You were correct in releasing that fish even though it was a hatchery fish! I have caught a few of them like that this year! I was told that these are hatchery fish(ventral clips) that were release as smolts in the upper watershed and then trucked around the dam(s) when they were ready to outmigrate. They are using the numbers of the returning adults to the hatchery to see how the survival of these fish is!