К изучению биологии судака (Sander lucioperca) в изменившихся экологических условиях северной части Аграханского залива Каспийского моря

Abstract

The northern part of the Agrakhan Bay, which used to play a peculiar role of a receiving reservoir for migratory and semi-migratory fish migrating to spawn and wintering, and served as a kind of nursery for the development of larvae of their young, rolling here from spawning-growing reservoirs and the lower reaches of the Terek, in recent years, as a result of a critical decrease in river flow and a drop in the level of the Caspian. It has ceased to perform its main functions to increase fish stocks in the Terek-Caspian fisheries area. Among semi-migratory fish, the walleye is of particularly important fishery importance, as the largest and most valuable representative of the Percidae family in commercial and food relations. It was found that the structure of the walleye population in the northern part of the Agrakhan Bay in the last 2018-2021 turned out to be the most susceptible to unaccounted withdrawal, and its number is in a depressed state. It was revealed that the current level of reproduction of walleye in the bay turned out to be relatively lower as a result of intensive overgrowth and weak water availability. Histological examination of the gonads showed that the ovaries of walleye in the IV stage of maturity are for five months, from the end of October to April. It is established that the growth rate at different stages of development depends on environmental factors (hydro-hydrochemical and temperature regime of reservoirs, regime, salt balance, etc.) as well as their food supply.