Unexpected fish and squid found in the Central Arctic Ocean

Date:
February 18, 2022
Source:
Stockholm University
Summary:
Single individuals of Atlantic cod and squid occur much further
north than previously expected. Scientists have found fish and
squid in deep water in the middle of the Arctic Ocean.



FULL STORY ========================================================================== Single individuals of Atlantic cod and squid occur much further north
than previously expected. Scientists participating in the international
MOSAiC expedition with research icebreaker Polarstern have found fish
and squid in deep water in the middle of the Arctic Ocean. The results
from Stockholm University, the Alfred Wegener Institute and colleagues
in the European Fisheries Inventory in the Central Arctic Ocean (EFICA) Consortium are published today in the scientific journal Science Advances.


========================================================================== Small fish occur at very low abundances in the 200-600 m deep Atlantic
water layer of the Amundsen Basin as shown by the unique hydroacoustic
dataset collected by the EFICA Consortium that showed a "deep scattering
layer" (DSL) consisting of zooplanktion and fish along a 3170 km long
track of the MOSAiC expedition.

Therefore, it was a big surprise when suddenly four larger fish were
caught at 350-400 meters of depth. An even bigger surprise to the research
team was that three of the fish were Atlantic cod, a predatory species
that is not supposed to live this far north and, being a coastal fish, not
in an four kilometers deep ocean basin more than 500 kilometers away from
any coastline. With a deep- sea camera deployed underneath the sea ice,
the scientists also discovered that Atlantic armhook squid and Atlantic lanternfish occur much further north than previously known.

The Atlantic cod originated from Norwegian spawning grounds, and had
lived in Arctic water temperature (-1 to 2 oC) for up to six years
laboratory analyses showed. The fish preferred the Atlantic water layer,
a slightly warmer water mass (0-2 oC) that reaches far into the Arctic
basin in-beteen the surface and deeper water layers which are below 0 oC.

"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," says Pauline Snoeijs Leijonmalm, coordinator of the EFICA Consortium and professor
in marine ecology at Stockholm University.

New insights in the functioning of the pelagic food web The study thus
adds a new trophic level to the pelagic food web of the central Arctic ecosystem -- that of large predatory fish and squid. Together with the
smaller fishes in the DSL, continuous immigration of larger Atlantic
fish contributes to potential food for mammals since seals and walrus
can dive down to the Atlantic water layer.



==========================================================================
"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,"
says biologist Dr. Hauke Flores, Alfred Wegener Institute.

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

"During the short productive season of the polar day the DSL will remain
in the deeper part of the Atlantic water layer 24 hours per day, even
when the sea ice disappears, because this process is regulated by the availability of light" says Pauline Snoeijs Leijonmalm.

No harvestable fish stocks Based on their scientific results, the authors
of the new paper in Science Advances conclude that -- at least in the
Eurasian Basin -- there are no harvestable fish stocks today or in the
near future.



========================================================================== "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 doubt rather limited,"
says Pauline Snoeijs Leijonmalm.

Pauline Snoeijs Leijonmalm stresses that it is of great importance
that this fragile but fully functional ecosystem will receive robust international protection similar to Antarctica.

International agreement prevents commercial fishing Global warming
strikes the Artic region harder than the rest of the globe and climate
models predict that the opening up of the Central Arctic Ocean for non- ice-breaking vessels is just a matter of decades. Since most of the
area consists of high seas -- international waters outside national jurisdictions - - possible future human activities here are debated at
national and international political levels.

"Usually, exploitation of newly accessible natural resources tends to
precede scientific research and management measures, and internationally
shared fish stocks in high seas are especially prone to overexploitation,"
says Pauline Snoeijs Leijonmalm.

Taking a precautionary approach, Canada, China, Greenland (Kingdom of
Denmark), Iceland, Japan, Norway, Russia, South-Korea, the USA and the
European Union negotiated the Agreement to Prevent Unregulated High Seas Fisheries in the Central Arctic Ocean (CAO) that entered into force on
25 June 2021. The ten partners of the Agreement will soon be launching
a large Joint Scientific Research and Monitoring Program to collect new
fish and ecosystem data in the Central Arctic Ocean. The EU has already
started this work by financing the EFICA Consortium's ecosystem research
on the MOSAiC expedition (2019-2020), and the Synoptic Arctic Survey
expedition with the Swedish icebreaker Oden (2021).

The new paper in Science Advances is the first scientific paper presenting
new field data in the context of the 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," says Pauline Snoeijs Leijonmalm.

========================================================================== Story Source: Materials provided by Stockholm_University. Note: Content
may be edited for style and length.


========================================================================== Related Multimedia:
* Expedition_MOSAiC_to_the_Arctic;_Atlantic_cod_and_squid ========================================================================== Journal Reference:
1. Pauline Snoeijs-Leijonmalm et al. Unexpected fish and squid in the
central Arctic deep scattering layer. Science Advances, 2022 DOI:
10.1126/sciadv.abj7536 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220218153033.htm

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