Marking 20 years
of bold journalism,
reader supported.
Rafe Mair Fund

Sea Lice Epidemic Overwhelms Fish Farms on Clayoquot Sound

Tiny parasite a growing global problem for the industry’s open net pens.

Andrew Nikiforuk 17 May

Andrew Nikiforuk is an award-winning journalist who has been writing about the energy industry for two decades and is a contributing editor to The Tyee. Find his previous stories here.

Sea lice have infested so many fish farms in Clayoquot Sound, a famed UNESCO Biosphere Reserve, that even Cermaq, a fully owned subsidiary of the Mitsubushi Corporation, has called the plague “challenging.”

In a prepared statement the company has said that it will not sell the infested fish under its “eco-label” from its affected sites.

“We are using multiple tools in the immediate term, including depopulating affected farms while treating others with an environmentally safe hydrogen peroxide bath now that we have received a licence for that approach,” David Kiemele, managing director for Cermaq Canada, writes in the statement.

But critics say the company is doing too little too late and that outbreak is just another illustration that industry’s impact on wild fish and other marine life can’t be properly regulated.

Half of the company’s 14 open-net salmon feedlots have reported sea lice levels way above the threshold that poses hazards to wild fish and triggers toxic chemical treatments or the use of mechanical devices to remove the lice in warm water or chemical baths.

Company audits on sea lice showed parasite population exponentially increasing as early January and February of this year, usually an indication that treatment programs have failed or were mismanaged, say scientists based on previous outbreaks.

By law the company must keep sea lice levels to an average of three motile lice per adult fish, but sea lice levels on Cermaq farms have reached 10 times that level or up to 34 sea lice per fish.

“It’s an environmental disaster,” said Bonny Glambeck, director of Clayoquot Action, a Tofino-based environmental group that monitors fish farms. “The outbreak will have a serious impact on wild salmon runs.”

Due to unnatural high population densities, industrial fish feedlots, which produce up to a half million fish per facility, can support massive outbreaks of billions of sea lice in places and at times where migrating salmon wouldn’t normally encounter the predator in such extreme numbers.

Just a couple of sea lice, which feed on the flesh of salmon, can cripple or kill young migrating wild chum and pink smolts, which haven’t developed scales for protection.

“Every wild migratory path for wild salmon has a fish farm on it. That means every smolt now leaving Clayoquot Sound will now have to pass by a gauntlet of fish farms exploding with sea lice,” Glambeck said.

Although the Atlantic salmon industry has succeeded in putting its fish on high end dinner tables around the world, the technology has come with a severe economic and ecological cost: a global explosion of sea lice wherever the industry has set up shop in Norway, B.C., Chile and Scotland.

The plague is the direct result of overcrowding at industrial feedlots that have given a natural ocean-going parasite easy opportunities to explode in numbers and thereby threaten migrating populations of wild fish.

In an early May visit to the outbreak area, Alex Morton, an independent biologist and fish farm activist who has co-authored 18 scientific papers on sea lice and fish farms, says some wild juvenile chum near the farms were carrying from 10 to 20 sea lice.

“They were so physically wrecked that it was hard to tell what species they are. They are being eaten alive.”

Morton, who has documented the impact of sea lice at fish farms on wild salmon since 2001, said the scale of the outbreak horrified her.

“We have told the Canadian government about all the problems posed by sea lice infestations on fish farms and the DFO still allows these industrial farms to literally eat wild fish to death,” she said.

Morton said Cermaq was now trucking in mixtures of hydrogen peroxide in a last-ditch effort to bathe its farmed Atlantic salmon in the caustic chemical solution — a treatment that burns the skin of the fish and depresses their immune systems.

The NDP provincial government has granted Cermaq permission to use two million litres of hydrogen peroxide even though the government hasn’t yet finished a review on pesticide use on open-net pens in coastal waters.

A DFO 2014 study noted that “There is little information on the toxicity of hydrogen peroxide to marine organisms.”

