I doubt much that there's any stocking unless it is "native" species. The Montana FWP has gone completely Aryan, in favor of purebred Nordic fish. Whether they are catchable is secondary to "native" genetics uber alles.
That's too bad. Back in the day, they planted fish in lakes whose features inhibited natural reproduction. I have caught brookies, cutthroats, goldens, rainbows, cut-bows and grayling in the Beartooths, back when I was able to carry a 65 pound pack through hip-deep snow to get to a lake just as the ice began to melt at the sunny edge. Last time I was there, about 15 years ago, they had turned the west fork rock creek into catch and release only. I have released most of the fish I ever caught up there, but I do like to have the occasional fish supper to add a little fresh protein to the backpacking menu.