EK80 Water Column Sonar Data Collected During DY2002

The Midwater Assessment and Conservation Engineering (MACE) program of NOAA Fisheries, Alaska Fisheries Science Center (AFSC) conducted an acoustic-trawl (AT) stock assessment survey in the southeastern Aleutian Basin near Bogoslof Island during the winter of 2020 to estimate the distribution and abundance of walleye pollock (Gadus chalcogrammus). This survey was conducted aboard NOAA Ship Oscar Dyson, a 64 meter research stern trawler equipped with acoustic and oceanographic instrumentation. The primary acoustic instrument for the survey was a Simrad EK80 split-beam echosounder system utilizing six frequencies (18, 38, 70, 120, 200, and 333 kHz). The vessel departed Sand Point, Alaska on 17 February transiting toward the southeast Aleutian Basin. The survey was conducted 19-23 February, 2020, between 167 and 170 W longitude south of Bogoslof Island and north of Unalaska, Umnak Islands, and the Islands of Four Mountains. Research trawls were conducted in Shelikof Strait on 18 and 27 February and the vessel arrived in Kodiak, Alaska to end the cruise on 28 February. A calibration of the echosounder system was conducted at the beginning of the previous cruise on 12 February in Uganik Bay, Kodiak Island, Alaska.