Egg and larval development of a new hybrid orange-spotted gruper Epinephelus coioides x tiger grouper E. fuscoguttatus

Abstract

To establish a seed production technique for a new hybrid orange-spotted grouper Epinephelus coioides x tiger grouper E. fuscoguttatus the egg and larval development were observed under artificial conditions. Newly ovulated eggs from a female E. coioides of 7.5kg in body weight were measured at 0.81+-0.02mm (mean+-SD) in diameter and weighed 3,505 eggs/g. After fertilization with sperm obtained from a male E. fuscoguttatus, its diameter measured 0.83+-0.02mm. The eggs hatched from 17h 30min (17:30h) to 19:00h after fertilization at 29.0degC at 30.0 ppt salinity. The fertilization and hatching rates were 93.9% and 50.3%, respectively. Newly hatched larvae were 1.52+-0.01mm in total length (TL) and floated motionless at water surface. Larvae commenced feeding at 3 days after hatched (d AH) when mouth and digestive tract were formed and eyes became deeply pigmented. Larvae showed typical early Epinephelus type pigmentation and differentiation of second dorsal-fin and pelvic-fin spines was observed prior to 10 d AH and thereafter elongated. Larvae started shifting habitat from pelagic to benthic at 40 d AH. Seven hundred and fifty tails 50 d AH juveniles with mean TL of 22.8+-3.6mm were produced from 21,500 newly hatched larvae.