1Stock Enhancement Technology Development Center, National Research Institute of Aquaculture (NRIA), Fisheries Research Agency (FRA), Saeki, Oita 879-2602, 2Ishigaki Tropical Station, Seikai National Fisheries Research Institute, FRA, Ishigaki, Okinawa 907-0451, 3School of Human Science, Kobe College, Nishinomiya, Hyogo 662-8505, 4FRA, Yokohama, Kanagawa 220-6115, 5Diagnosis and Training Center for Fish Diseases, NRIA, FRA, Minami-ise, Mie 516-0193, 6Yashima Station, National Center for Stock Enhancement, FRA, Yashima, Kagawa 761-0111, 7Aquatic Animal Health Division, NRIA, FRA, Saiki, Oita 879-2602
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8Department of Marine Biosciences, Tokyo University of Marine Science and Technology, Minato, Tokyo 108-8477, Japan
The larvae of longtooth grouper Epinephelus bruneus were reared in a 150 kL tank until ten days post hatching under a natural photoperiod condition and diurnal rhythms of feeding and tryptic activity of larvae were examined. Further, effects of different photoperiods (24L: 0D, 12L: 12D, 6L: 6D: 6L: 6D, and 0L: 24D) on larval survival, growth and feeding were examined using 500 L tanks until 11 days post hatching. The longtooth grouper larvae fed on rotifers during light periods and tryptic activity was highest at 7 p.m. Larval gut contents were quite few during dark periods and larvae did not grow and survive in tanks with 0L: 24D photoperiod. The number of rotifers in larval guts was low in tanks with 24L: 0D photoperiod thought larvae fed on rotifers slightly at night. Total length and survival rates of larvae reared in tanks under 24L: 0D and 6L: 6D: 6L: 6D conditions showed similar low values, and best growth and survival rates were observed in tanks under 12L: 12D condition.