Post-Release Performance and Assessment of Cage Conditioned Japanese Flounder In Wakasa Bay, Japan

Conditioning is the process of providing individuals reared for stock enhancement with some degree of "natural" experience prior to release. Predator-free acclimation cages may help flatfish adjust to the wild environment, establish burial skills, begin pigment change, recover from transport stress, and experience live food sources before true release. Since 2008, Obama Station has conducted pre-release, experimental acclimation cage conditioning for Japanese flounder, Paralichthys olivaceus in Wakasa Bay, Japan. Recaptured fish were acquired through a cooperative effort between researchers and local fishermen. The overall objective was to describe how the characteristics of released flounder changed with acclimation cage exposure as well as to determine how recapture rates compared between conditioned and nonconditioned fish.

Immediate benefits of cage conditioning included a higher percentage of conditioned fish burying upon release and consuming natural prey. More conditioned fish were recaptured via fishermen's efforts than nonconditioned fish. This study is the first to examine flatfish conditioning strategies using commercially landed data and shows that acclimation cage conditioning can favorably alter the attributes and recapture rates of released fish. International fisheries managers and scientists can regard Japanese flounder stocking efforts as case studies from which to model and base their own developing flatfish stocking protocols.