Progress towards the development of reliable hatchery technology for red snapper, Lutjanus campechanus, has been limited by inconsistent spawning and difficulties in larval rearing. W e report on recent progress to improve this technology. A trial assessing the effects of two different photoperiods (18L:6D and 24L:0D) was conducted at the University of Miami Experimental Hatchery (UMEH). A detailed protocol used for red snapper larval rearing from embryo through the completion of weaning from live to dry feeds is described.
Embryos were collected from a cohort of r ed snapper broodstock that ar e volitionally spawning regularly in copious quantities. Embryos were stocked into a cylindrical 400 liter incubation tank, treated with 100 ppm F ormalin for one hour, and hatched approximately 24 hours after collection. A total of , 114,000 larvae were split evenly across (8) 400 liter larval rearing tanks at a stocking density of 35 larvae/liter. Four tanks were subjected to a photoperiod of 18 hours of full spectrum light, while the remaining tanks were subjected to 24 hours of full spectrum light through 11 days post hatch (DPH ). Beginning at 12 DPH , all tanks were maintained with an 18 hour photoperiod. S-strain rotifers, Brachionus rotundiformis , were used as the exclusive first feeding source and were maintained at a density of 25/ml. Artemia sp. were introduced as a second feed source at 15 DPH and were co- fed with rotifers until 20 DPH. Both rotifers and Artemia were enriched with astaxanthin, a commercially available lipid supplement, algae extract, and taurine. Exchange rate was maintained at 250% per day and increased incrementally as larger feeds were introduced. Pure Oxygen and air were each lightly bubbled into each tank to maintain dissolved oxygen saturation from 6.5-9.0 mg/L. Temperature was maintained from 24.0 - 26.0 °C . Standard length, swim bladder inflation, and feed consumption were measured for each tank at 3 DPH, 6DPH, 9DPH , 12 DPH , and 16 DPH . Survival and was quantified at 12 DPH, 26 DPH , and at the completion of weaning 45 DPH. No significant differences in growth, feed consumption, or survival were detected between treatments at the conclusion of the trial . However, tanks maintained with 24 hour light showed completion of swim bladder inflation in >95% of larvae sampled by 9 DPH , while tanks maintained with an 18 hour photoperiod only showed 60% swim bladder inflation at this sample date. By 12 DPH , all tanks showed >95% swim bladder inflation. Due to this subtle, but potentially impactful difference, future larval rearing procedures should consider use of 24 hour light treatments through the completion of swim bladder inflation. Total survival across treatment groups through 12 DPH was 66%; survival was 31% at 26 DPH , and final survival at 45 DPH was 5.5%. This trial and other larval rearing trials at UMEH have demonstrated that red snapper can be raised solely on rotifers from first feeding through early larval stages. As broodstock continue to produce large quantities of high- quality eggs, a number of additional trials are planned to further optimize larval rearing protocols.