Squatina squatina
Encyclopedia
The angelshark is a species of shark
in the family
Squatinidae (known generally also as angel shark
s), 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 skate
s and invertebrate
s. 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
.
", in the 1758 tenth edition
of Systema Naturae
as Squalus squatina. He did not designate a type specimen. 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. Other common name
s used for this species include angel, angel fiddle fish, angel puffy fish, angel ray, angelfish, escat jueu, fiddle fish, monk, and monkfish. 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.
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 Sea
s. In recent times it has been extirpated from the North Sea
and large portions of the northern Mediterranean. 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 (492.1 ft). It sometimes enters brackish environments. Northern angelshark subpopulations migrate
northward in summer and southward in winter.
s. There are a pair of unadorned barbel
s 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.
The pectoral and pelvic fins are wide with rounded tips; the two dorsal fin
s 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. 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".
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. Aggregations numbering up to a hundred have been observed off Gran Canaria
in the summer. Known parasites of this species include the tapeworms Grillotia smaris-gora, G. angeli, and Christianella minuta, the fluke
Pseudocotyle squatinae, the monogenea
n Leptocotyle minor, and the isopod Aega rosacea.
The angelshark is an ambush predator that feeds mainly on bottom-dwelling bony fishes, especially flatfish
es, though it also preys on skate
s 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 cuttlefish
es Sepia officinalis and Sepiola
spp., and the crustacean
s Dorippe lanata, Geryon tridens, Dromia personata
, Goneplax rhomboides
, Macropipus corregatus, and Atelecyclus rotundatus. The stomachs of some examined specimens have also contained seagrass
or birds (in one case an entire cormorant
). Individual sharks select sites that offer the best ambush opportunities, and if successful may remain there for several days.
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 oocyte
s 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.
The angelshark is generally unaggressive towards humans, though it can deliver a severe bite if disturbed. 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. 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."
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. 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 goosefish
es of the genus Lophius). The angelshark may also be a source for shark liver oil
and fishmeal.
. 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.
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. 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.
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. 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. 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.
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....
in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Squatinidae (known generally also as angel shark
Angel shark
The angel sharks are an unusual genus of sharks with flattened bodies and broad pectoral fins that give them a strong resemblance to rays. The more than 16 known species are in the genus Squatina, the only genus in its family, Squatinidae, and order Squatiniformes. They occur worldwide in temperate...
s), once widespread in the coastal waters of the northeastern Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
. Well-adapted for camouflaging
Crypsis
In ecology, crypsis is the ability of an organism to avoid observation or detection by other organisms. It may be either a predation strategy or an antipredator adaptation, and methods include camouflage, nocturnality, subterranean lifestyle, transparency, and mimicry...
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
Batoidea
Batoidea is a superorder of cartilaginous fish commonly known as rays and skates, containing more than 500 described species in thirteen families...
. This species can be identified by its broad and stout body, conical barbels
Barbel (anatomy)
A barbel on a fish is a slender, whiskerlike tactile organ near the mouth. Fish that have barbels include the catfish, the carp, the goatfish, sturgeon, the zebrafish and some species of shark...
, 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
Ambush predator
Ambush predators or sit-and-wait predators are carnivorous animals that capture prey by stealth or cunning, not by speed or necessarily by strength. These organisms usually hide motionless and wait for prey to come within striking distance. They are often camouflaged, and may be solitary...
that buries itself in sediment and waits for passing prey, mostly benthic bony fishes but also skate
Skate
Skates are cartilaginous fish belonging to the family Rajidae in the superorder Batoidea of rays. There are more than 200 described species in 27 genera. There are two subfamilies, Rajinae and Arhynchobatinae ....
s and invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s. 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
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...
, this shark was often sold on European markets under the name "monkfish
Monkfish
Monkfish is the English name of a number of types of fish in the northwest Atlantic, most notably the species of the anglerfish genus Lophius and the angelshark genus Squatina...
". Since the mid-20th century, intense commercial fishing
Commercial fishing
Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often pursue fish far into the ocean under adverse conditions...
across the angelshark's range have decimated its population via bycatch
Bycatch
The term “bycatch” is usually used for fish caught unintentionally in a fishery while intending to catch other fish. It may however also indicate untargeted catch in other forms of animal harvesting or collecting...
– 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
Critically Endangered
Critically Endangered is the highest risk category assigned by the IUCN Red List for wild species. Critically Endangered means that a species' numbers have decreased, or will decrease, by 80% within three generations....
.
