Changes in growth,higher salinity tolerance and behavioral traits in Japanese flounder Paralichthys olivaceus after repeated cross-breeding

ABSTRACT:     To improve stock enhancement strategies, the influences of repeated cross-breeding on several traits were studied in hatchery-reared juveniles of the Japanese flounder. Ten families (seven caught in the wild and three from cross-bred brood fish) were produced by artificial fertilization. Ninety-four days after hatching, we investigated settlement, burying in the sand and escape behavioral traits, and then measured tolerance of high salinity and six morphological traits. Juveniles from the repeatedly cross-bred brood fish showed significantly higher growth and tolerance than those from the wild-caught brood fish. Among the behavioral traits, a significantly lower settling speed and incidence of burying in the sand were observed in the juveniles from the repeatedly cross-bred families. Heritability ( h ²) of growth traits was more than 0.2 in both origins, while that of other traits was close to zero. These results suggest that repeated cross-breeding of Japanese flounder under hatchery conditions improves growth performance and leads to the loss of certain behavioral traits that are considered essential to survival in wild environments.