EK80 Water Column Sonar Data Collected During DY2207

The Midwater Assessment and Conservation Engineering (MACE) program of NOAA Fisheries, Alaska Fisheries Science Center (AFSC), conducted an acoustic-trawl (AT) stock assessment survey on the Easter Bering Sea shelf from Bristol Bay to U.S.-Russia Convention Line in the late spring and summer of 2022 to estimate the 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). Trawl operations were conducted using an LFS1421 mid-water trawl net. The survey was conducted in three legs starting and ending in Dutch Harbor, Alaska with intermediate port calls in Dutch Harbor. Survey leg 1 was conducted 3-15 June, leg 2 was 22 June to 8 July, and leg 3 was 20 July to 5 August; the dates listed are for actual survey operations and do not include the additional transit time between port and area of operations. The delay between legs 2 and 3 was due to vessel staffing issues. Calibrations of the EK80 echosounder system were conducted prior to starting the survey (31 May), at the end of leg 2 (9 July), and at the end of the survey (5 August) in Captains Bay, Unalaska Island (Dutch Harbor), Alaska.