Influence of temperature and rate of feeding on nitrogen metabolism of juvenile bream ( Abramis brama L.)

Abstract

1. 1. Measurements of the rate of nitrogen consumption, ammonia, urea and fecal nitrogen as well as total nitrogen excretion of fry of bream ( Abramis brama) (body weight range: 75–1400 mg wet wt) were made at 15 ± 1 and 20 ± 1° C. 2. 2. Fish were fed once daily on live Zooplankton at 10–15% of their body weight. 3. 3. Neither the temperature nor the ration size influenced the nitrogen consumption offish weighing less than 100 mg. However, food ration affected the nitrogen consumption rate of fish with body weight above 200 mg at 20°C. 4. 4. About 32–78% of the nitrogen consumed in food was excreted and its rate depended mainly on food consumption. 5. 5. Ammonia was the chief end product of protein metabolism; about 52–69% of the total excreted nitrogen was NH 4N. 6. 6. Temperature had no significant influence on its rate but food ration affected the ammonia excretion of fish fry. 7. 7. Urea made up 14–21% of the excreted nitrogen, depending slightly on temperature. 8. 8. The nitrogen content of feces was high and had a range between 20 and 23%.