Population Ecology and Structural Dynamics of Walleye Pollock (Theragra chalcogramma)

Abstract

In this paper, walleye pollock (Theragra chalcogramma) is characterized as a generalist species, occupying a broad niche and inhabiting a wide geographic range. Pollock’s local abundance is usually high, dominating the fish biomass in many regional ecosystems. Thus, it appears to be an adaptable species capable of colonizing marginal habitats. The fields of macroecology, metapopulation dynamics, and genetic population structure are briefly reviewed and information on pollock is summarized within the framework of these concepts. Pollock show a pattern of apparent stock structure that has not always been indicated by genetic differences. Phenotypic differences between stocks, elemental composition of otoliths, and parasite studies indicate restricted mixing of adults. There are genetic differences between broad regions, but differences between adjacent stocks, especially within the eastern Bering Sea, are currently unresolved. The potential for gene flow mediated by larval drift is high between adjacent stocks. A generalized population structure for walleye pollock is proposed. The macro-population of walleye pollock is made of several major populations (such as the eastern Bering Sea and Sea of Okhotsk populations)