On the sea floor of Antarctica’s Weddell Sea, researchers have discovered the world’s largest fish breeding ground. More than 240km wide, the area hosts 60 million nests of the elusive icefish.
Icefish on the seafloor. Photo: Alfred Wegener Institute/PS124 OFOBS Team
Biologist Ditlef Rustad first discovered the icefish in 1927 in the Southern Ocean off Bouvet Island, the world’s most isolated island. So far, there are 33 known species of icefish. Sometimes known as the crocodile fish because of its unusually long snout and gray-brown color, it is 25-50cm long and its translucent skin lacks scales. It feeds on krill and other small creatures.
The white-blooded fish
Most importantly, it is also referred to as the “white-blooded fish” because it is the only vertebrate that lacks hemoglobin and red blood cells. Instead, its cardiovascular system consists of a larger heart and larger blood vessels, thereby pumping higher volumes of blood to compensate. Their lack of scales also may allow them to absorb more oxygen from the surrounding waters. The Antarctic Ocean is already very rich in oxygen. The fish has evolved to manage this harsh environment.
Spaced-out nests. Photo: Alfred Wegener Institute/PS124 OFOBS Team
Other than this, we don’t know much else about them…until now. Scientists from the Alfred Wegener Institute for Polar and Marine Research unexpectedly came across the giant colony of these fish while researching something else in the Southern Ocean. A special bathymetric camera documented perfectly spaced-out nests, which are little mounds of mud and small stones. Each nest contains up to 2,000 eggs. An adult icefish floats just above each nest, on constant guard.
Underwater cameras will continue to monitor the site until scientists return this April to continue their studies of this rare fish and its mating habits. The video below shows a tiny section of this almost endless hatchery.
