Jay Nicholas posted his response to this question recently on his Blog, Fishingwithjay.wordpress.com. You can view it if your curiosity is piqued, if you have an opinion one way or the other, or if you just want to see some of salmon art.
http://fishingwithjay.wordpress.com/category/salmon-conservation-issues/
CD
Excellent explanation. Also a clear illustration of how confusing this issue can be. So much easier to ignore facts and fall back to the pro-hatchery line “there’s no such thing as a wild fish!”