The answer to whether there is fish in the Chicago River is a definitive yes. The waterway is now home to a rich and expanding aquatic community, supporting a population far more diverse than many people realize. This dense, urban river system, which includes the main stem, the North Branch, and the South Branch, supports numerous fish species. This abundance is a measurable indicator of decades-long environmental engineering efforts and improvements in water quality, marking a remarkable turnaround from its heavily polluted history.
The River’s Recovery: From Pollution to Habitat
The river’s existence as a viable habitat today is the result of recovery from severe degradation. Beginning in the mid-19th century, the river was overwhelmed by industrial waste and raw sewage, leading to such poor water quality that by the 1970s, only about ten pollution-tolerant fish species remained. This contamination was a public health crisis, especially since the river originally flowed into Lake Michigan, the city’s source of drinking water.
In 1900, a civil engineering project reversed the flow of the river, sending water away from the lake and toward the Mississippi River basin via canals. While this protected the city’s drinking water, it turned the river into a channel for wastewater. The ecological turning point began with stricter environmental laws, such as the federal Clean Water Act of 1972, which regulated industrial and municipal discharge.
A subsequent infrastructure project, the Tunnel and Reservoir Plan (TARP), often called the Deep Tunnel, addressed the persistent problem of combined sewer overflows (CSOs). TARP is a vast underground network of tunnels and reservoirs designed to capture stormwater and sewage, preventing it from polluting the waterways. The captured water is pumped to reclamation plants for treatment before release. This system has dramatically reduced CSO events from an average of over 100 days per year to roughly 50. This reduction in pollutants and the subsequent improvement in dissolved oxygen levels are the primary reasons the Chicago River system has become habitable for a growing and diverse fish population.
Catalog of Aquatic Residents
The success of the cleanup efforts is clearly reflected in the sheer number of species now inventoried in the Chicago River system. Monitoring teams from the Metropolitan Water Reclamation District of Greater Chicago (MWRD) and partners like the Shedd Aquarium document a fish community of over 70 different species, an almost eightfold increase in diversity since surveys began in the 1970s.
The waterway supports a robust array of sport fish, including popular game species sought by anglers. Largemouth Bass and Smallmouth Bass are commonly found throughout the system, particularly in the quieter, vegetated areas of the North and South Branches. Northern Pike, Channel Catfish, and various species of Sunfish, such as Bluegill and Black Crappie, have also established stable populations.
The river also supports a wide range of forage and bottom-dwelling fish that form the base of the aquatic food web. These common residents include the Gizzard Shad, Common Carp, and several types of minnows and shiners. Studies focusing on fish larvae confirm that at least 24 species are successfully reproducing within the river system. The presence of larvae from pollution-intolerant species, such as the brook silverside and mimic shiner, indicates that water quality can sustain sensitive life stages.
Consumption Advisories and Safety
Despite the remarkable ecological recovery, consumption advisories remain in effect for fish caught in the Chicago River system due to the accumulation of contaminants from the river’s industrial past. The primary concern is the long-term, low-level exposure to persistent pollutants like Polychlorinated Biphenyls (PCBs) and Mercury. The Illinois Department of Public Health (IDPH) issues these advisories based on ongoing fish tissue sampling across the entire waterway.
The advisories are particularly strict for sensitive populations, including women who are pregnant, nursing, or of childbearing age, and children under the age of 15. These groups are cautioned to limit or avoid consuming certain species due to the potential developmental effects of these contaminants. For non-sensitive populations, the advice varies significantly by fish species and size, reflecting how different fish accumulate pollutants over time.
For instance, the IDPH advises against eating any Common Carp measuring 12 inches or longer from the Chicago River system because of high PCB concentrations. Smaller Common Carp are limited to six meals per year for the general public. Largemouth Bass and Channel Catfish over 18 inches carry an advisory of no more than one meal per month due to PCB levels.
Anglers are encouraged to practice catch-and-release fishing to minimize human health risks and maintain the river’s recovering fish populations. If an angler chooses to keep fish, they must consult the most current IDPH site-specific advisories for the North and South Branches, the North Shore Channel, and the Chicago Sanitary & Ship Canal. These advisories emphasize that while the river is ecologically healthier, legacy pollutants still affect the safety of the fish as a food source.