I caught a pretty decent sized Cutbow out of a reservoir in SW Montana a few years back that was like that.....I was told that it was more than likely a genetic defect !!
Looks like a deformed fish, my friend and the NDOFF (national deformities of fish foundation) said its definately deformed... Id copy and paste a bunch of stuff but its just easier to say its deformed... 
Hmmm... there must be an echo in here.
The thing is if it was a stocked fish, no fish from a lot that tested positive for WD would be planted. Just doesn't happen no matter what someone tells you. And if the fish was hatched and reared in a concrete raceway system, or fiberglass circular tanks, which is 99 percent of state and federal hatcheries, the chance of it contracting WD are nil to none these days. The life cycle for the parasite that causes WD needs bottom mud as in an earthen pond. Even fish or eggs coming into the hatchery system have to be tested and come out negative for disease or parasites. My source for trout eggs in Utah even tests for mollusk larvae and copepods.
So yeah if it's a stocked fish it's either genetic or an injury at some point.
I can tell you the states and feds take the fish health testing standards very seriously and don't plant diseased fish. I was under the impression my state of Indiana planted IPN positive fish but apparently it was a false positive. A least that is what I was told.