Taxonomy and phylogeny
The angelshark was originally described by the Swedish natural historian Carl Linnaeus, known as the "father of taxonomyTaxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
", in the 1758 tenth edition
10th edition of Systema Naturae
The 10th edition of Systema Naturae was a book written by Carl Linnaeus and published in two volumes in 1758 and 1759, which marks the starting point of zoological nomenclature...
of Systema Naturae
Systema Naturae
The book was one of the major works of the Swedish botanist, zoologist and physician Carolus Linnaeus. The first edition was published in 1735...
as Squalus squatina. He did not designate a type specimen. The word squatina is the angelshark's name in Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
, derived from the word for skate
Skate
Skates are cartilaginous fish belonging to the family Rajidae in the superorder Batoidea of rays. There are more than 200 described species in 27 genera. There are two subfamilies, Rajinae and Arhynchobatinae ....
; it was made the genus name for all angel sharks by the French zoologist André Duméril
André Marie Constant Duméril
André Marie Constant Duméril was a French zoologist. He was professor of anatomy at the Muséum National d'Histoire Naturelle from 1801 to 1812, when he became professor of herpetology and ichthyology...
in 1806. Other common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
s used for this species include angel, angel fiddle fish, angel puffy fish, angel ray, angelfish, escat jueu, fiddle fish, monk, and monkfish. Stelbrink and colleagues (2010) conducted a phylogenetic study based on mitochondrial DNA
Mitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...
, and found that the sister species of the angelshark is the sawback angelshark
Sawback angelshark
The sawback angelshark, Squatina aculeata, is an angel shark of the family Squatinidae-Identification:Colour: Are a dull grey to a light brown on back that has scarcely scattered with small irregular white spots and also with regular small dark brownish spots. No ocelli. Obtains dark blotches on...
(S. aculeata). The two species formed a clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
with a number of Asian angelshark species.
Distribution and habitat
Historically, the angelshark occurred in the temperateTemperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...
waters of the northeastern Atlantic, from southern Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
and Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
to the Western Sahara
Western Sahara
Western Sahara is a disputed territory in North Africa, bordered by Morocco to the north, Algeria to the northeast, Mauritania to the east and south, and the Atlantic Ocean to the west. Its surface area amounts to . It is one of the most sparsely populated territories in the world, mainly...
and the Canary Islands
Canary Islands
The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...
, including around the British Isles
British Isles
The British Isles are a group of islands off the northwest coast of continental Europe that include the islands of Great Britain and Ireland and over six thousand smaller isles. There are two sovereign states located on the islands: the United Kingdom of Great Britain and Northern Ireland and...
and in the Mediterranean
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
and Black Sea
Black Sea
The Black Sea is bounded by Europe, Anatolia and the Caucasus and is ultimately connected to the Atlantic Ocean via the Mediterranean and the Aegean seas and various straits. The Bosphorus strait connects it to the Sea of Marmara, and the strait of the Dardanelles connects that sea to the Aegean...
s. In recent times it has been extirpated from the North Sea
North Sea
In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...
and large portions of the northern Mediterranean. This benthic shark inhabits the continental shelf
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
, preferring soft substrates such as mud or sand, and can be found from near the coast to a depth of 150 m (492.1 ft). It sometimes enters brackish environments. Northern angelshark subpopulations migrate
Fish migration
Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousands of kilometres...
northward in summer and southward in winter.
Description
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 (176.4 lb). 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 spiracleSpiracle
Spiracles are openings on the surface of some animals that usually lead to respiratory systems.-Vertebrates:The spiracle is a small hole behind each eye that opens to the mouth in some fishes. In the primitive jawless fish the first gill opening immediately behind the mouth is essentially similar...
s. There are a pair of unadorned barbel
Barbel (anatomy)
A barbel on a fish is a slender, whiskerlike tactile organ near the mouth. Fish that have barbels include the catfish, the carp, the goatfish, sturgeon, the zebrafish and some species of shark...
s 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.
The pectoral and pelvic fins are wide with rounded tips; the two dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
s 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. 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".
Biology and ecology
Gran Canaria
Gran Canaria is the second most populous island of the Canary Islands, with a population of 838,397 which constitutes approximately 40% of the population of the archipelago...
in the summer. Known parasites of this species include the tapeworms Grillotia smaris-gora, G. angeli, and Christianella minuta, the fluke
Trematoda
Trematoda is a class within the phylum Platyhelminthes that contains two groups of parasitic flatworms, commonly referred to as "flukes".-Taxonomy and biodiversity:...
Pseudocotyle squatinae, the monogenea
Monogenea
Monogenea are a group of largely ectoparasitic members of the flatworm phylum Platyhelminthes, class Monogenea.-Characteristics:Monogenea are very small parasitic flatworms mainly found on skin or gills of fish....
n Leptocotyle minor, and the isopod Aega rosacea.
