Development and Validation of an Index of Biotic Integrity for Coldwater Streams in Wisconsin

Abstract The index of biotic integrity (IBI). developed from information on the structure, composition, and functional organization of fish assemblages, is used to assess the health of aquatic ecosystems. We analyzed two large statewide data sets on stream fish assemblages to develop and test a version of the IBI for application to Wisconsin coldwater streams (maximum daily mean water temperature usually 24°C), for which an IBI already exists. High-quality coldwater streams have few species, with salmonids and cottids dominating. and lack many of the taxonomic groups that are important in high-quality warmwater streams. In contrast, high-quality warmwater streams have numerous species, and cyprinids, catostomids, centrarchids, and percids typically dominate. Environmental degradation often causes an increase in species richness in cold...