Govind Tekale
Scientists have found the largest known fish breeding area on Earth near the Filchner Ice Shelf in the southern Weddell Sea, Antarctica. A research team from the Alfred Wegener Institute documented approximately 60 million icefish (Neopagetopsis ionah) nests covering an area of 240 square kilometers – roughly the size of Malta.
“The idea that such a huge breeding area of icefish in the Weddell Sea was previously undiscovered is totally fascinating,” said Autun Purser, deep-sea biologist at the Alfred Wegener Institute and lead author of the study published in Current Biology.
Discovery Details
The team used a specialized Ocean Floor Observation and Bathymetry System (OFOBS) – a camera sledge designed for surveying extreme environments like ice-covered seas. When researchers first spotted the nests on monitors aboard the research vessel Polarstern in February 2021, they were stunned by the sheer density:
- Average of one nest per three square meters
- Maximum density of 1-2 active nests per square meter
- 16,160 fish nests counted within 45,600 square meters of surveyed area
- Each nest measures 75 centimeters in diameter and 15 centimeters deep
- Active nests contain 1,500-2,500 eggs each
- About 75% of active nests were guarded by an adult icefish
The researchers mapped over 100,000 nests using side-scan sonar technology, allowing them to estimate the colony’s total biomass at 60,000 tonnes.
Environmental Significance
The breeding area coincides precisely with the inflow of warmer deep water from the Weddell Sea onto the higher shelf. Data from transmitter-equipped Weddell seals revealed that 90% of their diving activities occurred within the icefish breeding grounds, suggesting the colony serves as a crucial food source.
AWI Director and deep-sea biologist Prof. Antje Boetius emphasized the discovery’s conservation implications: “This great discovery was enabled by a specific under-ice survey technology we developed during my ERC Grant. It shows how important it is to be able to investigate unknown ecosystems before we disturb them.”
Conservation Implications
The finding strengthens calls for establishing a Marine Protected Area (MPA) in the Atlantic sector of the Southern Ocean. A proposal led by the Alfred Wegener Institute has been under consideration by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) since 2016.
“Unfortunately, the Weddell Sea MPA has still not yet been adopted unanimously by CCAMLR,” noted Boetius. “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.”
German Federal Research Minister Bettina Stark-Watzinger praised the discovery: “German research vessels are floating environmental research laboratories. They continue to sail the polar seas and our oceans almost non-stop, serving as platforms for science aimed at generating important findings to support climate and environmental protection.”
Though the area has been naturally protected by remoteness and challenging sea ice conditions, Boetius warns that “with the increasing pressures on the ocean and polar regions, we should be much more ambitious with marine conservation.”
The findings were published in the journal Current Biology (DOI: 10.1016/j.cub.2021.12.022).
