Researchers Spot and Film Ocean’s Deepest-Dwelling Fish

Scientists working on the research vessel DSSV Pressure Drop  (now named Dagon ) near Japan recently filmed the deepest fish ever recorded beneath the ocean’s surface. The extremely small white snailfish was swimming at a record-breaking depth of 27,349 feet (8,336 meters, or 5.1 miles). Believed to be a juvenile member of the genus  Pseudoliparis, the researchers jumped at the opportunity to capture footage.

Sea-ing is Believing

In addition, scientists from the Minderoo-University of Western Australia Deep Sea Research Centre  and the Tokyo University of Marine Science and Technology caught two snailfish from the species  Pseudoliparis belyaevi while working in the Japan Trench north of the Izu-Ogasawara Trench. They used traps set at 26,319 feet and broke the record for the deepest fish ever captured.

Expedition lead scientist Alan Jamieson and founder of the Deep Sea Research Centre said in a statement, “The Japanese trenches were incredible places to explore. They are so rich in life, even all the way at the bottom.” He added that it was the first time anyone had seen or caught a fish in the Izu-Ogasawara Trench and believes there are more fish residing there.

Snailfish belong to the Liparidae family, of which there are over 400 known species. They live in shallow coastal waters as well as in the ocean’s deepest areas. They can tolerate extreme pressure up to more than 800 atmospheres, a condition that would squash most living creatures. In order to live so deeply underwater, snailfish do not have swim bladders (air-filled sacs that allow most fish species to have buoyancy). And instead of scales, snailfish have a gelatinous layer that prevents them from being crushed from the pressure, according to Jamieson. They also use a fluid called osmolyte that protects them on a cellular level.

Younger snailfish are generally better adapted to live in deeper water compared to their adult counterparts. This is the opposite of many other deep-sea fish species. The young snailfish’s ability to swim at deeper depths allows it to avoid potential predators that cannot swim as far down.

A Fin-tastic Discovery

Previously, the deepest fish ever filmed was a Mariana snailfish ( Pseudoliparis swirei) swimming at a depth of 26,831 feet in the Mariana Trench, which is the Earth’s deepest-known ocean trench.

The new footage, which was taken during a two-month expedition last August through September, implies that snailfish in the Japanese trenches may be more prolific than similar species that reside in other ocean trenches. Researchers have not yet determined the reason for this.

“The real take-home message for me, is not necessarily that they are living at 8,336m,” Jamieson said, “but rather we have enough information on this environment to have predicted that these trenches would be where the deepest fish would be, in fact until this expedition, no one had ever seen nor collected a single fish from this entire trench,” Jamieson said.

The scientists want to return to the trenches near Japan as well as the Ryukyu Trench to further study the snailfish as well as locate other deep-sea fish.