There's a fair bit of fascinating stuff on the internet about the hundreds of deformed frogs found in Minnesota and Quebec (and elsewhere), mostly in ponds on agricultural lands. Frogs, as you may have heard, are considered "sentinel species;" because of their porous bodies -- they usually take water in directly through the skin, without having to drink -- and their complex life cycles, they make a good index of environmental degradation. It seems bizarre, but no-one has been able to prove that these sorts of deformities are caused by pesticides and other agricultural chemicals, though it's ones immediate assumption.
Disturbing to hear, anyhow, that similar things are being found in trout. Even though it's an isolated case, I wouldn't eat a fish like this.