Scientists in disbelief over discovery of world's largest fish-breeding area

Researchers estimate 60 million icefish are hanging out in one ocean region of Antarctica.

Amanda Kooser
Freelance writer Amanda C. Kooser covers gadgets and tech news with a twist for CNET. When not wallowing in weird gear and iPad apps for cats, she can be found tinkering with her 1956 DeSoto.
Amanda Kooser
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Icefish attend to nests in the Weddell Sea as part of a massive breeding colony.


Antarctica's hottest club is on the floor of the Weddell Sea, where all the cool icefish hang out. About 60 million of them. And they're there for a primal reason: making more icefish. 

The Alfred Wegener Institute (AWI) of the Helmholtz Centre for Polar and Marine Research in Germany announced the discovery of the world's largest known fish breeding area in a statement on Thursday. A team aboard the research vessel Polarstern found the mind-bogglingly massive icefish breeding colony while surveying the seabed with a camera system in February 2021. 

The Polarstern footage showed a seemingly endless expanse of icefish (Neopagetopsis ionah) nests. AWI described a sense of growing excitement and finally disbelief as the nests kept appearing. The researchers calculated an extent of 93 square miles (240 square kilometers) and an estimated population of 60 million fish. 

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The team published its findings in the journal Current Biology this week, describing the colony as having a "globally unprecedented extent." 

"The idea that such a huge breeding area of icefish in the Weddell Sea was previously undiscovered is totally fascinating," said AWI biologist Autun Purser, lead author of the study.

Each nest can contain 1,500 to 2,500 eggs guarded by an adult fish. Images and video from the seafloor show the distinctive round nests with their guardians in attendance. Using data from trackers, the researchers found the icefish colony is also a popular destination for seals that are likely making snacks of the residents.  

The researchers are urging the establishment of a regional marine protected area in Antarctica to prevent fishing or invasive research and preserve the extraordinary habitat.

Said AWI director Antje Boetius, who was not directly involved in the study, "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."