Influence of feeding level on growth, intraspecific weight variability and sexual growth dimorphism of Eurasian perch Perca fluviatilis L. reared in a recirculation system

Abstract

The influence of the feeding level (FL) on growth and sexual growth dimorphism, was investigated in juvenile Eurasian perch (10 g initial body weight) reared in a recirculation system over 84 days. Fish were divided into groups of 105 individuals and fed three feeding levels: 1, 2 and 3% of the fish biomass (3 replicates/FL). Survival was not significantly ( P > 0.05) different among the three FLs. Feeding levels significantly affected ( P < 0.05) growth performance of perch; mean body weight at the end of the experiment was 22.3 ± 0.5 g, 47.9 ± 2.4 g and 52.7 ± 1.7 g, at 1, 2 and 3% FL, respectively. Significant differences were observed among the specific growth rate of fish fed at 1, 2 and 3% FL. Similar feed conversion ratios (FCR) were obtained for fish fed at 1 and 2% FL (1.08 and 1.01, respectively) which were significantly lower ( P < 0.05) than that obtained for the groups fed at 3% FL (1.53). Weight heterogeneity was significantly affected by feeding level. During the 84 days, the coefficient of variation (CV) for weight decreased from 45–50% to 30–35% when perch received the 1 or 2% FL. On the other hand, CV remained constant at the 3% FL. The final autopsy of perch revealed that a 3% FL favoured a sexual growth dimorphism. While no significant weight differences between male and female perch were recorded in fish fed at 1 or 2% FL, the 3% FL females were larger than their male homologues (59.2 ± 1.2 vs. 47.6 ± 3.1, P < 0.01). These data suggest that feeding management could be used to regulate weight heterogeneity and sexual growth dimorphism in perch culture.