Effects of Prey Size, Microalgal Density, and Light Intensity on Survival of Pacific Red Snapper Larvae

Development of Pacific Red Snapper Lutjanus peru culture has been impeded by low survival in larval culture. We studied the effects of different culture conditions on larval survival in four experiments that examined (1) different-size prey at first feeding (nauplii of the copepods Parvocalanus crassirostris and Pseudodiaptomus euryhalinus; rotifers Proales similis; and a mix of these three prey types); (2) microalgal density (3 × 10⁵ and 1 × 10⁶ cells/mL); (3) the presence of adult copepods P. crassirostris in larval culture tanks compared to daily nauplius addition (Adult and Nauplius treatments); and (4) light intensity (50, 200, 500, and 1,000 lx). In experiment 1, a strong preference was observed for copepod P. crassirostris nauplii compared to other prey types. Survival at 15 d posthatch (DPH) was significantly higher in the P. crassirostris treatment (mean ± SD = 19.5 ± 10.2%) and the Mixed diet treatment (33.4 ± 9.4%). However, strange behavior of larvae was observed, followed by drastic mortality (at 15–18 DPH) when microalgal addition to larval tanks ceased. This behavior and mortality had not been observed in experiment 2 at any of the microalgal densities supplied until 20 DPH. In experiment 3, survival was evaluated at 2, 5, 7, and 9 DPH and dropped to 50% (5 DPH) in both treatments. At 9 DPH, survival was 14.8 ± 9.5% for the Adult treatment and 3.4 ± 0.9% for the Nauplius treatment. In experiment 4, a significant difference was observed for survival at 9 DPH; survival at 1,000 lx (26.5 ± 18.4%) was significantly higher than survival at 200 lx (4.9 ± 5%) and 50 lx (0.6 ± 0.6%) but was not different from survival at 500 lx (6.6 ± 3.1%). In conclusion, P. crassirostris nauplii are an adequate prey for first feeding of Pacific Red Snapper. Therefore, to improve larval survival, P. crassirostris adults should be added to the larval culture tanks. Moreover, microalgae should be present during all larval rearing, and a light intensity of 1,000 lx should be used.