Taking and Importing Marine Mammals; Taking Marine Mammals Incidental to Geophysical Surveys Related to Oil and Gas Activities in the Gulf of America

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One LOA issued to WesternGeco is effective from July 1, 2026, through February 29, 2027. The other LOA issued to WesternGeco is effective from August 1, 2026, through March 31, 2027.
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Published Document: 2026-12986 (91 FR 39080)
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AGENCY:
National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce.
ACTION:
Notice; issuance of Letters of Authorization.
SUMMARY:
In accordance with the Marine Mammal Protection Act (MMPA), as amended, its implementing regulations, and NMFS' MMPA regulations for taking marine mammals incidental to geophysical surveys related to oil and gas activities in the Gulf of America (GOA), notification is hereby given that NMFS has issued two separate Letters of Authorization (LOAs) to WesternGeco, LLC (WesternGeco), for the take of marine mammals incidental to geophysical survey activity in the GOA.
DATES:
One LOA issued to WesternGeco is effective from July 1, 2026, through February 29, 2027. The other LOA issued to WesternGeco is effective from August 1, 2026, through March 31, 2027.
Jenna Harlacher, Office of Protected Resources, NMFS, (301) 427-8401.
SUPPLEMENTARY INFORMATION:
Background
Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361et seq.) direct 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 allow for the issuance of LOAs to industry operators for the incidental take of marine mammals during 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
( printed page 39081)
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 Requests and Analysis
Engagement 12
WesternGeco plans to conduct a long offset sparse ocean bottom node (OBN) survey over 1,446 lease blocks in the Green Canyon, Walker Ridge and Atwater Valley areas, with water depths ranging from approximately 256 to 3,370 m. See section F of the LOA application for a map of the area.
WesternGeco plans to use one of the following source configurations: a low-frequency airgun source known as Gemini (also referred to as a dual barbell source), or a conventional airgun array source consisting of 28 elements with a total volume of 5,000 cubic inches (in3
) (0.082 cubic meter) and a low-frequency tuned pulse source (TPS) in tandem. Please see WesternGeco's application for additional details.
The Gemini and TPS were not included in the acoustic exposure modeling developed in support of the rule. However, the Gemini was described and evaluated in support of a previous LOA (88 FR 72739, October 23, 2023) and the TPS was previously described and evaluated in support of previous LOAs (86 FR 37309, 37310, July 15, 2021; 87 FR 55790, 55791, September 12, 2022). We rely on the prior analyses for the Gemini and TPS here. For additional details regarding sources, see section C of the LOA application. Based on this information we have determined there will be no effects of a magnitude or intensity different from those evaluated in support of the rule. NMFS therefore expects that use of modeling results supporting the final rule relating to use of airgun arrays is expected to be conservative as a proxy for use in evaluating potential impacts of use of the Gemini or TPS.
Consistent with the preamble to the 2026 final rule, the survey effort proposed by WesternGeco 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 [i]
); (3) number of days; (4) source; and (5) month [ii]
. To determine the most appropriate proxy array from the exposure modeling, the directionally dependent source level in a plane parallel to the sea surface was compared to the three airgun array sources that were originally modeled, including the 4,130, 5,110, and 8,000 in3
arrays. Out of these three proxies, the source that had the smallest relative error (arithmetic mean difference taken over the azimuthal or vessel bearing angle) was chosen as the most representative proxy. In this case, because WesternGeco may elect to use the specified 28-element, 5,000 in3
airgun array source, the 5,110 in3
had the lowest mean error (1.1 decibels (dB)) and was the airgun array proxy that was selected. 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.
No OBN surveys were included in the modeled survey types, and use of existing proxies (
i.e.,
2D, 3D NAZ, 3D WAZ, Coil) is generally conservative for use in evaluation of 3D OBN 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). Coil was selected as the best available proxy survey type in this case because the spatial coverage of the planned survey is most similar to the coil survey pattern. The planned OBN survey will involve two source vessels sailing along closely spaced survey lines, with daily survey area coverage of approximately 110 square kilometers (km2
) per day, similar to that assumed for the coil survey proxy. Among the different parameters of the modeled survey patterns (
e.g.,
area covered, line spacing, number of sources, shot interval, total simulated pulses), NMFS considers area covered per day to be most influential on daily modeled exposures exceeding Level B harassment criteria. Although WesternGeco is not proposing to perform a survey using the coil geometry, the coil proxy is most representative of the effort planned by WesternGeco in terms of predicted Level B harassment exposures.
The survey will take place over approximately 140 days with 100 days of sound source operation, including 53 days in Zone 5 and 47 days in Zone 7. The monthly distribution of survey days is not known in advance, though we assume that the planned 100 days of source operation would occur contiguously. Take estimates for each species are based on the time period that produces the greatest value.
For the Rice's whale, recent survey data, sightings, and acoustic data support Rice's whale occurrence in waters throughout the GOM between approximately 100 m and 400 m depth along the continental shelf break, and associated habitat-based density modeling has identified similar habitat (
i.e.,
approximately 100 to 400 meter (m) water depths along the continental shelf break) as being Rice's whale habitat (Garrison
et al.,
2023; Soldevilla
et al.,
2022, 2024). NMFS' 2026 proposed rule provided detailed discussion regarding Rice's whale habitat (see,
e.g.,91 FR 9014, 9026, February 24, 2026).