Michelle Rainer, a communications adviser with Fisheries and Ocean’s Canada, told the Tyee that DFO is aware of “the sea lice exceedances at Cermaq Canada's facilities in Clayoquot and has been in ongoing discussions with the company since January 2018 about measures to reduce sea lice levels.”

She added: “The department is reviewing Cermaq Canada’s sea lice management practices at these farms to determine if relevant licence conditions have been followed appropriately.” But there is “no formal investigation under the Fisheries Act or regulations.”

In a highly critical report on the federal government’s regulatory management of industrial fish farms, the Commissioner of the Environment and Sustainable Development recently noted that the DFO “had not set limits or thresholds for when to take action if it observed declines in wild fish stocks in areas where aquaculture was prevalent.”

She added that the department’s failure to define a precautionary approach to the disease and parasite spreading technology of industrial fish farming made DFO “vulnerable to claims that it prioritized the development of the aquaculture industry over the protection of wild fish.”

Each year epidemics of sea lice cost the global Atlantic salmon industry more than a $1 billion and kill untold numbers of wild fish.

The industry has tried one pesticide after another, but the lice have evolved resistance to most of the technologies including emamectin benzoate, known as Slice, a feed additive.

In recent years sea lice infestations have killed nearly 10 per cent of Atlantic salmon production at farms in the U.S., Canada, Scotland, Norway and Chile.

The outbreaks have forced the wholesale price of farmed salmon to increase as much as 50 per cent. One recent University of Chicago study estimated that sea lice plagues cost Norwegian fish farm industry nearly half a billion dollars alone in 2011. The government of Norway has imposed severe regulations on the industry because of rising deaths on fish farms due to sea lice outbreaks. It has also restricted further growth of the controversial industry unless it can better and safely control lice epidemics.

In its May 12 statement on the outbreak, Cermaq’s Kiemele said that he “takes this matter very seriously and is actively addressing it as quickly as possible through a number of strong actions, both immediate and longer-term in nature. This is challenging.”

In Scotland where sea lice epidemics have also compromised the survival of wild salmon populations, the issue has become the subject of intense political debate and investigation.

A March report to the Scottish parliament on the environmental impacts of salmon farming noted that “in order to mitigate the risk of transfer of sea lice, fish farms should be located away from salmonoid migration routes.”

The report added “that further research may be needed to ensure migration routes are adequately mapped and understood, but the committee is clear that the precautionary principle should be applied.”

A 2014 Norwegian study on the growing sea lice plague concluded: “Salmon aquaculture industry is under great pressure to control sea lice to prevent their spreading to wild fish, especially the outward migratory salmon juveniles. The cost of sea lice control may become a considerable limiting factor on farm productivity and profitability.”

This article was supported by those who generously contributed to the Rafe Mair Memorial Fund for Environmental Reporting on The Tyee. To find out more or contribute, click here.  [Tyee]

Read more: Food, Environment

  • Share:

Facts matter. Get The Tyee's in-depth journalism delivered to your inbox for free

Tyee Commenting Guidelines

Comments that violate guidelines risk being deleted, and violations may result in a temporary or permanent user ban. Maintain the spirit of good conversation to stay in the discussion.
*Please note The Tyee is not a forum for spreading misinformation about COVID-19, denying its existence or minimizing its risk to public health.


  • Be thoughtful about how your words may affect the communities you are addressing. Language matters
  • Challenge arguments, not commenters
  • Flag trolls and guideline violations
  • Treat all with respect and curiosity, learn from differences of opinion
  • Verify facts, debunk rumours, point out logical fallacies
  • Add context and background
  • Note typos and reporting blind spots
  • Stay on topic

Do not:

  • Use sexist, classist, racist, homophobic or transphobic language
  • Ridicule, misgender, bully, threaten, name call, troll or wish harm on others
  • Personally attack authors or contributors
  • Spread misinformation or perpetuate conspiracies
  • Libel, defame or publish falsehoods
  • Attempt to guess other commenters’ real-life identities
  • Post links without providing context


The Barometer

Would You Live in a Former Office Building?

Take this week's poll