Without going into the many details, as Smalma can run more off the top of his head than I could come up with in an hour, I'll just say this:

Planting more smolts does not automatically mean more adults will return...in some instances, once you get to a certain level of planting, the reverse is true, e.g., the Skagit River.

Quality of brood, quality of smolt, quality of water (fresh and salt), quality of habitat (fresh and salt), harvest pressures, and competitive pressures between themselves, their wild cousins, and the multitudes of wild and hatchery salmon, not to mention resident fish and predators...all of these are relevant factors that control the plant/adult ratio, and all of them are different for every stream.

Fish on...

Todd