Species structure of pelagic ichthyocenes in Russian waters of Far Eastern seas and the Pacific Ocean in 1980–2009

Abstract

Based on the results of pelagic trawl catches in 1980–2009 a general list of ichthyofauna in Russian waters of the Far Eastern seas and the Pacific Ocean comprise 450 species, among which 114 species are identified in the Sea of Japan, 258 species in the Sea of Okhotsk, 170 species in the Bering Sea, and 319 species in the Russian waters of the Pacific Ocean. The species composition of the ichthyofauna was classified according to taxonomical, biotopical, and zoogeographical status of the species. The Simson’ index of dominance varies in a narrow range from 1.58 to 2.66, and the Pielou’s evenness index has low values: 0.17 (Sea of Japan and Sea of Okhotsk), 0.19 (Russian waters of the Pacific Ocean), and 0.27 (Bering Sea). Values of the indexes are confirmed by the conclusion about the dominance of one or two to three species in the surveyed ichthyocenoses made according to the analysis of profiles of rank curves. The highest species diversity (Margalef’s index) is observed in Russian waters of the Pacific Ocean and the lowest diversity is in the Sea of Japan. When comparing qualitative and quantitative composition of ichthyofauna in respect to regions, the lowest index of diversity is found for the fauna in the Sea of Japan. The dynamics of biomass (tons/km2) of all components of pelagic ichthyocenoses is observed according to the periods of years and their species structure is determined. The average long-term density of pelagic fauna concentrations in the area under survey constitute 16.8 tons/km2 and its total resources are 70–80 million tons.