Thornback ray

Description

The thornback ray (Raja clavata), or thornback skate, is a species of ray fish in the family Rajidae. It is found in coastal waters of Europe and the Atlantic coast of western Africa and Mediterranean Sea coast of North Africa. It is native possibly as far south as Namibia and South Africa. Its natural habitats are open large seas and shallow seas. It is sometimes seen trapped in large estuarine pools at low tide. The thornback ray is probably one of the most common rays encountered by divers. The thornback ray is usually found on sedimentary seabeds such as mud, sand or gravel at depths between 10-60 metres (33-197 ft). Juvenile fish feed on small crustaceans, particularly amphipods and bottom-living shrimps; adults feed on crabs, shrimps and small fish. Like all rays, the thornback ray has a flattened body with broad, wing-like pectoral fins. The body is kite-shaped with a long, thorny tail. The back is covered in numerous thorny spines, as is the underside in older females. Adult fish can grow to 1 metre (3.3 ft) in length, although most are less than 85 centimetres (33 in). This ray can weigh from 4.5 to 8.75 lb (2 to 4 kg). Their colours vary from light brown to grey with darker blotches and numerous small darker spots and yellow patches. Sometimes the yellow patches are surrounded by small dark spots. The underside is creamy-white with a greyish margin. When threatened they can appear black. In sexually mature fish, some of the spines are thickened with button-like bases (known as bucklers). These are particularly well developed on the tails and backs of sexually mature females. Raja clavata, the thornback ray (or thornback skate, roker), was named by Carl Linnaeus in the 10th edition of Systema Naturae in 1758, in the genus Raja of the Order Rajiformes in the Family Rajidae. Dorsal spines: 0; Anal spines: 0; Anal soft rays: 0. ; disc-width 1,25 to 1,36 times in its length, its length 1,70 to 1,83 times in total length; pectoral fins with clear angles on lateral side; triangular pelvic fins. Dorsally prickly; large females also prickly throughout their ventral surface; young and large males prickly along the borders of their discs and the underside of their snout. 30-50 thorns form a median row from the nape to the first dorsal fin; additional large 'buckler' thorns with swollen bases scattered on upper surface of disc in adults. Max length: 105 cm male/unsexed; 139.0 cm (female); common length: 85.0 cm; max. weight: 18.0 kg.