Spotback skate | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Chondrichthyes |
Subclass: | Elasmobranchii |
Superorder: | Batoidea |
Order: | Rajiformes |
Family: | Arhynchobatidae |
Genus: | Atlantoraja |
Species: | A. castelnaui |
Binomial name | |
Atlantoraja castelnaui (A. Miranda-Ribeiro, 1907) | |
The spotback skate (Atlantoraja castelnaui) is a species of fish in the family Arhynchobatidae. It is found off the Atlantic coasts of Argentina, Brazil, and Uruguay where its natural habitat is over the continental shelf in the open sea. It is a large fish, growing to over a metre in length. It feeds mainly on other fish according to availability, with shrimps, octopuses and other invertebrates also being eaten. Reproduction takes place throughout most of the year, with the eggs being laid in capsules that adhere to the seabed. The spotback skate is the subject of a fishery and is thought to be overfished, resulting in Greenpeace adding the fish to its red list of fish to be avoided, and the International Union for Conservation of Nature listing it as an "endangered species".
The Atlantoraja castelnaui are found in the Southwest South Atlantic Ocean from Rio de Janeiro State in Brazil to Argentina. They prefer warm-temperate waters at depths ranging from 20 to 220 m. [2] In Argentina, they can be found as natives to the Argentinian Zoogeographic Province. They seek warm water climates, and are often reported to have a more southern distribution than normal in correlation with higher water temperatures. Spotback skates may migrate only slightly or perform slight periodic backwards and forwards movement depending on ocean water temperatures. [3] However, there is no notable seasonal variation for the species as they populate southern waters year round.
Although the location of their distribution has not been affected, the quantity of the spotback's distribution has lowered in many places and continues to be threatened by humans fishing in its habitats. [2]
The length of maturity for males and females differ with males ranging from 185 to 1250 mm in total length and females ranging from 243 to 1368 mm in total length. [4] Males have a continuous production of mature spermatozoa suggests they can reproduce throughout the year but studies have shown higher values in certain months but they are not significant. Females also reproduce year-round with peaks of reproductive activity as well. [4]
Female spotback skates lay their eggs on the ocean floor and leave them there. There is not parental care so the eggs have a capsule that protects the embryo's development once the mother leaves. [5] Collected egg capsules typically are rectangular and have horny process in each corner. They are also shiny and are medium brown in color. [5] The capsules on the eggs are covered by adhesion fibrils that allow the egg to attach itself to the sea floor immediately after the mother releases them. These adhesion fibrils are also seen in other species of skates. [5] The surface of the capsule is striated and presents a rough surface though it is relatively smooth. Atlantoraja castelnaui capsule's are also the largest egg capsule in its genus and compared to other co-occurring species in the same area and depth of the ocean. [5]
In the cities of Santos and Guarujá, specimens of the spotback skate which are deemed large enough to have commercial value are commonly landed and marketed. [4] From 1999 to present, the market for the meat of the spotback skate has expanded to Asia, particularly South Korea. [4] As a result, commercial fishing has led to an overexploitation of the species and its consequent listing as an endangered species.
Spotback skates are particularly vulnerable to extinction [6] due to their large body size relative to other skate species. According to Dulvy & Reynolds (2002), skate species considered to be locally extinct have larger body sizes compared to all other skates. [4] Large body size is in turn correlated with higher mortality rates and with life-history parameters such as late age at maturity. [4] Another study by García et al. (2007) also corroborated the notion that a large body size increased the extinction risk in elasmobranchs. [4] Spotback skates are also especially vulnerable to trawl fisheries because they inhabit the soft bottom substrates of the ocean (Ebert; Sulikowski, 2007). [7] Consequently, the biomass of spotback skates has decreased by 75% from 1994 to 1999. [1] [7]
The spotback skate is found across most of the continental shelf year round. [6] The spotback skate's diet is a versatile and mainly piscivorous consumer. Their diet shifts with increasing body size and as a response to seasonal and regional changes in prey abundance and distribution. They prey mostly on teleost, cephalopods, elasmobranchs, and decapods. Smaller spotback skate tend to consume decapods and the larger skates eat elasmobranchs and cephalopods. [8] The consumption of teleosts differed between seasons depending on whether the teleost were demersal- benthic or benthic. The more demersal- benthic teleosts were consumed during the cold season while the benthic teleosts were eaten during the warm season. [8] The decapods, cephalopods and elasmobranchs were predominantly shrimps, octopuses, and skates. The main cephalopod consumed in the warm season was the octopus. [7]
Like all fish species, spotback skates have a variety of parasites; these include copepods, [9] nematodes [10] and Myxozoans. [11]
In 2010, Greenpeace International has added the spotback skate to its seafood red list. "The Greenpeace International seafood red list is a list of fish that are commonly sold in supermarkets around the world, and which have a very high risk of being sourced from unsustainable fisheries." [12]
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 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.
