I suppose I should digress on this a bit.
Think about the evolution of salmonids. They all originated as fresh water species, basically trout. Because they were successful, almost too successful, the populations grew to a size where they started running out of food. Competition within the species would result in some individuals hogging all the food. Those fish would dominate the fresh water environment. The less successful individuals would be forced to move in to brackish, estuarial waters in order to access the (much larger) food supply in the ocean. Those that adapted to the salt conditions grew fat but, because of their fresh water origins, couldn't spawn in the ocean and had to return to the rivers and lakes to spawn. They were much bigger then the 'residuals' and dominated the spawning grounds.
Sometimes they would get lost and spawn in the cold, low-productivity rivers that wouldn't normally be able to support a year-round trout population. Because there was no competition for spawning grounds or fry rearing territory, they all grew into fry. They might stay for the summer, but winter would force them to the ocean to find food and survive. This is why some steelhead rivers have no residual rainbows, or in the case of sockeye, no kokanee.
Bottom line is this: more productive environments, like a hatchery, encourage residualization. It's not a problem because they are accessing different food supplies and the larger anadromous versions dominate the spawning grounds.