationship to the negligible impact standard) and how the LPAI standard is implemented (86 FR 5322, 5407, January 19, 2021). We refer readers to the full LPAI discussion in the 2021 final rule for additional information.

NMFS' evaluation of potential mitigation measures includes consideration of two primary factors:

(1) The manner in which, and the degree to which, implementation of the potential measure(s) is expected to reduce adverse impacts to marine mammal species or stocks, their habitat, and their availability for subsistence uses (where relevant). This analysis considers such things as the nature of the potential adverse impact (such as likelihood, scope, and range), the likelihood that the measure will be effective if implemented, and the likelihood of successful implementation; and

(2) The practicability of the measures for applicant implementation. Practicability of implementation may consider such things as cost, impact on activities, personnel safety, and practicality of implementation.

In carrying out the MMPA's mandate for this action, NMFS applies the context-specific balance between the manner in which and the degree to which measures are expected to reduce impacts to the affected species or stocks and their habitat and practicability for survey operators. The effects of concern (i.e., those with the potential to adversely impact species or stocks and their habitat) include auditory injury, severe behavioral reactions, disruptions of critical behaviors, and to a lesser degree, masking and impacts on acoustic habitat.

Mitigation prescribed in the 2021 rule and ITRs focused on measures with proven or reasonably presumed ability to avoid or reduce the intensity of acute exposures that have potential to result in these anticipated effects. To the extent of the information available to NMFS, in prescribing measures for the 2021 ITRs and in determining that the same measures meet the LPAI standard for this final rule, we considered practicability concerns, as well as potential undesired consequences of the measures, e.g., extended periods using the acoustic source due to the need to reshoot lines. NMFS recognizes that instantaneous protocols, such as shutdown requirements, are not capable of avoiding all acute effects, are not suitable for avoiding many cumulative or chronic effects, and do not provide targeted protection in areas of greatest importance for marine mammals. Therefore, in addition to a basic suite of seismic mitigation protocols, we also evaluated time-area restrictions that

would avoid or reduce both acute and chronic impacts of surveys.

In order to satisfy the MMPA's LPAI standard, NMFS evaluated a suite of basic mitigation protocols that are required regardless of the status of a stock. Additional or enhanced protections are required for species whose stocks are in particularly poor health and/or are subject to some significant additional stressor that lessens that stock's ability to weather the effects of the specified activities without worsening its status.

For purposes of defining mitigation requirements, we differentiate here between requirements for two classes of airgun survey activity: deep penetration and shallow penetration, with surveys using arrays greater than 1,500 in\3\ total airgun volume considered deep penetration. Shallow penetration surveys also include those using single airguns. A third general class of surveys is also considered, referred to here as HRG surveys and includes those surveys using the other electromechanical sources described previously. Below, mitigation requirements are described in detail.

Monitoring by dedicated, trained marine mammal observers is required in all water depths and, for certain surveys, observers must be independent. Additionally, for some surveys, NMFS requires that some PSOs have prior experience in the role. Independent observers are employed by a third-party observer provider; vessel crew may not serve as PSOs when independent observers are required. Dedicated observers are those who have no tasks other than to conduct observational effort, record observational data, and communicate with and instruct the survey operator (i.e., vessel captain and crew) with regard to the presence of marine mammals and mitigation requirements. Trained PSOs have successfully completed an approved PSO training course (see Monitoring and Reporting), and experienced PSOs have additionally gained a minimum of 90 days at-sea experience working as a PSO during a deep penetration seismic survey, with no more than 18 months having elapsed since the conclusion of the relevant at-sea experience. Training and experience is specific to either visual or acoustic PSO duties (where required). An experienced visual PSO must have completed approved, relevant training and must have gained the requisite experience working as a visual PSO. An experienced acoustic PSO must have completed a PAM operator training course and must have gained the requisite experience working as an acoustic PSO. Hereafter, we also refer to acoustic PSOs as PAM operators, whereas when we use “PSO” without a qualifier, the term refers to either visual PSOs or PAM operators (acoustic PSOs).

NMFS does not formally administer any PSO training program or endorse specific providers but will approve PSOs that have successfully completed courses that meet the curriculum and trainer requirements specified herein (see Monitoring and Reporting). NMFS will provide PSO approvals in the context of the need to ensure that PSOs have the necessary training to carry out their duties competently while also approving applicant staffing plans quickly. In order for PSOs to be approved, NMFS must review and approve PSO resumes indicating successful completion of an acceptable training course. A PSO may be trained and/or experienced as both a visual PSO and PAM operator and may perform either duty, pursuant to scheduling requirements. Where multiple PSOs are required and/or PAM operators are required, PSO watch schedules shall be devised in consideration of the following restrictions: (1) a maximum of 2 consecutive hours on watch followed by a break of at least 1 hour between watches for visual PSOs; (2) a maximum of 4 consecutive hours on watch followed by a break of at least 2 consecutive hours between watches for PAM operators; and (3) a maximum of 12 hours observation per 24-hour period. NMFS may grant an exception for the requirement that visual PSOs be limited to a maximum of 2 consecutive hours on watch followed by a break of at least 1 hour between watches if requested on the basis of practicability concerns by LOA applicants. If an exception is granted, visual PSOs would instead be limited to a maximum of 4 consecutive hours on watch followed by a break of at least 2 hours between watches. Further information regarding PSO requirements may be found in the Monitoring and Reporting section, later in this document.

Deep Penetration Surveys--During deep penetration survey operations (e.g., any day on which use of the acoustic source is planned to occur; whenever the acoustic source is in the water, whether activated or not), a minimum of two independent PSOs must be on duty and conducting visual observations at all times during daylight hours (i.e., from 30 minutes prior to sunrise through 30 minutes following sunset).

All source vessels must carry a minimum of one experienced visual PSO, who shall be designated as the lead PSO, coordinate duty schedules and roles,\7\ and serve as the primary point of contact for the operator. The lead PSO shall determine the most appropriate observation posts that will not interfere with navigation or operation of the vessel while affording an optimal, elevated view of the sea surface. These should be the highest elevation available on each vessel, with the maximum viewable range from the bow to 90 degrees to port or starboard of the vessel. PSOs shall coordinate to ensure 360[deg] visual coverage around the vessel, and shall conduct visual observations using binoculars and the naked eye while free from distractions and in a consistent, systematic, and diligent manner. All source vessels must be equipped with pedestal-mounted “bigeye” binoculars that will be available for PSO use. Within these broad outlines, the lead PSO and PSO team will have discretion to determine the most appropriate vessel- and survey-specific system for implementing effective marine mammal observational effort. Any observations of marine mammals by crew members aboard any vessel associated with the survey, including receiver or chase vessels, should be relayed to the source vessel(s) and to the PSO team.

\7\ The coordination of PSO duty schedules and roles may alternatively be performed by a third-party, shore-based Monitoring Coordinator.

All source vessels must use a towed PAM system for potential detection of marine mammals at all times when operating the sound source in waters deeper than 100 m. The term “towed PAM system” refers to any combination of hardware and software that uses a towed array for operations. The system must be monitored at all times during use of the acoustic source, and acoustic monitoring must begin at least 30 minutes prior to ramp-up. PAM operators must be independent, and all source vessels shall carry a minimum of two experienced PAM operators. PAM operators shall communicate all detections to visual PSOs, when visual PSOs are on duty, including any determination by the PSO regarding species identification, distance and bearing, and the degree of confidence in the determination. Further detail regarding PAM system requirements may be found in the Monitoring and Reporting section, later in this document.

Visual monitoring must begin at least 30 minutes prior to ramp-up (described below) and must continue until 1 hour after use of the acoustic source ceases or until 30 minutes past sunset. If any marine mammal is observed at any

distance from the vessel, a PSO would record the observation and monitor the animal's position (including latitude/longitude of the vessel and relative bearing and estimated distance to the animal) until the animal dives or moves out of visual range of the observer. A PSO would continue to observe the area to watch for the animal to resurface or for additional animals that may surface in the area. Visual PSOs shall communicate all observations to PAM operators, including any determination by the PSO regarding species identification, distance, and bearing and the degree of confidence in the determination.

