SUPPLEMENTARY INFORMATION:

Background

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

An authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s), will not have an unmitigable adverse impact on the availability of the species or stock(s) for subsistence uses (where relevant), and if the permissible methods of taking and requirements pertaining to the mitigation, monitoring and reporting of such takings are set forth. NMFS has defined “negligible impact” in 50 CFR 216.103 as an impact resulting from the specified activity that cannot be reasonably expected to, and is not reasonably likely to, adversely affect the species or stock through effects on annual rates of recruitment or survival.

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

On January 19, 2021, we issued a final rule with regulations to govern the unintentional taking of marine mammals incidental to geophysical survey activities conducted by oil and gas industry operators, and those persons authorized to conduct activities on their behalf (collectively “industry operators”), in U.S. waters of the GOA ^[1] over the course of 5 years (86 FR 5322, January 19, 2021). The rule was based on our findings that the total taking from the specified activities over the 5-year period will have a negligible impact on the affected species or stock(s) of marine mammals and will not have an unmitigable adverse impact on the availability of those species or stocks for subsistence uses, and became effective on April 19, 2021.

The regulations at 50 CFR 217.180 et seq. allow for the issuance of LOAs to industry operators for the incidental take of marine mammals during ( printed page 47218) geophysical survey activities and prescribe the permissible methods of taking and other means of effecting the least practicable adverse impact on marine mammal species or stocks and their habitat (often referred to as mitigation), as well as requirements pertaining to the monitoring and reporting of such taking. Under 50 CFR 217.186(e), issuance of an LOA shall be based on a determination that the level of taking will be consistent with the findings made for the total taking allowable under these regulations and a determination that the amount of take authorized under the LOA is of no more than small numbers.

NMFS subsequently discovered that the 2021 rule was based on erroneous take estimates. We conducted another rulemaking using correct take estimates and other newly available and pertinent information relevant to the analyses supporting some of the findings in the 2021 final rule and the taking allowable under the regulations. We issued a final rule in April 2024, effective May 24, 2024 (89 FR 31488, April 24, 2024).

On August 28, 2025, NMFS Office of Protected Resources (OPR) received a request from NMFS Office of Policy (Policy) for reimplementation of the current Incidental Take Regulation (ITR) to avoid a lapse in ITRs offering incidental take coverage for GOA geophysical survey activities. On October 20, 2025, Bureau of Ocean Energy Management (the original petitioner for the current ITRs) submitted a request to be included in the process as a co-petitioner. In response to these requests, NMFS issued a new final rule, effective April 20, 2026, through April 19, 2031 (91 FR 20784, April 17, 2026).

The reimplementation of the regulations continues the established framework for authorization of incidental take through LOAs. The final rule made no changes to the specified activities or the specified geographical region in which those activities would be conducted, and there are no changes to the associated mitigation, monitoring, and reporting requirements.

Summary of Request and Analysis

Fugro plans to test the operational parameters of a bubble gun source against an airgun over 47 lease blocks in the Green Canyon and South Timbalier areas, with water depths ranging from approximately 1,405 to 1,907 meters (m) in the Green Canyon area and approximately 18 to 33.5 m in the South Timbalier area. See section F of the LOA application for a map of the area. Specifically, Fugro plans to assess the maximum subsurface penetration of the bubble gun, compare the data quality between the three streamers planned for use, conduct an analysis of the bubble gun's frequency content, and confirm system readiness. Fugro anticipates using one source vessel with a single 160 cubic inch (in³ ) airgun and the bubble gun source. Please see the LOA application for additional details.

The bubble gun source (HMS-620LF AquaPulse^TM) is an electromechanical acoustic sub-bottom seismic system. The source is impulsive, has a short duration (approximately 4 ms), and a peak-to-peak source level of 220 dB. The source was evaluated based on the specific parameters included in Fugro's application, as well as data available from a recent sound source characterization study (Campo et al., 2025). Notably, the HMS-620LF can be operated as a single source or as an array with multiple HMS-620LF configured to fire simultaneously. Here we evaluated the operation of a single HMS-620LF with a pulse interval of 1.5 seconds, based on Fugro's stated planned operation of this source. Source levels for the single HMS-620LF were taken from Campo et al. (2025) or calculated from the source waveform therein. The resulting PK SPL, RMS SPL, and SEL source levels were 216.9, 210.5, and 187 dB, respectively. The measured source spectrum for the quad configuration from Campo et al. (2025) was used and adjusted to a broadband SEL source level of 187 dB.

