Induced spawning and first larval rearing in Epinephelus marginatus

Methods for controlled breeding of tropical groupers have been developed from 1977, but no reliable techniques are available for mediterranean groupers. From 1995 up to 1998 several trials for hormonal induction of final maturation and spawning have been tested on wild dusky grouper females (body weight 2.2-10.1 Kg ) adapted to captivity. Three broodstocks were maintained under natural photoperiod applying both natural and controlled thermoperiods. Fish with vitellogenic oocytes (>350 m) were induced (n=8) both with Human Chorionic Gonadotropin (HCG) at 500-2000 UI/Kg dosage, given in multiple injections, and with HCG (2000 UI/Kg) in combination with sea bass pituitary (7-9mg/Kg). HCG partially mimicked natural gonadotropin, inducing ovulation only in synergy with pituitary. GnRHa-Dep in microspheres (Triptoreline, Decapeptyl, Ipsen Biotech) at 40-50 g/Kg induced multiple spawning in 50% of females (n=26) with oocytes >350 m. Vitellogenic oocytes 350 m were not sensitive to HCG, pituitary extracts, GnRHa and GnRHa-Dep. Ovulation time ranged between 66-85 hours, according to temperature (17.7°C- 24.2°C) and oocyte maturity stage. Natural ovulation of healthy eggs was never achieved. Fertilisation rate on viable stripped eggs ranged between 80-89.5%. Embryonic development lasted 50-52.5 hours and survival at hatching (100%) varied widely (0-90.9 %). Mean eggs diameter was 839  9.9 m and mean dry weight was approximately 66 g. Preliminary larval rearing trials were carried out in 500l incubators using green algae, cryopreserved oyster trochophores (30 ind/ml) and baby rotifers (Brachionus plicatilis, size 80-90 m, 30 ind/ml). Survival was approximately 90% after 12 days from hatching. The first critical period was observed between 13th-15th days with 100% mortality. Further studies to identify physiological, metabolic and trophic parameters are necessary to set up reliable larval rearing techniques.