Current biological characteristics of Abramis brama in the Kuibyshev reservoir

Abstract

The article presents materials of long-term studies of bream from the Volga river and the Kuibyshev reservoir, and notes the changes that have occurred in its population. Before the creation of the Kuibyshev reservoir, in the Volga river sexual maturity in females of bream occurred at the age of 6–9 years, in males a year earlier. In the Kuibyshev reservoir, males began to mature at the age of 4–5 years, females — at the age of 5–6 years, and mass maturation began to be observed at the age of 9–11 years. The changes that took place both in the ecosystem of the reservoir and in the conditions of fish habitat contributed to a radical restructuring of the structure of the bream herd, which adapted to reproduction under significant fluctuations in the level regime of the reservoir. Its former, rather homogeneous local populations differentiated and began to multiply at different times. In shallow waters, it began to multiply at an earlier date, because the water here warms up faster, and in deeper places a little later, usually with repeated floods during a period of high water levels. At present, the rejuvenation of the commercial bream stock in the reservoir has been noted. In 1987, the catches included fish aged from 6+ to 20+ — 21+ years, today the age range of the reservoir bream is made up of fish 2+ — 17+ years old. This is due to the fact that over the past 20 years, in the Kuibyshev reservoir and in many water bodies of Russia, there has been an orientation of the fishery towards valuable species of fish, and to a greater extent large individuals with the greatest commercial benefit are caught.