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Farmed Salmon Virus Threatens Wild Pacific Salmon
Wild salmon ally and fish-trade magazine raise red flags 01/13/2009 by Craig Weatherby

Like many seafood retailers, we subscribe to a trade magazine called Intrafish, which covers the farmed and wild seafood industries.

We generally find Intrafish pretty fair when it comes to reporting on controversial issues, but we were still surprised to see them publish an article titled "How Long can B.C. [British Columbia] Avoid ISA?”

Salmon farms from Norway, Scotland, and Chile to Eastern Canada have all suffered outbreaks of a viral disease called Infectious Salmon Anemia (ISA).

(See our report on one country's viral problem: "Chilean Salmon Farms Hit by Predictable Virus Plague.”)

So it makes sense for Intrafish to worry that ISA will spread to the many offshore salmon farms located in British Columbia.

We worry, too, because ISA could spread to BC's wild salmon and, hypothetically, to Alaskan salmon as well.

Virus from fish farms threatens wild salmon

Unlike mammals, the red blood cells of fish have DNA, and can become infected with viruses. The fish develop pale gills and may swim close to the water surface, gulping for air.

However, the disease can also develop without the fish showing any external signs of illness; they maintain a normal appetite and suddenly die. In the worst cases, ISA kills 50 percent of the fish in a single production cycle (USDA 1999 and 2002).

ISA spreads through contact with infected fish or their secretions, or with equipment or people who have handled infected fish. The virus can survive in seawater, and a major risk factor for any uninfected farm or wild salmon run is its proximity to an infected farm.

More recently, the sea lice rampant in salmon farms have been shown to carry the virus passively on their surface and in their digestive tracts, although transmission of the disease by sea lice has not been proven.

So far, salmon farms in British Columbia have dodged the ISA bullet, but Intrafish questions how much longer that luck can last.

Farm industry assurances ring hollow

According to Intrafish, "While the east coast of Canada has suffered from ISA outbreaks, the west coast of the country has remained free of the virus, although it has other issues, such as sea lice and an infectious hematopoietic necrosis (IHN) outbreak that impacted sockeye stocks” (DiPietro B 2008).

Wild salmon defender Alexandra Morton immediately sent around an email calling into question the unpersuasive assurances by the BC Salmon Farmers Association that all is well.

Ms. Morton co-authored a landmark research paper on threat posed to BC's wild pink salmon by sea lice from salmon farms sited near migratory rivers. For more on this risk, see "Canada's Wild Salmon Need Americans' Help”.

Alexandra Morton's protest to the British Columbia government

Here is what Alexandra Morton wrote concerning the ISA threat:

Dear Minister of Fisheries and Oceans the Honourable Gail Shea:

Today, the industry publication Intrafish (Jan 12) asks the question, how long can British Columbia remain free of the fish farm disease ISA that is sweeping the planet, jumping oceans and continents to wherever there are salmon farms?

Never seen in wild fish previous to salmon farming, Infectious Salmon Anemia was first encountered in 1984 in Norwegian fish farms, 1996 in New Brunswick, 1998 Nova Scotia, Scotland 1998, Chile 1999, Faroe Islands 2000 and the U.S. 2001.

ISA is an orthomyxovirus, very similar to the flu family and mutates rapidly.

ISA is transmitted and spread from farmed fish populations to wild fish. Fish handlers and equipment contaminated with the ISA virus can introduce the disease to uninfected sites and fish.

Sea lice appear to enhance transmission of the ISA virus from infected to susceptible fish.

There is no cure for ISA and the reason Intrafish is asking how long BC can remain ISAfree is because the disease is so infectious that it appears impossible to stop.

I have asked government and industry many times if British Columbia is still importing fish farm stock from ISA infected countries and no one ever seems sure.

Mary Ellen Walling of the BC Salmon Farmers Association has now cleared this question up: "We have very tight controls about importation of eggs and broodstock; essentially it's very tightly controlled and for the most part not permitted.”

"For the most part,” means you are approving live fish or live fish products into British Columbia from ISA infected countries, because ISA is in every fish farmed area except B.C.

Minster Shea, you must close the British Columbia border to importation of farm salmon livestock immediately. Intrafish is not an environmental publication, this is an industry publication and by way of this article they appear to think it is only a matter of time before B.C. is contaminated with ISA.

Do you have any idea what ISA would do to our coast? No, no one does. But we do know that the fish farming companies in BC have to date been unsuccessful in stopping the disease in other areas where they are operating.

Minister Shea, I do not think that you have the right to expose the North Pacific to ISA, a virus known to be highly infectious and able to adapt quickly through rapid mutation. Furthermore, there should be no movement of fish farming equipment or outer fish farm personnel clothing from Chile, or the North Atlantic into Canada.

This is a matter of international bio-security and of extreme importance to both Canada and the United States including Washington, Oregon and Alaska.

I look forward to your reply at your earliest convenience.

Alexandra Morton

We recommend that you not purchase farmed salmon at all, until such time as the industry is environmentally sustainable and does not threaten wild stocks (That day may never come).

But if you do, please consider telling your local fish purveyors that you will not purchase farmed salmon from Canada until they deal convincingly with this dire threat to wild salmon, as well as the threat posed by sea lice by relocating farms from the mouths of migratory rivers.


  • DiPietro B. How Long can B.C. Avoid ISA? January 12, 2009. Accessed online at
  • Ely B. Infectious Salmon Anaemia. National Institute for Medical Research. Accessed online January 12, 2009 at
  • Morton A. Email communication. January 12, 2009.
  • USDA Animal and Plant Health Inspection Service. Infectious Salmon Anemia, Canada, November, 1999: Impact Worksheet Update. Accessed online January 12, 2009 at iw_1999_files/foreign/isacanadaupd.htm
  • USDA Animal and Plant Health Inspection Service. Infectious Salmon Anemia: January 2002. Accessed online January 12, 2009 at


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