ALBERT

Notes: The olive flounder Paralichthys olivaceus is one of the most commercially important fish species in Korea. In order to formulate better diets for cultured olive flounder we evaluated the optimum dietary protein requirements for larval, fry and juvenile olive flounder, and the optimum dietary protein to energy ratio for juvenile olive flounder. Results of four separate experiments suggested that the optimum dietary protein requirements were 60% in larvae (0.3 g), 46.4–51.2% in 4.1-g juvenile, and 40–44% in 13.3 g growing olive flounder. The optimum dietary protein to energy ratio based on weight gain, feed efficiency, specific growth rate, and protein retention efficiency was 27–28 mg protein/kJ 2 energy (35 and 45% CP for diets containing 12.5 and 16.7 kJ energylg diet, respectively).

Notes: Two feeding trials (experiments 1 and 2) were conducted to determine the combined effect of dietary energy levels (low energy, LE and high energy, HE) and number of daily meals (one meal with the entire daily amount, two meals with half of the daily amount, and three meals with one-third of the daily amount) on the growth and body composition of Nile tilapia Oreochromis niloticus in a recirculating system at different water temperatures, representing winter and summer seasons. In experiment 1 (winter), weight gain and specific growth rate (SGR) were significantly (P 〈 0.05) affected by dietary energy levels, but not by number of meals. Weight gain and SGR for fish fed the LE diet one daily meal were significantly (P 〈 0.05) higher than for fish fed the HE diet in one daily meal. Feed efficiency ratio (FER) and energy efficiency ratio (EER) were significantly (P 〈 0.05) affected by dietary energy levels, but not by number of meals. Protein efficiency ratio (PER) was not significantly (P 〉 0.05) affected by either dietary energy levels or number of meals. However, protein retention was significantly (P 〈 0.05) affected by both dietary energy levels and number of meals. The chemical composition (moisture, protein, lipid, and ash) of fish muscle was not significantly (P 〉 0.05) affected by either dietary energy levels or number of meals. However, visceral fat content was significantly (P 〈 0.05) affected by dietary energy levels, but not by number of meals. In experiment 2 (summer), weight gain and SGR were significantly (P 〈 0.05) affected by number of meals, but not by dietary energy levels. Weight gain and SGR for fish fed the LE and HE diets in two daily meals were significantly (P 〈 0.05) higher than those fed one daily meal. FER and PER were significantly (P 〈 0.05) affected by number of meals, but not by dietary energy levels. The highest FER and PER were observed in fish fed two daily meals. EER was significantly (P 〈 0.05) affected by both dietary energy levels and number of meals. Moisture and protein content of the whole fish were not significantly (P 〉 0.05) affected by either dietary energy levels or number of meals. Lipid content was significantly (P 〈 0.05) affected by dietary energy levels, but not by number of meals. Based on the results of these experiments, Nile tilapia should not be fed high-energy diets to improve fish performance even under a limited feed allowance during winter or summer. Fish grew rapidly when fed two daily meals during summer, but number of meals had no effect on fish performance during winter.