Biological monitoring of fish assemblages in Tennessee Valley reservoirs

Reservoirs comprise an expanding proportion of global freshwater resources. New multimetric approaches to biological monitoring, such as the index of biological integrity, have been useful in streams; similar approaches in reservoirs might aid managers concerned about the reservoirs they manage. Electrofishing data from Tennessee Valley Authority reservoirs were used to evaluate the applicability of biomonitoring to those reservoirs. Individual metrics and overall index scores exhibited 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 accumulation curves demonstrate that standard samples consisting of ten timed runs were not adequate; the sample error was high. Some metrics are useful, but they require more testing; other metrics are clearly not appropriate for use in a integrative multimetric index. Finally, the reservoirs included in this study may be similarly degraded; independent data from separate regions and watersheds are needed to resolve this and other 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 adequacy and sources of variation in sample data.