Farmed salmon could become an invasive species in forest streams

March 8, 2007

Ever since the Norwegians expanded commercial farming of salmon in the 1960s, the industry has continued to rapidly grow worldwide. It has expanded to such a degree that prices for farmed salmon have plummeted and, there is concern that farmed fish may become the next invasive species.

"Farmed fish escaping from marine net pens might become an invasive species in British Columbia, Washington or Alaska," says research fish biologist Peter Bisson. "Net pen culture of salmon is big business worldwide, and both advocates and opponents of salmon farming have been very vocal in stating their views. I wanted to look at the hard evidence to determine the short- and long-term risks to native species in streams on National Forests."

Bisson, a staff scientist with the Pacific Northwest Research Station/Forest Service, began work on the report, Assessment of the Risk of Invasion of National Forest Streams in the Pacific Northwest by Farmed Atlantic Salmon, to assess the potential impact of farmed salmon on native fishes inhabiting streams on National Forest System lands and to learn if concerns from both sides of the farmed-versus-wild fish debate had validity, based on an extensive literature review.

Here are some of the findings in the report:

-- At present, breeding populations of escaped farm salmon are not known to exist on National Forest System lands, but the locations of Atlantic salmon farms and the sightings of escaped salmon indicate that streams on four national forests may be at risk: the Tongass and Chugach NF in Alaska, and the Olympic and Mount Baker-Snoqualmie NF in Washington.

-- Atlantic salmon could transmit a serious disease or parasite to native fishes.

-- Escaped salmon may eventually adapt to local conditions, leading to self-sustaining populations.

-- Escaped salmon could compete with already at-risk species, such as steelhead.

Source: USDA Forest Service