The index of biotic integrity (IBI) integrates 12 measures of stream fish assemblages for assessing water resource quality. Initially developed and tested in the Midwest, the IBI recently was adapted for use in western Oregon, northeastern Colorado, New England, the Appalachians of West Virginia and Virginia, and northern California. The concept also was extended to Louisiana estuaries. In regions of low species richness, the IBI proved difficult to apply and often required extensive modification. Adapting the 1BI to those regions required that metrics be replaced, deleted, or added to accommodate regional differences in fish distribution and assemblage structure and function. Frequently replaced metrics include: proportion of individuals as green sunfish (Lepomis cyanellus), proportion of individuals as insectivorous cyprinids, proportion of individuals as hybrids, and number and identity of sunfish and darter species. The proportion of individuals as top carnivore metric was often deleted. Metrics added include total fish biomass and the number and identity of minnow species. These modifications generally followed the original IBI concept and its theoretical underpinnings. Problems remain in establishing tolerance rankings and scoring criteria, and adjusting scoring criteria for gradient differences in streams of similar size. The IBI holds promise for direct biological monitoring because of its strong ecological foundation and flexibility. Vermont, Tennessee Valley Authority, Ohio, Kentucky, and Illinois have incorporated the IBI into their monitoring or standards programs. The IBI thus serves as a quantitative, biological goal for water resource management.

Application of the “incremental methodology” is limited in many situations because quantitative information on microhabitat preferences of fishes is scarce, and because few field tests of the validity of the assumptions have been conducted. In this study, two critical assumptions were tested and the incremental methodology was applied in a warmwater stream in southeast Oklahoma. Habitat-suitability curves were developed for the freckled madtom Noturus nocturnus, the central stoneroller Campostoma anomalum, and the orangebelly darter Etheostoma radiosum. The assumption that depth, velocity, and substrate are perceived independently in the selection of microhabitats by these fishes was tested. The relation between standing stock and usable habitat (weighted usable area) was then investigated for these species as well as for adult and juvenile smallmouth bass Micropterus dolomieui. Fish population estimates were made quarterly over 2 years at four study sites concurrent with estimates of weighted us...

We examined habitat-use patterns in a fish assemblage in a large warmwater stream in West Virginia. Fish species and life stage composition and densities differed among habitat types, and five habitat-use guilds (edge pool, middle pool, edge channel, riffle, and generalist) were proposed. Larger centrarchids used deep habitats with slow velocities, whereas young centrarchids used shallower habitat. Juvenile and adult smallmouth bass Micropterus dolomieui were nearly ubiquitous in the habitats of the study area, although densities were highest among snags. Minnows and darters used shallower areas, but the range of velocity used differed among species and life stages. Vegetated and channel edge habitats served as nursery areas. Total fish densities were highest in edge pool, backwaters, snags, edge riffles, and riffles. Nearshore, structurally complex habitats seem important in influencing the assemblage structure of fishes of large streams.

A recently proposed index of biotic integrity (IBI), which applies features of indigenous fish communities to assess watershed and stream quality, is based on the assumption that community features change consistently with stream degradation. In this study, the IBI was modified for and applied to small coolwater streams in the Appalachian Plateau region of West Virginia. Changes in fish community variables proposed for the IBI were tested in seven similar streams exhibiting a wide range of stream degradation due to sewage, mining, and urbanization. A consistent response with increasing stream degradation was found for the following variables: Total number of species, proportion of individuals as creek chubs Semotilus atromaculatus, species richness and composition of darters (Percidae), number of fish in sample, and proportion of fish with disease or anomalies. Proportions of omnivores, insectivorous cyprinids, and herbivore‐detritivores yielded inconsistent results due to confounding interactions with species tolerance, whereas alternative trophic metrics, the proportions of specialist insectivores and generalist feeders, produced consistent trends with increasing stream degradation. A modified IBI, based on six fish community attributes, exhibited close agreement with independent rankings of stream degradation.