Overview

Brief Summary

Biology

The critically endangered angel shark is nocturnal, and spends its days lying buried in the mud or sand with just its eyes protruding. From this position it can ambush its prey, and will burst out at a startling speed to engulf flatfishes, skates, crustaceans or molluscs. At night, it swims strongly off the bottom. In the northern parts of its range the angel shark is seasonally migratory, and moves northwards during the summer (2). The angel shark is ovoviviparous, a method of reproduction in which the young develop within eggs that remain inside the body until they hatch. Gestation lasts eight to ten months, and females give birth to pups that are 24 to 30 centimetres long. The number of pups in each litter varies from 7 to 25 pups, with larger females having larger litters (3). Whilst the small size of angel sharks means that they are not a particularly dangerous species, their strong jaws and sharp, needle-like teeth can inflict a painful bite on a provoking human (5).
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Description

With its exceptionally flat body and large pectoral fins, the angel shark resembles a large ray more than a shark. Its skin is grey to reddish or greenish-brown, scattered with small white spots and blackish dots. Young angel sharks may also have white net-like markings and large, dark blotches, whilst adults are plainer (3). The dorsal fins have a dark leading edge and a pale trailing edge. It possesses simple, whisker-like projections near the nostrils, (nasal barbels), which are used to taste and feel (3). Large, round eyes with vertical slit pupils provide good all-round vision, enabling the angel shark to be an efficient ambush predator (4).
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Comprehensive Description

Squatina squatina ZBK (Linnaeus, 1758)

Istanbul Fish Market : 1700-30 (1 spc.), 1981 .

  • Nurettin Meriç, Lütfiye Eryilmaz, Müfit Özulug (2007): A catalogue of the fishes held in the Istanbul University, Science Faculty, Hydrobiology Museum. Zootaxa 1472, 29-54: 32-32, URL:http://www.zoobank.org/urn:lsid:zoobank.org:pub:428F3980-C1B8-45FF-812E-0F4847AF6786
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Biology

A benthic species that occurs inshore, on coasts and along the continental shelf; may enter estuaries (Ref. 247, 58085). Found mainly on sand or mud bottoms; sluggish by day, lying buried with eyes protruding. Also utilizes areas with macroalgae, kelp or rocks (Ref. 88920). Nocturnal species, swims off bottom at night. Feeds mainly on flatfishes and other benthic fishes, but also on skates, crustaceans and molluscs, with one record of swallowed cormorant (Ref. 247, 28070). Moves to deeper waters during winter, returning to the shallower depths in the spring (Ref. 88187), moving northwards in summer. Ovoviviparous (Ref. 50449). Females generally grow larger than males (Ref. 58137). Detects weak electric fields generated by other organisms (e.g. potential prey) (Ref. 10311). Utilized fresh and dried salted for human consumption, and possibly for oil and fishmeal (Ref. 247). Reaches 250 cm (Ref. 35388).
  • Compagno, L.J.V. 1984 FAO Species Catalogue. Vol. 4. Sharks of the world. An annotated and illustrated catalogue of shark species known to date. Part 1 - Hexanchiformes to Lamniformes. FAO Fish. Synop. 125(4/1):1-249. Rome: FAO. (Ref. 247)
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Description

 With its flat body, broad trunk and large, very high pectoral fins, Squatina squatina resembles a large ray more than a shark. Its skin is grey to reddish or greenish-brown and is scattered with small white spots and blackish dots. The dorsal fins have a dark leading edge and a pale trailing edge. Whisker-like nasal barbels project from near the nostrils. The monkfish, or angelfish as it is sometimes known, has large, round eyes with vertical slit pupils. It can grow up to 1.8 m in length and 80 kg in weight.Young angel sharks may also have white net-like markings and large, dark blotches, whilst adults are plainer (Compagno, 1984).
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Distribution

