Deformity of agglutinated pelvic fin membrane in hatchery-reared black rockfish Sebastes inermis and its application for stock separation study

Abstract

This study is the first to report on the high occurrence of agglutinated pelvic fin membrane deformities in hatchery-reared black rockfish Sebastes inermis. For 5 years, this symptom was marked in hatchery-reared fish, with 58.7% of fish deformed on average (varying between 46.7 and 72.0%). The deformity was a peculiarity in hatchery-reared fish, but is negated in wild fish, and was not related to whether the fish broodstock originated from the wild or from a hatchery. Mark-release experiments showed that deformed fish were almost the same as normal hatchery-reared fish in growth and survival rates, and, theoretically, the recapture numbers of hatchery-stocked fish, estimated by deformity, almost coincided with actual recapture numbers, confirmed by otolith tagging. The results of the present study indicate that deformity in hatchery-reared black rockfish is useful as a stock separation tool.