The main factor influencing the success of the reproduction of limnophilous fish is the height of the level and the duration of the spring flood with uniform water heating. Given the impossibility of regulating the operation of HPSs in accordance with fishery recommendations, due to the isadvantage of these rhythms for the shareholders of the energy sector, the search for environmental factors that can be influenced by the forces of the agricultural sector seems to be extremely relevant. The reproduction of fish was studied in the area of the middle zone of the Volgograd reservoir near the villages Akhmat and Zolotoye, Krasnoarmeysk district, Saratov region, from 2017 to 2021. In total, reproduction of 19 fish species was recorded in the studied water areas. In 2017, a high yield of juvenile fish was noted in the considered section of the reservoir, in 2018 there was an average yield, in subsequent years yield was very low. The production characteristics of spawning and feeding grounds of the corresponding area were studied. The dependence of the efficiency of fish reproduction on the productivity of shallow waters is shown. The relationship between the deficit of net primary production, the level and temperature regimes of the Volgograd reservoir and the damage caused to fish reproduction by the deficit of net primary production is mathematically described for the study area of the reservoir over a five-year period. One of the reasons for the deficit of net primary production is considered (expressed in mg O2/l): outbreaks of blue-green algae blooms in July-August, which also leads to death phenomena.

One of the main factors influencing the efficiency of reproduction of limnophilic fish is the height of water level and the duration of spring flood with uniform water heating. Work was carried out to assess the natural reproduction of fish in the area of the middle zone of the Volgograd reservoir, near the villages Akhmat and Zolotoye, Krasnoarmeysk district, Saratov region, in 2022. In total, juveniles of 11 fish species were caught in the surveyed areas in 2022. There is a significant decrease in species diversity compared to previous years. Due to the unfavorable level regime during the spawning period, very unfavorable conditions for the reproduction of fish have developed in 2022. For the first time in 6 years of research in the waters under consideration, it was possible to record the reproduction of catfish (Silurus glanis) and carp (Cyprinus carpio). In 2022, in the area near Akhmat village, an anomaly was observed: underyearlings of bleak (Alburnus alburnus), which usually dominates catches, and perch (Perca fluviatilis), which is also common in this area, were absent in the catches (despite the fact that individuals of these fish of older ages were encountered). In the water area near Zolotoye village still recorded the reproduction of Black Sea-Caspian sprat (Clupeonella cultriventris), the early larvae of which are common there in the catches and are not found in the water area near Akhmat village. In the water area near Zolotoye village underyearlings of asp (Aspius aspius) are still common, and they dominate the catches in 2022. In the water area near Akhmat village, the catches of 2022 are dominated by crucian carp (Carassius gibelio).

The nutrition of sunbleak (Leucaspius delineatus) from the pond of Noginsk district of Moscow region in February 2023, owned by GNP “Yakor”, was studied. The aim of the study was to investigate the nutrition of sunbleak. To achieve this aim, the following tasks were performed: the age of the caught fish, their average length and weight were determined, the quantitative and qualitative composition of zooplankton in the reservoir was studied, the food boluses of the fish were considered in order to establish the frequency of occurrence of food objects in them, the intestinal filling index and the selection index. The study of the sunbleak nutrition seems relevant for establishing links in the ecosystem of a fishery reservoir, with the aim of further optimal selection of fish multiculture, based on the analysis of the state of the natural food supply. As part of the zooplankton community of the reservoir, 11 taxa were identified: 4 species of rotifers, 4 species of branchous and 3 taxa of copepods. In the course of the study, it was found that the sunbleak from the reservoir in question fed on almost all the species encountered except rotifers. With age, the fullness of the fish intestines decreased. The species composition of the consumed crustaceans differed depending on the age of the fish. Younger fish preferred the smaller size species of crustaceans, older fish preferred larger size and more nutritious species of crustaceans. Crustaceans of the Daphnia genus turned out to be the most preferable food for the sunbleak of all ages, and with age, the fish more and more preferred this food object. The most abundant crustaceans of the Bosmina genus in the water body were avoided by the fish, even the underyearlings, the only age category of the sunbleak that fed on these organisms.

No abstract