Range Description

Original range from Scandinavia to North-western Africa (Mauritania and the Canary Islands), including the Mediterranean and Black Seas. Current distribution appears to be reduced from this historic range, as a result of severe population depletion, local extirpations, and some contraction in range; for example it is now considered to be extinct in the North Sea (ICES ACFM 2005) and is no longer encountered in most areas of the northern Mediterranean.
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Northeast Atlantic: southern Norway, Sweden and Shetland Islands to Morocco and West Sahara, including the Canary Islands, the Mediterranean and the Black Sea (Ref. 247). Range and abundance declining severly throughout its range; proposed legal protection in Britain (Ref.58085). Appendix III (Mediterranean) of the Bern Convention (2002). Annex V of the OSPAR Convention (2010).
  • Compagno, L.J.V. 1984 FAO Species Catalogue. Vol. 4. Sharks of the world. An annotated and illustrated catalogue of shark species known to date. Part 1 - Hexanchiformes to Lamniformes. FAO Fish. Synop. 125(4/1):1-249. Rome: FAO. (Ref. 247)
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Western Baltic Sea, North Sea, Mediterranean Sea, Black Sea, eastern Atlantic: Norway to Canary Islands and Western Sahara.
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Range

Occurs in the north-eastern Atlantic. Historically, its range extended from Norway to Mauritania, the Canary Islands, Mediterranean and Black Sea. However it has now vanished from some areas, and is uncommon in the remainder of its range (1) (3).
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Physical Description

Morphology

Dorsal spines (total): 0; Dorsal soft rays (total): 0
  • Compagno, L.J.V. 1984 FAO Species Catalogue. Vol. 4. Sharks of the world. An annotated and illustrated catalogue of shark species known to date. Part 1 - Hexanchiformes to Lamniformes. FAO Fish. Synop. 125(4/1):1-249. Rome: FAO. (Ref. 247)
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Size

Maximum size: 1830 mm TL
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Max. size

183 cm TL (male/unsexed; (Ref. 247)); 244 cm TL (female); max. published weight: 80.0 kg (Ref. 35388)
  • Compagno, L.J.V. 1984 FAO Species Catalogue. Vol. 4. Sharks of the world. An annotated and illustrated catalogue of shark species known to date. Part 1 - Hexanchiformes to Lamniformes. FAO Fish. Synop. 125(4/1):1-249. Rome: FAO. (Ref. 247)
  • Muus, B.J. and J.G. Nielsen 1999 Sea fish. Scandinavian Fishing Year Book, Hedehusene, Denmark. 340 p. (Ref. 35388)
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Diagnostic Description

Broad flattened body, with enlarged pectoral and pelvic fins, no anal fin. Eyes and large spiracles dorsally. Gill openings at the sides of the head. The mouth is terminal. Coloration variable, from grey to reddish or greenish-brown with scattered small white spots and blackish dots dorsally (Ref. 78469). No ocelli on body (Ref. 247).
  • Compagno, L.J.V. 1984 FAO Species Catalogue. Vol. 4. Sharks of the world. An annotated and illustrated catalogue of shark species known to date. Part 1 - Hexanchiformes to Lamniformes. FAO Fish. Synop. 125(4/1):1-249. Rome: FAO. (Ref. 247)
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
A temperate-water bottom-dwelling angel shark of the European and North African continental shelves, occurring on or near the bottom from close inshore (5 m) in the intertidal or subtidal zone to at least 150 m depth. This shark prefers mud or sandy bottom, where it lies buried with little more than its eyes protruding. It may penetrate estuaries and brackish water. The angelshark is nocturnal and can be found swimming strongly up off the bottom at night, but is torpid in the daytime and rests on the bottom. In the northern parts of its range the angelshark is seasonally migratory, and makes northwards incursions during the summer. (Compagno in prep.).

Most life history data were provided by Capape et al. (1990) for the Mediterranean. Females reach maturity at 128 to 169 cm, and males at 80 to 132 cm (Lipej et al. 2004), with maximum sizes of 183 cm and possibly up to 244 cm (Compagno 1984, in prep.), with estimates of less than 240 cm in the Mediterranean Sea (Tortonese 1956). Age at maturity and longevity are unknown. This shark is ovoviviparous, with both ovaries functional. It has moderate-sized litters of 7 to 25 young which vary according to the size of the female (Tortonese 1956, Bini 1967, Capapé et al. 1990, Compagno in prep). Records of size at birth are 24 to 30 cm (Compagno in prep.) and 24 cm (Tortonese 1956, Bini 1967). Gestation period is 8 to 10 months (Capapé et al. 1990, Compagno in prep.), born in December to February in the Mediterranean but apparently later in northern parts of its range (July in England). Reproductive age and periodicity, rate of population increase and mortality are unknown.

