EK80 Water Column Sonar Data Collected During RL2107

The survey domain, from Cape Flattery, WA to Central Baja California, Mexico, was defined primarily by the modeled distribution of potential habitat for the northern subpopulation (stock) of Pacific Sardine (Zwolinski et al., 2011), with a southern extension permitted by available sampling effort. This area was chosen to encompass the anticipated distributions of the northern stock of Pacific Sardine and the central and northern stocks of Northern Anchovy of the west coasts of the U.S., Canada, and Mexico, but it also spanned portions of the southern stock of Pacific Sardine, Pacific Mackerel, Jack Mackerel, Pacific Round Herring, and Pacific Herring. During summer 2021, the west coasts of the United States and Baja California were surveyed using Lasker, Carranza, Lisa Marie, Long Beach Carnage, and USVs. Compulsory transects were nearly perpendicular to the coast and separated by 10 nmi. The survey began off Cape Flattery, WA and the combination of survey platforms progressed southwards toward Punta Abreojos, MX. On Lasker, multi-frequency Wideband Transceivers (18-, 38-, 70-, 120-, 200-, and 333-kHz Simrad EK80 WBTs) were configured with split-beam transducers (Simrad ES18-11, ES38B, ES70-7C, ES120-7C, ES2007C, and ES333-7C). The transducers were mounted on the bottom of a retractable keel or “centerboard”. The keel was retracted (transducers ~5-m depth) during calibration, and extended to the intermediate position (transducers ~7-m depth) during the survey. Exceptions were made during shallow water operations, when the keel was retracted; or during times of heavy weather, when the keel was extended (transducers ~9-m depth) to provide extra stability and reduce the effect of weather-generated noise. Transducer position and motion were measured at 5 Hz using an inertial motion unit (POS-MV; Trimble/Applanix). Final Summer 2021 Report: https://doi.org/10.25923/cadh-x974 Final Summer 2021 Biomass Report: https://doi.org/10.25923/77kp-ww39