Interannual dynamics of size, age composition and parameters of growth for japanese sardine <i>Sardinops melanostictus</i> in periods of its high abundance in the North-West Pacific

Abstract

Interannual dynamics of size composition, age structure, and growth parameters are considered for japanese sardine Sardinops melanostictus in context of its recent and previous blooms and mass migrations to the Pacific waters at Kuril Islands and to the northern Japan Sea. Before the post-bloom catastrophic decline in the 1990s, in conditions of the highest density of the sardine population, small-sized fish with relatively slow growth rate became dominant, distinguished by lowered reproductive potential because of low population fecundity and reproduction rate. In the new, modern bloom of sardine population, two modal groups are observed in the year-classes size composition, in particular in the Japan Sea, with different exterior and biological parameters. There is assumed that they correspond with two morphological types, which alter each other at different stages of the demographic cycle, that determines total abundance of sardine population in the North-West Pacific and its long-term dynamics.