Scientists have discovered the world's deepest fish during research in the depths of the Pacific.

They captured video footage of a type of snailfish at depths of 8,145 metres  - the greatest depth a fish has ever been observed.

They also discovered several new species on the trip to the Mariana Trench in the Pacific, as well as the first footage of the mysterious "supergiant" amphipod filmed alive.

An international team of marine biologists, geologists, microbiologists and geneticists made the discoveries on a 30-day expedition.

The team, which included scientists from the University of Aberdeen, recorded the footage using the Hadal-Lander, said to be the UK's deepest diving vehicle, which was designed and built entirely in Aberdeenshire.

They had already discovered a new species of snailfish living between 6,000 and 8,000 metres, itself a depth record, and were excited to find a fish even deeper down.

Alan Jamieson, from the University of Aberdeen, said: "This really deep fish did not look like anything we had seen before, nor does it look like anything we know of.

"It is unbelievably fragile, with large wing-like fins and a head resembling a cartoon dog."

They were also pleased to capture on video the extremely rare "supergiant" amphipod, a very large crustacean that was recovered by traps off New Zealand in 2012.

The new footage shows the supergiants swimming, feeding and fending off other would-be predators with their large body size and protective tail.

Dr Jamieson said: "Knowing these creatures exist is one thing, but to watch them alive in their natural habitat and interacting with other species is truly amazing, we have learnt a great deal."

The team carried out 92 deployments of deep-sampling equipment across the entire depth range of the trench from 5,000 metres to 10,600 metres during their trip.

The goal of the 30-day Hadal Ecosystem Studies (HADES) expedition aboard Schmidt Ocean Institute's Research Vessel Falkor was to characterise the environments, animals, ecological and geological processes of the deepest area of the world's ocean.

Led by the University of Hawaii, the expedition sampled a broad spectrum of environments rather than solely focusing on the deepest point.

Jeff Drazen, co-chief scientist from Hawaii, said: "Many studies have rushed to the bottom of the trench but from an ecological view that is very limiting. It's like trying to understand a mountain ecosystem by only looking at its summit."

The University of Aberdeen said that from their perspective the expedition, their 14th to the deep trenches, has been a major success.

They amassed 105 hours of video and filmed many other species of fish, setting new depth records for three other fish families.

They also successfully reached the bottom of the Sirena deep at 10,545m.

Wendy Schmidt, co-founder of the Schmidt Ocean Institute, was delighted with the success of the expedition.

She said: "Rarely, do we get a full perspective of the ocean's unique deep environments.

"The questions that the scientists will be able to answer following this cruise will pave the way for a better understanding of the deep sea, which is not exempt from human impact."

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