I don't know but it is not just staging but pass-through. It could/should be answered by tagging studies or possibly genetic studies. WDF did a lot way back that could be consulted if there is nothing more recent.

Besides, with Skagit and Stilly so low why take any when you can get the Snoho fish in the Snoho? Why put additional unnecessary pressure on depressed stocks when better alternatives (stock-wise) exist?

To use the economic argument would probably say that taking WA Chinook and coho in BC and AK is economically a better idea because more money is spent per fish. Gotta maximize the economic return.