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    Author(s): Peter A. Bisson
    Date: 2006
    Source: Gen. Tech. Rep. PNW-GTR-697. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 28 p
    Publication Series: General Technical Report (GTR)
    Station: Pacific Northwest Research Station
    PDF: Download Publication  (932 KB)


    This report describes the evidence for invasion of Pacific Northwest streams by Atlantic salmon (Salmo salar) that have escaped from marine salmon farms, and assesses the potential impact of farmed salmon invasion on native fishes inhabiting streams on National Forest System lands. The current risk to streams on National Forest lands in the Pacific Northwest from Atlantic salmon invasions appears to be low and is limited to a few areas in northwest Washington and southeast Alaska. However, long-term risks may be substantial if fish continue to escape from marine rearing pens or freshwater hatcheries. The two greatest threats appear to be that (1) Atlantic salmon could transmit a serious disease or parasite to native fishes, and (2) escaped salmon could eventually adapt to local conditions, leading to self-sustaining populations. If Atlantic salmon populations are eventually established, this species’ preference for swiftly flowing stream habitats could facilitate competition with currently at-risk species such as steelhead (Oncorhynchus mykiss). This could result in a pattern of expansion similar to that observed in other nonnative aquatic plants and animals, in which a prolonged early colonization period is followed by a rapid phase of exponential growth as breeding populations adapt to local conditions.

    Publication Notes

    • Visit PNW's Publication Request Page to request a hard copy of this publication.
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    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.


    Bisson, Peter A. 2006. Assessment of the risk of invasion of national forest streams in the Pacific Northwest by farmed Atlantic salmon. Gen. Tech. Rep. PNW-GTR-697. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 28 p


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    Atlantic salmon, invasive aquatic species, salmon farms, Pacific Northwest streams.

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