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“Spectacular Discovery” in Antarctica: Massive Icefish Breeding Colony With 60 Million Nests - SciTechDaily
Jan 14, 2022 3 mins, 18 secs

Researchers detect around 60 million nests of Antarctic icefish over a 240 square kilometers area in the Weddell Sea.

Near the Filchner Ice Shelf in the south of the Antarctic Weddell Sea, a research team has found the world’s largest fish breeding area known to date.

The density of the nests and the size of the entire breeding area suggest a total number of about 60 million icefish breeding at the time of observation.

These findings provide support for the establishment of a Marine Protected Area in the Atlantic sector of the Southern Ocean.

The joy was great when, in February 2021, researchers viewed numerous fish nests on the monitors aboard the German research vessel Polarstern, which their towed camera system transmitted live to the vessel from the seabed, 535 to 420 meters below the ship, from the seafloor of the Antarctic Weddell Sea.

Extrapolated to this area size, the total number of fish nests was estimated to be about 60 million.

“The idea that such a huge breeding area of icefish in the Weddell Sea was previously undiscovered is totally fascinating,” says Autun Purser, deep-sea biologist at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) and lead author of the current publication.

“After the spectacular discovery of the many fish nests, we thought about a strategy on board to find out how large the breeding area was — there was literally no end in sight.

We covered an area of 45,600 square meters and counted an incredible 16,160 fish nests on the photo and video footage,” says the AWI expert.

Based on the images, the team was able to clearly identify the round fish nests, about 15 centimeters deep and 75 centimeters in diameter, which were made distinct from the otherwise muddy seabed by a round central area of small stones.

Several types of fish nests were distinguished: “Active” nests, containing between 1,500 and 2,500 eggs and guarded in three-quarters of the cases by an adult icefish of the species Neopagetopsis ionah, or nests which contained only eggs; there were also unused nests, in the vicinity of which either only a fish without eggs could be seen, or a dead fish.

The result: the breeding area corresponds spatially with the inflow of warmer deep water from the Weddell Sea onto the higher shelf.

With its biomass, this huge breeding area is an extremely important ecosystem for the Weddell Sea and, according to current research, likely to be the most spatially extensive contiguous fish breeding colony discovered worldwide to date, the experts report in the publication in Current Biology.

After the MOSAiC expedition, German marine and polar research has once more reaffirmed its outstanding position.

Funding by the Federal Ministry of Education and Research (BMBF) provides German marine and polar research with one of the most state-of-the-art research vessel fleets worldwide.

Considering how little known the Antarctic Weddell Sea is, this underlines all the more the need of international efforts to establish a Marine Protected Area (MPA),” Antje Boetius classifies the results of the study, in which she was not directly involved.

A proposal for such an MPA has been prepared under the lead of the Alfred Wegener Institute and is defended since 2016 by the European Union and its member states as well as other supporting countries in the international Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR).

But now that the location of this extraordinary breeding colony is known, Germany and other CCAMLR members should ensure that no fishing and only non-invasive research takes place there in future.

So far, the remoteness and difficult sea ice conditions of this southernmost area of the Weddell Sea have protected the area, but with the increasing pressures on the ocean and polar regions, we should be much more ambitious with marine conservation.”.

Reference: “A vast icefish breeding colony discovered in the Antarctic” by Autun Purser, Laura Hehemann, Lilian Boehringer, Sandra Tippenhauer, Mia Wege, Horst Bornemann, Santiago E.A.

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