Squatina squatina

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Source: Wikipedia, the free encyclopedia.
This article is about the type of shark sometimes called monkfish. For other fish called monkfish, see Monkfish (disambiguation).
This article is about the species. For the genus, see angelshark.

Angelshark
An angelshark, a fish with a flattened body and mottled skin, swims just above the sea floor

Critically Endangered  (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Subdivision: Selachimorpha
Order: Squatiniformes
Family: Squatinidae
Genus: Squatina
Species:
S. squatina
Binomial name
Squatina squatina
World map with blue outlines on the coastlines of southern Scandinavia, northern Europe, Britain and Ireland, the Iberian Peninsula, the Mediterranean, and northwest Africa as far as the Canary Isles
Former range of the angelshark
Synonyms

Squalraia acephala* de la Pylaie, 1835
Squalraia cervicata* de la Pylaie, 1835
Squalus squatina Linnaeus, 1758
Squatina angelus Blainville, 1825
Squatina angelus Gronow, 1854
Squatina europaea Swainson, 1839
Squatina laevis Cuvier, 1816
Squatina lewis Couch, 1825
Squatina vulgaris Risso, 1810

* ambiguous synonym

Squatina squatina, the angelshark or monkfish, is a species of

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

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
.

Taxonomy and phylogeny

The angelshark was originally described by the Swedish natural historian

sister species of the angelshark is the sawback angelshark (S. aculeata). The two species formed a clade with a number of Asian angelshark species.[5]

Description

Illustration of an angelshark from above
Early illustration of an angelshark from Les poissons (1877)

One of the largest members of its family, female angelsharks can attain a length of 2.4 m (7.9 ft) and males 1.8 m (5.9 ft); the maximum reported weight is 80 kg (180 lb).

nares, as well as a smooth or weakly fringed flap. Folds of skin with a single triangular lobe are present on the sides of the head. The teeth are small, sharp, and of similar shape in both jaws.[2]

The pectoral and pelvic fins are wide with rounded tips; the two

dermal denticles are small, narrow, and pointed, and cover the entire upper and most of the lower body surface. There are patches of small spines on the snout and over the eyes. Small individuals have a row of thorns down the middle of the back.[2][6] The coloration is gray to reddish or greenish brown above, with many small black and white spots, and white below. Juveniles are more ornately patterned than adults, with pale lines and darker blotches. The dorsal fins have a darker leading margin and lighter trailing margin. Some individuals have a white spot on the back of the "neck".[7]

Distribution and habitat

The angelshark occurs in the

IUCN, it is possible that it has been extirpated from the North Sea. It remains extant around the Canary Islands, Algeria, Tunisia, Libya, Israel, Turkey, northern Cyprus, eastern Greece (the Aegean Sea
), the Adriatic Sea of eastern Italy, Sicily, Malta, Corsica, Ireland and western Britain/Wales . Its modern presence in parts of the Mediterranean is unknown, such as around Madeira, the Azores, Morocco, Egypt, continental Spain and France, Crete, Syria, Sardinia, western Greece and western Italy.
brackish environments. Northern angelshark subpopulations migrate northward in summer and southward in winter.[2]

Biology and ecology

photo of an angelshark resting on the sea floor
The angelshark is well-camouflaged against the sea floor.

During daytime, the angelshark usually lies motionless on the sea floor, buried under a layer of sediment with only its eyes showing. At night, it becomes more active, and may sometimes be seen swimming above the bottom.

isopod Aega rosacea.[12]

The angelshark is an ambush predator that feeds mainly on bottom-dwelling bony fishes, especially

Sepia officinalis and Sepiola spp., and the crabs Medorippe lanata, Geryon trispinosus, Dromia personata, Goneplax rhomboides, Liocarcinus corrugatus, and Atelecyclus rotundatus. The stomachs of some examined specimens have also contained seagrass or birds (in one case an entire cormorant).[1] Individual sharks select sites that offer the best ambush opportunities, and if successful, may remain there for several days.[8]

Angelsharks are aplacental viviparous, meaning the young hatch inside the mother's

gestation period. The mature ova measure 8 cm (3.1 in) across and are not enclosed in a capsule. The reproductive cycle has been estimated at 2 years with ovulation taking place in spring, though this periodicity is ill-defined. The litter size ranges from seven to 25 and is correlated with the size of the mother; the young are gestated for 8–10 months. Parturition occurs from December to February in the Mediterranean and in July off England, with the newborns measuring 24–30 cm (9.4–11.8 in) long. Males and females mature at lengths of 0.8–1.3 m (2.6–4.3 ft) and 1.3–1.7 m (4.3–5.6 ft), respectively.[1][13]

Human interactions

Photo of an angelshark swimming just above the bottom
An angelshark off Tenerife in the Canary Islands, one of the few remaining locations with a substantial population

