1Stock Enhancement Technology Development Center, National Research Institute of Aquaculture (NRIA), Fisheries Research Agency (FRA), Saiki, Oita 879-2602, 2Seikai National Fisheries Research Institute, FRA, Ishigaki, Okinawa 907-0451, 3FRA, Yokohama, Kanagawa 220-6115, 4Diagnosis and Training Center for Fish Diseases, NRIA, FRA, Minami-ise, Mie 516-0193, 5Yashima Station, National Center for Stock Enhancement, FRA, Takamatsu, Kagawa 761-0111, 6Aquatic Animal Health Division, NRIA, FRA, Saiki, Oita 879-2602, 7Department of Marine Biosciences, Tokyo university of Marine Science and Technology, Minato, Tokyo 108-8477, Japan
The larvae of the seven band grouper Epinephelus septemfaciatus were reared until eight days post hatching in 500 L tanks under four different photoperiods: 24L:0D, 12L:12D, 6L:6D:6L:6D, and 0L:24D. Further, mass-culture experiments of the seven band grouper larvae were conducted until ten days post hatching using 100 kL tanks under natural photoperiod and 24L:0D conditions. The number of rotifers in larval guts and total length of larvae were examined at six-hour intervals. The best survival and growth of larvae were observed in 500 L tanks with 24L:0D photoperiod. In addition, larval survival rate was better in the 100 kL tank under the constant light condition. The seven band grouper larvae were suggested to be a visual feeder and their gut contents were clearly observed in tanks with 24L:0D photoperiod even during dark phases in other tanks. Therefore, it is considered that improved survival and/or growth of larvae in tanks under the constant light condition are attributed to the prolonged feeding period for larvae.