Angelshark

The angelsharks are a group of sharks in the genus Squatina in the family Squatinidae, which are unusual in having flattened bodies and broad pectoral fins that give them a strong resemblance to rays. This genus is the only one in its family and order Squatiniformes. They occur worldwide in temperate and tropical seas. Most species inhabit shallow temperate or tropical seas, but a few species inhabits deeper water, down to 1,300 m (4,300 ft).[2] Angel sharks are sometimes called monkfish, although this name is also applied to members of the genus Lophius.

Angel shark
Temporal range: 163.5–0 Ma[1]
Oxfordian to Present
Squatina australis
Australian angelshark (Squatina australis)
Squatina dumeril nefsc2
Sand devil (Squatina dumeril)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Infraclass: Euselachii
Superorder: Selachimorpha
Order: Squatiniformes
F. de Buen, 1926
Family: Squatinidae
Bonaparte, 1838
Genus: Squatina
A. M. C. Duméril, 1806
Type species
Squalus squatina
Angelsharks, off the coastline of Wales.

Appearance and biology

While the forward part of the angel shark's body is broad and flattened, the rear part retains a muscular appearance more typical of other sharks. The eyes and spiracles are on top and the five gill slits are on its back. Both the pectorals and the pelvic fins are large and held horizontally. There are two dorsal fins, no anal fin and unusually for sharks, the lower lobe of the caudal fin is longer than the upper lobe. Most types grow to a length of 1.5 m (5 ft), with the Japanese angel shark, known to reach 2 m.[3] Angel sharks possess extensible jaws that can rapidly snap upwards to capture prey and have long, needle-like teeth. They bury themselves in sand or mud lying in wait for prey, which includes fish, crustaceans and various types of mollusks.[2] They are ovoviviparous, producing litters of up to 13 pups. Pacific Angel Shark pups are born from March to June in deep water — generally 180 to 300 feet (55 and 90 metres) — possibly to protect the tiny pups from predators.[4] Angel Sharks usually reside in depths of 1–200 m and can be seen on muddy or soft bottom substrata where they can easily blend in as they lie on the bottom. Since Members of the family Squatinidae have a unique camouflage method, it goes hand in hand with how they obtain their food, by lying still on the sea floor, making rapid lunges at passing prey,and using negative pressure to capture prey by sucking it into their mouths. [5]

Tri-Species analysis

Morphological ID in the field can be to a great degree troublesome thinking about discontinuity of species for exchange or high likeness between congeneric species. In this specific circumstance, the shark aggregate having a place with the class Squatina is made out of three species circulated in the southern piece of the western Atlantic. These three species are arranged in the IUCN Red List as imperiled, and they are right now secured under Brazilian law, which denies angling and exchange. Sub-atomic hereditary apparatuses are presently utilized for commonsense ordered recognizable proof, especially in situations where morphological perception is forestalled, e.g., amid fish handling. Thus, DNA barcoding was utilized in the present examination to track potential wrongdoings against the arrival and exchange of imperiled species along the Sao Paulo coastline, specifically Squatina guggenheim (n = 75) and S. occulta (n = 5), and also the Brazilian guitarfish Pseudobatos horkelii (n = 5). DNA barcoding uncovered the ceaseless angling and trafficking of these ensured species, subsequently giving clear proof that the present protection models and strategies for observing are not working.[6]

Behavior

Although this shark is a bottom-dweller and appears harmless, it can inflict painful lacerations if provoked, due to its powerful jaws and sharp teeth. It may bite if a diver approaches the head or grabs the tail.[7]

Angelsharks have a unique way of breathing compared to most other benthic fish. They do not pump out water from the oropharyngeal cavity like other fish. Instead they use gill flaps located under their body to pump out water during respiration. Doing so also allows them to be more discreet and prevent detection.

