FIFTY YEARS OF THE LONG-TERM ILLINOIS RIVER FISH POPULATION MONITORING 
PROGRAM, 1957-2007.

Michael A. McClelland, Greg G. Sass, Thad R. Cook, Kevin S. Irons, T. Matt 
O’Hara, Camilla S. Smith, Nerissa N. Michaels, and Matthew R. Stroub.  
Illinois Natural History Survey, Illinois River Biological Station, 704 N. 
Schrader Ave., Havana, IL 62644.

Fishes of the Illinois River have been monitored since 1957 through the Long-
Term Illinois River Fish Population Monitoring Program.  Fish data has been 
collected annually in six reaches by AC electrofishing in a fixed site 
sampling design.  We examined fish collections over all sampling years to 
test for trends in total catches and catch rates, spatial and temporal 
changes in catch, species collections, spatial and temporal species 
composition and structure, and selected species.  We have collected 191,042 
fishes representing 97 species and seven hybrids resulting in a catch rate of 
202 fish per hour of electrofishing.  Community analyses revealed changes 
over time in species composition and structure in the upper three reaches of 
the river from a community dominated by common carp and goldfish to one with 
centrarchids and greater fish species diversity.  Species diversity also 
increased throughout the river over time, even with the exclusion of 
introduced species.  Important sportfishes such as bluegill and largemouth 
bass catches have shown considerable increase over time in many areas, while 
common carp catches decreased.  Largemouth bass catches have declined in the 
La Grange and Alton reaches since 1991.  Prior to 1991, catches of largemouth 
bass had increased since 1965.  The trends observed may reflect positive 
effects of rehabilitation efforts throughout the Illinois River.  While catch 
declines of largemouth bass in the La Grange and Alton reaches are alarming, 
our collections highlight the importance of long-term data sets and the 
ability to detect trends spanning multiple decades.  Results from our long-
term monitoring program may guide future Illinois River rehabilitation 
efforts.

Key words: Illinois River, electrofishing, fish population, population 
monitoring, long-term data

Michael A. McClelland
Illinois River Biological Station
704 N. Schrader Ave.
Havana, IL 62644
Phone (309) 543-6000
Fax (309) 543-2105
mmcclell@uiuc.edu

Platform presentation (PowerPoint), will convert to poster if necessary