Some say that hatchery born fish will not successfully reproduce in the wild, or studies show their reproduction success rate is very low. At least we all hope that is true.

As stated in the prior post, adaptations take thousands of years. Examples include disease resistance. Example: A fish native to a river sytem and it's ancestors may have become "immune" to a disease that occurs every fifty or so years. Whereas the Skamania strain steelhead that was "accidentaly" born in the wild now returning to the Nooksack comes upon the "fifty year virus" and does not have the immunity that the "native fish's family have developed over thousands of years.

The recent issue of STS clarifies some terminology
wild fish: as a fish that was born in a river system not a hatchery. May have originated from another river system
Native fish: Originated in a specific river system, born in the wild
I have always thought of wild fish as native, but this isn't so.

If your interested in learning more on the subject, "salmon without rivers" by Jim Lichatowich is an excellent explanation of hatcheries, native fish, and salmon history.