90 FR 11 pgs. 5815-5826 - Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to a Marine Geophysical Survey in the Northwest Gulf of Mexico
Type: NOTICEVolume: 90Number: 11Pages: 5815 - 5826
Pages: 5815, 5816, 5817, 5818, 5819, 5820, 5821, 5822, 5823, 5824, 5825, 5826Docket number: [RTID 0648-XE594]
FR document: [FR Doc. 2025-01143 Filed 1-16-25; 8:45 am]
Agency: Commerce Department
Sub Agency: National Oceanic and Atmospheric Administration
Official PDF Version: PDF Version
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
[RTID 0648-XE594]
Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to a Marine Geophysical Survey in the Northwest Gulf of Mexico
AGENCY:
National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce.
ACTION:
Notice; issuance of an incidental harassment authorization.
SUMMARY:
In accordance with the regulations implementing the Marine Mammal Protection Act (MMPA) as amended, notification is hereby given that NMFS has issued an incidental harassment authorization (IHA) to the University of Texas at Austin (UT) to incidentally harass marine mammals during survey activities associated with a marine geophysical survey in coastal waters off Texas in the northwest (NW) Gulf of Mexico (GOM).
DATES:
This authorization is effective from January 13, 2025 through January 12, 2026.
ADDRESSES:
Electronic copies of the application and supporting documents, as well as a list of the references cited in this document, may be obtained online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-research-and-other-activities. In case of problems accessing these documents, please call the contact listed below.
FOR FURTHER INFORMATION CONTACT:
Rachel Wachtendonk, Office of Protected Resources, NMFS, (301) 427-8401.
SUPPLEMENTARY INFORMATION:
Background
The MMPA prohibits the "take" of marine mammals, with certain exceptions. Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq. ) direct the Secretary of Commerce (as delegated to NMFS) to allow, upon request, the incidental, but not intentional, taking of small numbers of marine mammals by U.S. citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region if certain findings are made and either regulations are proposed or, if the taking is limited to harassment, a notice of a proposed IHA is provided to the public for review.
Authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s) and will not have an unmitigable adverse impact on the availability of the species or stock(s) for taking for subsistence uses (where relevant). Further, NMFS must prescribe the permissible methods of taking and other "means of effecting the least practicable adverse impact" on the affected species or stocks and their habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, and on the availability of the species or stocks for taking for certain subsistence uses (referred to in shorthand as "mitigation"); and requirements pertaining to the monitoring and reporting of the takings. The definitions of all applicable MMPA statutory terms used above are included in the relevant sections below and can be found in section 3 of the MMPA (16 U.S.C. 1362) and NMFS regulations at 50 CFR 216.103.
Summary of Request
On July 25, 2024, NMFS received a request from UT for an IHA to take marine mammals incidental to a marine geophysical survey in coastal waters off Texas in the NW GOM. The application was deemed adequate and complete on September 24, 2024. UT's request is for take of bottlenose dolphins, Atlantic spotted dolphins, and rough-toothed dolphins, by Level B harassment only. Neither UT nor NMFS expect serious injury or mortality to result from this activity and, therefore, an IHA is appropriate. There are no changes from the proposed IHA to the final IHA.
Description of Activity
Researchers from UT plan to conduct a low-energy marine seismic survey using airguns as the acoustic source from the research vessel (R/V) Brooks McCall (McCall) or similar vessel operated by TDI-Brooks International. The planned survey will occur within Texas State waters in the NW GOM from approximately January to April 2025. The planned survey will occur within the Exclusive Economic Zone (EEZ) of the United States and in Texas State waters, in water depths less than 30 meters (m). To complete this high resolution 3D (HR3D) seismic survey, the McCall will tow a 2-airgun array with a total discharge volume of ~210 cubic inches (in 3 ) at a depth of 3-4 meters (m), with a shot interval of 12.5 m (5-10 seconds (s)) as the primary acoustic source. The airgun array receiver will consist of four 25-m-long solid-state hydrophone streamers, spaced 10 m apart. Approximately 4,440 km of seismic acquisition is planned. The airgun array will introduce underwater sounds that may result in take, by Level B harassment only, of marine mammals.
A detailed description of the planned marine geophysical survey is provided in the Federal Register notice for the proposed IHA (89 FR 91340, November 19, 2024). Since that time, no changes have been made to the planned activities. Therefore, a detailed description is not provided here. Please refer to that Federal Register notice for a detailed description of the specific activity.
Comments and Responses
[top] A notice of NMFS' proposal to issue an IHA to UT was published in the Federal Register on November 19, 2024 (89 FR 91340). That notice described, in detail, UT's activity, the marine mammal species that may be affected by the activity, and the anticipated effects on marine mammals. In that notice, we requested public input on the request for authorization described therein, our analyses, the proposed authorization, and any other aspect of the notice of
Description of Marine Mammals in the Area of Specified Activities
Sections 3 and 4 of the application summarize available information regarding status and trends, distribution and habitat preferences, and behavior and life history of the potentially affected species. NMFS fully considered all of this information, and we refer the reader to these descriptions, instead of reprinting the information. Additional information regarding population trends and threats may be found in NMFS' Stock Assessment Reports (SARs; https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments ) and more general information about these species ( e.g., physical and behavioral descriptions) may be found on NMFS' website ( https://www.fisheries.noaa.gov/find-species ).
Table 1 lists all species or stocks for which take is expected and may be taken as a result of the planned survey and summarizes information related to the population or stock, including regulatory status under the MMPA and Endangered Species Act (ESA) and potential biological removal (PBR), where known. PBR is defined by the MMPA as the maximum number of animals, not including natural mortalities, that may be removed from a marine mammal stock while allowing that stock to reach or maintain its optimum sustainable population (as described in NMFS' SARs). While no serious injury or mortality is anticipated or authorized here, PBR and annual serious injury and mortality (M/SI) from anthropogenic sources are included here as gross indicators of the status of the species or stocks and other threats.
Marine mammal abundance estimates presented in this document represent the total number of individuals that make up a given stock or the total number estimated within a particular study or survey area. NMFS' stock abundance estimates for most species represent the total estimate of individuals within the geographic area, if known, that comprises that stock. For some species, this geographic area may extend beyond U.S. waters. All managed stocks in this region are assessed in NMFS' U.S. Atlantic and Gulf of Mexico SARs. All values presented in table 1 are the most recent available at the time of publication and are available online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments.
