Atlantic cod and squid were found further north than expected, according to a study published in the scientific journal Science Advances. Scientists from the international MOSAiC expedition with research icebreaker Polarstern spotted cod and squid in deep waters in the middle of the Arctic Ocean.
Typically, small fish are not very abundant in the 200-600 m deep Atlantic water layer of the Amundsen Basin. It was a big surprise for the research team from Stockholm University when they caught four large fish at 350–400 meters of depth. Three of them were Atlantic cod, which is not supposed to live this far north and more than 500 km from any coastline. With a deep-sea camera, the scientists also found Atlantic armhook squid and Atlantic lanternfish much further north than previously known.
Analyses showed that the cod came from Norwegian spawning grounds and had lived in Arctic waters for up to six years. “So, even if the Atlantic cod does not have its own central Arctic stock, this research shows that it can survive. A small number of individuals seem to find enough food to stay healthy for a longer time,” said Pauline Snoeijs Leijonmalm, coordinator of the EFICA Consortium and professor in marine ecology at Stockholm University.
The study added a few extra players in the food chain in the central Arctic ecosystem. The team believes this provides potential food for mammals since walrus and seals can dive down to find these cod. “The availability of small and even some larger fish in the Atlantic water layer could explain why seals, walrus, and polar bear can be found even at the North Pole. Both fish and mammals are very few, but they are there,” said Dr. Hauke Flores, Alfred Wegener Institute.
Despite finding some cod, the authors concluded that the amount of fish in this area is not enough to be fished. In contrast, they stress that this is a fragile ecosystem that should receive international protection similar to Antarctica.
“This was expected because the Central Arctic Ocean has very low nutrient concentrations and very low biological productivity. Even if more Atlantic fish and their prey would be advected with the water inflow from the Atlantic Ocean, the capacity of the Central Arctic Ocean ecosystem to support larger fish stocks is without a doubt rather limited,” said Leijonmalm.
Global warming affects the Arctic region more than the rest of the globe, and climate models predict that vessels can easily reach the Arctic Ocean in a matter of decades. As most of the area is classed as international waters outside national jurisdictions, it is essential to discuss how human activities will be regulated in the future.
As a precaution, Canada, China, Greenland, Iceland, Japan, Norway, Russia, South Korea, the USA, and European Union negotiated the Agreement to Prevent Unregulated High Seas Fisheries in the Central Arctic Ocean (CAO), which entered into force on 25 June 2021. This study is the first to present new data in the context of this agreement.
“This agreement prevents any commercial fishing for at least 16 years to come, and puts “science first,” warranting scientific assessments of the status and distribution of possible fish stocks in the Central Arctic Ocean and the ecosystem supporting them – a wise political decision and a good start towards full protection,” said Leijonmalm.
(1) Leijonmalm P, Flores H, Sakinan S et al (2022) Unexpected fish and squid in the central Arctic deep scattering layer. Science Advances, DOI: 10.1126/sciadv.abj7536