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

Abstract

The effect of thermal history (11 degrees C and 14 degrees C) on grow th of juvenile halibut, Hippoglossus hippoglossus (L.,) (initial mea n weight 140 g, n = 254), was stud ied, Fish were divided into four g roups, two groups remaining at constant temperature (C11, C 14), and fish in the other groups being transferred from either 11 degrees C t o 14degrees C (F11:14) or from 14 degrees C to 11 degre es C (F14:ll) . Twenty fish in each tank were tagged (PIT) at the start of the expe riment. The final mean weights were significantl y higher in F14:11 ( 384 g) than in F11:14 (308 g) and C14 (317 g). Further, F14:11 had si gnificantly higher length growth rate (SLGR) than both F11:14 and C14 . No significant differences betwe en the experimental groups within each temperature (F14:11 vs, C1 1, and F11:14 vs. C14) were, however, found. Growth rate (SGR) de clined rapidly with increasing size (fro m 1.4-1.8% day( -1) to 0.4-0.8 % day(-1)). It is concluded that the o ptimal temperature for grow th of juvenile halibut declines with incr easing size. T hus, as ha libut grow larger, the temperature should b e reduced to take adva ntage of this change in optimal temperature fo r growth.