JAPANESE SLEEPER RAY

Japanese sleeper rays

Japanese sleeper ray

View all available Japanese sleeper ray images in the Shark Pictures Database

Common Names: Sleeper ray, Japanese sleeper ray.

Latin Name: Narke japonica

Family: Narkidae

Identification: The Japanese sleeper ray has pair-shaped body disc. Reddish-brown to chocolate brown dorsum, often with a few scattered dark or light spots. Ventrum lighter brown. One rounded dorsal fin positioned posterior to pectoral fins. Tail thick, short and dorsally compressed with a lateral skin fold. High caudal fin, roughly triangular with no definition between upper and lower caudal lobes. Eyes small. Spiracles also small but with a prominent, raised rim that projects above the head. Groove around mouth.

Size: Maximum length 40cm.

Habitat: Usually found on sand near rocky reefs from 12 to 23 meters deep.

Distribution: Northwest Pacific Ocean. Southern Japan, North and South Korea, Mainland China, Taiwan and Hong Kong.

Diet: Invertebrates.

Behavior: The Japanese sleeper ray spends most of its time buried in the sand (see below). May incapacitate some prey by discharging its electric organs but probably mostly used for defense. Electric organs can emit 30-80v. Major predators include the blotchy swell shark.

Japanese sleeper ray buried under the sand

Reproduction: Ovoviviparous. Litter number up to 5.

Conservation Status: Listed as vulnerable by the IUCN. Heavy fishing pressure, particularly shrimp trawling in which this species is thought to be taken as bycatch in exists throughout the majority of its range. It is believed that post- discard survivorship is very low in electric rays. Although little specific information is available on this species population status, given its apparently restricted range in an area where historic and current fishing pressure is known to be intensive, it is likely that population numbers have been significantly reduced. Serious declines have been documented in populations of similar species, where they are heavily fished.

Citation: Carvalho, M.R. de & McCord, M.E. 2009. Narke japonica. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>

Photographs: Ito, Chiba Prefecture, Southern Honshu, Japan.

Similar species: Another sleeper ray known as the sleeper torpedo ray Crassinarke dormitor is said to occur off southern Japan but this may actually be the same species.

Reaction to divers: Remains motionless under the sand unless approached very closely. Will emit an electric shock if harassed.

Diving logistics:

Sometimes encountered around dive sites off the south coast of Honshu, Japan. Try dive shops in Chiba Prefecture or on the Izu Peninsula for the best chance of sightings.

HOME TAXONOMY UNDER THREAT CONTACT