A sunny winter day in 2016 found marine biologist Yoshihiro Fujiwara anchored off the coast of central Japan, measuring plump eels, when confusion suddenly broke out on board the ship. The crew of the Shonan Maru had just landed a big, bizarre-looking fish.
“Wow! We have a coelacanth!” they played while hoisting a specimen so large that it evoked the legendary “living fossil” species found only in Africa and Indonesia.
JAMSTEC
Fujiwara, whose specialty is “whale-dropping” communities – the rich ecosystems that emerge around and feed on whale carcasses – was equally moved and skeptical.
“It was exciting,” he told CBS News. “But this is a well-studied bay.”
It actually is. Researchers have been building a taxonomy of specimens from Suruga, Japan’s deepest bay, since the 19th century.
The area is also one of the most fished in the world. Certainly, Fujiwara thought, someone had seen this colossal creature before.
Surprisingly, no one had. Fujiwara and his team from the Japanese Earth Marine Science and Technology Agency (JAMSTEC) checked reference books and consulted colleagues around the world before concluding that the purple-colored spear-shaped creature from the depths was indeed a genuine discovery.
Three more specimens of the monster fish would be hooked that year, quickly preserved in formaldehyde or frozen for later reading in the laboratory.
JAMSTEC
Dissection, computed tomography and other analyzes placed the sample within the alepocephalid family, a species of deep water distributed worldwide and popularly known as “slickheads”, for their scaleless heads and gills. But unlike his much smaller relatives, who average only 35 centimeters in length, he was a beast: 55 centimeters long and 55 kilograms, he was the size and weight of a small child.
Fujiwara and his team decided to name the new species “yokozuna slickhead”, in honor of the top of the ranking in the sumo fight.
“I couldn’t believe it,” biologist Jan Yde Poulsen, an associate researcher at the Australian Museum and authority on slickheads, told CBS News from his base in Denmark.
Poulsen, who co-authored an article in January with the JAMSTEC team on the yokozuna slickhead, also doubted when he received the first photo from the Fujiwara team.
“It’s a very grainy picture, almost like when you see a picture of the Loch Ness monster,” he said. “The fact that you find a new species that weighs 25 pounds is just unbelievable.”
Despite its hostile deep sea, pitch-dark habitat, the slickhead was not only big, it was strong. While other slickhead species devour plankton and weak swimmers like jellyfish, DNA examination of the giant fish’s stomach content showed that it hunted other fish, perhaps supplementing its diet with scavengers.
Unlike the other 100 known species of slickhead in the world, the yokozuna is a vigorous swimmer, possibly capable of covering long distances, as evidenced by a few seconds of rare video captured with a bait camera at a depth of nearly 8,500 feet.
JAMSTEC
The slickhead’s “wide mouth” houses several rows of teeth, evoking an extraterrestrial monster. Fujiwara’s team tried to count the densely packed tusks and their strictly unofficial conclusion: “80 to 100” teeth in those jaws.
Physical attributes, in addition to biochemical analysis, identified the yokozuna slickhead as a vertex predator – the deep-sea version of a lion or killer whale.
“We have so many dives around the world,” said Fujiwara. “But it is rare to see a top predator.”
The well-endowed maritime agency has a number of sophisticated submersibles and other offshore exploration vehicles, “but these are very noisy and use strong light,” said Fujiwara. “Most major predators are very active, so (they) can easily escape from our submersible.”
His team determined that launching specially made long lines – long enough to reach the bottom of the ocean, equipped with hundreds of mackerel bait hooks – would be more effective, though time consuming. It takes up to four hours to deploy these ultra-long lines, which are left in the water overnight.
Although hundreds of new species of fish are identified annually, the deep sea that is difficult to access still holds many mysteries.
“We have no idea what’s down there,” said Fujiwara.