The angelshark is an ambush predator that feeds mainly on bottom-dwelling bony fishes, especially flatfish
Flatfish
The flatfish are an order of ray-finned fish, also called the Heterosomata, sometimes classified as a suborder of Perciformes. In many species, both eyes lie on one side of the head, one or the other migrating through and around the head during development...
es, though it also preys on skate
Skate
Skates are cartilaginous fish belonging to the family Rajidae in the superorder Batoidea of rays. There are more than 200 described species in 27 genera. There are two subfamilies, Rajinae and Arhynchobatinae ....
s and invertebrates. Prey reported taken include the hake
Hake
The term hake refers to fish in either of:* family Phycidae of the northern oceans* family Merlucciidae of the southern oceans-Hake fish:...
Merluccius merluccius
Merluccius merluccius
The European hake is a merluccid hake of the genus Merluccius. It sometimes was called the "herring hake", perhaps because it often feeds on herring and therefore is likely to be netted along with herring...
, the bream
Sparidae
The Sparidae is a family of fish, included in the order Perciformes. The fish of the family are commonly called sea breams and porgies . The sheepshead, scup, and red sea bream are species in this family. They are found in shallow temperate and tropical waters and are bottom-dwelling carnivores....
Pagellus erythrinus
Pagellus erythrinus
Pagellus erythrinus, or the common pandora, is a fish of the Sparidae family . It is a popular food fish in Mediterranean countries, with delicate white flesh....
, grunts
Haemulidae
The grunts are a family, Haemulidae, of fishes in the order Perciformes. They are numerous and widespread, with about 150 species in 19 genera, found in tropical fresh, brackish and salt waters around the world...
in the genus Pomadasys, the flatfishes Bothus
Bothus
Bothus is a genus of flatfish in the family Bothidae .-Species:* Bothus assimilis * Bothus bleekeri Steindachner, 1861* Bothus constellatus...
spp., Citharus linguatula, and Solea solea, the squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
Loligo vulgaris
Loligo vulgaris
The European squid is a large squid belonging to the family Loliginidae. It occurs abundantly in coastal waters from the North Sea to at least the west coast of Africa. This species lives from sea level to depths of . Its mantle is up to long...
, the cuttlefish
Cuttlefish
Cuttlefish are marine animals of the order Sepiida. They belong to the class Cephalopoda . Despite their name, cuttlefish are not fish but molluscs....
es Sepia officinalis and Sepiola
Sepiola
Sepiola is a genus of bobtail squid comprising around 15 species.-Species:*Genus Sepiola**Sepiola affinis, Anagolous Bobtail**Sepiola atlantica, Atlantic Bobtail**Sepiola aurantiaca, Golden Bobtail...
spp., and the crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s Dorippe lanata, Geryon tridens, Dromia personata
Dromia personata
Dromia personata is a species of crab found in the North Sea, the Mediterranean Sea, and connecting parts of the northeastern Atlantic Ocean. It grows up to a carapace length of , and lives mainly from the lower shore to a depth of , or occasionally to , and often in caves...
, Goneplax rhomboides
Goneplax rhomboides
Goneplax rhomboides is a species of crab. It is known by the common name angular crab because of its angular carapace. Although it is also called the square crab, its shell is in fact more trapezoidal than square...
, Macropipus corregatus, and Atelecyclus rotundatus. The stomachs of some examined specimens have also contained seagrass
Seagrass
Seagrasses are flowering plants from one of four plant families , all in the order Alismatales , which grow in marine, fully saline environments.-Ecology:...
or birds (in one case an entire cormorant
Cormorant
The bird family Phalacrocoracidae is represented by some 40 species of cormorants and shags. Several different classifications of the family have been proposed recently, and the number of genera is disputed.- Names :...
). Individual sharks select sites that offer the best ambush opportunities, and if successful may remain there for several days.
Angelsharks are aplacental viviparous, meaning the young hatch inside the mother's uterus
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
and are nourished by a yolk sac
Yolk sac
The yolk sac is a membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals...
until birth. Females have two functional ovaries
Ovary
The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands.-Human anatomy:Ovaries...
, with the right ovary containing more oocyte
Oocyte
An oocyte, ovocyte, or rarely ocyte, is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in the ovary during female gametogenesis. The female germ cells produce a primordial germ cell which undergoes a mitotic...
s 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
Vitellogenesis
Vitellogenesis is the process of yolk formation via nutrients being deposited in the oocyte, or female germ cell involved in reproduction. It starts when the fat body stimulates the release of juvenile hormones and produces vitellogenin protein. It occurs in all animal groups lower than the mammals...
(yolk formation) occurs concurrently with pregnancy, in the angelshark the onset of vitellogenesis is delayed until halfway through the gestation period
Gestation period
For mammals the gestation period is the time in which a fetus develops, beginning with fertilization and ending at birth. The duration of this period varies between species.-Duration:...
