Illinois Fishing Size Limits: Slot Rules, Harvest Caps, and Penalties

Illinois fishing size limits work differently than in most states: there is no statewide minimum length for largemouth bass, smallmouth bass, spotted bass, channel catfish, crappie, or sunfish. The species that do carry a statewide minimum are muskellunge (36 inches), northern pike (24 inches), and walleye, sauger, and saugeye (14 inches). Most other length rules come from site-specific regulations set by the Illinois Department of Natural Resources for individual lakes and rivers, so the water you’re fishing matters as much as the fish on your line.

Statewide Minimum Lengths by Species

The 2026 Illinois Fishing Information guide, effective April 1, 2026 through March 31, 2027, sets these statewide rules:

Largemouth, smallmouth, and spotted bass: no statewide size limit.
Muskellunge and tiger muskie: 36-inch minimum total length.
Northern pike: 24-inch minimum total length, except on the Mississippi River, where there is no size limit.
Walleye, sauger, and saugeye: 14-inch minimum total length, except on the Mississippi and Wabash Rivers, where there is no size limit.
Striped bass, white bass, yellow bass, and hybrids: no size limit for fish under 17 inches; fish 17 inches or longer are subject to a daily limit of 3.
Channel, blue, and flathead catfish: no statewide size limit.
Crappie: no statewide size limit.
Bluegill, redear sunfish, and other sunfish: no statewide size limit.
Trout and salmon: no size limit.
Alligator gar: no size limit.
Lake sturgeon: fully protected, no possession allowed.

Every statewide rule listed here is subject to site-specific regulations, which can impose stricter limits on particular waters.¹

Site-Specific Rules and Slot Limits

The absence of a statewide minimum for bass, catfish, or crappie doesn’t mean you can keep anything you catch. Hundreds of individual water bodies carry their own length limits, slot limits, or harvest caps, and these are where most anglers actually run into size requirements.

A slot limit prohibits keeping fish within a specified length range, protecting breeding-size fish while allowing harvest above and below the slot. Aledo City Lake, for example, protects bass between 12 and 18 inches: you can keep bass under 12 inches or 18 inches and over, but nothing in between. Other waters set straightforward minimums. Altamont New City Reservoir requires a 15-inch minimum for bass with a 1-fish daily limit. Anderson Lake allows bass down to 12 inches.²

Muskellunge show how much site rules can tighten the statewide floor. The statewide minimum is 36 inches, but Evergreen Lake, the Fox Chain O’ Lakes, Kinkaid Lake, Lake Shelbyville, Otter Lake, and Pierce Lake all require 48 inches, and that stricter limit extends to the tailwaters below their dams.³ Check the site-specific listings for the exact water you plan to fish. The IDNR publishes the full list each year in the fishing digest at ifishillinois.org.

How to Measure a Fish in Illinois

Getting this wrong can turn a legal fish into a violation. Illinois measures total length: tip of the snout to the end of the tail, with the fish laid flat on a ruler, mouth closed, and tail lobes pressed together.¹ Pinching the tail matters, because a naturally fanned tail adds length that doesn’t count.

Two species are measured differently. Paddlefish are measured from the eye to the fork of the tail. Sturgeon are measured from the tip of the snout to the fork of the tail rather than the tail tip.²

A rigid measuring board gives the most accurate reading. Flexible tapes tend to follow the curve of the fish’s body and read slightly long. Lay the fish flat, close the mouth, pinch the tail lobes, and read the number. When the fish is borderline, the conservation officer’s measurement is the one that counts, and they won’t round up in your favor.

Daily Harvest Limits

Length rules and daily limits work together. Even where no minimum length applies, you still face a cap on how many fish you can keep.

Bass (largemouth, smallmouth, spotted): 6 per day in any combination. In most rivers and streams, no more than 3 may be smallmouth. From April 1 through June 15, smallmouth bass caught in rivers and streams must be released immediately, with exceptions for the Mississippi, Ohio, Wabash, and Illinois Rivers and certain Chicago-area waterways.
Muskellunge and tiger muskie: 1 per day.
Northern pike: 3 per day.
Striped bass, white bass, yellow bass, and hybrids 17 inches or longer: 3 per day in any combination.
Trout and salmon: 5 per day in any combination.
Alligator gar: 1 per 24 hours.

Channel catfish, crappie, bluegill, and other sunfish carry no statewide daily limit, but many individual lakes impose one. A lake might cap crappie at 10 per day with a 10-inch minimum even though the statewide rule imposes neither.¹ Check the site rules before you fill a stringer.

Penalties for Keeping an Undersized Fish

A standard fishing regulation violation, including keeping a fish below the applicable size limit, is classified as a petty offense.⁴ The fine can reach $1,000.⁵

On top of the fine, anyone convicted of unlawfully taking or possessing protected fish owes a civil penalty tied to the value of the fish. For game species such as bass, walleye, muskellunge, trout, and salmon, that value is $4 per pound or fraction of a pound, with a $4 minimum per fish. Catfish, crappie, bluegill, and similar species also carry a $4-per-pound civil penalty. Endangered or threatened species, including lake sturgeon and pallid sturgeon, carry a $150-per-animal penalty.⁶

Anyone who violates any provision of the Fish and Aquatic Life Code within five years of having a license revoked faces a Class A misdemeanor. Repeat offenders can also lose their fishing license and have equipment confiscated.⁴

Transporting fish taken in violation of Illinois law across state lines adds federal exposure under the Lacey Act. Civil penalties reach $10,000 per violation. Criminal charges can bring up to $20,000 in fines and five years in prison for knowing violations involving sales or imports, or up to $10,000 and one year for negligent violations.⁷

Releasing Undersized Fish So They Survive

How you release a short fish decides whether the size limit actually protects anything. A rushed, careful release preserves the fish; a botched one just moves the mortality out of sight.

The hardest call is a deeply swallowed hook. A study on bluegill found that trying to remove a hook lodged in the esophagus killed 44% of fish within 10 days, compared with 12.5% mortality when the line was cut close to the hook. About 71% of fish left with the hook in place expelled it on their own within 10 days.⁸ If the hook is deep, cut the line.

For hookups in the lip or jaw, standard removal is fine. Barbless hooks, or crimped barbs, cut handling time. Keep hands wet, avoid squeezing, and minimize air exposure. If you need to measure, lay the fish on a wet board, get the reading, and get it back in the water. The whole process should feel rushed. That’s the right tempo.

1
I Fish Illinois. 2026 Illinois Fishing Information
2
Illinois Department of Natural Resources. Illinois Fishing Information
3
Illinois Department of Natural Resources. Illinois Administrative Code Title 17 Section 810
4
Illinois General Assembly. Illinois Code 515 ILCS 5/20-35 – Offenses
5
Legal Information Institute. Illinois Administrative Code 17-805.50 – Penalties
6
Illinois General Assembly. Illinois Code 515 ILCS 5/5-25
7
Office of the Law Revision Counsel. United States Code Title 16 Section 3373 – Penalties and Sanctions
8
ScienceDirect. Cut the Line or Remove the Hook? An Evaluation of Sublethal and Lethal Endpoints for Deeply Hooked Bluegill