ME70 Water Column Sonar Data Collected During RL2206

This report provides: 1) a detailed description of the acoustic-trawl method (ATM) used by NOAA’s Southwest Fisheries Science Center for direct assessments of the dominant coastal pelagic species (CPS; i.e.: Pacifc Sardine Sardinops sagax, Northern Anchovy Engraulis mordax, Pacifc Mackerel Scomber japonicus, Jack Mackerel Trachurus symmetricus, and Pacifc Herring Clupea pallasii in the California Current Ecosystem of the west coast of the United States (U.S.) and portions of Baja CA, Mexico (MX); and 2) estimates of the biomasses, distributions, and demographics of those CPS encountered in the survey area between 27 June and 30 September 2022. The core region transects were perpendicular to the coast, extending from the shallowest navigable depth (~20 m) to either a distance of 35 nmi or to the 1,000 ftm isobath, whichever was farthest. Compulsory transects were spaced 10 nmi-apart in areas of historic CPS abundance (e.g., between Cape Flattery and Newport, and between San Francisco and San Diego) and 20-nmi apart elsewhere. When CPS were observed within the westernmost 3 nmi of a transect, that transect and the next one to the south were extended in 5-nmi increments until no CPS were observed in the last 3 nmi of the extension, to a maximum extension of 50 nmi. If a transect was extended, the ensuing transect was extended by the same amount. Multi-frequency Wide-Bandwidth Transceivers (18-, 38-, 70-, 120-, 200-, and 333-kHz Simrad EK80 WBTs; Kongsberg) were confgured with split-beam transducers (Simrad ES18-11, ES38B, ES70-7C, ES120-7C, ES200-7C, and ES333-7C, respectively; Kongsberg). The transducers were mounted on the bottom of a retractable keel or "centerboard". The keel was retracted (transducers at ~5-m depth) during calibration, and extended to the intermediate position (transducers at ~7-m depth) during the survey. Exceptions were made during shallow water operations, when the keel was retracted; or during times of heavy weather, when the keel was extended (transducers at ~9-m depth) to provide extra stability and reduce the efect of weather-generated noise. In addition, acoustic data were also collected using a multibeam echosounder (Simrad ME70; Kongsberg), multibeam sonar (Simrad MS70; Kongsberg), scanning sonar (Simrad SX90; Kongsberg), acoustic Doppler current profler and echosounder (Simrad EC150-3C, Kongsberg), and a separate ADCP (Ocean Surveyor OS75; Teledyne RD Instruments). Transducer position and motion were measured at 5 Hz using an inertial motion unit (Applanix POS-MV; Trimble).