Geographical differences in stomach contents and feeding intensity of juvenile Japanese flounder Paralichthys olivaceus

Abstract

Japanese flounder juveniles were collected from 12 nurseries from southern to northern Japan and stomach contents of the juveniles, and density, biomass and species composition of mysids as the main prey for juvenile flounder, were examined. Juveniles fed mainly on mysids, small fishes, cragonids and gammarids. Mysid species composition in the field varied geographically and species richness and the biomass of mysids in the environment ranged from one to ten species and 3.0 to 1712.8 mg/m2, respectively. The most abundant species in the field occupied the majority in the stomach contents of flounder juveniles. Relative stomach fullness (RSF) on all prey items had no relation to the mysid biomass. However, RSF on mysids increased with mysid biomass in the environment to 200 mg/m2. The species composition and biomass of mysids would influence the stomach content composition and feeding intensity of juvenile Japanese flounder.