WesternGeco's planned activities will overlap this depth range, with approximately 0.6 percent of the area expected to be ensonified by the survey above root-mean-squared pressure received levels (RMS SPL) of 160 dB (referenced to 1 micropascal (re 1 μPa)) overlapping the 100-400 m isobaths. Therefore, there is some reasonable potential for take of Rice's whale to occur in association with this survey. The generic acoustic exposure modeling results in one take of Rice's whales and we have rounded that up to a group size, authorizing two Rice's whale takes.
Engagement 13
WesternGeco plans to conduct a long offset sparse OBN survey over 1,153 lease blocks in the Green Canyon and Walker Ridge areas, with water depths ranging from approximately 100 to 3,100 m. See section F of the LOA application for a map of the area.
WesternGeco plans to use one of the following source configurations: a low-frequency airgun source known as Gemini (also referred to as a dual barbell source), or a conventional airgun array source consisting of 28 elements with a total volume of 5,000 in3
and a low-frequency tuned pulse source (TPS) in tandem. Please see WesternGeco's application for additional details.
The Gemini and TPS were not included in the acoustic exposure modeling developed in support of the rule. However, the Gemini was described and evaluated in support of a previous LOA (88 FR 72739, October 23, 2023) and the TPS was previously described and evaluated in support of previous LOAs (86 FR 37309, 37310,
( printed page 39082)
July 15, 2021; 87 FR 55790, 55791, September 12, 2022), and we rely on those analyses here. For additional details regarding sources, see section C of the LOA application. Based on this information we have determined there will be no effects of a magnitude or intensity different from those evaluated in support of the rule. NMFS therefore expects that use of modeling results supporting the final rule relating to use of airgun arrays is expected to be conservative as a proxy for use in evaluating potential impacts of use of the Gemini and TPS.
Consistent with the preamble to the final rule, the survey effort proposed by WesternGeco 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 i
); (3) number of days; (4) source; and (5) month ii
. To determine the most appropriate proxy array from the exposure modeling, the directionally dependent source level in a plane parallel to the sea surface was compared to the three airgun array sources which were originally modeled, including the 4,130, 5,110, and 8,000 in3
arrays. Out of these three proxies, the source which had the smallest relative error (arithmetic mean difference taken over the azimuthal or vessel bearing angle) was chosen as the most representative proxy. In this case, because WesternGeco may elect to use the specified 28-element, 5,000 in3
airgun array source, the 5,110 in3
had the lowest mean error (1.1 dB) and was the airgun array proxy that was selected. 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.
No OBN surveys were included in the modeled survey types, and use of existing proxies (
i.e.,
2D, 3D NAZ, 3D WAZ, Coil) is generally conservative for use in evaluation of 3D OBN 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). Coil was selected as the best available proxy survey type in this case because the spatial coverage of the planned survey is most similar to the coil survey pattern. The planned OBN survey will involve two source vessels sailing along closely spaced survey lines, with daily survey area coverage of approximately 110 km2
per day, similar to that assumed for the coil survey proxy. Among the different parameters of the modeled survey patterns (
e.g.,
area covered, line spacing, number of sources, shot interval, total simulated pulses), NMFS considers area covered per day to be most influential on daily modeled exposures exceeding Level B harassment criteria. Although WesternGeco is not proposing to perform a survey using the coil geometry, the coil proxy is most representative of the effort planned by WesternGeco in terms of predicted Level B harassment exposures.
The survey will take place over approximately 140 days with 101 days of sound source operation, including 78 days in Zone 5 and 23 days in Zone 7. The monthly distribution of survey days is not known in advance, though we assume that the planned 101 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 each survey and authorized through each of the LOAs 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).
For each of WesternGeco's respective surveys, the take numbers for authorization are determined as described above in the Summary of Requests and Analysis section. Subsequently, the total incidents of harassment for each species are multiplied by scalar ratios (except in the cases where the take estimate has been rounded up to reflect a group size) to produce a derived product that better reflects the number of individuals likely to be taken within a survey (as compared to the total number of instances of take), accounting for the likelihood that some individual marine mammals may be taken on more than 1 day (see 91 FR 20784, April 17, 2026). The output of this scaling, where appropriate, is incorporated into adjusted total take estimates that are the basis for NMFS' small numbers determinations, as depicted in tables 1 and 2.
Based on the analysis contained herein of WesternGeco's planned survey activities described in their separate LOA applications and the anticipated take of marine mammals, NMFS finds that for each LOA 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 for each LOA.
Authorization
NMFS has determined that the level of taking for each 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 each LOA is of no more than small numbers. Accordingly, we have issued two LOAs to WesternGeco, authorizing the take of marine mammals incidental to its geophysical survey activity, as described above.
Dated: June 24, 2026.
Kimberly Damon-Randall,
Director, Office of Protected Resources, National Marine Fisheries Service.
Footnotes
1.
Pursuant to Executive Order 14172, “Restoring Names That Honor American Greatness,” and Department of the Interior Secretarial Order 3423, “The Gulf of America,” the body of water formerly known as the Gulf of Mexico is now called the Gulf of America.
ii.
Acoustic propagation modeling was performed for two seasons: Winter (December-March) and Summer (April-November). Marine mammal density data is generally available on a monthly basis, and therefore further refines take estimates temporally.