Effects of temperature and salinity on artificially reproduced eggs and larvae of the leopard grouper Mycteroperca rosacea

The effects of temperature and salinity on eggs and larvae of the leopard grouper, Mycteroperca rosacea, were studied. Eggs from hormone-induced spawning were artificially fertilized. The effect of temperature (20, 24, 26, 28, and 30°C) on hatch rate, notochord length, yolk sac volume, and oil droplet diameter was recorded. Times from fertilization to 50% hatch and hatching period duration (first to last hatch) were also recorded for each temperature. The effect of temperature (20, 24, 26, and 28°C) on survival, growth rate, and final larval lengths 5 days after fertilization was demonstrated. The effect of salinity (0 per thousand, 8 per thousand, 16 per thousand, 24 per thousand, 32 per thousand, 40 per thousand, 48 per thousand, 56 per thousand, and 64per thousand) on hatching rate and larval lengths at hatch was recorded. Additionally, the effect of salinity (0 per thousand, 10 per thousand, 20 per thousand , 30 per thousand, and 40 per thousand) on survival and growth of larvae until total absorption of the yolk sac was demonstrated. Also, egg buoyancy at different salinities was established. Results indicate better hatching rates (70-78%) in temperatures ranging from 24 to 30°C than at 20°C. The notochord length of newly hatched larvae was inversely related to temperature and to the oil droplet diameter. Larvae that hatched at 20°C were the longest and had the smallest oil droplet diameters and yolk sac volumes. The largest yolk sac volumes were observed at 26 and 28°C. Times from fertilization to 50% hatch and hatching period duration decreased with increasing temperature. A higher larval growth rate to day 5 after fertilization was obtained at higher temperatures. Eggs maintained at 32per thousand salinity showed the best hatching rates (80.7%). In the salinity growth trial, final notochord lengths of the larvae were inversely related to salinity. Eggs were buoyant at salinities above 34 per thousand.