Fisheries and Oceans Canada’s (DFO) announcement unleashed a torrent of protests from First Nations leaders and environmentalists. How could “nine peer-reviewed, scientific risk assessments” find that salmon farms pose a ‘minimal risk’ to migrating Fraser River sockeye salmon? Two questions from Cortes Currents were amidst the deluge of correspondence they took in. It has taken more than a week, but the DFO finally responded to my questions about minimal risk.

The nine assessemets

First, these are the pathogens they looked at and some notes about their conclusions:

• Thanks to the work of Alexandra Morton, the most notorious of these pathogens is Piscine Orthoreovirus (PRV), but DFO states there are three kinds and the kind found in the Discovery Islands (PRV-1) is “not known to not cause disease, mortality or swimming impairment in Sockeye salmon.”
• Infectious Hematopoietic Necrosis Virus (IHNV) “can cause a disease called infectious hematopoietic necrosis (IHN). This “disease can cause death of infected fish,” but DFO regards the risk as minimal because the salmon are inoculated and “if infection occurs, industry removes infected fish from the net-pens.”
• Aeromonas salmonicida is found in salmon farms, but there have been no known fatalities and DFO believes it “is very unlikely to infect Fraser River Sockeye salmon.”
•  there are no reports of salmonid rickettsial septicaemia in Sockeye salmon.
• While “Renibacterium salmoninarum can cause bacterial kidney disease (BKD) in salmon … the concentration estimated on a farm is much lower than the one required to cause infection or death in Chinook salmon, which are more vulnerable to R. salmoninarum infection than Sockeye salmon.”
• Yersinia ruckeri “is primarily a freshwater pathogen” and rarely found ” … on farms in the Discovery Islands area.”
• Moritella viscosa “causes winter ulcer” in the Atlantic Ocean, but “to date, there is no evidence of winter ulcer in Pacific salmon species in British Columbia.”
• Tenacibaculum maritimum can cause mouthrot disease to smolts in their first year at sea. However the trigger is stress and it “mainly affects young Atlantic salmon shortly after they are transferred from freshwater to the marine environment. Pacific salmon appear to be less susceptible than Atlantic salmon.”
• The Viral hemorrhagic septicemia virus can be fatal to Pacific herring and Pacific sardine, but is not as common among wild or farmed salmon. In fact, the DFO concluded “that Sockeye salmon are not susceptible to VHSV.”

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Why aren’t sea lice on the list?

The first question I asked the DFO was why didn’t the DFO carry out a risk assessment on sea lice?

The closest they came to a direct answer was, “The completion of ten risk assessments was not a specific recommendation of the Cohen Commission.”

DFO then proceeded to explain the rationale behind the other assessments:

“When completing the nine risk assessments on pathogens in the Discovery Islands, the Department considered variables, such as the time of year and the duration of any potential impact on wild salmon, to determine if they pose more than a minimal risk to the health of migrating Fraser River Sockeye salmon. The co-occurrence of diseases on Atlantic salmon farms has infrequently been reported through either the audit program or as fish health events.”

“The Department continues to conduct research, undertake additional risk assessments and provide advice to managers on an ongoing basis to inform their decisions. As new information and advice becomes available, the Department will continue to review and incorporate the information as part of its risk-based, science-informed adaptive management process.” 

How certain is the minimal risk assessment?

As they stated the risk was ‘minimal,’ I asked about the degree of uncertainty in these assessments.

DFO responded, “Risk assessments are specifically designed to provide information to support decision making in instances where there is uncertainty. The risk assessments integrated various types of information and data, which means there are different levels of uncertainty associated with the available scientific information. For each step in the risk assessment process the overall level of certainty is identified or characterized. Uncertainty includes both variability, which is not reducible with additional data collection, and knowledge gaps.”

“In scenarios where a variable did not have a high certainty or the certainty was unknown due to information being unavailable, the Department adopted a conservative approach to ensure that the resulting risk was not underestimated.”

Top photo credit: Sea farm from the surface photo courtesy Ian Roberts