Relationship of Size and Mass Characteristics, Indicators of Metabolism and Mercury Concentration in Muscle Tissue of Freshwater Fish from Tropical Vietnam

The main chemical composition and content of mercury in the muscles of freshwater fish species Xenentodon cancila, Notopterus notopterus, Anabas testudineus, Channa striata, Ch. gachua, Clarias batrachus from the rivers of the Cai South Vietnam, and their body sizes, was studied. A trend of more intensive accumulation of mercury, protein and fat in the muscle tissue of females compared to males was revealed. A significant relationship between the content of mercury and body size, as well as the content of mercury and the proportion of protein in the muscles, was not established in most of the studied individuals. Trophic patterns of mercury accumulation in fish muscles were confirmed: its content increased from euryphages to zoophages (facultative predators). An exception is the euryphage Clarias batrachus, which surpassed many facultative predators in mercury content. It is shown that individuals of the same species living in the biotopes of the Kai River with different hydrodynamic and hydrochemical conditions differ in weight, length, content of protein, fat and mercury in muscle tissue.