The Passive Acoustic Analysis for the California Current Cetacean and Ecosystem Assessment Survey (CalCurCEAS)

Overview

The 2024 California Current Cetacean and Ecosystem Assessment Survey (CalCurCEAS) was conducted by the Marine Mammal and Turtle Division (MMTD) of NOAA Fisheries’ Southwest Fisheries Science Center (SWFSC). The survey was conducted over the course of 6 legs aboard the M/V Bold Horizon between July 24th and December 5th 2024. The primary objectives of CalCurCEAS 2024 was to collect visual sightings data for marine mammals and seabirds, passive acoustic data for cetaceans, biopsy tissue samples for cetaceans and environmental DNA samples. These datasets will be used for a suite of analyses that support MMTD’s fulfillment of regulatory requirements and scientific initiatives, including marine mammal stock assessments for stakeholders such as the US Navy and the Bureau of Ocean Energy Management (BOEM).

Why Drifting Acoustic Recorders

Passive acoustic monitoring (PAM) of marine mammals provides a non-invasive tool for studying marine mammals, allowing researchers to detect species in no or low visibility conditions and track their presence over long periods. It helps identify deep diving creatures, such as beaked whales

Drifting Acoustic Recorders in the California Current

The passive acoustics component of CalCurCEAS 2024 was comprised of deploying drifting acoustic recording buoys at predetermined locations in the survey area. Buoys were deployed on all legs except for leg 1 due to it’s transitory nature (re-positioning the vessel from San Diego to the north end of the study area). Buoys were then left to drift at sea between 2-14 days before being retrieved.

Data from those buoys were downloaded and then processed to look for specific species. More detail can be found on the following pages.

Study Area

Our study area encompassed the entire west coast exclusive economic zone (EEZ), from the boarder of Canada to the north to the boarder of Mexico to the south, and the near coast region to the east to 200 nmi west. The map below shows the proposed survey tracklines and drifting acoustic buoy deployment locations at trackline intersections (large red numbers and letters). The deployment numbers at each intersection represented proposed primary deployment locations, while the letters represented secondary locations. The red outlined polygons represent wind energy areas on the west coast.

CalCurCEAS 2025 study area with tracklines. There is both an inshore and offshore strata. The red polygons in the inshore strata represent Wind Energy Areas (WEAs). The blue, black and brown numbers on the tracklines represent the line numbers and the larger red letters and numbers at the intersection of the tracklines are potential drifting buoy deployment locations.

Note

This study was funded by the U.S. Department of the Interior, Bureau of Ocean Energy Management (BOEM), Environmental Studies Program, Washington, DC, through Interagency Agreement Number M24PG00021 with the Southwest Fisheries Science Center. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the opinions or policies of BOEM, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.