British Columbia·In Depth

Pressure is on to find out if fish farms make wild salmon sick, says federal scientist

Anti-fish farm activists launched a new campaign this week highlighting a virus on fish farms. But what do scientists know so far about sick fish? Not enough, says a federal researcher leading the charge.

Once-muzzled federal scientist talks about the push to find out what diseases can hurt wild salmon

Spawning sockeye salmon are seen making their way up the Adams River in a spectacular display. Research is underway to answer outstanding questions about what role fish farms may play in disease transfer to wild fish. (The Canadian Press)

It's enough to make even the most ardent salmon lover lose their appetite: the divisive debate that's raged for decades on the West Coast about what fish farms are doing to our wild salmon.

This week, the latest volley: starlet Pamela Anderson and David Suzuki teamed up to launch an advocacy-slash-research mission looking for PRV — a fish virus especially prevalent on fish farms. The industry dismissed the campaign as a "stunt."

But there's no doubt the questions about farmed fish transferring disease to wild salmon are very real, said the Fisheries and Oceans Canada scientist co-leading the largest push to investigate them.

The problem is, they're also exceptionally difficult to answer.

"There is now a lot more public pressure to get information on this," said Kristi Miller, head of molecular genetics at DFO's Pacific Biological Station.

"I think that there's been a frustration that the science and policies needed to address this are just not forthcoming fast enough."

Actress and animal-rights activist Pamela Anderson was in Vancouver, Monday, urging consumers not to eat farmed salmon from B.C. (CBC)

Virus linked to heart disease

The virus that fish farm opponents are looking for on the B.C. coast this summer is called piscine reo-virus, or PRV, which may cause a deadly salmon disease called Heart and Skeletal Muscle Inflammation, or HSMI.

There's no debate that it's present on fish farms, even the B.C. Salmon Farming Association says most fish on farms are infected with PRV.

Kristi Miller is the head of molecular genetics for DFO's Pacific Biological Station, and helped launch the Strategic Salmon Health Initiative, a research partnership between DFO, Genome B.C. and the Pacific Salmon Foundation. (Nik West/Strategic Salmon Health Initiative)

But it's a hotly-contested question — that Miller and others are working on — as to whether PRV actually causes the disease.

Every farmed fish found with the disease has also had the virus, said Miller, whose team discovered the first case of HSMI on a B.C. fish farm in May.

"There's a pretty good weight of evidence that [PRV] is certainly a factor in the development of HSMI in Atlantic salmon," said Miller.

"But what other triggers may be required isn't really well understood."

It's complicated, because fish can be infected, but not sick — a fact industry points to as evidence there's no conclusive link.

And, the lab tests done so far to figure out if there is a cause-and-effect relationship have had conflicting results, said Miller. 

If PRV does cause the disease and if it's transferred to wild fish, that's a big concern, because wild salmon need to be marathon swimmers — with healthy hearts — to escape predators and migrate upstream to spawn.

An open net pen salmon aquaculture operation near Venture Point, north of Campbell River, B.C. The B.C. Salmon Farmers Association has said 70 to 80 per cent of fish on salmon farms have piscine reo-virus, or PRV. (B.C. Salmon Farmers Association)

Cohen Commission was a turning point

It might be surprising that those big 'ifs' are still unknown when questions about diseases from fish farms have been raised for years, be it PRV, infectious salmon anemia, sea lice, or other pathogens.

Anti-fish farm activists have accused DFO of dragging its feet, and having a conflict of interest to both promote the aquaculture industry and protect wild stocks.

It's a potential conflict that Justice Bruce Cohen, who led the federal commission into the decline of Fraser River sockeye, also identified as a concern. 

In his final report in 2012, he called on DFO to find answers, or hold off on more fish farms.

Miller, who has worked at DFO for more than two decades and studied the controversial disease question for years, said the Cohen Commission was a turning point.

"There's always been research ... trying to understand disease processes in aquaculture fish, but never really taken to the level of impacts on wild fish," she said.

"Maybe we needed the Cohen Commission to motivate both the department and other academic researchers to really look closely at this question."

Salmon health study underway

Now, sparked by Cohen, she leads genomic research for the Strategic Salmon Health Initiative, a partnership between DFO, Genome B.C. and the Pacific Salmon Foundation — investigating 45 pathogens in wild, farmed and hatchery fish, including PRV.

That initiative is supported by both sides of the debate, with salmon farmers giving the "world class" researchers access to their fish.

"We are relying on this team to ensure advocacy and research do not get confused," said Jeremy Dunn, executive director of the B.C. Salmon Farming Association.

The discovery of HSMI on a B.C. fish farm in May was the first taste of what that work might reveal.

"Our work on one of the salmon farms did show definitive proof that the disease actually was present here in B.C. What we don't know is  … how commonly it may be observed."

Migrating salmon need to be healthy to make the trip upstream to spawn. Diseased fish are likely to be picked off by predators or other selective pressures, making it difficult to know what's going on. (The Canadian Press)

How do you find a sick fish?

And the impact on wild salmon from that pathogen — let alone the 44 others — is unclear.

Molecular testing has found PRV in wild Pacific salmon, including sockeye, Chinook, coho, and chum — but HSMI hasn't been found yet in Pacific salmon, said Miller.

Unfortunately, that doesn't mean wild fish aren't getting sick.

"Understanding disease processes in wild migrating fish is a really hard question, because we don't observe them die," said Miller.

"Some might say, well there is no disease because we don't observe dying fish, but you don't observe them because they drop out of the water column."

Any slight decline in speed, eyesight, feeding ability, anything, would make a migrating salmon easy prey — whereas a cultured fish might just have a slow day in the pen.

"Disease or other kinds of stressors put wild fish much more at risk than perhaps farmed fish."

So, the research continues, with a pressure for answers, said Miller.

"I know that this is very very important in Ottawa, and they are pushing to get information on this all the time right now."

A show of wild salmon migrating up B.C.'s Scotch Creek. (Matt Casselman)


Lisa Johnson is an editor and senior writer at CBC News, and a producer of CBC Radio's What On Earth. She enjoys making sense of complicated things and has also reported for CBC TV and radio in B.C. with a specialty in science, nature, and the environment. Get in touch at or through Twitter at @lisasj.


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