Montana Fish, Wildlife & Parks wants to hear from the public on a slate of proposals aimed at helping ailing brown trout populations in southwest Montana. Biologists have documented steep brown trout population drops in recent years across multiple rivers. In the Big Hole Riverâs most popular section near Melrose, numbers of brown trout dipped from 1,800 fish per mile to 400. The Ruby has dropped from 1,500 brown trout per mile to 600-700 in the upper tail waters. The 2,000 fish per mile in the Beaverhead are now down to 1,000, the Montana Standard reported, with similar stories in the Jefferson and Clark Fork rivers.