Fishing in the Chicago River

Since Robert Cassidy described a “friendless river that decades of abuse and neglect had transformed from a great natural resource into an open sewer,” in Chicago Magazine, the Chicago River has made a remarkable comeback. In 1984, the Illinois Pollution Control Baord eliminated the fecal coliform water quality standard for water bodies classified as secondary contact (the majority of the Chicago River). Before then, MWRD has used chlorine to disinfect effluent as part of the treatment process; it discontinued this practice because of harmful effects on aquatic health. Currently, MWRD does not disinfect wastewater effluent on the Chicago River.

Another of the primary reasons water quality has improved: the requirement that the MWRD operate a pretreatment program for controlling discharges from industrial and commercial facilities. In 1985, the USEPA approved the program, and it was made a component of the district’s discharge permits. This program significantly reduced the amount of toxic metals and other pollutants released into the river.

One indicator of a healthy river ecosystem is species diversity. Since the early 1970s, the MWRD has conducted fish population surveys. The MWRD data shows that as the river’s water quality has improved, the aquatic ecosystem’s biodiversity has rebounded. The number of fish species in the river has increased from 10 in 1974 to 68 in 2005.

The greater Chicago region boasts 111 freshwater fish species–85 native, 16 non-native, and 10 hybrid. Many of these species are now also present in the Chicago River. As the river’s water quality continues to improve, we hope that several once-present species may again become viable. These include the longnose gar, cisco, grass pickerel, and freshwater drum.