Madison, Wisconsin: Wisconsin Department of Natural Resources
The biotic index I proposed in 1977 has been widely used in Wisconsin and elsewhere to evaluate the water quality of streams. It has proven to be a valuable tool, but it is not yet perfected and results obtained through its use must be evaluated with caution. In the past two years we have used the index to evaluate more than 1,000 streams in Wisconsin and have improved our understanding of its use. We have carried out studies to determine the efficiency and accuracy of the index, have evaluated alternative sampling techniques, and have made substantial changes in many of the tolerance values. In this bulletin I wish to report on recent improvements in the biotic index, point out problems that need to be considered when evaluating results, and provide keys for identification of species in certain important insect genera.