Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to a Marine Geophysical Survey in the Nauru Basin of Greater Micronesia in the Northwest Pacific Ocean

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 specific geographic 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 cited above are included in the relevant sections below.

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 preliminarily determined that the issuance of the proposed IHA qualifies to be categorically excluded from further NEPA review.

Summary of Request

On June 6, 2024, NMFS received a request from the Scripps Institution of Oceanography (SIO) for an IHA to take marine mammals incidental to a marine geophysical survey in the Nauru Basin of greater Micronesia in the northwest (NW) Pacific Ocean. The application was deemed adequate and complete on July 30, 2024. SIO's request is for take of 27 species of marine mammals, by Level B harassment only. Neither SIO nor NMFS expect serious injury or mortality to result from this activity and, therefore, an IHA is appropriate.

Description of Proposed Activity

Overview

Researchers from the Woods Hole Oceanographic Institution (WHOI) and University of Houston, with funding from the National Science Foundation (NSF), and implementation by SIO, propose to conduct a low-energy marine seismic survey using airguns as the acoustic source from the research vessel (R/V) Sikuliaq ( Sikuliaq), which is owned by NSF and operated by the University of Alaska Fairbanks (UAF). The proposed survey would occur in the Nauru Basin of greater Micronesia in the NW Pacific Ocean from approximately December 2024 to January 2025. The proposed survey would occur in International Waters and within the Exclusive Economic Zone (EEZ) of the Republic of Marshall Islands, in water depths ranging from approximately 4,000-6,000 meters (m). To complete this 2-dimensional (2-D) multi-channel seismic (MCS) reflection survey, the Sikuliaq would tow a 4-airgun array with a total discharge volume of ~420 cubic inches (in³ ) at a depth of 3 m, operated by marine technicians from SIO. The airgun array receiver would consist of a 1,200 m long solid-state hydrophone streamer. The airguns would fire at a shot interval of 30 m. Approximately 3,158 kilometers (km) of seismic acquisition is planned. Airgun arrays would introduce underwater sounds that may result in take, by Level B harassment, of marine mammals.

The purpose of the proposed survey is to examine magnetic reversals to help determine the process that causes changes in the Earth's magnetic field. The proposed seismic surveys are a prerequisite for processing magnetic data, as they will provide crucial information on the structure of the oceanic crust that is used to model the source of the magnetic signals.

Dates and Duration

The R/V Sikuliaq would likely mobilize from Honolulu, Hawaii, on December 7, 2024, and demobilize in Pohnpei, Federated States of Micronesia, on January 6, 2025, after the survey is completed. The survey is expected to last 27 days, including approximately 14 days of seismic operations and 13 days of transit.

Specific Geographic Region

The proposed survey would occur within approximately 6-20° N, 154-167° E, in International Waters and within the EEZ of the Republic of Marshall Islands, in water depths ranging from approximately 4,000 to 6,000 m. The region where the survey is proposed to occur is depicted in figure 1; the tracklines could occur anywhere within the polygon shown in figure 1. Representative survey tracklines are shown; however, some deviation in actual tracklines, including the order of survey operations, could be necessary for reasons such as science drivers, poor data quality, inclement weather, or mechanical issues with the research vessel and/or equipment. The R/V Sikuliaq would likely mobilize from Honolulu, Hawaii and demobilize in Pohnpei, Federated States of Micronesia.

Figure 1—Location of the Proposed Seismic Survey in the Nauru Basin of Greater Micronesia in the NW Pacific Ocean

Representative survey tracklines are included in the figure; however, the tracklines could occur anywhere within the survey area.

Detailed Description of the Specified Activity

The procedures to be used for the proposed survey would be similar to those used during previous seismic surveys by SIO and would use conventional seismic methodology. The survey would involve one source vessel, R/V Sikuliaq, which is owned by NSF and operated by UAF. During the low-energy MCS seismic reflection survey, R/V Sikuliaq would tow two strings, each with two Generator-Injector (GI) airguns. During the survey, both strings, totaling four active airguns with a total discharge volume of 420 in³ , would be used. The two airgun strings would be spaced 11 m apart and would be towed approximately 25 m behind the vessel. The airgun array configurations are illustrated in figure 2-11 of NSF and the U.S. Geological Survey's (USGS) Programmatic Environmental Impact Statement (PEIS; NSF-USGS, 2011). (The PEIS is available online at: https://www.nsf.gov/geo/oce/envcomp/usgs-nsf-marine-seismic-research/nsf-usgs-final-eis-oeis_3june2011.pdf ). The receiving system would consist of a 1,200 m long solid-state hydrophone streamer. As the airgun arrays are towed along the survey lines, the hydrophone streamer would transfer the data to the on-board processing system.

Approximately 3,158 km of seismic acquisition are planned. The survey would take place in water depths ranging from approximately 4,000 to 6,000 m. In addition to the operations of the airgun array, the ocean floor would be mapped with the Kongsberg EM 304 and the Kongsberg EM 710 multibeam echosounder (MBES), and a Knudsen Chirp 3260 sub-bottom profiler (SBP). A Teledyne RDI 75 kilohertz (kHz) Ocean Surveyor Acoustic Doppler Current Profiler (ADCP) would be used to measure water current velocities, and a passive sea surface magnetometer and a shipboard gravitometer would also be used. Take of marine mammals is not expected to occur incidental to use of the MBES, SBP, and ADCP, whether or not the airguns are operating simultaneously with the other sources. Given their characteristics ( e.g., narrow downward-directed beam), marine mammals would experience no more than one or two brief ping exposures, if any exposure were to occur. NMFS does not expect that the use of these sources presents any reasonable potential to cause take of marine mammals.

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

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 about these species ( e.g., physical and behavioral descriptions) may be found on NMFS' website ( https://www.fisheries.noaa.gov/find-species ). NMFS refers the reader to the aforementioned source for general information regarding the species listed in table 1.

The populations of marine mammals found in the survey area do not occur within the U.S. EEZ and therefore, are not assessed in NMFS' Stock Assessment Reports (SARs). For most species, there are no stocks defined for management purposes in the survey area, and NMFS is evaluating impacts at the species level and ranges for most species evaluated here are considered to be the North Pacific. As such, information on potential biological removal level (PBR; defined by the MMPA as the maximum number of animals, not including natural mortalities, that may be removed from a marine mammal stock while allowing that stock to reach or maintain its optimum sustainable population) and annual levels of serious injury and mortality from anthropogenic sources are not available for these marine mammal populations. Abundance estimates for marine mammals in the survey location were calculated using density data for marine mammals from a US Navy Technical Report for the region (DoN, 2018). The area covered in this report include the Mariana Islands Training and Testing (MITT) Study Area, within approximately 6-23° N, 122-150° E, and the Transit Corridor which spans from the MITT Study Area to the International Date Line.These abundance estimates are considered the best scientific information available on the abundance of marine mammal populations in the area.

Table 1 lists all species or stocks for which take is expected and proposed to be authorized for this activity and summarizes information related to the population or stock, including regulatory status under the MMPA and Endangered Species Act (ESA).