AS have a longer history of culture and more selective breeding. Imagine the outrage if you cultured Pacifics. First, they would genetically swamp the wild fish when they escaped. And, being the same species, would be way more likely to at least successfully mate. Say 2 AS's spawn and produce zip. Nothing lost. A cultured Chinook spawns with a wild Chinook. Still produces zip but one wild spawner is wasted. If they don't produce zip you get maladapted genes out there until natural selection removes them. Which again wastes wild fish. Who is going to surrender Pacific's for a private broodstock?