| Common name | Scientific name | Stock | ESA/MMPA status; strategic (Y/N)? 2 | Stock abundance (CV, N min , most recent abundance survey)? 3 | PBR | Annual M/SI? 4 | GOM population abundance? 5 |
|---|---|---|---|---|---|---|---|
| Odontoceti (toothed whales, dolphins, and porpoises) | |||||||
| Family Delphinidae | |||||||
| Atlantic spotted dolphin | Stenella frontalis | GOM | -/-; N | 21,506 (0.26; 17,339; 2018) | 166 | 6 ?36 | 7 ?12,240 |
| Rough-toothed dolphin | Steno bredanensis | GOM | -/-; N | unk (n/a; unk; 2018) | undetermined | 39 | 4,853 |
| Bottlenose dolphin | Tursiops truncatus | GOM Western Coastal | -/-; N | 20,759 (0.13; 18,585; 2018) | 167 | 36 | 7 ?151,886 |
| Northern GOM Continental Shelf | -/-; N | 63,280 (0.11; 57,917; 2018) | 556 | 5 ?65 | |||
| 1 ?Information on the classification of marine mammal species can be found on the web page for The Society for Marine Mammalogy's Committee on Taxonomy ( https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/ ). | |||||||
| 2 ?ESA status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed under the ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality exceeds PBR or which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed under the ESA is automatically designated under the MMPA as depleted and as a strategic stock. | |||||||
| 3 ?NMFS marine mammal stock assessment reports online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports-region. CV is coefficient of variation; N min is the minimum estimate of stock abundance. In some cases, CV is not applicable. | |||||||
| 4 ?These values, found in NMFS's SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined ( e.g., commercial fisheries, ship strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range. A CV associated with estimated mortality due to commercial fisheries is presented in some cases. | |||||||
| 5 ?Model-predicted stock abundance for Atlantic spotted dolphins and bottlenose dolphins from the most recent GOM density models (Garrison et al., 2023). Stock abundance for rough-toothed dolphins was taken from Roberts et al. (2016) density models, as Garrison et al. (2023) did not create a model for this species. | |||||||
| 6 ?M/SI is a minimum count and does not include projected mortality estimates for 2015-2019 due to the DWH oil spill. | |||||||
| 7 ?This estimate includes both coastal and continental shelf bottlenose dolphins from other stocks. | |||||||
As indicated above, all three species (with four managed stocks) in table 1 temporally and spatially co-occur with the activity to the degree that take is reasonably likely to occur. All species that could potentially occur in the planned survey areas are included in table 2 of the IHA application.
A detailed description of the species likely to be affected by the marine geophysical survey, including brief introductions to the species and relevant stocks as well as available information regarding population trends and threats, and information regarding local occurrence, were provided in the Federal Register notice for the proposed IHA (89 FR 91340, November 19, 2024); since that time, we are not aware of any changes in the status of these species and stocks; therefore, detailed descriptions are not provided here. Please refer to that Federal Register notice for these descriptions. Please also refer to NMFS' website ( https://www.fisheries.noaa.gov/find-species ) for generalized species accounts.
Marine Mammal Hearing
[top] 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
| Hearing group | Generalized hearing range?* |
|---|---|
| Underwater: | |
| Low-frequency (LF) cetaceans (baleen whales) | 7 Hz to 36?* kHz. |
| High-frequency (HF) cetaceans (dolphins, toothed whales, beaked whales, bottlenose whales) | 150 Hz to 160 kHz. |
| Very High-frequency (VHF) cetaceans (true porpoises, Kogia, river dolphins, Cephalorhynchid, Lagenorhynchus cruciger & L. australis ) | 200 Hz to 165 kHz. |
| Phocid pinnipeds (PW) (underwater) (true seals) | 40 Hz to 90 kHz. |
| Otariid pinnipeds (OW) (underwater) (sea lions and fur seals) | 60 Hz to 68 kHz. |
| *?Represents the generalized hearing range for the entire group as a composite ( i.e., all species within the group), where individual species' hearing ranges may not be as broad. Generalized hearing range chosen based on ~65 dB threshold from composite audiogram, previous analysis in NMFS 2018, and/or data from Southall et al., 2007; Southall et al., 2019. Additionally, animals are able to detect very loud sounds above and below that "generalized" hearing range. | |
Potential Effects of Specified Activities on Marine Mammals and Their Habitat
The effects of underwater noise from UT's survey activities have the potential to result in behavioral harassment of marine mammals in the vicinity of the survey area. The notice of proposed IHA (89 FR 91340, November 19, 2024) included a discussion of the effects of anthropogenic noise on marine mammals and the potential effects of underwater noise from UT's survey activity on marine mammals and their habitat. That information and analysis is referenced in this final IHA determination and is not repeated here; please refer to the notice of proposed IHA (89 FR 91340, November 19, 2024).
Estimated Take of Marine Mammals
This section provides an estimate of the number of incidental takes authorized through the IHA, which will inform NMFS' consideration of "small numbers," the negligible impact determinations, and impacts on subsistence uses.
Harassment is the only type of take expected to result from these activities. Except with respect to certain activities not pertinent here, section 3(18) of the MMPA defines "harassment" as any act of pursuit, torment, or annoyance, which (i) has the potential to injure a marine mammal or marine mammal stock in the wild (Level A harassment); or (ii) has the potential to disturb a marine mammal or marine mammal stock in the wild by causing disruption of behavioral patterns, including, but not limited to, migration, breathing, nursing, breeding, feeding, or sheltering (Level B harassment).
Authorized takes will be by Level B harassment only, in the form of disruption of behavioral patterns for individual marine mammals resulting from exposure to sound from low energy seismic airguns. Based on the nature of the activity, i.e., use of a low energy 2-airgun array, auditory injury (Level A harassment) is neither anticipated nor authorized. As described previously, no serious injury or mortality is anticipated or authorized for this activity. Below we describe how the authorized take numbers are estimated.
For acoustic impacts, generally speaking, we estimate take by considering: (1) acoustic thresholds above which NMFS believes the best available science indicates marine mammals will likely be behaviorally harassed or incur some degree of permanent hearing impairment; (2) the area or volume of water that will be ensonified above these levels in a day; (3) the density or occurrence of marine mammals within these ensonified areas; and, (4) the number of days of activities. We note that while these factors can contribute to a basic calculation to provide an initial prediction of potential takes, additional information that can qualitatively inform take estimates is also sometimes available ( e.g., previous monitoring results or average group size). Below, we describe the factors considered here in more detail and present the take estimates.
Acoustic Thresholds
NMFS recommends the use of acoustic thresholds that identify the received level of underwater sound above which exposed marine mammals would be reasonably expected to be behaviorally harassed (equated to Level B harassment) or to incur auditory injury of some degree (equated to Level A harassment).
[top] Level B Harassment -Though significantly driven by received level, the onset of behavioral disturbance from anthropogenic noise exposure is also informed to varying degrees by other factors related to the source or exposure context ( e.g., frequency, predictability, duty cycle, duration of the exposure, signal-to-noise ratio, distance to the source), the environment ( e.g., bathymetry, other noises in the area, predators in the area), and the receiving animals (hearing, motivation, experience, demography, life stage, depth) and can be difficult to predict ( e.g., Southall et al., 2007, 2021, Ellison et al., 2012). Based on what the available science indicates and the practical need to use a threshold based on a metric 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 behavioral harassment. NMFS generally predicts that marine mammals are likely to be behaviorally harassed in a manner considered to be Level B harassment when exposed to underwater anthropogenic noise above root-mean-squared pressure received levels (RMS SPL) of 120 decibels (dB) (referenced to 1 micropascal (re 1 µPa)) for continuous ( e.g., vibratory pile driving, drilling) and above RMS SPL 160 dB re 1 µPa for non-explosive impulsive ( e.g., seismic airguns) or intermittent ( e.g., scientific sonar) sources. Generally speaking, Level B harassment take estimates based on these behavioral harassment
UT's planned survey includes the use of impulsive seismic sources ( e.g., GI-airguns) and therefore, the 160 dB re 1 µPa (rms) criteria is applicable for analysis of Level B harassment.
