The main purpose of this study was to understand the effects of temperature on the growth and ammonia-N excretion rate (mg ammonia/100 g body weight/h) of juvenile silver perch Bidyanus bidyanus reared at 18, 23, and 28℃, respectively, for 12 weeks. The average feed intake/fish and percent weight gain were increased with the elevated temperature, and there was significant difference among treatments. Furthermore, feed efficiency and condition factor of the fish reared at 18℃ were remarkedly inferior to those reared at 28℃. Muscle moisture of the fish reared at 28℃ was significantly lower than those of other treatments, however, lipid and ash contents were observed to have the opposite tendency. On the other hand, protein efficiency, percent protein retention and percent lipid retention increased with the elevation of temperature. It indicated that water temperature affects fish on feed intake, and consequently, the metabolism of protein and lipid.
Ten fish (about 11.0 g) of each treatment were starved for 48 h and then fed to satiation for the study of temperatural effect on ammonia-N excretion rate. The result of ammonia-N excretion rates of fish were higher at the higher temperatures and decreased with lower temperatures. Moreover, ammonia-N excretion of all treatments rose to a sharp peak during the first 4 h after feeding. The second peak of excretion for fish reared at 28 and 23℃(or 18℃) was found at 12 and 16 h after feeding, respectively