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Preliminary Results of the Gulf of Alaska EIT Pollock Survey

The MACE Program conducted a feasibility echo integration-trawl (EIT) survey of walleye pollock between 4 June and 16 July 2003 on the central Gulf of Alaska shelf. The principal objective of the survey was to collect echo integration and trawl data to estimate midwater pollock abundance and distribution. Acoustic data were collected with Simrad EK500 and EK60 quantitative echo-sounding systems on the NOAA ship Miller Freeman.

Figure 1, see caption

Three split-beam transducers (38 kHz, 120 kHz, and 200 kHz) were used to collect acoustic data. Results presented here are based on Simrad EK500 38-kHz data. Midwater and near-bottom echosign were sampled using an Aleutian Wing 30/26 midwater trawl. On- or near-bottom echosign was sampled with a Poly nor’eastern trawl with roller gear. A Marinovich herring trawl was used to target age-0 pollock and macrozooplankton. The survey design consisted of parallel transects at 20 nmi spacing which extended from the Shumagin Islands to Montague Island off Prince William Sound. Areas around the Shumagin Islands, Mitrofania Island, Nakchamik Island, Alitak Bay, Barnabas Trough, Chiniak Trough, Marmot Bay, and Prince William Sound were surveyed along closer spaced transects of 1-8 nmi. There were also exploratory excursions into some of the bays on southeast Kenai Peninsula (Fig. 1 above). Echo integration and trawl data were collected during daylight hours (typically between 0500 and 2300). Nighttime operations included additional trawling, trial trawling with an opening-closing net, target strength data collection, and acoustic system testing.


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