Level A harassment -NMFS' Updated Technical Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammal Hearing (NMFS, 2024 (2024 Updated Technical Guidance)) identifies dual criteria to assess auditory injury (Level A harassment) to five different marine mammal groups (based on hearing sensitivity) as a result of exposure to noise from two different types of sources (impulsive or non-impulsive). NMFS defines auditory injury as "damage to the inner ear that can result in destruction of tissue . . . which may or may not result in permanent threshold shift (PTS)" (NMFS, 2024). NMFS defines PTS as a permanent, irreversible increase in the threshold of audibility at a specified frequency or portion of an individual's hearing range above a previously established reference level (NMFS, 2024). PTS does not generally affect more than a limited frequency range, and an animal that has incurred PTS has incurred some level of hearing loss at the relevant frequencies; typically, animals with PTS are not functionally deaf (Au and Hastings, 2008; Finneran, 2016). UT's planned survey includes the use of impulsive seismic sources ( i.e., airguns).
UT previously used modeling based on NMFS' 2018 technical guidance in order to calculate their isopleths. Based on the outcome of these comparisons/analyses using the Updated 2024 Technical Guidance, the low-frequency and high-frequency (now very high-frequency) cetacean isopleths are slightly larger using the updated guidance, and the mid-frequency (now high-frequency) cetacean isopleth is the same as those calculated using the 2018 Technical Guidance. As NMFS is only authorizing takes of mid-frequency (now high-frequency) cetaceans, the isopleths based on the 2018 Technical Guidance will be used as the basis for take numbers and mitigation zones for this IHA.
The 2018 and 2024 thresholds are provided in the tables below. The references, analysis, and methodology used in the development of the thresholds are described in NMFS' 2018 Technical Guidance and in NMFS' 2024 Updated Technical Guidance, which may be accessed at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance.
| Hearing group | PTS onset acoustic thresholds?* (received level) | Impulsive | Non-impulsive |
|---|---|---|---|
| Low-Frequency (LF) Cetaceans | Cell 1: L pk,flat : 219 dB; L E,LF,24h : 183 dB | Cell 2: L E,LF,24h : 199 dB. | |
| Mid-Frequency (MF) Cetaceans | Cell 3: L pk,flat : 230 dB; L E,MF,24h : 185 dB | Cell 4: L E,MF,24h : 198 dB. | |
| High-Frequency (HF) Cetaceans | Cell 5: L pk,flat : 202 dB; L E,HF,24h : 155 dB | Cell 6: L E,HF,24h : 173 dB. | |
| Phocid Pinnipeds (PW) (Underwater) | Cell 7: L pk,flat : 218 dB; L E,PW,24h : 185 dB | Cell 8: L E,PW,24h : 201 dB. | |
| Otariid Pinnipeds (OW) (Underwater) | Cell 9: L pk,flat : 232 dB; L E,OW,24h : 203 dB | Cell 10: L E,OW,24h : 219 dB. | |
| *?Dual metric acoustic thresholds for impulsive sounds: Use whichever results in the largest isopleth for calculating PTS onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure level thresholds associated with impulsive sounds, these thresholds should also be considered. | |||
| Note: Peak sound pressure ( L pk ) has a reference value of 1 µPa, and cumulative sound exposure level ( L E ) has a reference value of 1µPa 2 s. In this table, thresholds are abbreviated to reflect American National Standards Institute standards (ANSI, 2013). However, peak sound pressure is defined by ANSI as incorporating frequency weighting, which is not the intent for this Technical Guidance. Hence, the subscript "flat" is being included to indicate peak sound pressure should be flat weighted or unweighted within the generalized hearing range. The subscript associated with cumulative sound exposure level thresholds indicates the designated marine mammal auditory weighting function (LF, MF, and HF cetaceans, and PW and OW pinnipeds) and that the recommended accumulation period is 24 hours. The cumulative sound exposure level thresholds could be exceeded in a multitude of ways ( i.e., varying exposure levels and durations, duty cycle). When possible, it is valuable for action proponents to indicate the conditions under which these acoustic thresholds will be exceeded. | |||
| Hearing group | AUD INJ onset acoustic thresholds?* (received level) | Impulsive | Non-impulsive |
|---|---|---|---|
| Low-Frequency (LF) Cetaceans | Cell 1: L pk,flat : 222 dB; L E,LF,24h : 183 dB | Cell 2: L E,LF,24h : 197 dB. | |
| High-Frequency (HF) Cetaceans | Cell 3: L pk,flat : 230 dB; L E,HF,24h : 193 dB | Cell 4: L E,HF,24h : 201 dB. | |
| Very High-Frequency (VHF) Cetaceans | Cell 5: L pk,flat : 202 dB; L E,VHF,24h : 159 dB | Cell 6: L E,VHF,24h : 181 dB. | |
| Phocid Pinnipeds (PW) (Underwater) | Cell 7: L pk,flat : 223 dB; L E,PW,24h : 185 dB | Cell 8: L E,PW,24h : 195 dB. | |
| Otariid Pinnipeds (OW) (Underwater) | Cell 9: L pk,flat : 230 dB; L E,OW,24h : 185 dB | Cell 10: L E,OW,24h : 199 dB. | |
| *?Dual metric criteria for impulsive sounds: Use whichever criteria results in the larger isopleth for calculating AUD INJ onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure level criteria associated with impulsive sounds, the PK SPL criteria are recommended for consideration for non-impulsive sources. | |||
| Note: Peak sound pressure level (Lp,0-pk) has a reference value of 1 µPa (underwater) and 20 µPa (in air), and weighted cumulative sound exposure level (LE,p) has a reference value of 1 µPa2s (underwater) and 20 µPa2s (in air). In this table, criteria are abbreviated to be more reflective of International Organization for Standardization standards (ISO 2017; ISO 2020). The subscript "flat" is being included to indicate peak sound pressure are flat weighted or unweighted within the generalized hearing range of marine mammals underwater ( i.e., 7 Hz to 165 kHz) or in air ( i.e., 42 Hz to 52 kHz). The subscript associated with cumulative sound exposure level criteria indicates the designated marine mammal auditory weighting function (LF, HF, and VHF cetaceans, and PW, OW, PA, and OA pinnipeds) and that the recommended accumulation period is 24 hours. The weighted cumulative sound exposure level criteria could be exceeded in a multitude of ways ( i.e., varying exposure levels and durations, duty cycle). When possible, it is valuable for action proponents to indicate the conditions under which these criteria will be exceeded. | |||
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Ensonified Area
Here, we describe operational and environmental parameters of the activity that are used in estimating the area ensonified above the acoustic thresholds, including source levels and transmission loss coefficient.
When the Technical Guidance was initially published (NMFS, 2016), in recognition of the fact that ensonified area/volume could be more technically challenging to predict because of the duration component in the new thresholds, we developed a user spreadsheet that includes tools to help predict a simple isopleth that can be used in conjunction with marine mammal density or occurrence to help predict takes. We note that because of some of the assumptions included in the methods used for these tools, we anticipate that isopleths produced are typically going to be overestimates of some degree, which may result in some degree of overestimation of Level A harassment take. However, these tools offer the best way to predict appropriate isopleths when more sophisticated 3D modeling methods are not available, and NMFS continues to develop ways to quantitatively refine these tools and will qualitatively address the output where appropriate.
