Latin name

Bathytoshia centroura

Other name

Bathytoshia centroura

Identification

The snout of the roughtail ray is blunt and slightly elongated. Behind the small eyes are spiracles larger than the eyes themselves. On the ventral surface of the disc are 5 gill slits, a mouth and elongated narrow nostrils. A flap of skin with a fringed lower edge runs between the nostrils. The medium-sized mouth is curved into a wide arch. The floor of the mouth is covered by 6 projections. The teeth are small and blunt, with rhombic bases, staggered to form a flat surface. Unlike females and immature individuals, the teeth of adult males are pointed. There are 7 upper and 12-14 lower functional rows of teeth in the mouth, although the total number is considerably greater.

On the dorsal surface in the central part of the caudal peduncle is a long serrated spine connected by ducts to the venom gland. Sometimes stingrays have 2 spines, periodically the spines break off and a new one grows in their place. Behind the caudal spine is a lower skin fold. In individuals with a disc width of 46-48 cm the skin is completely smooth. The disc of larger scats along the midline from the tip of the snout to the base of the tail, as well as the dorsal and lateral surfaces of the tail, begin to be covered with large spiny plaques. The plaques vary in size, the largest being the diameter of an eye, and may bear up to 3 spines.

Features of fish fins

The edges of the pelvic fins of these rays form an almost straight line, with pointed tips.

Fish colouring

The colouration of the dorsal surface of the disc is plain brown or olive, the ventral surface is white, not darkened at the edges.

Distribution

Widespread in Atlantic coastal waters. In the western Atlantic they are found from Georges Bank, New England to Florida, the Bahamas and the northeastern Gulf of Mexico. There are few records of these rays in the waters of Venezuela, Argentina and the Belize Barrier Reef. In the eastern Atlantic, northern Roughtail stingrays are distributed from south of the Bay of Biscay to Angola, including the Mediterranean Sea and the waters around Madeira and the Canary Islands.

Habitat

Roughtail stingrays are found in depths of up to 274 metres in the Bahamas and are regularly caught in depths of over 200 metres in the Mediterranean, although they are more commonly found in depths of 15-50 metres. These bottom dwellers inhabit a variety of habitats, including open areas with sandy, muddy or mussel-rich bottoms. In the Northwest Atlantic they are often found in brackish waters and off the coast of West Africa in the lower reaches of large rivers. Preferring water temperatures of 15-22°C, temperature is the main factor influencing their distribution.

Size

The pectoral fins of the Roughtail Stingray fuse with the head to form a diamond-shaped flat disc, 1.2-1.3 times as wide as long, with rounded fins ("wings"). The length of the whip-shaped tail is 2.5 times the length of the disc. As the largest members of their genus, roughtail stingrays reach 2.6 m in diameter, with a maximum recorded length of 4.3 m and a weight of 360 kg. Females are generally larger than males.

Behavior

Off the east coast of the United States, they make seasonal migrations: from December to May they stay on the central and outer edge of the continental shelf from Cape Hatteras in North Carolina to Florida, with large individuals staying further south than small ones. In spring, the population moves north of the Cape into small bays, narrow inlets and brackish river mouths, maintaining the north-south size segregation. It is likely that populations of northern stingrays living in the Mediterranean also make similar migrations, moving into shallow coastal waters in summer and deeper waters in winter. Pregnant females of these stingrays prefer to stay apart. Normally these rays are inactive and spend most of the day lying on the bottom under a layer of sediment.

Food and feeding habits

They are versatile predators and their diet generally consists of the most available food in the habitat. They usually hunt near the bottom, although they can occasionally catch prey swimming in the water column. Their diet includes a variety of invertebrates and bony fish such as sand lance and stenotomus. Off the coast of Massachusetts they feed mainly on Cancer crabs, Mya clams, Polinices snails, Loligo squid and ringworms. In Delaware Bay, shrimp Cragon septemspinosa and polychaete worms Glycera dibranchiata form the basis of their diet. In Virginia waters, shrimp Upogebia affinis are the main food source. Off the coast of Florida they feed mainly on crustaceans (Rananoides, Sicyonia brevirostris, Polinices and Portunus) and polychaetes. Roughtail stingrays generally hunt near the bottom.

Reproduction

Roughtail stingrays are egg-laying fish. Embryos develop in the womb and feed on egg yolk and histotrophs. In adult females, only the left ovary and left uterus are functional. Off the east coast of the United States, females of this stingray give birth annually, mating in winter and early spring. After 9-11 months, 4-6 newborns, 34-37 cm long, are born in autumn or early winter. In North African waters, females give birth in July and December, suggesting either that they give birth twice a year after a 4-month gestation period, or that there are two distinct groups of females that carry the pups for 10 months and give birth once a year in different months. At these sites, the size of neonates is smaller than that of neonates in the North Atlantic population, with a disc width of 8-13 cm. This is probably due to the shorter gestation period. In the Northwest Atlantic, males and females reach sexual maturity at disc widths of 130-150 cm and 140-160 cm respectively, and in North African waters at 80 cm and 66-100 cm respectively.

Fishing

In the waters of the Northwest Atlantic, these rays are not targeted by commercial fisheries. Small numbers are caught as by-catch in bottom trawls and bottom longlines. Captured fish have historically been used as fertiliser. The Mediterranean is heavily fished with trawls, longlines and gillnets. Despite a lack of accurate data, their large size makes them vulnerable to overfishing. Recently, they have been caught less frequently in this region, which may indicate a decline in the population.

Relationship with a person

The large size and long venomous spine of these rays make them dangerous to humans, so fishermen should take care when catching them. However, they are generally not aggressive and are too deep to pose a threat to beachgoers. There is evidence that they damage shellfish beds. Northern spiny shark meat is consumed as food. The pectoral fins are sold fresh, smoked and dried. Fishmeal is made from the remains of the carcass, and liver fat is also valued.