The angelshark feeds primarily on bony fishes, especially flatfishes (Ellis et al. 1996) but also other demersal fishes and skates, crustaceans and molluscs. Specific items include hake (Merlucius merlucius, Merluciidae), sparids (Pagellus erythrinus, Sparidae), grunts (Pomadasys sp., Haemulidae) flatfish (Bothus sp., Bothidae, Citharus linguatula, Citharidae), sole (Solea solea, Soleidae), squid (Loligo vulgaris), cuttlefish (Sepia officinalis, Sepiola spp.), and crustaceans (Dorippe lanata, Geryon tridens, Dromia vulgaris, Goneplax rhomboides, Macropipus corregatus, Atelecyclus rotundatus). It occasionally swallows odd items, including eelgrass and seabirds (a cormorant was once recorded) (Compagno in prep.).

Systems
  • Marine
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Environment

demersal; oceanodromous (Ref. 51243); marine; depth range 5 - 150 m (Ref. 247)
  • Compagno, L.J.V. 1984 FAO Species Catalogue. Vol. 4. Sharks of the world. An annotated and illustrated catalogue of shark species known to date. Part 1 - Hexanchiformes to Lamniformes. FAO Fish. Synop. 125(4/1):1-249. Rome: FAO. (Ref. 247)
  • Riede, K. 2004 Global register of migratory species - from global to regional scales. Final Report of the R&D-Projekt 808 05 081. Federal Agency for Nature Conservation, Bonn, Germany. 329 p. (Ref. 51243)
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Depth range based on 3 specimens in 1 taxon.
Water temperature and chemistry ranges based on 1 sample.

Environmental ranges
  Depth range (m): 0 - 146
  Temperature range (°C): 16.273 - 16.273
  Nitrate (umol/L): 11.916 - 11.916
  Salinity (PPS): 36.219 - 36.219
  Oxygen (ml/l): 3.476 - 3.476
  Phosphate (umol/l): 0.711 - 0.711
  Silicate (umol/l): 4.349 - 4.349

Graphical representation

Depth range (m): 0 - 146
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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 Found on the continental shelves from close inshore to at least 150 m depth. During day time, found almost buried in a mud or sandy bottom often with hardly more than its eyes protruding. Will often be seen swimming off the bottom at night time.
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Depth: 0 - 150m.
Recorded at 150 meters.

Habitat: demersal.
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The angel shark occurs in temperate waters, over mud or sand, from coasts and estuaries to depths of over 150 metres (2).
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Migration

Oceanodromous. Migrating within oceans typically between spawning and different feeding areas, as tunas do. Migrations should be cyclical and predictable and cover more than 100 km.
  • Riede, K. 2004 Global register of migratory species - from global to regional scales. Final Report of the R&D-Projekt 808 05 081. Federal Agency for Nature Conservation, Bonn, Germany. 329 p. (Ref. 51243)
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Trophic Strategy

Cryptic ambush predator that may remain motionless for long periods of time, usually buried under sand or mud with only its eyes protruding (Ref. 247). Waits until potential prey is within striking distance before lunging for it (Ref. 88171).
  • Ellis, J.R., M.G. Pawson and S.E. Shackley 1996 The comparative feeding ecology of six species of shark and four species of ray (Elasmobranchii) in the north-east Atlantic. J. Mar. Biol. Ass. U.K. 76(1):89-106. (Ref. 28070)
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Life History and Behavior

Life Cycle

Ovoviviparous, produce 7-25 pups/litter, with litter number increasing with female size; gestation 8-10 months (born Dec-Feb in Mediterranean, July in England), size at birth about 24-30 cm TL (Ref. 58085). Embryos feed solely on yolk (Ref. 50449). Full term embryos weighed 189-200 g; no egg capsules found around ova or embryos; a biannual reproductive cycle is likely the case for this species (Ref. 32746).
  • Breder, C.M. and D.E. Rosen 1966 Modes of reproduction in fishes. T.F.H. Publications, Neptune City, New Jersey. 941 p. (Ref. 205)
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Molecular Biology and Genetics

Molecular Biology

Barcode data: Squatina squatina

The following is a representative barcode sequence, the centroid of all available sequences for this species.


