Effect of replacing darkness with dim light in the larviculture of red snapper, Lutjanus campechanus

Progress towards the development of reliable hatchery technology for red snapper, Lutjanus campechanus, has been limited by inconsistent spawning and difficulties in larval rearing. We report on recent progress to improve this technology. A larval rearing trial assessing the effects of two different photoperiods was conducted at the University of Miami Experimental Hatchery (UMEH). Four 400-L tanks were subjected to a photoperiod of 16 h of full spectrum light, and four 400-L tanks were subjected to 16 h of full spectrum light and 8 h of dim light through 11 days post hatch (dph). S-strain rotifers, Brachionus rotundiformis, were used as the exclusive first feeding source and were maintained at a density of 25 ml- 1 throughout the experimental period. Standard length, swim bladder inflation, and feed consumption were measured for each tank at 3, 6, 9 and 12 dph. Survival was quantified at 12 dph and at the completion of weaning onto dry feeds at 40 dph. No significant differences in growth, feed consumption, or survival rates were observed between treatments at the conclusion of the trial. However, tanks exposed to a treatment involving 8 h of dim light showed completion of swim bladder inflation in 92.5 +/- 10.8 % of larvae sampled by 9 dph, while tanks maintained with 16 h of light and 8 h of darkness showed a significant reduction with only 60 +/- 2.5 % swim bladder inflation at this sample date (p = 0.0131). By 12 dph, all larvae in all tanks showed >95 % swim bladder inflation success. Total survival across treatment groups through 13 dph was 66 +/- 8.0 % and 4.6 +/- 1.0 % at 40 dph when the larvae were fully weaned onto dry diets.