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FISH MONITORING 265 hypoxic discharges from dams, the introduction of exotic species and water level fluctuations associated with management of the hydrological regime (Voigtlander and Poppe, 1989). In response to these threats to reser- voir quality, the TVA initiated a monitoring programme in 1989. The programme includes the collection of chemical, physical and biological data, including annual electrofishing and gill-netting, to document species composition and the abundances of littoral and pelagic fish assemblages. The programme is designed to identify problem areas that can then receive more intensive study and remediation. Within this broader TVA programme, we used electrofishing data from Tennessee River mainstem reservoirs and one limnologically and functionally similar tributary reservoir (Melton Hill) collected during four years (1989-1992). IBI metrics and modifications for reservoirs As with the IBI, each attribute, or metric, tested for use in the RFAI is based on a predicted biological response to human-induced degradation of reservoir quality (Figure 1). The metrics selected were based on the IBI designed for warm-water streams (Karr et al., 1986), information obtained through analyses of TVA rotenone data (Karr and Dionne, 1991; Dionne and Karr, 1992) and discussions with TVA biolo- gists. Tolerance classifications and designations of trophic and reproductive guilds follow those outlined in Dionne and Karr (1992). Although the conceptual framework and many features of the IBI (Karr et al., 1986) remain intact in the RFAI, several important changes reflect the biology of impoundments (Table I). The total number of species (TAXA) includes introduced species that are now permanent residents of TVA reservoirs. Although we acknowledge the importance of these species to reservoir fish assemblages, we do not consider the stocking of additional species (that may result in short-term increases in RFAI scores) to be a positive management action because non-native introductions often pose serious threats to local and regional aquatic resources (Kohler and Courtenay, 1986). IBI metrics inappropriate for use in reservoirs [number of darter species, proportion of green sunfish (Lepomis cyanellus), and proportion of hybrids] are excluded. Darter diversity in reservoirs is low compared with unmodified warm water streams in the region and the modified environment of reservoirs is conducive to hybridization. The dominant piscivore in littoral zone samples was largemouth bass (Micropterus salmoides), which are tolerant of degration; therefore, this metric is unlikely to provide an easily interpretable measure of degradation. The IBI contains a metric measuring the proportion of insectivorous cyprinids, Table I. Metrics included in reservoir fish assemblage index (RFAI) and equivalent metric in original stream index of biotic integrity (IBI) for fish RFAI metric IBI metric Species richness and composition 1. Total number of fish species (TAXA) Same 2. Number of sunfish species (TSUN) Same 3. Number of sucker species (TSUK) Same 4. Number of intolerant species (TINT) Same 5. Proportion of individuals as tolerant species (PTOL) Percentage of individuals as green sunfish Trophic composition 6. Proportion of individuals as omnivores (POMN) Same 7. Proportion of individuals as invertivores (PINV) Percentage of individuals as insectivorous cyprinids Reproductive guild composition 8. Number of migratory spawning species (TMIG) No equivalent metric 9. Number of lithophilic broadcast spawning spp. (TLIT) No equivalent metric Fish abundance and condition 10. Number of individuals (ABUN) Same 11. Proportion with diseases, parasites, anomalies (PDIS) Same 12. Fish health assessment index (FHAI) No equivalent