I had a nice morning on the South Branch. I was fishing a pool and caught 3 Rainbows. One was a nice size trout for the South Branch. I observed the Trout had the nastiest looking mouth. It was all black. My question is: was the Trout's black mouth as a result of what it was eating? If so what was the Trout eating to cause such a nasty black mouth. It looked like an otherwise healthy fish. It put up a nice fight. I caught the Trout on a nymph. Great fall morning of fishing. I am curious.