Red Stingray

The red stingray can grow to 2 m (6.6 ft) long and 0.66 m (2.2 ft) across, though most do not exceed 1 m (3.3 ft) in length. The maximum recorded weight is 10.7 kg (24 lb). It has a diamond-shaped pectoral fin disc wider than long, with nearly straight front margins converging to a triangular snout. The small eyes are slightly elevated, and followed by spiracles that are almost twice as large. There is a thick flap of skin between the large nares. The teeth are arranged with a quincunx pattern into a pavement-like surface. Females and juveniles have blunt teeth, while adult males have pointed, recurved teeth. There is a row of 3 papillae across the floor of the mouth, sometimes with up to 2 pairs of accessory papillae alongside.

The red stingray may be endemic to the northwestern Pacific Ocean; it is found throughout Japanese coastal waters from Hokkaidō to Okinawa, and also occurs off Korea, mainland China and Taiwan. This species has been reported from as far as Thailand, the Philippines, Fiji, and Tuvalu. However, whether these records truly represent D. akajei has yet to be determined. The red stingray is commonly encountered in sandy areas close to shore and in bays at a depth of 10 m (33 ft) or more, but also inhabits muddy flats, coral reefs, and estuaries.

As an apex predator in nearshore demersal food webs, the red stingray plays a significant ecological role. Crustaceans are the most important component of its diet, followed by small bony fishes and then annelid worms, while molluscs are seldom consumed. In Tokyo Bay, important crustacean prey species are Crangon affinis for males, Oratosquilla ijimai for females, and Anisomysis ijimai for juveniles; the most important fish prey species is Sardinops melanostictus, followed by Conger myriaster. Like other stingrays, the red stingray is aplacental viviparous. During courtship, the male follows the female and bites at her pectoral fin disc, using his pointed teeth to gain a grip for copulation. The litter size has been variously reported as only 1 or up to 10. Males mature sexually at a disc width of 35–40 cm (14–16 in), and females at a disc width of 50–55 cm (20–22 in).

The venomous tail spine of the red stingray is potentially injurious to humans. The Ainu once used the dried tail spine, with the toxic sheath intact, as a weapon. This species is an incidental catch of commercial fisheries targeting flounder and other bottom-dwelling fishes, using bottom trawls, gillnets, set nets, and line gear. It is valued as food in Japan, especially in the Tokyo Bay area where it is consumed in autumn and winter; it may be prepared hard boiled, with miso soup, or as kamaboko. However, the small size of the red stingray limits its economic importance. Annual catches reported by Japanese fisheries have steadily declined from 20,000 tons in 1950 to varying between 3,959 and 5,388 tons from 1997 to 2004.