Raja clavata

Raja clavata, Photo: Michael Lahanas

Life-forms

Superregnum: Eukaryota
Cladus: Unikonta
Cladus: Opisthokonta
Cladus: Holozoa
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Classis: Chondrichthyes
Subclassis: Elasmobranchii
Superordo: Rajomorphii
Ordo: Rajiformes

Familia: Rajidae
Subfamilia: Rajinae
Genus: Raja
Species: Raja clavata
Name

Raja clavata Linnaeus, 1758
Type locality: Mediterranean Sea and northeastern Atlantic [original: "in Oceano Europæo"]
Syntypes: NRM 9072 (1)

Synonyms

Cephaleutherus maculatus Rafinesque, 1810
Hieroptera abredonensis Fleming, 1841
Raia aspera Risso, 1810
Raia rhizacanthus Regan, 1906
Raia rubus Bloch, 1784
Raja aspera Risso, 1810
Raja bonaespeiensis Fowler, 1910
Raja capensis Müller & Henle, 1841
Raja clavata Stephan, 1779
Raja leiobatos Gronow in Gray, 1854
Raja pontica Pallas, 1814
Raja rubus Bloch, 1784

References

Linnaeus, C. 1758. Systema Naturae per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis, Tomus I. Editio decima, reformata. Holmiæ: impensis direct. Laurentii Salvii. i–ii, 1–824 pp DOI: 10.5962/bhl.title.542: 232. Open access Reference page.

Links

Raja clavata – Taxon details on Integrated Taxonomic Information System (ITIS).
Raja clavata in the World Register of Marine Species
Raja clavata in FishBase,
Froese, R. & Pauly, D. (eds.) 2024. FishBase. World Wide Web electronic publication, www.fishbase.org, version 02/2024.
Raja clavata in Catalog of Fishes, Eschmeyer, W.N., Fricke, R. & van der Laan, R. (eds.) 2024. Catalog of Fishes electronic version.
Swedish Museum of Natural History Ichthyology name database

Vernacular names
български: Морска лисица
brezhoneg: Rae vouklet, Rac, rodellek
català: Clavellada
Cymraeg: Cath fôr, morgath styds
dansk: Sømrokke
Deutsch: Dornrochen, Keulenrochen, Nagelrochen
Ελληνικά: Σελάχι, Καλκανόβατος
English: Thornback ray, thornback skate, roker
español: Raya común, raya de clavos
euskara: Arraia gastaka, Bastanga
suomi: Okarausku
français: Raie bouclée
עברית: תריסנית קוצנית
magyar: Tövises rája
íslenska: Dröfnuskata
italiano: Raza, razza chiodata
lietuvių: Dyglioji raja
Nederlands: Doornrog, ruige rog, stekelrog
norsk nynorsk: Piggskate
norsk: Piggskate, piggrokke
polski: Płaszczka nabijana, raja ciernista, raja nabijana
português: Lenga, raia, raia pregada
română: Pisica de mare, pisică de mare
русский: или колючий скат, морская лисица, Скат шиповатый
slovenščina: Trnjevka, Raža trnjevka
shqip: Dhelpra e detit, ragja, shori
svenska: Knaggrocka
Türkçe: Dikenli vatoz
українська: Морська лисиця, Ромбовий скат колючий, Скат колючий, Скат шипуватий

The thornback ray (Raja clavata), or thornback skate, is a species of ray fish in the family Rajidae.[2]
Distribution

The Thornback ray is found in the Atlantic coastal waters of Europe and western Africa. It is also present from South Africa to the southwestern Indian Ocean [2] and in the Mediterranean and Black Seas.[3] It is native possibly as far south as Namibia and South Africa.[2]

Its natural habitats are open large seas and shallow seas. It is sometimes seen trapped in large estuarine pools at low tide.[2]

The thornback ray is probably one of the most common rays encountered by divers.
Habitat

The thornback ray is usually found on sedimentary seabeds such as mud, sand or gravel at depths between 10-60m. Juvenile fish feed on small crustaceans, particularly amphipods and bottom-living shrimps; adults feed on crabs, shrimps and small fish.
Description

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.[2][4]

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).[5]

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.[6][7]

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.[7]
Personificated face of a Raja clavata .
Taxonomy

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.[2]

It is one of about 13 species of skate (family Rajidae) that are known from the North Sea and adjacent Atlantic waters.
Common names
Raja clavata at the Aquarium de Vannes.

