Food base of nekton in deep-sea areas of the western Bering Sea: dynamics, current state and its consumption by pacific salmon

Abstract

Long-term dynamics of the food base for nekton in the deep-sea waters of the western Bering Sea are analyzed on the data of ecosystem surveys in 1986–2022. The main patterns of species composition and structure are determined for the main taxonomic groups of zooplankton and their production is evaluated. These features are influenced by climateoceanographic and biocenotic factors, with priority of the climate-oceanographic ones, whereas the biocenotic factors are conditioned by them. As an example of biocenotic impact, the effect of chaetognats on copepods is considered. Trophic characteristics of the most abundant species of pacific salmon (chum salmon Oncorhynchus keta and pink salmon O. gorbuscha) and their consumption of zooplankton production were estimated for 2020–2022. Comparing productivity and grazing of the main zooplankton groups, there is concluded that pacific salmon consume a small portion from seasonal production of their prey, therefore, food competition between the species of pacific salmon is absent in the deep-sea waters.