As noted previously, all source vessels must carry a minimum of one experienced visual PSO and two experienced PAM operators. The observer designated as lead PSO (including the full team of visual PSOs and PAM operators) must have experience as a visual PSO. The applicant may determine how many additional PSOs are required to adequately fulfill the requirements specified here. To summarize, these requirements are: (1) 24-hour acoustic monitoring during use of the acoustic source in waters deeper than 100 m; (2) visual monitoring during use of the acoustic source by two PSOs during all daylight hours; (3) maximum of 2 consecutive hours on watch followed by a minimum of 1 hour off watch for visual PSOs and a maximum of 4 consecutive hours on watch followed by a minimum of 2 consecutive hours off watch for PAM operators; and (4) maximum of 12 hours of observational effort per 24-hour period for any PSO, regardless of duties.

Shallow Penetration Surveys--During shallow penetration surveys, operators must follow the same requirements described above for deep penetration surveys, with one notable exception: The use of PAM is not required.

HRG Surveys--HRG survey protocols differ from the previously described protocols for deep and shallow penetration surveys, and we differentiate between deep-water (greater than 100 m) and shallow-water HRG surveys. Water depth in the GOA provides a reliable indicator of the marine mammal fauna that may be encountered and, therefore, the complexity of likely observations and concern related to potential effects on deep-diving and/or sensitive species.

Deep-water HRG surveys are required to employ a minimum of one independent visual PSO during all daylight operations, in the same manner as was described for deep and shallow penetration surveys. Shallow-water HRG surveys are required to employ a minimum of one visual PSO, which may be a crew member. PSOs employed during shallow- water HRG surveys are only required during a pre-clearance period. PAM is not required for any HRG survey.

PAM Malfunction--Survey activity may continue for brief periods of time when the PAM system malfunctions or is damaged. Activity may continue for 30 minutes without PAM while the PAM operator diagnoses the issue. If the diagnosis indicates that the PAM system must be repaired to solve the problem, operations may continue for an additional 2 hours without acoustic monitoring under the following conditions:

Daylight hours and sea state is less than or equal to Beaufort sea state (BSS) 4;

No marine mammals (excluding delphinids; see below) detected solely by PAM in the exclusion zone (see below) in the previous 2 hours;

NMFS is notified via email as soon as practicable with the time and location in which operations began without an active PAM system; and

Operations with an active acoustic source, but without an operating PAM system, do not exceed a cumulative total of 4 hours in any 24-hour period.

An exclusion zone is a defined area within which occurrence of a marine mammal triggers mitigation action intended to reduce the potential for certain outcomes such as auditory injury or more severe disruption of behavioral patterns. For deep penetration surveys, the PSOs shall establish and monitor a 500-m exclusion zone and additional 500-m buffer zone (total 1,000 m) during the pre-clearance period (see below) and a 500-m exclusion zone during the ramp-up and operational periods (see below for description of extended 1,500-m zone in special circumstances). PSOs should generally focus their observational effort within a 1.5-km zone, to the extent possible, with animals observed at greater distances recorded and mitigation action taken as necessary (see below). For shallow penetration surveys, the PSOs shall establish and monitor a 100-m exclusion zone with additional 100-m buffer (total 200-m zone) during the pre-clearance period and a 100-m exclusion zone during the ramp-up (for small arrays only, versus single airguns) and operational periods (see below for description of extended 500-m zone in special circumstances). PSOs should generally focus their observational effort within a 500-m zone, to the extent possible, with animals observed at greater distances recorded and mitigation action taken as necessary (see below). These zones shall be based upon radial distance from any element of the airgun array (rather than being based on the center of the array or around the vessel itself). During use of the acoustic source, occurrence of marine mammals within the buffer zone (but outside the exclusion zone) should be communicated to the operator to prepare for the potential shutdown of the acoustic source. Use of the buffer zone in relation to ramp-up is discussed below under “Ramp-up.” Further detail regarding the exclusion zone and shutdown requirements is given under “Exclusion Zone and Shutdown Requirements.”

Ramp-up of an acoustic source is intended to provide a gradual increase in sound levels, enabling animals to move away from the source if the signal is sufficiently aversive prior to its reaching full intensity. Ramp-up is required for all surveys using airgun arrays.

The ramp-up procedure involves a step-wise increase in the number of airguns firing and total array volume until all operational airguns are activated and the full volume is achieved. Ramp-up is required at all times as part of the activation of the acoustic source (including source tests; see “Miscellaneous Protocols” for more detail) and may occur at times of poor visibility, assuming appropriate acoustic monitoring with no detections in the 30 minutes prior to beginning ramp-up. Acoustic source activation may only occur at night where operational planning cannot reasonably avoid such circumstances. Ramp- up must occur at night following acoustic source deactivation due to line turn or mechanical difficulty. The operator must notify a designated PSO of the planned start of ramp-up as agreed-upon with the lead PSO; the notification time should be at least 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.

Ramp-up begins by activating a single airgun (i.e., array element) of the smallest volume in the array. Ramp-up continues in stages by doubling the number of active elements at the commencement of each stage, with each stage of approximately the same duration. Total duration should not be less than approximately 20 minutes but maximum duration is not prescribed

and will vary depending on the total number of stages. There will generally be one stage in which doubling the number of elements is not possible because the total number is not even. This should be the last stage of the ramp-up sequence. The operator must provide information to the PSO documenting that appropriate procedures were followed. This approach is intended to ensure a perceptible increase in sound output per increment while employing increments that produce similar degrees of increase at each step.

For deep penetration surveys, PSOs must monitor a 1,000-m zone (or to the distance visible if less than 1,000 m) for a minimum of 30 minutes prior to ramp-up (i.e., pre-clearance). For shallow penetration surveys, PSOs must monitor a 200-m zone (or to the distance visible if less than 200 m) for a minimum of 30 minutes prior to ramp-up or start- up (for single airgun or non-airgun surveys; note that extended distance shutdowns, discussed below, may be required if certain species or circumstances are detected within greater distances: 1.5 km for deep penetration surveys and 500 m for shallow penetration surveys). The pre-clearance period may occur during any vessel activity (i.e., transit, line turn). Ramp-up must be planned to occur during periods of good visibility when possible; operators may not target the period just after visual PSOs have gone off duty. Following deactivation of the source for reasons other than mitigation, the operator must communicate the near-term operational plan to the lead PSO with justification for any planned nighttime ramp-up. Ramp-up may not be initiated if any marine mammal is within the designated zone. If a marine mammal is observed within the zone during the pre-clearance period, ramp-up may not begin until the animal(s) has been observed exiting the zone or until an additional time period has elapsed with no further sightings (i.e., 15 minutes for small delphinids and 30 minutes for all other species). PSOs will monitor the exclusion zone during ramp-up, and ramp-up must cease and the source shut down upon observation of marine mammals within or approaching the zone.

Deep Penetration Surveys--The PSOs must establish a minimum exclusion zone with a 500-m radius as a perimeter around the outer extent of the airgun array (rather than being delineated around the center of the array or the vessel itself). If a marine mammal (other than the small delphinid species discussed below) appears within or enters this zone, the acoustic source must be shut down (i.e., power to the acoustic source must be immediately turned off). If a marine mammal is detected acoustically, the acoustic source must be shut down, unless the PAM operator is confident that the animal detected is outside the exclusion zone or that the detected species is not subject to the shutdown requirement (see below).

