Blackmouth catshark
Encyclopedia
The blackmouth catshark (Galeus melastomus) is a species
of catshark
, family
Scyliorhinidae, common in the northeastern Atlantic Ocean
from Iceland
to Senegal
, including the Mediterranean Sea
. It is typically found over the continental slope at depths of 150–1400 m (492.1–4,593.2 ft), on or near muddy bottoms. The youngest sharks generally inhabit shallower water than the older juveniles and adults. This slim-bodied species is characterized by the black interior of its mouth, a marbled pattern of pale-edged brownish saddles or blotches along its back and tail, and a prominent saw-toothed crest of enlarged dermal denticles along the upper edge of its caudal fin. It reaches lengths of 50–79 cm (19.7–31.1 in), with sharks in the Atlantic growing larger than those in the Mediterranean.
Slow-swimming but active, the blackmouth catshark is a generalist
that preys on a wide variety of crustacean
s, cephalopod
s, and fish
es. Its visual and electroreceptive
systems are adept at tracking moving, bioluminescent
prey. This species is oviparous, with females producing batches of up to 13 egg cases throughout the year. Because of its abundance, the blackmouth catshark forms a substantial part of the bycatch
of deepwater commercial fisheries across much of its range. It has low economic value and is usually discarded, though the largest sharks may be marketed for meat and leather
. The International Union for Conservation of Nature (IUCN) has listed this species under Least Concern
, as there is no indication that its numbers have declined despite fishing pressure.
species, based on mitochondrial
and nuclear DNA
, found that G. melastomus forms a clade
with G. murinus
, apart from the clade of G. eastmani
, G. gracilis
, and G. sauteri
. The oldest documented blackmouth catshark fossil
s come from the northern Apennines and date to the Lower Pliocene (5.3–3.6 Ma).
and Trondheim
, Norway
southward to Senegal
, including the Faroe Islands
, the British Isles
, the Azores
, and the northern portion of the Mid-Atlantic Ridge
. It occurs throughout the Mediterranean Sea
, save for the northern waters of the Adriatic
and Aegean Sea
s, and is absent from the Black Sea
. This species primarily inhabits the continental slope, at depths of 150–1400 m (492.1–4,593.2 ft). However, it has been documented from water as shallow as 50–60 m (164–196.9 ft) off southern France, and as deep as 2300–3850 m (7,545.9–12,631.2 ft) in the eastern Mediterranean. The depths at which it is most common vary between regions, for example 300–500 m (984.3–1,640.4 ft) in the Bay of Biscay
, 400–800 m (1,312.3–2,624.7 ft) off Portugal
, 500–800 m (1,640.4–2,624.7 ft) in the Strait of Sicily
, 1000–1400 m (3,280.8–4,593.2 ft) in the Catalan Sea
, and 1500–1830 m (4,921.3–6,003.9 ft) in the eastern Mediterranean. Water temperature does not appear to be an important factor in determining the distribution of this species.
Found on or near the bottom, the blackmouth catshark favors a muddy habitat
. There is little evidence for segregation by sex. A number of studies in the northern and western Mediterranean have reported that adults occur deeper than juveniles. Other studies though have found no such pattern. It is possible that areas such as the waters off southern France offer a habitat suitable for sharks of all ages. Another explanation with some scientific support is that adults are most common at intermediate depths, while young sharks are restricted to shallower water and both adults and juveniles are found in deeper water. If true, the age-depth inconsistencies observed from previous research could have resulted from incomplete depth sampling
.
The reported maximum lengths attained by the blackmouth catshark varies from 67 to 79 cm (26.4 to 31.1 in) for Atlantic sharks and 50 to 64 cm (19.7 to 25.2 in) for Mediterranean sharks; a length record of 90 cm (35.4 in) may be dubious. Females attain a larger ultimate size than males. The maximum weight on record is 1.4 kg (3.1 lb). This species has a slender, firm body with a rather long, pointed snout comprising roughly 6–9% of the total length. The anterior rim of each nostril bears a large triangular flap, which divides the nostril into incurrent and excurrent openings. The eyes are horizontally oval and equipped with rudimentary nictitating membrane
s (protective third eyelids). Beneath each eye is a subtle ridge, and behind is a small spiracle
. The mouth forms a short, wide arch, and bears moderately long furrows around the corners. The upper and lower jaws contain around 69 and 79 tooth rows respectively. Each tooth is small, with a narrow central cusp
flanked by one or two smaller cusplets on either side. There are five pairs of gill slit
s, with the fifth pair over the pectoral fin bases.
