A new species of fish, Narcetes shonanmaruae, was discovered in Suruga Bay, Japan, in 2021. This deep-sea fish, measuring about 1.40 meters in length and weighing 25 kilograms, lives at depths exceeding 2,100 meters and was previously unknown to science. It belongs to the alepod family, also known as slickheads, a group of deep-sea fish. Compared to its relatives, N. shonanmaruae is much larger, with a size similar to that of a ten-year-old child and a weight comparable to a medium-sized dog. A study published in Scientific Reports confirms it is the largest alepod known to date and one of the largest bony fish in the bathyal zone, which refers to the region of the ocean just above the deep sea. The four individuals of this species were captured at more than 2,171 meters, at the mouth of the bay, using a bottom trawling net. The JAMSTEC team, the Japanese agency for marine and terrestrial sciences and technologies, was conducting sampling campaigns when these unexpected fish were brought up. Researchers have nicknamed it the "yokozuna fish," in reference to the supreme rank in sumo wrestling. In Japanese, the entire family already has a sports-related name: sekitori iwashi, meaning "sumo wrestler sardine." Unlike its herbivorous relatives, which typically feed on gelatinous zooplankton, N. shonanmaruae is a piscivore, meaning it eats other fish. Behavioral observations and dietary analysis indicate that it preys on other fish. Isotopic analysis of stable nitrogen isotopes in certain amino acids confirms that N. shonanmaruae occupies one of the highest trophic positions ever recorded in a marine environment. JAMSTEC concludes that the fish is an apex predator in the deep waters of Suruga Bay, meaning it has no natural predators and plays a top role in the food chain. To understand the behavior of this newly discovered species, a baited camera was deployed at a depth of 2,572 meters in the same bay. The images captured show the fish actively swimming, contradicting the family's reputation as discreet grazers. This observation contributed to the study's subtitle: "an apex predator that actively swims." The study, published on January 25, 2021, is based on four fish specimens and some video footage taken at 2,572 meters, where the fish is seen swimming. The JAMSTEC team emphasizes the need to urgently clarify the diversity and role of large predators in the bathyal zone, as they influence ecosystem functioning and remain vulnerable to environmental changes.