Commercial value

Prior to the late 1980s, the Pacific angel shark was considered a "munk fish".[8] It was a byproduct of commercial gillnetting, with no commercial appeal and was used only for crab bait. In 1977, Michael Wagner, a fish processor in Santa Barbara, California, in cooperation with local commercial fisherman, developed the market for angel sharks.[8] The annual take of angel shark in 1977 was an estimated 147 kg.[8] By 1985, the annual take of angel shark on the central California coast had increased to more than 454 metric tons or an estimated 90,000 sharks.[8] The population declined dramatically and is now regulated.

In April 2008, the UK government afforded the angel shark full protection under the Wildlife and Countryside Act. Once considered abundant in the Atlantic Ocean, the angel shark (Squatina squatina) was classified as "critically endangered" in 2010.[9]

Species

There are currently 24 recognized species in this genus:

See also

References

  1. ^ Bourdon, J. (2011): Genera from the Fossil Record: Squatina Duméril, 1806. The Life and Times of Long Dead Sharks.
  2. ^ a b Stevens, J. & Last, P.R. (1998). Paxton, J.R. & Eschmeyer, W.N., eds. Encyclopedia of Fishes. San Diego: Academic Press. pp. 64–65. ISBN 0-12-547665-5.
  3. ^ Froese, Rainer, and Daniel Pauly, eds. (2016). "Squatinidae" in FishBase. January 2016 version.
  4. ^ Martin, R. Aidan. “Sandy Plains: No Place To Hide.” Sandy Plains: Pacific Angel Shark, 2003, www.elasmo-research.org/education/ecology/sandy-pacific_angel.htm.
  5. ^ Lyons, Kady; Lowe, Christopher G. (15 August 2015). "Organochlorine contaminants and maternal offloading in the lecithotrophic Pacific angel shark (Squatina californica) collected from southern California". Marine Pollution Bulletin. 97 (1–2): 518–522. |access-date= requires |url= (help)
  6. ^ "The fishing and illegal trade of the angelshark: DNA barcoding against misleading identifications". Fisheries Research. ScienceDirect. 2018. pp. 193–197. doi:10.1016/j.fishres.2018.05.018.
  7. ^ Bester, C. (2010): Florida Museum of Natural History. Pacific Angelshark.
  8. ^ a b c d Richards, J.B. (1987): Developing a Localized Fishery: The Pacific Angel Shark. Sharks: An Inquiry into Biology, Behavior, Fisheries, and Use. Cook, S. (Eds.) EM 8330: 147-160.
  9. ^ Fowler, S. (2010). "Background Document for Angel shark Squatina squatina" (PDF). German Federal Agency for Nature Conservation.
  10. ^ Walsh, J.H., Ebert, D.A. & Compagno, L.J.V. (2011): Squatina caillieti sp. nov., a new species of angel shark (Chondrichthyes: Squatiniformes: Squatinidae) from the Philippine Islands. Zootaxa, 2759: 49–59.
  11. ^ Acero P., A., Tavera, J.J., Anguila, R. & Hernández, L. (2016): A New Southern Caribbean Species of Angel Shark (Chondrichthyes, Squatiniformes, Squatinidae), Including Phylogeny and Tempo of Diversification of American Species. Copeia, 104 (2): 577-585.
African angelshark

The African angelshark (Squatina africana) is an angelshark of the family Squatinidae.

Angular angelshark

The angular angelshark or spiny angelshark (Squatina guggenheim) is an angelshark of the family Squatinidae found off southern Brazil, Uruguay, and northern Argentina at depths of between 4 and 265 m. Its length is up to 1.3 m.

Reproduction is ovoviviparous, with 6 to 8 pups in a litter. Shallow inshore regions are important as nursery grounds for this endangered species.

Argentine angelshark

The Argentine angelshark (Squatina argentina) is an angelshark of the family Squatinidae.

Australian angelshark

The Australian angelshark (Squatina australis) is a species of angelshark, family Squatinidae, found in the subtropical waters of southern Australia from Western Australia to New South Wales between latitudes 18°S and 41°S, at depths down to 255 m (840 ft). Its length is up to 1.52 m (5 ft). Reproduction is ovoviviparous, with up to 20 pups in a litter.

