The impact on the trout from having salmon fishermen around (if they are not using bait) is probably minimal compared to the effect of the increased numbers of fishermen on the local trout anglers. Some of them probably do not appreciate the gear tossers in such a pretty streach of trout water. It would bug me also, but that's how it goes.

As for being the only river that produces trout over 20" with any kind of regularity? Well, that's not exactly true. It has the most fishermen out of WA's collection of great trout streams, but there are several other places I can think of off the top of my head that are less crowded (because they are much less accessible) that will produce may fish in the 20" class and can on a very good day, produce hundreds of fish in the 10-15" range.

I think a well managed (often an oxymoron in this state) salmon fishery could be great. Maybe a few kids could tie into a king and begin a love of sportfishing they would keep for the rest of their lives. The fish need all the friends that they can get :P