Optimum daily ration for Eurasian perch Perca fluviatilis L. reared at its optimum growing temperature

Abstract

Four feeding experiments were conducted to estimate the optimal daily food ration of Eurasian perch at different stages of its development under optimum rearing temperature (23 °C). Mean initial weights of 0.22-, 0.73-, 1.56- and 18.9-g fish, previously habituated to a dry diet, were used in experiments lasting between 14 and 30 days, depending on initial body weight. Daily feeding levels ranged from 2% to 20% of biomass in 0.22-g fish, from 1% to 8% in 0.73-g fish, from 1% to 10% of biomass in 1.56-g fish and from 0.3% to 3% of biomass for 18.9-g fish. Feeding levels significantly affected survival of perch, except in experiment 4 with large juveniles (18.9). In experiments 2 and 3 (with 0.73- and 1.56-g fish, respectively), cannibalism was significantly higher at the lowest feeding level (1% biomass day −1), while starvation seemed to be the major cause of death in experiment 1 with 0.22-g fish. Values of specific growth rate (SGR) plotted against daily food ration allowed the maintenance, optimum and maximum feeding levels to be determined, according to the Brett and Grove's model. Optimum feeding level for Eurasian perch decreased from 7.4% to 5.1%, 4.5% and 2.2% biomass day −1 for fish of 0.22, 0.73, 1.56 and 18.9 g initial body weight, respectively.