Featured picture: School of eels on the Tiefseeberg

Eels
(Image: Deep Sea Fish Ecology Lab / Astrid Leitner and Jeff Drazen, University of Hawaii Manoa, DeepCCZ expedition)

While huge schools of fish are not uncommon in the oceans, the wild mess these eels make is a unique find. Because this swarm has gathered on a deep sea mountain below 3000 meters.

At the bottom of the deep sea, scientists are constantly discovering undersea mountains, the peaks of which are thousands of meters below the sea surface. These so-called seamounts usually arise when ocean plates move and thus form volcanoes, but they do not reach the surface of the water. So far, however, marine biologists have only researched a few hundred of these deep-sea mountains and their sparsely populated surroundings.

The Pacific region between Hawaii and Mexico, the so-called “Clarion Clipperton Zone”, is an area in which several seamounts and license areas for future deep-sea mining are located. Scientists led by Astrid Leitner from the University of Hawaii in Manoa examined three of these deep-sea mountains and their surroundings for the occurrence of copper, zinc, cobalt and manganese for metal extraction during their expedition.

In doing so, they made a rare discovery: the team cast fishing bait on the summit of one of the deep-sea mountains, attracting a swarm of 115 pit eels (Synaphobranchidae). It was the largest concentration of fish ever observed below 3000 meters. As can be seen in the photo, the eels cavort around the casted mackerel bait.

“Our observations really surprised us,” said Leitner. “We had never seen reports of such high numbers of fish in the sparsely populated, food-limited deep sea.” The researchers captured a few animals and assigned them to the species Ilyophis arx – a little-known species with fewer than ten documented specimens worldwide.

The amazing thing: Leitner and her colleagues only observed the eels on the peaks of the undersea mountains, but not in the surrounding deep sea level. Earlier research also demonstrated this “seamount effect”, in which there is an increased occurrence of marine animals, corals and sponges only near the deep sea mountains.

The role the mountains play for the animals and whether they were spotted there by chance will have to be further researched in the future. Some marine animals such as eels are probably specially adapted to the food-limited life of the deep sea.

Recent Articles

Related Stories

Stay on op - Ge the daily news in your inbox