Biodiversity & Conservation

Thornback ray - Raja clavata

Raja clavata

Image Mark Thomas - A thornback ray in shallow water. Image width ca XX cm.
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Distribution map

Raja clavata recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

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  • OSPAR
Taxonomy icon Taxonomy Taxon English term
Phylum Chordata Sea squirts, fish, reptiles, birds and mammals
Class Elasmobranchii Sharks, rays and skates
Authority Linnaeus, 1758
Recent synonyms None
Map icon 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).
Habitat information icon Habitat information 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).
Text page icon 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. The thornback ray may be observed having submerged itself slightly in the substratum, with only the eyes protruding.
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 icon 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 mermaid's 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.

This review can be cited as follows:

Catherine Wilding and Emma Snowden 2008. Raja clavata. Thornback ray. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 22/05/2012]. Available from: <http://www.marlin.ac.uk/speciesinformation.php?speciesID=4229>