Effects of Feeding Frequency and Ration Level on Growth Performance and Non-Specific Immunity of Juvenile Turbot (Scophthalmus maximus) at Different Growth Stages

Four growth trials were carried out to optimize a feeding regime for turbot in industrial aquaculture systems at 15±0.5°C. Six ration levels (50%, 60%, 70%, 80%, 90%, and 100%) of satiation were tested in trial I and five ration levels (60%, 70%, 80%, 90% and 100%) of satiation were tested in trial III. For optimal feeding frequency, turbot were fed to satiation for 1 meal/day, 2 meals/day, 3 meals/day in trial II, and 1 meal every other day, 1 meal/day, and 2 meals/day in trial IV. The average initial body weight of fish was 28.90±0.07g for trials I & II, and 181.75±1.05g for trials III & IV. Growth performance generally decreased and feed utilization increased with decreasing ration levels, while no significant differences were observed with small sized turbot fed to 80%, 90%, 100% levels of satiation, and with large sized turbot fed to 90% & 100% levels of satiation. There was no increase in size heterogeneity with decreasing ration levels. Ration levels significantly influenced water quality. There were no significant differences in growth and feed efficiency among turbot fed with different feeding frequencies. Feeding small size turbot once a day and large size turbot once every other day at a ration level of 80% satiation is suggested for better feed utilization and less waste output.