effect of feeding on oxygen consumption and ammonia excretion of juvenile tench Tinca tinca (L.) reared in a water recirculating system

The effect of feeding frequency (one, three, and continuous feeding), feed ration (0.2, 0.5, 0.8% of total fish biomass), and feeding per se on the oxygen consumption (OC, mg O₂ kg-¹ h-¹) and ammonia excretion (AE, mg TAN kg-¹ h-¹) of juvenile tench (body weight 15-19 g) and variations in these parameters in daily cycles were examined. Fish metabolism was studied in a recirculating system (rearing tanks of 0.2 m³, water temperature 23 °C). It was found that oxygen consumption and ammonia excretion depended significantly on feed ration. An increase of feed ration from 0.2 to 0.8% of fish biomass caused an increase of OC and AE from 126.80 mg O₂ kg-¹ h-¹ and 1.95 mg TAN kg-¹ h-¹ to 187.35 mg O₂ kg-¹ h-¹ and 8.80 mg TAN kg-¹ h-¹ (p