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EMIQUON PRESERVE - THOMPSON LAKE
Lake Information
County: Fulton
Acreage: 4000
Average Depth: 0.00 feet
Recreational Amenities
Boat Fishing? Electric only
Boat Ramps? Yes
Boat Rental? No
Skiing? No
Swimming? No
Picnicking? Yes
Camping? No
There are no zebra mussels in this lake.
Fish Stocking | |||
Year |
Species |
Size |
Count |
2023 |
Alligator Gar |
Adult |
1007 |
Additional information for stocking on Thompson Lake - Emiquon
Fishing Outlook ( Full PDF Report )
Click here for a list of all reports.
Species |
Rank |
Fish Status |
Average | In 2023 the bluegill population was sampled by 372 fish by electrofishing. The survey samples represent a bluegill population with a distribution from 1.2 to 8.5 inches long. The bluegill recruitment was low again in 2023. The last high recruitment year for bluegill was in 2019. The body condition remained good for the fish over 5 inches.The bluegill electrofishing collection rate for stock size fish (over 3.1 inches) was 1.8 fish per minute in 2023. This is close to the 1.4 fish per minute in 2022. But this is a decrease from 2.1 fish per minute in 2021 and from the 3.4 fish per minute collected in 2020. This density trend will be evaluated in the future. The Bluegill population structure appears to be primarily under 7 inches in length. There are lower numbers of quality bluegill than have existed at Emiquon since 2019. The dense areas of submerged aquatic vegetation is the key to allow the current bluegill population the potential for an excellent spawn and recruitment. These large areas of vegetated habitat would also provide a preferred niche for the Lepomis sp. in competition with the expanding gizzard shad and common carp population. However, these vegetation areas have not been present at high levels in the last 3 years. | |
Fair | The bowfin population was sampled by 96 fish in the spring trap net survey and 29 fish in the fall electrofishing surveys. The size ranged from 14.3 to 31.0 inches in length. Several year classes appear to be present. The body condition of many of these fish was average to poor in 2022 and 2023. There is no easy explanation for this, and it will be evaluated going forward. The bowfin population has seen an increase in density and biomass in the sampling over the past 10 years. In 2023, the electrofishing rates were .16 fish per minute. This is consistent with the 5-year average collection rate for the Emiquon Preserve. | |
Very Good | 60 channel catfish were sampled in 2023 by electrofishing and 143 in trap nets. This continues the upward density trend since their consistent sampling that started in 2014. In 2023, the size ranged from 13.3 to 30.8 inches in length. The body condition was good in 2023. If turbid water conditions exist in the future, channel catfish recruitment should continue at a high level. | |
Good | The black crappie population was sampled by 151 stock-sized fish by electrofishing in 2023. The black crappie electrofishing collection rate was .81 fish per minute for all sizes in 2023. This rate was below the previous 5-year average of 2.2 fish per minute of electrofishing. The black crappie sample shows a low number of fish in the YOY class up to 5.9 inches long and multiple year classes from 7.9 to 14.0 inches long. The body condition was still good for the fish over 8 inches. The white crappie population was again sampled at a low density at .14 fish per minute. The size range was from 5.9 to 13.6 inches in length. The body condition average was very good. The future emergence of the white crappie population to a common occurrence will probably depend upon the water clarity. In a lake habitat with both species of crappie, the black crappie tend to dominate in clearer water, while the white crappie tend to succeed with more turbid conditions. The overall crappie density was reduced in both the trap netting and electrofishing surveys in 2023. This lower density trend is evident in all the Centrarchidae populations in Emiquon in 2023. A dense crappie population with larger fish present, will feed on the gizzard shad population and provide additional predation upon potential exotic and invasive fish species reproduction. | |
Average | In 2023, the largemouth bass population was sampled by 90 fish by electrofishing. The largemouth bass population was defined by an average year of recruitment with 8 fish sampled from 4.4 to 8.0 inches. The fall 2023 electrofishing survey indicated that the largemouth bass population density has continued to drop. The collection rate of stock-sized bass (over 8 inches) dropped from 1.4 fish per minute in 2021 at 155 pounds per hour, to .67 fish per minute at 87 pounds per hour in 2022, and down to .44 fish per minute at 65 pounds per hour in 2023. This was a decline from the 2.5 fish per minute and 246 pounds per hour collected in 2020. The goal is a collection rate of 1 bass per minute. The bass population structure is currently skewed high due to the limited number of fish under 12 inches in length. 84% of the Emiquon bass population was over 12 inches in length. The body condition rating did remains at a good level. The previous 5 years had shown a trend of lower body condition values for the bass from 16 to 19 inches. In 2021 thru 2023 the largemouth bass data was much improved for this size group of fish. Overall, the largemouth bass population appears to be declining in overall density. The population appears to be in balance with the current forage and water conditions available in the Emiquon Preserve. The main concern will be the need for stronger year class production and recruitment over the next several years. The goal of the initial 18-inch minimum size limit was to create a high density bass population. The predation exerted by this population is necessary to control the exotic and invasive fish reproduction and recruitment that may occur. This predation is also the key to maintain the native species balance within the habitat. | |
Poor | In 2023 the pumpkinseed population was sampled by 2 fish by electrofishing. These fish were both 2.4 inches in length. The pumpkinseed electrofishing collection rate for stock size fish (over 3.1 inches) was 0 fish per minute. This continues the rapid population decline over the last 5 years. Our electrofishing effort in the large rip rap in front of the control gate in the main ditch held all the fish sampled in 2023. Dense stands of submerged aquatic vegetation will be a key to allow the current pumpkinseed population the potential for an improved spawn and recruitment in the future. | |
Poor | The yellow bass introduction into the Emiquon Preserve has allowed this population to expand rapidly since 2018. The catch per minute rate by electrofishing went up from .49 fish per minute in 2020 to 1.2 fish per minute in 2021 and 1.1 fish per minute in 2022. However in 2023, the catch per minute dropped to .36 fish per minute by electrofishing. And the corresponding catch rate per trap net night went from 26.2 in 2021, to 14.5 in 2022, and then to 12.8 in 2023. The body condition of the yellow bass was also noted by poor condition in 2023. It is interesting to note that the yellow bass population appears to be showing a similar decline as noted with the Centrarchidae populations in Emiquon. | |
Location: The Nature Conservancy's Emiquon Preserve is adjacent to the Illinois River in Fulton County, Illinois, approximately 1 mile northwest of Havana and 3 miles southeast of Lewistown.
