Effects of photoperiod on sexual maturation and somatic growth in male Atlantic halibut (Hippoglossus hippoglossus L.)

A major obstacle in modern, intensive aquaculture is the precocious maturat ion of male fish, leading to decreased somatic growth and reduced filet qua lity. Effects of photoperiod on sexual maturation and growth in male Atlant ic halibut were therefore examined. In June 1996, 1300 1 + fish of both sex es were distributed in two indoor tanks supplied with continuous light (LL) or a simulated natural photoperiod (SNP). In December 1996 and June 1997, 200 individuals were exchanged between the tanks creating six experimental groups that were followed until June 1998. LL stimulated growth and acceler ated timing of first maturation by approximately 3 months. LL also appeared to interrupt circannual rhythmicity in sexual maturation. Sexual maturatio n led to reduced growth from 3 months pre-spawning and throughout the spawn ing season. Males that did not mature during the experiment attained the hi ghest final body weight. All males reared on LL from June 1997 reached sexu al maturity the following season. In contrast, only 26% of the males mature d in the group transferred from LL to SNP in June 1997, and this group also had the highest final body weight. The results indicate a possible route f or reducing the problem of precocious maturation in male halibut. (C) 2001 Elsevier Science Inc. All rights reserved.