The effects of temperature on eggs and yolksac larvae of the Nassau grouper (Epinephelus striatus) were examined under controlled, hatchery conditions. Artificially-fertilized eggs, obtained by induced spawning of captive adults, were stocked (36 eggs per l) into 15 500 l cylindroconical indoor tanks at temperatures of 26, 28 and 30 degrees C, with five tanks per treatment. A salinity of 37 g l(-1) and a photoperiod of 12 L: 12 D were maintained. Incubation time to hatching was inversely related to temperature, decreasing from 24.9 h post-fertilization (p.f.) at 26 degrees C to 20.4 h p.f. at 30 degrees C, but hatching success (avg. = 82.5%) did not vary with temperature. Survival of pre-feeding larvae declined more rapidly at the higher temperatures to 91.4, 80.7 and 42.2% by Day 1 p.h, at 26, 28 and 30 degrees C, respectively, indicating that early survival was influenced by factors unrelated to feeding. Development time to the first-feeding stage was inversely related to temperature, decreasing from 86 h p.f. (2.54 d p.h.) at 26 degrees C to 71 h p.f. (2.11 d p.h.) at 30 degrees C. Lower temperatures delayed starvation, with survival falling to 32.3, 9.3 and 1.2% by Day 4 p.h. at 26, 28 and 30 degrees C, respectively. A temperature of 26 degrees C is deemed advantageous to higher temperatures for incubating eggs and for rearing first-feeding larvae, although even lower temperatures may be feasible. Temperatures within an ecological range can markedly influence development rates of E. striatus eggs and yolksac larvae and hence, dispersal potential, first-feeding and survival in the field.
