Snailfish have been filmed in the ocean's hadal zone before, but never as deep as one small juvenile of a hitherto unknown species, discovered 8,336m beneath the surface to set a new world record.
“We have spent over 15 years researching these deep snailfish,” said British marine biologist Prof Alan Jamieson of the University of Western Australia (UWA), founder of the Minderoo-UWA Deep Sea Research Centre. “There is so much more to them than simply the depth – but the maximum depth they can survive is truly astonishing.”
A snailfish can handle pressures equal to the weight of 1,600 elephants, according to Guinness World Records, which is holding an award ceremony – for the scientists rather than the fish – in recognition of the new record in Tokyo today (4 April).
The scientific team was led by Prof Jamieson and Prof Hiroshi Kitazato of Tokyo University of Marine Science & Technology. Last September they began a two-month expedition to explore the deep North Pacific trenches off Japan from the research ship Pressure Drop, with the help of submersible pilot Victor Vescovo and his Caladan Oceanic team.
The mission, part of a 10-year study of the world’s deepest fish populations, was to explore the Japan (8km), Izu-Ogasawara (9.3km) and Ryukyu (7.3km) Trenches, deploying baited cameras in their deepest reaches. Seven crewed submersible dives and 63 lander deployments were carried out.
International marine scientific research body Inkfish, which shortly afterwards bought Pressure Drop and the ultra-deep submersible Limiting Factor from Vescovo, funded the expedition.
Divernet reported on the mission, including images of snailfish seen on the seabed, but it is only now that the deepest-fish record has been confirmed.
The deepest snailfish, from the Pseudoliparis genus, was found and filmed in the Izu-Ogasawara Trench south of Japan. A few days later in the Japan Trench the team also collected two Pseudoliparis belyaevi snailfish in traps 8,022m deep – the first fish ever to be collected from beyond 8km. The species had not been seen deeper than 7,700m before.
Small and solitary
“The Japanese trenches were incredible places to explore – they are so rich in life, even all the way at the bottom,” commented Prof Jamieson. Of the record snailfish, he said: “In other trenches such as the Mariana Trench we were finding them at increasingly deeper depths, just creeping over that 8,000m mark in fewer and fewer numbers, but around Japan they are really quite abundant.”
Most of the deep snailfish seen were described as large and “lively”, but the record was set by a very small and solitary juvenile. Unlike other deep-sea fish, juvenile snailfish tend to live at the deeper end of their depth range.
“The real take-home message for me is not necessarily that they are living at 8,336m but rather that we have enough information on this environment to have predicted that these trenches would be where the deepest fish would be,” said Prof Jamieson. “In fact, until this expedition, no one had ever seen nor collected a single fish from this entire trench.”
Until now the Guinness World Record for deepest fish had been an ethereal snailfish (Pseudoliparas swirei) observed at 8,143m in the Marianas Trench in November 2014 – again by Prof Jamieson, with Thomas Linley of the University of Aberdeen. The deepest capture of a live snailfish had been logged at 7,966m in the Marianas Trench that same month.
Prof Jamieson, who has also been responsible for finding the world’s deepest octopus, jellyfish and squid, will be back at sea in June as chief scientist on Pressure Drop – though it will have been renamed Dagon, while the submersible Limiting Factor will have become Bakunawa.