Electrof ishing survey 30 May 1991 Page 2 



Summary of Maior Findings in 1990 



The analysis this year focused on the upper Illinois River where the fish 

 populations have been affected adversely in the past by waste discharges from the 

 Chicago-Joliet metropolitan area, but where game fish populations seem to be recovering 

 as waste treatment improves. 



The condition of largemouth bass, smallmouth bass, white bass, and carp, as 

 measured by relative weight, Wr, improved between 1982 and 1985 in the upper Illinois 

 River, but declined by 1989. Wr of the three basses were all above 1.0 by 1985. In 

 contrast, the Wr of channel catfish peaked earlier, at slightly better than 1.0 in 1983, and 

 has since declined to just above 0.8. 



Another indicator of a long-terra improvement is the development of a sport 

 fishery for sauger in the upper Illinois River. Sauger first appeared in substantial 

 numbers in our catch in 1979 in the upper river, confirming that return of the sauger is 

 a relatively recent event that appears to be associated with water quality improvements 

 made during the decade of the 1970's, starting with the Clean Water Act of 1972. 



Although the increased catch of sauger and the improvement in Wr of 4 of 5 

 species over the last 10 years are encouraging, the decline in Wr values between 1985 and 

 1989, and the further decline in 1990, are worrisome, particularly since 2 other agencies 

 have obtained similar findings. The Illinois Department of Conservation has noted the 

 same decline in several species of game fish in their electrofishing collections from the 

 river in 1989 and 1990, and Southern Illinois University reports a decline in the Wr of 

 sauger (personal communication. Dr. Roy Heidinger, Professor of Fisheries, Department 

 of Zoology, Southern Illinois University, Carbondale, Illinois, 9 April 1991). 

 Representatives from all three agencies met in Springfield on 9 April 1991, with 

 representatives from the Illinois Environmental Protection Agency and the Metropolitan 



