The article presents the research materials of pike perch r. Volga and the Kuibyshev reservoir and noted the changes that have occurred in its population. Prior to the creation of the reservoir in the conditions of the Middle Volga, male zander matured at the age of 5–6 years, females at 6–7 years. In the Kuibyshev reservoir, pike perch becomes sexually mature at the age of 4–5 years, and a small part of it matures at the age of three. In the reservoir, due to ecological plasticity and the ability to lay eggs in a wide temperature range, regardless of the level regime of the reservoir and the spawning substrate, a gradual increase in its biological indicators, abundance and reserves began to be noted. Improving the feeding conditions of zander in the reservoir contributed to earlier puberty, an increase in the absolute fecundity of fish and its abundance in the reservoir. This contributed to an increase in zander catches since 1974, which in 1985 reached a maximum of 517 tons (9,2% of the total fish catch in the reservoir). Sufficiently high catches of zander over the past 10–15 years indicate the stability of its stocks in the Kuibyshev reservoir, which currently tend to increase. The multi-age sizeweight composition of zander in the Kuibyshev reservoir is represented by both young and older individuals, and confirms that the population is in good condition.
The article analyzes the data of long-term studies of sterlet growth in the Kuibyshev Reservoir (watershed of the Volga River) conducted by researchers of the Tatar branch of the
All-Russian Research Institute of Fisheries and Oceanography. Significant variations in sterlet length were found not only from year to year, but also in different parts of the reservoir. There have been stated the changes in sterlet population. In recent years, the reservoir has seen an improvement in the growth of sterlet yearlings in comparison with that of fish in the Volga river and in the first years of the reservoir's existence, and a decrease in the growth rate and size of older individuals. It has been found that starlet species in Kama Reaches grow better than in other parts of the reservoir. Fish with fast linear growth is found to increase its percentage, while the part of slow-growing fish decreases.
The article presents a review of the main commercial fish stocks of the Kuibyshev Reservoir based on the long-term research data (2000–2019). The Kuibyshev Reservoir is the leading fishery reservoir in the Republic of Tatarstan, Mari El, Chuvashia, Ulyanovsk and Samara Re-gions. There have been given the data of regular observing species, sex, size-weight and age composition of fish, their reproduction efficiency, distribution, abundance and reproduction of aquatic biological resources, their habitat, as well as control over their fishing and conservation. The analysis of the influence of environmental factors (level and temperature regimes) and fishing on the fish stocks formation is presented. Based on the presented materials, there have been shown the data about the stocks of the main commercial fish species of the Kuibyshev Reservoir (bream, zander, pike, carp, catfish, sterlet) and of the small-sized ordinary fish stocks, the optimal development of which will bring the catches up to 10 thousand tons and more. It has been inferred that for rational fishing in the reservoir, it is necessary to develop a strategy for the integrated effective development of biological resources of the reservoir on an ecosystem basis for better use of the bioproduction capabilities of its biological resources.
The features of the industrial reproduction of sterlet in the Middle Volga region are considered. The necessity of further increasing the volume of production and release of juvenile sterlet to the Kuibyshev reservoir is shown. An increase in the relevance of research works in the field of sturgeon ichthyopathology has been noted. The importance of carrying out ichthyopathological observations is shown both for ensuring the stability and efficiency of production, and for preserving the natural population of sterlet in the Kuibyshev reservoir. The article considers the relative novelty of ichthyopathology as a science and the discrepancy between normative legal acts regulating ichthyopathological observations in Russia. The industrialization of aquaculture forms is shown. The emergence of new sturgeon diseases specific to high-intensity fish farming was noted. The results of experiments on the use of inorganic drugs for the treatment of sturgeon nutritional diseases are presented.
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