Description: Historically, what is now the Emiquon Preserve included two backwater lakes, Thompson Lake and Flag Lake, and was argued to have been one of the better hunting and fishing complexes in the Illinois River Valley if not the whole Midwest. From the early 1920s through the present, most of the property currently owned by the Conservancy was managed for agriculture, most recently primarily for intensive row-crop production. In 2007, the site pumps were shut off and the water level in the site was allowed to rise and reform the lakes. The current Thompson/Flag Lake covers approximately 4,000 surface acres. The lake topography is two large shallow basins with deep water ditches dissecting it. In midsummer, the lake basins can be 70% covered with aquatic vegetation.
History and Status of the Sport Fishery: In 2007, The Nature Conservancy entered into a cooperative fish management agreement with the Illinois Department of Natural Resources for the Emiquon Preserve. The water bodies on the site underwent an immediate fish rehabilitation project to remove exotic fish species. The IDNR initiated fish restocking in 2007 with brood fish that included: llargemouth bass, white crappie, black crappie, bluegill, bowfin, spotted gar, channel catfish, brown bullhead, warmouth, orangespotted sunfish, pumpkinseed sunfish, golden shiner, brook silverside, and blackstripe topminnow. IDNR fish stockings and surveys have resulted in the potential of at least 43 fish species now present in the lake.
In 2023, the total nonnative fish collected were 63 common carp, 4 silver carp, 2 grass carp, 1 bighead carp and 2 carp x goldfish hybrids.
These new fish species collections probably entered the Preserve from the Illinois River through the new control structure site. The size of these fish indicate that they arrived through a large passage like the control structure. The silver carp, bighead carp and the grass carp had extremely robust body conditions. Their growth rate is currently at an accelerated rate in the Preserve. No reproduction and recruitment has been documented at this time for the Asian carp species.
The presence of an expanding population of common carp, grass carp and silver carp is an ominous sign for the future aquatic habitat in the Preserve. The rapid removal of the submerged aquatic plant community through consumption by the grass carp, and decreased water clarity from algal blooms stimulated by the silver carp biomass may soon reach a critical tipping point. Then the reduced water clarity will likely allow the common carp to achieve very high reproduction and recruitment in the Preserve. A rapid degradation of the aquatic habitat, submerged aquatic plant community, and native fish population is the factual, proven result from a high common carp density.
Additional Lake Information: Public access to the water bodies on the Emiquon Preserve is limited to registered boats. Free annual registration to access the site for all users is required and available at the adjacent Dickson Mounds State Museum. Only electric trolling motors are allowed. No gas motors are allowed on the boats.
2 pole and line fishing only. A concrete boat ramp with a gravel parking lot for 25 vehicle/trailers is present and a boardwalk, visitor area and canoe launch.
The site contains an inviolate refuge from public access. This refuge will attempt to serve as a limited disturbance area for all of the wildlife utilizing the Preserve. This refuge encompasses approximately the eastern half of the former Thompson Lake basin, all of the former Flag Lake basin and then to the Illinois River levee. This refuge area is designated with marked buoys and signs. The access time to the water bodies is sunrise to sunset. This access is year round, except during the Central Zone waterfowl hunting season. During the Central Zone waterfowl hunting season, no water access is allowed on hunting days. Currently waterfowl is allowed 3 days a week, thereby allowing fishing access 4 days a week. Ice fishing is allowed when practical on the entire lake basin.
Site Regulations:
Largemouth Bass: 1 fish daily limit; 18" minimum length limit
Bluegill: 25 fish daily limit; no length limit
Channel Catfish: 6 fish daily limit; no length limit
Walleye, Sauger or Hybrid Walleye: 6 fish daily limit; 14" minimum length limit
White and Black Crappie: 25 fish daily limit; 9" minimum length limit
Contact Information: The Nature Conservancy Site Office 309-547-2730IDNR Fisheries Biologist, Rob Hilsabeck309-370-5296
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