Echo integration-trawl survey results for walleye pollock (Theragra chalcogramma) on the Bering Sea shelf and slope during summer 2000

Abstract

Walleye pollock (Theragra chalcogramma) abundance and distribution in midwater were assessed on the eastern Bering Sea shelf and slope between 7 June and 2 August 2000, using echo integration-trawl (EIT) survey techniques aboard the NOAA ship Miller Freeman. Pollock were surveyed from Port Moller, Alaska, to the U.S./Russia Convention Line, including some trackline that extended into the "horseshoe area" based on results from the summer 1999 EIT survey. Results showed that east of the Pribilof Islands (i.e., east of 170° long.), pollock were most concentrated north of Unimak Island, they decreased in abundance around the Pribilof Islands, and reached peak abundances west of the Pribilofs Islands (i.e., west of 170° long.) southwest of St. Matthew Island. East of the Pribilof Islands, the 1992 year class was most abundant by numbers, followed by the 1995 year class. West of the Pribilof Islands, the 1996 year class predominated, followed by 1998 and 1997 year classes. Estimated pollock abundance in midwater (14 m below the surface to 3 m off bottom) was 3.05 million metric tons (t) for the total survey area. Numbers of pollock were estimated to be 7.63 billion. East of 170°W long., estimated pollock abundance was 0.89 million t. West of 170°W long., estimated abundance was 2.16 million t. Thirteen percent of the total biomass was inside the Steller sea lion Conservation Area (SCA). Proportions of pollock biomass estimated east and west of 170°W long., and inside and outside the SCA, were similar to that observed during the four summer EIT surveys conducted since 1994.


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