Chilean angelshark

The Chilean angelshark (Squatina armata) is an angelshark of the family Squatinidae found in the subtropical waters of Chile, that grows up to 1.03 metres (3 ft 5 in) in length. The holotype is lost. Reproduction is ovoviviparous.

Clouded angelshark

The clouded angelshark (Squatina nebulosa) is an angelshark of the family Squatinidae found in the northwest Pacific from the southeastern Sea of Japan to Taiwan between latitudes 47° N and 22° N. Its length is up to 1.63 m.

Reproduction is ovoviviparous.

Disparate angelshark

The disparate angelshark (Squatina heteroptera) is a species of angelshark. It occurs at depths down to 164 m in the Gulf of Mexico and reaches a length of 49 cm (19 in). Heteroptera in its name refers to the difference in size, shape and area of the two dorsal fins.

Eastern angelshark

The eastern angelshark (Squatina albipunctata) is an angelshark of the family Squatinidae.

Indonesian angelshark

The Indonesian angelshark (Squatina legnota) is a rare species of angelshark, family Squatinidae, known only from a few specimens collected from fish landing sites in southern Indonesia. It is thought to inhabit the deep waters of the continental slope. Reaching at least 1.34 m (4.4 ft) long, this species has a flattened, ray-like shape and a well-developed tail and caudal fin. It is characterized by the absences of fringes on its nasal barbels and thorns down the midline of its back, as well as by its relatively plain grayish-brown dorsal coloration with dark saddles beneath the dorsal fin bases and a black leading margin on the underside of the pectoral fins. The International Union for Conservation of Nature (IUCN) presently lacks sufficient information to assess the conservation status of this species.

Japanese angelshark

The Japanese angelshark (Squatina japonica) 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.

Feeding on fishes, cephalopods, and crustaceans, the Japanese angelshark is a nocturnal ambush predator that spends most of the day lying still on the sea floor. This species gives birth to live young, which are sustained during gestation by yolk. The litter size varies from two to 10. The Japanese angelshark is not dangerous to humans unless provoked. It is fished in large numbers and used for meat and shagreen, a type of leather. The International Union for Conservation of Nature has listed it under Vulnerable, citing the intense bottom trawling activity within its range and the low resilience of angel sharks to fishing pressure.

Ocellated angelshark

The ocellated angelshark (Squatina tergocellatoides) is an angelshark of the family Squatinidae found only from the Taiwan Straits in the western Pacific between latitudes 28 and 22°N and in northern Malaysia. Its length is up to 63 cm.

Reproduction is ovoviviparous.

Ornate angelshark

The ornate angelshark (Squatina tergocellata) is an angelshark of the family Squatinidae endemic to southern Australia between latitudes 30°S and 35°S, at depths of 130–400 m (430–1,310 ft). It can reach lengths of up to 1.4 m (4.6 ft). Reproduction is ovoviviparous, with two to nine pups per litter.It appears that S. tergocellatahas a minimum gestation period of 6-12 months and parturition may occur biennially. The most common stomach contents were squid (Notodarus gouldi) and fish (mainly Monacanthidae).

Pacific angelshark

The Pacific angelshark (Squatina californica) is a species of angelshark, family Squatinidae, found in the eastern Pacific Ocean from Alaska to the Gulf of California, and from Ecuador to Chile, although those in the Gulf of California and southeastern Pacific may in fact be separate species. The Pacific angelshark inhabits shallow, coastal waters on sandy flats, usually near rocky reefs, kelp forests, or other underwater features. This species resembles other angel sharks in appearance, with a flattened body and greatly enlarged pectoral and pelvic fins. Characteristic features of this shark include a pair of cone-shaped barbels on its snout, angular pectoral fins, and a brown or gray dorsal coloration with many small dark markings. It attains a maximum length of 1.5 m (4.9 ft).

