Assessing changes in the Presque Isle Bay watershed fish community using a modified index of biotic integrity: before and after the elimination of combined sewer overflows

An index of biotic integrity and species rich- ness were used to assess changes in the Presque Isle Bay watershed fish community before and after the elimina- tion of combined sewer overflows (CSOs). The fish community was sampled with a backpack electrofisher in2011 at12stream locationson4 tributaries ofPresque Isle Bay, Erie County, Pennsylvania. All sites were previously sampled in 2001. Significant increases in speciesrichnessand indexofbiotic integrity(IBI)scores were observed in 2011 compared to 2001. The signifi- cant increases in species richness and IBI scores oc- curredfollowing theeliminationof10CSOs to Garrison Run, 7 CSOs to Cascade Creek, and 37 CSOs to Mill Creek. Despite the increasedrichness and IBI scores,the fish community remains in poor condition, which may be related to the highly urbanized land use of the water- shed. Urbanland uses comprise 77% of the Presque Isle Bay watershed, and in both 2011 and 2001, the water- shedasawholedidnotmeetwarm-waterhabitatcriteria. It is unlikely that the fish community will continue to recover without addressing urbanization throughout the watershed.