The planned survey will entail the use up to two 105 in 3 airguns with a maximum total discharge of 210 in 3 at a tow depth of 3-4 m. UT used modeling by Lamont-Doherty Earth Observatory (L-DEO), which determines the 160 dB rms radius for the airgun source down to a maximum depth of 2,000 m. Received sound levels have been predicted by L-DEO's model (Diebold et al., 2010) as a function of distance from the 2-airgun array. This modeling approach uses ray tracing for the direct wave traveling from the array to the receiver and its associated source ghost (reflection at the air-water interface in the vicinity of the array), in a constant-velocity half-space (infinite homogeneous ocean layer, unbounded by a seafloor).
The planned low-energy survey will acquire data with up to two 105-in 3 GI guns, towed in-line, at a depth of 3-4 m. The shallow-water radii are obtained by scaling the empirically derived measurements from the GOM calibration survey to account for the differences in volume and tow depth between the calibration survey (6,600 in 3 at 6 m tow depth) and the planned survey (210 in 3 at 4 m tow depth). A simple scaling factor is calculated from the ratios of the isopleths calculated by the deep-water L-DEO model, which are essentially a measure of the energy radiated by the source array.
L-DEO's methodology is described in greater detail in UT's IHA application. The estimated distances to the Level B harassment isopleth for the planned airgun configuration are shown in table 5.
| Airgun configuration | Max tow depth (m) | Water depth (m) | Predicted distances (in m) to the Level B harassment threshold |
|---|---|---|---|
| 2 105-in 3 airguns | 4 | <100 | 1,750 |
| Mid frequency cetaceans | |
|---|---|
| PTS SEL cum | 0 |
| PTS Peak | *?1.5 |
| *?The largest distance of the dual criteria (cumulative SEL (SEL cum ) or Peak) was used to estimate threshold distances and potential takes by Level A harassment. | |
Table 6 presents the modeled Level A harassment isopleths for the dolphin species considered here based on L-DEO modeling incorporated in the companion user spreadsheet, for the low-energy surveys with the shortest shot interval ( i.e., greatest potential to cause auditory injury or PTS based on accumulated sound energy) (NMFS 2018). Although NMFS' 2024 Updated Technical Guidance was finalized on October 24, 2024 (89 FR 84872), a similar survey using four 105-in 3 GI guns showed no difference in the auditory injury (Level A harassment) isopleths for delphinid species in the same hearing group (89 FR 81429, October 8, 2024; 89 FR 101555, December 16, 2024), so the values based on the 2018 guidance were used here.
Predicted distances to Level A harassment isopleths, which vary based on marine mammal hearing groups, were calculated based on modeling performed by L-DEO using the Nucleus software program and the NMFS user spreadsheet, described below. The acoustic thresholds for impulsive sounds contained in the NMFS Technical Guidance were presented as dual metric acoustic thresholds using both SEL cum and peak sound pressure metrics (NMFS, 2024). As dual metrics, NMFS considers onset of PTS (Level A harassment) to have occurred when either one of the two metrics is exceeded ( i.e., metric resulting in the largest isopleth). The SEL cum metric considers both level and duration of exposure, as well as auditory weighting functions by marine mammal hearing group.
[top] The SEL cum for the 2-airgun array is derived from calculating the modified farfield signature. The farfield signature is often used as a theoretical representation of the source level. To compute the farfield signature, the source level is estimated at a large distance (right) below the array ( e.g., 9 km), and this level is back projected mathematically to a notional distance of 1 m from the array's geometrical center. However, it has been recognized that the source level from the theoretical farfield signature is never physically achieved at the source when the source is an array of multiple airguns separated in space (Tolstoy et al., 2009). Near the source (at short ranges, distances <1 km), the pulses of sound pressure from each individual airgun in the source array do not stack constructively as they do for the theoretical farfield signature. The pulses from the different airguns spread out in time such that the source levels observed or modeled are the result of the summation of pulses from a few airguns, not the full array (Tolstoy et al., 2009). At larger distances, away from the source array center, sound pressure of all the airguns in the array stack coherently, but not within one time sample, resulting in smaller source levels (a few dB) than the source level derived from the farfield signature. Because the farfield signature does not take into account the large array effect
Auditory injury is unlikely to occur for the dolphin species considered here, given the very small modeled zones of injury for those species (all estimated zones are less than 10 m), in the context of distributed source dynamics.
In consideration of the received sound levels in the near-field as described above, we expect the potential for Level A harassment to be de minimis, even before the likely moderating effects of aversion and/or other compensatory behaviors ( e.g., Nachtigall et al., 2018) are considered. We do not anticipate that Level A harassment is a likely outcome for any of the dolphin species considered here and do not authorize any take by Level A harassment for these species.
The Level A and Level B harassment estimates are based on a consideration of the number of marine mammals that could be within the area around the operating airgun array where received levels of sound =160 dB re 1 µPa rms are predicted to occur. The estimated numbers are based on the densities (numbers per unit area) of marine mammals expected to occur in the area in the absence of seismic surveys. To the extent that marine mammals tend to move away from seismic sources before the sound level reaches the criterion level and tend not to approach an operating airgun array, these estimates likely overestimate the numbers actually exposed to the specified level of sound.
Marine Mammal Occurrence
In this section we provide information about the occurrence of marine mammals, including density or other relevant information which will inform the take calculations.
For the planned survey area in the NW GOM, UT determined that the best source of density data for marine mammal species that might be encountered in the project area was habitat-based density modeling conducted by Garrison et al., (2023). The Garrison et al., (2023) data provides abundance estimates for marine mammal species in the GOM within 40 km 2 hexagons (~3.9 km sides and ~7 km across from each side) on a monthly basis. To calculate expected densities specific to the survey area, UT calculated the mean of the predicted densities from the cells within the combined survey area (primary and alternate survey area) for each species and month. The highest mean monthly density was chosen for each species from the months of January to April ( i.e., the months within which the survey is expected to occur).
Rough-toothed dolphins were not modeled by Garrison et al., (2023) due to a lack of sightings, so habitat-based marine mammal density estimates from Roberts et al., (2016) were used. The Roberts et al., (2016) models consisted of 10 km x 10 km grid cells containing average annual densities for U.S. waters in the GOM. The combined survey area was used to select grid cells from the Roberts et al., (2016) dataset, and the mean of the selected grid cells for rough-toothed dolphins was calculated to estimate the annual average density of the species in the survey area. Estimated densities used and Level B harassment ensonified areas to inform take estimates are presented in table 7.
| Species | Estimated density (#/km 2 ) | Level B ensonified area (km 2 ) |
|---|---|---|
| Atlantic spotted dolphin | b ?0.0043 | 1,522 |
| Bottlenose dolphin? a | b ?0.8596 | 1,522 |
| Rough-toothed dolphin | c ?0.0037 | 1,522 |
| a ?Bottlenose dolphin density estimate does not differentiate between coastal and shelf stocks. | ||
| b ?Density calculated from Garrison et al., (2023). | ||
| c ?Density calculated from Roberts et al., (2016). | ||
Take Estimation
Here we describe how the information provided above is synthesized to produce a quantitative estimate of the take that is reasonably likely to occur and authorized. In order to estimate the number of marine mammals predicted to be exposed to sound levels that would result in Level B harassment, radial distances from the airgun array to the predicted isopleth corresponding to the Level B harassment threshold was calculated, as described above. Those radial distances were then used to calculate the area(s) around the airgun array predicted to be ensonified to sound levels that exceed the harassment thresholds. The area expected to be ensonified on 1 day was determined by multiplying the number of line km possible in 1 day by two times the 160-dB radius plus adding endcaps to the start and beginning of the line. The daily ensonified area was then multiplied by the number of survey days (20 days). The highest mean monthly density for each species was then multiplied by the total ensonified area to calculate the estimated takes of each species.
