August 1, 2022
A freshwater drum, Aplodinotus grunniens. Photo by Brett Billings, USFWS.

60+ Years of Monitoring Large River Fishes in Illinois

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By Andrya L. Whitten, Jason A. DeBoer, James T. Lamer
A researcher holds a cream and dark greenish-gray mottled catfish in out stretched hands. In the background is  a ruler of measuring fish.
A channel catfish, Ictalurus punctatus.

Survey and Assessment of Large-River fishes in Illinois (commonly referred to as LTEF for Long Term Electrofishing) has been tracking changes in the Illinois River fish community, water quality and habitat since 1957. Over the years, funding and program leadership has periodically changed, but monitoring has always been conducted by Illinois Natural History Survey (INHS) biologists out of Havana, Illinois, currently at the Illinois River Biological Station (IRBS). Since 1989, funding for the LTEF program is provided by the Illinois Department of Natural Resources/U.S. Fish and Wildlife Service Federal Aid in Sportfish Restoration program.

From 1957 to 2015, LTEF crews used boat-mounted 3-phase AC electrofishing gear to sample fish at fixed side-channel border sites throughout the Illinois River Waterway (IRW). Fish were sampled at 28 sampling sites; 27 of those sites on the Illinois River Waterway (25 sites on the Illinois River and 2 sites on the lower Des Plaines River) and a single site on Pool 26 of the Upper Mississippi River (UMR) below Grafton. Sites were sampled for one hour during late August and September each year when water levels were at seasonal lows. Sampling was not conducted if water levels exceeded specific criteria established for each site, or if water temperature fell below 50° F. The database contains data for most years; funding lapses and high-water conditions precluded eight years of sampling over the entire 64-year span of the LTEF project.

A map of Illinois with the Illinois, the Mississippi, the Wabash, and the Ohio rivers highlighted in blue indicating where research had taken place.
Map of the current reaches/pools sampled on the Illinois, Mississippi, Ohio, and Wabash rivers by the LTEF program using pulsed-DC electrofishing gear.

The LTEF program expanded fisheries monitoring and research efforts on the Illinois River and portions of the UMR (pools 16, 19, 20, 25 and open river) in 2009. The expanded fisheries monitoring differs from the historic AC electrofishing protocol by using pulsed-direct current (pulsed-DC) electrofishing protocols, similar to that used by the Upper Mississippi River Restoration Program’s Long-Term Resource Monitoring (LTRM) element on the UMR system. The 3-phase AC electrofishing was discontinued after 2015, although approximately half of the historic IRW AC sites (those that still maintain high-quality fish habitat) are still sampled with the pulsed-DC gear and protocol.
The modern LTEF DC project conducts fish sampling using pulsed-DC electrofishing in three, six-week sampling periods from June 15 to October 31 primarily in main-channel border habitat, along with some historical side-channel fixed sites in the IRW. Fish data collected includes species identification, weights, lengths, and the occurrences of external lesions, parasites, or deformities. Ancillary water quality data are also collected at each site, including dissolved oxygen, water temperature, Secchi transparency, and water velocity.

The LTEF DC project was expanded in 2010 to include fisheries monitoring on the Illinois portions of the Ohio and Wabash rivers (2010 to present), the Kankakee and Iroquois rivers (2013 to 2020), and pools 17, 18 and 21 on the UMR (2013 to present). To accommodate these expansions, the INHS Great Rivers Field Station (GRFS), Eastern Illinois University, Western Illinois University (now collected by IRBS), and Southern Illinois University all conduct sampling and contribute to the LTEF dataset. The GRFS samples the Alton Pool of the IRW and the UMR Pool 25 and two reaches of open river below Pool 26. Eastern Illinois University samples the Illinois portion of the Wabash River, and Southern Illinois University samples the Illinois portion of the Ohio River. Illinois River Biological Station initially sampled UMR pools 16, 19 and 20 during the initial 2010 expansion, then in 2014, Western Illinois University started sampling in UMR pools 17, 18 and 21 in 2014-2015 before pools were reallocated in 2016: IRBS – UMR pools 16-18, WIU – UMR pools 19-21 and currently, IRBS does all sampling from UMR pools 16-21 since 2019.

A researcher holds a large gray catfish while standing in a boat in a river. Shrubby green vegetation is on the shoreline. The researcher is wearing a life-vest.
LTEF staff holding a channel catfish.

The collaboration of these LTEF partners make it possible to not only provide robust data to Illinois managers and stakeholders, but also conduct important and informative research with these data. For example, the LTEF partners collected channel catfish (Ictalurus punctatus) and freshwater drum (Aplodinotus grunniens) as part of normal annual sampling during 2017 and 2018 for a graduate student’s research project. The goal of this project was to determine and compare the population dynamics (e.g., size structure, individual growth and mortality) of these two ecologically, commercially and recreationally important fishes among the Illinois River and sections of the Mississippi, Ohio and Wabash rivers to provide a current baseline for managing these populations. As you would expect, population dynamics for both fishes varied among rivers, which gives us a better understanding of channel catfish and freshwater drum populations in these systems, which is essential to improving current and future fisheries management programs.


Andrya Whitten is a large river fisheries ecologist with the Illinois River Biological Station in Havana. She primarily works on monitoring long-term trends in fish populations on the Illinois River.

Jason DeBoer is a large river fisheries ecologist with the Illinois River Biological Station in Havana where he monitors fish populations on the Mississippi River. He has been involved with fisheries research and monitoring since 2006.

Jim Lamer is a large river ecologist and Director of the Illinois River Biological Station in Havana. He has spent the past 21 years conducting research and monitoring on the Mississippi and Illinois rivers.

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