Fish including catfish in water bodies draining off of areas like national forests, and so on, can be VERY good table fare (assuming one does not have a dietary problem), and, under 8 lbs. or so, low in contaminants.
The lake I mentioned several posts earlier, Devils Kitchen Lake, in S. IL, is quite “clean”, but does have some mercury contamination from natural sources — basically, exposed rocks. At my age, mercury unless really high in level is not much of a concern, and in the panfish it’s pretty low anyway, even @ DKL, so wifey liking the 8” bluegill works out well.
At DKL, I’d probably release catfish over 5 lbs. or so anyway, as the lake arguably could use a few more large predators - most of the bass over 14” or so get fished out, it appears. There are good numbers of small bass, 12” or so — arguably the lake could use a slot limit (no harvest of bass between 14” and 18”, perhaps. However, that might dent the trout population...
I don’t fish the rivers much for the reason you state. Luckily, we have quite a few lakes and ponds in areas that don’t get much if any nasty runoff. :-)
Removed from THE Illinois river, not AN Illinois river! I imagine you could make a lot of fish emulsion fertilizer from 50 million pounds of Carp! (Easier than the 1 fish one corn plant Squanto method!)
I last fished in the 1990s on a fishing charters out of Egg Harbor on Green bay. There were 7 passengers. One person caught a salmon. The rest of us bobbed around for 2 hours and got sunburned. Oh well.