MarLIN

information on the biology of species and the ecology of habitats found around the coasts and seas of the British Isles

Thornback ray (Raja clavata)

Distribution data supplied by the Ocean Biogeographic Information System (OBIS). To interrogate UK data visit the NBN Atlas.

Summary

Description

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 Ireland

Common 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 distribution

Distributed 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).

Habitat

Raja 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).

Depth range

10-300

Identifying features

  • Short-snouted.
  • 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.

Additional information

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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Bibliography

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  2. Chevolot, M., Ellis, J.R., Hoarau, G., Rijnsdorp, A.D., Stam, W.T. & Olsen, J.L. 2006. Population structure of the thornback ray (Raja clavata L.) in British waters. Journal of Sea Research, 56, 305–316

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  13. Holden, M. J., 1972. The growth rates of Raja brachyura, R. clavata and R. montagui as determined from tagging data. Journal du Conseil International pour l’Exploration de la Mer, 34, 161–168.

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Citation

This review can be cited as:

Snowden, E. 2008. Raja clavata Thornback ray. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. Available from: http://www.marlin.ac.uk/species/detail/2187

Last Updated: 08/05/2008