Sharks are some of the oldest known creatures on Earth, with some having been around for millions of years. While several species have been identified within the vast expanses of oceans, the deep waters can surprise us with something new when one least expects it. Now, researchers have discovered a new species of dogfish shark in the tropical waters of Southern Japan.

The new deep-water dogfish shark— Squalus shiraii—with unique features was discovered by an international team of scientists. It has been proposed to be named in honor of Dr. Shigeru Shirai, a former Japanese expert on the Squalus species.

Unique Characteristics

Squalus shiraii
Squalus shiraii (lateral view) Sarah Viana

Squalus is a group of dogfish sharks that are commonly known as 'Spurdogs'. The newly-discovered species measures 59-77 cm in length and possesses peculiar characteristics. Some of these features include a tall first dorsal fin (on the back), along with caudal (tail) fin with white margins that are broad.

"Squalus shiraii has body brown in color, postventral and preventral caudal margins whitish, dorsal and ventral caudal tips broadly white and black upper caudal blotch evident in adults," described Dr. Sarah Viana, lead author of the study. As of now, the new species is believed to be endemic to Japan and found only in the tropical shallow waters of the North-western Pacific around Southern Japan.

Previously Mistaken For Another Species

North-western Pacific Ocean
Map of the North-western Pacific Ocean, showing the geographical distribution of Squalus shiraii Sarah Viana

The newly-identified Squalus shiraii was gravely misidentified previously for another species of spurdog—Shortspine spurdog (Squalus mitsukurii). This incorrect categorization is due to the close resemblance that the two species share such as similarly shaped body, length of the snout and design of the fins. Nevertheless, there are marked differences that set the two creatures part.

"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," Dr. Viana explained.

Global Spurdog Trade

Shortspine spurdog
Shortspine spurdog(Squalus mitsukurii) Wikimedia Commons

Spurdogs form a commercially crucial group in the global fish trade. Currently, there are 30 recognized species of spurdogs across the world. They are fished for a wide range of uses. These include meat, liver oil and fins. In spite of their wide presence, accurate data surrounding the identification of the species is very limited. Data regarding threats to various populations and trends continue to remain obscure.

Currently, Japan is among the leading countries in the world that engage in the trade of shark fish. However, over the past few decades, the quantity of shark catches has diminished. Also, over 78 elasmobranch species—cartilaginous fishes such sharks, skates, sawfish, and rays—have now been classified as threatened.