The 500-m radial distance of the standard exclusion zone is expected to contain sound levels exceeding peak pressure injury criteria for all hearing groups other than, potentially, VHF cetaceans, while also providing a consistent, reasonably observable zone within which PSOs would typically be able to conduct effective observational effort. Although significantly greater distances may be observed from an elevated platform under good conditions, NMFS believes that 500 m is likely regularly attainable for PSOs using the naked eye during typical conditions. In addition, an exclusion zone is expected to be helpful in avoiding more severe behavioral responses. Behavioral response to an acoustic stimulus is determined not only by received level but by context (e.g., activity state) including, importantly, proximity to the source (e.g., Southall et al., 2007; Ellison et al., 2012; DeRuiter et al., 2013). In prescribing an exclusion zone, NMFS seeks not only to avoid most potential auditory injury but also to reduce the likely severity of the behavioral response at a given received level of sound.

In summary, NMFS' goal in prescribing a standard exclusion zone distance is to (1) encompass zones for most species within which auditory injury could occur on the basis of instantaneous exposure; (2) provide 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) enable more effective implementation of required mitigation by providing consistency and ease of implementation for PSOs, who need to monitor and implement the exclusion zone; and (4) define a distance within which detection probabilities are reasonably high for most species under typical conditions. NMFS' use of 500 m as the zone is not based directly on any quantitative understanding of the range at which auditory injury would be entirely precluded or any range specifically related to disruption of behavioral patterns. Rather, we believe it is a reasonable combination of factors. This zone has been proven as a feasible measure through past implementation by operators in the GOA. In summary, a practicable criterion such as this has the advantage of familiarity and simplicity while still providing in most cases a zone larger than relevant auditory injury zones, given realistic movement of source and receiver. Increased shutdowns, without a firm idea of the outcome the measure seeks to avoid, simply displace survey activity in time and increase the total duration of acoustic influence as well as total sound energy in the water (due to additional ramp-up and overlap where data acquisition was interrupted). The shutdown requirement described here would be required for most marine mammals, with certain differences. Small delphinids are excepted from the shutdown requirement, as described in the following section. Certain species are subject to an extended distance shutdown zone, as described in the subsequent section entitled “Other Shutdown Requirements.”

Dolphin Exception--The shutdown requirement described above is in place for all marine mammals, with the exception of small delphinids. As defined here, the small delphinid 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). Here we refer to “large delphinids” and “small delphinids” as shorthand for generally deep- diving versus surface-dwelling/bow-riding groups, respectively, as the important distinction is their dive behavior rather than their size. This exception to the shutdown requirement applies solely to specific genera of dolphins--Steno, Tursiops, Stenella, and Lagenodelphis (see table 2)--and applies under all circumstances, regardless of what the perception of the animal(s) behavior or intent may be. Please see the notice of proposed rulemaking for additional detailed discussion of the rationale for the dolphin exception (91 FR 9014, February 24, 2026), which is not repeated here.

Other Surveys--Shutdown protocols for shallow penetration surveys are similar to those described for deep penetration surveys, except that the exclusion zone is defined as a 100-m radial distance around the perimeter of the acoustic source. The small delphinid exception described above for deep penetration surveys would apply. As described previously, no shutdowns would be required for HRG surveys.

Extended Shutdown Requirements for Special Circumstances--Shutdown of the acoustic source is also required in the event of certain other detections beyond the standard exclusion zones. As for normal shutdowns within the standard exclusion zone, shutdowns at extended distance should be made on the basis of confirmed detections (visual or acoustic) within the zone. For deep penetration surveys, NMFS determined an appropriate distance on the basis of available information regarding detection functions for relevant species, but notes that, while based on quantitative data, the distance is an approximate limit that is merely intended to encompass the region within which we would expect a relatively high degree of success in sighting certain species while also improving PSO efficacy by removing the potential that a PSO might interpret these requirements as demanding a focus on areas further from the vessel. NMFS set the shutdown radius for special circumstances (described below) at 1.5 km for deep penetration surveys and 500 m for shallow penetration surveys.

Circumstances justifying shutdown at extended distance (i.e., 1.5 km for deep penetration surveys and 500 m for shallow penetration surveys) include (please see the notice of proposed rulemaking for rationale for each of these circumstances):

Upon detection of a Rice's whale.

Upon detection of a sperm whale.

Upon detection of a beaked whale or Kogia spp.

Shutdown Implementation Protocols--Any PSO on duty has the authority to delay the start of survey operations or to call for shutdown of the acoustic source. When shutdown is called for by a PSO, the acoustic source must be immediately deactivated and any dispute resolved only following deactivation. The survey operator must establish and maintain clear lines of communication directly between PSOs on duty and crew controlling the acoustic source to ensure that shutdown commands are conveyed swiftly while allowing PSOs to maintain watch. When both visual PSOs and PAM operators are on duty, all detections must be immediately communicated to the remainder of the on- duty team for potential verification of visual observations by the PAM operator or of acoustic detections by visual PSOs and initiation of dialogue as necessary. When there is certainty regarding the need for mitigation action on the basis of either visual or acoustic detection alone, the relevant PSO(s) must call for such action immediately.

Upon implementation of shutdown, the source may be reactivated after the animal(s) has been observed exiting the exclusion zone or following a 30-minute clearance period with no further detection of the animal(s).

If the acoustic source is shut down for reasons other than mitigation (e.g., mechanical difficulty) for brief periods (i.e., less than 30 minutes), it may be activated again without ramp-up if PSOs have maintained constant observation (including acoustic observation, where required) and no visual detections of any marine mammal have occurred within the relevant exclusion zone and no acoustic detections have occurred (when required). NMFS defines “brief periods” in keeping with other clearance watch periods and to avoid unnecessary complexity in protocols for PSOs. For any longer shutdown (e.g., during line turns), pre-clearance watch and ramp-up are required. For any shutdown at night or in periods of poor visibility (e.g., BSS 4 or greater), ramp-up is required but if the shutdown period was brief and constant observation maintained, pre-clearance watch is not required.

NMFS requires the same coastal restriction included in the 2021 ITRs to provide enhanced protection for northern coastal bottlenose dolphins, and discusses the potential for a restriction area for Rice's whales below. For all other species, there are no known specific areas of particular importance to consider for time-area restrictions, and no new information to suggest that the standard operational mitigation requirements in the 2021 ITRs are not sufficient and should be changed to meet the LPAI standard.

Coastal Restriction--No airgun surveys may occur from 90[deg] to 84[deg] W long. (as truncated through removal of the GOMESA moratorium area) and shoreward of a line indicated by the 20-m isobath, during the months of January through May. Waters shoreward of the 20-m isobath, where coastal dolphin stocks occur, represent the areas of greatest abundance for bottlenose dolphins.

The restriction is intended specifically to avoid additional stressors to the northern coastal stock of bottlenose dolphins during the time period believed to be of greatest importance as a reproductive period. NOAA estimates that potentially 82 percent of northern coastal dolphins were exposed to DWH oil, resulting in an array of long-term health impacts (including reproductive failure) and possible population reductions of 50 percent for the stock (DWH MMIQT, 2015). The same analysis estimated that these population-level impacts could require 39 years to recovery, in the absence of other additional stressors. The stock has been the subject of multiple declared UMEs.

The January-May timeframe is intended to best encompass the most important reproductive period for bottlenose dolphins in these coastal waters, when additional stress is most likely to have serious impacts on pregnancy and/or survival of neonates. Expert interpretation of the long-term data for neonate strandings is that February-April are the primary months that animals are born in the northern GOA, and that fewer but similar numbers are born in January and May. This refers to long-term averages and in any particular year the peak reproductive period can shift earlier or later.

