Effect of various feed rations on the growth parameters of European perch, Perca fluviatilis (L.), reared in a recirculating aquaculture system

The aim of the study was to determine the influence various feed rations had on the growth, feed conversion, and variation in body weight of European perch, Perca fluvatilis (L.), reared in a recirculating system. The three feed rations applied were: 0.5% (group F 0.5), 0.8% (group F 0.8), and 1.1% (group F 1.1) of the fish biomass. The fish in each group were marked individually and assigned to size classes: small (class S - 58.7 g), medium (class M - 77.3 g), and large (class L - 106.6 g). The stock in each tank with a volume of 1m3 was 21 individuals (three replicates for each group). The experiment was 56 days long. The highest mean body weight after eight weeks of rearing was determined in group F 1.1. The final body weight of this group was 7.5% higher than in group F 0.8 and 21.5% higher than in group F 0.5 (P < 0.05). The daily growth rate (DGR) of the fish fed the largest feed ration (group F 1.1) was 2.5 times higher than in the group fed the smallest feed ration (group F 0.5). The specific growth rate (SGR) ranged from 0.26% day^-1 (group F 0.5) to 0.70% in group F 1.1, and the differences among the groups were statistically significant. The experimental results showed that the best perch rearing results were obtained using daily feed rations of 1.1% of fish biomass. Under such conditions, perch obtained larger relative and absolute daily specific growth rates.