An ambush predator, the Pacific angelshark conceals itself on the sea floor and waits for approaching prey, primarily bony fishes and squid. Prey are targeted visually and, with a quick upward thrust of the head, snatched in protrusible jaws. Individual sharks actively choose ideal ambush sites, where they stay for several days before moving on to a new one. This species is more active at night than during the day, when it stays buried in sediment and seldom moves. Reproduction is ovoviviparous, with the embryos hatching inside the mother's uterus and being sustained by a yolk sac until birth. Females give birth to an average of six young every spring.

Pacific angelsharks are not dangerous to humans unless provoked, in which case their bite can cause a painful injury. They are valued for their meat and are captured by commercial and recreational fishers across their range. A targeted gillnet fishery for this species began off Santa Barbara, California in 1976 and ended in 1994, after overfishing and new regulations led to its near-collapse. This species is now mainly fished in Mexican waters. The International Union for Conservation of Nature (IUCN) has assessed this species as Near Threatened, as the Californian population is largely protected and recovering, while the impact of Mexican fisheries is unknown.

Sawback angelshark

The sawback angelshark (Squatina aculeata) is an angelshark of the family Squatinidae

Smoothback angelshark

The smoothback angelshark (Squatina oculata) is an angelshark of the family Squatinidae found in the eastern Atlantic between latitudes 47°N and 28°S. Its length is up to 1.6 metre.

Reproduction is ovoviviparous.

It is fished for off the African coast, and is depleted in the Mediterranean.

Squalidae

The Squalidae, also called dogfish sharks or spiny dogfishes, are a family of sharks in the order Squaliformes. They have two dorsal fins, each with smooth spines, but no anal fin, and their skin is generally rough to the touch. Unlike virtually all other shark species, dogfish sharks possess venom which coats their dorsal spines – this venom is mildly toxic to humans.

These sharks are characterized by teeth in upper and lower jaws similar in size; a caudal peduncle with lateral keels; the upper precaudal pit usually is present; and the caudal fin is without a subterminal notch.

They are carnivorous, principally preying upon organisms smaller than themselves.

The livers and stomachs of the Squalidae contain the compound squalamine, which possesses the property of reduction of small blood vessel growth in humans.Two genera are known: Squalus, which contains numerous species, and Cirrhigaleus, which has three species.

Squatina squatina

Squatina squatina, the angelshark or monkfish, is a species of shark in the family Squatinidae (known generally also as angel sharks), that were once widespread in the coastal waters of the northeastern Atlantic Ocean. Well-adapted for camouflaging itself on the sea floor, the angelshark has a flattened form with enlarged pectoral and pelvic fins, giving it a superficial resemblance to a ray. This species can be identified by its broad and stout body, conical barbels, thornless back (in larger individuals), and grayish or brownish dorsal coloration with a pattern of numerous small light and dark markings (that is more vivid in juveniles). It measures up to 2.4 m (7.9 ft) long.

Like other members of its family, the angelshark is a nocturnal ambush predator that buries itself in sediment and waits for passing prey, mostly benthic bony fishes, but also skates and invertebrates. An aplacental viviparous species, females bear litters of seven to 25 pups every other year. The angelshark normally poses little danger to humans, though if provoked, it is quick to bite. Since the mid-20th century, intense commercial fishing across the angelshark's range has decimated its population via bycatch – it is now locally extinct or nearly so across most of its northern range, and the prospects of the remaining fragmented subpopulations are made more precarious by its slow rate of reproduction. As a result, the International Union for Conservation of Nature has assessed this species as Critically Endangered.

Taiwan angelshark

The Taiwan angelshark (Squatina formosa) is an angelshark in the family Squatinidae. The Taiwan angelshark is one of four species of Squatina in the waters around Taiwan and Japan. It is a demersal, ray-like shark that grows to 1–2 meters in length.

Western angelshark

The western angelshark (Squatina pseudocellata) is an angelshark of the family Squatinidae found on the tropical outer continental shelf off northern Western Australia, at depths of 130 to 310 metres (430 to 1,020 ft). Its length is up to 64 centimetres (25 in).

Reproduction is ovoviviparous, with up to 20 pups in a litter.

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