Post-release predation of hatchery reared marbled flounder Pseudopleuronectes yokohamae in Hiroshima Bay, Japan

Post-release survival of hatchery-reared juveniles is critical for the success of stock enhancement programs. This study investigated predation on released juveniles of marbled flounder Pseudopleuronectes yokohamae in an estuary in Hiroshima Bay, Japan, using gill nets. A total of one Chondrichthyes, 11 Osteichthyes, and three Malacostraca piscivorous species were collected, and released juveniles were found in the stomach of a Japanese seabass Lateolabrax japonicus (385 mm total length). In a laboratory experiment, predation on hatchery-reared marbled flounder by Japanese mitten crab Eriocheir japonica , which aggregated for spawning, was observed. These findings suggest that shallow estuarine environments may be suboptimal habitats, at least seasonally, for released juveniles due to the risk of post-release predation. • Post-release predation of marbled flounder was investigated. • Predation by Japanese seabass was confirmed. • Laboratory experiments revealed potential but light predation by mitten crabs was possible.