Illinois aquatic systems are economically vital, provide extensive ecosystem functions and services, and support high biodiversity, including over 200 fish species, 80 freshwater mussel species, and hundreds of aquatic insect species, many of which are Species of Greatest Conservation Need (SGCN). Unfortunately, numerous anthropogenic factors and stressors have impaired these aquatic systems and degraded their economic and ecological value. The Illinois Department of Natural Resources and state partners developed the Biological Stream Characterization (BSC) and Biologically Significant Streams (BSS) to characterize biological conditions and assemblages in Illinois’ running waters. However, both the BSC and BSS stand to benefit from updates incorporating new data and analytical approaches. Such work is imperative to ensuring that Illinois aquatic systems and the services they provide are restored from impaired conditions and conserved through well-informed management plans.
This project will update the BSC and BSS by developing biological references based on species distribution models for fishes, freshwater mussels, and EPT (Ephemeroptera [mayflies], Plecoptera [stoneflies], and Trichoptera [caddisflies]) in wadeable streams statewide. Species of greatest conservation need and Watch List species will be prioritized in these efforts. The degree of correspondence between observed conditions or biodiversity and reference biological expectations will be used to independently grade streams for each taxonomic group and for all groups collectively. Updated BSC grades will focus on the correspondence between expected and observed assemblages of fish, mussels, and aquatic insects, whereas BSS reaches will be identified as those stream reaches with observed conditions that have more diverse assemblages relative to expected conditions.