The problem with those northern interceptions is that you are dealing with two more countries. Alaska is the Big Dog, politically. Plus, nobody catches their fish. The lower 48 and Canada have no hammers to compel a change.

Now, Canada takes Lower 48 fish, and we take theirs. Wilkerson, in the first US-Canada treaty (80s) allowed their take of coho to numerically match the expected US share of Fraser sockeye. If we want Canada off "our" fish, we just need to stay off theirs. That would still leave Canada in a pissing match with AK because they take Canadian fish up north. As I recall, Canada was hoping that the other 49 states would exert some control on AK.