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This study was carried out to investigate the influences of feeding frequency of extruded pellet and moist pellet on growth and body composition of juvenile flounder (initial mean weight 6.3 g) in suboptimal water temperatures. A 2 (diets: extruded pellet and moist pellet) ¥ 2 (feeding frequencies: two and three times daily) ¥ 2 (water temperatures: 12 and 17°C) factorial design with three replications was used. After 60 days of feeding, the feeding frequency did not significantly affect growth performance of fish. Weight gain, daily feed intake, feed efficiency and protein efficiency ratio were significantly (P < 0.05) higher for fish reared at the higher water temperature. At the same water temperature, weight gain, feed efficiency, and protein efficiency ratio were significantly (P < 0.05) higher for fish fed the extruded pellet than moist pellet. The results of this study indicate that feeding frequency of two times daily is sufficient for optimal growth of juvenile flounder when reared in suboptimal water temperatures, and an increase in water temperature from 12 to 17°C improved growth and feed efficiency.KEY WORDS: extruded pellet, feeding frequency, Japanese flounder, moist pellet, water temperature.

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This study is conducted to monitor the morphological developmental features of the egg development, larvae and juvenile of Epinephelus septemfasciatus, the fertilized eggs were gotton using artificial insemination. Matured parents are collected from marine caged fish farms in Geomun-ri, Samsan-myeon, Yeosu-si, Jeollanamdo Korea in June 2012. The fertilized eggs were pelagic eggs containing one oil globule, and measured 0.81~0.89 mm (0.85±0.04 mm, n=50) in diameter. In regard to rearing environment, the water temperature is 21.0~23.0°C and the salinity is 32.0~33.2‰. Hatching was observed from 48 hours after fertilization, the mouth and anus of prelarvae was not opened but had egg yolk at newly hatched. 4 days after hatching, the mouth and anus of postlarvae was opened and began to eat Rotifer and was measured 2.40~2.49 mm (2.45±0.03 mm n=10) in total length. 12 days after hatching, postlarvae was measured 3.77~4.67 mm (4.27±0.33 mm) in total length, its the second pole tide of dorsal fin and the first pole tide of pelvic fin was extended longitudinally. 71 days after hatching, juvenile was measured 40.5~45.4 mm (42.6±2.04 mm) in total length. Seven bands were observed in body, and pole tides of dorsal and pelvic fins were shortened.