Modeling Impact of Dams on Masu Salmon in Hokkaido, Japan

A predictive habitat model revealed the distribution and the degree of the impacts of damming on masu salmon in Hokkaido Island, Japan. Based on the presence/absence of the species from > 13,000 surveys conducted over the last half century at about 8,000 sites, the model predicted that the occurrence probability of masu salmon had declined sharply approximately 30 years after damming. Areas where the probability had significantly dropped were distributed throughout Hokkaido as patches of various sizes and degrees of impact. This same model can be used to identify watersheds that have high occurrence probabilities of the species; are less impacted by dams; and therefore should be prioritized for conservation. Conversely, the model can be used to identify watersheds with high potential occurrence probabilities but significant impacts from the existing dams. Such watersheds should therefore be prioritized for restoration, such as dam removal and barrier mitigation.