The Portuguese dogfish or Portuguese shark, is a species of sleeper shark of the family Somniosidae. This globally distributed species has been reported down to a depth of 3,675 m (12,057 ft), making it the deepest-living shark known. It inhabits lower continental slopes and abyssal plains, usually staying near the bottom. Stocky and dark brown in color, the Portuguese dogfish can be distinguished from similar-looking species by the small spines in front of its dorsal fins. Its dermal denticles are also unusual, resembling the scales of a bony fish. This species typically reaches 0.9–1 m (3.0–3.3 ft) in length; sharks in the Mediterranean Sea are much smaller and have distinct depth and food preferences.
The blackmouth catshark is a species of catshark, and part of the family Scyliorhinidae, 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 barndoor skate is a species of marine cartilaginous fish in the skate family Rajidae of the order Rajiformes. It is native to the northwestern Atlantic Ocean, and is found from the Grand Banks of Newfoundland and the southern side of the Gulf of St. Lawrence south to North Carolina. The fish is one of the largest skates found in the North Atlantic Ocean, reaching lengths up to 1.5 m (5 ft). It is carnivorous, feeding on invertebrates and other fish found near the sea floor.
Atlantoraja is a genus of skates in the family Arhynchobatidae. They are found from near sea level to depths of 300 metres (980 ft) in the Atlantic Ocean off Argentina, Brazil and Uruguay. These fish are all considered threatened due to the intense fishing pressure within their range.
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.
Arhynchobatidae is a family of skates whose members are commonly known as the softnose skates. It belongs to the order Rajiformes in the superorder Batoidea of rays. At least 104 species have been described, in 13 genera. Softnose skates have at times been placed in the same family as hardnose skates, but most recent authors recognize them as a distinct family. Members of the Arhynchobatidae can be distinguished from hardnose skates in having a soft and flexible snout, as well as a more or less reduced rostrum.
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.
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.
Batoidea is a superorder of cartilaginous fishes, commonly known as rays. They and their close relatives, the sharks, compose the subclass Elasmobranchii. Rays are the largest group of cartilaginous fishes, with well over 600 species in 26 families. Rays are distinguished by their flattened bodies, enlarged pectoral fins that are fused to the head, and gill slits that are placed on their ventral surfaces.
The mottled skate is a species of skate in the family Rajidae. An inhabitant of shallow coastal waters, it is found in the northwestern Pacific Ocean off Korea, Japan, and China. This species grows to 1.12 m (3.7 ft) long and has a diamond-shaped pectoral fin disc with a long snout. It is characterized by a covering of prickles above and below its snout, but not elsewhere on its body, and a dark ring in the middle of each "wing".
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 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 Norwegian skate, or black skate, is a species of skate found at depths of 200 m (660 ft) to over 1,600 m (5,200 ft) in the East Atlantic region. Initially its range was believed to be restricted to the Norwegian Sea and North Sea to the Bay of Biscay. It is occasionally encountered off the western coast of Ireland, and historically has been found near Rockall and in the Norwegian Deep, though recent surveys have not identified the species there. The species has frequently been confused with other skates, and since the late 1980s it has been confirmed to occur more widely, ranging from Iceland to Morocco, as well as off South Africa and in 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.
Bigelow's ray, also called the chocolate skate or Bigelow's skate, is a species of skate in the family Rajidae. It is named in honour of the oceanographer Henry Bryant Bigelow.