There are 6 barcode sequences available from BOLD and GenBank.

Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.

See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

ACCCTTTACTTAATCTTCGGTGCATGAGCAGGAATAGTGGGCACCGCCCTA---AGTTTACTTATTCGAGCAGAATTAAGCCAGCCTGGTACCCTTCTTGGGGAT---GATCAAATTTACAATGTAATCGTTACTGCCCACGCTTTGGTGATAATTTTTTTTATAGTAATACCCATCATAATTGGGGGATTTGGGAATTGATTAGTCCCCTTAATA---ATTGGTGCACCAGATATAGCTTTCCCACGAATAAATAATATAAGTTTCTGACTTTTGCCTCCTTCCTTACTTTTACTACTTGCCTCAGCCGGAGTTGAAGCAGGAGCCGGCACTGGTTGAACGGTTTACCCTCCTCTTGCAGGAAATTTAGCTCACGCCGGAGCATCGGTAGATTTA---GCAATTTTTTCCTTACATCTAGCTGGTATTTCTTCAATCCTAGCCTCTATTAATTTCATTACAACCATTATTAATATAAAACCCCCAGCCATTTCCCAGTATCAAACACCACTCTTTGTTTGATCAATCCTTGTAACTACTGTTCTCCTCCTCCTTTCTCTTCCGGTCCTCGCAGCT---GCAATCACAATATTATTAACTGACCGTAACTTAAACACAACATTTTTTGACCCTGCAGGAGGTGGAGACCCAATCCTTTATCAGCATTTG------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------TTC
-- end --

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Statistics of barcoding coverage: Squatina squatina

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 27
Specimens with Barcodes: 27
Species With Barcodes: 1
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
CR
Critically Endangered

Red List Criteria
A2bcd+3d+4bcd

Version
3.1

Year Assessed
2006

Assessor/s
Morey, G., Serena, F., Mancusi, C., Fowler, S.L., Dipper, F. & Ellis, J.

Reviewer/s
Cavanagh, R.D., Valenti, S.V. & participants of the Shark Specialist Group Northeast Atlantic workshop (Shark Red List Authority)

Contributor/s

Justification
This large stocky angel shark was formerly a common and important demersal predator over large areas of its coastal and outer continental shelf sediment habitat in the Northeast Atlantic, Mediterranean and Black Seas. Most of this region is now subject to intense demersal fisheries, and the species is highly vulnerable from birth onwards to bycatch in the benthic trawls, set nets and bottom longlines operating through most of its range and habitat. As a result of its limiting life history characteristics and bycatch in fisheries with steadily increasing effort and capacity, its abundance has declined dramatically during the past 50 years to the point where it has been declared extinct in the North Sea and has apparently been extirpated from large areas of the northern Mediterranean. It is now extremely uncommon throughout most of the remainder of its range, with the possible exception of some areas of the southern Mediterranean and Canary Islands where its status should be confirmed and conservation measures introduced as a matter of urgency.

History
  • 2000
    Vulnerable
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In 2012, Squatina squatina was included among the world's 100 most threatened species, in a report by the IUCN Species Survival Commission and the Zoological Society of London.

(Baillie & Butcher 2012; Harvey 2012)

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Status

Classified as Critically Endangered (CR) on the IUCN Red List (1).
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Population

