Evaluation of First‐Feeding Regimens for Larval Nassau Grouper <i>Epinephelus straitus</i> and Preliminary, Pilot‐Scale Culture through Metamorphosis

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<jats:title>Abstract</jats:title><jats:p>Two 10‐day hatchery experiments were conducted to evaluate s‐type (Hawaiian strain) and ss‐type (Thailand strain) rotifers <jats:italic>Brachionus plicatilis</jats:italic> and cryogenically preserved oyster <jats:italic>Crassostrea gigas</jats:italic> trochophores as first feeds for larval Nassau grouper <jats:italic>Epinephelus striatus</jats:italic>. 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 dark photoperiod. Beginning on day 2 posthatching (d2ph), prey were maintained at a density of 20 individuals/mL, while phytoplankton (<jats:italic>Nanochloropsis oculata</jats:italic>) was maintained at 500 × 10<jats:sup>3</jats:sup> cells/mL. In experiment 1, survival and growth were higher (<jats:italic>P <</jats:italic> 0.05) for fish fed small s‐type rotifers (mean lorica length = 117 μm; fish survival = 7.96%) selected by sieving than for fish fed non‐selected rotifers (mean lorica length = 161 μm; fish survival = 2.13%). These results demonstrated the advantage of small prey size and suggested that super‐small (ss‐type) rotifer strains would be beneficial. In experiment 2, three feeding regimens were compared: 1) ss‐type rotifers (mean lorica length = 147 μm); 2) oyster trochophores (mean diameter = 50 μm) gradually replaced by ss‐type rotifers from d5ph; and 3) a mixed‐prey teatment of 50% oyster trochophores and 50% ss‐type rotifers. Survival was higher (<jats:italic>P <</jats:italic> 0.05) for larvae fed mixed prey (15.6%) than for those fed rotifers (9.73%) or trochophores and rotifers in sequence (2.55%), which also 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<jats:sup>3</jats:sup> outdoor tanks. Fertilized eggs were stocked at a density of 10 eggs/L and larvae were fed ss‐type rotifers from d2ph‐d20ph, newly hatched <jats:italic>Artemia</jats:italic> from d15ph‐d18ph, 1‐d‐old <jats:italic>Artemia</jats:italic> nauplii from d18ph‐d62ph. Survival on d62ph was 1.17%, with a total of 5,651 post‐metamorphic juveniles produced.</jats:p>

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