Sawback angelshark

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Sawback angelshark
Squatina aculeata.004 - Aquarium Finisterrae.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Subdivision: Selachimorpha
Order: Squatiniformes
Family: Squatinidae
Genus: Squatina
Species:
S. aculeata
Binomial name
Squatina aculeata
Cuvier, 1829
Squatina aculeata 2019 range.jpg
Range of sawback angelshark (in gold)

The sawback angelshark (Squatina aculeata) is an angelshark of the family Squatinidae [2] It is one of rarest species of sharks known to date, and one of the three species of angelsharks that inhabits the Mediterranean. The Sawback angelshark lives in sandy and muddy bottoms of the ocean at depths of 30-500m. [3]

Contents

Measurements

Their size at birth ranges from 30 to 35 cm. As adults, female measurements range from 137 to 143 cm, while males range from 120 to 122 cm. [4] Their relative weight based on the size of the shark for males is between 12.7 kg and 24.0 kg. In females, they weigh anywhere from 22 to 32 kg. [5] The females grow to be larger than the males because they need to be able to carry and support their young.

Development

The development of the males was measured in three stages, juvenile, subadult and adult. The juvenile males had short and flexible claspers and the testes were membranous and barely developed. The subadult males showed changes in the claspers involving slight calcification and elongation in the sharks. It is in the adult stage that the claspers are fully elongated and calcified, and are rigid. The spermatozoa had developed and sperm production became possible in these adult sharks.

The three development stages for females are the same for males: juvenile, subadult and adult. The juvenile females have whitish ovaries, and extremely small ovaries, which need to be seen under a microscope. In the subadult females, they have primarily white, translucent follicles, differentiated genital areas, and developed ovarian glands. In adult females, the fully functional ovaries exhibits developing and fully developed follicles. [5]

Appearance

Their eyes are larger than their spiracle. The frontal cephalic membranes are lobed; external nasal flap fringed; spiracle with 13-14 pseudo branchial lamellae. Has concave between eye, eye spiracle distance <1.5 x eye length. They have between 19 and 24 teeth, the average of the species being 21 total teeth. Their pectoral fin base at is least half of their fin length. They have denticles on their back which are large-based, almost pyramidal, with a line of median spines. The lower belly of the shark has denticles only on outer edges of pectoral and pelvic fins Obtains large thorns atop its head in a row down its back. The colour of the angelshark is light brown mottled with dark brown, with white sports arranged on the head and some of the body. Obtains dark blotches on head, back, the fin bases and tail. The species contains no ocelli. [6]

Distribution and range

The range of the sawback angelshark continues to decrease as their population declines. They range along the Eastern Atlantic in Senegal, Gambia, and Sierra Leone. They also inhabit the Southern Mediterranean coastline in Algeria to the eastern basin, and along the northern coast from Turkey possibly to Albania, although their presence is unknown further east. Its presence is unknown in Algeria, Sardinia, Malta, Libya, Egypt, Palestine, Lebanon, Syria, southern Cyprus, Crete, ad Western Mainland Greece. [1]

Climate and habitat

Subtropical; offshore species, outer continental shelf and upper slope, demersal, marine. Usually found on muddy bottoms. 30–500 m (98–1,640 ft) down.

Behavior

As with other angelsharks, the sawback angelshark is a bottom-dweller that tries to camouflage at the bottom of the ocean in order to ambush and capture its prey.

Feeding

Sawback angelsharks are ambush predators, meaning they lie on the ocean floor and wait for their prey to pass by. They feed on small sharks, bony fishes, cephalopods, and crustaceans. [7]

Reproduction

Sawback angelshark reproduction is ovoviviparous. This means the young develop inside the mother as eggs until they are ready to hatch. The average generation of the sawback angelshark is 15 years, so they have a low population doubling time. Females produce live young, and their litter size ranges from 8 to 12 pups. [7] The female fecundity ranges from 12 to 22, and larger females sharks tend to have a higher fecundity and produce more offspring than smaller females.

Status

IUCN Red List: Critically Endangered. Added to endangered species list in 2007 due to overexploitation. [1] One major source of their decline has been contamination in the North-Eastern Mediterranean. Due to agricultural, industrial and urban wastes, the Mediterranean has seen an untick in the amount of toxic heavy metals. The metals most present are Iron (Fe), Zinc (Zn), and Mercury (Hg). These metals have been found in dangerous quantities in Angelsharks gills, liver and muscle tissues.

