New Dogfish Shark Species Discovered In Japan

An international team of scientists discovered a new dogfish shark species in the tropical waters of southern Japan. The group was till then misidentified as another shark species because of their similarities.

The researchers of a study identified the fish as a dogfish shark species (Squalus shiraii), which was previously thought to be a shortspine spurdog (S. mitsukurii). However, analysis of the new species, native to Japan, and other species in the area supported the S. shiraii was a novel group and showed specific differences between it and the S. mitsukurii.

"Squalus shiraii has body brown in colour, postventral and preventral caudal margins whitish, dorsal and ventral caudal tips broadly white and black upper caudal blotch evident in adults. S. mitsukurii has body conspicuously black to dark grey and caudal fins black throughout with post-ventral caudal margin fairly whitish and black upper caudal blotch not evident in adults," study lead author Dr. Sarah Viana of the South African Institute for Aquatic Biodiversity said in a Pensoft Publishers blog.

The name S. shiraii or Shiraii's spurdog paid homage to Japanese expert Dr. Shigeru Shirai.

Dogfish are small, bottom-dwelling sharks whose habitats range from 3,000 feet to shallower waters to receive sunlight. Among dogfish sharks, spurdogs are considered commercially relevant in the world fish trade, as they are often caught for their meat, liver oil and fins.

Many shark populations are in serious decline across the world because of threats such as commercial and recreational fishing. With Japan being one of the leading shark fisheries in the world, over 78 of the elasmobranch species being traded in the country’s shark fin markets are already evaluated as threatened in the IUCN Red List.

As for spurdogs, however, even if their occurrence is rather high, species identification, population trends and threats remain unknown.

"Aspects of the biology, distribution, ecology and population size of Squalus species from Japan are still poorly acknowledged with only two species, S. mitsukurii and S. suckleyi, usually targeted and more rarely S. japonicus," the researchers wrote. "Understanding the related threats and population trends are paramount as these species are historically under fishing pressures in Japanese waters."

The study was published in the journal Zoosystematics and Evolution.