Oceans cover about 70% of the Earth’s surface, and only 20% of the seafloor has been mapped in detail, making the sea one of the most mysterious places on Earth. Research expeditions on boats continue to discover more about the complex ecosystems found within the ocean. Recently, scientists from the Alfred Wegener Helmholtz Centre for Marine and Polar Research in Germany and colleagues discovered the largest fish breeding colony known to date in the Antarctic Ocean.

Scientists aboard the RV Polarstern research vessel captured images of thousands of icefish nests in the cold waters of the Antarctic Ocean. They estimate that over an area the size of about 100 square miles, there are over 60 million icefish nests. Before this, icefish nests have only been found in groups of less than 100. Each nest is the shape of a bowl and was made by the fish digging out about 5 gallons worth of sediment to reveal gravel and rocks underneath, which is where around 1,700 eggs are laid. Besides being fish nurseries, the nests also draw other ocean organisms like sea stars, octopi, and other fish that scavenge dead icefish and hunt fish eggs. Seal tracking data also shows that seals tend to gather near the nesting site, often diving to the depth of the nests, suggesting that they use the nesting site as a food source. Empty nests are colonized by stationary organisms like sea sponges, further shaping the environment.

This study shows a snapshot of the ecosystem surrounding the largest fish breeding colony observed yet. The icefish nest site could become a regional marine protected area, which would help protect and preserve the ecosystem. Scientists plan to continue researching the site by leaving a camera that will take images over the next two years.

This study was a collaborative effort led by Dr. Autun Purser at the Alfred Wegener Helmholtz Centre for Marine and Polar Research.

Managing Correspondent: Gemma Johnson

Press Articles: “An icefish colony discovered in Antarctica is world’s largest fish breeding ground”, CNN, “’Nothing but fish nests’: huge icefish colony found in Antarctic sea”, The Guardian

Podcast: “A Massive New Find Of Icefish Found Near Antarctic”, Science Friday Original Journal Article: “A vast icefish breeding colony discovered in the Antarctic”, Current Biology

Image Credit: Purser, Autun; Boehringer, Lilian; Hehemann, Laura; Wenzhöfer, Frank (2021): Ocean Floor Observation and Bathymetry System (OFOBS) images of Neopagetopsis ionah ice fish nest arrays in the Filchner Trough, Antarctica collected during the PS124 Polarstern expedition. PANGAEA, https://doi.org/10.1594/PANGAEA.932827