Rice's Whale--For this final rule, NMFS evaluated the potential for a restriction on survey activity in areas between 100 and 400 m in depth throughout the geographic area covered by the rule for Rice's whales. We first provide a summary of baseline information relevant to our consideration of mitigation for Rice's whales. Rice's whales have a small population size, are restricted to the GOA, and were determined by the status review team to be “at or below the near-extinction population level” (Rosel et al., 2016). While various population abundance estimates are available (e.g.,

Garrison et al., 2020, 2023; Hayes et al., 2023; Roberts et al., 2016; Dias and Garrison, 2016), all are highly uncertain because targeted surveys have not been conducted throughout the Rice's whale's range. The most recent statistically-derived abundance estimate, from 2017 and 2018 surveys in the northeastern GOA, is 51 individuals (20-130 95% Confidence Interval (CI)) (Garrison et al., 2020). There may be fewer than 100 individuals throughout the GOA (Rosel et al., 2016). In addition, the population exhibits very low levels of genetic diversity (Rosel and Wilcox, 2014; Rosel et al., 2021). The small population size, restricted range, and low genetic diversity alone place these whales at significant risk of extinction (IWC, 2017). This risk has been exacerbated by the effects of the DWH oil spill, which was estimated to have exposed up to half the population to oil (DWH NRDA Trustees, 2016; DWH MMIQT, 2015). In addition, Rice's whales face a significant suite of anthropogenic threats, including noise produced by airgun surveys (Rosel et al., 2016). Additionally, Rice's whale dive and foraging behavior places them at heightened risk of being struck by vessels and/or entangled in fishing gear (Soldevilla et al., 2017).

Of relevance here, the geographic scope of the specified activity for this final rule excludes the eastern GOA through BOEM's earlier removal of the GOMESA area (see figure 1). This reduced scope effectively minimizes potential impacts to Rice's whales and their core habitat.

It is in the aforementioned context that we evaluated restriction of survey activity over a broad area of the central and/or western GOA within Rice's whale habitat in waters between the 100 and 400 m isobaths. There is no scientific information supporting a temporal component for any potential restriction nor any specific spatial definition for a central and/or western GOA restriction.

The amount of anticipated take of Rice's whales over the 5-year duration of the ITRs is relatively low and limited to Level B harassment. The anticipated magnitude of impacts from any of these anticipated takes is considered to be relatively low, as we concluded that none of these takes are expected to impact the fitness of any individuals. See Negligible Impact Analysis and Determinations. We also note the robust required shutdown measures that utilize highly effective visual and passive acoustic detection methods to avoid marine mammal injury as well as minimize TTS and more severe behavioral responses.

For this rulemaking, NMFS examined the potential for area-based restrictions in the context of the LPAI standard to determine whether a restriction is warranted to minimize the impacts from seismic survey activities on the affected marine mammal species or stocks. This analysis is consistent with the consideration of the LPAI criteria described above when determining appropriateness of mitigation measures. These potential measures were evaluated (see below) in the context of the seismic survey activities (including the geographic scope of the rule) and the other existing mitigation measures that would be implemented to minimize impacts on the affected marine mammal species or stocks from these activities.

To reiterate, the geographic scope of the rule does not cover Rice's whale core habitat in the northeastern GOA, which is the area that contains the highest known densities of Rice's whale and which has defined the movements of previously tagged Rice's whales. Thus, even though individual Rice's whales occurring outside of the core habitat area may experience harassment, the geographic scope of the rule likely precludes significant impacts to Rice's whales at the species level by avoiding takes of the majority of individuals and by avoiding impacts to the habitat that supports the highest densities of the species. This important context generally means that the takes that do occur for Rice's whales are expected to have lower potential to have negative energetic effects or deleterious effects on reproduction that could reduce the likelihood of survival or reproductive success. In addition, NMFS is again requiring mitigation measures that would minimize or alleviate the likelihood of injury (PTS), TTS, and more severe behavioral responses (the 1,500-m shutdown zone). Exposures to airgun noise would occur in open water areas where animals can more readily avoid the source, which moves slowly and in a linear fashion, and find alternate habitat relatively easily. Those mitigation requirements are expected to be effective in ensuring that impacts are limited to lower- level responses with limited potential to significantly alter behavior patterns in ways that would affect the fitness of individuals and by extension the affected species.

In evaluating mitigation for species or stocks and their habitat, we consider the expected benefits of the mitigation measures for the species or stocks and their habitats against the practicability of implementation. This consideration includes assessing the manner in which, and the degree to which, the implementation of the measure(s) is expected to reduce impacts to marine mammal species or stocks (including through consideration of expected reduced impacts on individuals), their habitat, and their availability for subsistence uses (where relevant). This analysis considers such things as the nature of the activity's adverse impact (likelihood, scope, range); the likelihood that the measure will be effective if implemented; and the likelihood of successful implementation. Practicability of implementing the measure is also assessed and may involve consideration of such things as cost and impact on operations.

Taking into account the above considerations, we provide evaluation of potential survey restrictions in the central and western GOA. Please see discussion of information related to Rice's whale occurrence in the central and western GOA provided previously in the Description of Marine Mammals in the Area of the Specified Activities section, with more detailed discussion provided in the notice of proposed rulemaking (91 FR 9014, February 24, 2026). In summary, passive acoustic data provide evidence that waters 100-400 m deep in the central and western GOA are Rice's whale habitat and are used by Rice's whales in all seasons, though available data suggest that density and abundance of Rice's whales in the central and western GOA are lower than in the core habitat in the northeastern GOA. Little is known about the number of whales that may be present, the nature of these individuals' use of the habitat, or the timing, duration, or frequency of occurrence for individual whales; and predictions of Rice's whale density modeling have been used to estimate potential takes of Rice's whales in the area.

Restricting survey activity in central/western GOA waters from 100 to 400 m depth would avoid likely Level B harassment of any individuals that may occur in the area, but aside from the very large area within the 100-400 m isobaths throughout the GOA generally, there is no information supporting further delineation of any specific area in the central and/or western GOA within which a restriction on survey activity might be expected to provide targeted reductions in adverse impacts to Rice's whales or their habitat. Further, Level B harassment that may occur in the central/western GOA may be expected to have lower potential for meaningful consequences relative to Level B harassment events that occur in the northeastern GOA core habitat area, where important behavior may be more likely disrupted, and where greater numbers of Rice's whale are expected to

occur. The relatively low level of take predicted for Rice's whales in the geographic scope for the specified activity under this final rule, as well as the required mitigation measures (including expanded shutdowns for Rice's whales), which are expected with a high degree of confidence to minimize the duration and intensity of any instances of take that do occur, factor into NMFS' consideration of the potential benefits of any restriction on survey effort in central and western GOA waters 100-400 m depth.

Practicability--NMFS produced a draft RIA in support of the 2018 proposed rule, which evaluated potential costs associated with a range of area-based activity restrictions (available online at: https://www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-gulf-mexico). While the RIA did not directly evaluate the impacts of area-based restrictions for Rice's whales in the central and western GOA, it did consider the impacts of other potential area-based restrictions and in so doing provided a useful framework for considering practicability of area- based restrictions considered in this current rulemaking. The analysis suggested that the analyzed seasonal and year-round area closures would have the potential to generate reductions in leasing, exploration, and subsequent development activity. Although the 2018 draft RIA cautioned that its conclusions were subject to substantial uncertainty, it provided several factors that the likelihood of ultimate impacts to oil and gas production as a result of delays in data collection could be expected to depend upon: (1) oil and gas market conditions; (2) the relative importance of the closure area to oil and gas production; (3) the state of existing data covering the area; and (4) the duration of the closure. For this current rulemaking, NMFS cannot predict factor (1) and does not have complete information regarding factor (3) (though the 2018 draft RIA provides that new surveys are expected to be required to facilitate efficient exploration and development decisions). We can, however, more adequately predict the effects of factors (2) and (4) on the impact of any closure.

