Abstract
The purpose of this study is to verify the validity of the habitat assessment based on physical environments using biological community data in middle reaches of the Shibetsu River, eastern Hokkaido, Japan. We surveyed biological assemblages (fish, benthic invertebrates, terrestrial plants and birds) at 16 sites in the study reaches and examined relationships between the physical assessment results (DDR: the degree of departure in physical conditions from reference sites) and biological data: 1) abundance or diversity of species that are typical in pristine environment of the study reaches and 2) community compositions. The community compositions were analyzed by the Detrended Correspondence Analysis (DCA) ordination. Abundances of the typical fish and plant species were high in the sites that were evaluated as ‘good’ by the physical habitat assessment, whereas they were low in those as ‘degraded’. The first axis of DCA showed a gradient in species composition reflecting anthropogenic influences and correlated with DDR and many physical variables in fish, benthic invertebrate and terrestrial plant communities. The main DCA axes showed no relationship with DDR and few relationships with physical variables in bird communities. Our results showed that the habitat assessment method using the degree of departure in physical conditions from reference sites was an effective tool for comprehensive river habitat assessment.
