RPetzold:
I think it's an interesting idea and as long as the lit search is conducted in an unbiased manner it may provide interesting information. At the least it will be a good learning experience.
This brings up some good questions: at what degree of hybridization do you call a stock extinct? How valid is the idea of stock recovery through the protection of hybrids? How would you determine a native with all of the intermixing that has already occurred?
Also, what would be the fallout if wild upper Columbia River steelhead were declared extinct? Would this put more pressure on NMFS to move on Snake river fish?
Just some ideas. Sorry I can't give you any sources right now. Good luck!