Japanese Sleeper Ray: Narke japonica

Family: Narkidae
Common name(s)

Japanese Sleeper Ray.

Binomial

Narke japonica.

Synonyms

Torpedo japonica.

Identification

A small sleeper ray with a teardrop-shaped body. Disc sub-circular. Snout short, tip weakly convex. Pectoral fin apices evenly rounded. Eyes partially encircled by much larger spiracles.  Spiracles circular. Spiracular rim weakly raised, with no papillae. Nostrils with circular incurrent openings and narrow nasal flaps. Nasal curtain short, with deep central groove.
Pelvic fins broad. Tail broad based. Pronounced caudal keel. Single rounded dorsal fin, origin posterior to pelvic fin. Caudal fin much larger than dorsal fin. Upper caudal margin straight. Ventral and posterior caudal margin broadly convex.

Colour

Dorsum light brown to dark reddish brown, sometimes with dusky purple shadowing. Small dark blotched occasionally present. Ventrum white.

Size

Maximum length 37cm. Size at birth 8cm.

Japanese Sleeper Ray, Narke japonica, Chiba Prefecture, Honshu, Japan, Pacific Ocean.

Conservation Status

VULNERABLE

The Japanese Sleeper Ray (Narke japonica) is a bycatch component in trawl, gillnet, and line fisheries. In japan it is discarded, but in Taiwan and China it is ground into fish meal. Although no species specific catch information is available, overall declines in skate and ray numbers within the region indicate that the Japanese sleeper ray has likely declined by 30-49%.

Japanese Sleeper Ray, Narke japonica, Chiba Prefecture, Honshu, Japan, Pacific Ocean.
Habitat

Warm temperate to tropical seas. Benthic on soft bottoms and gravel at 12-140m.

Distribution

Northwest Pacific. Found from Japan to China, including South Korea and Taiwan.

Reproduction

Aplacental viviparous. Litter size 1-9.

Diet

Diet unknown.

Behavior

Poorly known. Capable of emitting mild electric shocks; probably to stun prey and as a defensive tactic.

Reaction to divers

Easy to approach. Generally remains motionless when approach.

Diving logistics

The Japanese sleeper ray is rarely encountered by divers. It is most common at dive sites in the southern half of Japan (e.g. along the south coast of Honshu) and around Taiwan.

Japanese Sleeper Ray, Narke japonica, Chiba Prefecture, Honshu, Japan, Pacific Ocean.
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Japanese Sleeper Ray, Narke japonica, Chiba Prefecture, Honshu, Japan, Pacific Ocean.

Japanese Sleeper Ray, Narke japonica, Chiba Prefecture, Honshu, Japan, Pacific Ocean.
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Japanese Sleeper Ray, Narke japonica, Chiba Prefecture, Honshu, Japan, Pacific Ocean.

Japanese Sleeper Ray, Narke japonica, Chiba Prefecture, Honshu, Japan, Pacific Ocean.
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Japanese Sleeper Ray, Narke japonica, Chiba Prefecture, Honshu, Japan, Pacific Ocean.

Japanese Sleeper Ray, Narke japonica, Chiba Prefecture, Honshu, Japan, Pacific Ocean.
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Japanese Sleeper Ray, Narke japonica, Chiba Prefecture, Honshu, Japan, Pacific Ocean.

Japanese Sleeper Ray, Narke japonica, Chiba Prefecture, Honshu, Japan, Pacific Ocean.
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Japanese Sleeper Ray, Narke japonica, Chiba Prefecture, Honshu, Japan, Pacific Ocean.

Japanese Sleeper Ray, Narke japonica, Chiba Prefecture, Honshu, Japan, Pacific Ocean.
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Japanese Sleeper Ray, Narke japonica, Chiba Prefecture, Honshu, Japan, Pacific Ocean.

Japanese Sleeper Ray, Narke japonica, Chiba Prefecture, Honshu, Japan, Pacific Ocean.
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Japanese Sleeper Ray, Narke japonica, Chiba Prefecture, Honshu, Japan, Pacific Ocean.

Japanese Sleeper Ray, Narke japonica, Chiba Prefecture, Honshu, Japan, Pacific Ocean.
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Japanese Sleeper Ray 017

Japanese Sleeper Ray, Narke japonica, Chiba Prefecture, Honshu, Japan, Pacific Ocean.

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Similar species

Spot-tail Sleeper Ray Distinguishable by paired pale blotches on posterior disc, above pelvic fins, and at tail base.