INDUCED SPAWNING AND LARVAL REARING OF SNAPPER, PAGRUS-AURATUS (PISCES, SPARIDAE), FROM AUSTRALIAN WATERS

This study describes the hormone induction and larval rearing of wild caught snapper, Pagrus auratus, from Australian waters. Ovulation was induced by injecting human chorionic gonadotrophin (hCG) at 1000 IU kg-1. Males and females were stripped and fertilised eggs were incubated at 21.5 +/- 1-degrees-C. At hatch, larvae averaged 3.1 +/- 0.09 mm total length (TL) with a 0.6 +/- 0.02 mm yolk-sac and 0.2 +/- 0.02 mm oil globule. Feeding on rotifers started on Day 6 after hatch and initial swim bladder inflation started on Day 7. Metamorphosis was complete by Day 25 when larvae averaged 8.6 +/- 0.5 mm TL. Larvae with functional swim bladders (52% by Day 15) grew faster than those without swim bladders. Significant mortalities, of predominantly smaller fish (103 +/- 0.6 mm) without swim bladders, occurred from Day 36. About 22% of fish survived to harvest at Day 50 (mean fork length 22.1 +/- 4.8 mm). Larvae tolerated temperatures as high as 31.5-degrees-C. We compared the egg and larval development recorded in this study with that described for the northern population (red sea bream) in Japan and the southern population in New Zealand. The close similarities observed between the northern and southern populations of Pagrus auratus support recent studies recognising only one species.