Only 17 species of fish are known from the abyssal ecosystems below 1,500 metres in the Arctic Ocean. These regions are harsh and inaccessible — they are incredibly deep and the surface above is often covered by ice.
A paper published in Deep Sea Research Part I: Oceanographic Research Papers in August 2026 offers new information on one of the few fish that can tolerate the extreme conditions at these depths: the Arctic deep-sea eelpout.
This ghostly, eel-like fish was initially known from a single specimen found near Iceland in 1896. Others captured by deep-sea trawls and observations on the seafloor using ROV cameras have led to a more thorough understanding of its biology and its taxonomic relationship to other species in recent years.
Until the researchers conducted genetic analysis, it had been classified as Lycenchelys platyrhina. Lead author Peter Rask Møller, a biologist at the University of Copenhagen, suspected that it did not really belong in that genus due to its lack of scales.
“With the recently collected specimens we ran some DNA tests that pointed us in the direction of other hydrothermal vent dwellers further south in the genus Pachycara,” Møller says.
- Giant deep-sea beasts aren’t just the stuff of legend – here’s how they got so massive
- Meet the animals that can survive the hottest temperatures on Earth
Now known as Pachycara platyrhina, the species is the first of its genus known from Arctic waters. Its nearest relatives are found on or near the Mid-Atlantic Ridge. This makes it even more unique.
“It is not closely related to other Arctic or Pacific zoarcids,” Møller explains. “Other Arctic zoarcids and other Arctic fishes are closely related to North Pacific lineages of cold-adapted relatives, indicating that they have their origin in the Pacific.”
P. platyrhina made its way to the hostile deeps of the Arctic from the Atlantic instead.
There, the species congregates around hydrothermal vents and methane seeps, which support unique chemosynthetic ecosystems reliant on the conversion of chemical compounds to energy by microbial life.
“They stay away from the hottest water – that would kill them – but take advantage of the abundant food at and near the chemosynthesis-based ecosystems,” Møller notes. The paper hypothesises that they may also use the warmer water emitted by hydrothermal vents to “bask,” perhaps accelerating larval or embryonic development or assisting in digestion of prey such as gastropods and amphipods.
“There is definitely an increased abundance of prey near hydrothermal vents and cold seeps, which can be very sparse in deep sea regions. The structures of the vent system, including the biogenic structures of the worm forests, can provide shelter,” adds coauthor Mari Heggernes Eilertsen, a biologist at the University of Bergen.
However, the fish are also found in areas where there are no vents or seeps, indicating that they are not entirely reliant on them – and can tolerate a wide range of temperatures.
Find out more about the study.
Top image: Pachycara platyrhina resting in a tubeworm forest. Credit: Centre for Deep Sea Research, ROV ÆGIR6000 (NORMAR), University of Bergen
More wildlife stories from around the world
- Giant squid detected in deep-sea canyon off coast of Australia
- Enormous animal filmed at bottom of deep, dark trench in the Pacific Ocean
- Gigantic iceberg breaks free in Antarctica, revealing ghostly mega-nest beneath
- NASA officials sent over 2,000 baby jellyfish into space. Tens of thousands more came back to Earth
