Thank aquaculture for ocean virus knowledge

If it wasn’t for aquaculture, we would know almost nothing about ocean viruses.

It was only in the late 1980s that scientists really became aware of how many viruses are out there in the ocean, millions in a teaspoon of ocean water.

And it was only in the late 1990s and early 2000s that scientists came to understand how viruses in the ocean are incredibly diverse in their genetics.

The backbone of what we know about ocean viruses is science done to help improve aquaculture practices and understanding.

Most of our knowledge has been driven by the economic consequences of viral disease and the protection of stocks of commercial fisheries or at-risk species. In the marine aquaculture industry, viral diseases can cause enormous losses in production and revenue.

It is remarkable that so many different pathogens can infect some already well-studied organisms, such as the panaeid shrimp, and that previously unknown viruses are still routinely discovered.

Some of these discoveries have been extraordinary; in the case of the white spot syndrome virus (WSS V), which infects panaeid shrimp, a new virus family has been recognized.

Similarly, viruses that infect commercially significant finfish have been intensively studied, and have been found to encompass a wide range of viral families, including rhabdoviruses, birnaviruses, nodaviruses, reoviruses and herpesviruses.

Source: Suttle, C (2007). Marine Viruses – Major Players in the Global Ecosystem. Nature Reviews Microbiology 5: 801–812.

The science of virology is relatively new and there is literally an ocean full of trillions of viruses to discover. But while the science is advancing, the public’s understanding of how viruses work is not. People only generally understand how viruses work in human populations, and their knowledge is usually limited to seasonal flu outbreaks and to what they see in popular films such as “Contagion.”

Because few people think of viruses except when they make them really, really sick, viruses are synonymous with scary and dangerous. It’s only natural that critics of aquaculture, particularly salmon farming, will present marine viruses as scary and dangerous, because like the tagline for “Contagion” says, “Nothing Spreads Like Fear.”

Nothing spreads like fear. Except misinformation about salmon farming.

Since last year, here in B.C. critics have been fixated on the idea that viruses from salmon farms could harm wild salmon. They have backed up their claims with science that is poor at best, and nonexistent most of the time, relying on speculations and a gullible, sensationalist media to get their message out.

However, although we strongly disagree with their conclusions, messages and methods, their underlying concerns are valid. We all want to see wild salmon thrive forever and we should make sure human activities such as farming fish in the same waters do no harm, or at the very least, pose no threat to the future of wild salmon.

The problem is, their argument is fallacious.

Farmed fish are put into the ocean virus and disease-free, because farmers want them to live a good, healthy life and because farmers want as many of their fish to survive as possible. It costs a significant amount of money just to grow salmon to smolt size, so farmers want to make sure their investment stays healthy to harvest.

But diseases are inevitable because the ocean is full of viruses. Wild salmon and other fish carry many parasites and diseases and viruses; this is normal, and it’s normal that farmed salmon will catch these diseases and parasites, too.

IHN virus, which is carried naturally by wild salmon but can be fatal to farmed salmon, seen through an electron microscope.

And as described above, diseases and parasites cause financial loss in aquaculture. This threat has prompted a vast amount of science investigating diseases found in aquaculture.

But what about the wild fish? The fact is, few people bothered investigating diseases and viruses in wild fish much in the past. The fish kept coming back and no one cared much, or knew much, about fish diseases.

When salmon enhancement programs became bigger and more common in the 1950s, scientists started noticing disease outbreaks among hatchery fish and started understanding that fish could carry and spread viruses, too. The traditional solution to the high mortality of wild salmon since the 1950s hasn’t changed much; it’s been a “brute force” approach, pumping out larger numbers of hatchery fish in the hopes that more will survive and return to spawn. Trying to increase their survival rate through vaccinations at enhancement hatcheries is too expensive and could actually be a big risk for hatchery fish, stressing them out just before they are released into the river, where they must struggle to survive.

Hatcheries are aquaculture, growing salmon the same way farmers do for the first part of the salmon’s lives.

Scientists continue to study diseases in wild salmon enhancement hatcheries, and their discoveries have contributed a great deal to what we know about ocean viruses.

Here’s where we need to point out that hatcheries are aquaculture. They grow fish from eggs, feed them and care for them, just like salmon farmers do.

If it wasn’t for aquaculture, in enhancement facilities and in private farms, we really would know next to nothing about marine viruses and diseases. We’ve only just begun to learn and understand what kinds of viruses are out there in the wild, natural ocean.

We shouldn’t be surprised when we start finding viruses in wild fish which have been observed in the past in aquaculture fish. After all, farmers found them first.

And we should be very careful not to fall into the correlation/causation trap. Just because one thing follows another, does not mean they are at all related.

And in the case of viruses in the ocean, so far on the Pacific Coast, science shows that there are a lot of viruses which occur naturally, and which affect both farmed and wild fish.

So the next time you read about viruses in the ocean, remember that it’s thanks to aquaculture that we know as much as we do. And hopefully we will continue to learn more, and find even better ways to both farm fish and protect the wild fish in our ocean.

 

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2 thoughts on “Thank aquaculture for ocean virus knowledge”

  1. Good article. Its also worth mentioning that we humans are also infected with a wide array of viruses that do no harm- we each are infected by many strains of cold and flu viruses for example. The anti-fish farmers could quite rightly claim: “95% of humans are infected with deadly flu virus”. Same goes for all animals.

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