For one year of adult returns on the Hoh there were age-2 and age-3 hatchery smolts that returned as adults. It looks like they were released as age-1 and hung around for a year or two before smolting. I know that a long time ago WDG was concerned about steelhead smolts residualizing but I think they only looked at if they stayed post-release and not if they finally smolted.