I believe that the somewhat simple answer is that it will allow significant increases in artificial production. As an example, the lower Columbia Chinook are/were in such bad shape that hatchery releases had to be almost eliminated to allow for "recovery" of naturally spawning fish. As has been noted in PS, the decades since listing have not resulted in improvements in the wild fish. The argument can thus be made that actual recovery is , in many cases, impossible to achieve. We can debate the reasons (habitat, climate change, overfishing, your choice) but the rusult is that we, as a society, don't want to accept the cost of meaningful wild recovery and the constraints on development that leads to. So, if we are going to have fisheries where we kill fish, then we gotta grow them in hatcheries.