Applications of the Stock Concept to Fish Populations in the USSR

Abstract

Genetic studies of several species of marine fish conducted for over 20 years are reviewed for their application to the problem of intraspecific differentiation of fish. Cyto-physiological, biochemical, and immunological methods were used. By each of these, two sizes of Black Sea horse mackerel (Trachurus mediterraneus) were shown to be sibling species and not local stocks. Similarly, North Atlantic redfish Sebastes marinus and S. mentella were found to be separate species, in agreement with known morphological and ecological differences. In Pacific salmon, genetic markers were used to distinguish planted chums from native stocks, and indicated that such populations are maximally adapted to their historic environment. Stock differences are less apparent in pinks, but are sufficient to suggest subpopulation structure. Genetic differences are found in adjacent generations in odd and even years. Subdivision was most pronounced in sockeye salmon (Oncorhynchus nerka). Spring sockeye spawning in streams were more subject to selection pressure than were summer stocks spawning in lakes. In Atlantic salmon (Salmo salar), spawning in rivers of northern European USSR, the majority showed genetic subdivision during the spawning run. North Sea herring (Clupea harengus) tested by hemagglutination reactions showed differences that coincided with ecological subdivision at spawning, for winter–spring oceanic, summer–autumn marine, and spring–summer coastal herring. Electrophoretic determinations supported these differences. In European anchovies (Engraulis encrasicholus), stocks were differentiated by blood groups, even in the absence of spatial isolation. All of these findings indicate that elementary fish populations play an important role in differentiation and integration of the species gene pool. Efficient management of fish stocks is based on preserving the hereditary heterogeneity of their populations.Key words: genetic markers, stock differences, immunological, biochemical, physiological, intraspecific differentiation