Mishandling by previous angler(s) is the more likely reason. Anglers grabbing it, dropping it, dragging it causes damage the fishes protective slime leading to fungus then open sores/infections. The cold may slow down the infection but by summer, it'll be a dead fish more than likley. Anglers love to catch them but show little mercy when it comes to handling/releasing them. I particularly like the pictures of fish laying on the bank covered in sand or lying across laps. That's really good for them
If not for the state stocking them every year, we'd have very few left due to poor handling. Nobody is eating them so no need to haul them into your boat or onto shore. Clip down your barbs, keep them in the water and use pliers to release them. A money shot is okay but do it quick. If you lose it or it escapes, so what, its not like your losing a pic worth any money. If you enjoy this great fishery the state has created, then fishes safety SHOULD come first above all else. I was guilty of the mishandling at first in my eagerness to get pictures but came to realize i don't need photos of every damn fish.
