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and (3) the fish fauna has far greater species richness than in the West. Direct biological monitoring of reference sites and sites of interest, conducted within an appropriately scaled ecoregion framework, can provide both an assessment of status and a prediction of effects, given similar stressors in similar ecoregions (Hughes et al. 1986; Omernik 1987; Hughes and Larsen 1988). Such information is generally more convinc- ing to the public and to judges than are violations of chemical criteria and flow standards (E. Bender, USEP A Office of Water Enforcement and Permits, Washington, DC, personal communication). To in- crease the accuracy of our predictions, we must combine long-term biological monitoring and experi- mental field studies of the effects of key physical and chemical variables on populations and communities. How can data on species and their abundances be made understandable to the public and to water resource regulators while retaining the ecological in- formation that is meaningful to biologists? A recent attempt to communicate such information is the In- dex of Biotic Integrity, or lEI (Karr 1981; Karr et al. 1986). The lEI is a means of quantifying ichthyol- ogists' judgments of the relative quality of a fish assemblage. It is based on a sample of the entire fish assemblage, not just game fish. The index incor- porates professional judgment of fish assemblage health in 12 metrics and their scoring criteria, which are based on regional ideals. These regional stan- dards are determined from historical data and data from minimally affected sites that characterize the region. The individual metrics differ in their range of sensitivity for detecting perturbations, and a degree of redundance is built into the IEI because no single metric can reliably indicate integrity. The metrics and variations on them (Karr et al. 1986; Miller et al. 1988; Plafkin et al. 1989) are summar- ized below. Number of native fish species Number of darter and benthic species Number of sunfish and water column species Number of sucker and long-lived species Number of intolerant species Percent top carnivore individuals Percent insectivorous individuals Percent omnivorous individuals Percent tolerant individuals Total number of individuals Percent hybrid and exotic individuals Percent diseased individuals Five of Karr's original metrics have frequently re- quired modification for streams outside the Midwest ~ THE IEI 27 (Miller et al. 1988). It may be instructive to examine this process if IEI modification is needed in the southeastern United States. The numbers of benthic insectivorous species and sculpin species were used in New England and Oregon, respectively, where darters are depauperate or rare. Both substitutions contain species that use benthic habitats for repro- duction and feeding, have small home ranges, and are sensitive to degradation. In the Southeast, mad- toms might be added to this metric. The number of native minnow or water-column species replaced sunfish species as a measure of pool quality in Oregon and the Northeast, respectively. The species in both groups are sensitive to changes in pool or water-column habitats, and sunfishes are introduced or depauperate in both regions. Insectivorous cypri- nids are a dominant trophic group in the Midwest, but where they are less dominant, Karr's original metric was changed to "all insectivores" or to "specialized invertebrate feeders." The proportion of individuals as green sunfish has been replaced fre- quently. This metric assesses the degree to which species that are tolerant to a variety of stressors dominate. Common carp, white sucker, creek chub (Miller et al. 1988), and the percent of individuals of the 12 most tolerant species (Ohio Environmen- tal Protection Agency 1988) have all been used where green sunfish were inappropriate or insen- sitive. The percent of hybrids has also been prob- lematic in several regions; introduced or exotic species were substituted in Oregon and Colorado. This modification may be appropriate in Florida also, as a measure of the breakdown of reproductive separation zoogeographically or simply as an indica- tion of biological pollution. There is growing interest in applying the IEI to water resource management. The lEI is presently being used by the Illinois Environmental Protection Agency, the Kentucky Cabinet for Natural Re- sources and Environmental Protection, the Ohio En- vironmental Protection Agency, and the Tennessee Valley Authority. Several other State agencies (Ala- bama Department of Environmental Management, Iowa Conservation Commission, Kansas Depart- ment of Wildlife and Parks, Nebraska Department of Environmental Control, New York Department of Environmental Conservation, North Carolina Division of Environmental Management, Oklahoma Department of Health, Vermont Department of En- vironmental Conservation, and Wisconsin Depart- ment of Natural Resources) and the National Park Service are testing the IEI for use as a monitoring,tool. Ohio Environmental Protection Agency (1988) uses the lEI as a legal criterion in its water quality standards program, and the USEP A supports the