Kyoto Institute of Oceanic and Fishery Science, Kyoto 626-0052, Japan
Meristic characteristics were studied in Japanese flounder Paralichthys olivaceus collected in western Wakasa Bay with the focus on two distinct populations. The numbers of dorsal and anal fin rays were compared between immature and adult fish collected from 1994 to 2000. Matured adult fish collected in the spawning season had significantly lower number of dorsal and anal fin rays compared to the immature fish collected in the same area. Considering the previous reports which showed that there were two distinct populations as resident (lower fin ray number) and migrant (higher fin ray number), we speculated that the higher fin ray number population emigrates westward from western Wakasa Bay at one or two years old, whereas the lower fin ray number population stays in this area throughout its life.