The science is clear: open net pen fish farms put wild Pacific salmon at risk

Piscine Orthoreovirus (PRV) is a highly contagious virus affecting salmon in BC. A new study, published May 26, 2021, from the University of British Columbia, the Department of Fisheries and Oceans, GenomeBC and Pacific Salmon Foundation shows PRV (piscine orthoreovirus) arrived in BC at the same time as industrial fish farming. It confirms that, during their time in open net pen fish farms, nearly all farmed salmon are infected with PRV^[1].

The study also confirms that endangered wild Chinook salmon from areas near the farms are far more likely to pick up the infection than Chinook in areas without farms. In Chinook salmon, the virus causes kidney and liver damage that can be fatal.

In Norway, PRV has been linked to Heart and Skeletal Muscle Inflammation (HSMI), which causes problems with the heart, liver, spleen, and other internal organs in salmon. HSMI has a mortality rate of 20%^[2]. It is a deadly disease that can quickly devastate a salmon population.

PRV is extremely contagious. 95% of farmed salmon in BC test positive for PRV^[3]. The dense nature of open net pen fish farms allows PRV to mutate to higher levels of virulence. Most concerning, PRV can be spread through water, making wild Pacific salmon who come in close proximity to open net pen fish farms highly susceptible to the virus. PRV is a powerful example of what happens when viruses are left to replicate in open net pen fish farms.

Fish farm waste is having a significant impact on the health of wild Pacific salmon. Although far from the only source of pollution in our oceans, open net pen fish farms discharge extraordinarily high concentrations of untreated sewage. These include large quantities of chemicals including copper, zinc, antibiotics such as oxytetracycline and oxolinic acid, anti-parasite compounds like ivermectin, and numerous insecticides. ^[1]

BC currently has over 100 open net pen fish farms. A single average-sized fish farm of 200,000-fish produces:

• fecal matter equivalent to 65,000 people
• nitrogen equivalent to 20,000 people
• phosphorous equivalent to 25,000 people^[2]

When compared to humans, these numbers are staggering. In 2000, WWF Scotland calculated that phosphorous nutrient pollution from Scottish aquaculture was comparable to a city of 9.4 million people. At that time, Scotland’s population was just over 5 million people. ^[3]

This pollution contaminates the seabed and damages marine biodiversity – not just directly below the open net-pen salmon farms, but also hundreds of metres away. Marine dives have found these “dead zones” are completely devoid of marine life. ^[4]

Open net pen fish farms pollute our oceans for free. While fish farming is an important industry, it is imperative that BC moves to more sustainable farming methods with land based closed containment farms to ensure the preservation of the province’s delicate ecosystems.