Interannual Dynamics of the Fish Community’s Integral Characteristics in the Upper Epipelagic Layer of the Pacific Ocean’s Russian Part in June–September 2004–2018

Abstract

Interannual dynamics of the integral characteristics of species structure in the fish community in the Pacific waters off the Kuril Islands in 2004–2018 is described. During that period, the species richness of the fish community was relatively low: 88 fish and fishlike species (annual average 41.06 ± 1.55) of three classes, 20 orders, 47 families, and 75 genera. It was revealed that species diversity and evenness of species structure are decreased because of subtropical species' mass migrations (chub mackerel Scomber japonicus and Japanese sardine Sardinops melanostictus) to the region in the warm season. Changes in the species structure of ichthyocene occurred in 2013–2014. The values of Simpson dominance index (from 4.85 ± 0.44 to 2.97 ± 0.29) and Pielou evenness species structure (from 0.41 ± 0.04 to 0.21 ± 0.03) decreased, while the measure of the concentration of species richness (Margalef index) did not significantly change (3.43 ± 0.14 on average). The hypothesis of the “Japanese sardine’s Epoch” onset is discussed.