The unexpected find is much bigger than any other fish colony.
We know less about the ocean floor than we do about the Moon’s surface, but that doesn’t take away from how amazing this discovery is. A group of researchers just found the largest known fish spawning site 500 meters below the ice south of Antarctica’s Weddell Sea.
There may soon be a marine protected area just for the ice babies in their nests. Alfred Wegener Institute, PS124 OFOBS Team, is responsible for the photo.
A new study published in Current Biology says that the active nests of Jonah’s icefish (Neopagetopsis ionah) cover at least 240 square kilometres and are made up of 60 million nests. The German research ship Polarstern led a towed camera system that helped find it.
Researchers had only seen a few or dozens of icefish nests at a time up until now. Before, even the most social fish that build nests were only known to gather in groups of hundreds (other such species include the artistically inclined pufferfish and freshwater cichlids).
Deep sea researcher Autun Purser of Germany’s Alfred Wegener Institute and his colleagues found the large colony in early 2021 while on a research trip in the Weddell Sea between the Antarctic Peninsula and the main continent.
According to what they found, icefish have a big effect on Antarctic food webs that nobody knew about before.
Icefish are unique because they are the only known vertebrates that don’t have red blood cells with haemoglobin in them. This is how they got the name “white-blooded icefish.” They also have a protein-based antifreeze in their blood, which makes it white and almost see-through and lets them live under the Antarctic ice shelf. So much so that researchers found a nesting ground the size of Malta, with one nesting site for every 3 square meters (32.3 square feet).
Alfred Wegener Institute, PS124 OFOBS Team, is responsible for the photo.
Polarstern estimates that more than 60 million nests are at the breeding ground. This means that the area is important for the species and is part of a marine ecosystem that needs to be protected. Since 2016, the European Union and the International Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) have considered this area a Marine Protected Area, but it has yet to happen.
The study’s lead author, Purser, said, “It is hard to believe that such a large area where icefish breed in the Weddell Sea was not known before.”
Purser’s excitement is easy to understand when you consider that the AWI has been studying this part of the Weddell Sea for 40 years but has only found a few small clusters of icefish breeding sites. Why are we here, then? The researchers used oceanographic and biological data to show that the large breeding area was linked to the flow of warmer deep water from the Weddell Sea onto the nesting ground shelf.
Alfred Wegener Institute, PS124 OFOBS Team, is responsible for the photo.
The colony’s biomass is thought to be more than 60,000 tons since each active nest has between 1,000 and 2,000 eggs and several adults are nearby to protect them. So, it shouldn’t be a surprise that hungry Weddell seals come to the area because it has a lot of food.
The nesting site is the most important place for fish to breed because it is the largest, most connected fish breeding colony ever found on Earth. This is a pretty good reason to build the proposed marine protected area.
Given how little is known about the Antarctic Weddell Sea, this shows how important it is for international efforts to set up a Marine Protected Area (MPA),” said AWI Director and deep-sea biologist Professor Antje Boetius, who helped create non-invasive technology that let the team observe the ecosystem without disturbing it. “Unfortunately, CCAMLR has not yet agreed on the Weddell Sea MPA. But now that the location of this unique breeding colony has been found, Germany and other CCAMLR members should make sure that no fishing is done there in the future and that only non-invasive research is done there.
World’s Largest Fish Nesting Ground With 60 Million Nests Discovered Under Antarctic ice