EVALUATION OF FIRST-FEEDING REGIMENS FOR LARVAL NASSAU GROUPER EPINEPHELUS-STRIATUS AND PRELIMINARY, PILOT-SCALE CULTURE THROUGH METAMORPHOSIS

Two 10-day hatchery experiments were conducted to evaluate s-type (Haw aiian strain) and ss-type (Thailand strain) rotifers Brachionus plicat ilis and cryogenically preserved oyster Crassostrea gigas trochophores as first feeds for larval Nassau grouper Epinephelus striatus. Newly hatched grouper larvae were reared at densities of 11.2-20.8/L in 500- L tanks at 36-38 ppt salinity, 25-26 C, and under a 11-h light:13-h da rk photoperiod. Beginning on day 2 posthatching (d2ph), prey were main tained at a density of 20 individuals/mL, while phytoplankton (Nanochl oropsis oculata) was maintained at 500 x 10(3) cells/mL. In experiment 1, survival and growth were higher (P < 0.05) for fish fed small s-ty pe rotifers (mean lorica length = 117 mu m; fish survival = 7.96%) sel ected by sieving than for fish fed non-selected rotifers (mean lorica length = 161 mu m; fish survival = 2.13%). These results demonstrated the advantage of small prey size and suggested that super-small (ss-ty pe) rotifer strains would be beneficial. In experiment 2, three feedin g regimens were compared: 1) ss-type rotifers (mean lorica length = 14 7 mu m); 2) oyster trochophores (mean diameter = 50 mu m) gradually re placed by ss-type rotifers from d5ph; and 3) a mixed-prey teatment of 50% oyster trochophores and 50% ss-type rotifers. Survival was higher (P < 0.05) for larvae fed mixed prey (15.6%) than for those fed rotife rs (9.73%) or trochophores and rotifers in sequence (2.55%), which als o showed the slowest growth. Oyster trochophores, although inadequate when used exclusively, enhanced survival when used in combination with rotifers, possibly by improving size selectivity and dietary quality. In a pilot-scale trial, larvae were cultured through metamorphosis in two 33.8-m(3) outdoor tanks. Fertilized eggs were stocked at a densit y of 10 eggs/L and larvae were fed ss-type rotifers from d2ph-d20ph, n ewly hatched Artemia from d15ph-d18ph, 1-d-old Artemia nauplii from d1 8ph-d62ph. Survival on d62ph was 1.17%, with a total of 5,651 post-met amorphic juveniles produced.