No takes by Level A harassment are expected or authorized. Estimated exposures and authorized take numbers are shown in table 8.
[top]
| Common name | Stock | Estimated Level B take | Authorized Level B take | Stock abundance? 1 | Percent of stock |
|---|---|---|---|---|---|
| Atlantic spotted dolphin | GOM | 7 | 2 ?26 | 21,506 | 0.12 |
| Bottlenose dolphin? 3 | GOM Western Coastal | 1,309 | 1,309 | 20,759 | 6.31 |
| Northern GOM Continental Shelf | 63,280 | 2.07 | |||
| Rough-toothed dolphin | GOM | 6 | 2 ?14 | 4,853 | 0.29 |
| 1 ?Stock abundance for Atlantic spotted dolphins and bottlenose dolphins was taken from Garrison et al., (2023). Stock abundance for rough-toothed dolphins was taken from Roberts et al., (2016), as Garrison et al., (2023) did not create a model for this species. |
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| 2 ?Authorized take increased to mean group size from Maze-Foley and Mullin (2006). | |||||
| 3 ?Estimated take for bottlenose dolphins is not apportioned to stock, as density information does not differentiate between coastal and shelf dolphins. However, based on the planned survey depths, we expect that most of the takes would be from the coastal stock, but some takes could be from the shelf stock. Percent of stock was calculated as if all takes authorized accrued to the single stock with the lowest population abundance. | |||||
Mitigation
In order to issue an IHA under section 101(a)(5)(D) of the MMPA, NMFS must set forth the permissible methods of taking pursuant to the activity, and other means of effecting the least practicable impact on the species or stock and its habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, and on the availability of the species or stock for taking for certain subsistence uses (latter not applicable for this action). NMFS regulations require applicants for incidental take authorizations to include information about the availability and feasibility (economic and technological) of equipment, methods, and manner of conducting the activity or other means of effecting the least practicable adverse impact upon the affected species or stocks, and their habitat (50 CFR 216.104(a)(11)).
In evaluating how mitigation may or may not be appropriate to ensure the least practicable adverse impact on species or stocks and their habitat, as well as subsistence uses where applicable, NMFS considers two primary factors:
(1) The manner in which, and the degree to which, the successful implementation of the measure(s) is expected to reduce impacts to marine mammals, marine mammal species or stocks, and their habitat. This considers the nature of the potential adverse impact being mitigated (likelihood, scope, range). It further considers the likelihood that the measure will be effective if implemented (probability of accomplishing the mitigating result if implemented as planned), the likelihood of effective implementation (probability implemented as planned); and,
(2) The practicability of the measures for applicant implementation, which may consider such things as cost, and impact on operations.
Vessel-Visual Based Mitigation Monitoring
Visual monitoring requires the use of trained observers (herein referred to as visual protected species observers (PSOs)) to scan the ocean surface visually for the presence of marine mammals. PSOs shall establish and monitor a pre-start clearance zone and, to the extent practicable, a Level B harassment zone (table 5). These zones shall be based upon the radial distance from the edges of the acoustic source (rather than being based on the center of the array or around the vessel itself). During pre-start clearance ( i.e., before ramp-up begins), the pre-start clearance zone is the area in which observations of marine mammals within the zone will prevent airgun operations from beginning ( i.e., ramp-up). The pre-start clearance zone encompasses the area at and below the sea surface out to a radius of 200 m from the edges of the airgun array.
During survey operations ( e.g., any day on which use of the acoustic source is planned to occur, and whenever the acoustic source is in the water, whether activated or not), a minimum of two PSOs must be on duty and conducting visual observations at all times during daylight hours ( i.e., from 30 minutes prior to sunrise through 30 minutes following sunset). Visual monitoring must begin no less than 30 minutes prior to ramp-up and must continue until 1 hour after use of the acoustic source ceases or until 30 minutes past sunset. Visual PSOs must coordinate to ensure 360 degree visual coverage around the vessel from the most appropriate observation posts, and must conduct visual observations using binoculars and the naked eye while free from distractions and in a consistent, systematic, and diligent manner.
PSOs shall establish and monitor a pre-start clearance zone and to the extent practicable, a Level B harassment zone. These zones shall be based upon the radial distance from the edges of the acoustic source (rather than being based on the center of the array or around the vessel itself). Any observations of marine mammals by crew members shall be relayed to the PSO team. During good conditions ( e.g., daylight hours, Beaufort sea state (BSS) 3 or less), visual PSOs shall conduct observations when the acoustic source is not operating for comparison of sightings rates and behavior with and without use of the acoustic source and between acquisition periods, to the maximum extent practicable.
Visual PSOs may be on watch for a maximum of 4 consecutive hours followed by a break of at least 1 hour between watches and may conduct a maximum of 12 hours of observation per 24-hour period.
Pre-Start Clearance and Ramp-Up
Ramp-up (sometimes referred to as "soft start") means the gradual and systematic increase of emitted sound levels from an airgun array. The intent of pre-start clearance observation (30 minutes) is to ensure no marine mammals are observed within the pre-start clearance zone prior to the beginning of ramp-up. The intent of the ramp-up is to warn marine mammals of pending seismic survey operations and to allow sufficient time for those animals to leave the immediate vicinity prior to the sound source reaching full intensity. A ramp-up procedure, involving a stepwise increase in the number of airguns firing and total array volume until all operational airguns are activated and the full volume is achieved, is required at all times as part of the activation of the airgun array. All operators must adhere to the following pre-start clearance and ramp-up requirements:
• The operator must notify a designated PSO of the planned start of ramp-up as agreed upon with the lead PSO; the notification time should not be less than 60 minutes prior to the planned ramp-up in order to allow PSOs time to monitor the pre-start clearance zone for 30 minutes prior to the initiation of ramp-up (pre-start clearance).
• Ramp-ups shall be scheduled so as to minimize the time spent with the source activated prior to reaching the designated run-in.
• One of the PSOs conducting pre-start clearance observations must be notified again immediately prior to initiating ramp-up procedures and the operator must receive confirmation from the PSO to proceed.
• Ramp-up may not be initiated if any marine mammal is within the pre-start clearance zone. If a marine mammal is observed within the pre-start clearance zone during the 30 minutes 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 (15 minutes for small delphinids and 30 minutes for all other species).
[top] • Ramp-up must begin by activating one GI airgun for no less than 5 minutes and then activating the second airgun. The operator must provide information to the PSO documenting that appropriate procedures were followed.
• PSOs must monitor the pre-start clearance zone during ramp-up, and ramp-up must cease and the source must be shut down upon detection of a marine mammal within the pre-start clearance zone. Once ramp-up has begun, observations of marine mammals for which take authorization is granted within the pre-start clearance zone does not require shutdown.
