Illinois - Alton Pool
Location: The Alton Pool extends upstream 80.2 miles from Grafton to the tailwater of the La Grange Lock and Dam, north of Meredosia. Although the lower Illinois River reach is not impounded, it is termed the Alton Pool because it is to some degree influenced by the Mel Price Lock and Dam on the Mississippi River at Alton.
Description: The Illinois River is formed at the confluence of the Des Plaines and Kankakee rivers near Channahon in northeastern Illinois. It flows southwest for 273 miles across the state to enter the Mississippi River at Grafton. There are five dams along the Illinois forming pooled reaches named (upstream to downstream) the Dresden, Marseilles, Starved Rock, Peoria and La Grange pools. The lower Illinois reach is the Alton Pool.
Status of the Sport Fishery: Historically the lower Illinois River was one of the most productive freshwater fisheries in the world, but over the last century the structure and function of the Illinois River and its floodplain have been greatly altered. Diversion of water from Lake Michigan into the Illinois River, levee construction and isolation of the floodplain, changes in land use and construction of locks and dams has resulted in aquatic habitat degradation. Additionally, Asian carp have invaded the river and now comprise about half of the biomass of our electrofishing samples in the lower river. A total of 65 native fish species were collected by electrofishing in the Illinois River in 2022 and excellent sport fishing opportunities remain in the Alton Pool.
River Access: The Alton Pool is typically characterized by slow water velocities and soft substrates of silt and sand. There are a number of islands and associated side channels in the reach. One notable side channel is Dark Chute, with a boat ramp available at the Godar-Diamond Island Complex along Route 100 north of Hardin. Cross the river to the mouth of Macoupin Creek for good fishing opportunities as well. About 10 miles to the south, Helmbold and 12 Mile islands are accessible by a ramp at The Glades Management Area west of Rosedale. The area between Grafton and Nutwood has many backwater lakes that provide good sunfish and bass fishing opportunities. The Stump Lake Fish and Wildlife Area boat ramp just north of Pere Marquette State Park provides access to Flat, Long, Fowler and Upper Stump lakes. The Stump Lake complex provides excellent bluegill, crappie and bullhead fishing. Boat ramps at Grafton and Pere Marquette State Park provide access to the lower Illinois River. The northern half of the Alton Pool has a number of good fishing sites with easy access as well. Big Blue Island located between I72 and Route 100 is accessible by boat with a ramp just southwest of the Route 100 Bridge near Florence. Naples and Meredosia both have public ramps on the river. There is a ramp upstream of the La Grange Lock and Dam, but access to the tailwater requires locking through. The run from the Meredosia ramp to the La Grange tailwater is about 9 miles, but worth the trip. The swift currents below the dam add a diversity of habitat conditions, which provides excellent white bass fishing, along with concentrations of sauger, largemouth and smallmouth bass and catfish. Public access areas are typically good areas for bank fishing as well. There are numerous bank fishing areas in the Mississippi River Fish and Wildlife Area.
Additional Information: There is a 12 inch minimum length limit for largemouth and smallmouth bass. The daily creel limit is six bass total with no more than three smallmouth bass. The minimum length limit for walleye, sauger and their hybrids is 14 inches, with a six fish daily creel limit. White bass, striped bass and their hybrids have no daily creel limit under 17 inches. The daily creel limit of white bass, striped bass and their hybrids measuring 17 inches or longer is three total. Waterfowl management areas may be closed to fishing as posted at the site. For specifics on restrictions and for information on bank fishing access, contact the Mississippi River Area office (618) 376-3303.
Contact Information: Mississippi River Area Office 618-376-3303
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The blue catfish population is on the rise in the lower Illinois River and, like flatheads, they also reach trophy sizes. No blue catfish were collected in 2022. Two previous world record blue catfish (at 124 and 130 pounds each) were caught just a few miles downstream of the Illinois River mouth. Fish the deep holes and main channel border near structure from Pearl down to Grafton for “blue skins”.
Channel catfish are the primary game fish of the Alton Pool and are very abundant throughout the reach. Notable areas for channel catfish are main channel border and side channels with current and structure. The 2022 fish community survey resulted in a catch rate of 8 channel catfish/hour electrofishing in the Alton Pool ranging from 1-20 inches. The catch rate of channel catfish in 2022 is low, but a poor survey year is not concerning as survey success can be affected by many biotic and abiotic factors. There remains a one-meal-per-week contaminant advisory on channel catfish over 16 inches in the lower Illinois River due to low level PCB detection in the flesh. PCB contamination in fish is a remnant of past pollution that is declining. Trim the fat, particularly around the belly, and allow fat to drip off the fish when cooking to minimize exposure to PCBs.
The 2022 fish community survey resulted in only 18 crappie ranging from 5 – 11 inches. While the 2022 survey produced low numbers of crappie, the higher occurrence of spring flooding has benefitted all sunfish species in the Alton Pool. Backwaters, side channels and main channel border areas with submerged brush are the best locations for crappie fishing.
Flathead catfish are common in the Alton Pool and trophy-sized fish exceeding 36 inches and 30 pounds can be found. The 2022 fish community survey resulted in a poor flathead catfish survey. Spring hoop net surveys can produce higher catch rates of catfish. Spring hoop net surveys are planned for 2023. Fish the deep holes, main channel border near current breaks, and woody debris piles or other structure. Specifically, the mouth of Macoupin Creek and nearby Dark Chute at Diamond Island and the La Grange tailwater offer great opportunities for catching flatheads.
IDNR Biologists have been receiving an increase in calls from anglers catching hybrid striped bass (white bass x striped bass). There is no creel limit on white or hybrid striped bass measuring less than 17 inches, however white or hybrid striped bass measuring 17 inches or greater have a 3 fish/day creel limit on the Illinois River.
Largemouth bass are prevalent throughout the Alton Pool and, like other members of the sunfish family, they have reproductive spikes during big flood years. While catch rates were low in the 2022 fish community survey, largemouth bass density has been increasing over the last ten years in the Alton Pool. An increase in largemouth bass density is attributed to high water years that allow for an increase in spawning habitat availability. Backwaters, side channels and shallow water with structure are the places to fish for river bass.
Catchable sauger and, to a lesser degree, walleye, are most abundant in the upper pools of the Illinois River, but do inhabit the Alton Pool. Sauger are found in deep waters during the day, but search for food in the shallows of the main channel border at night. Their feeding habits result in poor day-time electrofishing catches.
White bass, the most prevalent of the three temperate bass species found in the Illinois River, is a schooling species that is present throughout the main channel of the Alton Pool. White bass are a short-lived and fast-growing species that provide excellent sport fishing opportunities during the early spring spawning runs or mid-summer feeding frenzies of gizzard shad. White bass measuring up to 14 inches were collected in the 2022 Alton Pool survey and showed the highest catch rate out of all pools in 2022. White bass catch rates have been increasing in the Alton Pool over the last 10 years.