science
The Edible Crab Keeps Moving Northwards
This summer, researchers at the Norwegian Institute of Marine Research found edible crab as far north as Skjervøy in Troms, Northern Norway. “The edible crab is clearly not finished exploring new areas,” says researcher Johanna Marcussen.
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Crab populations in Troms, Northern Norway, are currently being mapped through the Institute of Marine Research's research project "Crabs on the Move" (2023-2027).
During a survey this summer, the researchers caught edible crab off Skjervøy in northern Troms.
"That is further north than we have previously recorded the species in our ongoing crab mapping. The edible crab is clearly not finished exploring new areas," says researcher and survey leader Johanna Marcussen in a press release.
As a result of climate change and ocean warming, the edible crab is one of the species moving northwards.
Meeting the red king crab
In the project, the researchers are studying, among other things, how edible crabs and red king crabs are moving closer to one another. While the edible crab is heading northwards, the red king crab is moving westwards and southwards from Finnmark.
"In 2023 and 2024, we found many edible crabs in southern Senja, and the catches were on a par with catches in Vestland, Møre and Trøndelag. Further north, by Vannøya, we found only individual specimens of the edible crab. This year’s survey shows that it is continuing to spread northwards," Marcussen says.
The survey was carried out on board the research vessel Ingrid Alexandra in cooperation with the Norwegian Directorate of Fisheries’ sea service.
Using various methods
In the hunt for crabs, the researchers used both traditional crab pots and baited video rigs. In addition, they use environmental DNA to search for traces of the crabs. In short, this involves finding crab genes (DNA remnants) showing that the species has been present in the area.
Data from the project will be used in modelling species distribution for several crab species, and will form the basis for stock indicators for crabs in what is an important area for the fisheries and aquaculture industries.
The researchers are also collecting data on underutilised resources such as whelks, shore crabs, sea cucumbers and sea urchins.
Seeking tips from the public
Although this project’s northernmost recording of edible crab is at Skjervøy, the species has previously been recorded by the Institute of Marine Research in Loppa municipality in western Finnmark. Fishers have also reported findings of the crab in Finnmark.
Marcussen would like people to join the search for the country’s northernmost edible crab and encourages anyone who has seen the species in North Troms or Finnmark to report it to the institute on the website Dugnad for havet.
"If we are to get a more precise picture of how far north the crab has come, we depend on help from people who travel along the coast and fish here more often than once a year," she says, and continues:
"Every observation helps to draw a better map of the crab’s northward migration. Citizen science is an important part of our toolbox, and can be combined with traditional methods and with new methods that were tested during this year’s survey."
