But, coho biology is that they spawn high in a watershed and rear low. Seed from the top down and then be pushed downstream to the desired habitat. From which they smolt. So, it is natural and desireable, from the fish perspective, to bypass the hatchery and push on upstream as far as they can. The solution would be to rack the Hump and filter out the hatchery fish.
Or, alternatively, allow enough wild fish to spawn that they numerically overwhelm the hatchery fish.