Habitat that supports all of the Rice's whale life-history states is generally considered to consist of the aforementioned strip of continental shelf waters within the 100-400 m isobaths throughout the U.S. GOA (Roberts et al., 2016; Garrison et al., 2023; NMFS, 2023). Salinity and surface water velocity are likely predictive of potential Rice's whale occurrence (Garrison et al., 2023), but these more dynamic variables are less useful in delineating a potential area of importance than the static depth variable. Within this GOA-wide depth range, we focus on the area where Soldevilla et al. (2022; 2024) recorded Rice's whale calls as being of interest for a potential restriction. This area lies within the central GOA, where the vast majority of seismic survey effort during NMFS' experience implementing the 2021 rule has occurred. The 2018 proposed rule draft RIA considered the economic impacts of a prospective closure area in deeper waters of the central GOA. The evaluated area was designed to benefit sperm whales and beaked whales, which are found in deep water, and more activity is projected to occur in deep water than in the shelf-break waters where Rice's whale habitat occurs. As such, the 2018 draft RIA analysis likely overestimates the potential impacts of a central or western GOA closure within a portion of the shelf waters considered to be Rice's whale habitat. That said, the draft RIA analysis of deep-water closures in the central GOA suggests that a central GOA closure for Rice's whales could cause significant economic impacts. A key consideration in this finding relates to factor (4), as the analyzed closure for sperm whales and beaked whales was year-round. Similarly here, there is no information to support a temporal component to design of a potential Rice's whale restriction and, therefore, a restriction would appropriately be year- round. As operators have no ability to plan around a year-round restriction, this aspect exacerbates the potential for effects on oil and gas production in the GOA.

We also considered data available specifically for the area under consideration (Rice's whale habitat in the central and western GOA). While Rice's whale habitat (i.e., water depths of 100-400 m on the continental shelf break) contains less oil and gas industry infrastructure than do shallower, more developed waters, and have been subject to less leasing activity than deeper waters with greater expected potential reserves, central and western GOA waters 100-400 m nevertheless host significant industry activity. BOEM provides summary information by water depth bin, including water depths of 201-400 m (see https://www.data.boem.gov/Main/Default.aspx). The area covering those depths overlaps 33 active leases, with 17 active platforms and over 1,200 approved applications to drill. In the past 20 years, over 500 wells have been drilled in water depths of 100-400 m. These data confirm that there is substantial oil and gas industry activity in this area and, therefore, the inability to collect new seismic data could affect oil and gas development given that the oil and gas industry typically uses targeted seismic data to refine geologic analyses before drilling a well. Under the existing rule, NMFS has issued (at the time of writing) 8 LOAs in association with surveys that partially overlapped the central GOA 100-400 m depth band. These surveys support a conclusion that a year-round closure would likely substantially affect future GOA oil and gas activity.

In summary, the foregoing supports that (1) we are unable to delineate specific areas of Rice's whale habitat in the central and western GOA where restrictions on survey activity would be appropriate because there is currently uncertainty about Rice's whale density, abundance, habitat usage patterns and other factors in the central and western GOA; and (2) there is high likelihood that closures or other restrictions on survey activity in all waters of 100-400 m depth in the central and western GOA would have significant economic impacts. Therefore, while new information regarding Rice's whale presence in areas of the GOA outside of the northeastern core habitat suggests that a restriction on survey effort may be expected to reduce adverse impacts to individual whales, there is a lack of information supporting the importance of or appropriately specific timing or location of such a restriction and an unclear understanding of the importance of particular areas to individual whales or the population as a whole. On the other hand, information regarding the potential for economic impacts resulting from a year-round restriction broadly in the 100-400 m area supports our conclusion that there are significant practicability concerns. As a result, NMFS has determined that no additional mitigation is warranted to effect the LPAI on the species.

These measures apply to all vessels associated with any survey activity (e.g., source vessels, streamer vessels, chase vessels, supply vessels). However, NMFS notes that 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. These measures include the following:

1. Vessel operators and crews must maintain a vigilant watch for all marine mammals and must slow down, stop their vessel, or alter course, as appropriate and regardless of vessel size, to avoid striking any marine mammal. A visual observer aboard the vessel must monitor a vessel strike avoidance zone around the vessel (distances stated below). Visual observers monitoring the vessel strike avoidance zone may be third-party observers (i.e., PSOs) or crew members, but crew members responsible for these duties must receive sufficient training to (1) distinguish protected species from other phenomena and (2) broadly to identify a marine mammal as a baleen whale, sperm whale, or other marine mammal;

2. Vessel speeds must be reduced to 10 kn or less when mother/calf pairs, pods, or large assemblages of any marine mammal are observed near a vessel;

3. All vessels must maintain a minimum separation distance of 500 m from baleen whales;

4. All vessels must maintain a minimum separation distance of 100 m from sperm whales;

5. All vessels must, to the maximum extent practicable, attempt to maintain a minimum separation distance of 50 m from all other marine mammals, with an understanding that at times this may not be possible (e.g., for animals that approach the vessel); and

6. When marine mammals are sighted while a vessel is underway, the vessel shall take action as necessary to avoid violating the relevant separation distance (e.g., attempt to remain parallel to the animal's course, avoid excessive speed or abrupt changes in direction until the animal has left the area). If marine mammals are sighted within the relevant separation distance, the vessel must reduce speed and shift the engine to neutral, not engaging the engines until animals are clear of the area. This does not apply to any vessel towing gear or any vessel that is navigationally constrained.

NMFS has carefully evaluated the suite of mitigation measures described here and considered a range of other measures in the context of ensuring that we prescribe the means of effecting the least practicable adverse impact on the affected marine mammal species and stocks and their habitat. Based on our evaluation of these measures, we have determined that the required mitigation measures provide the means of effecting the least practicable adverse impact on marine mammal species or stocks and their habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance.

In order to issue an incidental take authorization for an activity, section 101(a)(5)(A) of the MMPA states that NMFS must set forth requirements pertaining to the monitoring and reporting of the authorized taking. NMFS' MMPA implementing regulations further describe the information that an applicant should provide when requesting an authorization (50 CFR 216.104(a)(13)), including the means of accomplishing the necessary monitoring and reporting that will result in increased knowledge of the species and the level of taking or impacts on populations of marine mammals.

Section 101(a)(5)(A) allows that incidental taking may be authorized only if the total of such taking contemplated over the course of 5 years will have a negligible impact on affected species or stocks (a finding based on impacts to annual rates of recruitment and survival) and, further, section 101(a)(5)(B) requires that authorizations issued pursuant to 101(a)(5)(A) be withdrawn or suspended if the total taking is having, or may have, more than a negligible impact (or such information may inform decisions on requests for LOAs under the specific regulations). Therefore, the necessary requirements pertaining to monitoring and reporting must address the total annual impacts to marine mammal species or stocks. 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 in action area (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 important physical components of marine mammal habitat); and

Mitigation and monitoring effectiveness.

NMFS has carefully reviewed the monitoring and reporting requirements prescribed through the current ITRs, and determined that these requirements remain appropriate. We therefore carry forward those requirements, described below, without change.

All PSO resumes must be submitted to NMFS and PSOs must be approved by NMFS after a review of their qualifications. These qualifications include whether the individual has successfully completed the necessary training (see “Training,” below) and, if relevant, whether the individual has the requisite experience (and is in good standing). PSOs should provide a current resume and information indicating successful completion of an acceptable PSO training course. In order for a PSO training course to be deemed acceptable by NMFS, the agency must, at minimum, review a course information packet that includes the name and qualifications (e.g., experience, training, or education) of the instructor(s), the course outline or syllabus, and course reference material. Absent a waiver (discussed below),

PSOs must be trained biologists, with the following minimum qualifications:

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; and

Successful completion of relevant training (described below), including completion of all required coursework and passing (80 percent or greater) a written and/or oral examination developed for the training program.

