Development of an Index of Biotic Integrity for the Mid-Atlantic Highlands Region

Abstract

From 1993 to 1996, fish assemblage data were collected from 309 wadeable streams in the U.S. Mid-Atlantic Highlands region as part of the U.S. Environmental Protection Agency's Environmental Monitoring and Assessment Program. Stream sites were selected with a probabilistic sampling design that allowed regional estimates of stream condition. We examined responses of 58 fish assemblage metrics to physical, chemical, and landscape indicators of disturbance. Univariate and multivariate analyses of relationships among fish metrics, habitat integrity, and anthropogenic disturbance were used to develop a fish index of biotic integrity (IBI) for assessing stream condition in the entire region. Of 58 candidate metrics 9 were selected and scored continuously from 0 to 10; the resulting IBI was scaled so that it ranged from 0 to 100. Regional estimates of stream conditions showed that 27% of the stream length in the Mid-Atlantic Highlands had fish assemblages in good or excellent ecological condition. Of the total wadeable perennial stream length in the region 38% was fair and 14% was poor. There were insufficient data to calculate IBIs for 21% of the wadeable stream length in the Mid-Atlantic Highlands; all of these streams were small (watershed area ≤2 km²) and lacked sufficient sample size (<10 individuals) to calculate an IBI.