Takehara Fisheries Research Laboratory, Hiroshima University, Takehara, Hiroshima 725-0024, Japan
The occurrence and feeding habits of Japanese sea bass Lateolabrax japonicus larvae and juveniles were investigated in Hiroshima Bay and the Ohta River estuary (Ohta River Diversion Channel and Tenma River) in order to compare the early life history of the species and environmental conditions of the larval and juvenile habitats with those of the Chikugo River estuary, southwestern Japan, where larvae and juveniles occur in the low-salinity water of the river. Larval and juvenile density was significantly higher in the river area than in the sea area with the highest density at 4.7-8.0 km upriver from the river mouth (salinity<12). Major prey organisms of the larvae and juveniles were Podon leuckarti, Oithona spp., Paracalanus parvus and Pseudodiaptomus inopius. The low-salinity waters of the two rivers were considered to be important habitats for Japanese sea bass larvae and juveniles with the zooplankton species as important prey resources during the early life stages, while an estuarine copepod, Sinocalanus sinensis, contributes as a single major prey organism for the Japanese sea bass larvae and juveniles in Chikugo River, southwestern Japan.