FNP,
I greatly admire your energy to run the calcs. Two other variables that should be included come to mind, and there are no doubt others. First, although the returning hatchery fish that spawn in the wild have reduced fitness, each subsequent generation from them that remains in the natural environment improves in fitness. At least that is the present theory. And it's probably true, given that natural runs have resulted from hatchery stocks in the past, fortunately before we knew so much about their reduced fitness (t.i.c.). Second, with each passing generation of chinook, the habitat suitability improves slightly in productivity. It's not a specific steady trend line, as backsliding occurs, only to be followed by several years of higher quality conditions, etc. We have seen this on Deer Ck, the NF Stilly tributary that hosts the native summer steelhead. But for this habitat phenomenon, native Stilly summer runs might be a thing of the past as well.
Francis, your analysis could well be the most accurate portrayal of the final outcome. However, pulling the plug eliminates future options. The "conservation" program preserves options, even if only for a while. Given that choice, what would you do? If these chinook were your "family" for instance?
Sg