EK80 Water Column Sonar Data Collected During DY2003

The Midwater Assessment and Conservation Engineering (MACE) program of NOAA Fisheries, Alaska Fisheries Science Center (AFSC) conducted acoustic-trawl (AT) stock assessment surveys in the Shelikof Strait area of the Gulf of Alaska (GOA) in the late winter/early spring of 2020 to estimate 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 water column acoustic instrument for the survey was a Simrad EK80 split-beam scientific echosounder system utilizing six frequencies (18, 38, 70, 120, 200, and 333 kHz). The vessel departed Kodiak, Alaska on 2 March and the Shelikof Strait survey 6-15 March. A calibration of the EK80 echosounder was conducted at the start of the winter 2020 field season on 12 Febrauary in Uganik Bay, Kodiak Island, Alaska and a follow-up post-cruise calibration was conducted in Kalsin Bay, Kodiak Island, Alaska on 16 March.