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Understanding a species' historical and current distribution is critical when making conservation and management decisions. Recent observations in headwater streams of northern Illinois, USA, where no previous records of Iowa Darters Etheostoma exile occurred, revealed the need to re‐evaluate its state‐wide distribution. We conducted a series of species distribution modelling procedures coupled with targeted field surveys to generate historical and contemporary distribution models. The historical distribution model indicated E. exile distributions were concentrated across extreme northern Illinois. Both contemporary models included results of the historical model as a model variable. Based on the initial contemporary model, 30 potential Iowa Darter sites, 10 each of three groups representing low, medium and high model scores, were sampled during the summer of 2016. Field surveys provided nine new E. exile localities and presence–absence data from field surveys were then applied to revise the contemporary model. The revised contemporary model suggests a decrease in certain areas of its historic Illinois range, as well as areas where it has potentially expanded its range.

With data spanning over 120 years, the Fishes of Champaign County is a comprehensive, long-term investigation into the changing fish communities of east-central Illinois. Surveys first occurred in Champaign County in the late 1880s (40 sites), with subsequent surveys in 1928–1929 (125 sites), 1959–1960 (143 sites), and 1987–1988 (141 sites). Between 2012 and 2015, we resampled 122 sites across Champaign County. The combined data from these five surveys have produced a unique perspective into not only the fish communities of the region, but also insight into in-stream habitat changes during the past 120 years. After a period of degradation, fish communities appear to be improving throughout the county, demonstrated by the return of two state-threatened species that had not been recorded since 1928. Our analysis of in-stream habitat indicates a general trend away from small streams of various substrate types toward wider, deeper streams with a more uniform substrate. Fish community data support the results, indicating a shift from typical headwater species to those species that frequent deeper streams with more stable flows. Long-term surveys such as this are rare, and the data and analyses of these surveys can provide managers with valuable information to further restoration efforts using a historical perspective.

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