Population
Squatina squatina was reported to be common, or at least frequently or regularly recorded in many areas, during the 19th century and early 20th centuries. For example, It was particularly common on the south and east English coasts (Yarrell 1836, Day 1880-04), and also common in the North Sea, on the Dogger Bank, in the Bristol Channel and Cornwall, and "by no means uncommon" in the Firth of Clyde (Day 1880-4). Historically it has also been caught in Tralee Bay and Clew Bay, Ireland. It was still being caught regularly and considered common in the UK at the beginning of the 20th century (Garstang 1903). Although more common off the Atlantic Iberian coasts, Squatina squatina was also reported as frequent in the Mediterranean during the first half of the 20th century by Lozano Rey (1928). Steep population declines have, however, now been reported from several parts of this species' range, including in the North Sea (ICES ACFM 2005) UK coastal waters (Rogers and Ellis 2000), the French coast (Quero and Cendrero 1996, Capapé et al. 2000), and large areas of the Mediterranean (e.g., Vacchi et al. 2002). During the early 1900s, an average of one specimen was taken during every ten hours of trawl survey, but in recent years the species has virtually vanished (Rogers and Ellis, 2000). CEFAS surveys recorded angel sharks in low numbers in Cardigan Bay during the 1980s (Ellis et al. 1996) but report just one individual in the last 15 years. The population is clearly becoming increasingly fragmented and records are now extremely infrequent (for more information, see "Threats"). It has now virtually disappeared from much of its former range in the Northeast Atlantic and Mediterranean. Off the North Africa coastline the species may be more common, e.g., as reported off the coast of Tunisia (although it is considered rare in the Gulf of Gabès) (Bradai 2000).

Vacchi et al. (2002) reported the dramatic decline in the elasmobranch catch of a tuna trap operating in Baratti (Northern Tyrrhenian Sea) between 1898 and 1922. For the genus Squatina, catches decreased from an average of 134 specimens from the period 1898 to 1905, to 95 between 1906 and 1913, and down to 15 between 1914 and 1922.

Declines have also been reported from studies off the Balearic Islands where this species, previously relatively frequent, may now be absent. Off the Balearic Islands Squatina squatina was historically documented in checklists (Delaroche 1809, Ramis 1814, Barceló I Combis 1868, Fage 1907, De Buen 1935). Captures of S. squatina spp. were relatively frequent until the 1970s, becoming increasingly sporadic during the 1980s in coastal artisanal fisheries (trammel nets and gillnets), lobster tanglenets, trawls and bottom longline fisheries. Since the mid 1990s no reports of Squatina spp. have been reported in the area (Gabriel Morey, pers. comm). Recently, Massutí and Moranta (2003) reported no captures of Squatina spp. from four bottom trawl fishing surveys (131 hauls, at a depth range of 46 to 1,800 m) carried out between 1996 and 2001 around the Balearic Islands. In addition, the likely low interaction with stocks from other areas further affects the already low recovery capacity of isolated populations such as those around the Balearics.

Catch data for this species in the north Mediterranean exist for the period from 1985 to 1999, when two major trawl surveys were carried out: the Mediterranean International Trawl Survey (MEDITS) and the Italian National Project (National Group for Demersal Resource Evaluation (GRUND)).

During the MEDITS program (1995-1999), a broad scale survey of the north Mediterranean coastline from west Morocco to the Aegean Sea in depths of 10 to 800 m, S. squatina appeared in only two of a total of 9,095 tows, at a depth range of 50 to 100 m, resulting in an estimated standing biomass of 14 t throughout the survey area (Baino et al. 2001), which equates to 1,400 individuals assuming an average individual weight of 10 kg.

In the Italian survey, captures of S. squatina were reported in only 0.41% of 9,281 hauls (Relini et al. 2000). Squatina squatina was reported from trawl surveys carried out in the Adriatic Sea in 1948, but MEDITS trawls in 1998 indicated this species may now be absent from this area (Jukic-Peladic et al. 2001). Indeed, evidence points to angel sharks being absent nowadays from most of the northern Mediterranean coastline.

Landings in the Northeast Atlantic compiled by WGEF (2004) from 1978 to 2002 for all ICES Areas are variable because of recent misreporting of other species (primarily Lophius) as this non-quota species. After deleting these records, landings have declined from 15 to 20 t in the 1980s, to 1 to 2 t in the 1990s, with the last reported landing in 1998.

