tromsø, nor – it’s near impossible to go out to eat in tromsø, the second biggest city north of the arctic circle and not see fish on the menu. one of the most popular types of fish served in norway, a country known for its seafood, is salmon. and with exports valued at more than $15 billion per year, it’s a fish that norway now provides for dinner tables the world over. 

salmon is one of the most-farmed fish in norway’s aquaculture industry, which works by raising fish offshore in large open-net pens. norway’s salmon farms produce the highest amount of farmed salmon in the world at about 1.2 million tonnes each year. 

but tiny organisms known as “sea lice” are infecting farmed salmon populations at high levels. 

for the salmon industry, “sea lice is the number one problem here in norway,” said jelena kolaveric, a professor and researcher at the arctic university of norway in tromsø. 

a growing problem for arctic salmon farms

first prevalent in salmon farms along the southern coast of the country, the lice have spread to affect farms along the northern coast. and the climate change connection is clear: warmer water temperatures allow sea lice to reproduce faster. so as northern waters rise in temperature, even just a few degrees, the problem is spreading into the arctic.

monica eide, a community contact for gratanglaks, a salmon farming company based in the grantangen municipality in troms, norway, said this summer was particularly bad for salmon farms in northern norway.  

“we had a marine heat wave in the arctic this summer, and the temperature increased by 4-5 degrees,”  said elisabeth ytteborg, a senior researcher at nofima, whose research focuses primarily on climate change impacts to aquaculture. all that heat, says ytteborg, has led to “a sea lice explosion in the north”

but the process of fighting off the lice has its own challenges. the salmon farming industry in norway, and across the world, has received criticism for some of its negative environmental impacts. these include dumping chemicals into the oceans to get rid of the lice, diseases spreading to wild salmon populations, and farmed salmon escaping and interbreeding with wild salmon.  

delousing: harder than it looks

a longstanding method of treating the lice is to take the salmon out of the sea, remove lice in tanks on land, and return the salmon to their offshore pens. but this method isn’t ideal. 

“we’re hoping to find a system where we don’t have to take them up because that’s stressing the fish,” said eide. “what we really would like to do is to get rid of lice without handling the fish that much, without taking it out from the sea.” 

another, more recent method, which is employed at gratanglaks, is to use lasers to detect lice, and once detected, the lasers shoot at the lice to kill them off one by one. according to kvaroy arctic, a salmon farming company, the salmon aren’t hurt by the process. however, individually killing off the lice is time consuming. 

kolaveric’s research aims to address some of those environmental concerns with salmon farming. what if salmon farming could be done in tanks on land kept free of sea lice or other pathogens?  her research is primarily on recirculating aquaculture systems (ras). this is a relatively new type of technology where seawater is recycled and reused to produce salmon in water tanks on land. a challenge this system faces is that trying to replicate on land the ecological needs the salmon receive from ocean water can be expensive and energy intensive. however, kolaveric hopes it will push the industry forward to a more sustainable method of salmon production. 

“these recirculation systems, they give you an opportunity to better control the environment, and also give you flexibility,” said kolaveric. “because in a ras system, you can adjust your temperature, you can adjust your oxygen.” that control, she says, can prevent lice from infesting the pools. 

seeking holistic solutions

ytteborg emphasizes that it’s important to keep in mind that the fish aren’t solely affected by rising temperatures, but also the various stressors associated with salmon farming in general, such as viruses, bacteria and parasites. there is also the stress coming from the production itself, vaccinations, transportation and treatment. 

she emphasizes the value in doing more research to try to understand how a fluctuating environment will affect the fish on top of other stressors.  

“we need to work more trans-sectoral. biologists like me need to work with the climatologists to understand how the environment will change and how it may impact the animals, and then we need to work with the industry to see what kind of measures they have and what kind of procedures they do,” said ytteborg. “and then it’s not like one size fits all because climate change will affect one area very differently from another one and different strategies are needed.” 

eide, whose company aims to find more sustainable methods of lice treatment and salmon production, highlights the relationship between salmon farmers and the fish themselves. 

“we want them to be healthy, we want them to have a good time. we don’t want to hurt them, but there’s also a lot of things happening in the industry that aren’t good,” said eide. “not all of us are aware of what we’re doing to the fish so i think we have a lot of things that we could be better on, and i think we should be open about that too.”