Abstract
To obtain fundamental information on the early critical period of larvae of the yellowtail, Seriola quinqueradiata, they were reared in the laboratory tanks during 10 days after hatching, with or without food.In the larvae of the starved group, the digestive organs were normal in histological structure and digestive function on 4th day, but strikingly degenerated on 6th to 9th day after hatching.It is interesting that larvae of the fed group receiving rotifers (3-5individuals per ml sea water) as food from 4th day are classified into 3 types: the starved-, semistarved-and normally feeding types.Larvae of the starved type possessed the same histological features as the larvae of starved group.The semistarved type had histologically normal digestive tract, but sotifers were not seen in the intestinal lumen.Starved larvae were 70% and the semistarved type were 0% at 6th day, 46% and 27% at 7th day, 5% and 39% at 9th day, respectively.This suggests that the unfavorable feeding condition in the early period, 4th-6th day after hatching, appears to be a main cause of the intensive death for the yellowtail larvae reared in the laboratory tanks.
