Composition, structure, and dynamics of nekton in the upper epipelagic layer in the Aleutian and Commander Basins of the western Bering Sea in the fall periods of 2002-2013

Abstract

Species composition and abundance of nekton and their interannual variation are considered for the upper epipelagic layer (0-50 m) in the Aleutian and Commander deep-water basins of the western Bering Sea on the data of surveys conducted by Pacific Fish. Res. Center (TINRO) in September-October of 2002-2013. Dominant species were similar for both areas: the most abundant ones were chum salmon Oncorhynchus keta and boreopacific gonate squid Boreoteuthis borealis . Simpson index of domination was higher in the Aleutian Basin and these indices in two areas changed synchronously until 2009 but later they became closer and changed asynchronously. Either chum salmon or the squid dominated usually with some years as exclusion. South-boreal and subtropical species were more abundant in the Commander Basin, in particular in 2006, 2008 and 2012. Year-to-year dynamics of certain species were statistically similar, but its nature was unclear. The total biomass of nekton decreased after the climate regime shift in 2006-2007 from 3241 to 1736 kg/km2 (in 46 %) in the Aleutian Basin and from 2459 to 1976 kg/km2 (in 20 %) in the Commander Basin.

Keywords

• западная часть берингова моря
• верхняя эпипелагиаль
• нектон
• видовая структура
• доминирование
• тихоокеанские лососи
• климатический режимный сдвиг