Population Trend
Decreasing
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Threats

Major Threats
Angel sharks are highly susceptible to bycatch in trawls as they lie on the bottom. Benthic trawl effort has increased in both intensity and efficiency on the shelf and slope area of the Northeast Atlantic and Mediterranean over the last 50 years. The species is also bycaught in trammel nets and bottom longlines throughout its range. Human disturbance by habitat degradation and tourism are also possible threats to its preferred sandy nearshore habitat.There is evidence for dramatic declines from historic data from a tuna trap operating in the Northern Tyrrhenian Sea with catches of the genus Squatina reported at an average of 134 specimens from 1898 to 1905, down to 15 between 1914 and 1922 (Vacchi et al. 2002). This early decline probably marks the beginning of trawling activity in the area, to which angel sharks are highly susceptible. A low rate of exchange between Squatina populations may makes them especially prone to local depletion and means that recolonisation will be extremely low.

Tunisia reported small catches of this species during the past decade (10 to 53 t), with the 1997 catch at 37 t; other Mediterranean countries that report 'angelsharks' to FAO with this species as part of the catch include Albania, Turkey, Malta and France. Landings in the Northeast Atlantic collated by WGEF (ICES 2004) may include some misreporting of other (quota) species (e.g., Lophius) as angel shark is a non-quota species, but otherwise landings have declined from an average of 17 t/annum in the 1980s, to 1 to 2 t in the 1990s.
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Critically Endangered (CR) (A2bcd+3d+4bcd)
  • IUCN 2006 2006 IUCN red list of threatened species. www.iucnredlist.org. Downloaded July 2006.
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The angel shark is not particularly sought after by fisheries, and since 1989 catches have only been reported from Tunisia. The small numbers caught are utilised for human consumption, and possibly also used for oil and fishmeal (5). A more widespread, potential threat is the capture of this species as by-catch (5). As they lie on the bottom, angel sharks are particularly vulnerable to by-catch in trawl fisheries, an activity that has increased in the last 50 years. As a result, numbers of angel sharks have declined dramatically, and have even been declared extinct in the North Sea (1).
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Management

Conservation Actions

Conservation Actions
The genus Squatina is protected within three Balearic Islands marine reserves, where fishing for these species is forbidden. Squatina squatina was proposed for strict protection under the UK Wildlife and Countryside Act in 2001; a decision is still (2006) awaited from government [Update by LRH May 27th 2010 - species now listed under UK Wildlife and Countryside Act, and will be protected against killing, injuring or taking (section 9(1)) on land and up to 3 nautical miles (nm) from English coastal baselines]. UK and Belgium proposed S. squatina for listing on the OSPAR Priority List of Threatened and Endangered Species, and although the proposal was deemed appropriate by the Study Group on Elasmobranch Fishes (ICES, 2002), the nomination was not accepted. Squatina squatina is listed on Annex III of the Barcelona Convention.

There is an urgent need to confirm the status of this species in the southern Mediterranean, Canary Islands and other areas where populations may still persist. If so appropriate conservation measures are needed to protect this species there.
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Conservation

All Squatina species are protected within three Balearic Islands marine reserves, where fishing for these species is forbidden (1). The status of the angel shark in many parts of its range is unknown (1), and the impact of fisheries is unclear (5), and thus research is required and conservation measures urgently need to be implemented (1), to assure the conservation of this unusual and distinctive shark.
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Relevance to Humans and Ecosystems

Benefits

Importance

fisheries: minor commercial; gamefish: yes; price category: medium; price reliability: reliable: based on ex-vessel price for this species
  • Food and Agriculture Organization of the United Nations 1992 FAO yearbook 1990. Fishery statistics. Catches and landings. FAO Fish. Ser. (38). FAO Stat. Ser. 70:(105):647 p. (Ref. 4931)
  • International Game Fish Association 1991 World record game fishes. International Game Fish Association, Florida, USA. (Ref. 4699)
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Wikipedia

Squatina squatina

This article is about the species. For the genus, see angel shark.

Squatina squatina, the angelshark or monkfish, is a species of shark in the family Squatinidae (known generally also as angel sharks), 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 7–25 pups every other year. The angelshark normally poses little danger to humans, though if provoked it is quick to bite. Caught for food since at least Ancient Greece, this shark was often sold on European markets under the name "monkfish". Since the mid-20th century, intense commercial fishing across the angelshark's range have 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 (IUCN) has assessed this species as Critically Endangered.

