japanese roughshark

An extremely rare roughshark only found in Japan

The Japanese roughshark (Oxynotus japonicus) is a rare species of shark in the family Oxynotidae, known only from a few specimens recovered from Suruga Bay and Honshu, the Enshunada Sea off west Japan at a depth of 738–1,150 feet.


Family: Oxynotidae – Roughsharks

Genus: Oxynotus 

Species: japonicus


Phylum– Chordata

Class– Chondrichthyles



Common NameDogfish Sharks

Family– Oxynotidae

Common NameRoughsharks




Average Size and Length: Mature females range 1.9 feet long and males 1.8 feet long. The maximum recorded length is 2.2 feet long.

Teeth and Jaw: The mouth of the Japanese roughshark is small, with thick, fleshy lips; the teeth in the upper jaw are narrow, erect, and smooth-edged, while those in the lower jaw are broad, blade-like, and smooth-edged. Only one row of teeth in the lower jaw are functional.

Head: The head is dorsally depressed. The snout is short, with large nostrils whose lateral and medial apertures are separated by a thick nasal flap. The eyes and spiracles are vertically oval in shape.

Denticles: The dermal denticles of the Japanese roughshark are large and widely spaced, giving the skin a very rough texture.

Demographic, Distribution, Habitat, Environment and Range: Only a few Japanes roughsharks have been found in Suruga Bay and Honshu, the Enshunada Sea off west Japan. It is benthic and occurs at a depth of 738–1,150 feet.

Aesthetic Identification: The Japanese roughshark is a uniform dark brown, with the lips, nasal flap margins, fin axils and inner margins of claspers white. The five pairs of gill slits are very small and vertical. They have two sail-like dorsal fins with deeply embedded spines. The large dorsal fins are subtriangular in shape, with the first dorsal spine sloping slightly backward. The pectoral fins have a convex front margin and a concave rear margin. The anal fin is absent. There is a strong ridge running between the pectoral and pelvic fins on each side of the body. They have a stout, high trunk. 

Biology and Reproduction: The Japanese roughshark is thought to be ovoviviparous.

Behavioral Traits, Sensing and Intelligence: Unknown.

Japanese Roughshark Future and Conservation: They are caught (and discarded) as bycatch by bottom trawlers throughout its entire limited range, and may be threatened given the declines in other bottom deep sea species in Suruga Bay.

Japanese Roughshark Recorded Attacks on Humans: Not a threat to humans.