CHEMICAL COMPOSITION OF FISH MUSCLE OF SMALL RIVERS OF THE YAROSLAVL REGION
The article presents the study results of the chemical composition of Cyprinidae and Percidae skeletal muscles from the Sot', Vopsha and Kast' rivers in the territory of the Yaroslavsky State Nature Reserve. The fish were ascertained for sex, stage of gonad maturity, and age. The total amount of water, dry matter, total lipids, protein, minerals, and nitrogen-free extractives (NFE) were determined in their muscle tissues. The study revealed significant differences in the content of final metabolic products in the muscles of individuals of the same species living in different rivers, which may be connected to the difference in food supply or with characteristics of hydrochemical composition of the reservoirs under study. It has been stated that the chemical composition of muscle tissues depends on the trophic status of aquatic organisms, their sex and age. On average, in the rivers the carpal skeletal muscles were superior to the perch muscular tissue in terms of total lipid content, but inferior to the amount of protein, ash, and NFE. As it was revealed, the female muscles contained more protein and fat, than muscles of males and juveniles. Reduction of dry matter and fat in the muscle tissues of roach, sabrefish and rudd (aged 4 to 5) can be associated with attaining puberty in fish. With age, a decrease of water was observed in Cyprinidae and Percidae muscles due to accumulation of dry matter. With ageing of the studied fish in their muscle tissues was found both the increased and decreased concentration of protein, total lipids, mineral substances and NFE. From the data obtained it can be inferred that the fish population of the rivers flowing through the territory of the Yaroslavsky State Nature Reserve exist in relatively favorable conditions.