The angelshark is generally not aggressive towards humans, though it can deliver a severe bite if disturbed.[2] When approached underwater, the angelshark usually remains still or swims away, though one circling a diver with its mouth open is recorded.[8] Fishery workers, in particular, should treat it with caution; in the 1776 edition of British Zoology, Thomas Pennant wrote that it is "extremely fierce and dangerous to be approached. We know of an instance of a fisherman, whose leg was terribly torn by a large one of this species, which lay within his nets in shallow water, and which he went to lay hold of incautiously."[14]

Humans have used the angelshark for thousands of years.

fishmeal.[4][17]

Conservation status

Sources from the 19th and early 20th centuries indicate that the angelshark was once abundant all around the coasts of

trammel nets, and bottom longlines; the low reproductive rate of this shark limits its capacity to withstand population depletion.[1]
This has also led to habitat loss caused by the development of coastal areas for commercialism and tourism.

Angelshark numbers have declined precipitously across most of its range; it is now believed to be extinct in the North Sea and most of the northern Mediterranean, and has become extremely rare elsewhere. During the comprehensive Mediterranean International Trawl Survey program from 1995 to 1999, only two angelsharks were captured from 9,905 trawls. Similarly, another survey by the Italian National Project (National Group for Demersal Resource Evaluation) around the same period caught angelsharks in only 38 of 9,281 trawls. Fishery data compiled by the Working Group for Elasmobranch Fishes (WGEF) show that no angelsharks have been landed in the Northeast Atlantic since 1998.[1] Fewer than a dozen angelsharks are thought to remain in Irish waters.[18] Healthy subpopulations of angelsharks are thought to still persist in areas off North Africa and around the Canary Islands, though a more thorough assessment is urgently needed.[1][19]

As a result of these steep population declines and the ongoing threat from

Convention for the Protection of the Marine Environment of the North-East Atlantic Priority List of Threatened and Endangered Species.[1] A captive breeding program has been initiated at Deep Sea World, North Queensferry, with the first live pups born in 2011.[22]

In 2019, a population of angelsharks was discovered off the coast of Wales, indicating that the species had begun a potential return to the region.[23]

References

  1. ^
    doi:10.2305/IUCN.UK.2019-1.RLTS.T39332A117498371.en
    . Retrieved 13 November 2021.
  2. ^
    ISBN 978-92-5-101384-7
    .
  3. ^ Smith, H.M. (1907). North Carolina Geological and Economic Survey Volume II: The Fishes of North Carolina. E.M. Uzzell & Co., State Printers and Binders. pp. 37–38.
  4. ^ a b c Froese, Rainer; Pauly, Daniel (eds.) (2009). "Squatina squatina" in FishBase. July 2009 version.
  5. PMID 19647086
    .
  6. ^
    ISBN 978-0-262-12162-0
    .
  7. ISBN 978-0-691-12072-0
    .
  8. ^ a b c Murch, A. Common Angel Shark Information and Pictures. Elasmodiver.com. Retrieved on July 8, 2009.
  9. doi:10.1093/icesjms/46.2.155
    .
  10. S2CID 54077382
    .
  11. ^ Henderson, A.C. & J. Dunne (2001). "The distribution of the microbothriid shark parasite Leptocotyle minor on its host, the lesser-spotted dogfish Scyliorhinus canicula". Biology and Environment: Proceedings of the Royal Irish Academy. 101B (3): 251–253.
  12. S2CID 35127351
    .
  13. doi:10.1111/j.1095-8649.1990.tb05865.x
    .
  14. ^ Lineaweaver, T.H. (III) & R.H. Backus (1970). The Natural History of Sharks. J.B. Lippincott. p. 178.
  15. ISBN 978-0-415-23259-3
    .
  16. ISBN 978-0-7885-0615-4
    .
  17. ISBN 978-1-58008-450-5
    .
  18. ^ Kelleher, L. (December 23, 2013). "Only 12 left of Irish shark species that's 4m years old". Irish Examiner. Retrieved December 30, 2013.
  19. ^ Narváez, K., F. Osaer, B. Goldthorpe, E. Vera and R. Haroun. (2007). Sighting of the angel shark Squatina squatina by Davy Jones Diving in the island of Gran Canaria. Davy Jones Diving. Retrieved on July 8, 2009.
  20. ^ Ruddock, J. (Feb. 21, 2008) The Wildlife and Countryside Act 1981 (Variation of Schedule 5) (England) Order 2008 No. 431. Office of Public Sector Information. Retrieved on July 7, 2009.
  21. ^ The making of the Wildlife and Countryside Act 1981 (Variation of Schedule 5) (Wales) Order 2008. Welsh Assembly Government. Retrieved on July 24, 2009.
  22. ^ "Rare shark born in Deep Sea World in UK first". BBC News. November 18, 2011. Retrieved December 5, 2011.
  23. ^ Briggs, Helen (25 January 2019). "Rare angel sharks found living off Wales". BBC News. Retrieved 25 January 2019.

External links

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