One of the biggest challenges facing the aquaculture industry everywhere, is Lepeophtheirus salmonis, the sea-louse (below).
It's a parasite which attacks both farmed and wild salmon, 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.
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Sea lice, Lepeophtheirus salmonis, on farmed Atlantic salmon, New Brunswick, CA. Photo by 7Barrym0re 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. |
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The latest (but not the only) cautionary tale about the wisdom of this practise, has just emerged from Norway.
A team of researchers there exposed (in the lab), an important food source for the fish, to varying levels of hydrogen peroxide (H202). It's the active ingredient in several such products.
The food source was a zooplankten called Calanus spp.
It's abundant in coastal waters where many salmon farms are located and is a key component in the North Atlantic food web. It's important, not only to young farmed fish, but to wild herring and cod, as well.
The lab results were convincing.
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."
I interviewed the lead author of the study, Rosa Escobar Lux of the Marine Austevoll Research Station, Norway.
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 her team were published recently in the Canadian science journal, FACETS.
Is evidence of harm confined to the lab?
Another study from Norway published just last month, takes us beyond the lab, into open waters (or "the wild" as Dr. Escobar Lux puts it). It reveals, elevated levels of the pesticide diflubenzuron (DFB) are being found in commercially-valuable northern shrimp (Pandalus borealis) in Norwegian fjords. Salmon farms there use a medicated feed containing that product. 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. Experts want further studies to find out if shrimp populations are already crashing.
And yet another recent study reaches a similar conclusion, that
hydrogen peroxide's toxicity may already be making itself felt in the open ocean, on northern shrimp. Conducted by mostly Norwegian researchers, they find hydrogen peroxide may be causing "gill damage and delayed mortality" to the shrimp, more than a kilometre from fish farms there.
Even older studies, some done in Canada, point to several other marine creatures being vulnerable to aquacultural pesticides, too. These not only include zooplankten like the kind already referred to, but commercially valuable catches such as lobster and shrimp!
Last year, experts "rounded up" those studies and combined them in a single, "systematic and exhaustive" review.
They concluded that hydrogen peroxide wasn't the only suspect product. Three others, 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."
Despite all of this, in 2016, quite some time after much of this research was known, Health Canada granted "full registration for the sale and use" of pesticides using hydrogen peroxide as their active ingredient" 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.
A year later, the Department also registered azamethiphos for an identical use, giving identical reasons for doing so.
In its documents approving registration of both products, 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. <They are> relatively benign products that pose 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 that year, be allowed one treatment more of H202 than was usually allowed.
In addition to H202, Canada has, for at least a decade, also permitted the use of deltamethrin, at least in Atlantic Canada. Cypermethrin, however, is prohibited.
In the course of my investigation, I was only able to find out how much hydrogen peroxide is being used in aquaculture.
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This image shows how industry applies pesticides within their operations. |
If that figure sounds high, amounts used in Norway - the world's largest producer of farmed Atlantic salmon - are "through the roof" by comparison. One source says, the industry in that country applied 132 million kilograms of H202 between 2009 and 2018. That would be at least than 13 times more per year than the Canadian usage!
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 describe 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. For some reason, it's the most recent figure available. In 2013, production in the sector was valued at almost $1 billion. This country is ranked as the world's 4th-largest producer of farmed salmon.
The website of the Canada Food Inspection Agency proudly states:
"Canada is one of the world's most trusted and respected food suppliers, 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.)
Are there better ways?
Researchers with Fisheries and Oceans Canada are among those looking for alternatives. 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. There's no sign, yet that such methods are about to replace that heavy pesticide use, however.
Meanwhile, research published about five years ago, seems to put an even finer point on the importance of finding alternatives - not just to pesticides - but to aquaculture itself! Growth of the industry could actually be worsening the problem. Since sea lice numbers are proportional to fish size, "expanded salmon farming has shifted the conditions in favour of the parasites. Salmon farms are often situated near migrating routes of lice in the open ocean."
And, as if that weren't enough, the lice are now showing resistance to three of the five compounds being used against them.
On January 11th, I e-mailed Canada's Minister of Health, Patty Hajdu (responsible for the Pesticide Management Regulatory Agency); Fisheries and Oceans Minister, Bernadette Jordan and the "Canadian Aquaculture Industry Alliance," to comment on my story.
I did not get a substantive response.
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