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A European strain of a deadly salmon virus has been found in wild salmon stocks in Canada

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Warning as infectious salmon disease spreads from Europe's fish farms to Canada

Anna Taylor

15th December, 2011

Discovery of the deadly salmon virus Infectious Salmon Anaemia in Canada is just latest likely example of disease spreading to wild fish stocks from the world's mega fish farms

The rise of the farmed fish industry in recent years has been accompanied by the emergence of many infectious diseases of fish. One of the most recent and serious diseases is the marine viral disease, Infectious Salmon Anaemia (ISA).

First detected in Atlantic salmon farmed along the southwest coast of Norway in 1984, it has since spread throughout the world.

As the name suggests, ISA shows itself by a severe anaemia, with fish displaying pale gills, and often swimming close to the surface of the water, gulping for air. More insidiously, however, many fish show no signs at all until they suddenly die.

An outbreak of the ISA was detected in wild Pacific salmon last October, in the Canadian province of British Columbia. Outbreaks of this virus have previously been detected in fish farms in Chile and Scotland, and although not dangerous to human health, have had serious impacts on the industry and the communities who depend upon it.

Infection spreading to wild fish

Effective management of the diseases of aquatic animals can be problematic. Often, too little is known about the infection itself, and infections can spread via flowing water and populations of wild fish sharing the same waters as farmed fish.

British Columbia’s ISA outbreak in wild salmon was discovered by researchers from Simon Fraser University, led by Professor Richard Routledge. Samples were taken in May and June last year as part of a ten year study into the importance of the Rivers Inlet area to migrating juvenile sockeye salmon.

'It was not until toward the end of the migration season, when we realised how few juvenile sockeye salmon we were going to be able to catch, that we began to consider possible causes of the low catch rate. ISAv was just one of several potential causes that we eventually considered,' said Professor Routledge.

Samples from 48 wild salmon were sent to the reference laboratory at the University of Prince Edward Island, the global centre for tests to detect the virus. They confirmed the presence of ISA in two of the fish. Subsequently, three out of ten fish collected from a tributary of Fraser River, the biggest wild salmon river in the world, also tested positive for the ISA virus. The three fish were all different species: coho, chinook, and chum salmon, and all three died before they had spawned, although the cause of death has not yet been determined.

These results have not surprised many scientists, who see infection in the wild population as inevitable and point the finger of blame at nearby fish farms. Rivers Inlet, where the positive samples were taken, is just 60 miles from the nearest salmon farm, and although there is no definitive evidence, the fact that it was the European strain of the virus which was detected, seems to suggest that this is a distinct possibility.

The aquaculture industry in British Columbia has imported millions of Atlantic salmon eggs from Norway and other countries in Europe for the past 25 years. Previously ISA had been found in ocean-going salmon, but was not deadly until it morphed into a virulent strain in Norway’s fish-farming pens. Poor aquaculture practices are thought to have contributed to the mutation, with unhealthy fish being fed antibiotics and living in densely packed pens. A diseased fish comes into close contact with many other fish, spreading ISA via urine, blood and other bodily fluids. As the fish farm has an open net, disease can be easily transferred to the outside world.

Professor Routledge believes that the fish farms are 'an important potential pathway for ISAv to be spread to wild Pacific salmon.'

Industry rejects call to reform fish farms

Many have been campaigning for years against open net fish farming. The Coastal Alliance for Aquaculture Reform (CAAR), comprising of groups working to promote safe salmon farming in British Columbia, has led efforts to develop a safe salmon farming industry. Will Soltau who works for the Living Oceans Society, one of the member groups, says that CAAR has 'worked for the last decade to stop the expansion of open net-cage salmon farming in BC and advocate for transitioning the open net-cage farms into closed containment technology. That transition would separate the farmed fish from the wild fish and thereby eliminate a lot of the negative effect from the industry to the marine environment.'

Unfortunately, the Canadian Government has not acted on advice and the industry has resisted change. 'We are now faced with the possibility of this disease being introduced to the North Pacific Ocean for the first time and spreading in wild salmon stocks,' adds Mr Soltau.

Campaigners are right to be worried. In 2007, an outbreak of ISA in Chile decimated their lucrative farmed salmon industry. More than 100 fish farms were affected, with over a million fish being killed and 50 per cent of workers losing their jobs. The cost of ISA over the last 4 years is estimated to be around US$2 billion, and the industry is yet to recover from the impacts of the disease.

Scotland too has had to tackle its own outbreaks. In 1998/99, ISA was confirmed at 11 sites, and suspected at 34 additional sites, scattered across virtually the entire salmon farming region. The cost to the industry was estimated to have amounted to £30 million. Ten years later ISA returned, although this time on a much smaller scale. Six infected sites in Shetland were confirmed and depopulated of fish, and only after 2 years of monitoring and testing were they declared ISA free.

Shock of Canada disease outbreak


In British Columbia, salmon farming and the wild commercial salmon sector combined provides over 3,000 full-time equivalent jobs, and contributes hundreds of millions of dollars to the provincial GDP. Salmon sport fishing is also important to the economy, and is a significant employer. 

The news of ISA in British Columbia has surprised those in the industry. The British Columbia Salmon Farmers Association stated that their fish health departments regularly test farmed fish for ISA but have never found a positive result. In addition, the Canadian Government has conducted tests on the original wild samples.

They were sent to a laboratory at the University of Bergen in Norway, and the Canadian Food Inspection Agency (CFIA) announced that the lab found no evidence of ISA.

However, this statement is misleading according to Professor Routledge. 'The Norwegian lab was able to generate one positive test result on a sample from one of the two fish that had previously tested positive, but the result was not repeatable. One explanation for the discrepancy that seems highly credible to me is that the samples were by then degraded.' The samples were of too poor a quality for the results to be replicated so the CFIA announced, somewhat controversially, that the results were negative. 

Alexandra Morton, the marine scientist and outspoken wild salmon activist who collected the Fraser River samples, cannot understand the government’s response. 'Why would government jump out and deny evidence of ISA virus in BC? If the samples were poor wouldn't it make sense to go back to the places where the positive tested fish came from and take their own samples? How can we take any confidence when government says everything is fine because the virus was found in poor quality samples?' She continues: 'ISA virus is the most deadly salmon virus known, it plagues salmon farms worldwide but Canada is going to ignore the results from two of the top ISA virus labs in the world, because the samples were of poor quality?'

Alaska fears spread to its fish

While the Canadian Government is playing down the fears of ISA, the United States Government has taken the opposite stance. In a statement released by senators from Washington State and Alaska, fears were expressed that the Canadian government may be too close to the multi-billion dollar industry. They called upon the United States to conduct their own tests, as 'we should not rely on another government – particularly one that may have a motive to misrepresent its finding – to determine how we assess the risk ISA may pose to American fishery jobs. We have to get a coordinated game plan in place to protect our salmon and stop the spread of this deadly virus.'

As ‘Salmongate’ (as the North American press have dubbed this debate) continues, it is clear that more tests are needed to confirm the initial findings.  'I believe that top priority needs to be given to collecting, preserving, and analysing new samples under tight protocols to obtain more definitive evidence regarding the presence, geographic range, origin, etc., of the virus in the North Pacific,' says Professor Routledge.

The stakes are high, especially with so many people dependent on salmon-related industries in the Pacific Northwest. Campaigners are viewing the ISA outbreak as one reason why changes to aquaculture procedures are essential, but scientists admit that they are on a steep learning curve. Swift action is necessary, but no country has ever managed to completely eradicate ISA, and reverberations of this outbreak may be felt far and wide for many years to come.

 

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