The construction of erosion control dams and the alteration of riparian forest are known to have strong influences on the density of salmonid fish that dominate in mountain streams. Our objective was to elucidate the indirect effect of the dam construction and riparian alteration on stream invertebrates through the alteration of salmonid fish (Oncorhynchus masou ishikawae) density. The densities of two dominant invertebrate species, Baetis yoshinensis and Baetis thermicus, were low at study sites with high O. masou density. In conclusion, our study suggested that human activities indirectly affect stream invertebrates via changing fish abundance in mountain streams.
