The US/Canada treaty had (still might) a provision that the benefits of habitat improvement accrue to the folks doing the improvement. So, if WA actually removes culverts the benefits accrue to WA.

AK made the argument (Jeff Koenings, I believe) that since they are protecting the ocean up there they get the benefit of those fish. This was in response to Canada suggesting that if they (BC) improved habitat the catch would accrue in BC.

AK shares with nobody. So BC hits the lower 48.