Science shows there is no need to ban salmon farms

But will Canada undermine economic self-determination for First Nations by banning BC salmon farms that pose no more than a minimal risk to wild salmon?

Commentary
By Dr. Gary D. Marty

Salmon farm diseases have no more than a minimal effect on wild salmon population size. Fish health professionals can work to further minimize the spread of farm salmon diseases without the banning of salmon farms and the benefits that those farms provide Indigenous people in Canada.

In a July 3 Hill Times article reporting Canada’s decision to ban open-net pen salmon farms in British Columbia by 2029, Energy and Natural Resources Minister Jonathan Wilkinson is quoted as saying, “’virtually every scientist in academia, the Pacific Salmon Foundation, and a range of others’ agree salmon farming is a real problem contributing to those [population] declines.”

I respectfully disagree.

A 2012 scientific paper from Simon Fraser University, led by Dr. Randall Peterman, reported that “recent decreases in abundance and productivity of Fraser River sockeye salmon occurred across a large geographic area” ranging from Washington to southeast Alaska.

Restated, this academic study found no differences between sockeye salmon populations whether or not they were exposed to salmon farms.

The 2012 final report from the Cohen Commission of Inquiry into the Decline of Sockeye Salmon in the Fraser River recognized that “potential harm posed by salmon farms to Fraser River sockeye salmon is serious or irreversible.” 

However, Justice Cohen also recognized, “There was a statistically significant declining trend in the number of high-risk diseases reported by salmon farms between 2003 and 2010.” 

 His independent assessment concluded, “Data presented during this Inquiry did not show that salmon farms were having a significant negative impact on Fraser River sockeye.”

I have veterinary school appointments at the University of Saskatchewan and the University of California, Davis. 

For 41 years, I have been one of roughly 250 members of the Fish Health Section of the American Fisheries Society, serving as president from 2021-2022. The Section includes many academic scientists and their graduate students. 

The American Association of Fish Veterinarians has about 300 members. A few veterinarians are members of both organizations. To the best of my knowledge, none of these approximately 500 fish health professionals agree that salmon farming is a real problem contributing to declines of wild salmon.

I call these fish health professionals “the silent majority.” Few are active on social media, and many work for natural resource agencies that restrict staff participation in public debate. But these restrictions do not negate the power of their knowledge:

• Disease is a normal part of all animal populations. Therefore, all populations that interact have some risk of disease transfer.
• A “risk” of disease transfer is almost meaningless unless it is linked to a “consequence,” such as decreased population size in relation to reference populations.
• When risk is not associated with consequences at the population level—as with Dr. Peterman’s academic study described above—we can be confident that the risk is minimal.
• The spread of infectious disease has two basic components, both of which are enhanced within salmon farms but reduced for wild salmon: 1) How long is the fish infectious? Sick wild salmon are eaten by predators, so they are not infectious for as long as farm fish, which are protected from predators; and 2) How many contacts does the infectious fish have before it dies? Wild salmon are more dispersed than farm salmon, so wild salmon have fewer contacts than farm salmon.
• Public government records about disease on B.C. salmon farms provide good evidence that only about three per cent of farm salmon die each year from infectious disease. I am confident in this number because I am one of 12 pathologists who contributed data to this assessment.
• Telemetry studies inform us that Fraser River sockeye salmon spend only about two hours of their lives near salmon farms, which is 0.02 per cent of the time that farm salmon are in contact with each other (i.e., farm salmon are in contact with each other 24/7 throughout the year).
• Because only three per cent of farm salmon die from infectious disease, basic principles of infectious disease lead us to expect much less than three per cent of Fraser River sockeye salmon to die from farm-source infectious disease (0.02 per cent of three per cent = 0.0006 per cent).
• Annual mortality of 0.0006 per cent is not a threat to wild salmon. It would take more than 1,600 years for this mortality to add up to one per cent.

We need to put salmon farm disease in perspective with how we respond to infectious disease in humans.

Public government records inform us that more than 8,000 Canadians die each year from hospital-acquired infections. While each death is a tragedy to the people affected, we recognize the overall benefit of hospitals and do not advocate for banning hospitals to avoid these deaths.

Instead, medical professionals work to reduce the number of deaths. 

Likewise, we recognize the overall benefit of salmon farms for Indigenous Peoples, and fish health professionals work to minimize farm salmon infectious diseases without the banning of salmon farms.

For the past 20 years, Dr. Gary D. Marty has worked as a diagnostic fish pathologist in British Columbia, first for the B.C. Ministry of Agriculture, and since 2023 as an independent consultant.

This opinion piece was originally published by The Hill Times

Image shows Dr. Gary D. Marty.