For those transboundary rivers, if the adults make it to Canada and lay their eggs, the smolts will be migrating downstream. Some of them will move up into, for instance, those small side tributaries that may have barriers. Chinook salmon will do that, in order to overwinter in those side tributaries. There would be some benefits in that case, but not all salmon species have that behaviour.
On November 25th, 2024. See this statement in context.