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Thornback ray

January 01, 1970

This article is about the species of fish in the Atlantic Ocean. For other fish with similar names, see Thornback.

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

Thornback ray
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Superorder: Batoidea
Order: Rajiformes
Family: Rajidae
Genus: Raja
Species:
R. clavata
Binomial name
Raja clavata

Distribution edit

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 edit

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 edit

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 edit

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 edit

 
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 edit

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 edit

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 edit

References edit

  1. ^ 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.
  2. ^ a b c d e f g Fishbase.org: Raja clavata
  3. ^ 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
  4. ^ Filaman.ifm: Morphology of Raja clavata
  5. ^ Kindersley, Dorling (2005) [2001]. Animal. New York City: DK Publishing. ISBN 0-7894-7764-5.
  6. ^ Shark-references.com: Lists/literature by V.A. Vanov
  7. ^ a b Oceanario.pt: Raja clavata
  8. ^ http://www.ices.dk/explore-us/projects/EU-RFP/EU Repository/ICES ICES Fish Map: species factsheet for Raja clavata
  9. ^ "Pontobdella muricata Linnaeus, 1758". SeaLifeBase. Retrieved 27 December 2019.
  10. ^ 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)

External links edit

  •   Data related to Raja clavata at Wikispecies
  • Fishbase.org Database: Raja clavata
  • IUCN Red List of all current Threatened Species
  • Photos of Thornback ray on Sealife Collection

January 01, 1970
thornback, this, article, about, species, fish, atlantic, ocean, other, fish, with, similar, names, thornback, thornback, raja, clavata, thornback, skate, species, fish, family, rajidae, conservation, status, near, threatened, iucn, scientific, classification,. This article is about the species of fish in the Atlantic Ocean For other fish with similar names see Thornback The thornback ray Raja clavata or thornback skate is a species of ray fish in the family Rajidae 2 Thornback ray Conservation status Near Threatened IUCN 3 1 1 Scientific classification Domain Eukaryota Kingdom Animalia Phylum Chordata Class Chondrichthyes Subclass Elasmobranchii Superorder Batoidea Order Rajiformes Family Rajidae Genus Raja Species R clavata Binomial name Raja clavataLinnaeus 1758 Contents 1 Distribution 1 1 Habitat 2 Description 3 Taxonomy 3 1 Common names 4 Morphometrics 5 Life cycle 6 See also 7 References 8 External linksDistribution editThe 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 edit 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 editLike 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 nbsp Personificated face of a Raja clavata Taxonomy editRaja 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 Rajaof 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 edit nbsp Raja clavata at the Aquarium de Vannes Common names include 8 Danish Somrokke Dutch Stekelrog English Roker Thornback ray Dorn Estonian Astelrai Faeroese Naglaskota Finnish Okarausku French Raie bouclee German Nagelrochen Icelandic Drofnuskata Latvian Dzelknraja Norwegian Piggskate Polish Raja nabijana a ciernista Portuguese Raia lenga Raia brocheada Russian Kolyuchij skat Spanish Raya de clavos Swedish Knaggrocka Morphometrics editDorsal 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 nbsp Top side view of a thornback ray on a white background Life cycle editThornback 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 nbsp 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 editFish of the Atlantic Ocean Fish of the Mediterranean SeaReferences edit 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 a b c d e f g 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 a b 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 amp Morrow C C 2005 Encyclopedia of Marine Life of Britain and Ireland Habitas org uk Raja clavata Thornback ray External links edit nbsp Data related to Raja clavata at Wikispecies Fishbase org Database Raja clavata IUCN Red List of all current Threatened Species Photos of Thornback ray on Sealife Collection Retrieved from https en wikipedia org w index php title Thornback ray amp oldid 1206470640, wikipedia, wiki, book, books, library,

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