Dynamics of chemical composition of the Black Sea gray mullet <Emphasis Type="Italic">Mugil cephalus</Emphasis> in the period of early ontogenesis and its dependence on temperature and salinity

Results of experiments on the study of the effect of temperature and salinity on dynamics of the chemical composition of gray mullet Mugil cephalus in the embryonic-larval period of development are presented. During the period of endogenous feeding (from the beginning of egg cleavage to transition of larvae to active feeding), lipids are spent with a greater rate than protein. After transition of larvae to exogenous feeding, an increase in the absolute concentration of proteins compared to lipids begins earlier and proceeds more intensively. The stage of irreversible starvation in larvae of gray mullet starts at a loss of 39–44% of protein and of the same amount of lipids of their initial content at the moment of hatching. Minimal protein losses over the period of embryonic development of gray mullet, as well as of protein and lipids towards the moment of termination of resorption of yolk sac, are observed in the range of temperatures of 21–25°C. Under conditions of low salinity (13–15‰) in the process of resorption of the yolk sac, lipids are spent more economically than at a higher salinity (17–19‰) at the expense of an increase in protein losses. Thus, a decrease in specific weight promoting the retention of buoyancy of larvae in water of low density is achieved.