Transport, Distribution, and Abundance of Larval and Juvenile Walleye Pollock (Theragra chalcogramma) in the Western Gulf of Alaska

Abstract

The spawning distribution of walleye pollock (Theragra chalcogramma) and subsequent southwesterly drift of eggs, larvae, and juveniles were investigated in Shelikof Strait, March–September 1987. In mid-March, a hydroacoustics survey found that spawning adults were concentrated in the deeper parts of Shelikof Strait, as were eggs collected in this area during an ichthyoplankton survey about 1 mo later. In May, a concentration of young larvae was found 100–150 km to the southwest of the spawning area. In late June and early July, the center of distribution of late larval and early juvenile walleye pollock was further to the southwest, between the Shumagin and Semidi Islands. By August and September, juveniles were mostly distributed downstream of the Shumagin Islands. The rate of drift of eggs and larvae through June was estimated at 4–6 cm/s. The trajectories of satellite-tracked buoys deployed in the region of greatest egg abundance revealed similar patterns to those of the early life stages of walleye pollock. These observations demonstrate that transport is an important factor determining the distribution of pollock larvae in downstream coastal nursery areas.