The red stingray (Hemitrygon akajei) is a species of stingray that lives in the northwestern Pacific Ocean. Its range includes coastal waters around Japan, Korea, and China, although scientists believe it may occur in additional regions that require further study.

These stingrays usually inhabit shallow coastal environments with sandy bottoms. They are also able to survive in brackish water, where freshwater and seawater mix. The species gets its name from the bright orange-red coloration on its underside, and some individuals also show orange markings on their upper surface. Most red stingrays grow to about 1 meter (3.3 feet) in length.

Red stingrays mainly feed on crustaceans such as crabs and shrimp, along with small bony fish. As important predators in their marine ecosystems, they help maintain balance within coastal food webs. Females give birth to live young, usually producing between one and ten pups at a time.

In Japan, red stingrays are considered a valuable food source. However, many are accidentally captured as bycatch during fishing operations targeting other species. This has contributed to population declines, and the International Union for Conservation of Nature (IUCN) currently classifies them as Near Threatened, meaning they may become endangered if their numbers continue to decrease.

Distribution and Habitat of Red Stingrays

Red stingrays are believed to occur mainly in the northwestern Pacific Ocean. They are found along much of the Japanese coastline, from Hokkaidō in the north to Okinawa in the south.

They also inhabit waters near Korea, mainland China, and Taiwan. There have been occasional reports of red stingrays in countries and regions such as Thailand, the Philippines, Fiji, and Tuvalu, but researchers are still investigating whether these sightings truly represent this species.

These stingrays prefer shallow coastal habitats with sandy bottoms. They are commonly found in bays at depths of around 10 meters (33 feet) or more. They may also inhabit muddy seabeds, coral reef environments, and estuaries where freshwater meets the ocean.

Physical Characteristics of the Red Stingray

The red stingray is recognized by its orange coloration on both the upper and lower surfaces of its body.

Although some individuals can grow up to 2 meters (6.6 feet) long and 0.66 meters (2.2 feet) wide, most adults are much smaller and usually measure less than 1 meter (3.3 feet). The heaviest recorded individual weighed approximately 10.7 kilograms (24 pounds).

Their body has a broad diamond-like shape, with the width greater than the length. The front edges of the body are nearly straight and meet at a pointed snout. Their eyes are small and slightly elevated, with spiracles located behind the eyes that are nearly twice as large and help with breathing.

Inside the mouth, their teeth form a rough, pavement-like surface. Young stingrays and females typically have flatter teeth, while mature males develop sharper, curved teeth. Small structures called papillae are also present on the floor of the mouth.

The tail is long, narrow, and whip-like, measuring about one to one and a half times the width of the body. A large serrated spine is located near the beginning of the tail. Behind the spine are a small upper ridge and a lower skin fold.

Young red stingrays have smooth skin, but adults develop rough patches of small scales called dermal denticles. These are found between and behind the eyes. Adults also have a line of thorns along the center of the back and additional small bumps near the tail spine.

The upper body is generally plain brown, often with yellow or orange areas around the eyes, behind the spiracles, along the body edges, and on the sides of the tail. The tail becomes darker toward the tip, sometimes appearing almost black. The underside is white with vivid orange-red markings.

Diet and Behavior of Red Stingrays

The red stingray plays an important role as an apex predator in shallow coastal ecosystems. It occupies a high position in the food chain and helps regulate populations of smaller marine animals.

Its primary food sources include crustaceans such as crabs and shrimp. It also consumes small bony fish and marine worms, while mollusks are only eaten occasionally.

In Tokyo Bay, feeding habits vary between individuals. Male red stingrays mainly consume the shrimp Crangon affinis, while females often prefer the mantis shrimp Oratosquilla ijimai. Young stingrays commonly feed on small shrimp species such as Anisomysis ijimai. One of the fish species frequently eaten is the Japanese sardine (Sardinops melanostictus).

Like many other stingray species, red stingrays reproduce by giving birth to live young through a process known as aplacental viviparity. During mating, males follow females and may gently bite their bodies.

Females can produce anywhere from one to ten offspring in a single birth. Males usually become capable of reproduction when their body width reaches about 35–40 centimeters (14–16 inches), while females mature at approximately 50–55 centimeters (20–22 inches) wide.

Relationship Between Red Stingrays and Humans

Red stingrays possess a venomous spine on their tail that can injure humans if the animal is stepped on or handled improperly. The Ainu people of northern Japan historically used dried stingray tail spines as weapons.

Today, many red stingrays are accidentally caught by fishing vessels targeting other species, especially flatfish such as flounder. They are captured using various types of fishing equipment, including nets and fishing lines.

In Japan, red stingrays are eaten as seafood, particularly around Tokyo Bay during autumn and winter. They may be prepared by boiling, added to miso soup, or processed into kamaboko, a traditional Japanese fish cake.

Although valued as food, red stingrays are not large enough to represent a major commercial fishery resource. The number caught by Japanese fisheries has declined significantly over time. Around 20,000 tons were harvested in 1950, but annual catches between 1997 and 2004 dropped to approximately 3,959–5,388 tons.

This decline, combined with continued fishing pressure and the species’ slow reproductive rate, has resulted in its classification as Near Threatened by the IUCN. Without effective management and conservation efforts, red stingrays may face a greater risk of becoming endangered in the future.