CHAMPAIGN, Ill., 3/16/23: Using data spanning 120 years, scientists in the Illinois Natural History Survey (INHS) have a unique view of long-term changes in stream fish populations and their habitats in Champaign County. The best news: several fish species that were last seen here in the 1960s have returned to the county, suggesting some streams are improving.

Champaign County fish surveys were first taken in the late 1880s, with subsequent monitoring in 1930, 1960, and 1988. INHS ecologists resampled 122 sites in the county between 2012 and 2015.

“This legacy project has produced the longest long-term dataset of freshwater fishes in one area and at the same sites, maybe in the world,” said Jeremy Tiemann, aquatic ecologist in the INHS, a unit of the Prairie Research Institute at the University of Illinois. “Surveys of five different time periods show how streams in the county have changed and how the fish assemblages have responded.”

Understanding and documenting changes related to urbanization, agricultural practices, pollution, and other factors are critical for fish conservation. Land use practices had the most significant effect on Champaign County fishes, according to the study.

In the prairies of east-central Illinois pre-development, shallow ditches of gently flowing streams were common. As row-crop agriculture was introduced, the streams were dredged to allow excess water to be removed from the fields quickly. These altered streams became deeper with more unstable flows, favoring tolerant fish populations that thrive in those conditions.

Now more than 80 percent of land in the county has been incorporated into drainage districts. Changes to headwater streams have worked downstream to cause changes in fish communities. The slender madtom and the banded darter, fish species associated with larger substrates on stream bottoms, have been replaced by species that prefer smaller substrates, such as sand and gravel. Some species, such as the Mississippi silvery minnow and bluntnose darter seem to have disappeared entirely in the county because of habitat changes.

The growing urban populations of Champaign and Urbana have affected stream fishes, especially related to pollution, including road-salt runoff into waterways. Accidental releases of industrial chemicals and livestock feedlot wastes commonly result in fish kills. Such events were recorded in the 1960s and 1990s reports, so the problem of polluted streams is hardly new.

In the past 10 years though, several state-threatened fish species have returned to Champaign County streams. The bigeye chub, last seen in Illinois in the 1960s, has made a comeback in the state, and is now found in the Boneyard Creek. The eastern sand darter and the bluebreast darter are two other welcomed species to the area. The bullhead minnow was found in the latest survey and had not been seen since the survey in 1930.

“We are really excited to see their return,” said Tiemann. “That’s likely a product of how well Urbana has treated their wastewater. They’ve always been good, using cutting-edge technology, but they’ve taken a step further to reduce chloride in wastewater. With that, we’ve seen at least four fish species come back and another four species for the first time ever in the county.”

Overall, the county streams seem to be healthy, but the study focused on five separate basins, as fish populations and other factors vary by site. Champaign County is unique in that it is the headwaters of five different river basins: the Sangamon and Kaskaskia, both draining into the Mississippi River; and the Vermilion, Little Vermilion, and Embarras, all draining into the Wabash River.

“Continued fish monitoring going forward will allow us to understand how streams will alter with the changing climate,” Tiemann said. “We see a lot of flooding, which can play a critical role in fish habitats and the health of fish populations.”

Co-authors of the study publication, “Fishes of Champaign County, Illinois: As Affected by 120 Years of Stream Changes,” included Joshua Sherwood, project coordinator, and Jeffrey Stein. The study was published in the Illinois Natural History Survey Bulletin.

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Media contact: Jeremy Tiemann, 217-244-4594, jtiemann@illinois.edu