| Rough ray | |
|---|---|
 | |
| Rough ray ventral side | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Order: | Rajiformes |
| Family: | Rajidae |
| Genus: | Raja |
| Species: | R. radula |
| Binomial name | |
| Raja radula Delaroche, 1809 | |
The rough ray (Raja radula) is a Mediterranean ray species of the Rajidae family described by Delaroche in 1809. [2] [3]
The rough ray is named for the spinules that cover its upper surface. In juveniles and males, these rough spinules are only on the snout and the lower half of the tail. [4] The females of this species have spinules in these areas, but also around the mouth, along the mid-section, and the full tail. [4] These spinules differ from the thorns that are on the inner-eye and from the end of the head to before the dorsal fin. There are two thorns between the dorsal fins. [4]
The subcircular body has a short, curved snout, anterior edges are convex and the extremities are angular wings. [5] Most individuals are around 70 centimeters. The main upper surface colors are light brown and grey, with darker spots and lines. [4] There are two eye-spots with yellow rings and a thick outer darker ring with light dots, placed on either side of the spinal meridian at the level of greatest width of the body. [4] The underside of the ray is white with darkening edges, and some darker spots on the tail.
Raja radula is a benthic species native to the Mediterranean Sea. [7] Some Atlantic records are probably misidentifications of Leucoraja naevus and/or Raja africana and need to be clarified. [8] This species inhabits coastal areas, between 2 and 300m depth on sandy or muddy bottoms of the continental shelf. [7] [1]
This species seems to have short periods where they search for food and rapid digestion. Their diet consists mainly of benthic animals, such as crustaceans, teleosts, and mollusks. [9] Indeed, their main prey are crustaceans, such as decapods or amphipods, and the second are teleosts. It was found that diet remained relatively similar between individuals of different sexes, however, the size of the individual led R. radula to move from the consumption of crustaceans to teleosts. [9] The smaller individuals have a diet dominated by crustaceans as the medium size individuals. However, larger individuals seem to be specialized in teleosts. These changes in diet over their growth suggest that they have diet plasticity that can be explained by different energetic needs between younger and older individuals and as an adaptation to avoid competition for resources. Juveniles are active feeders during the day all over the year and have a higher metabolic rate than adults. [10]
Moreover, there is a difference in diet depending on the geographic location. These differences in diet between locations can be explained by the different distribution, abundance, density, and availability of the prey. Reproductive migration is common in elasmobranchs, as a consequence, they occupy different niches that may result in diet diversification. Raja radula has an active predator foraging behavior. Some pelagic species are found in their stomach content even if their morphology suggests that they can not prey on the water column. Thus, the hypothesis is that they also present scavenger behavior. [11] [12] They are considered as specialized secondary consumers but with sufficient plasticity in the diet to adapt their consumption in the function of the preys available in the environment. Their trophic level may increase with their growth.
Like many other rays, R. radula presents an oviparous reproduction strategy, meaning that parents produce offspring by laying eggs. The eggs have a case of 5.1 to 5.7 cm long. [13] The embryos hatch in about 4 months. [4] This species reproduces throughout the year, with a peak in late spring/early summer. [4] The females and males become mature at different sizes: females are mature at 34 cm disc width and males at 30 cm disc width [14] [4] This species reproduces throughout the year, with a peak in late spring/early summer. [4] The females and males become mature at different sizes: females are mature at 34 cm disc width and males at 30 cm disc width. [15] [16] [17] Half of the maturity is reached at 4.47 years for male individuals and 5.89 years for female individuals. Females can live until 12 years and reach 80 cm total length maximum while males can live 9 years and reach 65 cm total length maximum. The average length of 70 cm is therefore estimated to be reached at 9 years.
Rays usually present a swimming mode, where the thrust generation involves the passing of undulatory waves (from anterior to posterior) along with the enlarged pectoral fins. However, this species presents a particular locomotion behavior: pelvic fin locomotion. [18] The pelvic fin cycle has two phases: a recovery and a propulsion phase. Left and right fins move alternatively during the recovery and they move in synchrony when punting.
