FISHERIES RESEARCH INSTITUTE,MOA,TAIWAN

The mulloway, Argyrosomus japonicas, is one of the economical aquaculture species in Taiwan. However, poor feeding management of the species has led to a high degree of size heterogeneity, and consequently, cannibalism and highly mortality in the nursery period. Four feeding frequencies of one (A), two (B), three (C) and four (D) times per day were evaluated as treatments in triplicate during a 30-day growing study. Hatchery-produced weaned juveniles (39.91–40.03 mm/ 0.90–0.95 g size) stocked at a rate of 100 per tank were fed a commercial diet containing 44% crude protein and 12% crude fat at 10% of the biomass daily during the experimental period. The survival, cannibalism rate, growth parameters and coefficient of variation (CV) of body weight and total length were tested. The results showed that after 30 days, the survival rates for treatments B, C and D were 82.67 ± 1.20%, 87.67 ± 1.20% and 93.33 ± 1.20%, respectively. All of those rates were significantly (p < 0.05) higher than that for treatment A (66.00 ± 2.52%). The cannibalism rate (6.67 ± 1.20%) for treatment D was significantly (p < 0.05) lower than that for treatment A from 14 to 30 days. The growth parameters, including fish body weight, total length, daily weight gain, percentage weight gain, specific growth rate and feed conversion ratio, for treatments C and D were significantly (p < 0.05) better than those for treatment A. There was no significant (p > 0.05) difference among the four treatments in the condition factors. The CV of body weight and total length were not significantly (p > 0.05) different among the four treatments. Overall, the results from this study indicate that in order to maximize growth performance, the juvenile mulloway should be fed three times per day, whereas in the aim is to maintain a lower cannibalism rate during the entire nursery period, the juvenile should be fed four times per day.