AFSC/RACE/MACE: Results of 2009 ACOUSTIC-TRAWL SURVEYS OF THE SHUMAGINS, SANAK TROUGH & WESTERN GULF OF ALASKA SHELFBREAK DY0901

Scientists from the Midwater Assessment and Conservation Engineering (MACE) Program of the Alaska Fisheries Science Center's (AFSC) Resource Assessment and Conservation Engineering (RACE) Division routinely conduct echo integration-trawl (EIT) stock assessment surveys in the Gulf of Alaska (GOA) during late winter and early spring to estimate the distribution and abundance of walleye pollock (Theragra chalcogramma). Surveys were conducted in the Shumagin Islands area in 1994-96, 2001-03, and 2005-07 and along the GOA continental shelf break east of Chirikof Island to Barnabas Trench in 2002-07. This report presents the distribution and abundance of walleye pollock for surveys conducted in the Shumagins during February and March 2009.

Collect echo integration data and trawl data necessary to determine the distribution, biomass, and biological composition of walleye pollock in the Shumagins area; Collect pollock target strength data using hull-mounted or lowered transducers for use in scaling echo integration data to estimates of absolute abundance; Calibrate the ER60 and ME70 acoustic system using standard sphere calibration techniques; Conduct a codend-comparison experiment; Collect physical oceanographic data (temperature and salinity profiles) at selected sites, and continuously collect sea surface temperature and salinity data.

The Shumagins region is a critical spawning ground for walleye pollock and annual surveys of pollock age structure and biomass are used to inform GOA pollock stock assesment models. In particular, there is a strong correlation between the abundance of age-1 pollock in the Shumagin Islands survey and year-class strength for the GOA region.

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Acoustic Systems: Simrad ER60 echosounder (18, 38, 70, 120 & 200 kHz) and Simrad ME70 multibeam echosounder. Nets: Midwater = Aleutian wing trawl (headrope/foot rope = 270 ft, vertical opening = 90 ft, codend liners = ? in.; Bottom = Poly Nor'eastern bottom trawl (headrope = 90 ft, footrope = 105 ft, vertical opening = 19 ft, codend liner = 1? in.) Research: lowered 38 kHz acoustic system, multi opening/closing codend (MOCC)

Go to https://www.ngdc.noaa.gov/mgg/wcd/ or email Anderson, Charles (charles.anderson@noaa.gov)

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There was no sampling during the dates of February 21- March 19.

These data were collected in accordance NOAA protocols for fisheries acoustics surveys and related sampling (Alaska Fisheries Science Center), 23 p. Prepared by Midwater Assessment and Conservation Engineering Program, Alaska Fish. Sci. Center, Natl. Mar. Fish. Serv., NOAA. Available online: http://www.afsc.noaa.gov/RACE/midwater/AFSC%20AT%20Survey%20Protocols_Feb%202013.pdf

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Acoustic data were recorded at the five split-beam frequencies using ER60 software and, as a backup, acoustic telegram data were logged with Myriax EchoLog 500 software. Acoustic measurements were collected from 16 m below the sea surface to within 0.5 m of the sounder-detected bottom or a maximum of 1,000 m in deep water. Data were analyzed using Myriax Echoview post-processing software. See National Marine Fisheries Service (NMFS) 2013. NOAA protocols for fisheries acoustics surveys and related sampling (Alaska Fisheries Science Center), 23 p. Prepared by Midwater Assessment and Conservation Engineering Program, Alaska Fish. Sci. Center, Natl. Mar. Fish. Serv., NOAA. Available online: http://www.afsc.noaa.gov/RACE/midwater/AFSC%20AT%20Survey%20Protocols_Feb%202013.pdf