The two dorsal fin
s are roughly equal in size and placed far back on the body: the first originates behind the midpoint of the pelvic fin bases and the second behind the midpoint of the anal fin base. The pectoral fins are large, while the pelvic fins are small and low, with angular margins. The anal fin is much larger than either dorsal fin; its base measures 13–18% of the total length and greatly exceeds the distance between the pelvic and anal fins, or between the dorsal fins. The caudal peduncle is laterally compressed, with the end of the anal fin very close to the caudal fin. The caudal fin comprises around a quarter of the total length; the upper lobe is low with a ventral notch near the tip, while the lower lobe is indistinct. The skin is very thick and covered by well-calcified
dermal denticles. There is a prominent row of enlarged denticles, resembling saw teeth, along the upper edge of the caudal fin. The body is grayish-brown above, with 15–18 dark, rounded saddles, blotches, and/or spots that run onto the tail; each marking is highlighted by a paler border. The underside is white, as are the tips of the dorsal and caudal fins. The inside of the mouth is black.
. Relatively slow, this shark swims with strong eel-like (anguilliform) undulations of its body. It often cruises just above the sea floor, perhaps taking advantage of the ground effect (a reduction in the drag
on a wing when close to the ground) to save energy. It has also been seen resting motionless on the bottom. Known predators of the blackmouth catshark include the kitefin shark
(Dalatias licha) and the European flying squid (Todarodes sagittatus). Parasites that have been documented from this species include the tapeworm Ditrachybothridium macrocephalum and the protist
Eimeria palavensis.
predator that feeds on both bottom-dwelling and free-swimming organisms. Its diet is dominated by decapod
s, krill
, bony fishes (including lanternfish
es, bristlemouths, dragonfish
es, and mora
s), and cephalopod
s. The most significant prey species generally reflect what is most available in the environment, for example the shrimp
s Calocaris macandreae and Pasiphaea multidentata off southern France and the prawn
s Sergestes arcticus and Sergia robusta off the Iberian Peninsula
. Juveniles consume a greater amount and variety of crustaceans than adults, including smaller types such as mysid
s and hyperiid amphipod
s. Adults favor relatively large fish prey and have been known to take other sharks and rays and smaller members of the same species. The importance of cephalopod prey across ages differs between regions. The stomachs of some blackmouth catsharks have found to contain pieces of animals too large for a single shark to overwhelm, suggesting that it may sometimes attack in groups. Scavenging has been infrequently documented, including of human refuse.
When foraging, the blackmouth catshark swings its head from side to side to employ its senses more effectively. It likely relies mainly on vision and electroreception
to find food, and less on smell
. As in most sharks, its visual acuity
is greatest along the median horizontal plane. The lens
and cone cell
s of its eyes are large, allowing smaller or farther objects to be discerned from the background. The rod cell
s of its eyes are most sensitive to the wavelengths emitted by bioluminescence
, which is exhibited by most of the organisms it hunts. For electroreception, the blackmouth catshark has a high number of ampullae of Lorenzini
that are evenly arranged, which enhances spatial resolution and is best suited for localizing fast-moving prey.
, in which more than one egg can mature within each oviduct
simultaneously. Females may contain up to 13 developing eggs, though 1–4 per oviduct is typical. The number of eggs laid annually per female has been estimated at between 60 to 100, increasing with female size. Only the right ovary
is functional in mature females. The egg case is vase-shaped and bears a slight flange along the lateral margins; the anterior end is squared off, with a pair of stubby, coiled horns at the corners, while the posterior end is rounded. The surface of the case is somewhat translucent, smooth, and glossy. The case is a golden brown color when first laid, and becomes dark brown in sea water. Egg cases produced by Atlantic sharks measure 3.5–6.5 cm (1.4–2.6 in) long and 1.4–3 cm (0.551181102362205–1.2 in) across. Those produced by Mediterranean sharks tend to be smaller at 4.2–5.5 cm (1.7–2.2 in) long and 1.7–2.5 cm (0.669291338582677–0.984251968503937 in) across. Larger females produce slightly larger egg cases.
Mating
and egg-laying proceeds year-round; reproductive activity is highest in winter and summer, though not all studies have found such a seasonal pattern. The eggs are deposited on muddy substrates
in relatively shallow water. Maturation size
varies between geographical regions, and is generally larger in the Atlantic than in the Mediterranean. Lengths at maturity for males and females have been variously reported from 48 to 79 cm (18.9 to 31.1 in) and 56 to 79 cm (22 to 31.1 in) respectively in the Atlantic, and from 42 to 55 cm (16.5 to 21.7 in) and 39 to 61 cm (15.4 to 24 in) respectively in the Mediterranean.
in large numbers by commercial
bottom trawl and longline fisheries. In particular, it is among the most commonly bycaught sharks in trawls targeting deepwater lobsters and shrimps (Nephrops norvegicus, Parapenaeus longirostris, Aristeus antennatus, and Aristaeomorpha folicea), operating off Portugal and in the Mediterranean. Most captured sharks are discarded, probably with heavy mortality. Some fisheries, such as those off Portugal and Italy, retain and utilize a small subset of the largest individuals for human consumption fresh or dried and salted, and for leather
; the fishing fleet of Viareggio
, Tuscany
reported landing 700 kg (1,543.2 lb) in 2005. In the northeastern Atlantic, this shark is being increasingly targeted by fishers following the decline of other deepwater shark species.