Another major contributing factor to the decline of the species has been fisheries and overfishing in the Mediterranean. This comes from illegal, unreported and unregulated (IUU) fishing, commercial fishing (lack of species identification, as well as the impact of different gear types), recreational fishing, subsidence/food security and small scale fishing. Human intrusion into the angel sharks environment has also caused a significant disruption to their habitat and breeding spaces. Lastly, residential and commercial development has added to the decline of the species including coastal building and infrastructure development, renewable energy sources like underwater turbines. Combined, these have led to the decline in population numbers causing a lack of genetic diversity in the species. [8]

Threat to Humans

The sawback angelshark is a harmless species, but may be dangerous to humans if provoked or their habitat is disturbed.

Related Research Articles

<span class="mw-page-title-main">Angelshark</span> Genus of sharks

Angelsharks are sharks belonging to the genus Squatina. They are the only living members of the family Squatinidae and order Squatiniformes. They commonly inhabit sandy seabeds close to 150 m (490 ft) in depth.

<span class="mw-page-title-main">Izak catshark</span> Species of catshark, of the family Scyliorhinidae

The Izak catshark or simply Izak is a species of catshark, belonging to the family Scyliorhinidae, common off the coasts of South Africa and southern Namibia. It typically inhabits the outer continental shelf at depths of 100–300 m (330–980 ft), with the males found deeper than the females and juveniles. The Izak catshark has a short, wide, flattened head and a robust body tapering to a long, slender tail. It can be identified by its ornate color pattern of dark brown spots or reticulations and blotches on a light yellowish background, as well as by the enlarged dermal denticles over its pectoral fins and along its dorsal midline from the snout to the second dorsal fin. This species reaches 69 cm (27 in) in length, with the males larger than females.

<span class="mw-page-title-main">Sand devil</span> Species of shark

The sand devil or Atlantic angel shark is a species of angelshark, family Squatinidae, native to the northwestern Atlantic Ocean. It occurs off the eastern United States, in the northern Gulf of Mexico, and possibly in parts of the Caribbean Sea. This bottom-dwelling shark is found in shallow inshore waters in summer and fall, and deep offshore waters in winter and spring. The sand devil's flattened body and enlarged pectoral and pelvic fins give it a ray-like appearance. There is a band of enlarged thorns running along the middle of its back. It is gray or brown in color, with scattered small dark spots. This species reaches 1.2–1.5 m (3.9–4.9 ft) in length.

<span class="mw-page-title-main">Cloudy catshark</span> Species of shark

The cloudy catshark is a common species of catshark, belonging to the family Scyliorhinidae. It is a bottom-dweller that inhabits rocky reefs in the northwestern Pacific Ocean, from the shore to a depth of 320 m (1,050 ft). Growing up to 50 cm (20 in) long, this small, slim shark has a narrow head with a short blunt snout, no grooves between the nostrils and mouth, and furrows on the lower but not the upper jaw. It is also characterized by extremely rough skin and coloration consisting of a series of dark brown saddles along its back and tail, along with various darker and lighter spots in larger individuals.

<span class="mw-page-title-main">Gecko catshark</span> Species of shark

The gecko catshark is a species of catshark, part of the family Scyliorhinidae, native to the northwestern Pacific Ocean from southern Japan to Taiwan, and possibly also off Vietnam. It is a common, demersal species found at depths of 100–900 m (330–2,950 ft). Its body is slender, with a pattern of dark saddles and blotches. The dorsal and caudal fins are edged in white, and there is a prominent crest of enlarged dermal denticles along the dorsal edge of the caudal fin. The gecko catshark is a schooling, opportunistic predator of bony fishes, cephalopods, and crustaceans. It is oviparous, with females producing two vase-shaped egg capsules at a time. This species is captured as bycatch, but does not appear to be threatened by fishery activities at present and has been assessed as Least Concern by the International Union for Conservation of Nature (IUCN).

<span class="mw-page-title-main">Broadfin sawtail catshark</span> Species of shark

The broadfin sawtail catshark is a common species of catshark, part of the family Scyliorhinidae. It is found on or near the bottom at depths of 150–540 m (490–1,770 ft), from southeastern Japan to the East China Sea. A slender species growing to 68 cm (27 in) long, this shark is characterized by a fairly long, pointed snout, a series of indistinct, dark saddles along its back and tail, and a prominent crest of enlarged dermal denticles along the dorsal edge of its caudal fin. In addition, adult males have very long claspers that reach past the anal fin. The broadfin sawtail catshark is an opportunistic predator of bony fishes, cephalopods, and crustaceans, with immature and mature sharks being primarily piscivorous. It is oviparous and reproduces year-round.

<span class="mw-page-title-main">Eastern angelshark</span> Species of shark

The eastern angelshark is an angelshark of the family Squatinidae.

<span class="mw-page-title-main">Australian angelshark</span> Species of shark

The Australian angelshark 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.

<span class="mw-page-title-main">Pacific angelshark</span> Species of shark

The Pacific angelshark 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).

<span class="mw-page-title-main">Taiwan angelshark</span> Species of shark

The Taiwan angelshark 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.

