Relations between Biotic Integrity and Physical Habitat in the Embarras River Basin, Illinois

This study investigated the relationship between a habitat quality index and stream fish assessment indices used to evaluate stream quality in an agricultural setting. Fish data and stream habitat quality data were collected from 13 sampling localities within the Embarras River basin. Habitat quality was measured using a stream habitat assessment procedure, a qualitative index comprised of 15 metrics. Stream quality was determined by fish species richness and an index of biotic integrity (IBI). Multiple regression analysis identified pool quality, bank vegetation, and width-to-depth ratio as the best estimators of IBI. These variables were used in creating a model for predicting IBI. This model demonstrates the potential for predicting the biotic integrity of a stream fish community from commonly collected, and often readily available, habitat data. Thus, models which use habitat information may be an important management tool which will allow for the rapid prediction of the biotic integrity of a stream, and thus permit intensive management practices to be focused on critical sites within a stream basin.