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Mysterious new apex predator discovered in dark depths of Japan's Suruga Bay

A new species of deep-sea fish, scientifically named "Narcetes shonanmaruae," is seen after being caught in Suruga Bay, off the coast of Shizuoka Prefecture. (Photo courtesy of JAMSTEC)
A new species of deep-sea fish, scientifically named "Narcetes shonanmaruae," is seen. Many of the scales came off the body when it was caught. (Photo courtesy of JAMSTEC)
A new species of deep-sea fish, scientifically named "Narcetes shonanmaruae," undergoes a CT scan. (Photo courtesy of JAMSTEC with the cooperation of GE Healthcare Japan)

TOKYO -- A new species of deep-sea fish measuring over a meter long has been discovered in Japan's deepest bay by a research team led by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC).

    The fish is thought to be an apex predator in the ecosystem of Suruga Bay of Shizuoka Prefecture, southwest of Tokyo. The research team included the word "yokozuna" -- professional sumo's top rank -- in the fish's Japanese name as it is thought to be the largest member of the slickhead family, which usually grow to about 30 centimeters in length. The fish was given the scientific name "Narcetes shonanmaruae."

    Much of the ecosystem of Suruga Bay remains a mystery. In 2016, the team did bottom longline fishing and caught a total of four unknown fish from depths of about 2,100 to 2,600 meters. The specimens were between 1.22 and 1.38 meters long. Their scales were bright blue and they resembled coelacanths, deep-sea fish sometimes called "living fossils."

    CT scans and genetic analysis revealed that the fish can be classified in the family Alepocephalidae. Appending "yokozuna" to the species' Japanese moniker was a natural fit, as the Japanese name for the family "sekitori" apparently derives from wrestlers at grand sumo tournaments. Analysis of their stomach contents revealed that they preyed on other deep-sea fish, suggesting it is at the top of the local food chain.

    The team also caught the fish on video, swimming near the seabed. Researchers believe that they capitalize on their strong swimming and large mouth to catch their prey.

    Deep-sea areas make up over half of the world ocean, but the apex predators in each of these varying ecosystems are little known, unlike shallow-water hunters like orcas. Yoshihiro Fujiwara, a senior JAMSTEC researcher, said, "Fishing has been conducted in the deeper sea. If apex predators are in danger of extinction due to human beings, the ecosystem may be significantly out of balance. I want to examine the types and roles of top deep-sea predators to lead to sustainable use of the sea."

    The discovery was published in the British scientific journal "Scientific Reports" on Jan. 25.

    (Japanese original by Tomohiro Ikeda, Science & Environment News Department)

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