Grandpa -
interesting question.

Clearly hatchery fish have successfully established self-sustaining populations; however in most cases it has been in cases like that in the Cedar. The hatchery fish are introduced for one or more years and then the releases discontinued the natural selection process will proceed allowing each new generation to become more adapted to the environment. As I recall it took several decades for the sockeye in the Cedar to become very productive in their new environment. This is not unlike the process of colonization and re-colonization of habitats by wild fish that has been going on for 10,000s of years.

This is different from what we commonly think of hatchery and wild fish interacting in the wild. As most know the rearing of salmonids in a hatchery environment results in "domestication" of the fish. Thus hatchery fish tend to be less productive when spawning in the wild than naturally produced fish (whether hatchery or wild). The annual input of hatchery fish in the natural population continues this loss of productivity. Of course if the hatchery releases were to stop the offspring of this last generation would have the chance to adapt through the natural selection process and may become productive "wild' fish.

Tight lines
Smalma