Echo integration-trawl survey results for walleye pollock (Theragra chalcogramma) on the Bering Sea shelf and slope during summer 1999

Abstract

Walleye pollock (Theragra chalcogramma) abundance and distribution in midwater were assessed on the eastern Bering Sea shelf and slope between 12 June and 3 August 1999, using echo integration-trawl survey (EIT) techniques aboard the NOAA ship Miller Freeman. The survey extended from Port Moller, Alaska, to the U.S./Russia Convention Line. Results showed that pollock were absent east of 162°W long. and were relatively abundant around the Pribilof Islands. West of the Pribilof Islands, pollock were rarely found in water shallower than the 100-m isobath. Highest pollock concentrations were at approximately 173° and 177°W long. In 1999, the center of pollock distribution was south and slightly west of the center of distribution observed during previous years (1994,1996,1997). Age distribution was similar east and west of the Pribilofs. The 1996 year class predominated, followed in order of decreasing importance by 1995 and 1992 in the east, and by 1997 and 1995 in the west. Age-1 pollock (1998 year class) were rarely observed. Estimated pollock abundance between 14 m from the surface and 3 m off-bottom was 3.29 million metric tons (t) and 9.6 million fish. East of 170°W long., estimated pollock abundance was 0.89 million t. West of 170°W long., estimated biomass was 2.41 million t. Nine percent (0.30 million t) 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 summer EIT surveys conducted during the 1990s. Estimated pollock abundance in a small region of extended trackline in the "horseshoe area" outside of our normal survey area was 0.060 million t during the first pass through the area on Leg 1 of the cruise, and 0.058 million t during the second pass at the end of Leg 2. Future surveys will include trackline extensions into this area.


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