<span class="mw-page-title-main">Japanese angelshark</span> Species of shark

The Japanese angelshark 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.

<span class="mw-page-title-main">Angular angelshark</span> Species of shark

The angular angelshark or Squantina guggenheim are sharks of the Squantina genus in the Squantinidae family. They originate in Brazil, Uruguay and Argentina while living in marine, brackish and demersal environments at depth of approximately 4-360m. Their typical food sources consist of bony fish, crustaceans, and mollusks.

<span class="mw-page-title-main">Smoothback angelshark</span> Species of shark

The smoothback angelshark is an angelshark of the family Squatinidae found in the eastern Atlantic and Mediterranean.

<i>Squatina squatina</i> Species of shark

Squatina squatina, the angelshark or monkfish, is a species of shark in the family Squatinidae, 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, and grayish or brownish dorsal coloration with a pattern of numerous small light and dark markings. It measures up to 2.4 m (7.9 ft) long.

<span class="mw-page-title-main">Ornate angelshark</span> Species of shark

The ornate angelshark 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). Females tend to have a TL at 1150–1250 mm, while males range from a TL of 810–910 mm at sexual maturity. Reproduction is ovoviviparous, with two to nine pups per litter.

<span class="mw-page-title-main">Spiny butterfly ray</span> Species of cartilaginous fish

The spiny butterfly ray or giant butterfly ray is a species of butterfly ray, family Gymnuridae, native to the shallow coastal waters of the Atlantic Ocean. A large ray that can measure over 2 m across, it may be distinguished from the sympatric smooth butterfly ray by the spine at the base of its tail and by a small tentacular structure on the margin of each spiracle. Slow-reproducing and valued for its meat, in recent decades its population has experienced a decline of over 30%, and it has become Critically Endangered in certain parts of its range.

<span class="mw-page-title-main">Indonesian angelshark</span> Species of shark

The Indonesian angelshark 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) has classified it as Critically Endangered due to significant fishing pressure.

The Philippines angelshark is a species of angelshark, family Squatinidae, known only from a 33 cm (13 in) long immature female caught in the Philippines, where it is the only known representative of its family. It has a flattened body and head with greatly expanded pectoral and pelvic fins, and is greenish above with brown spots. Identifying traits of this species include the spiracles, which are more widely spaced than the eyes and bear papillae on the posterior inner rims, and the relative positions of the two dorsal fins. Additionally, S. caillieti lacks fringes on its barbels, enlarged thorns along the middle of its back, and ocelli ("eyespots") on its fins.

<i>Squatina mapama</i> Species of angelshark

Squatina mapama is a species of angelshark found in the Caribbean. It was described by Douglas J. Long, David A. Ebert, Jose Tavera, Arturo Acero Pizarro, and David Ross Robertson in December 2021.

<span class="mw-page-title-main">Vari's angelshark</span> Species of angelshark

Vari's angelshark is an angelshark in the family Squatinidae found in Southwestern Atlantic, specifically Brazil. It lives in the continental slope between latitudes 11° and 22°S, at the depths of 195–666 m (640–2,185 ft).

References

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  2. "Species Squatina aculeata Cuvier". FishWisePro. 1829. Retrieved 19 April 2020.
  3. Başusta, Nuri (2016-06-01). "New records of neonate and juvenile sharks (Heptranchias perlo, Squatina aculeata, Etmopterus spinax) from the North-eastern Mediterranean Sea". Marine Biodiversity. 46 (2): 525–527. doi:10.1007/s12526-015-0391-z. ISSN   1867-1624. S2CID   255581818.
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  5. 1 2 Christian Capapé, Y. Diatta, A.A. Seck, Olivier Guélorget (June 2005). "Reproduction of the sawback angelshark Squatina aculeata (Chondrichthyes: Squatinidae) off Senegal and Tunisia". Research Gate. Retrieved 11 November 2022.{{cite web}}: CS1 maint: multiple names: authors list (link)
  6. Irmak, Erhan. "Occurence [sic] of Squatina aculeata Cuvier, 1829 (Elasmobranchii, Squatinidae) from the Aegean Sea, Turkey".{{cite journal}}: Cite journal requires |journal= (help)
  7. 1 2 Fisheries, NOAA (2022-01-26). "Sawback Angelshark | NOAA Fisheries". NOAA. Retrieved 2022-10-26.
  8. Pepin-Neff, Christopher; Wynter, Thomas (2017-09-13). "Shark Bites and Shark Conservation: An Analysis of Human Attitudes Following Shark Bite Incidents in Two Locations in Australia". Conservation Letters. 11 (2): e12407. doi: 10.1111/conl.12407 . ISSN   1755-263X. S2CID   90554435.

Research Sources