• If the acoustic source is shut down for brief periods ( i.e., less than 30 minutes) for reasons other than implementation of prescribed mitigation ( e.g., mechanical difficulty), it may be activated again without ramp-up if PSOs have maintained constant observation and no detections of marine mammals have occurred within the pre-start clearance zone. For any longer shutdown, pre-start clearance observation and ramp-up are required. Ramp-up may occur at times of poor visibility ( e.g., BSS 4 or greater), including nighttime, if appropriate visual monitoring has occurred with no detections of marine mammals 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.
• Testing of the acoustic source involving all elements requires ramp-up. Testing limited to individual source elements or strings does not require ramp-up but does require a 30-minute pre-start clearance period.
Shutdown Procedures
The shutdown of an airgun array requires the immediate de-activation of all individual airgun elements of the array. Any PSO on duty will have the authority to call for shutdown of the airgun array. The operator must also establish and maintain clear lines of communication directly between PSOs on duty and crew controlling the airgun array to ensure that shutdown commands are conveyed swiftly while allowing PSOs to maintain watch. The shutdown requirement will be waived for small dolphins. As defined here, the small dolphin group is intended to encompass those members of the Family Delphinidae most likely to voluntarily approach the source vessel for purposes of interacting with the vessel and/or airgun array ( e.g., bow riding). This exception to the shutdown requirement applies solely to specific genera of small dolphins- Steno, Stenella, and Tursiops. As Tursiops, Stenella, and Steno are the only species expected to potentially be encountered, there is no shutdown requirement included in the issued IHA for species for which take is authorized. UT must implement shutdown if a marine mammal species for which take was not authorized or a species for which authorization was granted but the authorized takes have been met approaches the Level B harassment zone.
We include this small dolphin exception because shutdown requirements for these species under all circumstances represent practicability concerns without likely commensurate benefits for the animals in question. Small dolphins are generally the most commonly observed marine mammals in the specific geographic region and would typically be the only marine mammals likely to intentionally approach the vessel. As described above, auditory injury is extremely unlikely to occur for the dolphin species considered here, as they are relatively insensitive to sound produced at the predominant frequencies in an airgun pulse while also having a relatively high threshold for the onset of auditory injury ( i.e., permanent threshold shift).
A large body of anecdotal evidence indicates that small dolphins commonly approach vessels and/or towed arrays during active sound production for purposes of bow riding with no apparent effect observed ( e.g., Barkaszi et al., 2012; Barkaszi and Kelly, 2018). The potential for increased shutdowns resulting from such a measure would require the McCall to revisit the missed track line to reacquire data, resulting in an overall increase in the total sound energy input to the marine environment and an increase in the total duration over which the survey is active in a given area.
Vessel Strike Avoidance Mitigation Measures
Vessel personnel should use an appropriate reference guide that includes identifying information on all marine mammals that may be encountered. Vessel operators must comply with the below measures except under extraordinary circumstances when the safety of the vessel or crew is in doubt or the safety of life at sea is in question. 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.
Vessel operators and crews must maintain a vigilant watch for all marine mammals and slow down, stop their vessel, or alter course, as appropriate and regardless of vessel size, to avoid striking any marine mammal. A single marine mammal at the surface may indicate the presence of submerged animals in the vicinity of the vessel; therefore, precautionary measures should always be exercised. A visual observer aboard the vessel must monitor a vessel strike avoidance zone around the vessel (separation 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 be provided sufficient training to (1) distinguish marine mammals from other phenomena and (2) broadly to identify a marine mammal as a whale (defined in this context as sperm whales or baleen whales), or other marine mammals.
Vessel speeds must be reduced to 10 knots (kn) (18.5 kph) or less when mother/calf pairs, pods, or large assemblages of cetaceans are observed near a vessel. The vessel must maintain a minimum separation distance of 500 m from baleen whales. If a baleen whale is sighted within the relevant separation distance, the vessel must steer a course away at 10 kn (18.5 kph) or less until the 500-m separation distance is established. If a whale is observed but cannot be confirmed as a species other than a baleen whale, the vessel operator must assume that it is a baleen whale and take appropriate action. All vessels must maintain a minimum separation distance of 100 m from sperm whales. 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).
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.
[top] Based on our evaluation of the applicant's planned measures, as well as other measures considered by NMFS, NMFS has determined that the mitigation measures provide the means of effecting the least practicable impact on the affected species or stocks and their habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance.
Monitoring and Reporting
In order to issue an IHA for an activity, section 101(a)(5)(D) of the MMPA states that NMFS must set forth requirements pertaining to the monitoring and reporting of such taking. The MMPA implementing regulations at 50 CFR 216.104(a)(13) indicate that requests for authorizations must include the suggested means of accomplishing the necessary monitoring and reporting that will result in increased knowledge of the species and of the level of taking or impacts on populations of marine mammals that are expected to be present while conducting the activities. Effective reporting is critical both to compliance as well as ensuring that the most value is obtained from the required monitoring.
Monitoring and reporting requirements prescribed by NMFS should contribute to improved understanding of one or more of the following:
• Occurrence of marine mammal species or stocks in the area in which take is anticipated ( e.g., presence, abundance, distribution, density);
• Nature, scope, or context of likely marine mammal exposure to potential stressors/impacts (individual or cumulative, acute or chronic), through better understanding of: (1) action or environment ( e.g., source characterization, propagation, ambient noise); (2) affected species ( e.g., life history, dive patterns); (3) co-occurrence of marine mammal species with the activity; or (4) biological or behavioral context of exposure ( e.g., age, calving or feeding areas);
• Individual marine mammal responses (behavioral or physiological) to acoustic stressors (acute, chronic, or cumulative), other stressors, or cumulative impacts from multiple stressors;
• How anticipated responses to stressors impact either: (1) long-term fitness and survival of individual marine mammals; or (2) populations, species, or stocks;
• Effects on marine mammal habitat ( e.g., marine mammal prey species, acoustic habitat, or other important physical components of marine mammal habitat); and,
• Mitigation and monitoring effectiveness.
Vessel-Based Visual Monitoring
As described above, PSO observations will take place during daytime airgun operations. During seismic survey operations, two visual PSOs will be on duty at all times during daytime hours. The operator will work with the selected third-party observer provider to ensure PSOs have all equipment (including backup equipment) needed to adequately perform necessary tasks, including accurate determination of distance and bearing to observed marine mammals. UT must use dedicated, trained, and NMFS-approved PSOs. At least one visual PSO aboard the vessel must have a minimum of 90 days at-sea experience working in those roles, respectively, with no more than 18 months elapsed since the conclusion of the at-sea experience. One visual PSO with such experience shall be designated as the lead for the entire protected species observation team. The lead PSO shall serve as primary point of contact for the vessel operator and ensure all PSO requirements per the IHA are met. To the maximum extent practicable, the experienced PSOs should be scheduled to be on duty with those PSOs with appropriate training but who have not yet gained relevant experience. The PSOs must have no tasks other than to conduct observational effort, record observational data, and communicate with and instruct relevant vessel crew with regard to the presence of marine mammals and mitigation requirements. PSO resumes shall be provided to NMFS for approval. Monitoring shall be conducted in accordance with the following requirements:
• PSOs shall be independent, dedicated, trained visual PSOs and must be employed by a third-party observer provider.
• PSOs shall have no tasks other than to conduct observational effort, collect data, and communicate with and instruct relevant vessel crew with regard to the presence of protected species and mitigation requirements (including brief alerts regarding maritime hazards).
