Scientists have filmed the deepest fish ever recorded which swam more than 8 km underwater. This creature, an unknown species of snailfish from the genus Pseudoliparis, was filmed at a depth of 8,336 meters in the Izu-Ogasawara trench, southeast of Japan. Previously, researchers caught footage of two other snailfish from the species Pseudoliparis belyaevi from a depth of 8,022 meters, making them the first fish ever to be collected at a depth greater than 8,000 meters. To record the snailfish from 8,336 meters underwater, scientists used unmanned submersibles to deploy baited cameras in the Japan, Izu-Ogasawara and Ryukyu trenches, which are 8,000, 9,300 and 7,300 meters deep, respectively. This expedition was part of a decade-long study into the world’s deepest fish populations.

The expedition team found that specific adaptations enabled some snailfish species to live about 1,000 meters deeper than the next deep-sea fish. For example, snailfish do not have swim bladders which can be difficult to maintain at high pressure. Snailfish also do not have scales but instead have a gelatinous layer. 

The organism filmed at the deepest depth was a juvenile fish as young snailfish are generally found at greater depths than adults. This is possibly because there is nothing else beyond them and they could be eaten. This exciting discovery speaks to how much more there is to learn about the oceans and our ecosystems. Understanding what species are out there can further our comprehension of how some creatures came to be.