EK60 Water Column Sonar Data Collected During DY0801

Echo Integration-Trawl Surveys of Walleye Pollock in the Shumagin Islands and Sanak Trough areas of the Gulf of Alaska, 6-15 February, 2008 (DY2008-01). The Midwater Assessment and Conservation Engineering (MACE) program of NOAA National Marine Fisheries Service (NMFS), Alaska Fisheries Science Center (AFSC) conducted acoustic-trawl (AT) stock assessment surveys in the Shumagin Islands and Sanak Trough areas of the Gulf of Alaska (GOA) during the winter of 2008 to estimate the distribution and abundance of walleye pollock (Theragra chalcogramma). This cruise was also used as an opportunity to compare results from acoustic-trawl surveys conducted simultaneously between NOAA Ships Oscar Dyson and Miller Freeman. This survey was conducted onboard NOAA Ship Oscar Dyson, departing from Kodiak, Alaska on 6 February and arriving in Dutch Harbor, Alaska on 15 February. A calibration of the echosounder system was conducted in Three Saints Bay, Kodiak Island, Alaska on 6 February. Both vessels (Freeman accompanying the Dyson) conducted the Shumagin Islands survey (including Shumagin Trough, Stepovak Bay, Renshaw Point, and Unga Strait) 7-12 February. The vessels conducted the survey of Sanak Trough 12-13 February. The experimental intervessel comparison work required that the vessels travel side-by-side along the survey transects at a separation distance of 0.5 nm, and at other times following each other at a distance of 1.0 nm along shorter transects. The intervessel comparison was designed to minimally impact efforts to complete the survey with the Miller Freeman as the primary survey vessel. A calibration of the Dyson echosounder system was conducted at the end of the survey in Captains Bay, Dutch Harbor, Alaska on 15 February. The Dyson arrived in Dutch Harbor, Alaska on 15 February, ending the cruise. The Dyson is a 64 meter fisheries research stern trawler equipped with acoustic and oceanographic instrumentation. The primary acoustic echosounder system installed on the Dyson is a Simrad EK60 scientific split beam echosounder utilizing five frequencies (18, 38, 70, 120, and 200 kHz).