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IL Fox River Connectivity & Habitat Study

The Illinois Department of Natural Resources is currently implementing an initiative within the State of Illinois to remove dams for the purpose of habitat restoration, fish and mussel recolonization, water quality improvement and human safety. The ILDNR has in turn requested that the USACE move the Fox River Fish Passage Project forward under the Section 519 WRDA 2000, Illinois River Basin Restoration authority to ascertain the feasibility of restoring important riverine habitat within the Fox River. The need for riverine ecosystem restoration of the study area is based on extensive habitat, organism and water quality studies conducted by state, regional and local agencies and groups. The data and results from these studies clearly show that the dams have severely degraded the natural riverine continuum.


The Fox River and its surrounding watershed are highly valued ecological and recreational resources. Currently, there are 15 dams on the river’s mainstem in Illinois, 3 in Wisconsin and numerous smaller dams on tributaries. Many of these dams were originally built in the 1800’s to provide mechanical power for grist and lumber mills and have since been rebuilt to maintain the flat water ponds or impoundments that form upstream of the dam. Although important in their time, most dams today serve no functional purpose except the single purpose of recreational boating. The ILDNR, Fox River Ecosystem Partnership (FREP), Fox River Study Group (FRSG) and other supportive groups have identified dam removal as an important watershed management tool to effectively recover the riverine ecosystem of the Fox River ecosystem.


The quality of aquatic habitat available to fish and invertebrate communities differed substantially between free-flowing and impounded portions of river. The distribution of fish species among station types during summer indicated that most fishes favored free-flowing portions of river over impounded areas created by dams. The natural flowing river reaches have more species, four times the abundance, and double the number of harvestable-sized sport fish. Also, there are more Sucker (including State Endangered River Redhorse (Moxostoma carinatum)), Darter:Percidae, and intolerant fish species, a higher percentage of riverine specialized Minnows:Cyprinidae, and a lower proportion of diseased individuals than impounded areas. Impounded stations typically had lower species richness, low overall and sport fish abundance, more diseased fish, and a predominance of tolerant and omnivorous species, such as Common Carp (Cyprinus carpio) and Green Sunfish (Lepomis cyanellus). In addition to altering habitats, dams appear to have altered distributions of nearly one third of Fox River fishes by acting as barriers to upstream fish movement. Free-flowing reaches supported higher quality macroinvertebrate communities than impounded waters above dams. Dams also prevent freshwater mussels from reestablishing populations in areas where they once were abundant. Free-flowing sites had higher catch per unit effort, extant species richness and lower percent missing species than impounded sites. Data also suggests that dams limit the upstream distribution of 5 mussel species.

Funding and Planning

The work on this study is being cost shared with the Non-Federal Sponsor, Illinois Department of Natural Resources at a ratio of 65/35.  The local cost share dollars for the Feasibility Study are being provided to the ILDNR by the Fox River Study Group through a Joint Funding Agreement.

Types of Deliverables

The Feasibility Study will be released for public review prior to its completion.  The release is currently scheduled for February of 2023.  In order to be notified please join our mailing list.


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