During the recovery phase, one of the pelvic fins lifts off the bottom and protrudes anteriorly; the other fin firmly touches the bottom during the propulsion phase. No vertical undulations of pectoral fins occurs during asynchronous movements of the pelvic fins and the species held its body parallel to the bottom. The ray performs a general form of punting: although the fins were not entirely synchronous, the offset was minimal, and therefore, still considered punting. The rough ray is pushed off the bottom by a rapid powerful punt followed by the pectoral fin undulations. Although the left and right pelvic fin movements can be slightly offset, the movements are generally considered synchronous punts.
The Mediterranean sea is subject to many pressures that endanger its biodiversity, particularly by urbanization and overexploitation. Like other elasmobranch species, Raja radula represents an important catch in the Mediterranean sea even if this species does not have any commercial value. Even if this species is not exploited or traded commercially, it is classified as Endangered (EN) according to the IUCN Red List. [1] Indeed, the greatest threat to this species is the by-catch [19] in demersal trawl, gillnet, trammel net, bottom longline, and purse seine fisheries. This bycatch occurs when fishing for cuttlefish, spiny lobster, red mullet, grouper, and Sparidae [20] mainly. In general, there are no conservation measures for this species. Indeed, it is not part of any education program, market control, or systematic monitoring scheme. [1] Furthermore, data on this species are often limited because when it is fished, the term "rays" or "stake" are recorded in the registry, which does not allow the determination of which species are fished. However, a study has shown that it is the sixth most commercially traded elasmobranch species in Palma de Mallorca. [21] This species is not registered in the CITES legislation from Species+ even when a decline of more than 50% is estimated. It is important to conduct further studies on this species to create accurate conservation programs for this endemic Mediterranean species.
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.
The cloudy catshark is a common species of catshark, belonging to the family Scyliorhinidae. It is a bottom-dweller that inhabits rocky reefs in the northwestern Pacific Ocean, from the shore to a depth of 320 m (1,050 ft). Growing up to 50 cm (20 in) long, this small, slim shark has a narrow head with a short blunt snout, no grooves between the nostrils and mouth, and furrows on the lower but not the upper jaw. It is also characterized by extremely rough skin and coloration consisting of a series of dark brown saddles along its back and tail, along with various darker and lighter spots in larger individuals.
The blackmouth catshark is a species of deepwater catshark, belonging yo the family Pentanchidae, common in the northeastern Atlantic Ocean from Iceland to Senegal, including the Mediterranean Sea. It is typically found over the continental slope at depths of 150–1,400 m (490–4,590 ft), on or near muddy bottoms. The youngest sharks generally inhabit shallower water than the older juveniles and adults. This slim-bodied species is characterized by the black interior of its mouth, a marbled pattern of pale-edged brownish saddles or blotches along its back and tail, and a prominent saw-toothed crest of enlarged dermal denticles along the upper edge of its caudal fin. It reaches lengths of 50–79 cm (20–31 in), with sharks in the Atlantic growing larger than those in the Mediterranean.
The white ghost catshark is a shark of the catshark family Pentanchidae, the deepwater catsharks. This shark is found in deep water in the northeast Atlantic between latitudes 57°N and 58°N. A deep-water catshark known from the eastern North Atlantic from depths of 1,014 to 1,800 m, it is known from only a limited number of specimens. It reaches a maximum of 54 cm or 1.7 ft total length which is a medium size for the Apristurus genus.
The Japanese angelshark is a species of angelshark, family Squatinidae, found in the northwestern Pacific Ocean off China, Japan, and Korea. It is a bottom-dwelling shark found in sandy habitats down to 300 m (980 ft) deep. This species has the flattened shape with wing-like pectoral and pelvic fins typical of its family, and grows to 1.5 m (4.9 ft) or more in length. Its two dorsal fins are placed behind the pelvic fins, and a row of large thorns occurs along its dorsal midline. Its upper surface is cryptically patterned, with numerous squarish dark spots on a brown background.
