Development and application of an index of biotic integrity for fish communities of wadeable Monongahela River tributaries

We developed an index of biotic integrity (IBI) to assess the health of fish communities inhabiting low-order tributaries of the Monongahela River in Pennsylvania. Environmental stressors observed were urbanization, agriculture, raw and treated sewage discharges, net alkaline mine drainage, and acid mine drainage (AMD). Species richness ranged from zero in streams impacted by AMD and/or untreated sewage to 24 in our reference stream. Our IBI classified the majority (> 90%) of streams in this region as significantly stressed, receiving qualitative evaluations of fair to very poor. Moreover, of the 4,090 fishes collected, only four species representing 2% of the total number collected were classified as intolerant to pollution.