The Nature Conservancy's Emiquon Preserve: Fish and Aquatic Vegetation Monitoring 6-year (2007-2012) Report

Todd D. VanMiddlesworth, Nerissa N. Michaels, Andrew F. Casper

Research output: Book/Report/Conference proceedingTechnical report


A revised version of Key Ecological Attributes (KEAs) developed in 2006 for fish and aquatic vegetation communities at Thompson and Flag lakes of The Nature Conservancy’s Emiquon Preserve were assessed during 2007-2012. Of 19 relevant KEAs, 13were evaluated in 2007, 15 in 2008, 16 in 2009, 15 in 2010, 18 in 2011, and 16 in 2012 through standardized monitoring of the fish and aquatic vegetation communities. Of the total KEAs evaluated during 2007-2012, goals for 9 were met in 2007, 12 in 2008, 12 in 2009, 11 in 2010, 12 in 2011, and 11 in 2012. Secchi disc transparencies collected monthly (April-October) at three fixed Secchi sites (north YSI pole, pumphouse ditch mouth, pumphouse) and two fixed pelagic fish sites (tandem fyke, tandem mini-fyke)decreased during 2008-2012 indicating reduced water clarity overtime. Two invasive aquatic plant species (i.e., Eurasian watermilfoil and curly-leaf pondweed) were collected during 2008-2012. Eurasian watermilfoil dominated the aquatic vegetation community in 2012in that it was collected at more sites, at a higher density than any other species, and at a higher density than previous years(i.e.,rake densities were higher than any other aquatic plant species rake density or percent cover). In contrast, curly-leaf pondweed was collected at fewer sites and at a lower density in 2012 than previous years. Invasive aquatic plant species will continue to be monitored closely.The fish community collections were dominated by native species during 2007-2012. Despite this, the KEA goal of collecting ≥25 native fish species has not been met. Additional stocking efforts and more time may be needed for less abundant species to become established in order to meet this goal. Also, a planned reconnection to the Illinois River may establish more native species. Catch rates of native fishes including largemouth bass, bowfin, spotted gar, longnose gar, gizzard shad, golden shiner, and the threatened starhead topminnow were the highest ever observed at the Emiquon Preserve during 2012. Increased catch rates of these species may be due to reduced water levels in 2012, which may have resulted in the fish community becoming more concentrated allowing for greater detectability. Gizzard shad are a preferred prey type of largemouth bass and an increased density of gizzard shad may increase organic turbidity by promoting phytoplankton growth through feces deposition and feeding on zooplankton. Gizzard shad may also be a more preferred prey type by largemouth bass compared to Lepomis spp. or invasive common carp and increased density of gizzard shad may reduce the potential for largemouth bass to control common carp establishment. Of the all fish species collected during 2007-2012, only two invasives were collected (i.e.,common carp and goldfish). Common carp catch rates increased from 2007-2011 and decreased in 2012, while goldfish catch rates have remained low. Both species have the ability to reduce water clarity through their foraging behaviors by suspending sediments and nutrients into the water column. Common carp and goldfish also have the potential to be detrimental to submersed aquatic vegetation by uprooting plants and reducing water transparency. A recent study conducted on a similar floodplain lake complex showed that high common carp density can cause a decrease in aquatic plant density and waterfowl diversity and use (Bajer et al. 2009). Invasive fish species will continue to be monitored closely.
Original languageEnglish (US)
PublisherIllinois Natural History Survey
StatePublished - Jan 15 2014

Publication series

NameINHS Technical Report 2014 (01)


  • INHS


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