Effects of temperature on nitrogenous excretion of Japanese flounder [Paralichthys olivaceus]

Effects of temperature on nitrogenous excretion of Japanese flounder (Paralichthys olivaceus) were examined at 16, 20, and 25 degree C with fish of 1.3 to 9.7 g (juvenile), 57.2 to 100.6 g (young), and 265.9 to 535.0 g (immature) in body weight. The ammonia excretion rate of the starved flounder increased with an increase of temperature at all developmental stages. Temperature did not affect the urea excretion rate of juvenile and young fish, however, the rate of immature fish showed a similar trend to the ammonia excretion. Diurnal patterns of ammonia and urea excretion of juvenile fish after feeding were similar to each other among temperatures tested. Daily rates of ammonia, urea, and feces nitrogen excretion of the fed fish tended to increase with an increase of temperature, as well as the proportions of these substances to the consumed nitrogen.