In addition, it is recommended that PSOs meet the following requirements:

Experience and ability to conduct field observations and collect data according to assigned protocols (may include academic experience) and experience with data entry on computers;

Visual acuity in both eyes (vision correction is permissible) sufficient for discernment of moving targets at the water's surface with ability to estimate target size and distance; use of binoculars may be necessary to correctly identify the target (required for visual PSOs only);

Experience or training in the field identification of marine mammals, including the identification of behaviors (required for visual PSOs only);

Sufficient training, orientation, or experience with the survey operation to ensure personal safety during observations;

Writing skills sufficient to prepare a report of observations (e.g., description, summary, interpretation, analysis) including but not limited to the number and species of marine mammals observed; marine mammal behavior; and descriptions of activity conducted and implementation of mitigation; and

Ability to communicate orally, by radio or in person, with survey personnel to provide real-time information on marine mammals detected in the area as necessary.

The educational requirements may be waived if the PSO has acquired the relevant skills through alternate experience. Requests for such a waiver must include written justification, and prospective PSOs granted waivers must satisfy training requirements described below. Alternate experience that may be considered includes, but is not limited to, the following:

Secondary education and/or experience comparable to PSO duties;

Previous work experience conducting academic, commercial, or government-sponsored marine mammal surveys; and

Previous work experience as a PSO; the PSO should demonstrate good standing and consistently good performance of PSO duties.

Training--NMFS does not formally administer any PSO training program or endorse specific providers but will approve PSOs that have successfully completed courses that meet the curriculum and trainer requirements specified herein and, therefore, are deemed acceptable. To be deemed acceptable, training should adhere generally to the recommendations provided by “National Standards for a Protected Species Observer and Data Management Program: A Model Using Geological and Geophysical Surveys” (Baker et al., 2013). Those recommendations include the following topics for training programs:

Life at sea, duties, and authorities;

Ethics, conflicts of interest, standards of conduct, and data confidentiality;

Offshore survival and safety training;

Overview of oil and gas activities (including geophysical data acquisition operations, theory, and principles) and types of relevant sound source technology and equipment;

Overview of the MMPA and ESA as they relate to protection of marine mammals;

Mitigation, monitoring, and reporting requirements as they pertain to geophysical surveys;

Marine mammal identification, biology and behavior;

Background on underwater sound;

Visual surveying protocols, distance calculations and determination, cues, and search methods for locating and tracking different marine mammal species (visual PSOs only);

Optimized deployment and configuration of PAM equipment to ensure effective detections of cetaceans for mitigation purposes (PAM operators only);

Detection and identification of vocalizing species or cetacean groups (PAM operators only);

Measuring distance and bearing of vocalizing cetaceans while accounting for vessel movement (PAM operators only);

Data recording and protocols, including standard forms and reports, determining range, distance, direction, and bearing of marine mammals and vessels; recording GPS location coordinates, weather conditions, Beaufort wind force and sea state, etc.;

Proficiency with relevant software tools;

Field communication/support with appropriate personnel, and using communication devices (e.g., two-way radios, satellite phones, internet, email, facsimile);

Reporting of violations, noncompliance, and coercion; and

Conflict resolution.

PAM operators should regularly refresh their detection skills through practice with simulation-modeling software and keep up to date with training on the latest software/hardware advances.

The lead PSO is responsible for establishing and maintaining clear lines of communication with vessel crew. The vessel operator shall work with the lead PSO to accomplish this and shall ensure any necessary briefings are provided for vessel crew to understand mitigation requirements and protocols. While on duty, PSOs will continually scan the water surface in all directions around the acoustic source and vessel for presence of marine mammals, using a combination of the naked eye and high-quality binoculars, from optimum vantage points for unimpaired visual observations with minimum distractions. PSOs will collect observational data for all marine mammals observed, regardless of distance from the vessel, including species, group size, presence of calves, distance from vessel and direction of travel, and any observed behavior (including an assessment of behavioral responses to survey activity). Upon observation of marine mammal(s), a PSO will record the observation and monitor the animal's position (including latitude/ longitude of the vessel and relative bearing and estimated distance to the animal) until the animal dives or moves out of visual range of the observer, and a PSO will continue to observe the area to watch for the animal to resurface or for additional animals that may surface in the area. PSOs will also record environmental conditions at the beginning and end of the observation period and at the time of any observations, as well as whenever conditions change significantly in the judgment of the PSO on duty.

For all deep penetration surveys, the vessel operator must provide bigeye binoculars of appropriate quality (e.g., 25 x 150; 2.7 view angle; individual ocular focus; height control) solely for PSO use. These should be pedestal-mounted on the deck at the most appropriate vantage point that provides for optimal sea surface observation, PSO safety, and safe operation of the vessel. Other required equipment, which should be made available to PSOs by the third-party observer provider, includes

reticle binoculars of appropriate quality (e.g., 7 x 50), GPS, digital camera with a telephoto lens (the camera or lens should also have an image stabilization system) that is at least 300 mm or equivalent on a full-frame single-lens reflex, compass, and any other tools necessary to adequately perform the tasks described above, including accurate determination of distance and bearing to observed marine mammals.

Use of towed PAM is required for deep penetration surveys. Monitoring of a towed PAM system is required at all times for these surveys, from 30 minutes prior to ramp-up, throughout all use of the acoustic source, and for 60 minutes following cessation of survey activity. Towed PAM systems should consist of hardware (e.g., hydrophone array, recorder, cables) and software (e.g., data processing program and algorithm). Some type of automated detection software must be used. Acoustic signals are processed for output to the PAM operator with software designed to detect marine mammal vocalizations. Current PAM technology has some limitations (e.g., limited directional capabilities and detection range, detection of signals due to vessel and flow noise, low accuracy in localization) and there are no formal guidelines currently in place regarding specifications for hardware, software, or operator training requirements.

NMFS' requirement to use PAM refers to the use of calibrated hydrophone arrays with full system redundancy to detect, identify, and estimate distance and bearing to vocalizing cetaceans, to the extent possible. With regard to calibration, the PAM system should have at least one calibrated hydrophone, sufficient for determining whether background noise levels on the towed PAM system are sufficiently low to meet performance expectations. Additionally, if multiple hydrophone types occur in a system (i.e., monitor different bandwidths), then one hydrophone from each such type shall be calibrated, and whenever sets of hydrophones (of the same type) are sufficiently spatially separated such that they would be expected to experience ambient noise environments that differ by 6 dB or more across any integrated species cluster bandwidth, then at least one hydrophone from each set should be calibrated. In terms of calibrating the rest of the system, the signal route to the data recorder and monitoring software shall be calibrated so that the binary amplitude data written to hard disk can be converted into units of acoustic pressure. The configuration of hardware should be coupled with appropriate software to aid monitoring and listening by a PAM operator skilled in bioacoustics analysis and computer system specifications capable of running appropriate software. GPS data acquisition is recommended for all PAM operations. If the PAM plan (see below) claims an ability to localize, every localization estimate obtained from a PAM system must be accompanied by some estimate of uncertainty and ambiguity.

In the absence of formal standards addressing any of these three facets of PAM technology, all applicants must provide a PAM plan including description of the hardware and software proposed for use prior to proceeding with any survey where PAM is required. Following the survey, a validation document must be submitted as part of required reporting (see below). The purpose of the PAM plan is to demonstrate that the PAM system being proposed for use is adequate for addressing the mitigation goals. The plan shall include methodology and documentation requirements for all stages of the project. PAM plans should, at minimum, adequately address and describe (1) the hardware and software planned for use, including a hardware performance diagram demonstrating that the sensitivity and dynamic range of the hardware is appropriate for the operation; (2) deployment methodology, including target depth/tow distance; (3) definitions of expected operational conditions, used to summarize background noise statistics; (4) proposed detection-classification-localization methodology, including anticipated species clusters (using a cluster definition table), target minimum detection range for each cluster, and the proposed localization method for each cluster; (5) operation plans, including the background noise sampling schedule; (6) array design considerations for noise abatement; and (7) cluster-specific details regarding which real-time displays and automated detectors the operator would monitor. Where relevant, the plan should address the potential for PAM deployment on a receiver vessel or other associated vessel separate from the acoustic source.

