Biochemical Genetic Variation in Walleye Pollock, Theragra chalcogramma: Population Structure in the Southeastern Bering Sea and the Gulf of Alaska

Abstract

The distributions of biochemical genetic variants were used to examine the genetic relationships among populations of walleye pollock, Theragra chalcogramma, located in the southeastern Bering Sea and the Gulf of Alaska. Enzymatic proteins in tissue samples of fish collected from 14 locations were assayed for electrophoretically detectable variants. Twenty-eight loci were tentatively identified, 8 (28%) of which were polymorphic. Only two loci, ME-2 and 6PG, had variants in great enough frequencies to be of use in distinguishing populations. Significant differences between regions were detected using a log-likelihood test for heterogeneity. Variation in allelic frequencies within each region was minimal. Cluster analysis of genetic similarities between sample pairs revealed two major clusters roughly corresponding to the Bering Sea and the Gulf of Alaska. Our biochemical genetic data suggest that there are no distinct stocks within the southeastern Bering Sea nor within the Gulf of Alaska, but that there are minor genetic differences between fish in these two regions.Key words: Walleye pollock, Theragra chalcogramma; biochemical genetic variation, population structure, eastern Bering Sea, Gulf of Alaska, starch gel electrophoresis