Off Corsica
, Sicily
, and southern Portugal, and in the Ionian
, southern Adriatic, and Aegean Seas, most of the blackmouth catsharks captured are immature, suggesting there has been a negative impact of fishing pressure. However, the species remains extremely abundant in a number of areas, and survey and fishery data have not shown any evidence of overall population decline. The wide range of depths it occupies likely afford it some protection against fishing, particularly given a 2005 ban on trawling deeper than 1000 m (3,280.8 ft) in the Mediterranean. Therefore, the International Union for Conservation of Nature (IUCN) has listed the blackmouth catshark under Least Concern
. In the waters of the European Commission
, fishing for this species is managed as part of the Total Allowable Catch (TAC) for deepwater sharks.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of catshark
Catshark
Catsharks are ground sharks of the family Scyliorhinidae, with over 150 known species. While they are generally known as catsharks, many species are commonly called dogfish....
, 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...
Scyliorhinidae, common in 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...
from Iceland
Iceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
to Senegal
Senegal
Senegal , officially the Republic of Senegal , is a country in western Africa. It owes its name to the Sénégal River that borders it to the east and north...
, including the Mediterranean Sea
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...
. It is typically found over the continental slope at depths of 150–1400 m (492.1–4,593.2 ft), on or near muddy bottoms. The youngest sharks generally inhabit shallower water than the older juveniles and adults. This slim-bodied species is characterized by the black interior of its mouth, a marbled pattern of pale-edged brownish saddles or blotches along its back and tail, and a prominent saw-toothed crest of enlarged dermal denticles along the upper edge of its caudal fin. It reaches lengths of 50–79 cm (19.7–31.1 in), with sharks in the Atlantic growing larger than those in the Mediterranean.
Slow-swimming but active, the blackmouth catshark is a generalist
Generalist and specialist species
A generalist species is able to thrive in a wide variety of environmental conditions and can make use of a variety of different resources . A specialist species can only thrive in a narrow range of environmental conditions or has a limited diet. Most organisms do not all fit neatly into either...
that preys on a wide variety of 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, cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...
s, and fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
es. Its visual and electroreceptive
Electroreception
Electroreception is the biological ability to perceive natural electrical stimuli. It has been observed only in aquatic or amphibious animals, since water is a much better conductor than air. Electroreception is used in electrolocation and for electrocommunication.- Overview :Electroreception is...
systems are adept at tracking moving, bioluminescent
Bioluminescence
Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...
prey. This species is oviparous, with females producing batches of up to 13 egg cases throughout the year. Because of its abundance, the blackmouth catshark forms a substantial part of the 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...
of deepwater commercial fisheries across much of its range. It has low economic value and is usually discarded, though the largest sharks may be marketed for meat and leather
Leather
Leather is a durable and flexible material created via the tanning of putrescible animal rawhide and skin, primarily cattlehide. It can be produced through different manufacturing processes, ranging from cottage industry to heavy industry.-Forms:...
. The International Union for Conservation of Nature (IUCN) has listed this species under Least Concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...
, as there is no indication that its numbers have declined despite fishing pressure.
Taxonomy and phylogeny
Constantine Samuel Rafinesque briefly described the blackmouth catshark in his 1810 Caratteri di alcuni nuovi generi e nuove specie di animali e piante della Sicilia: con varie osservazioni sopra i medesimi, wherein he referenced the distinctive black interior of its mouth (from which the specific epithet melastomus is derived). No type specimen was designated. This species may also be called the black-mouthed dogfish. A 2005 phylogenetic analysis that included five GaleusGaleus
Galeus is a genus of catshark, family Scyliorhinidae, commonly known as sawtail catsharks in reference to a distinctive saw-toothed crest of enlarged dermal denticles found along the upper edges of their caudal fins. They are found in the Atlantic, the western and central Pacific, and the Gulf of...
species, based on mitochondrial
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 nuclear DNA
Nuclear DNA
Nuclear DNA, nuclear deoxyribonucleic acid , is DNA contained within a nucleus of eukaryotic organisms. In mammals and vertebrates, nuclear DNA encodes more of the genome than the mitochondrial DNA and is composed of information inherited from two parents, one male, and one female, rather than...