Taxonomy and phylogeny[edit]

The angelshark was originally described by the Swedish natural historian Carl Linnaeus, known as the "father of taxonomy", in the 1758 tenth edition of Systema Naturae as Squalus squatina. He did not designate a type specimen.[2] The word squatina is the angelshark's name in Latin, derived from the word for skate; it was made the genus name for all angel sharks by the French zoologist André Duméril in 1806.[3] Other common names used for this species include angel, angel fiddle fish, angel puffy fish, angel ray, angelfish, escat jueu, fiddle fish, monk, and monkfish.[4] Stelbrink and colleagues (2010) conducted a phylogenetic study based on mitochondrial DNA, and found that the 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[edit]

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).[4] This species shares in common with other angel sharks a flattened body and large, wing-like pectoral fins whose anterior lobes are not fused to the head. The head and body are very broad and stocky, with small eyes positioned dorsally and followed by a pair of larger spiracles.[6] There are a pair of unadorned barbels in front of the nares, as well as a smooth or weakly fringed flap. Folds of skin with 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 dorsal fins are positioned on the muscular tail behind the pelvic fins. The anal fin is absent, and the caudal fin has a larger lower lobe than upper. The 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[edit]

Historically, the angelshark occurred in the temperate waters of the northeastern Atlantic, from southern Norway and Sweden to the Western Sahara and the Canary Islands, including around the British Isles and in the Mediterranean and Black Seas. In recent times it has been extirpated from the North Sea and large portions of the northern Mediterranean.[1] This benthic shark inhabits the continental shelf, preferring soft substrates such as mud or sand, and can be found from near the coast to a depth of 150 m (490 ft). It sometimes enters brackish environments. Northern angelshark subpopulations migrate northward in summer and southward in winter.[2]

Biology and ecology[edit]

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.[2] Aggregations numbering up to a hundred have been observed off Gran Canaria in the summer.[8] Known parasites of this species include the tapeworms Grillotia smaris-gora, G. angeli, and Christianella minuta,[9] the fluke Pseudocotyle squatinae,[10] the monogenean Leptocotyle minor,[11] and the isopod Aega rosacea.[12]

The angelshark is an ambush predator that feeds mainly on bottom-dwelling bony fishes, especially flatfishes, though it also preys on skates and invertebrates. Prey reported taken include the hake Merluccius merluccius, the bream Pagellus erythrinus, grunts in the genus Pomadasys, the flatfishes Bothus spp., Citharus linguatula, and Solea solea, the squid Loligo vulgaris, the cuttlefishes 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 uterus and are nourished by a yolk sac until birth. Females have two functional ovaries, with the right ovary containing more oocytes and the right uterus correspondingly containing more embryos; this functional asymmetry is not present in other angel shark species. Unlike most sharks, in which vitellogenesis (yolk formation) occurs concurrently with pregnancy, in the angelshark the onset of vitellogenesis is delayed until halfway through the 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 7 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[edit]

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 unaggressive towards humans, though it can deliver a severe bite if disturbed.[2] When approached underwater the angelshark usually remains still or swims away, though there is a record of one circling a diver with its mouth open.[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 utilized the angelshark for thousands of years. Ancient Greek authors, such as Diphilus and Mnesitheus, described its meat as "light" and "easily digestible", and Pliny the Elder noted in his Naturalis Historia (77–79 AD) that its rough skin was valued by craftsmen for polishing wood and ivory. Aristotle recorded elements of its natural history, including that it bore live young, and correctly recognized that it was a shark despite its resemblance to rays and skates.[15][16] The use of this species for food has continued into modern times; it is sold fresh or dried and salted, often under the name "monkfish" (which also refers to the goosefishes of the genus Lophius). The angelshark may also be a source for shark liver oil and fishmeal.[4][17]

Conservation status[edit]

