ЧИСЛЕННОСТЬ И РАСПРЕДЕЛЕНИЕ СЕГОЛЕТОК ВОБЛЫ, ЛЕЩА И СУДАКА В ЗАПАДНОЙ ЧАСТИ СЕВЕРНОГО КАСПИЯ В СОВРЕМЕННЫХ УСЛОВИЯХ МНОГОВОДНОГО И МАЛОВОДНОГО СТОКА РЕКИ ВОЛГИ

Abstract

The article presents the comparative analysis of quantity and the distribution of Caspian roach, bream and pike perch underyearlings in western part of the northern Caspian in the current context of the Volga river high water and low-water run-off in 2013-2016. It has been shown that, depending on conditions of each year, the quantity of the three species underyearlings varies too much. The biggest number of Caspian roach and bream in the period under review was observed in 2013 and 2016, and the biggest pike perch quantity - in 2016. In spite of certain variability, the quantity of Caspian roach and pike perch underyearlings stays low today. Bream quantity in some years increased up to the level of middle yielding generations. In spite of low quantity, Caspian roach underyearlings almost completely developed feeding territories of western part of the north Caspian in both high water and in low-water years. The foraging area of bream and especially of pike perch underyearlings is smaller than Caspian roach one. They spread to the maximum upon the water area of the Caspian Sea in 2016, that year was the most favorable in salinity for generative freshwater fish for the last few years. Caspian roach underyearlings generally gained weight in waters with salinity over 8‰, bream - in desalinated areas with salinity up to 5‰. Pike perch underyearlings stayed in desalinated areas during the high water years; they were found across the studied spectrum with low (0-5‰), high (>10‰) and moderate water salinity (5-8‰) during the low-water years.