top of page

Artificially wild: how salmon farms are destroying wild Atlantic salmon populations

Updated: Feb 5, 2021

The beautiful York River on an August morning in Gaspé, Quebec. Photo Credit: Michael Fiorini

It is August 31st, 2019.

We’re wading through the impossibly clear waters of the York River in Gaspé, Quebec. Attentively, we meander along the ledges of the geological pores that hold our bounty. Their dancing shadows are a dead give away.

Fishing rods in hand, we are trying to catch Atlantic salmon (Salmo salar). There are hundreds of them, aggregated together in deep pools of the otherwise shallow august stream, acting in accordance with their anadromous behaviour. Their treacherous up-river migration is behind them now, so they lie relatively motionless in efforts to produce future generations.

Everything here appears to be wild. This is the kind of place that entices you to consciously acknowledge the seemingly mystical power of nature and evolution. The kind of place where you are infinitely thankful that humans have accepted their rightful role as distant bystanders.

A devious misconception.

Fly fisherman attempts to catch Atlantic salmon in Gaspé, Quebec. Photo credit: Michael Fiorini

Two years later, I still reminisce on this invaluable experience, but my perceptions of wild Atlantic salmon have changed. Like most things on our planet, “wild” salmon have been tampered with by the degrading hands of human beings.

The issue is aquaculture. Fish farms.

Atlantic Canada alone produces over 60 000 tones of farmed Atlantic salmon annually, courtesy of highly efficient fish farms scattered along the coasts of southern New Brunswick, Nova Scotia, and New Foundland and Labrador. [2] There is no arguing the value of aquaculture to supply the increasing human population with suitable sources of protein. But their ecological impacts on wild salmon populations cannot be over looked.

Sea-cages used for Atlantic salmon aquaculture . Photo Credit: Sam Beebe

To begin, parasites and viruses proliferate in fish farms as a result of the unnatural population density and host availability in the sea-cages. [1] These diseases are then easily transmitted across the permeable mesh of the pens to wild salmon who spend their time at sea in proximity to the farms. [8]

Salmon lice parasitism has become 4000 times more prominent among wild salmon since the beginning of fish farms. [1] While Piscine Orthoreovirus (PRV), characterized by lethargic behaviour and erratic swimming patterns, infects 79-95% of farmed salmon and is commonly transmitted to wild Atlantic salmon. [11]

Both parasitism and PRV alike can kill wild salmon. Otherwise, they impair their ability to complete their spawning migrations. [9] If Atlantic salmon cannot reproduce, the future of the species is undoubtedly grim.

The most severe ecological impacts are consequent of the two million farmed salmon that escape their sea-cages each year to enter the Atlantic ocean and nearby streams and rivers. [7]

Farmed escapees comprise up to 20% of all sexually mature Atlantic salmon. [10] Often, farmed salmon will interbreed with their wild counterparts, reducing the overall fitness of wild populations as they pass on their artificially selected traits that benefit the commercial industry: [4]

  • Extensive growth

  • Fast growth

  • Delayed maturity

These traits are not beneficial in the wild and can lead to increased fat content, and physiological, morphological and behavioural changes. [10] Contaminating the gene pool of wild Atlantic salmon with the genetics of farmed fish dismantles the process of natural selection and leads to the loss of adaptive genetic variation. [4]

Increased fat content in farmed Atlantic salmon. Photo credit: CSIRO ScienceImage

Sten Karlsson of the Norwegian Institute for Nature Research (NINA) published his findings that 6.4% of the genetic makeup of wild Atlantic salmon comes from farmed salmon, up to 40% in certain individuals. [6] Furthermore, it is estimated that 50% of wild Atlantic salmon will contain genes from farmed origin. [6] These numbers are expected to increase given the rapid expansion of the aquaculture industry.

Fisheries and Oceans Canada states:

"Atlantic salmon are considered “wild” if they have spent their entire life cycle in the wild and originate from parents who were also produced by natural spawning and continuously lived in the wild." [3]

Because interbreeding has become increasingly more common, we can no longer guarantee that the Atlantic salmon in our Canadian rivers, the ones that generate $130 million dollars a year from recreational fishing, are truly wild. [5]

"Wild" female Atlantic salmon caught on the York River in Gaspé, Quebec. Photo credit: Michael Fiorini

The smiles on our faces display the excitement any passionate angler will experience upon catching an Atlantic salmon. But it begs the question, was our salmon wild? Likely it was less then 96% wild, perhaps it was only 60% wild; artificially wild.


What can you do to help?

  • Educate yourself. Be aware of the origins of your sea food, and when possible purchase environmentally sustainable sea food.

  • Become a conscious consumer. Consult the Monterey Bay Aquarium’s Sea Food watch list for valuable information on the origins and sustainability of sea food.

  • Donate. LivingOceans is a non-profit organizations dedicated to the health and sustainability of Canadian oceans. Contributions can be made here.


  • Your opinions matter. All Comments, questions and concerns are welcomed and encouraged. Please feel free to leave comments in the comment section below, or reach out on instagram @thenorthernherd or by email:

To learn more


Works Cited

[1] Aas, Øystein, et al., eds. Atlantic salmon ecology. John Wiley & Sons, 2010.

[2]Atlantic Canada Opportunities Agency. “Aquaculture in Atlantic Canada - Atlantic Salmon.”, / Gouvernement Du Canada (2020).

[3] Fisheries and Oceans Canada “Canada's Wild Atlantic Salmon Conservation Policy.”, / Gouvernement Du Canada (2018).

[4] Fraser, Dylan J., et al. "Mixed evidence for reduced local adaptation in wild salmon resulting from interbreeding with escaped farmed salmon: complexities in hybrid fitness." Evolutionary Applications 1.3 (2008): 501-512.

[5] Gardner, Pinfold. "Economic value of wild Atlantic salmon." Atlantic Salmon Federation (2011).

[6] Karlsson, Sten, et al. "Widespread genetic introgression of escaped farmed Atlantic salmon in wild salmon populations." ICES Journal of Marine Science 73.10 (2016): 2488-2498.

[7] Keyser, Freya, et al. "Predicting the impacts of escaped farmed Atlantic salmon on wild salmon populations." Canadian Journal of Fisheries and Aquatic Sciences 75.4 (2018): 506-512.

[8] Krkošek, Martin, et al. "Fish farms, parasites, and predators: implications for salmon population dynamics." Ecological Applications 21.3 (2011): 897-914.

[9] Morton, Alexandra, et al. "The effect of exposure to farmed salmon on piscine orthoreovirus infection and fitness in wild Pacific salmon in British Columbia, Canada." PloS one 12.12 (2017): e0188793.

[10] Roberge, Christian, et al. "Genetic consequences of interbreeding between farmed and wild Atlantic salmon: insights from the transcriptome." Molecular ecology 17.1 (2008): 314-324.

[11] Wessel, Øystein, et al. "Infection with purified Piscine orthoreovirus demonstrates a causal relationship with heart and skeletal muscle inflammation in Atlantic salmon." PloS one 12.8 (2017): e0183781.


Beebe, Sam. Farmed Salmon Net Pens. La Lobada, 22 Jan. 2009.

Personal Images

The York River. 31 Aug. 2019.

Fly fisherman fishing for Atlantic salmon. 31 Aug. 2019.

Fly fishermen display a caught female Atlantic Salmon. 31 Aug. 2019.


Written by Michael Fiorini for the Wildlife Conservation course at McGill University

64 views0 comments


bottom of page