Unexpected Fish and Squid Encountered in the Central Arctic Ocean

The investigators taking part in the global MOSAiC expedition with the Polarstern icebreaker survey have discovered fish and squid in deep water in the mid-Arctic Ocean.

Suddenly four very large fish were captured at a depth of 350-400 meters. An added shock to the research study group was the fact that three of the fish were Atlantic cod. The Atlantic Cod is a predatorial species not meant to be living that far north and, being a coastal fish, not in four kilometers deep in the ocean basin more than 500 kilometers from any shoreline. By utilizing a deep-sea camera that was released below water ice, the investigators also found that Atlantic squid and lanternfish appear much farther north than was recently known

Well, although Atlantic cod do not have their own main supply, this research shows that they can continue to survive. A small group of individuals seems to discover enough food to stay healthy longer,” Pauline Snoeijs Leijonmalm, Coordinator of the EFICA Consortium and professor at Stockholm University, says..

New knowledge on how the pelagic food web works

The new study adds a full new trophic degree to the pelagic food web of the central Arctic ecosystem. Besides the smaller fish in the DSL, the ongoing migration of larger fish from the Atlantic contributes to the possible food for mammals, since seals and walruses can dive down to the Atlantic water layer.

Throughout the brief season of the producing polar day, the DSL will be kept in the innermost part of the Atlantic water layer 24 hours a day, including when the sea ice has disappeared, because the constant presence of light generates this process.

_{There is no fish supply for harvesting}

From their scientific results, the contributors to the new article in Science Advances concluded that – at the very minimum in the Eurasian basin – no harvestable fish supply is available today or in the immediate future.

This would be expected considering that the Central Arctic Ocean has lower nutrient connections and a very low biological production. Still, although more Atlantic fish and their prey would surely come from the Atlantic Ocean, the capacity of the Central Arctic Ocean ecosystem to support larger fish stocks is undoubtedly rather constrained.

International agreement avoids commercial fishing

Global warming is affecting the Arctic region more strongly than the rest of the globe, and climate models are predicting that the further opening of the Central Arctic Ocean to non-ice-breaking vessels is only a question of many decades.

Typically, the exploitation of recently accessible natural deposits tends to come first before science research and management action, and internationally divided deep-sea supplies of fish are in particular susceptible to being overexploited,” notes Pauline Snoeijs Leijonmalm.

Following a preventive implementation policy, Canada, China, Greenland (Kingdom of Denmark), Iceland, Japan, Norway, Russia, South Korea, the USA and the European Union discussed the Agreement to Prevent High Seas Overfishing in the Central Arctic Ocean (CAO) that became effective on June 25, 2021. The ten Agreement members will promptly launch a massive Joint Scientific Research and Monitor Program to gather new information on fish and ecosystems in the Central Arctic Ocean.

The arrangement prohibits any viable trade fisheries for at least 16 years, and puts “scientific investigation at the beginning”, warranting scientific assessments of the status and movement of potential fish populations in the Central Arctic Ocean and the surrounding ecosystem that sustains them – a prudent policy choice and a great start towards full implementation of the protection

Read the original article on Science Daily.

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Reference: Pauline Snoeijs-Leijonmalm et al. Unexpected fish and squid in the central Arctic deep scattering layer. Science Advances, 2022 DOI: 10.1126/sciadv.abj7536