Snagging is the only way to catch them. They don't take bait; they're filter-feeders. It's legal in OK year-round, except in a few areas where they are protected.
I've tangled with several of them. Usually the jig I was using would just slip off/out after about 60 seconds. I hooked into one accidentally a couple years ago. It about pulled me into the river, when it made a downstream run. I could either tighten my drag down, and get pulled downstream, or loosen my drag up a bit and try to fight it. Ended up chasing it downriver, where the fish wrapped around a rock. Had to pop 40 lbs test line, which isn't easy.
I actually did manage to hook one in the mouth many, many, years ago. I was fishing cut bait under a float for catfish, using a circle hook. All I noticed was that suddenly, my float started moving in an odd direction. I immediately came tight to the fish and started trying to bring it in, which is when all heck broke loose

I guess it was swimming along, mouth open, trying to feed, and just happened to engulf my bait and hook. As it swam away from me, the circle hook did what it was supposed to do and hooked the fish in the corner of the mouth. Still would be considered a snag.