EK80 Water Column Sonar Data Collected During DY2304

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 Shelikof Strait, Chirikof Shelfbreak, and Marmot Bay areas of the Gulf of Alaska (GOA) in the late winter of 2023 to estimate distribution and abundance of walleye pollock (Gadus chalcogrammus). This survey was conducted aboard NOAA Ship Oscar Dyson (built in 2003, 64 meters, 2500 tons, 3100 hp), a research stern trawler equipped with acoustic and oceanographic instrumentation. The primary water column acoustic instrument for the survey was a Kongsberg EK80 split-beam scientific echosounder system utilizing five frequencies (18, 38, 70, 120, and 200 kHz). The vessel departed Kodiak, Alaska on 4 March and conducted the Shelikof Strait survey 4-11 March, followed by the Chirikof Shelfbreak survey 11-14 March, and Marmot Bay 15-16 March. A calibration of the EK80 echosounder system was conducted prior to starting the previous survey on 12 February; a post-cruise calibration was conducted 13 March in Kaiugnak Bay, Kodiak Island, Alaska. Trawl operations were conducted using an LFS1421 mid-water trawl net.