The Nature Conservancy's Emiquon Preserve: Fish and Aquatic Vegetation Monitoring Annual Report [2012]

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

Research output: Book/Report/Conference proceedingTechnical report


Key Ecological Attributes (KEA’s) for the fish and aquatic vegetation communities at Thompson and Flag lakes of The Nature Conservancy’s Emiquon Preserve were assessed from 4/10/2012-10/29/2012. Of 18 relevant KEA’s, 13 were addressed in 2012 by aquatic vegetation and fish community monitoring. Out of 13 KEA’s addressed, 8 were met in 2012. Secchi disc transparencies taken during April-May, 2012 were always less than half the maximum water depth, while all water depths exceeded two times the Secchi disc transparencies during June-October,2012 indicating a decrease in water clarity. Also, mean Secchi disc transparencies taken during April-May decreased from 2011 to 2012, while mean Secchi disc readings from June-October were significantly greater in 2011 than in 2012 further suggesting a decrease in water clarity. Two invasive aquatic plant species including Eurasian watermilfoil and curly-leaf pondweed were collected in 2012. Eurasian watermilfoil dominated the aquatic vegetation community and was collected at more sites and at a higher density than in 2011. This suggests that it has been further propagating and is well established within Thompson and Flag lakes. Aquatic vegetation monitoring in 2012 represents the first year since monitoring began that Eurasian watermilfoil 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 than in 2011. Invasive aquatic plant species will continue to be monitored closely.The fish community was dominated bynative species in 2012. Despite this, the KEA goal of collecting ≥25 native fish species was not met. More time may be needed for less abundant species to become established and/or additional stocking may be necessary in order to meet this goal. Golden shiner dominated our catches in 2012. Catches of desirable native fishes including largemouth bass, bowfin, spotted gar, longnose gar, golden shiner, and the threatened starhead topminnow were the highest ever observed at the Emiquon Preserve. This may be due to reduced water levels in 2012, which may have resulted in the fish community becoming more concentrated. An increase in golden shiner catches may be attributed to a successful spawn in 2012, while an increase in starhead topminnow catches may be the result of a successful spawn and/or successful stocking efforts in2012. Undesirable native fish,such as gizzard shad,increased from 2011 to 2012. While gizzard shad are an energetically favorable prey fish for largemouth bass, increased density of gizzard shad may increase turbidity by inducing phytoplankton growth through feces deposition and feeding behaviours (zooplanktivores). Gizzard shad may also be a more preferred prey type by largemouth bass compared to Lepomis spp. or invasive common carp and may reduce the potential to control common carp establishment and induce a trophic cascade. Of the 18fish species collected during 2012, only two invasives were collected including common carp and goldfish. Both have the ability to reduce water clarity through their foraging behaviors by uprooting aquatic vegetation and suspending sediments and nutrients into the water column. A recent study found that common carp can also cause a decrease in aquatic vegetation and waterfowl diversity and use (Bajer et al. 2009). Common carp catches decreased from 2011 to 2012. Goldfish catches were low and were not collected in 2011.Invasive fish species will continue to be monitored closely.
Original languageEnglish (US)
PublisherIllinois Natural History Survey
StatePublished - Jan 15 2013

Publication series

NameINHS Technical Report 2013 (02)


  • INHS


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