Effect of habitat components on competitive interaction between native white-spotted charr and introduced brown trout

In salmonid species, interspecific competition has been affirmed as the major mechanism of the replacement of native species by introduced species. However, competitive interactions are variable according to various habitat components. Our study on native white-spotted charr and introduced brown trout in a small creek in southwestern Hokkaido, Japan indicates that the intensity of the interspecific competition was reduced in structurally complex habitats, areas with numerous woody debris, because the native species were able to survive in those environments. Therefore, the replacement may be inhibited in structurally complex habitat.