Common names include:[8]

Danish — Sømrokke.
Dutch — Stekelrog.
English — Roker / Thornback ray / Dorn.
Estonian — Astelrai.
Faeroese — Naglaskøta.
Finnish — Okarausku.
French — Raie bouclée.
German — Nagelrochen.
Icelandic — Dröfnuskata.
Latvian — Dzelkņraja.
Norwegian — Piggskate.
Polish — Raja nabijana a. ciernista.
Portuguese — Raia lenga / Raia brocheada
Russian — Колючий скат.
Spanish — Raya de clavos.
Swedish — Knaggrocka.

Morphometrics

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.
Top side view of a thornback ray on a white background.
Life cycle

Thornback rays are an oviparous and polyandrous species. Paired eggs are laid and deposited on shallow sand, mud, pebble or gravel bottoms . Up to 170 egg cases can be laid by a single female in a year, average fecundity around 48-74 eggs. In northwestern Europe, egg cases are laid during spring, and in the Mediterranean during winter and spring. Egg cases are oblong capsules with stiff pointed horns at the corners, each containing one embryo. Capsules are 5.0-9.0 cm long without the horns and 3.4-6.8 cm wide. Egg cases are anchored with an adhesive film.

Embryos feed solely on yolk. Egg cases hatch after about 4–5 months and pups are about 11–13 cm.

Mating season is from February to September, peaking in June. Adults observed to form same-sex aggregations during the mating season with females moving to shallower inshore waters approximately a month before the males. Mating does not occur in the Baltic Sea.[2] This is one of the fish used by the marine leech Pontobdella muricata as a host.[9]

British Isles population

Skeletal mount

A search about the growth and maturation of Raja clavata in the Solway Firth (part of the border between Cumbria, England and Dumfries and Galloway, Scotland) shows that the males and females appear to mature at 42 and 45 cm in disc width respectively. The Solway population is heavily exploited by an unrestricted commercial fishery and a considerable proportion (48.6%) of the retained catch is immature. It is suggested that fishing pressure has brought about a reduction in the size at which female fish mature.[10]
See also

Fish of the Atlantic Ocean
Fish of the Mediterranean Sea

References

Ellis, J. (2016). "Raja clavata". IUCN Red List of Threatened Species. 2016: e.T39399A103110667. doi:10.2305/IUCN.UK.2016-3.RLTS.T39399A103110667.en. Retrieved 15 November 2021.
Fishbase.org: Raja clavata
Guide of Mediterranean Skates and Rays (Raja clavata). Oct. 2022. Mendez L., Bacquet A. and F. Briand. http://www.ciesm.org/Guide/skatesandrays/raja-clavata
Filaman.ifm: Morphology of Raja clavata
Kindersley, Dorling (2005) [2001]. Animal. New York City: DK Publishing. ISBN 0-7894-7764-5.
Shark-references.com: Lists/literature by V.A. Vanov
Oceanario.pt: Raja clavata
http://www.ices.dk/explore-us/projects/EU-RFP/EU Repository/ICES ICES Fish Map: species factsheet for Raja clavata
"Pontobdella muricata Linnaeus, 1758". SeaLifeBase. Retrieved 27 December 2019.

Nottage, A. S. (1983). "Growth and maturation of roker Raja clavata L. in the Solway Firth". Journal of Fish Biology. 23: 43–48. doi:10.1111/j.1095-8649.1983.tb02880.x.

Picton, B.E. & Morrow, C.C., 2005. — Encyclopedia of Marine Life of Britain and Ireland.
Habitas.org.uk: Raja clavata (Thornback ray)