ME70 Water Column Sonar Data Collected During RL1704

Coastal pelagic fish species (CPS), krill, and their environment within the California Current Ecosystem (CCE) were sampled using multi-frequency echosounders, surface trawls, vertically integrating net tows, a continuous underway fish-egg sampler (CUFES), and conductivity-temperature-depth probes (CTD), and assessed using the Acoustic-Trawl Method (ATM) and Daily Egg Production Method (DEPM) during the Spring CPS Survey aboard the NOAA Fisheries Survey Vessel (FSV) Reuben Lasker (hereafter, Lasker), 21 March to 22 April 2017. The objectives of the survey were to: 1) acoustically map the distributions and estimate the abundances of CPS, e.g., Pacific sardine (Sardinops sagax), Northern anchovy (Engraulis mordax), Pacific herring (Clupea pallasii), Pacific mackerel (Scomber japonicus), and jack mackerel (Trachurus symmetricus);
and krill (euphausiid spp.); 2) characterize their biotic and abiotic environments, and investigate linkages; and 3) gather information regarding their life history parameters. The survey domain encompassed the anticipated distribution of the central sub-population of anchovy. The modeled distribution of potential sardine habitat, and information recently gathered from other research projects (e.g., CalCOFI samples) or the fishing industry (e.g., sardine bycatch) were used to determine whether the survey domain also encompassed the northern sub-population of sardine. Transect positions, lengths, and spaces were adjusted according to the expected distribution of anchovy at the time of the survey. Compulsory transects were nearly perpendicular to the coast with nominal separations of 20 nmi; adaptive transects were placed between compulsory transects to reduce nominal separation to 10 nmi when the survey encountered putative CPS backscatter in echograms, high-density eggs in the CUFES (1 or 0.3 eggs min-1 for anchovy or sardine, respectively), or adults in trawls.
Multi-frequency (18, 38, 70, 120, 200, and 333 kHz) General Purpose Transceivers (Simrad EK60 GPTs) and Wideband Transceivers (Simrad EK80 WBTs) were configured with split-beam transducers (Simrad ES18-11, ES38B, ES70-7C, ES120-7C, ES200-7C, and ES333-7C, respectively). The transducers were mounted on the bottom of a retractable keel or “centerboard”. The keel was retracted (~ 5-m depth) during calibration, and extended to the intermediate position (~7-m depth) during the survey. Exceptions were made during shallow water operations, when the keel was retracted to ~ 5-m depth; or during times of heavy weather, when the keel was extended to ~9-m depth to provide extra stability and reduce the effect of weather-generated noise. The echosounders were calibrated using the standard sphere technique (Demer et al., 2015; Foote et al., 1987)