WHITE PERCH DISTRIBUTIONS IN THE ILLINOIS RIVER: DETECTING AN INVASIVE SPECIES 
WITH THE LONG TERM RESOURCE MONITORING PROGRAM.

Kevin S. Irons, T. Matthew O'Hara, Michael A. McClelland, and Mark A. Pegg. 
Illinois Natural History Survey, Illinois River Biological Station, 704 N. 
Schrader Ave., Havana, IL 62644

ABSTRACT: White perch Morone americana are native to the Atlantic coast of the 
United States and first gained access to the Great Lakes in the early 1900's 
with the construction of canals connecting these water bodies.  White perch have 
since spread throughout the Great Lakes and are now invading the Upper 
Mississippi River System through a connection between the Illinois River and 
Lake Michigan.  We have collected white perch along the La Grange Reach of the 
Illinois River since 1991, through the Long Term Resource Monitoring Program 
(LTRMP).  Since 1991, we have observed a growing white perch population with 
total abundance in our standardized collections rising to over 50 fish per year 
(1999).  Initial negative impacts with the native fauna include collections of 
yellow bass x white perch hybrids in the Illinois River.  It is important to 
understand the detrimental effects this invasion may have on the Illinois River 
and other ecosystems as this species expands its range. 

Keywords:  White perch, Morone americana, Illinois River, invasive species, 
hybrids, Long Term Resource Monitoring Program