MM, the fundamental difference is that there are far fewer wild fish now than before we had hatcheries. Nature was in balance, predator and prey. Since the predator base has increased (as you point out) and the wild fish have decreased, the effects of barging the hatchery fish would be devastating to the wild run.
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"You're not a g*dda*n looney Martini, you're a fisherman"

R.P. McMurphy - One Flew Over The Cuckoo's Nest