A massive research initiative to explore deep-sea creatures brought discoveries to light in the northern Pacific Ocean last year, when scientists filmed and captured three fish at depths never recorded before.

As part of a 10-year collaborative study between the University of Western Australia and the Tokyo University of Marine Science and Technology that was funded by Caladan Oceanic, scientists used baited robotic cameras to film a young snailfish at about 8,300 meters below the surface, the Australian university announced on Monday. The school deemed the record-breaking discovery the "world's deepest fish."

The milestone was announced after a two-month expedition that specifically focused on the deep-sea fish populations in three trenches located near Japan. The Japan, Izu-Ogasawara and Ryukyu trenches stretch 8,000 meters, 9,300 meters and 7,300 meters respectively below the surface of the northern Pacific.

Snailfish are tadpole-like and can only grow to about 12 inches long. They are found in oceans across the world, with some species inhabiting relatively shallow waters. The snailfish discovered 8,300 meters down — which is more than 27,000 feet, or five miles, deep — belongs to an unknown species, scientists said. 

They found and filmed the fish last September in the Izu-Ogasawara trench south of Japan, setting a world record for the deepest fish ever recorded on video. The footage was released on Sunday, and shows the snailfish, which scientists described as a very small juvenile, swimming on its own just above the ocean floor.

This particular type of snailfish belongs to the Pseudoliparis family and had previously been seen about 7,700 meters below the surface of the ocean in 2008, according to the University of Western Australia. 

Video footage released over the weekend also shows two snailfish found and caught during the same research expedition. At 8,022 meters down, in another deep trench off Japan, the pair of fish captured in traps marked scientists' deepest catch on record.

"The Japanese trenches were incredible places to explore; they are so rich in life, even all the way at the bottom," said Alan Jamieson, a professor at the University of Western Australia who led the expedition, in a statement.

"We have spent over 15 years researching these deep snailfish," Jamieson added. "There is so much more to them than simply the depth, but the maximum depth they can survive is truly astonishing."

The professor said that scientists found snailfish "at increasingly deeper depths just creeping over that 8,000m mark in fewer and fewer numbers" in other areas, like the Mariana Trench — the world's deepest — which is in the western Pacific Ocean closer to Guam. But Jamieson noted that the population explored around Japan was especially "abundant."

"The real take-home message for me, is not necessarily that they are living at 8,336m," said Jamieson, "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."

In:
• Oceans
• Australia
• Pacific Ocean
• Japan