• PSOs shall have successfully completed an approved PSO training course appropriate for their designated task.
• NMFS must review and approve PSO resumes accompanied by a relevant training course information packet that includes the name and qualifications ( i.e., experience, training completed, or educational background) of the instructor(s), the course outline or syllabus, and course reference material as well as a document stating successful completion of the course.
• PSOs must successfully complete relevant training, including completion of all required coursework and passing (80 percent or greater) a written and/or oral examination developed for the training program.
• PSOs must have successfully attained a bachelor's degree from an accredited college or university with a major in one of the natural sciences, a minimum of 30 semester hours or equivalent in the biological sciences, and at least one undergraduate course in math or statistics.
• The educational requirements may be waived if the PSO has acquired the relevant skills through alternate experience. Requests for such a waiver shall be submitted to NMFS and must include written justification. Requests shall be granted or denied (with justification) by NMFS within 1 week of receipt of submitted information. Alternate experience that may be considered includes, but is not limited to (1) secondary education and/or experience comparable to PSO duties; (2) previous work experience conducting academic, commercial, or government-sponsored protected species surveys; or (3) previous work experience as a PSO; the PSO should demonstrate good standing and consistently good performance of PSO duties.
• For data collection purposes, PSOs shall use standardized electronic data collection forms. PSOs shall record detailed information about any implementation of mitigation requirements, including the distance of animals to the airgun array 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 airgun array. If required mitigation was not implemented, PSOs should record a description of the circumstances. At a minimum, the following information must be recorded:
? Vessel name, vessel size and type, maximum speed capability of vessel;
? Dates (MM/DD/YYYY) of departures and returns to port with port name;
? PSO names and affiliations, PSO ID (initials or other identifier);
? Date (MM/DD/YYYY) and participants of PSO briefings;
? Visual monitoring equipment used (description);
? PSO location on vessel and height (meters) of observation location above water surface;
? Watch status (description);
? Dates (MM/DD/YYYY) and times (Greenwich Mean Time/UTC) of survey on/off effort and times (GMC/UTC) corresponding with PSO on/off effort;
[top] ? Vessel location (decimal degrees) when survey effort began and ended and vessel location at beginning and end of visual PSO duty shifts;
? Vessel location (decimal degrees) at 30-second intervals if obtainable from data collection software, otherwise at practical regular interval;
? Vessel heading (compass heading) and speed (knots) at beginning and end of visual PSO duty shifts and upon any change;
? Water depth (meters) (if obtainable from data collection software);
? Environmental conditions while on visual survey (at beginning and end of PSO shift and whenever conditions changed significantly), including BSS and any other relevant weather conditions including cloud cover, fog, sun glare, and overall visibility to the horizon;
? Factors that may have contributed to impaired observations during each PSO shift change or as needed as environmental conditions changed (description) ( e.g., vessel traffic, equipment malfunctions); and
? Vessel/Survey activity information (and changes thereof) (description), such as airgun power output while in operation, number and volume of airguns operating in the array, tow depth of the array, and any other notes of significance ( i.e., pre-start clearance, ramp-up, shutdown, testing, shooting, ramp-up completion, end of operations, streamers, etc. ).
• Upon visual observation of any marine mammals, the following information must be recorded:
? Sighting ID (numeric);
? Watch status (sighting made by PSO on/off effort, opportunistic, crew, alternate vessel/platform);
? Location of PSO/observer (description);
? Vessel activity at the time of the sighting ( e.g., deploying, recovering, testing, shooting, data acquisition, other);
? PSO who sighted the animal/ID;
? Time/date of sighting (GMT/UTC, MM/DD/YYYY);
? Initial detection method (description);
? Sighting cue (description);
? Vessel location at time of sighting (decimal degrees);
? Water depth (meters);
? Direction of vessel's travel (compass direction);
? Speed (knots) of the vessel from which the observation was made;
? Direction of animal's travel relative to the vessel (description, compass heading);
? Bearing to sighting (degrees);
? Identification of the animal ( e.g., genus/species, lowest possible taxonomic level, or unidentified) and the composition of the group if there is a mix of species;
? Species reliability (an indicator of confidence in identification) (1 = unsure/possible, 2 = probable, 3 = definite/sure, 9 = unknown/not recorded);
? Estimated distance to the animal (meters) and method of estimating distance;
? Estimated number of animals (high/low/best) (numeric);
? Estimated number of animals by cohort (adults, yearlings, juveniles, calves, group composition, etc. );
? 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);
? Detailed behavior observations ( e.g., number of blows/breaths, number of surfaces, breaching, spyhopping, diving, feeding, traveling; as explicit and detailed as possible; note any observed changes in behavior);
? Animal's closest point of approach (meters) and/or closest distance from any element of the airgun array;
? Description of any actions implemented in response to the sighting ( e.g., delays, shutdown, ramp-up) and time and location of the action;
? Photos (Yes/No);
? Photo Frame Numbers (List of numbers); and
? Conditions at time of sighting (Visibility; BSS).
Reporting
UT shall submit a draft comprehensive report on all activities and monitoring results within 90 days of the completion of the survey or expiration of the IHA, whichever comes sooner. The report must describe all activities conducted and sightings of marine mammals, must provide full documentation of methods, results, and interpretation pertaining to all monitoring, and must summarize the dates and locations of survey operations and all marine mammal sightings (dates, times, locations, activities, associated survey activities). The draft report shall also include geo-referenced time-stamped vessel tracklines for all time periods during which airgun arrays were operating. Tracklines should include points recording any change in airgun array status ( e.g., when the sources began operating, when they were turned off, or when they changed operational status such as from full array to single gun or vice versa). Geographic Information System files shall be provided in Environmental Systems Research Institute shapefile format and include the UTC date and time, latitude in decimal degrees, and longitude in decimal degrees. All coordinates shall be referenced to the WGS84 geographic coordinate system. In addition to the report, all raw observational data shall be made available. The report must summarize data collected as described above in Monitoring and Reporting. A final report must be submitted within 30 days following resolution of any comments on the draft report.
Reporting Injured or Dead Marine Mammals
Discovery of injured or dead marine mammals -In the event that personnel involved in the survey activities discover an injured or dead marine mammal, UT shall report the incident to the Office of Protected Resources (OPR), NMFS and the NMFS, Southeast Regional Stranding Coordinator 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 strike of a marine mammal by any vessel involved in the activities covered by the authorization, UT shall report the incident to OPR, NMFS, and the NMFS Southeast Regional Stranding Coordinator as soon as feasible. The report must include the following information:
• Time, date, and location (latitude/longitude) of the incident;
• 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 measure were taken, if any, to avoid strike;
• Environmental conditions ( e.g., wind speed and direction, BSS, cloud cover, visibility) immediately preceding the strike;
• Species identification (if known) or description of the animal(s) involved;
[top] • Estimated size and length of the 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 present 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).
