Growth of juvenile halibut, Hippoglossus hippoglossus (L.), under a constant and switched temperature regime

The effect of thermal history (11 degrees C and 14 degrees C) on growth of juvenile halibut, Hippoglossus hippoglossus (L.,) (initial mean weight 140 g, n = 254), was studied, Fish were divided into four groups, two groups remaining at constant temperature (C11, C14), and fish in the other groups being transferred from either 11 degrees C to 14 degrees C (F11:14) or from 14 degrees C to 11 degrees C (F14:ll). Twenty fish in each tank were tagged (PIT) at the start of the experiment. The final mean weights were significantly higher in F14:11 (384 g) than in F11:14 (308 g) and C14 (317 g). Further, F14:11 had significantly higher length growth rate (SLGR) than both F11:14 and C14. No significant differences between the experimental groups within each temperature (F14:11 vs, C11, and F11:14 vs. C14) were, however, found. Growth rate (SGR) declined rapidly with increasing size (from 1.4-1.8% day(-1) to 0.4-0.8% day(-1)). It is concluded that the optimal temperature for growth of juvenile halibut declines with increasing size. Thus, as halibut grow larger, the temperature should be reduced to take advantage of this change in optimal temperature for growth.