| Bioassessment can be performed through several methods and with different bioindicators. In Canadian Areas of Concern (AOC), fishes are used as a proxy for site condition. The Index of Biotic Integrity (IBI), a multimetric index for biological assessment, has been applied to fish data across Canadian AOCs to detect recovery. Previous studies, however, have indicated the IBI is not sensitive to assemblage changes characteristic of later stages of recovery. In this study, the IBI and multivariate methods were applied to data from two AOCs, the Detroit and St. Clair rivers. The results revealed that the IBI is susceptible to species substitutions within metric categories. The substitutions produced high variability within narrative ranks and rendered the IBI insensitive to changes, detected by multivariate methods, in the fish assemblage. In the absence of reference sites, the multivariate analyses were supplemented with the development of a reference condition based on best professional judgment. |
