Physiological research of young Russian sturgeons in modern ecological conditions of the Caspian sea

In the Volga-Caspian fisheries basin, artificial reproduction of sturgeon species is the primary source of replenishing their natural populations. The aim of this study is to conduct physiological research on juvenile Russian sturgeon (Acipenser gueldenstaedtii) in the western part of the Northern Caspian Sea, to establish the features of fish homeostasis. The physiological condition of the specimens was studied using a set of physiological and biochemical parameters. Hematological, biochemical, and morpho-histological parameters were evaluated. In the blood of the fish, the contents of hemoglobin, total protein, glucose, inorganic phosphorus, calcium, creatinine, bilirubin, total lipids, cholesterol, and triglycerides were determined. In the muscle tissue of juvenile Russian sturgeon, the physiological and biochemical indicators studied included the content of the main reserve substances of the body — total lipids and water-soluble protein. Histological methods were used to assess the morpho-functional state of the gills. The variability of physiological and biochemical parameters in juvenile Russian sturgeon was calculated using descriptive statistics based on parametric and non-parametric criteria in the blood and muscles. According to the results of correlation statistical analysis, significant changes were observed in the tissues of the sturgeon juveniles, aimed at providing the body with sources of energy and nutrients used for the functioning of body tissues and serving as reserve stocks, as well as maintaining regulatory mechanisms of metabolism and its changes depending on fluctuating environmental conditions. The morphological examination of the gills revealed vascular disorders, hyperplasia, swelling, and hypertrophy of the respiratory epithelium cells, corresponding to borderline disturbances from mild to moderate damage, which was the organ’s response to external environmental influences.