TOKYO Japanese researchers have succeeded in taking a video on the ocean floor of a deep-sea bony fish that is over 2.5 meters in length. The creature, named the yokozuna slickhead, is known as the largest bony fish species in the world among deep-sea fish that live in waters deeper than 2 kilometers, except for cartilage fish such as sharks and rays.
Six yokozuna slickhead fish have been caught in a deep-sea area in Suruga Bay of Shizuoka Prefecture in central Japan, with the largest measuring 1.38 meters long. The Japan Agency for Marine-Earth Science and Technology JAMSTEC was surveying the large deep-sea fish and took the video on the ocean floor south of the bay.
The research team extracted DNA from fish scales and particles of dung contained in deep-sea water as part of an ecological survey in a marine reserve south of Japan. They detected the genome sequence of yokozuna slickhead in samples collected at three locations, about 400 to 600 kilometers south of the bay.
The team lowered a camera with a bait cage that contained pieces of mackerel to the 2.09 kilometer deep seabed about 400 kilometers south of Suruga Bay in October 2021, and the camera captured the image of a very large yokozuna slickhead. The footage shows the fish with its characteristic indigo blue eyes threatening and chasing away Pacific grenadiers that had gathered near the bait. The yokozuna slickhead was 2.53 meters in length, which was estimated from the size of the cage.
Before the finding of the yokozuna slickhead, the giant rattail had been the largest bony fish known to live permanently in the deep sea, with one caught measuring 2.1 meters long.
Yoshihiro Fujiwara, a senior JAMSTEC researcher, commented: We measured the yokozuna slickhead many times because it was so big. There may be many other large new species in the deep sea. The yokozuna slickhead is the largest species of slickhead family. They are the pinnacle of the ecosystem in the deep sea because they eat other deep-water fish, so in 2021 they were named yokozuna, which means sumo grand champion.