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

—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. Fish species exhibit diverse morphological, ecological, and behavioral adaptations to their natural habitat and, thus, are particularly effective indicators of the condition of aquatic systems (Karr et al. 1986; Fausch et al. 1990; Simon and Lyons 1995). Human disturbance of streams and landscapes alters key attributes of aquatic ecosystems: water quality, habitat structure, hydrological regime, energy flow, and biological interactions (Karr and Dudley 1981). The index of biological integrity (IBI) was developed to assess the condition of water bodies by direct evaluation of biological attributes (Karr et al. 1986). The IBI is a composite index that integrates structural, ecological, trophic, and reproductive attributes of fish assemblages at multiple levels of organization * Corresponding author: [email protected] Received April 14, 1999; accepted March 16, 2001 (Fausch et al. 1990). Originally developed for assessment of Midwestern U.S. warmwater streams, it has been modified for use in other regions and waters (Miller et al. 1988; Jordan et al. 1993; Simon and Lyons 1995; Lyons et al. 1996; Hughes and Oberdorff 1999), as well as for other taxa (Lenat 1993; Kerans and Karr 1994; DeShon 1995). Several authors have argued that the IBI must be modified when it is applied in different ecoregions (Fausch et al. 1984; Miller et al. 1988). In the Mid-Atlantic region, researchers have developed IBIs for specific ecoregions (Scott and Hall 1997; Roth et al. 1998; Smogor and Angermeier 1999) or applied it to specific systems (Leonard and Orth 1986). Our objective was to develop a single IBI for assessing the condition of fish assemblages in first-order to third-order streams throughout the upland ecoregions of the mid-Atlantic states. 858 MCCORMICK ET AL. There has been a long history of human impact on the landscape, streams, and fish assemblages of the region (Denevan 1992). Streams in the highlands have been subjected to stresses from acid deposition, mining, logging, agriculture, and urban development (Raitz et al. 1984; Whitney 1994; Jones et al. 1997). Agriculture and clear-cutting of highland and valley forests exacerbated soil erosion and sedimentation (USDA 1996). Active and abandoned coal mining resulted in mine drainage that affected approximately 4,000 km of streams (Herlihy et al. 1990; USEPA 1995). Extensive areas of the Ridge, Blue Ridge, and Appalachian Plateau ecoregions have poorly buffered soils and steep slopes, which have also made streams draining these areas susceptible to acid precipitation (Herlihy et al. 1993). Brown trout Salmo trutta, rainbow trout Oncorhynchus mykiss, common carp Cyprinus carpio, and large warmwater species in the genera Micropterus, Lepomis, and Ameiurus were stocked in streams of the Mid-Atlantic Highlands by the U.S. Fish Commission and state agencies (Courtenay et al. 1986; Jenkins and Burkhead 1994). Hatcheries were established in the 1870s to culture trout and warmwater game fishes in response to the loss of native species and public demand for augmented sport fisheries. Other introductions, particularly those of forage fish, occurred to support sport fisheries or as bait bucket transfers (Nico and Fuller 1999). Nonindigenous species constitute as much as 33% of the fish fauna of the Potomac drainage and 48% of the fish species in the upper Kanawha (New) River drainage (Appendix 1; Hocutt et al. 1986; Jenkins and Burkhead 1994). The purpose of this research was to develop an index of biotic integrity for the Mid-Atlantic Highlands region of the United States that could be applied in assessing the condition of small, wadeable streams in the region.