Hokkaido Fish Hatchery, Eniwa, Hokkaido 061-1433, Japan
The variation in morphological characteristics of adult pink salmon Oncorhynchus gorbuscha collected in nine rivers in Hokkaido, Japan was surveyed in 2005 and 2006. Results of the cluster analysis and discriminant analysis suggested that the difference in meristic counts between the years was greater than that among rivers. The difference in the numbers of dorsal fin rays, anal fin rays and vertebrae between years was greater than that among rivers within year. There was a significant difference in the count of pectoral fin rays and gill rakers of the specimens among rivers, but not between years. Principal component analysis revealed that the 2006 year fish have more dorsal fin rays, anal fin rays and vertebrae, than the 2005 year fish.