Physiological state of rudd (Scardinius erythrophthalmus L., 1758) of the Volga delta in summer

The rudd (Scardinus erythrophthalmus Linnaeus, 1758) in the Volga Delta is an object of commercial and amateur fishing, but its physiological characteristics have not been established. The aim of the study was to determine the functional state of the Volga Delta rudd in the summer period based on hematological and biochemical blood parameters. The fish were caught in July 2022 in accordance with the rules of amateur fi shing in the Bushma River of the Volga Delta. The study material was 30 rudd individuals (females, gonadosomatic index 3.83±0.54%). The body weight of the examined fi sh was 162.73±12.77 g, absolute body length was 23.20±0.58 cm, and body length to the end of the scale cover was 20.80±0.55 cm. Blood was obtained by puncturing the tail vein. Hemoglobin was determined in the blood using the colorimetric hemiglobin cyanide method. The following was analyzed in the blood serum using the colorimetric method: total protein content — by reaction with biuret reagent; albumin — by reaction with bromcresol green; cholesterol, triglycerides and glucose — enzymatically using the Trinder reaction. As a result of the study, the hemoglobin content of the blood of rudd was established at the level of 59.5±3.1 g/l. Protein metabolites of blood serum were characterized by the content of total protein 28.8±3.9 g/l, albumin 17.1±2.3 g/l. The results of determination of lipid metabolites revealed the content of cholesterol 3.1±0.4 mmol/l, triglycerides 2.66±0.16 mmol/l. The content of glucose in blood serum was 2.83±0.82 mmol/l. Expressed variability of the studied biochemical parameters was found. The results of the study can be used in assessing the state of physiological adaptation of rudd in the Volga delta in summer.