Rainbow trout - unidentified injury/disease

[goodfishin]

Hit up a lake that has been good to me the last couple years yesterday and hooked into a few nice stockie rainbows.

The nicest of the bunch was about as good as you're going to get of the regular ol' stocked variety. Nice and chunky, good fight.

Had dreams of throwing him on the grill right up until I got him in the net and saw the big lesion on his side. Not sure what the cause of it was but my guess is an injury that got infected. Could be a disease though.

Anybody have a guess at what the poor guy's ailment was?