Species clusters--The PAM plan shall list the species of concern during the upcoming operation. While some species may be listed individually for special attention, in many circumstances it is expected that for the purposes of a PAM operation multiple species can be grouped together in a “cluster” that shares similar acoustic and behavioral characteristics (e.g., sperm whale, beaked whales). The plan must specify a target minimum detection (and possibly localization) range for each species cluster used in the document. Different ranges can be defined for different operational conditions. The PAM system may exceed this detection range, but shall always be capable of achieving this minimum detection range.

Hardware and software specifications--The PAM plan shall have a section dedicated to demonstrating that the PAM hardware is sensitive enough to detect signals from the species clusters of concern at the target minimum detection ranges specified. The plan should include a hardware specification table and hardware performance diagram. The diagram will show the sensitivity and bandwidth of the combined array hardware and recording system, as well as the received levels required for a given species cluster to be detectable at the target minimum detection range. The overall goal of the diagram is to visually demonstrate that the planned PAM array/recording system would have the capability of detecting various species clusters at required target ranges, provided that background noise levels are not an issue.

Operational conditions--The validation document should demonstrate whether the PAM system has been compromised by excessive background noise, whether that noise is electronic interference, flow, platform, or environmental noise. Therefore, the PAM plan shall define a set of “operational conditions” under which detection statistics (background noise profiles) will be categorized during the project. Operational conditions consist of three categories: platform activity and status, mitigation (activity) status, and environmental status.

Operating procedures--The PAM plan shall describe the level of effort that is reasonably expected to occur for the monitoring requirements. For every species cluster, the plan should detail which part of the PAM display would be used for detecting that cluster. For example, if a scrolling spectrogram display is being used for a species cluster, then the spectrogram's fast Fourier transform sample size, frequency bandwidth, and their refresh rate shall be specified. Similar details would be provided for other software tools, such as click detectors and other automated detectors and classifiers. The plan shall also provide a screenshot of the expected monitor display.

In coordination with vessel crew, the lead PAM operator will be responsible for deployment, retrieval, and testing and optimization of the hydrophone

array. While on duty, the PAM operator must diligently listen to received signals and/or monitoring display screens in order to detect vocalizing cetaceans, except as required to attend to PAM equipment. The PAM operator must use appropriate sample analysis and filtering techniques and must report all cetacean detections. NMFS recommends that vessel self-noise assessments be undertaken during mobilization in order to optimize PAM array configuration according to the specific noise characteristics of the vessel and equipment involved, and to refine expectations for distance/bearing estimations for cetacean species during the survey. Copies of any vessel self-noise assessment reports must be included with the summary trip report.

PSOs must use standardized electronic data forms. PSOs will record detailed information about any implementation of mitigation requirements, including the distance of animals to the acoustic source and description of specific actions that ensued, the behavior of the animal(s), any observed changes in behavior before and after implementation of mitigation, and if shutdown was implemented, the length of time before any subsequent ramp-up of the acoustic source to resume survey. If required mitigation was not implemented, PSOs should submit a description of the circumstances. NMFS requires that, at a minimum, the following information be reported:

Vessel names (source vessel and other vessels associated with survey), vessel size and type, maximum speed capability of vessel, port of origin, and call signs;

PSO names and affiliations;

Dates of departures and returns to port with port name;

Dates and participants of PSO briefings;

Dates and times (Greenwich Mean Time) of survey effort and times corresponding with PSO effort;

Vessel location (latitude/longitude) when survey effort begins and ends and vessel location at beginning and end of visual PSO duty shifts

Vessel location at 30 second intervals (if software capability allows) or 5-minute intervals (if location must be manually recorded);

Vessel heading and speed at beginning and end of visual PSO duty shifts and upon any line change;

Environmental conditions while on visual survey (at beginning and end of PSO shift and whenever conditions change significantly), including Beaufort scale and any other relevant weather conditions including cloud cover, fog, sun glare, night, and overall visibility to the horizon;

Vessel location when environmental conditions change significantly;

Factors that may have contributed to impaired observations during each PSO shift change or as needed as environmental conditions change (e.g., vessel traffic, equipment malfunctions);

Survey activity information, such as acoustic source power output while in operation, number and volume of airguns operating in an array, tow depth of an acoustic source, and any other notes of significance (i.e., pre-clearance, ramp-up, shutdown, testing, shooting, ramp-up completion, end of operations, streamers, etc.);

If a marine mammal is sighted, the following information should be recorded:

[cir] Watch status (sighting made by PSO on/off effort, opportunistic, crew, alternate vessel/platform);

[cir] PSO who sighted the animal and PSO location (including height above water) at time of sighting;

[cir] Time of sighting;

[cir] Vessel location at time of sighting;

[cir] Water depth;

[cir] Direction of vessel's travel (compass direction);

[cir] Direction of animal's travel relative to the vessel;

[cir] Pace of the animal;

[cir] Estimated distance to the animal (and method of estimating distance) and its heading relative to vessel at initial sighting;

[cir] Identification of the animal (e.g., genus/species, lowest possible taxonomic level, or unidentified) and PSO confidence in identification; also note the composition of the group if there is a mix of species;

[cir] Estimated number of animals (high/low/best);

[cir] Estimated number of animals by cohort (adults, yearlings, juveniles, calves, group composition, etc.);

[cir] Description (as many distinguishing features as possible of each individual seen, including length, shape, color, pattern, scars or markings, shape and size of dorsal fin, shape of head, and blow characteristics);

[cir] Detailed behavior observations (e.g., number of blows, number of surfaces, breaching, spyhopping, diving, feeding, traveling; as explicit and detailed as possible; note any observed changes in behavior);

[cir] Animal's closest point of approach (CPA) and/or closest distance from the acoustic source;

[cir] Platform activity at time of sighting (e.g., deploying, recovering, testing, shooting, data acquisition, other); and

[cir] Description of any actions implemented in response to the sighting (e.g., delays, shutdown, ramp-up); time and location of the action should also be recorded;

If a marine mammal is detected while using the PAM system, the following information should be recorded:

[cir] An acoustic encounter identification number, and whether the detection was linked with a visual sighting;

[cir] Time when first and last heard;

[cir] Types and nature of sounds heard (e.g., clicks, whistles, creaks, burst pulses, continuous, sporadic, strength of signal); and

[cir] Any additional information recorded such as water depth of the hydrophone array, bearing of the animal to the vessel (if determinable), species or taxonomic group (if determinable), spectrogram screenshot, and any other notable information.

PSO effort, survey details, and sightings data should be recorded continuously during surveys. Reports must include all information described above under “Data Collection,” including amount and location of line-kms surveyed and all marine mammal observations with closest approach distance. Draft reports must be submitted to NMFS within 90 days of survey completion or following expiration of an issued LOA. In the event that an LOA is issued for a period exceeding 1 year, annual reports must be submitted during the period of validity. The draft report must be accompanied by a certification from lead PSOs as to the accuracy of the report. A final report must be submitted within 30 days following resolution of any comments on the draft report.

The report must describe the operations conducted and sightings of marine mammals near the operations; provide full documentation of methods, results, and interpretation pertaining to all monitoring; summarize the dates and locations of survey operations, and all marine mammal sightings (dates, times, locations, activities, associated survey activities); and provide information regarding locations where the acoustic source was used. The LOA-holder shall provide geo- referenced time-stamped vessel tracklines for all time periods in which airguns (full array or single) were operating. Tracklines should include points recording any change in airgun status (e.g., when the airguns began

operating, when they were turned off). 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 should be referenced to the WGS84 geographic coordinate system. In addition to the report, all raw observational data shall be made available to NMFS.

