Feeding and Growth of Epinephelus moara Larvae in the Process of Nourishing Transformation

Abstract:

Newly hatched larvae do not have feeding activities. Instead, they obtain nutrients from the oil globule and yolk sac during the endogenous period. The oil globule and yolk sac are gradually consumed and absorbed with the development of the larvae. Then the larvae start to feed on a combination of baits, the oil globule and yolk sac for energy, and their development progress into the mixed vegetative period. As the oil globule and yolk sac are fully consumed, the larvae develop into the exogenous vegetative stage when they acquire the nutrients solely from the external environment. Here we investigated the growth, feeding and survival of the Epinephelus moara. The larvae were divided into a fasting group and a control group. In the fasting group the larvae were deprived of feed, and in the control group they were fed on the 3rd day after hatching. The feeding was conducted at temperature (23±0.5)℃ and salinity 29-30. We found that the body length of the larvae grouper grew negatively, and that they started feeding on the 3rd days after hatching. The yolk sac and oil globules were exhausted on the 4.5 day after hatching. We also found the initial feeding rate of the larvae changed over the days after hatching, first increased followed by a continuous decrease till 0 eventually. The maximum initial feeding rate (66.67%) appeared on the 5.5 day after hatching when the yolk sac and oil globules were completely exhausted. The initial feeding rate reduced to half of the peak value on the 6th day after hatching when the larvae reached PNR (point-of -no-return). Therefore the nutrition-mixture stage of the larvae lasted for 2.5 days, and 3-6 days after hatching should be the crucial feeding period of the larvae