1Stock Enhancement Technology Development Center, National Research Institute of Aquaculture, Fisheries Research Agency, Saiki, Oita 879-2602, 2Department of Marine Biosciences, Tokyo University of Marine Science and Technology, Minato, Tokyo 108-8477, 3Shibushi Station, National Center for Stock Enhancement, Fisheries Research Agency, Shibushi, Kagoshima 899-7101, Japan
To obtain basic knowledge on sinking death syndrome which has been considered to be one of the causes of early mortality during the seedling production of greater amberjack, ontogenetic changes of larval body density were examined. A rearing experiment was conducted to investigate the effects of aeration rate (0.1-2.0 L/min) on the vertical distribution, feeding, survival, growth and initial swim bladder inflation of larvae reared in 500-L tanks for 10 days post hatching. Greater amberjack larvae showed negative buoyancy. In tanks with aeration of 0.1-1.0 L/min, larvae were distributed in the upper layer in the daytime and on the tank bottom in the nighttime after 3 days post hatching. Excessive aeration (2.0 L/min) caused larvae to disperse in tanks. However, feeding amounts, and rates of survival, growth and initial swim bladder inflation of larvae were low in those tanks with rearing seawater of high turbulence. To prevent the larvae from sinking to the tank bottom, rearing techniques with less physical stress on larvae should be developed.