But since our hatchery is going to operate for more than just one generation, we need to cull out another 50 pair of wild fish for broodstock. So in that next generation, total production would be as follows:
(and yes Curt and Steve, I realize that I'm simplifying here because the fish actually come back in staggered age classes which makes the real analysis much more complicated, but regardless this exercise is still instructive)
the 100 wild broodstock fish brought into the hatchery would bring back 200, the 200 hatchery fish spawning on the gravel would bring back 136, and
the remaining 220 wild natural spawners would bring back 176.
Total production from that second generation would be 512 fish... in other words the fish just replace themselves.
OK... I made an error there. That second generation of hatchery production does NOT break even. That second run thru the hatchery actually results in a net loss 8 fish or 1.5 % of the 520 fish it started with.
For clarity, my hypothetical scenario actually shows how the "conservation" hatchery is no longer self-sustaining as early as the second generation of fish.
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