THE EFFECT OF A RECENTLY COMPLETED HABITAT REHABILITATION AND ENHANCEMENT 
PROJECT (HREP) ON FISH ABUNDANCES IN THE LA GRANGE REACH OF THE ILLINOIS RIVER 
USING LONG TERM RESOURCE MONITORING PROGRAM (LTRMP) DATA

Timothy M. O’Hara, Michael A. McClelland, Kevin S. Irons, Thad R. Cook and Greg 
G. Sass

Illinois River Biological Station, Illinois Natural History Survey, 704 North 
Schrader Avenue, Havana, Illinois 62644.

      The Long Term Resource Monitoring Program (LTRMP) fish component monitors 
fish communities in six regional trend areas of the Upper Mississippi River 
System (UMRS). Using this data, we evaluated the ability of the LTRMP to detect 
changes in the fish community of the La Grange Reach of the Illinois River 
following the Lake Chautauqua Habitat Rehabilitation and Enhancement Project 
(HREP).  In 1996, an estimated 46 million fish representing 34 species were 
produced and discharged from the south cell of Lake Chautauqua into the Illinois 
River. While this observation may indicate that the south cell serves as a 
spawning and nursery area for many fish species, no studies to our knowledge 
have tested for an effect of the HREP on fish recruitment to the river fish 
community. At three spatial scales (local 1 river mile (rm), regional ~10 rm, 
and reach wide 80 rm), we assessed fish catch-per-unit-effort (CPUE) data 
collected from mini-fyke net and day electrofishing gears among pre- (1993-1995) 
and post-HREP (1996-2005) periods of the Chautauqua NWR HREP. General Linear 
Model (GLM) results demonstrated no significant differences among periods or 
spatial scales in fish CPUE. Applying a Before-After-Control-Impact (BACI) 
design, we observed significantly higher catches in day electrofishing runs and 
mini fyke net sets within 10 river miles of the HREP impacted area following 
construction.  Our results may indicate that: (1) the LTRMP sampling design 
lacked sufficient statistical power to detect reach-wide effects of the HREP; 
(2) the LTRMP sampling design lacked the spatial and temporal resolution to 
detect effects; (3) the Lake Chautauqua HREP has not been established long 
enough to detect long-term trends in fish production; and/or (4) the HREP had no 
effect on fish recruitment to the Illinois River.  Our findings suggest that an 
intensive study at defined temporal and spatial scales may be required to detect 
changes in the fish community in the La Grange Reach, Illinois River as a 
consequence of HREP’s.  Nevertheless, our results also suggest that backwater 
areas of the La Grange Reach are major fish producers, and efforts to increase 
connectivity of backwaters to the mainstem river through HREP’s may be important 
for the long term sustainability of the Illinois River fish community.

Keywords: Long Term Resource Monitoring Program (LTRMP), Lake Chautauqua, fish 
communities, Habitat Rehabilitation and Enhancement Project (HREP), Upper 
Mississippi River System (UMRS)