| Thornback ray | |
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Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Order: | Rajiformes |
| Family: | Rajidae |
| Genus: | Raja |
| Species: | R. clavata |
| Binomial name | |
| Raja clavata | |
The thornback ray (Raja clavata), or thornback skate, is a species of ray fish in the family Rajidae. [2]
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.
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.
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]
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 include: [8]
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.
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]
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]
Skates are cartilaginous fish belonging to the family Rajidae in the superorder Batoidea of rays. More than 150 species have been described, in 17 genera. Softnose skates and pygmy skates were previously treated as subfamilies of Rajidae, but are now considered as distinct families. Alternatively, the name "skate" is used to refer to the entire order of Rajiformes.
Rajiformes is one of the four orders in the clade Batomorphi, often referred to as the superorder Batoidea, flattened cartilaginous fishes related to sharks. Rajiforms are distinguished by the presence of greatly enlarged pectoral fins, which reach as far forward as the sides of the head, with a generally flattened body. The undulatory pectoral fin motion diagnostic to this taxon is known as rajiform locomotion. The eyes and spiracles are located on the upper surface of the head and the gill slits are on the underside of the body. Most species give birth to live young, although some lay eggs enclosed in a horny capsule.
Raja, also known as raia, is a genus of skates in the family Rajidae containing 16 species. Formerly a wastebasket genus, many species historically categorized here have been moved to other genera in the family, such as Amblyraja, Beringraja, Dipturus, Leucoraja and Rostroraja. Raja are flat-bodied, cartilaginous fish with a rhombic shapes due to their large pectoral fins extending from or near from the snouts to the bases of their tails. Their sharp snouts are produced by a cranial projection of rostral cartilage. The mouth and gills are located on the underside of the body. They may be either solid-coloured or patterned, and most skates have spiny or thorn-like structures on the upper surface, while some species contain weak electrical organs within their tails. Mating typically occurs in the spring and the female lays numerous eggs per clutch which are encapsulated in leathery cases, commonly known as "mermaid’s purses". Species vary in size, ranging from about 40 to 140 cm (1.3–4.6 ft) in length. These bottom-dwellers are active during both day and night, and typically feed on molluscs, crustaceans and fish. Raja skates are found in the East Atlantic, also in the Mediterranean, and western Indian Ocean, ranging from relatively shallow water to a depth of 800 m (2,600 ft). Skates and related species have fossil records dating from the Upper Cretaceous period, thus this well-adapted species is quite ancient.
Mullus barbatus is a species of goatfish found in the Mediterranean Sea, Sea of Marmara, the Black Sea and the eastern North Atlantic Ocean, where its range extends from Scandinavia to Senegal. They are fished, mostly by trawling, with the flesh being well regarded. The International Union for Conservation of Nature has assessed their conservation status as being of "least concern".
The big skate is the largest species of skate in the waters off North America. They are found along the Pacific Coast from Alaska to Baja California, typically from the intertidal zone to a depth of 120 m (390 ft), and feed on benthic invertebrates and small fishes. They are unusual among skates in that their egg cases may contain up to seven eggs each. This species is one of the most commercially important skates off California and is sold for food.
The bottlenose skate, spearnose skate, or white skate is a species of skate in the family Rajidae. It is a benthic fish native to the coastal eastern Atlantic Ocean. Due to overfishing, it has been depleted or extirpated in many parts of its former range in the northeastern Atlantic and the Mediterranean Sea, and is now endangered.
The broad skate is a poorly known species of skate in the family Rajidae. It occurs at depths of 846 to 2,324 metres, and has been observed via remotely operated underwater vehicle by the Monterey Bay Aquarium Research Institute as deep as 3,167 metres (10,390 ft), making it one of the deepest-occurring skates known. It is sporadically distributed in the Pacific Ocean, from the Gulf of Panama to British Columbia and the Bering Sea, to the Tohoku Slope off northern Honshu and the Okhotsk Slope off Hokkaido. The species name, badia, comes from the Latin batius meaning "brown", referring to its color.
The undulate ray is a species of skate and cartilaginous fish found in the Mediterranean and East Atlantic from southern Ireland and England to the Gulf of Guinea. It is found in areas with mud or sand, and may occur as deep as 200 m (660 ft), though it prefers shallower depths. It is considered endangered due to overfishing.
The shagreen ray, also known as shagreen skate or fuller's ray, is a species of skate in the family Rajidae. This ray is found in the eastern Atlantic Ocean, from Murmansk, Russia through Norway, southern Iceland, the Faroe Islands, the Celtic Sea, the northern North Sea and Skagerrak, to western Morocco and the Madeira archipelago, but not in the shallow waters off England and Wales. It is also recorded sporadically in the Mediterranean Sea.
Jensen's skate, also known as the shortail skate, is a poorly known species of fish discovered in 2004 during a study of bottom ichthyofauna aboard the Norwegian RV G.O. Sars, where four species were identified, including A. jenseni.
The black scorpionfish, also known as the European scorpionfish or small-scaled scorpionfish, is a venomous scorpionfish, common in marine subtropical waters. It is widespread in the Eastern Atlantic Ocean from the British Isles to the Azores and Canary Islands, near the coasts of Morocco, in the Mediterranean Sea and the Black Sea.
The clearnose skate is a species of cartilaginous fish in the family Rajidae. R. eglanteria is also known by other common names such as the brier skate and summer skate. Clearnose skates are easily identified by the translucent patches on either side of their snouts and their mottled dorsal surface. They are found along the Atlantic and Gulf coasts of the United States in shallow waters of the continental shelf.
The pita skate is a medium-sized skate in the family Rajidae. The holotype and only known specimen was found in the northern Persian Gulf, in Iraqi waters. It was collected at a depth of less than 15 m (49 ft).
The roundel skate or Texas clearnose skate is a species of cartilaginous fish in the family Rajidae. It is found in the Gulf of Mexico, Southeast Florida and the Yucatan Peninsula.
Raja straeleni, the biscuit skate, false thornback skate, or spotted skate, is a species of marine fish in the skate family of order Rajiformes. It is native to the eastern Atlantic Ocean.
Caliraja stellulata, commonly known as the Pacific starry skate, rock skate, prickly skate, or starry skate, is a species of cartilaginous fish in the family Rajidae. It is found on rocky bottoms at 18–982 m depths in the Northeast and Eastern Central Pacific, from Coronado Bank in northern Baja California in Mexico to Barkley Sound in British Columbia, Canada. Females reach a maximum total length of 76.1 cm and a maximum age of 15 years, while males can be up to 71.7 cm long and live up to 14 years; the total length at birth is 15.5–22.5 cm. This skate prefers cold water with a temperature of 4.1–11.6°C.
The flapper skate is a species of cartilaginous fish, a ray, belonging to the family Rajidae, the skates. It was formerly considered to be conspecific with the blue skate, the combined taxon being known as the common skate. The flapper skate is found in the Eastern Atlantic Ocean, although its range has contracted to a considerable extent due to overfishing, and it is classified by the International Union for Conservation of Nature as Critically Endangered. It is the largest species of skate in the World.
Pontobdella muricata is a species of marine leech in the family Piscicolidae. It is a parasite of fishes and is native to the northeastern Atlantic Ocean, the Baltic Sea, the North Sea, and the Mediterranean Sea.
The rough ray is a Mediterranean ray species of the Rajidae family described by Delaroche in 1809.
The blonde ray or blonde skate is a species of ray fish in the family Rajidae.
Data related to Raja clavata at Wikispecies| Authority control databases: National |
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