The Nature Conservancy's Emiquon Preserve Fish and Aquatic Vegetation Monitoring 12-Year (2007-2018) Field Report

Olivea M. Mendenhall, Levi F. Solomon, James T. Lamer

Research output: Book/Report/Conference proceedingTechnical report


Since 2007, The Emiquon Preserve (Emiquon) has been monitored using Key Ecological Attributes (KEA) to determine the success of restoration on the vegetation and fish communities. The indicators outlined in the KEA’s are used to determine if the desired ranges are being met to provide an overall healthy ecosystem. From 2016-2018, Emiquon experienced fluctuating stages of water level management and in 2018, water reduction occurred during most of the sampling season and during the peak of the growing season (July/August). The impacts of the drawdown on flora and fauna are still being evaluated as restoration efforts continue in the future. Emiquon continues to maintain a robust population of fish, maintaining a dominance of primarily native fish over time (98%). Additionally, native submersed aquatic vegetation (SAV) abundance and richness continue to be the dominant macrophyte communities. Submersed aquatic vegetation species diversity has remained stable and native species dominate the community composition. However, the abundance of non-native eurasian watermilfoil (Myriophyllum spicatum) has increased until 2018, when water levels were reduced over the growing period. This drawdown reduced abundance and composition of native SAV present but also reduced the detections of non-native eurasian watermilfoil. The number of fish species found continues to grow and the number and biomass of native species remains above the desired range. Largemouth bass (Micropterus salmoides) abundance threshold greater than 100 fish/hr wasn’t attained in most years; however, Emiquon remains a popular destination for anglers. Although the goal of 100 fish/hr has not been achieved in most years, the random and fixed site design of the U.S. Army Corps of Engineers’ Upper Mississippi River Restoration (UMRR) Program’s Long-Term Resource Monitoring element (LTRM) does not target sites based on habitat that would possibly increase catch rates of largemouth bass, thus preventing this goal from being achieved. The native fish population dominates in both abundance and composition. The success of adult fish and presence of young-of-year (YOY) fish indicate Emiquon is providing abundant spawning, nursery, and over-wintering habitat for fish. Several species (~12 of 32)of stocked fish have not been detected since being introduced by the Illinois Department of Natural Resources. Additionally, a limited connection to the Illinois River in 2013 likely introduced several riverine fish including species initially stocked but not detected until after being inundated. Water clarity decreased over the last 12 years. Secchi disc transparency (Fig 24) has decreased since 2009, dropped substantially in 2012 (drought year) and 2018 (which mimicked a drought year due to drawdown), and conductivity increased (Fig 23). Dissolved oxygen levels throughout the seasons are within their respective ranges (Tables 2, 3, & 4). Anecdotally, in 2016, it was common to find softball size and larger bryozoan communities; however, in 2018 they were largely absent except for small communities observed on vegetation samples. The presence of bryozoans often indicates good water quality.
Original languageEnglish (US)
PublisherIllinois Natural History Survey
StatePublished - Jul 31 2019

Publication series

NameINHS Technical Report 2019 (16)


  • INHS


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