FISHERIES RESEARCH INSTITUTE,MOA,TAIWAN

Rearing experiments were conducted for 8 weeks to investigate the effect of temperature on the growth and ammonia-N excretion rate (mg ammonia/100 g body weight/h) of Amur sturgeon, Acipenser schrenckii, at 3 temperature treatments (18, 23, and 28 °C) with 2 replicates per treatment. Twenty-five juveniles per treatment with an average length of 37.4 cm and an average weight of 154.8 g were stocked in each of 6 thermo-regulated recirculating tanks (2.5 ton/tank). Fish were fed every 2 h with an auto-feeder at a 3.5% daily ration for the first 6-week period and 3% for the last 2 weeks. Average feed intake/fish, weight gain, and feed efficiency of fish reared at 23 °C were significantly higher than those at 18 and 28 °C. After termination of the rearing trial, 3 fish from each treatment group were starved for 48 h and then fed to satiation to determine the ammonia-N excretion rate. The results indicated that the excretion rate was much higher at 28 °C than at the lower temperatures. Moreover, ammonia-N excretion of fish reared at 23 and 28 °C rose to a sharp peak at 4 h after feeding, whereas the peak occurred at 8 h at 18 °C. This showed that temperature greatly influenced the ammonia-N excretion rate of Amur sturgeon.