Abstract

Ciliates are abundant in marine waters, but their significance as a first food for fish larvae is poorly understood, as many have no lorica to facilitate their identification in the gut of a larval fish. One of the major challenges of culturing of red snapper, Lutjanus campechanus is providing an appropriate food source at onset of feeding. Possible food organisms include species of Fabrea, Strombidium and Strombilidium with average sizes of 40 x 100, 33 x 41, and 35 x 80 µm, respectively. Optimum growth conditions evaluated were photoperiod, stocking densities of ciliates and algae, and algal food type. Techniques were developed for the consistent mass culture of Fabrea salina using 200 L solar tubes, resulting in 75 ciliates/ml in seven days.\Growth and survival of red snapper larvae was evaluated in a production setting using 1 m 3 tanks. Larvae were stocked at 10/L, 36 hours post hatch, and prior to functioning mouthparts. Three treatments were fed:\i) Copepod nauplii, 20-75µm only from days 1 to 10;\i) Copepod nauplii from days 1 to 10 plus Fabrea from days 1 to 5; and\iii) Fabrea only from days 1 to 3 plus copepod nauplii from days 4 to 10.\Copepod nauplii were added at 2/ml and ciliates were added at 5/ml. Two larvae per tank were removed daily from day 1 to 5 and once per week thereafter and photographed for morphometrics. Survival after 28 days was 0.28% and 2.39% in treatment 1 and 2, respectively. Treatment 3 did not have any survival after six days post-hatch. Larvae were more active feeders in the tanks given Fabrea and copepods as first foods with 34.6 ± 58.1% average daily reduction in copepod nauplii compared to 15.8 ± 107% reduction when only nauplii were provided. Survival was positively related to the presence of Fabrea and nauplii at first feeding.

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