THE NATURE CONSERVANCY’S EMIQUON PRESERVE: RESETTING AND RESTORING THE 
THOMPSON LAKE FISH COMMUNITY

Nerissa N. Michaels1, Greg G. Sass1, Timothy W. Spier2, Thad R. Cook1, T. 
Matthew O’Hara1, Kevin S. Irons1, Michael A. McClelland1, and Matt R. Stroub1

1Illinois River Biological Station, Illinois Natural History Survey, 704 
North Schrader Ave, Havana, IL 62644
2Department of Biology, Western Illinois University, 1 University Circle, 
Macomb, IL, 61455 

	Thompson and Flag lakes, located in Fulton County, Illinois, were 
historically known as two of the most productive backwater lakes of the 
Illinois River.  In the early 1920’s, Thompson and Flag lakes were leveed 
from the Illinois River, drained, and used for agricultural land.  Eighty 
years later the land was purchased by The Nature Conservancy with plans to 
restore the lakes to their natural state: a fully functional floodplain 
labeled the Emiquon Preserve.  In the spring of 2007, rotenone was applied in 
attempts to rid the existing waters of invasive and nuisance fish species.  
The remnant farm ditches and the newly reformed Thompson Lake were then 
stocked with desirable fishes by the Illinois Department of Natural Resources 
following historical accounts of native fishes once present in the lakes. 
Thus far, 24 fish species have been stocked at the Emiquon Preserve.  The 
Illinois Natural History Survey’s Illinois River Biological Station has 
conducted preliminary fish and aquatic vegetation monitoring on Thompson Lake 
since its restoration.   We used a multiple gear approach to sample the fish 
population in Thompson Lake from July thru November, 2007.  Aquatic 
vegetation sampling was limited to visual presence/absence and species 
observations to ensure low levels of disturbance during the first year of 
restoration.  We also collected a total of 1,290 fish comprised of 8 species 
during this sampling period.  Largemouth bass Micropterus salmoides 
contributed to 90% of the total catch with a mean of 376 bass/ hour 
electrofishing.  One invasive species, an individual adult common carp 
Cyprinus carpio, was collected while electrofishing suggesting rotenone 
survival or unintentional stocking.  Future sampling efforts will be 
intensified by implementing a stratified random sampling approach with 
supplemental fixed sites.  Additional research will include snorkeling 
surveys to determine fish habitat usage and fish diet analyses to 
characterize the emerging food web.  The information gained from the fish and 
aquatic vegetation monitoring and supplemental research will help manage and 
provide future management alternatives regarding restoration efforts. 

Keywords:  backwater lake, Emiquon Preserve, floodplain, Illinois River, 
restoration, The Nature Conservancy