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Fires around Ft. MacMurray, Alberta, Canada in 2016.
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Toxic Tides

One of the biggest challenges facing the aquaculture industry everywhere, is Lepeophtheirus salmonis, the sea-louse. 

 Sea lice, Lepeophtheirus salmonis, on farmed
Atlantic salmon, New Brunswick, CA.

Photo by 7Barrym0re

It’s a parasite which attacks both farmed and wild salmon (r.), causing lesions and infections which stunt their growth. But the costs of de-lousing are high. And so are the losses suffered by the industry in the marketplace. Many lice can actually kill many fish.

To fight back, the fish-farmers dump pesticides into the waters (below). But, because they’re released directly into the environment, they not only kill the lice, but place beneficial, “non-target” organisms at risk, too. And several of these live in the open ocean, beyond the confines of the  farms.

This image shows how industry applies pesticides within their operations.

The latest (but not the only) cautionary tale about the wisdom of this practise, comes out of Norway. 

A team of researchers there exposed an important food source for the fish, a zooplankten called Calanus spp. (below) to varying levels of hydrogen peroxide (H202) in the lab. 

Calanus spp. Illustration by the

Scripps Institution of Oceanography.

Calanus spp. is abundant in coastal waters where many salmon farms are located. It’s a key component in the North Atlantic food web, important not only to young farmed fish, but wild herring and cod, as well. 

H202 is the active ingredient in many of the pesticides used in this manner.

The lab results were striking.

In just one hour, at only 10% of levels the farmers would apply, 92% of the juvenile Calanus spp. and all of the adult females died. And, at much lower doses (1% or less), the ability of the organisms to take in oxygen was greatly reduced. Their “escape response” was destroyed, making the likelihood of them being eaten by predators, "extremely high." The researchers concluded,  "Present recommended levels of application underestimate the impact of the pesticide on non-target crustaceans.”

Rosa H. Escobar Lux, PhD candidate,

Research group Disease & Pathogen 

Transmission.Havforsknings Institute 
of Marine ResearchAustevoll Research Station, 
Norway.

I interviewed the lead author of the study, Rosa Escobar Lux (l.).

PinP: Do you have any evidence that the abundance of Calanus spp. may be affected to the degree that the fish themselves are becoming "food-deprived?" 

Dr. Escobar Lux: "No. Our experiments were done in a laboratory which can answer some of our questions but it does not give definite answers to what is happening in the wild.  Also, there's a need for dispersion models to help us understand the real magnitude of the effects...."

The findings of Dr. Escobar Lux's team were published recently in the Canadian science journal, FACETS.

Past Evidence Casts an Even Wider Net.

But this is hardly the only evidence of adverse effects. Previous research studies, some done in Canada, point to several other marine creatures being vulnerable to aquaculture pesticides, too. Last year, experts "rounded up" those studies and combined them in  a single, "systematic and exhaustive" review. 

They concluded that hydrogen peroxide was not the only suspect product. Three other pesticides, cypermethrin, deltamethrin and azamethiphos - each used extensively in the industry - had similar effects.  

The review concludes, "Aquaculture has consequences for the environment. Salmon and trout cage culture has required the use of large quantities of pharmaceuticals. Our results show clear negative effects at concentrations lower than those used in treatments against sea lice in all of the species studied." 

Those species included, not only marine zooplankten, like the one studied in Norway, but American lobster and shrimp.

In the course of my investigation, I was only able to find out how much hydrogen peroxide is being used in aquaculture - not the other products mentioned here. And it's not immediately known if they're registered here in Canada, too.

Health Canada figures (see table) show more than one million kilograms of hydroxen peroxide were sold in 2016. That placed the active ingredient among the top ten best-sellers that year (9th). It did not register in the top ten the following year. (The government counts products sold for aquaculture as "agricultural.")

