A similar mechanism has given rise to the presence of mini-jack salmon. Those are hatchery Chinook salmon smolts that mature to adults, but never leave the Columbia River. They spend their life in the reservoirs behind the dams, and return as mature adults but are only 8 inches long. Not much different than resident rainbows, except they're salmon.

PIT tag data has indicated that mini-jacks are much, much more common than anyone previously realized. They don't often return to the hatcheries because they're too small to go up the fish ladders, so they spawn in the tribs wherever they can, usually with wild fish. They are only found by surveying the spawning grounds with PIT tag detection equipment. Invariably, mini-jacks are hatchery fish.