The effect of feed supply rate on growth of juvenile perch (Perca fluviatilis)

This study investigates the effect of the feed supply rate within a meal on growth of juvenile perch (Perca fluviatilis). Groups of PIT-tagged, feed-trained juvenile perch (12 g) were held in 100-L tanks at 18 degreesC, under a 24L:0D photoperiod and fed five meals per day in excess. Feed was applied at rates of 1.2 (Low), 4.2 (Medium) and 14.3 (High) pellets fish(-1) min(-1) during two periods, each of 50 days. Cumulative meal-time per day ranged from 10 to 225 min. Specific growth rates (SGR) in the two periods were positively correlated, indicating a consistent individual growth performance. There was growth dimorphism between the sexes. Females grew about 20% faster than males, resulting in final mean weights of approximate to 87 and 58 g respectively. Autopsy revealed differences in sex ratios between treatments and the effect of feeding rate was analysed according to sex. There was a tendency for fish fed at the lowest rate to have a higher SGR than fish in other treatments, both for females (L = 1.98 +/- 0.0, M = 1.84 +/- 0.08, H = 1.88 +/- 0.19% bw day(-1)) and males (L = 1.68 +/- 0.01, M = 1.55 +/- 0.16, H = 1.57 +/- 0.02% bw day(-1)). Fish fed at the lowest rate also tended to have the lowest feed conversion ratio (L = 0.88 +/- 0.05, M = 1.02 +/- 0.11, H = 1.04 +/- 0.10) but the effects were not significant. These results suggest that juvenile perch can feed efficiently under a range of conditions.