In order to determine the appropriate mitigation measures for this source, we compare this source to Tier 2 airguns and established Tier 3 sources (see Ruppel et al. (2022) for a description of source tiering), based on their estimated distances to marine mammal auditory injury onset and behavioral disturbance onset. Estimated distances to auditory injury onset utilized the NMFS Optional User Spreadsheet tool (Version 3.1, 2024) and NMFS (2024) auditory injury weighting functions. For all marine mammal hearing groups, the estimated distances to auditory injury onset were less than 10 m and at most approximately 5 m in the case of Very High-Frequency (VHF) cetaceans. These short ranges imply auditory injury from a single HMS-620LF operating at a pulse interval of 1.5 seconds is unlikely and are generally consistent with Tier 3 sources ( e.g., low energy sparkers). The RMS SPL source level (210.5 dB re 1 µPa) implies a spherical spreading distance of 335 m to the 160 dB re 1 µPa behavioral disturbance threshold for impulsive sources. This range is smaller than those for small airguns, which typically have distances greater than 1 km, and is comparable to some Tier 3 sources ( e.g., sparkers).

Based on these comparisons, we have determined the single HMS-620LF AquaPulse^TM operating at a pulse interval of 1.5 seconds is considered Tier 3. With Tier 3 mitigation, there is no take incidental to use of the bubble gun and therefore we have not included those survey days in our calculation.

Consistent with the preamble to the final rule, the remaining survey effort proposed by Fugro in its LOA request was used to develop LOA-specific take estimates based on the acoustic exposure modeling results described in the preamble (91 FR 20784, April 17, 2026). In order to generate the appropriate take number for authorization, the following information was considered: (1) survey type; (2) location (by modeling zone ^[2] ); (3) number of days; (4) source; and (5) month.^[3] The acoustic exposure modeling performed in support of the rule provides 24-hour exposure estimates for each species, specific to each modeled source and survey type in each zone and month.

Fugro's survey type was not included in the modeled survey types, and use of existing proxies ( i.e., two-dimensional (2D), three-dimensional (3D) narrow-azimuth (NAZ), 3D wide-azimuth (WAZ), Coil) are generally conservative for use in evaluation of Fugro's survey effort, largely due to the greater area covered by the modeled proxies. Summary descriptions of these modeled survey geometries are available in the preamble to the proposed rule (91 FR 9014, 9018, February 24, 2026). In Fugro's case, because these proxies are conservative, the exposure modeling results were generated using the single airgun proxy. Because these results assume use of a 90-in³ airgun, the take numbers authorized through this LOA are considered the most similar to the sound source planned for use by Fugro, as compared to the other proxies modeled for the rule. All other proxies would likely overestimate take due to Fugro's total daily survey area, short total survey duration, and size of the airgun array planned for use.

The survey will take place over approximately 10 days with 6 days of sound source (airgun) operation: 3 days planned in Zone 2 and 3 days planned ( printed page 47219) in Zone 5. The monthly distribution of survey days is not known in advance, though we assume that the planned 5 days of source operation would occur contiguously. Take estimates for each species are based on the time period that produces the greatest value.

Based on the results of our analysis, NMFS has determined that the level of taking expected for this survey and authorized through the LOA is consistent with the findings made for the total taking allowable under the regulations. See table 1 in this notice and table 7 of the rule (91 FR 20784, April 17, 2026).

Small Numbers Determination

Under the rule, NMFS may not authorize incidental take of marine mammals in an LOA if it will exceed “small numbers.” In short, when an acceptable estimate of the individual marine mammals taken is available, if the estimated number of individual animals taken is up to, but not greater than, one-third of the best available abundance estimate, NMFS will determine that the numbers of marine mammals taken of a species or stock are small (see 91 FR 20784, April 17, 2026). For more information, please see NMFS' discussion of small numbers in the 2026 final rule (91 FR 20784, April 17, 2026).

The take numbers for authorization, determined as described in the Summary of Request and Analysis section, are used by NMFS in making the necessary small numbers determinations, through comparison with the best available abundance estimates (see discussion at 91 FR 20784, 20812, April 17, 2026). For this comparison, NMFS' approach is to use the maximum theoretical population, determined through review of current stock assessment reports (SAR; https://www.fisheries.noaa.gov/​national/​marine-mammal-protection/​marine-mammal-stock-assessments) and model-predicted abundance information ( https://seamap.env.duke.edu/​models/​Duke/​GOM/​). Information supporting the small numbers determinations is provided in table 1.

Based on the analysis contained herein of Fugro's proposed survey activity described in its LOA application and the anticipated take of marine mammals, NMFS finds that small numbers of marine mammals will be taken relative to the affected species or stock sizes ( i.e., less than one-third of the best available abundance estimate) and therefore the taking is of no more than small numbers.

Authorization

NMFS has determined that the level of taking for this LOA request is consistent with the findings made for the total taking allowable under the incidental take regulations and that the amount of take authorized under the LOA is of no more than small numbers. Accordingly, we have issued an LOA to Fugro authorizing the take of marine mammals incidental to its geophysical survey activity, as described above.

91 FR 47217