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.
The thornback ray, or thornback skate, is a species of ray fish in the family Rajidae.
The porcupine ray is a rare species of stingray in the family Dasyatidae. This bottom-dweller is found throughout the tropical Indo-Pacific, as well as off West Africa. It favors sand, coral rubble, and seagrass habitats in inshore waters to a depth of 30 m (100 ft). A large and heavy-bodied species reaching 1.2–1.5 m (3.9–4.9 ft) in width, the porcupine ray has a nearly circular, plain-colored pectoral fin disc and a thin tail without any fin folds. Uniquely within its family, it lacks a venomous stinging spine. However, an adult ray can still defend itself ably with the many large, sharp thorns found over its disc and tail.
The common torpedo, also known as ocellate torpedo or eyed electric ray, is a species of electric ray in the family Torpedinidae. It is found in the Mediterranean Sea and the eastern Atlantic Ocean from the Bay of Biscay to Angola, and is a benthic fish typically encountered over soft substrates in fairly shallow, coastal waters. Growing to 60 cm (24 in) long, this species has a nearly circular pectoral fin disc and a short, thick tail with two dorsal fins of nearly equal size and a large caudal fin. It can be identified by the prominent blue spots on its back, which usually number five but may vary from zero to nine, as well as by the small knobs on the rims of its spiracles.
The little skate is a species of skate in the family Rajidae, found from Nova Scotia to North Carolina on sand or gravel habitats. They are one of the dominant members of the demersal fish community in the northwestern Atlantic. This species is of minimal commercial importance and is mostly used as bait for lobster traps, though its wings are also marketed for food. It is also important as a model organism for biological and medical research.
The Jenkins' whipray is a species of stingray in the family Dasyatidae, with a wide distribution in the Indo-Pacific region from South Africa to the Malay Archipelago to northern Australia. This large species grows to 1.5 m (4.9 ft) across and has a broad, diamond-shaped pectoral fin disc and a whip-like tail without fin folds. It has a band of heart-shaped dermal denticles running from between the eyes to the tail on its upper surface, along with a characteristic row of large spear-like thorns along the midline. It is uniform yellowish brown above, becoming grayish on the tail past the stinging spine, and white below; there is apparently a spotted color variant that had previously been described as a different species, the dragon stingray.
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.
Helicolenus dactylopterus, blackbelly rosefish, bluemouth rockfish, and bluemouth seaperch, is a species of marine ray-finned fish belonging to the subfamily Sebastinae which is classified within the family Scorpaenidae. This Atlantic species is a typical sit-and-wait predator with a highly cryptic coloration.
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 graytail skate, or gray tail skate, is a large species of skate in the family Arhynchobatidae, native to the south-western Atlantic Ocean and south-eastern Pacific Ocean. It is listed as endangered by the IUCN. It was caught as part of a commercial fishery around the Falkland Islands and is a bycatch in several other fisheries.
The common eagle ray or bullray is a species of fish in the family Myliobatidae. It inhabits the eastern Atlantic Ocean, the Mediterranean Sea and the south-western Indian Ocean.
Sphyraena chrysotaenia, the yellowstripe barracuda, is a species of predatory, ray finned fish from the family Sphyraenidae which is found in the Indo-West Pacific region. It has entered the Mediterranean Sea from the Red Sea through the Suez Canal as a Lessepesian migrant and is now an important species in the fisheries of the eastern Mediterranean.
Stephanolepis diaspros, commonly known as the reticulated filefish or the reticulated leatherjacket, is a species of bony fish, a ray-finned fish in the family Monacanthidae. Its natural range is the western Indian Ocean but it is also one of the species which has colonised the Mediterranean through the Suez Canal by Lessepsian migration from the Red Sea.
The blonde ray or blonde skate is a species of ray fish in the family Rajidae.
The spotted ray or spotted skate is a species of skate in the family Rajidae.
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