Fish

By 2002, the USEPA reports that more than 99% of wastewater treatment facilities in the Illinois River basin provide “maximum levels of treatment” (Herndon 2002). Many species of fish benefit from the improvement in water quality that occurs as a result. Beginning in 1987 and 1988, the game fish population experiences a rebirth. Carp, bullhead, drum and occasionally a catfish were the common fish captured by fishermen until 1988. Now, there are large populations of smallmouth and largemouth bass, sauger (Figure 44), walleye, white bass, and even an occasional pike. Biologists also see shovelnose sturgeon and paddlefish with greater frequency. There is also a decline in numbers of the common carp (Herndon 2002).

Figure 44: Sauger (Manitoba Fisheries)

While the fisheries of the Illinois River have improved due to improved water quality, there is a continuing catastrophic decline in fish habitat areas due to sedimentation. Game fish need cover to feed and protect their young. They also need deep water to escape temporary water quality problems common in summer months, and to avoid being “flushed downstream in mid-winter by floodwaters when low water temperatures make them too lethargic to move.” Deeper water outside navigation channel habitats is vital to meet these needs (Herndon 2002).

As an example, largemouth and smallmouth bass and crappie (Figure 45) populations require adequate spawning areas for nest building and for consistent water levels during egg incubation and hatching. These conditions occur in one of every three or four years, meaning there is a strong class of these species every few years.

Figure 45: Black Crappie (Pomoxis negromaculatus) (USEPA)

The young fish are subject to severe stress during the winter because of the lack of deep water habitat. Fewer individuals survive. It is therefore rare for largemouth bass in the Illinois River to attain 4 years of age. As a consequence, few game fish are able to reach trophy size, affecting fishing opportunities. The exceptions are walleye and sauger. The Peoria and Starved Rock pools have large populations of these species, such that people from across the United States come to participate in fishing tournaments on the upper river (Herndon 2002).