A big surprise for researchers when they found unexpected fish and squid in the central Arctic Ocean

The research team finds Atlantic cod in the Arctic Ocean. Credit: UFA Show & Factual, Germany

Single specimens of cod and squid are found much further north than previously thought. Scientists involved in the international expedition MOSAiC with the research icebreaker Polarstern, found fish and squid in deep water in the middle of the Arctic Ocean. The results of Stockholm University, the Alfred Wegener Institute and colleagues from the Consortium of the European Fisheries Inventory in the Central Arctic Ocean (EFICA) published today (February 18, 2022) in a scientific journal Advances in science.

Small fish are found in very small numbers in the 200-600-meter Atlantic water layer of the Amundsen Basin, as shown by a unique set of sonar data collected by the EFICA consortium that showed a “deep scattering layer” (DSL) consisting of zooplankton and fish along. the route of the MOSAiC expedition is 3170 km long.

So it was a big surprise when suddenly at a depth of 350-400 meters caught four larger fish. An even bigger surprise for the research team was that the three fish were Atlantic cod, a predatory species that should not live so far north and, being a coastal fish, is not located in a four-kilometer ocean basin more than 500 kilometers. from any coastline. Using a deep-sea camera deployed under sea ice, the scientists also found that the Atlantic squid and the Atlantic lanternfish meet much further north than was previously known.

Armhook Squid Fish Cam

A squid-pond in the Arctic Ocean, spotted by an expedition camera. Credit: EFICA consortium

Atlantic cod originated in Norwegian spawning grounds and lived at Arctic water temperatures (-1 to 2). Fr.C) up to six years showed laboratory tests. The fish preferred the Atlantic water layer, a slightly warmer water mass (0-2 Fr.C) reaching far into the Arctic basin between the surface and deeper layers of water below 0 Fr.S.

“So even if cod doesn’t have its own central Arctic reserve, this study shows it can survive. Few people seem to find enough food to stay healthy for longer, ”said Pauline Snois Lejonmalm, coordinator of the EFICA consortium and professor of marine ecology at Stockholm University.

New ideas in the functioning of the pelagic food network

Thus, the study adds a new trophic level to the pelagic food network of the central Arctic ecosystem – large predatory fish and squid. Along with the smaller fish in the DSL the continuous immigration of large Atlantic fish contributes to potential food for mammals as seals and marjoram can dive into the Atlantic aquifer.

“The presence of small and even larger fish in the Atlantic water layer may explain why seals, marjoram and polar bears can be found even at the North Pole. There are very few fish and mammals, but they are there, ”said biologist Dr. Hauke ​​Flores of the Alfred Wegener Institute.

Pauline Snois Leyonmalm

Pauline Snois Leyonmalm. Author: Esther Horvat / AWI

A new study also found that vertical DSL migration is absent during polar night, six months of continuous darkness (DSL at 100-250 m) and polar day, six months of continuous light (DSL at 300-500 m). This means that the flow of carbon from shallower water to deeper through daily vertical DSL migration is hampered in the Central Arctic Ocean compared to all other oceans.

“During the short harvest season of the polar day, DSL will remain in the deeper part of the Atlantic water 24 hours a day, even if the sea ice disappears, because this process is regulated by the availability of light,” says Pauline Snois. Leionmalm.

No fish stocks

Based on their scientific findings, the authors of a new article in Science Advances conclude that – at least in the Eurasian Basin – there are no fish stocks that could be harvested, neither today nor in the near future.

“This was expected because the Central Arctic Ocean has a very low concentration of nutrients and very low biological productivity. Even if more Atlantic fish and their prey are attracted by the influx of water from the Atlantic Ocean, the ability of the Central Arctic ecosystem to maintain large fish stocks is undoubtedly quite limited, ”says Pauline Snois Leyonmalm.

Pauline Snois Leyonmalm emphasizes that it is important that this fragile but fully functional ecosystem be given strong international protection, similar to Antarctica.

An international agreement bans commercial fishing

Global warming is hitting the Arctic harder than the rest of the globe, and climate models predict that the discovery of the Central Arctic Ocean for non-ice ships is just a matter of decades. Since most of the territory consists of the high seas – international waters beyond national jurisdiction – possible future human activities are discussed here at the national and international political levels.

“Usually, the exploitation of new available natural resources is usually preceded by scientific research and management measures, and international fish stocks on the high seas are particularly prone to overexploitation,” says Pauline Snois Leionmalm.

Following the warnings, Canada, China, Greenland (Kingdom of Denmark), Iceland, Japan, Norway, Russia, South Korea, the United States and the European Union negotiated. Agreement on the Prevention of Unregulated Fisheries on the High Seas in the Central Arctic Ocean (CAO) which entered into force on 25 June 2021. The ten partners of the agreement will soon launch a large Joint research and monitoring program to collect new data on fish and ecosystems in the Central Arctic Ocean. The EU has already started this work by funding the EFICA ecosystem research consortium on the MOSAiC expedition (2019-2020) and the Synoptic Arctic Survey expedition with the Swedish icebreaker Oden (2021). The new work in Science Advances is the first scientific work to present new field data in the context of an agreement.

This agreement prevents any commercial fisheries for at least 16 years and puts “science first”, ensuring scientific assessments of the state and distribution of possible fish stocks in the Central Arctic Ocean and the ecosystem that supports them – a wise political decision and a good start on the road to full protection, ”says Pauline Snois Leyonmalm.

Reference: “Unexpected fish and squid in the central Arctic deep scattered layer” February 18, 2022, Advances in science.
DOI: 10.1126 / sciadv.abj7536 A big surprise for researchers when they found unexpected fish and squid in the central Arctic Ocean

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