Swift - So where would the unclipped parent come from?

From the wild stock, obviously. Which means fishery managers would be "mining" the wild stock to supplement the hatchery stock. Could be fine if the wild stock is healthy, is spawning successfully, and may have "excess" adults. But if not, the practice of mining the wild fish just to prop up the hatchery is a major reason some wild stocks are no longer with us, particularly on the OP. That practice becomes part of the problem, not the cure.