A private hatchery is one that raises fish for profit. A subgroup is the commercial net pens.

The problems (weakness) caused in hatchery fish tend to be genetic and tend to be lethal in the wild. They "overcome" the weakness by dieing. Probably the worst was some Chamber Creek winter steelhead that spawned in the wild and produced no smolts.

The overall problem with taking fish into hatcheries is that many of the changes are genetic; the fish genetically adapt to the hatchery. Unless the hatchery environment is EXACTLY the same as the wild in terms of temperature, flow velocity, available habitats (pool/riffle/run), unless the foods are the same and arrive the same way (in the water column, not all on the surface) and so on the fish will be changed. Some of the changes, which are "learned", can be overcome. The genetic ones tend to kill.