Broad Stingray

The broad stingray is found only in Hawaii and Taiwan. Most researchers agree their populations are plentiful. It is one of four species known to inhabit Hawaiian waters and belongs to the suborder elasmobranchs (cartilaginous fishes including sharks, skates, and rays).

The broad stingray exhibits a color-pattern known as counter-shading, a type of camouflage in which the brownish-black dorsal (top) surface is darker than the creamy white ventral (belly) surface. They can reach a body, or disc, width of 5 feet. Their body width is always greater than its length and their tails are twice the length of their bodies. Calcareous, sharp spines called tubercles cover the wide portion of the tail and one to three venomous spines are located near the top. The spines normally lay flat, but when threatened, the spines are raised at an angle and the flexible tail can be bent toward the head, impaling anything above the animal. The barbs have serrations along both sides and a venom gland at the base which is equipped with a powerful neurotoxin. The spine is made of modified dermal denticles, the same substance a shark’s rough skin is made out of. Once broken off, the spines are believed to grow back in 6-9 months on average.

These rays are sexually dimorphic, meaning the females are larger than the males. A female reaches sexual maturity when she is approximately 3.7 feet wide whereas the males are only 3 feet in width at the time of sexual maturity. All male elasmobranchs have two reproductive organs that extend behind the pelvic fins called claspers. During the summer mating months, the females release pheromones into the water signaling the male she is ready for courtship. The dance begins as the male bites the edges of the female’s pectoral fins and latches on while swimming together belly to belly. If mating is successful, the gestation period is 10-12 months. Mother rays are known to come into the shallows to give birth and then head back to deeper waters. The resulting litter can produce 3-4 very independent newborn rays, or pups, as there is no parental care seen among elasmobranchs. While in utero, however, developing embryos receive nourishment from their individual egg yolk and then uterine milk from their mother, believed to facilitate growth and ensure the pups survival.

The broad stingray is a non-aggressive, bottom-dwelling ray that prefers the muddy or sandy shallows. They have been observed burrowing into the sand with only their eyes and spiracles exposed. Spiracles are the rays’ respiratory organs. They are located between the eyes and the gill slits and supply necessary oxygen as they pull in water that passes over the gills. Scattered around the snout are sensory pores known as the ampullae of Lorenzini. Much like sharks, they can sense the electrical field of other living things. It is also believed to be beneficial in navigation and possibly in locating a mate. This “electro receptor” system assists these very active hunters who forage at night to locate crab, squid, octopus, and other soft prey. Their strong grinding bite plates are adapted for grating, creating a suction mechanism which allows them to mince and ingest prey.

Broad stingrays have been seen in waters as shallow at 8ft, but spend most of their time in waters between 49 feet and over 1,000 feet deep. Their main predator other than humans is the hammerhead shark.

*Due to the constant rotation of animals back to the ocean, the presence of any specific animal cannot be guaranteed.