Interannual variability of the functional state of bream (Abramis brama, L.) of the delta Volga in the pre-spawning period

Bream is an important fishing object of the Volga-Caspian region. Its catches here in the middle of the last century reached 60 thousand tons, while currently they do not exceed 14 thousand tons. The study of the functional state of bream in the pre-spawning period makes it possible to determine the success of spawning, predict the survival of offspring at the early stages of ontogenesis. During the spawning periods (2007–2017 and 2021), the functional state of female and male bream caught in the waters of the delta Volga was studied. To assess the physiological state, the following biochemical parameters of blood were analyzed: the amount of hemoglobin, total serum protein, β-lipoproteins, cholesterol, total lipids, triglycerides, inorganic phosphorus, glucose, activity of alkaline phosphatase and aspartate aminotransferase, generally accepted methods of hematological and biochemical studies of blood and blood serum were used. The work used generally accepted methods of hematological and biochemical studies of blood and blood serum. As a result, there were statistically significant differences in the values of such indicators as the level of hemoglobin in the blood, cholesterol and β-lipoproteins cholesterol, glucose between females and males were noted. Significant interannual differences in the values of the studied indicators were revealed. The flow regime and the volume of spring flood had a decisive influence on the functional state of bream in the prespawning period. Deviations from the values of these indicators from the limits of reference values characteristic of fish and bream, in particular, taken from literary sources, were usually observed in low-water years (hemoglobin, β-lipoproteins, total lipids). The average level of correlation (r = 0.50) between the value of total whey protein and cholesterol was established in bream, which indicates a close relationship between protein and lipid metabolism. Thus, the physiological state of the Lower Volga bream in the pre-spawning period of high-water years can be characterized as relatively favorable.