Using a cropped camera system, a team of scientists recently discovered the world’s largest fish farming area near the Felchner Ice Shelf in the southern Weddell Sea in Antarctica. They photographed and photographed many nests of ice fish of the species Neopagetopsis.
The unique observations are made using so-called OFOBS, the Ocean Floor Observation and Bathymetry System, a camera system designed to explore the sea floor in extreme environments, such as ice-covered seas. Scientists drag the camera on a special fiber-optic cable and generally a power cable at a speed of half to one knot, about a meter and a half above the sea floor.
In February 2021, the team aboard the research vessel Polarstern found a mind-boggling large ice fish breeding colony while scanning the sea floor with this camera system. The photos revealed many fish nests. Further observations show that, on average, one breeding site per three square metres, the team found a maximum of one to two active nests per square metre.
The team estimated the total number of fish nests at about 60 million. The nests are round, 15 cm deep and 75 cm in diameter.
Otton Perser, a deep-sea biologist at the Alfred Wegener Institute and the Helmholtz Center for Polar and Marine Research (AWI), and lead author of the current publication, said, “The idea that such a huge ice fish spawning area in the Weddell Sea has never before been discovered is a fantastic one.”
“After the astonishing discovery of several fish nests, we thought of a strategy on board the ship to find out the size of the breeding area – there was no end in sight. The nests are three-quarters of a meter in diameter – so they are much larger than the structures and creatures, some of which are only centimeters in size, which We usually detect it using the OFOBS system.”
“Therefore, we were able to increase the height above the ground to about three meters and the towing speed to a maximum of three knots, thus doubling the area examined. We covered an area of 45,600 square meters and counted 16,160 fish nests in the photos and video footage.”
The team distinguished several types of fish nests: ‘active’ nests containing between 1,500 and 2,500 eggs and in three-quarters of cases guarded by adult icefish Neopagetopsis ionah, or nests with eggs only; There were also unused nests, where only a fish without eggs, or a dead fish, could be seen.
When combined with oceanographic and biological data, the results revealed that the breeding zone spatially corresponds to the influx of warmer deep waters from the Weddell Sea to the higher shelf. Further analysis revealed that the area is a popular destination for Weddell seals. The scientists also calculated the biomass of the ice fish colony there at 60,000 tons.
German Federal Research Minister Bettina Stark-Watzinger said: “Congratulations to the participating researchers on their wonderful discovery. After the MOSAiC expedition, German marine and polar research has reaffirmed its privileged position. German research ships are afloat in environmental research laboratories.”
“They continue to navigate the polar seas and our oceans almost nonstop, serving as science platforms aimed at generating important results in support of climate and environmental protection. The Federal Ministry for Education and Research (BMBF) provides German marine and polar research with one of the most modern fleets of research vessels worldwide. This discovery can To make an important contribution to the protection of the Antarctic environment. The BMBF will continue to work towards this goal under the umbrella of the United Nations Decade of Oceanography for Sustainable Development, which runs until 2030.”
Professor Antje Boetius, Director of AWI and a deep-sea biologist, said, “The current study is a sign of the urgency of establishing marine protected areas in Antarctica. This remarkable discovery was enabled by a specific sub-ice survey technology that we developed during my ERC grant.”
“It shows how important it is to be able to explore unknown ecosystems before we perturb them. Given how little the Weddell Sea is in Antarctica, this further underscores the need for international efforts to create a marine protected area (MPA).”
- Autun Purser, Laura Hehemann et al. Icefish Metropole: Extensive breeding colony discovered in the southern Weddell Sea, Current Biology (2022). DOI: 10.1016 / j.cub.2021.12.022
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