Originally Posted By: Salmo g.
1).The article in the link refers to a specific case on Oregon's Clackamas River.

2. 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.

3 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).


I have tried to key my thoughts to the 3 points selected from Salmo g.'s post that I have partially quoted above:

1. I agree with Salmo g. here. This is a specific case where most of the fish from the hatchery program were separated from the natural winter population either by removal at the dam or because most of the summer steelhead hatchery smolts were released in lower portions of the mainstem. Quoting from the report: Separation in spawn timing and location may explain why the presence of large numbers of summer steelhead did not reduce the productivity of adult winter steelhead...Additionally, releases of summer steelhead hatchery smolts tended to occur at lower elevations in the main-stem Clackamas River, while winter steelhead likely spawned further upstream in the basin and largely in tributaries to the main stem. If hatchery summer steelhead spawned at lower elevations proximate to their release sites, this may have limited their ecological interactions with winter steelhead because naturally produced juvenile summer steelhead were inhabiting areas downstream of the most productive winter steelhead rearing habitat.

2. I agree with Salm g. here as well: His point here is correct in that the only population abundance information that is considered in the analysis for both hatchery summer runs and naturally produced winter runs is derived from counts at the dam. No abundance information about interaction of the hatchery program on any natural production below the dam is possible without abundance information from below the dam. Very simple.

3. Again, I agree with Salmo g.: These populations were fairly well segregated both by removal of adults at the dam and through selection of release location, thereby reducing the number of effective hatchery spawners. Again from the report: Additionally, releases of summer steelhead hatchery smolts tended to occur at lower elevations in the main-stem Clackamas River, while winter steelhead likely spawned further upstream in the basin and largely in tributaries to the main stem. David et al. (2018) found that 68% of winter steelhead spawners entered upper Clackamas River tribu-taries, but only 23% of hatchery summer steelhead were released in upper Clackamas River tributaries during the augmentation program (ODFW, unpublished data).

The major point here as Salmo g. tries to point out is that the results of this study are for the specific case of the Clackamas River and the hatchery program that was occurring in the Clackamas River not for all rivers and programs. He seems to make that pretty clear - "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)."

What it does not tell us is what some posters, such as Elijah, say it does - "...that hatchery fish are not to blame for the decrease in wild fish."

As I final thought, I'm pretty sure that the authors, although they concluded that this particular program did not have an effect on this particular population, would also not conclude that no hatchery programs has a negative effect on natural production. They certainly had that opportunity to say that in their discussion, but didn't do so. Instead they concluded the paper by pointing out the need to look at specific situations (like Salmo g. does, by the way), calling for studies that "directly quantify the effects of hatchery fish on the production of natural-origin salmon and steelhead," "empirically test published theories about mechanisms of hatchery fish impacts on natural-origin populations" and "document population responses to major changes in hatchery programs."

They clearly did not jump to the conclusion that no hatchery program has a negative effect on natural populations.