Thornback ray (Raja clavata)
|Researched by||Emma Snowden||Refereed by||This information is not refereed|
|Other common names||-||Synonyms||-|
A short-snouted ray with typical diamond shape and sharply angled pectoral fins approaching 90 degrees. The colour is variable, usually a mottled, blotchy brown to grey, with numerous small dark spots and yellowish patches. In young fish the yellow patches form distinct spots, each outlined with smaller dark spots. The underneath is an off-white with grey to black margins. Dorsally the body is covered with coarse prickles, which are present from hatching. In addition, large, backward pointing thorns (called bucklers) are scattered over the dorsal surface, each of which has a thick button-like base. These thorns are particularly numerous on the tail and in females present in a line along the back. Raja clavata can grow up to 1 m long however 85 cm is the usual maximum length. Females are larger than males.
Recorded distribution in Britain and IrelandCommon all around coasts of Britain and Ireland, the most abundant ray in in-shore waters. Distribution includes the Wash, Outer Thames Estuary, Solent, Carmarthen Bay, Cardigan Bay, Liverpool Bay and Solway Firth (Ellis et al., 2005).
Global distributionDistributed throughout the eastern Atlantic: Norway, south of Arctic Circle & Iceland to Northwest Africa, Mediterranean, western Black sea, & rarely the western Baltic. Possibly from South Africa & south-west Indian Ocean (Stehmann & Bürkel, 1994).
HabitatRaja clavata frequents a wide variety of grounds from mud, sand, shingle and gravel. It is less frequently recorded on coarser sediment types. They are also found on patches of sediment among rocky outcrops and boulders. It may be found to a depth of 300 m but most common between 10 – 60 m. Although mainly a non-migratory species, the fish often moves close inshore during the spring. Juveniles are more likely to be found in near-shore coastal waters (Rousset, 1990).
- Upper surface always prickly.
- Upper surface has scattering of large 'buckler' thorns, large, backward pointing with button-like base.
- Row of 30-50 thorns from back of head to first dorsal fin.
- Various shades of brown to grey, often with dark and light spots or blotches, may appear as a marbled pattern.
- Small specimens may have distinctive yellow spots.
On account of its abundance, Raja clavata is an important fish commercially. Most of the skate found in fishmongers is likely to be thornback ray also known as the 'roker'. Thornback rays lay up to 150 egg cases a year. The empty egg cases are a common sight washed up on the shore and are known as mermaids purses. Thornback rays tend to lie covered in sand during the day and feed at night on a range of bottom-dwelling animals. They will eat fish such as sand eels, herrings, sprats and small flatfish however shore and swimming crabs and brown shrimps are its main food. Raja clavata resembles other rays found in area, but is distinguished by the large 'buckler' thorns scattered on dorsal surface.
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Last Updated: 08/05/2008