Red Stingray: Hemitrygon akajei

Family: Dasyatidae
Common name(s)

Red Stingray.

Identification

A medium sized stingray with a relatively thick body and a kite-shaped disc that is slightly wider than long; disc width approximately 1.1-1.2 x length. Snout obtusely angular with a small protruding tip. Anterior margins of disc almost straight. Pectoral fin apexes broadly rounded. Pelvic fins fairly long with narrowly rounded apexes.
Eyes small. Snout length 1.8-2.3 x combined eye and spiracle length.
Mouth contains 3-7 oral papillae. Deep labial furrows around mouth. Lower jaw concave at symphysis. Short, wide, skirt shaped nasal curtain with a weakly fringed margin. Nostrils narrowly oval shaped.
Adults usually have a few spear-shaped thorns on tail anterior to tail sting. Occasionally small thorns  present along median of disc. Thorns absent in juveniles. V-shaped patch of dermal denticles on head. Tail somewhat depressed at base, tapering to tail sting, then filamentous to tip. Tail length (when intact) less than 1-1-1.6x disc width. Ventral finfold short; about .3x disc width. Dorsal finfold  just a ridge. Ventral finfold development varies; base length 39-58% of disc width. One tail sting usually present.

Colour

Dorsum reddish brown to dark brown with yellowish patches below eye and on posterior margin of spiracle. Ventrum white with a wide, irregular, bright yellow or brown margin. Dorsal surface of tail brown; darkening to tip. Sides of tail yellow. Ventral surface of tail and fin folds dusky anteriorly fading to black towards the tip.

Size

Maximum disc width 66cm. Disc width at birth unknown.

Habitat

Warm temperate / sub-tropical seas. On soft substrates, sometimes adjacent to reefs. From shallow bays to at least 50m. Known to enter brackish environments.

Distribution

Northwest Pacific Ocean. Common around the coast of Honshu, Japan. Also found from central China to Taiwan.
Observations from the Philippines may be misidentifications.

Conservation Status

NEAR THREATENED

Hemitrygon akajei is caught in commercial quantities in coastal and even brackish waters. It is taken as bycatch in the bottom trawl fishery, gillnet, set net and hook and line fishery targeting demersal bottom fishes such as flounders, and this bycatch is utilized. Landings are reported to be declining. Population is therefore strongly affected by present level of fishing.

Hemitrygon akajei plays an important role as an apex predator in the demersal food network of coastal regions across its range. However, very little is known of its life-history traits. The species is subject to high fishing effort and caught in commercial quantities in the coastal waters of Japan and even in brackish waters. It is taken as bycatch in the bottom trawl fishery, gillnet, set net and hook and line fishery targeting demersal bottom fishes such as flounders. This bycatch is utilized and landings are reported to be declining. Fecundity is very low with one pup per litter reported. Due to the current high level of bycatch and strong fishing pressure in its area of occurrence, which will have depleted the population, this species should be classified as Near Threatened. Data need to be collected in order to accurately assess the population status, which may show that the species falls into a higher threat category.

Citation

Huveneers, C. & Ishihara, H. 2016. Hemitrygon akajeiThe IUCN Red List of Threatened Species 2016: e.T60148A104113240. https://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T60148A104113240.en. Downloaded on 12 February 2021.

Reproduction

Matrotrophic aplacental viviparity. 1 pup per litter.

Diet

Diet consists mostly of crustaceans and small benthic fishes, and occasionally annelid worms.

Behavior

Sedentary. Spends much of the day resting on the substrate.

Reaction to divers

Normally shy unless habituated. Habituated animals will take food by hand.

Diving logistics

Red stingrays are occasionally encountered throughout much of Japan but they are abundant and very easily approached during baited shark dives in Chiba; on the southeast coast of Honshu. Big Fish Expeditions runs yearly Japanese Shark Diving trips where hundreds of these rays are always seen.

Similar species

Bennett’s Stingray A similar ray from Southeast Asia. Distinguished by larger head, narrower disc (length .9-1 x width), and longer tail greater than 2x disc width.