BIOLOGICAL MONITORING OF FISH ASSEMBLAGES IN TENNESSEE VALLEY RESERVOIRS

Reservoirs comprise an expanding proportion of global freshwater resou rces. New multimetric approaches to biological monitoring, such as the index of biological integrity, have been useful in streams; similar a pproaches in reservoirs might aid managers concerned about the reservo irs they manage. Electrofishing data from Tennessee Valley Authority r eservoirs were used to evaluate the applicability of biomonitoring to those reservoirs. Individual metrics and overall index scores exhibite d substantial annual variation. Within-year variation in scores from a supplemental data set suggests that annual changes in scores may not represent real fluctuations in resource condition. Species accumulatio n curves demonstrate that standard samples consisting of ten timed run s were not adequate; the sample error was high. Some metrics are usefu l, but they require more testing; other metrics are clearly not approp riate for use in a integrative multimetric index. Finally, the reservo irs included in this study may be similarly degraded; independent data from separate regions and watersheds are needed to resolve this and o ther issues. Although attaching qualitative judgements (e.g. excellent to poor) is premature, the concept of a reservoir biomonitoring index deserves more study, especially the development of more comprehensive and systematic sampling programmes designed to resolve sample adequac y and sources of variation in sample data.