This report must also include a validation document concerning the use of PAM (if PAM was required), which should include necessary noise validation diagrams (NVD) and demonstrate whether background noise levels on the PAM deployment limited achievement of the planned detection goals. A separate diagram should be produced for every background noise percentile chosen for analysis. Background noise percentiles, rather than a simple average of the data, are required because the highly non-stationary characteristics of many background noise profiles cannot be described by a simple mean. For example, data collected during a seismic survey will have short periods of time containing high-intensity pulses and longer periods of time dominated by lower levels of reverberation. Taking a simple mean of these noise data would imply background noise levels substantially higher than what may actually have been present between seismic pulses. A validation report would typically contain between three to five diagrams, depending on the number of percentiles analyzed. At a minimum, the validation report should contain three diagrams that include the 50th percentile (median), 5th percentile, and 95th percentile. The 25th percentile and 75th percentile may also be included. In each percentile diagram, a separate background noise curve shall be drawn for each defined operational condition. In general, the NVD should be generated from the data stream that is used for detecting the presence of marine mammal signals. For example, if beamforming or some other form of array gain has been applied before invoking signal detection, then the NVD should be generated using the beamformed data, and not omnidirectional data. The complete set of NVDs, one for each percentile of interest, combined with a table that lists the fraction of time the activity was in each operational state, provides a means of reviewing the background noise-limitations encountered by the PAM system during various operational conditions. Actual marine mammal detections should be plotted on this diagram for a reasonableness check on the expected received levels. Overall, the validation document should reiterate all the goals and parameters stated in the planning document and verify that goals were/were not met, why, changes, etc. The validation document also should state whether the planning was suited to the needs of the survey and met the required mitigation standards.

The report must include a post-survey estimate of the instances of take of each species utilizing the line miles of survey actually conducted and the same methods used to initially predict the estimated take in the LOA application. Depending on the length and dates of the survey, LOA-holders may be required to segment take estimates into specific years to support the administration of the rule.

Individual LOA-holders will be responsible for collecting and submitting monitoring data to NMFS, as described above. In addition, on an annual basis, LOA-holders will also collectively be responsible for compilation and analysis of those data for inclusion in subsequent annual synthesis reports. Individual LOA-holders may collaborate to produce this report or may elect to have their trade associations support the production of such a report. These reports would summarize the data presented in the individual LOA-holder reports, provide analysis of these synthesized results, discuss the implementation of required mitigation, and present any recommendations. This comprehensive annual report would be the basis of an annual adaptive management process (described below in Adaptive Management). The following topics will be described in comprehensive reporting:

Summary of geophysical survey activity by survey type, geographic zone (i.e., the seven zones described in the modeling report), month, and acoustic source status (e.g., inactive, ramp-up, full-power, power-down);

Summary of monitoring effort (on-effort hours and/or distance) by acoustic source status, location, and visibility conditions (for both visual and acoustic monitoring);

Summary of mitigation measures implemented (e.g., delayed ramp-ups, shutdowns, course alterations for vessel strike avoidance) by survey type and location;

Sighting rates of marine mammals during periods with and without acoustic source activities and other variables that could affect detectability of marine mammals, such as:

[cir] Initial sighting distances of marine mammals relative to source status;

[cir] Closest point of approach of marine mammals relative to source status;

[cir] Observed behaviors and types of movements of marine mammals relative to source status;

[cir] Distribution/presence of marine mammals around the survey vessel relative to source status; and

[cir] Analysis of the effects of various factors influencing the detectability of marine mammals (e.g., wind speed, sea state, swell height, presence of glare or fog).

Estimates of total take across all activities for which take is authorized based on actual survey effort and original estimation method;

Summary and conclusions from monitoring in previous year; and

Recommendations for adaptive management.

Each annual comprehensive report should cover 1 full year of monitoring effort and must be submitted for review each year. Each report should analyze survey and monitoring effort described in reports submitted by individual LOA-holders during a given 1 year period, beginning from the date of effectiveness of these regulations. Each annual comprehensive report must be submitted for review 90 days following conclusion of the annual reporting period.

Discovery of Injured or Dead Marine Mammal--In the event that personnel involved in the survey activities covered by the authorization discover an injured or dead marine mammal, the LOA-holder shall report the incident to OPR, NMFS and to the regional stranding network as soon as feasible. The report must include the following information:

Time, date, and location (latitude/longitude) of the first discovery (and updated location information if known and applicable);

Species identification (if known) or description of the animal(s) involved;

Condition of the animal(s) (including carcass condition if the animal is dead);

Observed behaviors of the animal(s), if alive;

If available, photographs or video footage of the animal(s); and

General circumstances under which the animal was discovered.

Vessel Strike--In the event of a ship strike of a marine mammal by any vessel involved in the activities covered by the authorization, the LOA-holder shall report the incident to OPR, NMFS and to the regional stranding network as

soon as feasible. The report must include the following information:

Time, date, and location (latitude/longitude) of the incident;

Species identification (if known) or description of the animal(s) involved;

Vessel's speed during and leading up to the incident;

Vessel's course/heading and what operations were being conducted (if applicable);

Status of all sound sources in use;

Description of avoidance measures/requirements that were in place at the time of the strike and what additional measures were taken, if any, to avoid strike;

Environmental conditions (e.g., wind speed and direction, Beaufort sea state, cloud cover, visibility) immediately preceding the strike;

Estimated size and length of animal that was struck;

Description of the behavior of the marine mammal immediately preceding and following the strike;

If available, description of the presence and behavior of any other marine mammals immediately preceding the strike;

Estimated fate of the animal (e.g., dead, injured but alive, injured and moving, blood or tissue observed in the water, status unknown, disappeared); and

To the extent practicable, photographs or video footage of the animal(s).

Actions To Minimize Additional Harm to Live-Stranded (or Milling) Marine Mammals

For deep penetration surveys, in the event of a live stranding (or near-shore atypical milling) event within 50 km of the survey operations, where the NMFS stranding network is engaged in herding or other interventions to return animals to the water, the Director of OPR, NMFS (or designee) will advise the LOA-holder of the need to implement shutdown procedures for all active acoustic sources operating within 50 km of the stranding. Shutdown procedures for live stranding or milling marine mammals include the following:

If at any time, the marine mammals die or are euthanized, or if herding/intervention efforts are stopped, the Director of OPR, NMFS (or designee) will advise the LOA-holder that the shutdown around the animals' location is no longer needed.

Otherwise, shutdown procedures will remain in effect until the Director of OPR, NMFS (or designee) determines and advises the LOA- holder that all live animals involved have left the area (either of their own volition or following an intervention).

If further observations of the marine mammals indicate the potential for re-stranding, additional coordination with the LOA-holder will be required to determine what measures are necessary to minimize that likelihood (e.g., extending the shutdown or moving operations farther away) and to implement those measures as appropriate.

Shutdown procedures are not related to the investigation of the cause of the stranding and their implementation is not intended to imply that the specified activity is the cause of the stranding. Rather, shutdown procedures are intended to protect marine mammals exhibiting indicators of distress by minimizing their exposure to possible additional stressors, regardless of the factors that contributed to the stranding.

Additional Information Requests--If NMFS determines that the circumstances of any marine mammal stranding found in the vicinity of the activity suggest investigation of the association with survey activities is warranted (example circumstances noted below), and an investigation into the stranding is being pursued, NMFS will submit a written request to the LOA-holder indicating that the following initial available information must be provided as soon as possible, but no later than 7 business days after the request for information.

Status of all sound source use in the 48 hours preceding the estimated time of stranding and within 50 km of the discovery/ notification of the stranding by NMFS; and

If available, description of the behavior of any marine mammal(s) observed preceding (i.e., within 48 hours and 50 km) and immediately after the discovery of the stranding.

Examples of circumstances that could trigger the additional information request include, but are not limited to, the following:

Atypical nearshore milling events of live cetaceans;

Mass strandings of cetaceans (two or more individuals, not including cow/calf pairs);

Beaked whale strandings; or,

Necropsies with findings of pathologies that are unusual for the species or area.

In the event that the investigation is still inconclusive, the investigation of the association of the survey activities is still warranted, and the investigation is still being pursued, NMFS may provide additional information requests, in writing, regarding the nature and location of survey operations prior to the time period above.