IDENTIFICATION OF HABITAT CONDITIONS INFLUENCING NON-NATIVE ASIAN CARPS 
REPRODUCTION IN THE UPPER MISSISSIPPI RIVER SYSTEM.

Matt O’Hara , Kevin S. Irons, Greg G. Sass, Thad R. Cook, , Michael A. 
McClelland,  Nerissa N. Michaels, and Matt R. Stroub.  
Illinois River Biological Station, Illinois Natural History Survey, 704. N. 
Schrader Ave., Havana, Illinois 62644

Since 2000, the La Grange Reach of the Illinois River has boasted the highest 
densities of invasive bighead Hypophthalmichthys nobilis and silver carp H. 
molitrix (henceforth, Asian carps) within the Upper Mississippi River System 
(UMRS).  While precise cues and habitat conditions that trigger Asian carps 
spawning events are mostly unknown, hydrologic and fisheries data collected 
by the Long Term Resource Monitoring Program (LTRMP) and other sources may 
provide insights for Asian carps expansion, establishment, and sustainability 
in the UMRS.  In this study, we tested for the influences of abiotic habitat 
conditions (e.g. water temperature, river discharge, river stage, dissolved 
oxygen, conductivity) on young-of-year Asian carps catches (surrogate for 
successful spawning) in the La Grange Reach of the Illinois River.  Our 
preliminary results suggest that increased catches of young-of year Asian 
carps are correlated with summer water temperatures and flood pulses.  
Increased catch rates of young-of year Asian carps lagged approximately 2 
weeks from peak summer river discharge and stage events.  Drought years in 
2002 and 2005 (i.e. no summer flood) showed little or no Asian carps 
reproduction, while 2007 (i.e. three summer flood) had three distinct Asian 
carps spawning events as evidenced by young-of year catches.  Although 
preliminary, our examination of the La Grange Reach will be expanded to other 
regional trend areas of the LTRMP with Asian carps present (Open River, Pool 
26) to test for similarities or differences in reproductive cues.  
Ultimately, this research may inform managers in uninvaded portions of the 
UMRS in regards to whether appropriate conditions and cues exist for Asian 
carps establishment and sustainability.   

Kewords: Bighead Carp, Silver Carp, Illinois River, temperatures, expansion, 

Matt O'Hara
704 North Schrader Ave.
Havana, Illinois 62644
309/543/6000
t-ohara@uiuc.edu

Platform presentation