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Searched for fish in the Arctic Ocean: “It was completely empty”
Researchers have investigated what lives in the waters of the Arctic Ocean.
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Researchers at the Norwegian Polar Institute and the Fram Centre have been on an expedition from Svalbard to the North Pole.
Along the way, they mapped the occurrence of fish and other marine animals using echo sounders and trawling.
The researchers summarised their findings in a study published in Communications Earth & Environment.
They had expected to find at least some fish in the Arctic Ocean, down to 500 metres below the surface. But there was little to find.
“When we reached the cold, deep waters, there was nothing there. It was completely empty of fish,” says Haakon Hop.
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The researchers were on an expedition in the Arctic Ocean with the research vessel Kronprins Haakon in the late summer of 2022 and 2023.
The voyage took them from the continental shelf north of Svalbard and out into the Nansen Basin and the Amundsen Basin in the Arctic Ocean.
The plan was to deploy two rigs to measure hydrographic conditions such as current, temperature, and salinity.
Along the route, samples were collected to map the occurrence of fish and other small animals.
The researchers used echo sounders that send sound waves into the ocean. They used different frequencies to detect fish and smaller zooplankton.
At the same time, trawling was carried out to determine which species were present in the open water masses. The trawl is specially adapted for trawling in openings in the sea ice.
Capelin and cod
“As soon as we moved north of the continental slope near Svalbard, the fish disappeared,” says Hop. “We had expected that we would at least find some fish in the Arctic Ocean.”
Outside Svalbard, the catch was dominated by capelin.
“Capelin spread quite far into the area north of Svalbard, along the continental slope. And since cod eat capelin, there were also some cod along the shelf edge,” he says.
Then the capelin and the cod disappeared.
What remained were juvenile fish that had been carried out by ocean currents.
The researchers found juvenile beaked redfish, juveniles and larvae of capelin, small Greenland halibut measuring three to four centimetres, and some juvenile polar cod.
Lanternfish
The researchers thought they would find mesopelagic fish in the Arctic Ocean. These are fish that live in the middle sea depths, usually 300 to 400 metres below the surface, and are called lanternfish.
“They are found north of Svalbard, in the Southern Ocean, and really all the world's oceans,” says Hop.
The researchers did catch some lanternfish in the trawl, and this was the species found farthest north.
But after the research vessel crossed 82 degrees north, these also disappeared. The vessel had then entered the deep Nansen Basin.
“It was surprisingly empty, and there was very little zooplankton as well,” he says.
Jellyfish and small animals
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After passing 82 degrees north, the team caught some crustaceans, krill, jellyfish, squid, and ten-centimetre-long arrow worms, but no fish.
They also used plankton nets to catch smaller zooplankton that existed in low densities.
In the Amundsen Basin, closer to the North Pole, there was even less life.
The researchers did, however, observe polar cod darting up to the surface as the ship broke through the ice.
Saw polar bears and ringed seals
The reason the Arctic Ocean is so empty is because the season during which plankton is produced is so short, says Hop.
There is also a lack of nutrients, which act as fertiliser for the algae. That means there is little food for zooplankton to graze on, and few zooplankton for fish.
Even though fish were scarce, the researchers observed seals and polar bears all the way up to the North Pole.
That is because the animals are part of an ecosystem linked to sea ice, says Hop.
“This ice-associated ecosystem is based on the production of ice algae. These are algae that grow as a brown layer beneath the ice, and the species Melosira arctica hangs down like curtains,” he says.
The algae provide nourishment for crustaceans and zooplankton. That creates a food source for young polar cod that live in cavities in the ice.
Crustaceans and polar cod are food for ringed seals, which in turn are the primary prey of polar bears.
“It's a food chain that exists around the ice, but is disconnected from what happens in the water masses,” Hop says.
Can forget about fishing plans
The study showed a negative result, according to Hop.
“We tried to determine whether there were fish in the Arctic Ocean and have shown that there are almost no fish there,” he says. “That means plans to fish in the Arctic Ocean can mostly just be forgotten. At least as long as there's ice and cold water masses there.”
There is already an agreement in place, the CAO Fisheries Agreement, which came into force in 2021 and prohibits fishing in the Arctic Ocean for 16 years.
"An important contribution"
Marit Reigstad is a professor of marine ecology at UiT The Arctic University of Norway.
She says it's important to document what lives in the waters of the Arctic Ocean.
“We have thought that the Arctic Ocean is nutrient-poor, but at the same time people have seen signals on echo sounders. Documenting what actually exists in the deeper layers is part of the ongoing effort to gather knowledge about the Arctic Ocean,” she says.
“This has been difficult to study because of the ice. But as there becomes less ice, interest in the area is increasing, and it's becoming more accessible,” she adds.
As part of the CAO Fisheries Agreement, the countries committed themselves to learning more about resources and fish stocks in the Arctic Ocean, according to Reigstad.
“This study is an important Norwegian contribution and shows that there are very few fish and that the organisms present are largely jellyfish, crustaceans, and arrow worms,” she says.
Reigstad says the study supports earlier findings.
When researchers in the Nansen Legacy project trawled under the ice in 2021, they only caught seven fish.
Probably not going to be productive
Reigstad says the significance of the study is that it shows there may be good reason to continue the fishing ban in the area.
“There are many changes happening in the Arctic, with both climate change and increased human activity. Reducing the pressure on these areas as much as possible will be important,” she says.
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But could there be more fish in the Arctic Ocean as the climate warms?
“In general, fisheries are found on shelf areas and continental slopes, not only in the Arctic but also off the Norwegian coast,” she says.
Continental shelf areas are where the most food is available, according to Reigstad.
“In that sense, it's not surprising that most fish, crustaceans, and nutrients are found along the shelf slope west and north of Svalbard,” she says.
“This could spread farther east, but I don’t think any researchers believe that the central Arctic Ocean will become highly productive. The layered structure of the water masses will continue to restrict the flow of nutrients,” she adds.
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Translated by Nancy Bazilchuk
Read the Norwegian version of this article on forskning.no
Photo credits: Vegard Stürzinger, Google Earth, Haakon Hop
References:
Dodd et al. Barren depths from 82° N to the North Pole reveal scarcity of fish in the Central Arctic Ocean, Communications Earth & Environment, 2026. DOI: 10.1038/s43247-026-03381-7
Ingvaldsen et al. Under-ice observations by trawls and multi-frequency acoustics in the Central Arctic Ocean reveals abundance and composition of pelagic fauna, Scientific Reports, 2023. DOI: 10.1038/s41598-023-27957-x
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