I agree with Eric, either method is not 100 percent. I've caught fish after fish after fish on bait, all hooked in the jaw; and I've hooked fish on pink worms that were really deep. I can't recall to many winter hatchery brats ever to have have swallowed my bait; although a few summer brats have. I'm sure some of the natives I've caught would have swallowed bait (by the intense pick-up), but all of the native fisheries I fish are baitless/barbless.

And if you're in smolt infested waters, you usually either give up using bait or run out before you do much damage.

Because of this, I would think a bait ban would be necessary only on native fisheries, just to make sure you're on the lower end of average as far as hooking mortality goes. I would also think a bait ban would be useful during periods of downstream smolt migration.