Koji Takeno，Mamoru Yoshiya，Toshiaki Miyajima

　

Nippon Suisan Gakkaishi, 67(6) : 1082-1088 (2001)
　

In order to clarify the stock structure of the Japanese flounder Paralichthys olivaceus in western Wakasa Bay, the first annual ring radius of the otolith were compared between immature and adult fish collected from 1994 to 2000. The average radius of the first ring in adult fish was significantly smaller than that of the same year-class immature fish. This phenomenon was observed in both female and male. Considering the previous reports which showed that there were two distinct populations as early setllers and late setllers, we speculated that the early settlers with more fin ray number grow fast and migrate to the westward at one or two years old, whereas the late settlers with less fin ray number grow slowly and stay in this area throughout their life.