U.S.-Japan Cooperative Research: Field Tests of Interspecific Competition in Stream Salmonid Guilds in Japanand the U.S.

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This award provides support for a two year cooperative research project between Professor Kurt Fausch, Department of Fishery and Wildlife Biology, Colorado State University, and Dr Hiroya Kawanabe, Department of Zoology, Kyoto University, Japan. This project is aimed at increasing our understanding of the roles of biotic interactions and environmental factors in shaping longitudinal distributions of salmonid guilds in mountain streams. Ecologists have long sought to understand the relative roles of biotic and abiotic factors in shaping animal communities by investigating distributions of species along altitudinal gradients where environmental features and species composition change over short distances. A frequent finding is that congeneric species, which are assumed to compete strongly, occupy different positions along the gradient and overlap little. Furthermore , the distribu- tion of one or both species is usually expanded in locations where its congener is absent versus those where it is present. The objective of this research is to experimentally test whether interspecific interference competition is an important mechanism in determining the relative success of two congeners, the Japanese charr and the Dolly Varden charr, in the altitudinal zone where they are sympatric, in the Hidaka Mountains of Hokkaido, Japan. Both Professor Fausch and Dr Kawanabe are leading experts in their fields and their strengths are complementary. The project will give Professor Fausch the opportunity to undertake research in a relatively undisturbed community, and the Japanese methods of 3-dimensional mapping of positions should yield a more precise examination of interactions and displacements than generally encountered. The results of this research should provide a better understanding of the ecology of stream salmonids and animal communities in general. Stream salmonids are an economically important species and any increase in knowledge of their ecology should permit better management of streams that support them.