Restoring Nutrients in Salmonid Ecosystems, and AFS book, would be a place to start if you are looking for published results.

The most recent Pacific Coast Steelhead Management Meeting website as abstracts and PowerPoints that show ongoing studies/data.

Northwest Science has some papers from the mid 90s by Michael, i believe, that show direct benefit of increased escapments of thos fish that deliver nutrients.

There have been a series of papers in Fisheries (AFS's monthly magazine) dealing with the question.

The recent AFS book on Modeling Salmonid Ecosystems touches on the question and how to model it.

The AFS book on Diadromous Fishes has one of the best summaries of how salmonid delivered nutrients drive the whole ecosystem; not just fish.

And, there is a lot of stuff in the "almost submitted" and "still collecting data but can you believ what this shows" out there.