Hatchery fish are more likely to get diseases easier than wild fish in some people's opinion. There has been no strong evidence to prove this theory. But that because the hatchery fish live in closer living quarters disease spreads faster. However in the wild hatchery fish seem no more susceptible to disease than the wild fish. Having a hatchery with many fish in a small pond is an easy source for birds other predators to come in to eat the salmon.
Birds can stand on the cement separation blocks and scoop up the fish.
To help solve this problem the hatcheries have put up a series of wire along side the cement blocks to prevent the birds from getting the fish. Other hatcheries put nets around the whole rearing pond area to keep predators out. Salmon spend only six weeks in fresh water on their way down stream to the ocean. Salmon don't eat on their way upstream. Food is much more abundant in the ocean where salmon live most of their lives.