Movement and Growth of Wild and Hatchery-reared Japanese flounder, Paralichthys olivaceus in the Sea of Japan off Northern Hokkaido

Abstract

In order to examine movement and growth, 3, 623 wild and 5, 565 hatchery-reared Japanese flounder, Paralichthys olivaceus fry were tagged and released in the Sea of Japan off northern Hokkaido in June and August 1986, respectively. Wild flounder migrated north until September and then tended to move southward in winter. Most wild flounder recoveries were recorded in the release area and the area south of the release point one year or more after release. Similar results were obtained from the tagging experiment with reared flounder. The distribution of wild and reared flounder was thought to expand toward the south. The difference between growth of wild (0.61 mm/day) and reared flounder (0.44 mm/day) was significant. It is supposed that the poor degree of adaptation of reared flounder to the natural conditions was one of the factors affecting growth.