If you fish the Mississippi River between MO and IL here are the catfish creel limits.
Mississippi River (between IL & MO)
Illinois waters (Multiple Counties)
All fishermen shall conform with the regulations of the state in which
they are fishing unless the regulations of the fishermen’s licensing
state are more restrictive, then the fishermen must conform with the
more restrictive regulations.
Channel or Blue Catfish (14) . . . 20 Fish Daily Creel Limit
All Nongame Species Combined — 100 Fish Daily Creel Limit
(Excludes endangered and threatened species and the following
game species: Crappie, Channel/Blue/Flathead Catfish, Rock
Bass, Warmouth, White/Yellow/Striped/Hybrid Striped Bass, Trout,
Largemouth/Smallmouth/Spotted Bass, Muskellunge,Northern
14) Daily catch limit includes all fish species (either singly or in the
aggregate) caught within each of the following fish groupings.
1) Largemouth or Smallmouth Bass
2) Walleye, Sauger, or their hybrid
3) Bluegill, Redear Sunfish, or Pumpkinseed
Right now, we're in a wait-and-see situation in IL. We haven't collected regular creel surveys for some time as I understand, so until there's documentation of significant harvest we're unlikely to see any statewide regulations.
In the past (more than 15-20 years ago) , there was little info about the population of fish. Presently, the standard DNR position has been naturally reproducing populations don't need protection. Except where required based on agreements between neighboring states, only site specific limits apply (typically where a stocked catfish population exists - "put and take" catfisheries).
I think many recreational anglers would like to see some statewide restrictions on harvest, at least of flatheads, and possible other cats based on size. But, we probably won't get any traction with ILDNR on this until there's more data to support the necessity of this. Don't forget, enforecement is a huge issue as far as their being a shortage of officers who could write people up anyhow. So in essence we're on the honor system at the present time.