A total of 35900 in 1990 and 73400 in 1991 otolith-marked, hatchery-raised Japanese flounder Paralichthys olivaceus fry ranging from 4 to 15 cm total length (TL) were released into shallow water at depths of 4 to 8 m at Ohno Bay, northeastern Japan. The otoliths of the fish were marked 1 to 3 d prior to release with an alizarin complexone fluorescent marker The size at release of flounder recaptured by a beam trawl, set net and commercial catch was estimated using the fluorescent mark diameter

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... o TL relationship, and survival and growth rates were examined. As time progressed after release, back-calculated release size distributions gradually shlfted to larger values. The flounder fry > 9 cm at release were successful in recruiting to commercial fisheries. The major cause of mortality was thought to be predation by large flounder and greenling Hexagrammos otaku whlch were abundant in the flounder nursery ground. Growth rate of released flounder was high in the warm and low in the cold season. Individual growth rates were estimated by otolith mark diameter and TL at catch. The relationship of release size and growth rate analyzed in the flounder recaptured 1 1 mo after release indicated that survival of released flounder is strongly associated with size itself and growth rate in the field.