Illinois Natural History Survey - University of Illinois

The Emiquon Preserve 

Emiquon_resized.pngOn the left is an arial photo of Thompson and Flag Lakes while still in agricultural production in 1998, on the right is an image of the restored Emiquon Preserve in 2012

P1010059.JPGThe Nature Conservancy’s (TNC) Emiquon Preserve is one of the larger floodplain restoration projects in the United States. The Emiquon Preserve is >2800 ha in size and partly consists of the recently restored Thompson and Flag lakes located along the Illinois River between Lewistown and  Havana, IL. Historically, Thompson and Flag lakes were known as two of the most productive backwater lakes in the Illinois River valley. They were disconnected from the Illinois River in 1924 when they were reduced to agricultural drainage ditches. The area was known as the Thompson Lake Drainage and Levee district which was put into agricultural production from 1924-2006 becoming the largest agricultural farm in Illinois. TNC purchased this property in 2000 and began aquatic restoration of the site in 2007 when rotenone was applied to the remaining agricultural drainage ditches to start over by removing all fish species including invasive and nuisance fish species. Since 2007, thirty native fish species have been stocked based on historical records of what used to inhabit the two lakes.

The Illinois Natural History Survey’s Illinois River Biological Station has been contracted by TNC to monitor the aquatic vegetation and fish communities at Thompson and Flag P1010068.JPGlakes of TNC’s Emiquon Preserve from 2007-present. Aquatic vegetation and fish community monitoring use LTRM protocols to evaluate Key Ecological Attributes (KEA’s) that were developed by TNC’s Emiquon Science Advisory Board to serve as the driving management force to determine Thompson and Flag lakes restoration success. There are a total of 18 KEA’s relevant to Thompson and Flag lake restoration success that determine underwater irradiance, hydrology, aquatic vegetation community composition, fish community assemblages and composition, spawning, nursery, feeding, and over-wintering habitat. Aquatic vegetation monitoring is conducted May-September on both Thompson and Flag lakes using an aquatic vegetation rake. Thompson and Flag lakes are sampled as one water body, but spatially stratified into north, middle, and south units. A total of 30 random sites are sampled May-June and September while a total of 60 random sites are sampled during July and August, which is the peak of the growing season. At each site we record data from 6 rake subsamples around our boat, as well as, water quality parameters including Secchi, depth, water temperature, dissolved oxygen, and conductivity.

3.JPGFish community monitoring is conducted on Thompson Lake only due to Flag Lake consisting of shallow water depths and abundant aquatic vegetation which foul our sampling gears. We use a multiple gear approach at random and fixed sites, but not spatially stratified. A total of 4 electrofishing runs (15 minutes each), 4 fyke nets (24 hours each) and 4 mini-fyke nets (24 hours each) at shoreline or pseudo-shoreline (used for shoreline gear) sites, 1 tandem fyke net (24 hours each) and 1 tandem mini-fyke net (24 hours each) at open water (pelagic) sites. Water quality parameters were taken including Secchi, Secchi, depth, water temperature, dissolved oxygen, and conductivity.  

Illinois Natural History Survey

1816 South Oak Street, MC 652
Champaign, IL 61820

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