Sources from the 19th and early 20th centuries indicate that the angelshark was once abundant all around the coasts of Western Europe. Yarrell (1836), Day (1880–04), and Garstang (1903) all noted that the angelshark was common around the British Isles, and Rey (1928) recorded that this species was common around the Iberian Peninsula and in the Mediterranean. However, from the latter half of the 20th century onwards the angelshark has come under intense pressure from commercial fisheries operating across much of its range. Due to its benthic, near-shore habits, individuals of all ages are susceptible to incidental capture by bottom trawls, trammel nets, and bottom longlines; the low reproductive rate of this shark limits its capacity to withstand population depletion.[1]

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 (MEDITS) 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 demersal fisheries, the IUCN has assessed the angelshark as Critically Endangered. It is listed on Annex III of the 1976 Barcelona Convention, which aims to limit pollution in the Mediterranean Sea. This species is protected within three marine reserves in the Balearic Islands, although it has not been reported from this area since the mid-1990s.[1] In 2008, the angelshark also received full legal protection from human activities in the waters off England and Wales from the coast to a distance of 11 km (6.8 mi), under the UK Wildlife and Countryside Act.[20][21] The United Kingdom and Belgium have pushed, unsuccessfully, for this species to be listed on the Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR) 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]

References[edit]

  1. ^ a b c d e f g h i Morey, G., F. Serena, C. Mancusi, S.L. Fowler, F. Dipper, and J. Ellis (2006). Squatina squatina. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved July 7, 2009.
  2. ^ a b c d e f Compagno, L.J.V. (1984). Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date. Rome: Food and Agricultural Organization. pp. 150–151. ISBN 92-5-101384-5. 
  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 and Pauly, Daniel, eds. (2009). "Squatina squatina" in FishBase. July 2009 version.
  5. ^ Stelbrink, B., T. von Rintelen, G. Cliff, and J. Kriwet (2010). "Molecular systematics and global phylogeography of angel sharks (genus Squatina)". Molecular Phylogenetics and Evolution 54 (2): 395–404. doi:10.1016/j.ympev.2009.07.029. PMID 19647086. 
  6. ^ a b Lythgoe, J. and G. Lythgoe (1991). Fishes of the Sea: The North Atlantic and Mediterranean. Blandford Press. pp. 29–30. ISBN 0-262-12162-X. 
  7. ^ Compagno, L.J.V., M. Dando and S. Fowler (2005). Sharks of the World. Princeton University Press. p. 146. 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. ^ MacKenzie, K. (1990). "Cestode parasites as biological tags for mackerel (Scomber scombrus L.) in the Northeast Atlantic". Journal du Conseil International pour I'Exploration de la Mer 46: 155–166. 
  10. ^ Kearn, G.C. (1962). "Breathing movements in Entobdella soleae (Trematoda, Monogenea) from the skin of the common sole". Journal of the Marine Biological Association of the United Kingdom 42 (01): 93–104. doi:10.1017/S0025315400004471. 
  11. ^ Henderson, A.C. and 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. ^ Ramdane, Z. and J. Trilles (2008). "Cymothoidae and Aegidae (Crustacea, Isopoda) from Algeria". Acta Parasitologica 53 (2): 173–178. doi:10.2478/s11686-008-0033-8. 
  13. ^ Capapé, C., J.P. Quignard and J. Mellinger (1990). "Reproduction and development of two angel sharks, Squatina squatina and S. oculata (Pisces: Squatinidae), off Tunisian coasts: semi-delayed vitellogenesis, lack of egg capsules, and lecithotrophy". Journal of Fish Biology 37 (3): 347–356. doi:10.1111/j.1095-8649.1990.tb05865.x. 
  14. ^ Lineaweaver, T.H. (III) and R.H. Backus (1970). The Natural History of Sharks. J.B. Lippincott. p. 178. 
  15. ^ Dalby, A. (2003). Food in the Ancient World from A to Z. Routledge. p. 120. ISBN 0-415-23259-7. 
  16. ^ Matron, S., D. Olson and A. Sens (1999). Matro of Pitane and the Tradition of Epic Parody in the Fourth Century BCE: Text, Translation, and Commentary. Oxford University Press US. p. 108. ISBN 0-7885-0615-3. 
  17. ^ Davidson, A. (2004). North Atlantic Seafood: A Comprehensive Guide with Recipes (third ed.). Ten Speed Press. p. 171. ISBN 1-58008-450-8. 
  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. 
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