The unexpected find is way larger than any other known colony of fish nests found so far.
The fact that we know less about the ocean floor than we do about the Moon’s surface doesn’t make this astonishing discovery any less amazing. A study team just discovered the world’s largest fish spawning location known to date, 500 meters beneath the ice covering the south of Antarctica’s Weddell Sea.
According to a new research published in Current Biology, 60 million active nests of Jonah’s icefish (Neopagetopsis ionah) span at least 240 square kilometers. A towed camera system headed by the German research vessel Polarstern aided in the finding.
Until date, researchers had only met a few, if not several dozen, icefish nests at a time. Previously, even the most gregarious nest-building fish species were only known to congregate in the hundreds (other such species include the artistically inclined pufferfish, and freshwater cichlids).
Deep marine researcher Autun Purser of Germany’s Alfred Wegener Institute and colleagues discovered the large colony in early 2021 while on a research expedition in the Weddell Sea, which lies between the Antarctic Peninsula and the main continent.
According to their findings, icefish have a significant and previously unknown impact on Antarctic food webs.
Icefish are unique not only because they are the only known vertebrates that lack hemoglobin-containing red blood cells (hence the name white-blooded icefish), but also because they have a protein-based antifreeze in their blood (white in color and nearly see-through, by the way), which allows them to live beneath the Antarctic ice shelf. So much so that the researchers uncovered a nesting ground the size of Malta, with one breeding site per 3 square meters (32.3 square feet).
The number of nests at the breeding ground is estimated to be over 60 million based on Polarstern measurements, suggesting that the location is critical for the species and a marine ecosystem deserving of conservation. The European Union and the international Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) have been considering establishing a Marine Protected Area here since 2016, although it has yet to be implemented.
“The concept that such a massive breeding region of icefish in the Weddell Sea was previously unknown is extremely amazing,” said Purser, the study’s principal author, in a statement.
Purser’s exuberance is understandable when you consider that the AWI has been investigating this specific section of the Weddell Sea for the past 40 years, but only tiny clusters of icefish breeding sites have been discovered. So, why are we here? The researchers utilized oceanographic and biological data to show that the large breeding location corresponded with an inflow of warmer deep water from the Weddell Sea onto the nesting ground shelf.
The biomass of the colony is estimated to be over 60,000 tons since each active nest holds 1,000-2,000 eggs and there are several adults surrounding to defend them. It’s no surprise, therefore, that hungry Weddell seals visit the resource-rich area.
The nesting site undoubtedly tops the records for important breeding sites, being the largest geographically massive contiguous fish breeding colony ever documented on Earth – a fairly compelling justification for the construction of the proposed marine protected area.
“Given how little is known about the Antarctic Weddell Sea, this highlights the importance of international efforts to establish a Marine Protected Area (MPA),” said AWI Director and deep-sea biologist Professor Antje Boetius, who was involved in developing non-invasive technology that allowed the team to observe the ecosystem without disturbing it. “Unfortunately, CCAMLR has yet to unanimously approve the Weddell Sea MPA. However, given that the site of this unique breeding colony has been identified, Germany and other CCAMLR members should ensure that no fishing and only non-invasive research is conducted there in the future.”