The article in the link refers to a specific case on Oregon's Clackamas River. The hatchery summer steelhead don't impact wild winter steelhead in the upper Clackamas for a very simple physical, not genetic, reason. The wild winter steelhead are passed upstream of the dam to migrate and spawn naturally. The hatchery summer steelhead are stopped at the dam and prevented from migrating and spawning in the upper river. The summer runs that are not caught in the recreational fishery may in fact spawn in the river downstream of the dam. And that spawning activity might have a negative impact on wild steelhead that spawn downstream of the dam. But we don't know because the effects of hatchery steelhead on wild steelhead downstream of the dam were not studied.

It's important to read information and analyze it carefully. What this study tells us is that we can have successful hatchery and wild steelhead programs when the two stocks are kept separated from spawning in the same area. It doesn't tell us a thing about whether the hatchery and wild populations can co-exist in the same habitat at the same time without any ill effects to either population. That is a related, but distinctly different, subject. And that relates directly to the hatchery summer steelhead programs on the Sky and Green Rivers (and Stillaguamish).