The largest muskie (in weight) pulled out of a trap net since surveys began. This 39.8-pound fish was collected in April 2023 and would qualify as a state record if caught hook-and-line. Photo courtesy of Scott Bartell.
Heidecke Lake: Fisheries Management at a Former Power Plant Cooling Lake
As a District Fisheries Biologist, I encounter Illinois’ incredible aquatic natural resources on a near daily basis. I know, some of our waterbodies may not look identical to those of our northern neighbors with their pristine glacial lakes or wilderness settings. In fact, most public water within my District could be classified into two broad categories: power plant cooling lakes or reclaimed surface-mining lakes. These types of waterbodies aren’t glamorous, but you can’t always judge a book by its cover. Despite scenery and skyline looking more like the Chicago Sanitary and Ship Canal, Heidecke Lake State Fish and Wildlife Area is a very popular destination for Chicago metro area anglers.
Originally known as Collins Lake, Heidecke has an extremely fascinating history. The lake was constructed as a partially perched cooling lake for five, 500-megawatt oil and natural gas-fired generating units, and it began being filled with water from the adjacent Illinois River in 1976. The power plant began initial operations in 1978 and the final power generating unit went online in 1979. During this time, the Illinois Department of Natural Resources (IDNR; at the time known as the Department of Conservation) had taken a keen interest in working with the then owners, Commonwealth Edison, on creating an exciting and successful sportfishing lake in northeastern Illinois. As a result, several research and management projects were conducted in collaboration with Southern Illinois University Carbondale to achieve this sport fishing objective.
IDNR ultimately signed a lease agreement with Commonwealth Edison and opened the lake to recreational use in 1982. The first fish residing in the lake were not the hybrid striped bass and walleye that anglers target today, but rather fish species that found their way into the lake during initial impoundment (either directly from the Illinois River or indirectly during basin construction). Two varieties of hybrid striped bass (Sunshine and “Wiper”) were the first fish species stocked by IDNR in 1978 and 1979. Afterwards, muskie, walleye, largemouth bass and striped bass were stocked. Within this new lake, having an abundant gizzard shad forage base and heated water, these stocked sport fish survived well, grew fast and created an exceptional fishery, including many trophy-sized fish.
Heidecke Lake drastically changed in 2004 when the powerplant was decommissioned. Without the thermal load, the lake’s sportfish were not exposed to extreme thermal conditions that often plague our power plant cooling lakes. The lake’s sportfish populations have remained stable and largely unchanged ever since.
To effectively manage Heidecke Lake’s nearly 1,955 acres of aquatic resources, IDNR Division of Fisheries staff conduct various sportfish management activities through a lease agreement with the current owner, NRG Energy. Sportfish populations are assessed through trap net and electrofishing fish population surveys, and the data garnered through these surveys is then used to evaluate stocking needs and regulation efficacy. On a routine basis the lake receives muskie, walleye, hybrid striped bass and black crappie from the State Hatchery System. While the Division of Fisheries is heavily involved in the stocking and assessment of sportfish, successful lake management is only possible with the cooperation of IDNR Office of Law Enforcement and Office of Land Management. Regulations, while a necessary tool to a fisheries biologist, are only useful if they can be enforced. Furthermore, a lake is only desirable to anglers if the access facilities are maintained. Managing Heidecke Lake is certainly a team effort!
In addition to the stocked species above, Heidecke Lake’s current sportfish community includes smallmouth bass, largemouth bass, white bass, yellow bass, white crappie and bluegill. Gizzard shad are still the main forage for predators and prey abundance remains high (we caught a whopping 1,500 shad in 90 minutes of electrofishing during the October 2024 electrofishing survey). These gizzard shad are usually 3 to 5 inches long with only a few larger individuals collected.
Field work on Heidecke Lake usually starts with an annual spring muskie trap netting survey, typically occurring around the first week of April when water temperatures are roughly 50 – 55° F. Large trap nets with frames measuring 4 feet by 6 feet are used and set at specific locations throughout the South Pool of the lake. The nets are fished for three nights and checked daily. Bycatch is released back into the lake, and the muskies are held in a large tank with oxygen prior to processing. At minimum, each fish is sexed, measured, weighed and fin clipped. Recently, we have sought to better understand muskie population demographics and are now tagging muskie with Passive Integrated Transponder (PIT) tags. These tags are small glass transponders implanted in the back musculature and are only detectable with a special PIT tag receiver (similar to those implanted into dogs and cats for lost pet recovery). This tagging technique allows us to identify individual fish and track them over time once they are recaptured. After being worked up, the fish are released back into the lake.
Some years the weather can be brutal, and nets are shifted to alternate locations if wind gusts are going to make sampling hazardous. In April 2024, we collected nearly 150 muskies in 10 nets set over three days. Besides being a record catch, two of those fish were more than 48 inches in length. Catches have historically ranged from 0 (in the early years) to 91 fish in 2013, so collecting 150 muskies was quite exciting. The number of legal fish collected in recent surveys is a good indication that the muskie fishery is developing well, and Illinois muskie anglers should add Heidecke Lake to their Rolodex of places to fish. If those numbers aren’t tempting enough, a 39.8-pound female muskie was collected in the spring 2023 survey which surpasses the current 38.5-pound state record fish caught in 2002.
The rest of the fish population surveys take place in the fall, and primarily consist of fall electrofishing surveys though additional targeted surveys utilizing other gears have been conducted to assess other sportfish species. The Heidecke fall electrofishing survey usually takes place around the first week of October and might take two or three days to complete depending on weather conditions. Sampling a lake this size is quite the undertaking, and IDNR Fisheries staff from other portions of the state come and help.
While non-game fish species, such as freshwater drum and common carp are present in Heidecke Lake, sportfish are the main targets of these surveys. During the electrofishing run, stunned fish are dipped out of the water and placed into an oxygenated holding tank. After the run is complete, those fish are measured, weighed and released. Occasionally fish are sacrificed either for contaminant analysis as part of the fish consumption advisory program or for age and growth analysis. Many fish are collected during these surveys, with about 1,100 individual sportfish from 12 different species observed during the fall 2024 electrofishing survey. Sportfish collected included bluegill (n = 547), smallmouth bass (n = 204), hybrid striped bass (n = 128), walleye (n = 75) and largemouth bass (n = 68). Crappie are often collected in these surveys but not in very high numbers. These low crappie catches are not representative of the fishery but rather due to gear bias. For example, only 10 black crappie were collected in the fall electrofishing survey but a few hundred adults are collected during spring muskie trap netting. Furthermore, a few thousand young-of-year were collected during experimental fall crappie trap netting. Seasonality and gear selection impacts fish survey and angler success alike.
Heidecke Lake is one of my favorite lakes to manage. It may not be as scenic as some of the other waterbodies in the state but what Heidecke lacks in scenery, I believe it makes up for in recreational opportunity. Heidecke Lake can be a challenging lake to fish, but anglers who put in the time and effort seem to be rewarded. Ultimately, it is my objective as a fisheries biologist to help steward the resource so both current and future Illinois anglers can enjoy a day on the water casting a line.
Seth Love is a District Fisheries Biologist with the Illinois Department of Natural Resources and covers Grundy, Kankakee, Kendall, South-Cook and Will counties. While the majority of his work involves managing the waterbodies within this five-county district, he also provides technical guidance to private landowners who have pond and lake management questions.
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