Negligible Impact Analysis and Determination
NMFS has defined negligible impact as an impact resulting from the specified activity that cannot be reasonably expected to, and is not reasonably likely to, adversely affect the species or stock through effects on annual rates of recruitment or survival (50 CFR 216.103). A negligible impact finding is based on the lack of likely adverse effects on annual rates of recruitment or survival ( i.e., population-level effects). An estimate of the number of takes alone is not enough information on which to base an impact determination. In addition to considering estimates of the number of marine mammals that might be "taken" through harassment, NMFS considers other factors, such as the likely nature of any impacts or responses ( e.g., intensity, duration), the context of any impacts or responses ( e.g., critical reproductive time or location, foraging impacts affecting energetics), as well as effects on habitat, and the likely effectiveness of the mitigation. We also assess the number, intensity, and context of estimated takes by evaluating this information relative to population status. Consistent with the 1989 preamble for NMFS' implementing regulations (54 FR 40338, September 29, 1989), the impacts from other past and ongoing anthropogenic activities are incorporated into this analysis via their impacts on the baseline ( e.g., as reflected in the regulatory status of the species, population size and growth rate where known, ongoing sources of human-caused mortality, or ambient noise levels).
To avoid repetition, the discussion of our analysis applies to Atlantic spotted dolphins, bottlenose dolphins, and rough-toothed dolphins, given that the anticipated effects of this activity on these different marine mammal stocks are expected to be similar. There is little information about the nature or severity of the impacts, or the size, status, or structure of any of these species or stocks that would lead to a different analysis for this activity.
NMFS does not anticipate that serious injury or mortality would occur as a result of UT's planned survey, even in the absence of mitigation, and no serious injury or mortality is authorized. As discussed in the Potential Effects of Specified Activities on Marine Mammals and Their Habitat section above, non-auditory physical effects and vessel strike are not expected to occur. NMFS expects that all potential take will be in the form of Level B behavioral harassment in the form of temporary avoidance of the area or decreased foraging (if such activity was occurring), responses that are considered to be of low severity, and with no lasting biological consequences ( e.g., Southall et al., 2007, 2021). These low-level impacts of behavioral harassment are not likely to impact the overall fitness of any individual or lead to population level effects of any species. As described above, auditory injury (Level A harassment) is not expected to occur given the estimated small size of the Level A harassment zones.
In addition, the maximum expected Level B harassment zone around the survey vessel is 1,750 m. Therefore, the ensonified area surrounding the vessel is relatively small compared to the overall distribution of animals in the area and their use of the habitat. Feeding behavior is not likely to be significantly impacted as prey species are mobile and are broadly distributed throughout the survey area; therefore, marine mammals that may be temporarily displaced during survey activities are expected to be able to resume foraging once they have moved away from areas with disturbing levels of underwater noise. Because of the short duration (20 survey days) and temporary nature of the disturbance and the availability of similar habitat and resources in the surrounding area, the impacts to marine mammals and marine mammal prey species are not expected to cause significant or long-term fitness consequences for individual marine mammals or their populations.
Additionally, the acoustic "footprint" of the planned survey will be very small relative to the ranges of all marine mammals that would potentially be affected. Sound levels will increase in the marine environment in a relatively small area surrounding the vessel compared to the range of the marine mammals within the planned survey area. The seismic array will be active 24 hours per day throughout the duration of the planned survey. However, the very brief overall duration of the planned survey (20 survey days) will further limit potential impacts that may occur as a result of the planned activity.
There are no rookeries, mating, or calving grounds known to be biologically important to marine mammals within the planned survey area and there are no feeding areas known to be biologically important to marine mammals within the survey area. There is no designated critical habitat for any ESA-listed marine mammals within the project area.
In summary and as described above, the following factors support our determination that the impacts resulting from this activity are not expected to adversely affect any of the species or stocks through effects on annual rates of recruitment or survival:
• No serious injury or mortality is anticipated or authorized;
• No auditory injury (Level A harassment) is anticipated or authorized;
• The planned activity is temporary and of relatively short duration (23 days total with 20 days of planned survey activity);
• The anticipated impacts of the planned activity on marine mammals will be temporary behavioral changes due to avoidance of the ensonified area, which is relatively small (see tables 5 and 6);
• The availability of alternative areas of similar habitat value for marine mammals to temporarily vacate the survey area during the survey to avoid exposure to sounds from the activity is readily abundant;
• The potential adverse effects on fish or invertebrate species that serve as prey species for marine mammals from the planned survey will be temporary and spatially limited and impacts to marine mammal foraging will be minimal; and
• The mitigation measures are expected to reduce the number and severity of takes, to the extent practicable, by visually detecting marine mammals within the established zones and implementing corresponding mitigation measures ( e.g., delay; ramp-up).
Based on the analysis contained herein of the likely effects of the specified activity on marine mammals and their habitat, and taking into consideration the implementation of the monitoring and mitigation measures, NMFS finds that the total marine mammal take from the planned activity will have a negligible impact on all affected marine mammal species or stocks.
Small Numbers
[top] As noted previously, only take of small numbers of marine mammals may
The number of takes NMFS is authorizing is below one-third of the modeled abundance for all relevant populations (specifically, take of individuals is less than 7 percent of the most appropriate abundance estimate for each stock, see table 7). This is conservative because this approach assumes all takes are of different individual animals, which is likely not the case. Some individuals may be encountered multiple times in a day, but PSOs would count them as separate individuals if they cannot be identified.
Based on the analysis contained herein of the planned activity (including the mitigation and monitoring measures) and the anticipated take of marine mammals, NMFS finds that small numbers of marine mammals would be taken relative to the population size of the affected species or stocks.
Unmitigable Adverse Impact Analysis and Determination
There are no relevant subsistence uses of the affected marine mammal stocks or species implicated by this action. Therefore, NMFS has determined that the total taking of affected species or stocks would not have an unmitigable adverse impact on the availability of such species or stocks for taking for subsistence purposes.
Endangered Species Act
Section 7(a)(2) of the ESA of 1973 (16 U.S.C. 1531 et seq. ) requires that each Federal agency insure that any action it authorizes, funds, or carries out is not likely to jeopardize the continued existence of any endangered or threatened species or result in the destruction or adverse modification of designated critical habitat. To ensure ESA compliance for the issuance of IHAs, NMFS consults internally whenever we propose to authorize take for endangered or threatened species.
No incidental take of ESA-listed species are authorized or expected to result from this activity. Therefore, NMFS has determined that formal consultation under section 7 of the ESA is not required for this action.
National Environmental Policy Act
To comply with the National Environmental Policy Act of 1969 (NEPA; 42 U.S.C. 4321 et seq. ) and NOAA Administrative Order (NAO) 216-6A, NMFS must review our proposed action ( i.e., the issuance of an IHA) with respect to potential impacts on the human environment.
This action is consistent with categories of activities identified in Categorical Exclusion B4 (IHAs with no anticipated serious injury or mortality) of the Companion Manual for NAO 216-6A, which do not individually or cumulatively have the potential for significant impacts on the quality of the human environment and for which we have not identified any extraordinary circumstances that would preclude this categorical exclusion. Accordingly, NMFS has determined that the issuance of the IHA qualifies to be categorically excluded from further NEPA review.
Authorization
NMFS has issued an IHA to UT for the potential harassment of small numbers of three marine mammal species incidental to the marine geophysical survey in the NW GOM that includes the previously explained mitigation, monitoring, and reporting requirements.
Dated: January 14, 2025.
Catherine Marzin,
Deputy Director, Office of Protected Resources, National Marine Fisheries Service.
[FR Doc. 2025-01143 Filed 1-16-25; 8:45 am]
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