The most recent statements of the National Marine Fisheries Service, and the statements of other salmon advocates, suggest that the goal of salmon recovery may be fifty years away, and we may never succeed. Growing salmon does takes longer than growing corn, or rabbits, or even cattle, but not longer than growing trees. Recovering salmon will be like any agricultural enterprise. Its success will depend on the vagaries of the weather. It will depend on luck with the salmon stocks we choose to introduce.
Some transplants work, like the salmon in New Zealand.
If nature cooperates, every major river in the Pacific Northwest could be running with salmon. We have the hatcheries to do it, if we can focus on making them work before we dismantle them. But if the climate gets warmer and warmer, it's just no realistic to expect to maintain large populations of cold-water fish. It is surely true that what would be best for salmon would be a Pacific Northwest without humanity at all. So far, the best has been the enemy of the good, with those pursuing the best destroying the good and achieving nothing.