ABSTRACT 

 The effect of municipal and industrial discharges from the Chicago-Joliet 

 area was evident in electrof ishing catches from the Des Plaines River — only the 

 introduced carp and goldfish and hybrids of these two pollution-tolerant species 

 were abundant, and most were diseased. There was a greater variety and abun- 

 dance of fishes in the Illinois, compared to the Des Plaines, and the fish were 

 generally in better condition. The Upper Illinois River has improved for fish 

 life since the 1920' s, when no fish were taken throughout much of this section. 

 The improvement is attributable to improved oxygen levels as a result of im- 

 proved waste treatment. From the 1900 's to the 1950' s, the backwater areas and 

 bottomland lakes along the river served as nurseries and havens for fish and 

 fish food organisms. In the mid-1950' s, the aquatic plants and food organisms 

 in many of these areas died out, and the areas have been seriously diminished 

 and degraded by accumulations of sediment, with a consequent decline in the fish- 

 eries. During a drought period in the mid-1960' s oxygen and water levels were 

 low, and game fish populations declined. A resurgence in the fish populations 

 occurred in 1973 and 1974, following high water levels and greater dilution of 

 pollution from 1971 through the spring of 1973. 



Richard E. Sparks 



ENVIRONMENTAL INVENTORY AND ASSESSMENT OF NAVIGATION POOLS 24, 25, AND 26, 



UPPER MISSISSIPPI AND LOWER ILLINOIS RIVERS: AN ELECTROFISHING SURVEY OF 



THE ILLINOIS RIVER 



Special Report No. 5, Water Resources Center, University of Illinois, 



June 1977, Urbana, Illinois 



KEYWORDS — electro-fishing/ fish population/fish harvest/turbidity/navigation/ 



fish food organism/Illinois River/pollution effects 



