IDNR presents Fox River fish-survey findings; Saint Charles committee seeks environmental information on local dam

Tristan Whitlow, river and streams biologist for Northeastern Illinois with the Illinois Department of Natural Resources, told the Saint Charles Natural Resources Committee that IDNR’s 2022 Fox Basin survey documented measurable fish-community improvements after dam removal projects and that the agency uses fish-community metrics to rate stream health.

Whitlow summarized the agency's basin survey program and methods and said the Index of Biotic Integrity (IBI) — a composite score ranging 0–60 based on 10 community metrics — is used to determine whether a site fully supports aquatic life. "We'd love to see all our IBIs at or above 41," Whitlow said, adding that a score of 41 or higher indicates no aquatic-life impairment under EPA reporting tied to the Clean Water Act.

The IDNR presentation included regional examples and before-and-after monitoring: Whitlow said IDNR documented 38 dam projects regionally (13 in the Fox Basin), 34 full removals and more than 500 miles of river reconnected. He gave averaged, survey-derived numbers showing species richness increasing from about 8 to about 22 species after removals, catch-per-unit-effort (fish/hour sampled) rising from about 79 to roughly 612 on average, and mean IBI scores increasing from 22 to 33 — changes Whitlow called statistically meaningful.

Whitlow also highlighted rare or state-threatened species found in limited locations (examples included Ozark minnow limited to Salmonock Creek, modeled sculpin, river redhorse and American brook lamprey) and described how the presence of certain suckers and hogsuckers serves as an indicator of higher-quality habitat. He said dams can truncate distributions: in 2022, only about 25% of species were found across all four Fox River segments they analyzed, while 45% showed discontinuous distributions that could be linked to dams.

Committee members asked technical questions about local concerns. When asked whether dredging of Lake Holiday could affect the findings, Whitlow said dredging can disturb and move sediment downstream and that such operations generally require state and federal permits and timing restrictions to avoid spawning seasons. On whether engineered fish passages (ramps or ladders) work, Whitlow said such structures are used and fish do use them when designed and maintained, but they can require ongoing upkeep and sometimes are engineered poorly (he cited Yorkville’s bypass as an imperfect example).

Local committee discussion focused on the Saint Charles dam. Committee members said they want environmental information without making a commitment to remove the dam. A committee member noted the city must respond to IDNR by a date the committee believes is January 31 and emphasized that any letter should request the environmental information as a nonbinding step. The committee’s moderator said Wes Couture of the IDNR Office of Water Resources told them he would be willing to speak with the group and members suggested inviting Couture and reviewing form letters used by nearby municipalities.

Administrative items completed during the meeting included acceptance of minutes from the committee’s Oct. 14, 2025 meeting and acceptance of the public services tree-activity report for October 2025 (both approved by voice vote). Marceline reported community-program statistics, including a pumpkin-collection total of 1,525 pumpkins and participation data across Saint Charles and neighboring communities.

Next steps recorded in the meeting: the committee agreed it wants the IDNR environmental information study before settling on any position regarding the Saint Charles dam and noted an outreach step to invite IDNR staff to a future meeting. No formal commitment to remove the dam was made during the session.