The development of yolk-sac larvae of red snapper Lutjanus campechanus from endogenous utilization of nutrient sources to the development of feeding ability is described, with the aim of better understanding the high mortalities observed at first-feeding. Larvae from several spawns were reared at a salinity of 31 and a temperature of 28°C. Yolk utilization rate, changes in body parameters and the development of morphological characters were observed. Maximum standard length (L S ) and body depth were observed concurrently with yolk-sac exhaustion at 56 h postfertilization (hpf). A decrease in L S , body width and body depth was observed following yolk-sac exhaustion. Orbit pigmentation, followed by jaw articulation, were observed at 65 hpf. Substantial cranial and body cavity development occurred in the absence of visible yolk material. Complete absence of visible yolk-sac material and less than 2% of the oil globule volume at hatching were observed at the time of development of feeding ability. This indicates an absence of a transitional feeding period and the critical nature of first-feeding in this species within controlled environments. KEY WORDS: Red snapper · Larval development · Yolk utilization · Endogenous reservesResale or republication not permitted without written consent of the publisher

To allow for the initial identi¢cation of practical diet formulations for red snapper culture, the present study was conducted to evaluate the e¡ects of feeding varying levels of dietary protein and lipid on growth and body composition of juvenile and sub-adult red snapper. Twelve diets were formulated to contain varying levels of dietary protein and lipid. In trial 1, juvenile red snapper (initial mean weight 5.9 g) were o¡ered diets with graded levels of dietary protein (32%, 36%, 40%, 44%) and practical energy to protein ratios. In trial 2, juvenile red snapper (initial mean weight 8.64 g) were o¡ered isonitrogenous diets (44% protein) containing graded levels of dietary lipid (8%, 10%, 12%, 14%). Sub-adult ¢sh (initial mean weight 151.5 g) were used in trial 3 and maintained on diets similar to those of trial 1 (32^44% protein). Sub-adult ¢sh (initial mean weight 178.3 g) in trial 4 were o¡ered isonitrogenous diets containing 32% dietary protein and graded levels of dietary lipid (6%, 8%, 10%, 12%). There were no signi¢cant di¡erences in growth, feed e⁄ciency ratio (FER) or survival in juvenile ¢sh. Juvenile ¢sh o¡ered 32% dietary protein exhibited a signi¢cantly greater (P 5 0.0497) protein conversion e⁄ciency (PCE) than ¢sh o¡ered a diet containing 44% dietary protein. Juvenile ¢sh in trial 2 also had signi¢cantly higher (P 5 0.005) intraperitoneal fat ratios (IPFRs) at 14% dietary lipid than ¢sh o¡ered diets containing 81 0% dietary lipid, and displayed trends towards greater protein as a percent of whole-body composition at 8^10% dietary lipid. Sub-adult snapper in trials 3 and 4 showed no signi¢cant di¡erences in growth, FER or survival. However, in trial 4 there was a general trend towards increased % weight gain (P 5 0.0615), FER (P 5 0.0601) and ¢nal mean weight (P 5 0.0596) with increasing levels of dietary lipid. Fish in trial 4 o¡ered 6% dietary lipid also had signi-¢cantly lower (P 5 0.0439) IPFR and PCE (P 5 0.0188) than ¢sh o¡ered 12% dietary lipid. Based on data obtained from these trials, inclusion of dietary protein at levels of 32^36% appears su⁄cient to support growth. For this level of protein, dietary lipid should be $ 10% in order to meet the energetic demands of the ¢sh and to spare dietary protein for growth.

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