It is an argument for removing dams as well.
For many years biologists have known that hatchery fish effect the fitness of wild fish through competition and interbreeding. Hatchery fish don’t have the selective pressures that wild fish do so are less fit to survive in the wild. Because of this, when hatchery fish breed with wild fish the progeny are less suited to survive in the wild affecting the overall survival of wild fish.
Hatchery fish are also larger and more aggressive than wild fish and compete with them for food further limiting the success of wild fish. Being more aggressive makes hatchery fish more vulnerable to predators, a trait that you don’t want to transfer to wild fish. Hatchery fish also stray more so they can interbreed with runs which are managed to be exclusively wild such as the Middle Fork of the Salmon River.
In the case of steelhead, hatchery fish virtually flood the habitat with stray fish, a situation that almost ensures that hatchery fish will interbreed with wild fish in places where it is not intended.
I think the report mentioned is more of an argument for removing dams than it is for reducing hatchery production because, due to the impacts of lower numbers of fish in the short term like economic and biological impacts, you can’t reduce hatchery production without increasing the success of wild fish reproduction. The only way to increase wild fish production to such a degree will be to remove dams.
Federal biologists say that cutting hatchery production could help protect wild salmon
By Scott Learn, The Oregonian