No bighead or silver carp were captured or observed in the Chicago Area Waterway System during the Fall Seasonal Intensive Monitoring (SIM) effort involving two weeks of intensive sampling in late September and early October 2025. Two grass carp were captured and later determined to be “triploid,” meaning they were bred to be sterile (it is legal in some states to use triploid grass carp for controlling algae and vegetation in small, contained waterbodies). 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.
For both 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 and U.S. Army Corps of Engineers conduct sampling using boat electrofishing. Commercial fishers working on contract for the state conduct sampling using gill nets and commercial seines.
For the 2025 Fall SIM effort, crews conducted 70 hours of electrofishing at 280 locations and set and pulled 88,000 yards of gill net at 440 locations.
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.
Since their entry into the lower Mississippi River 50 years ago, invasive carp multiplied rapidly and expanded their range, spreading north and into the major tributaries of the Mississippi River basin. Altogether, nearly 50 partners are now formally organized to carry out around 80 invasive carp management projects across both the Mississippi River and Great Lakes basins. Efforts of the Invasive Carp Regional Coordinating Committee to protect the Great Lakes are complemented by another partnership, the Mississippi Interstate Cooperative Resource Association, or MICRA, with a focus on invasive carp management in the Mississippi River basin. These are among the largest coordinated conservation efforts in North America.