Steeliematt, the numbers I'm quoting are just general for comparison purposes between average survival of wild fish to smolt size vs. hatchery fish, again, generally in a hatchery 90% of eggs taken survive to smolt, whereas in the wild it's closer to 10%. These figures come from a compilation of Columbia tributary studies, many of which are in Oregon, but again are just general. And I did at one time manage the release/recapture facility of the largest coho hatchery in the world, that would be OreAqua with releases exceeding 20 million smolts, and have more than enough experience with fish culture, and fish genetics, than most.

Cowfish, that works every time you open up a new hatchery, and also almost every time you outplant a system with a different stock. The cause of this phenomenon has not been studied, but I would guess it relates to predator abundance - it probably takes a year or two for the predators to identify and adapt to preying upon new runs of fish. It probably also relates to disease and parasites, both of which take time to catch up with newly-established runs. Again, relating this to Oreaqua, at the peak of our operation there were over 20,000 common murres counted at the entrance to Yaquina Bay, and after we shut down that number declined to less than a thousand. Predators adapt to increases and decreases in prey - the predator/prey cycle is Biology 101 stuff but is about as valid as any science that has been brought to bear on this subject.