Fish are on the move - what about the fishermen?

With change in ocean temperature, fish and other marine species move towards the poles. PhD fellow Francesc Gordó Vilaseca at Nord University will present new research that shows major changes in the distribution and body size of marine species.

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PhD fellow Francesc Gordó Vilaseca at the Faculty of Biosciences and Aquaculture, Nord University, asks what changes fishermen must make as a result of warmer seas and fish species on the move. Photo: Lise Fagerbakk​​

On Wednesday August 24th at the Nor-Fishing 2022 fair in Trondheim, PhD fellow Francesc Gordó Vilaseca at Nord University in Bodø will present new research about how climate change and warmer seas affect the species of the sea, with an emphasis on the fish.

“Marine species are adapted to the temperatures that they normally experience. This means that when an area that was too cold for them becomes warmer, they can expand their distribution into that area. Also, when an area that was at their warm limits becomes warmer, they cannot live in that area anymore. As a result, we see that the number of species around the Equator has been decreasing in concert with climate change. This applies to all the species in the sea, including fish, mammals, birds and reptiles. Most of them move either north or south, towards the poles", Vilaseca explains.

Research published last year by his colleagues show that thousands of animal species, including fish and invertebrates, open water and seabed living, have been moving away from the equator since the 1950s.

Species diversity around Svalbard

New research not yet published shows that the number of fish species has doubled in Norwegian and adjacent seas since the 1990s, including in Arctic waters around Svalbard and the Barents Sea.

“The number of species around Svalbard and the northern parts of the Barents Sea has approximately doubled during the last 25 years. This affects both fishermen and the fisheries because it tells us something about how and what we have to fish in the future", he says. “When we compare the temperature preferences of the fish from research with fishery catch data, we can see that the fisheries are not adapting to the changing fish species abundances ".

There is basically an increase of species coming from southern latitudes, with several Arctic species declining, and some of them also increasing.

Warmer seas also cause other changes.

“We know from previous research that warmer temperatures reduce the length of the fish. At the same time, the fish grow faster. This varies from species to species. However, species that live in very cold water, can increase their length with small increases in temperature, which could be the case for  the Greenland halibut,. The conclusion is that warmer seas could have a positive effect on some Arctic species, while others shrink in size."

The Norwegian cod is also expanding northwards, because a warmer Arctic is not too cold for this species anymore.

“The coastal cod in Norway tolerates a wide variation in temperature, so we believe it will still be in Lofoten and Vesterålen. The historical problem with this species lies not in the sea temperature, but in the extent of fishing", says Vilaseca.

Protection for more research

Nevertheless, the changes are so big that fishermen and fisheries have to adjust.

“I am going to Nor-Fishing 2022 to present the latest research on the area and to discuss with the fishermen about how all of us should adapt for the future. I also want to hear about any changes they experience, and any questions that they may come up with", he says.

Vilaseca and his colleagues at Nord University want to find out more about the changes they now see.

“The question is whether change in species diversity and size of organisms is a result of fishing or an effect of climate change and warmer seas. The only way to distinguish these processes is to have some “reference" areas where there is no fishing, but where climate change will have effects. Then we can compare fished and non-fished areas to see if there are changes in fish species' abundance that are the same and likely due to climate change, or only in fished areas and thus related to direct or indirect (food web) effects of fishing. This is a matter I would also like to discuss with fishermen, fisheries and the industry", says Vilaseca.

Vilaseca's lecture “Biological Effects of Climate Warming on Arctic and Global Fisheries" can be heard on Wednesday August 24th at 1.30 pm.