MARINE HEATWAVES MULTIPLY PROBLEMS WITH SALMON FARMING

Marine heatwaves multiply problems with salmon farming.

Article in Dagens Næringsliv February 25:  The sea is getting warmer – it causes even bigger problems for both farmed salmon and the environment.  

Author: Nils Gunnar Kvamstø, Director of Marine Research, and Mari Skuggedal Myksvoll, Research Manager for Environmental Effects of Aquaculture.

Last summer we got a taste of it. A marine heat wave started in Western Norway in June and spread northward. In late summer, the heat reached Troms and Finnmark.

The heat record didn’t come alone. Never before have so many sea lice been recorded on wild fish in the northernmost counties.

High temperatures put lice on steroids, making them grow faster, more prolific, and more contagious.

Salmon lice feed on salmon – and thrive in fish farms.

From there, the female lice release “baby lice” into the open water bodies – where wild salmon, sea trout and char become infected.

In the worst-affected areas, up to 30 percent of the salmon smolt that migrate out of the rivers die annually.

Unfortunately, it’s not just sea lice that like the southern heat.

In recent years, the pearl oyster jellyfish has been a regular visitor to our coast, breaking into stinging pieces when it crashes into a salmon cage.

This has resulted in a lot of dead or injured farmed fish that have to be euthanised. The pearl jellyfish has become a welfare problem for the fish and is a drain on the farmers’ purse strings.

We don’t really know why this jellyfish has suddenly become so common along our coast. But higher temperatures and increased inflow into our oceans are one of the theories. 

We have also seen cases of harmful algae blooms in recent years. Although it is not necessarily due to warmer water, we cannot rule out that climate change has a hand in it.

And as ocean temperatures rise, fish have weaker immune systems. They become more susceptible to both viral and bacterial infections. New diseases can also come as stowaways on exotic species that find their way here.

Warmer water also becomes lighter, and the replacement of the bottom water in the fjords occurs less frequently. This means that we get less oxygen in the fjord basins. The fjords are less equipped to withstand additional stress, such as emissions from fish farming. Climate change may therefore mean that the aquaculture industry must switch to zero-emission cages or move out of sheltered areas.

The risk of salmon escapes also increases as extreme weather becomes more common.

All the problems with salmon farming are largely made worse by the temperature wildcard. So how big a temperature change is needed before we see these effects?

Since 1935, we have seen an increase of 2 degrees in the average temperature of the water along the Norwegian coast. And we are already seeing the start of the problems.

By 2100, we assume that the temperature will be another 1-3 degrees higher than today. 

What we now call a marine heat wave may then be the new normal.

When we see what awaits us, it should have consequences for how the aquaculture industry adjusts. It is our impression that farmers are taking the climate risk seriously – but they must speed up the transition for their own sake and the sake of the environment. It is quite clear that climate change is challenging the traditional way of farming. This will place greater demands on technological development both to protect the fish in the cages and the environment outside. 

We marine scientists will also contribute with the knowledge needed. The coast is long and stretches across several climate zones. Solutions that work in sheltered fjords in the south are not necessarily right in weather-exposed fjords in the north. We need a whole toolbox of solutions combined with local knowledge.

Today, we contribute research into new cage technology, early warning of algae and jellyfish, the placement of facilities in relation to currents, and sea lice infestation, to name a few.

But we can all work more purposefully on climate adaptation. A changing ocean is not waiting for us to find the right solutions.

Photo credit: Institute of Marine Research

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