. 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
Ovulation
Ovulation is the process in a female's menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum . Ovulation also occurs in the estrous cycle of other female mammals, which differs in many fundamental ways from the menstrual cycle...
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.
Human interactions
Humans have utilized the angelshark for thousands of years. Ancient Greek
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...
authors, such as Diphilus and Mnesitheus, described its meat as "light" and "easily digestible", and Pliny the Elder
Pliny the Elder
Gaius Plinius Secundus , better known as Pliny the Elder, was a Roman author, naturalist, and natural philosopher, as well as naval and army commander of the early Roman Empire, and personal friend of the emperor Vespasian...
noted in his Naturalis Historia (77–79 AD) that its rough skin was valued by craftsmen for polishing wood
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...
and ivory
Ivory
Ivory is a term for dentine, which constitutes the bulk of the teeth and tusks of animals, when used as a material for art or manufacturing. Ivory has been important since ancient times for making a range of items, from ivory carvings to false teeth, fans, dominoes, joint tubes, piano keys and...
. Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...
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. 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 goosefish
Goosefish
Monkfish are a family, Lophiidae, of anglerfishes. They are found in the Arctic, Atlantic, Indian and Pacific Oceans where they live on sandy and muddy bottoms of the continental shelf and continental slope, at depths in excess of ....
es of the genus Lophius). The angelshark may also be a source for shark liver oil
Shark liver oil
Shark liver oil is obtained from sharks that are caught for food purposes and are living in cold, deep oceans. The liver oil from sharks has been used by fishermen for centuries as a folk remedy for general health...
and fishmeal.
Conservation status
Sources from the 19th and early 20th centuries indicate that the angelshark was once abundant all around the coasts of Western EuropeWestern Europe
Western Europe is a loose term for the collection of countries in the western most region of the European continents, though this definition is context-dependent and carries cultural and political connotations. One definition describes Western Europe as a geographic entity—the region lying in the...
. 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
Iberian Peninsula
The Iberian Peninsula , sometimes called Iberia, is located in the extreme southwest of Europe and includes the modern-day sovereign states of Spain, Portugal and Andorra, as well as the British Overseas Territory of Gibraltar...
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.
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. Healthy subpopulations of angelsharks are thought to still persist in areas off North Africa
North Africa
North Africa or Northern Africa is the northernmost region of the African continent, linked by the Sahara to Sub-Saharan Africa. Geopolitically, the United Nations definition of Northern Africa includes eight countries or territories; Algeria, Egypt, Libya, Morocco, South Sudan, Sudan, Tunisia, and...
and around the Canary Islands, though a more thorough assessment is urgently needed.
As a result of these steep population declines and the ongoing threat from demersal
Demersal zone
The demersal zone is the part of the sea or ocean comprising the water column that is near to the seabed and the benthos. The demersal zone is just above the benthic zone and forms a layer of the larger profundal zone....
fisheries, the IUCN has assessed the angelshark as Critically Endangered
Critically Endangered
Critically Endangered is the highest risk category assigned by the IUCN Red List for wild species. Critically Endangered means that a species' numbers have decreased, or will decrease, by 80% within three generations....
. It is listed on Annex III of the 1976 Barcelona Convention
Barcelona Convention
The 1976 Barcelona Convention for Protection against Pollution in the Mediterranean Sea is a regional convention to prevent and abate pollution from ships, aircraft and land based sources in the Mediterranean Sea. This includes, but is not limited to, dumping, run-off and discharges...
, which aims to limit pollution
Pollution
Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...
in the Mediterranean Sea. This species is protected within three marine reserves in the Balearic Islands
Balearic Islands
The Balearic Islands are an archipelago of Spain in the western Mediterranean Sea, near the eastern coast of the Iberian Peninsula.The four largest islands are: Majorca, Minorca, Ibiza and Formentera. The archipelago forms an autonomous community and a province of Spain with Palma as the capital...
, although it has not been reported from this area since the mid-1990s. In 2008, the angelshark also received full legal protection from human activities in the waters off England and Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
from the coast to a distance of 11 km (6.8 mi), under the UK Wildlife and Countryside Act. The United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
and Belgium
Belgium
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...
have pushed, unsuccessfully, for this species to be listed on the Convention for the Protection of the Marine Environment of the North-East Atlantic
Convention for the Protection of the Marine Environment of the North-East Atlantic
The or OSPAR Convention is the current legislative instrument regulating international cooperation on environmental protection in the North-East Atlantic. It combines and up-dates the 1972 Oslo Convention on dumping waste at sea and the 1974 Paris Convention on land-based sources of marine pollution...
(OSPAR) Priority List of Threatened and Endangered Species.