ABSTRACT

The ability of the Index of Biotic Integrity (IBI) to reflect anthropogenic disturbance depends directly on the validity of the assumptions used to score each metric. This chapter examines uni-, bi-, and multivariate relations between measures of disturbance and potential IBI fish metrics for wadeable warmwater streams in each of three physiographic regions in Virginia. It investigates if fish metrics relate to selected habitat variables in ways consistent with prevailing IBI assumptions, how these relations differ among IBI regions, and which fish metrics useful for stream-fish IBIs in Virginia. Variables were employed that presumably reflected anthropogenic disturbance manifested throughout watersheds, along riparian zones, and in stream channels. The chapter also examines metrics that presumably reflect effects of typical anthropogenic disturbance on fish communities and are relatively easy to determine from field data. Consistent with prevailing IBI metric assumptions, one would expect that more-disturbed sites will have more trophic or reproductive “generalists” and fewer “specialists” than less-disturbed ones, and vice versa.