60 million icefish nest on the floor of the Weddell Sea were spotted by scientists onboard an icebreaker. The largest known breeding colony of fish is represented by the bonanza of nurseries.
Autun Purser of the Alfred Wegener Institute was on the bridge of the German icebreaker, called the RV Polarstern, keeping watch for whales when his graduate student, Lilian Bhringer, called up to the bridge.
Bhringer was watching a live video feed from the Ocean Floor Observation and Bathymetry System (OFOBS), which is a one-ton camera towed behind the ship.
Bhringer could see fish nest pockmarks on the seafloor in all directions, covering an area of 93 square miles.
The camera was moving across the seafloor and it just didn't stop. Bhringer told Live Science that they were everywhere.
The notothenioid icefish carved the bowls in the mud on the seafloor, which are native to the chilly southern oceans. They are the only animals that have no hemoglobin in their blood. Icefish are considered "white-blooded."
"After ringing up the home institute the next day, we realized we had found something spectacular," Purser said.
After the initial discovery, the team made subsequent passes over the site, towing the camera at a deeper depth to get a better view of the colony.
"The most ever seen before was forty nest or something like that," said Purser. This site has an estimated 60 million birds.
One adult fish watched over an average of 1,700 eggs in the most of the nests.
The researchers were in the general area because they were studying an upwelling of water that was 3.6 degrees warmer than the surrounding water. "We wanted to see how carbon goes from the surface to the water column and what communities are in the water column," said Purser.
Fish carcasses were mixed with the nest. The team is from the AWI OFOBS.
Young icefish, after hatching, swim to the floating buffet before returning to the seafloor to breed. The presence of icefish in the upwelling was expected because of the food. A breeding colony of many orders of magnitude larger than ever before was not.
The team found that the area was covered in fish carcasses, suggesting that the icefish colony is an important part of the local environment.
The commission for the protection of marine living resources in the ocean is trying to make the colony a marine protected area.
The icefish colony went from being very dense to nothing. It was like a line in the sand.
The outer edge of the warm upwelling was found to be a line in the sand. The upwelling seems to create a rare and ideal environment for the icefish to breed.
The crew of the polarstern left two cameras to observe the inner workings of this rare environment before leaving the area. In April 2022, Purser plans to return to the sea.
"There's a lot to be discovered," said Purser.
The study was published in January in the journal Current Biology.
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The article was published by Live Science. The original article can be found here.
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