No bighead or silver carp were captured or observed in the Chicago Area Waterway System during the Spring Seasonal Intensive Monitoring (SIM) effort involving two weeks of intensive sampling in late May 2025. One grass carp was observed in the Cal-Sag, but crews were unable to capture it. Grass carp are occasionally observed during the SIM and removed whenever possible. The SIM is conducted in the Chicago waterway twice per year as part of an interagency effort to monitor for the presence of live bighead or silver carp.
The Chicago Area Waterway System connects the Illinois River, where invasive carp are abundant, to Lake Michigan, representing a possible pathway for invasive carp to spread to the Great Lakes. The current invasive carp population front on the Illinois River is approximately 47 miles from Lake Michigan and is heavily monitored, with harvest efforts conducted in downstream waters to remove carp and reduce the risk of upstream movement. Furthermore, the Electric Dispersal Barrier System is active in Romeoville, 37 miles from Lake Michigan, providing an additional line of defense against upstream carp movement. Though invasive carp remain well downstream of Lake Michigan, sampling in the Chicago waterway plays a critical role in assessing any population changes and providing a first response capability in the event of invasive carp detections.
For the Spring and Fall SIM efforts, partner agencies under the leadership of the Illinois Department of Natural Resources meticulously sample hundreds of sites throughout the Chicago Area Waterway System. Crews from the Illinois Department of Natural Resources, U.S. Fish and Wildlife Service, U.S. Army Corps of Engineers conducted sampling using boat electrofishing. Commercial fishers working on contract for the state conducted the sampling using gill nets and commercial seines.
For the 2025 Spring SIM effort, crews conducted 70 hours of electrofishing at 280 locations, set 81,600 yards of gill net at 408 different locations and set 3,200 yards of commercial seine at 4 locations in Lake Calumet.