Top 10 Active Ingredients Sold in Canada in 2016 in the Agricultural Sector

Active Ingredient	Product Type
Glyphosate	Herbicide
Surfactant blend	Other
Available chlorine, present as sodium hypochlorite	Antimicrobial
Glufosinate ammonium	Herbicide
2,4-D	Herbicide
MCPA	Herbicide
Mineral oil	Insecticide/Fungicide/Other
Mancozeb	Fungicide
Hydrogen peroxide	Herbicide/Insecticide/Fungicide
Chlorothalonil	Fungicide

Source - PMRA - Health CA. 

If that figure sounds high, amounts used in Norway - the world's largest producer of farmed Atlantic salmon - are even higher. One source says, the industry in that country applied a whopping 132 million kilograms of H202 between 2009 and 2018. That would be more than 13 times Canada's yearly usage!

Is evidence of harm confined to the lab?

Another study from Norway published just last month,  takes us beyond the lab, into open waters. Elevated levels of a toxin have been found in commercially-valuable northern shrimp, (Pandalus borealis) in Norwegian fjords. Salmon farms there use a medicated feed containing the pesticide diflubenzuron (DFB). Lab tests have shown it can be lethal to the shrimp, and actually becomes more toxic in warmer waters. This raises added concerns in a world that is heating up fast.

Many Norwegian fishers report, they're catching fewer shrimp in fjords where salmon farms are operating. The research suggests further study needs to be done to find out whether shrimp populations are already declining. 


(I can find no record of DFB being registered for use in Canada.)

So why do regulators continue to register these products?

The importance of aquaculture to human society is widely recognized. In their own studies, the researchers refer to it as "One of the best prospects to help meet the growing need for protein in the human diet." 

The UN's Food and Agriculture Organization estimates, almost 19 million people worked in that sector in 2015. The world now produces about as much farmed fish as that taken in the wild. Once non-fish products (plants, shells and pearls) are added in - more than 100 million tonnes, or US$163 billion dollars worth of products, were produced by "ocean-farming" that year. It's considered the fastest-growing source of food for human consumption and is made up mostly of "finfish" such as the Atlantic salmon.

In Canada, government figures show, aquaculture employed 14 thousand people, full-time in 2009, the latest available figure. In 2013, the value of production in the sector approached $1 billion. This country is ranked as the world's 4th-largest producer of farmed salmon. 

The website of the Canada Food Inspection Agency paints a glowing picture of the industry here.  

"Canada is one of the world's most trusted and respected food suppliers," it boasts, "trusted to provide safe and wholesome products and respected for our commitment to global food security. Canada's strong regulatory system forms the basis of this positive reputation."  (Emphasis mine.)

Notwithstanding that "strong regulatory system," in 2016," Health Canada granted "full registration for  the sale and use" of pesticides using hydrogen peroxide as their active ingredient," including 
Paramove, for the treatment of sea lice on Atlantic salmon reared in marine aquaculture sites." That was at least five years after the first warnings about the pesticides I was personally able to find…warnings that our government officials must have been aware of. 

Yet, in its document approving registration of H202, Health Canada concludes, "Under the approved conditions of use, the products have value and do not present an unacceptable risk to human health or the environment. Hydrogen peroxide is a relatively benign product that poses little or no risk to salmon, the marine environment, non-target species, or human health." 

It went on to recommend that the industry, facing one of its worst years for sea lice infestation up 'til then, be allowed one treatment more than was usually allowed. 

Are there alternatives?

Researchers with Fisheries and Oceans Canada are among those looking for better ways. 

They're trying to find out whether physical light traps and biological filters may be able to attract and remove the sea lice from the farms.

More than two weeks ago, I e-mailed Canada's Ministers of Health, Patty Hajdu (responsible for the Pesticide Management Regulatory Agency); Fisheries and Oceans, Bernadette Jordan and the industry group, "Canadian Aquaculture Industry Alliance" to comment on my story. 

None has responded, so far.

-30-

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