Illinois River - Alton Pool

Flathead Catfish

Very Good

Flathead Catfish are common in the Alton Pool and trophy-sized fish exceeding 36 inches and 30 pounds can be found. The 2024 Alton Pool survey resulted in the highest Flathead Catfish catch rate out of all pools in 2024 and the highest catch rate over the last 10 years in the Alton Pool with 8 fish/hr electrofishing. 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

White Bass

Good

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 numbers can be cyclic, because they require a degree of flowing water for spawning success. White Bass numbers have been on the low cycle, but rebounded in 2024, likely due to spring flooding. Thirty-one White Bass/hour measuring 3 - 16 inches weighing up to 1.8 pounds were collected in the 2024 Alton Pool survey.

Largemouth Bass

Good

Largemouth Bass can be found throughout the Alton Pool and, like other members of the sunfish family, have reproductive spikes during big flood years. The Alton Pool has experienced multiple low water years in recent years that can reduce spawning success for Largemouth Bass due to lack of suitable spawning and nursery habitat availability that can affect year class strength. Catch rates were average for the Alton Pool in the 2024 fish community survey (5/hour) and lowest out of all pools. Backwaters, side channels and shallow water with structure are the places to fish for river bass.

Sauger

Average

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. The 2024 survey resulted in only 1 Sauger/hour electrofishing and no walleye.

Crappie spp.

Excellent

The 2024 fish community survey resulted in an above average crappie collections. Black and white crappie ranged in size 2–13 inches with a strong year class 6–7 inches. Year class strength of crappie increases with the occurrence of spring flood events. Backwaters, side channels and main channel border areas with submerged brush are the best locations for crappie fishing.

Striped Bass x White Bass (Wiper)

Good

IDNR Biologists have been receiving an increase in calls from anglers catching hybrid striped bass (white bass x striped bass). In 2024 we collected 3 fish/hr each of hybrid striped bass and pure striped bass. There is no creel limit on white, striped, or hybrid striped bass measuring less than 17 inches, however white, striped, or hybrid striped bass measuring 17 inches or greater have a 3 fish/day creel limit on the Illinois River.

Channel Catfish

Excellent

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 2024 fish community survey resulted in a catch rate of 10 Channel Catfish/hour electrofishing in the Alton Pool ranging from 14–25 inches and weighing up to 6.7 lbs. The catch rate of Channel Catfish in 2024 was about average over the last 10 years. A spring hoop net survey was not conducted in 2024 due to high water levels and is rescheduled for 2025. 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.

Blue Catfish

Excellent

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 2024. 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.”