Fish assemblage structure in natural, channelized, and restored sections of Nippersink Creek, McHenry County, Illinois

Degradation of aquatic habitats and loss of biodiversity are growing concerns of natural resource managers and the general public. Channelization, the common historical practice of straightening streams and rivers for agricultural interests, has had profound detrimental effects on the biodiversity of lotic fish assemblages. Nippersink Creek, McHenry County, IL is a twenty-three mile stream that flows through an area valued for its fish, wildlife, and invertebrate biodiversity. Although a portion of the stream was channelized in the 1950's, restoration efforts by the McHenry County Conservation District have recently restored historical meanders. Nevertheless, efforts to restore streams and rivers to their natural conditions may also have unknown detrimental effects because the process of restoration is a disturbance to lotic fish assemblages. This project assessed and compared fish assemblage structure, habitat, and biotic integrity of historically channelized, restored, and natural sections of Nippersink Creek, utilizing data collected in the natural and restored areas of Nippersink Creek and data gathered by McHenry County Conservation District before restoration efforts began. Index of Biotic Integrity scores and species richness were low overall in comparison to historical data, but were as high or higher in the restored section of Nippersink Creek than in upstream natural and downstream natural areas, suggesting that the restoration effort was successful. An analysis of habitat variables found that percent silt, gravel, and algae substrate cover were most important in shaping the fish community, although a more complete suite of habitat variables should be sampled in future studies to determine whether these variables are determinant. Findings from this study will contribute to a greater understanding of the effects of stream restoration on fish assemblages in Midwestern agricultural streams, and will be valuable in future stream restoration efforts within the Chicago area and throughout the United States.