Dispersal patterns of anadromous and freshwater resident masu salmon at different spatial scales in mid-western Hokkaido, Japan

To evaluate the influences of spatial scale on dispersal, the dispersal patterns of masu salmon Oncorhynchus masou masou were investigated at among-river (ca. < 43 km) and within-river levels in mid-western Hokkaido, Japan. A genetic differentiation (F (ST)) and assignment test showed that among-river dispersal was much less common (2.9 % of 339 individuals) than within-river dispersal (7.4 % of 190 individuals). We also found that there was no bias in dispersal at the among-river level, while anadromous males were more likely to disperse at the within-river level, suggesting that the dispersal patterns may be scale dependent.