Egg and Larval Development of a New Hybrid Orange-Spotted Grouper Epinephelus coioides×Giant Grouper E. lanceolatus

To establish a seed production technique for a new hybrid orange-spotted grouper Epinephelus coioides x giant grouper E. lanceolatus, the egg and larval development were observed. Newly ovulated eggs from a female E. coioides of 7.5 kg in body weight were measured 806+-20 micro m (mean+-SD) in diameter and weighed 3,505 eggs/g. After fertilization with sperm obtained from a male E. lanceolatus, the diameter of fertilized eggs measured 836+-10 micro m. The eggs hatched from 17 h 15 min (17:15 h) to 19:20 h after fertilization at 28.0 -29.0degC and 30.0 psu salinity. The fertilization and hatched rates were 91.0% and 33.6%, respectively. Newly hatched larvae were 1.53+-0.01 mm in total length (TL). Larvae commenced feeding at 2 day after hatched (d AH) when the mouth and digestive tract were developed and eyes became deeply pigmented. Larvae showed typical early Epinephelus type pigmentation and formation of dorsal and pelvic spines. Cannibalistic behaviour occurred with the appearance of orange pigmentation above the abdominal area at 30 d AH. Deformities were not observed throughout the rearing period. Two hundred and thirty five fishes of 50 d AH juveniles with mean TL of 28.4+2.5 mm were produced from 15,800 newly hatched larvae.