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NEWPORT - Domesticated salmon on the lam from aquaculture farms continue to pose a serious threat to wild salmon, says a scientist at Oregon State University's Coastal Oregon Marine Experiment Station here who has studied the phenomenon in several parts of the world.

"Escapes remain a major concern throughout northern Europe, especially for threatened wild populations," and the problem could escalate quickly in areas such as British Columbia and eastern North America with growing aquaculture industries, said OSU fish ecologist Ian Fleming.

Concerns are that farm salmon escaping from ocean net pens will negatively affect wild salmon populations through competition, predation and the transmission of diseases, said Fleming. Another concern, he said, is that genetic traits important for survival in the wild could be disrupted through interbreeding with farm fish. The number of truly wild salmon is declining, according to Fleming.

The researcher said even though less than one percent of farm-raised salmon escape into the wild, 20 to 40 percent of the salmon in the wild now are of farm origin.

"The reason is that the scale of the farm production dwarfs wild production by more than two orders of magnitude," Fleming said. "While there have been considerable improvements in containment (of farmed salmon), the rate of expansion of the industry has far exceeded the ability to control the scale of escape."

The fish ecologist, who joined the OSU faculty last year, spent 10 years in Norway studying interactions between farm and wild salmon. He still holds an adjunct position with the Norwegian Institute for Nature Research.

Concerns about interactions between hatchery-raised salmon and wild salmon, a contentious topic in Oregon and other parts of the Pacific Northwest, are similar to the concerns about the influence of farm-raised salmon on wild salmon, according to Fleming.

As a graduate student in Canada in the mid-to-late 1980s at Simon Fraser University, and subsequently the University of Toronto, Fleming studied interactions between hatchery and wild coho salmon. He is constructing an OSU research program that will gather information about the lives and interactions of wild and hatchery-raised salmon in Oregon and other parts of the Pacific Northwest.

The researcher said farm salmon originated from fish collected from wild populations in the 1970s. Since then, farm fish have been selected for growth rate, age at maturity, resistance to diseases and flesh quality.

Escaped farm salmon can spawn successfully in the wild, but their breeding performance can be inferior to that of wild salmon, according to Fleming, especially for males, fish that escape shortly before spawning, and fish in rivers with healthy breeding populations of wild fish.

The researcher said the offspring of farm salmon, and of matings between farm and wild salmon, are more aggressive and outgrow wild fish, but they appear to incur higher mortality during early life stages, possibly because they are easier targets for predators. Simultaneously, he said, wild fish appear to suffer in resource competition with the more aggressive farm fish.

"Our findings suggest that gene flow from farm to native fish will lead to wild populations changing genetically and behaviorally in the direction of domesticated salmon," write Fleming and Kjetil Hindar, a researcher at the Norwegian Institute for Nature Research, in an article to appear in a book that is in press.

"Moreover," the researchers say in the article, "wild populations may suffer depressed productivity caused by ecological interactions. This questions the long-term viability of many salmon populations."

According to Fleming and Hindar, possible solutions for protecting wild salmon include:

• Controlling inflowing and outflowing water at fish farms to eliminate the possibility of escape;
• Sterilizing the fish in such aquaculture operations;
• Situating fish farms away from important river populations of wild fish;
• Selectively harvesting farm escapees;
• Restricting the transport of farmed fish;
• Setting up gene banks to protect important genetic traits of wild fish.