ANDREA SEABROOK, host:
You know the classic fish story. I once caught a fish this big! Well, a team of scientists can now brag it caught a fish this deep - eight kilometers deep or almost five miles down. It's Science Out Of The Box.
SEABROOK: Scientists from Japan and Britain have just released the first photos and videos of a species of fish that lives at least 4.8 miles deep in the Pacific Ocean's Japan Trench. The old record was just four miles under water. Monty Priede directs the group leading this research, Oceanlab at the University of Aberdeen. He joins us on the line now from Scotland. Thanks for joining us.
Dr. MONTY PRIEDE (Director, Oceanlab, University of Aberdeen): Hello, there.
SEABROOK: So, I'm looking at the video right now online. We're putting it on our website, npr.org.
Dr. PRIEDE: Yeah.
SEABROOK: The fish, to me, they look like bullfrog tadpoles. They're like big blobs in the front with wavy tails.
Dr. PRIEDE: Yes, they belong to a group called the Liparidi (ph), and the common names for the liparids is either tadpole fish or snail fish. The official common name is snail fish. But these hadelle (unintelligible) species live deeper than six kilometers. They never occur any shallower.
SEABROOK: Did scientists have any idea that anything lived that deep, anything that was a vertebrate anyway, a fish?
Dr. PRIEDE: Well, there is one record for one fish that was caught at 8.5 kilometers, a (unintelligible) brotula, but that's just one dead specimen was dredged up, and it's never been confirmed. And that particular species has an average depth of occurrence of just four kilometers, so we've now regarded that as a vagrant. This species that we're seeing here was known from Russian and Danish expeditions, but they had trawled them up from shallower depths, and we only have five dead specimens known to science previously. So we're here. We got the film of the world's deepest living fishes.
SEABROOK: How did you get the camera down so deep?
Dr. PRIEDE: Well the problem is a steel wire 10 kilometers long, which is the ultimate depths we're aiming at, tends to break under its own weight, so what we've used is a free-form lander. So we named it after this sort of lunar lander type thing. It looks very similar, except we just dropped it off the ship; we don't need any rocket engines. And it falls down to the sea floor, takes about five hours to fall the eight kilometers down to the bottom. And then the onboard computers activate the cameras and the lights and start filming.
Then, after the mission is finished, the ship comes back again, sends an acoustic command to the receiver onboard the lander. The lander drops the weights and then ascends to the surface. And that's a tantalizing time waiting for the thing to come up to the surface. And you're not sure if you're going to get anything until the lander pops up on the surface, and then they can replay the videos. And while the guys on board the ship were astounded last week when they saw all these fish down there.
SEABROOK: They move really slowly. You have to imagine that having five miles of water pressing down on you is a lot of pressure on this fish.
Dr. PRIEDE: Yes, it is, and they will have all kinds of special adaptations. They don't have any air spaces in them, so being squashed by the water isn't a problem. But if you subject muscles or nerves to this kind of pressure, they stop working. So these fish must have all kinds of invisible adaptations at the molecular and ultra structural level, which we hope to study in future if we manage to catch more specimens.
SEABROOK: I can't tell though - because I have no point of reference, I can't tell how big these fish are in the video. The biggest ones are just over 12 inches long. They're actually relatively normal looking fish. They're not monsters. They're not tiny. They're just average fish. I guess that's the most important discovery, that you don't have to be all that special to live down there.
Monty Pried is the director of Oceanlab at the University of Aberdeen in Scotland. Thanks so much for sharing your fish story with us.
Dr. PRIEDE: Well, thanks for your interest.