FishNDoc-
Unfortunately my computer skills are even more limited that Salmo's. However some of the authors that have written on survival of hatchery steelhead include: Leider et al. 1990, Blouin 2003, Kostow 2003, McLean et al. 2003, Hulett et al. 1996

For coho - Fleming and Gross 1993

For chinook - Reisenbichler and Rubin 1999

There are a number of ongoing studies as well as some literature comparing hatch and wild survivals for altantic salmon and anadromous brown trout.

The species interaction studies (several authors on the Yakima - (funded by BPA I think) would also likely have some information.

The short of it is that generally the longer the juvenile fish are held in the hatchery envirnoment (yearling smolts -steelhead, coho and chinook) the poor they perform in the wild. In addition the more generations a brood stock has been in the hatchery the poorer they do.

The poor survival is likely due primarily to the domesitication of the fish - that is the hatchey envirnoment selects for different behaviors than a free flowing river. The degree that the returning hatchery fish's spawn timing, behavior, run timing etc is out of sync with that exhibited by the wild fish also play a role in their survival.

To minimize negative effects of natural spawning hatchery fish on the wild populations the best bet is to catch the heck out of the hatchery fish. Two other general statregies have been commonly used. The first typcialified by the early Chamber's Creek fish is to have a large temporal and spacial separation in the spawning of the two populations. In the North Sound area the temporal separation of the two winter stocks is nearly 100%. The other is use native brood stock and to try to selective the brood stock so the smolts produced are representative of the wild population they came from - with prolong spawning and run timing that can be difficult. Any selection that occurs in the wild brood stock will likely result in a hatchery fish that is somewhat different that the wild population however there will be significant spacial and temporal spawning between the two populations.

Each of the hatchery programs present differrent harvest management problems as well. Which is better if any is likely best determined on a case by case basis.

Tight lines
Smalma