If these are hatchery fish, I would say the deformities are a result of a genetic mutation. It's possible they are a result of an injury but not likely. I've seen genetic mutations in young hatchery fish that look very similar.

I believe they're hatchery fish because, although genetic mutuations occur in the wild, fish with genetic mutations don't usually survive long enough to reach the adult stage. Unless, of course, the mutation results in increased fitness, thereby passing along the genes for better survival. Genetic selection at it's best. But this ain't one of those benefical mutations.....

Which brings up the question, why have these fish survived? It's likely they spent their first year or so in a hatchery. This allows inferior genes to persist when normally they would be eliminated quickly. A classic case of how hatcheries can, under some circumstances, reduce the fitness of wild salmon.

BTW - I've seen some very signficant genetic mutations in hatchery fish, including a fish that had two heads on one body. That fish was almost 8 inches long.