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.
An egg case or egg capsule, often colloquially called a mermaid's purse, is the casing that surrounds the eggs of oviparous chondrichthyans. Living chondricthyans that produce egg cases include some sharks, skates and chimaeras. Egg cases typically contain one embryo, except for big skate and mottled skate egg cases, which contain up to 7 embryos. Oviparity is completely absent in the superorder Squalomorphii. Egg cases are also thought to have been produced by some extinct chondricthyan groups, such as hybodonts and xenacanths.
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.
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 common skate, also known as the blue skate, is the largest skate in the world, attaining a length of up to 2.85 m. Historically, it was one of the most abundant skates in the northeast Atlantic Ocean and the Mediterranean Sea. Despite its name, today it appears to be absent from much of this range. Where previously abundant, fisheries directly targeted this skate and elsewhere it is caught incidentally as bycatch. The species was uplisted to critically endangered on the IUCN Red List in 2006 and it is protected within the EU.
The spotback skate 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 thornback ray, or thornback skate, is a species of ray fish in the family Rajidae.
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 smalleyed ray or smalleyed skate is a species of ray in the family Rajidae, the typical rays and skates, from the eastern Atlantic Ocean where it is found in tidal, coastal waters with sandy substrates.
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 undulate ray is a species of ray 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 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 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 rough ray is a Mediterranean ray species of the Rajidae family described by Delaroche in 1809.
The sandy ray or sandy skate is a species of ray in the family Rajidae.
The spotted ray or spotted skate is a species of skate in the family Rajidae.
The deepwater ray, also called the deepwater skate or abyssal skate, is a species of skate in the family Rajidae.