, found that G. melastomus forms 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 G. murinus
Mouse catshark
The mouse catshark is a species of catshark, family Scyliorhinidae, common in the northeastern Atlantic Ocean, from Iceland to Western Sahara. There is much taxonomic confusion regarding this species in Icelandic waters, where it may be confounded with another species of Galeus or Apristurus...
, apart from the clade of G. eastmani
Gecko catshark
The gecko catshark is a species of catshark, 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 . Its body is slender, with a pattern of dark saddles and blotches...
, G. gracilis
Slender sawtail catshark
The slender sawtail catshark is a little-known species of catshark, family Scyliorhinidae, endemic to northern Australia. It is found over the continental slope in on water...
, and G. sauteri
Blacktip sawtail catshark
The blacktip sawtail catshark is a species of catshark, family Scyliorhinidae, found off Taiwan and the Philippines. It is demersal in nature and occurs deeper than...
. The oldest documented blackmouth catshark fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s come from the northern Apennines and date to the Lower Pliocene (5.3–3.6 Ma).
Distribution and habitat
The blackmouth catshark is widely distributed in the northeastern Atlantic Ocean, from southwestern IcelandIceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
and Trondheim
Trondheim
Trondheim , historically, Nidaros and Trondhjem, is a city and municipality in Sør-Trøndelag county, Norway. With a population of 173,486, it is the third most populous municipality and city in the country, although the fourth largest metropolitan area. It is the administrative centre of...
, 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...
southward to Senegal
Senegal
Senegal , officially the Republic of Senegal , is a country in western Africa. It owes its name to the Sénégal River that borders it to the east and north...
, including the Faroe Islands
Faroe Islands
The Faroe Islands are an island group situated between the Norwegian Sea and the North Atlantic Ocean, approximately halfway between Scotland and Iceland. The Faroe Islands are a self-governing territory within the Kingdom of Denmark, along with Denmark proper and Greenland...
, 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...
, the Azores
Azores
The Archipelago of the Azores is composed of nine volcanic islands situated in the middle of the North Atlantic Ocean, and is located about west from Lisbon and about east from the east coast of North America. The islands, and their economic exclusion zone, form the Autonomous Region of the...
, and the northern portion of the Mid-Atlantic Ridge
Mid-Atlantic Ridge
The Mid-Atlantic Ridge is a mid-ocean ridge, a divergent tectonic plate boundary located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. It separates the Eurasian Plate and North American Plate in the North Atlantic, and the African Plate from the South...
. It occurs throughout the Mediterranean Sea
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...
, save for the northern waters of the Adriatic
Adriatic Sea
The Adriatic Sea is a body of water separating the Italian Peninsula from the Balkan peninsula, and the system of the Apennine Mountains from that of the Dinaric Alps and adjacent ranges...
and Aegean Sea
Aegean Sea
The Aegean Sea[p] is an elongated embayment of the Mediterranean Sea located between the southern Balkan and Anatolian peninsulas, i.e., between the mainlands of Greece and Turkey. In the north, it is connected to the Marmara Sea and Black Sea by the Dardanelles and Bosporus...
s, and is absent from the 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...
. This species primarily inhabits the continental slope, at depths of 150–1400 m (492.1–4,593.2 ft). However, it has been documented from water as shallow as 50–60 m (164–196.9 ft) off southern France, and as deep as 2300–3850 m (7,545.9–12,631.2 ft) in the eastern Mediterranean. The depths at which it is most common vary between regions, for example 300–500 m (984.3–1,640.4 ft) in the Bay of Biscay
Bay of Biscay
The Bay of Biscay is a gulf of the northeast Atlantic Ocean located south of the Celtic Sea. It lies along the western coast of France from Brest south to the Spanish border, and the northern coast of Spain west to Cape Ortegal, and is named in English after the province of Biscay, in the Spanish...
, 400–800 m (1,312.3–2,624.7 ft) off Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...
, 500–800 m (1,640.4–2,624.7 ft) in the Strait of Sicily
Strait of Sicily
The Strait of Sicily is the strait between Sicily and Tunisia. It is about wide and divides the Tyrrhenian Sea and the western Mediterranean Sea from the eastern Mediterranean. Its maximum depth is ....
, 1000–1400 m (3,280.8–4,593.2 ft) in the Catalan Sea
Balearic Sea
The Balearic Sea or Iberian Sea is a body of water in the Mediterranean Sea near the Balearic Islands. In the Catalan language the area is also known as the Catalan-Balearic Sea .The Ebro River flows into this small sea....
, and 1500–1830 m (4,921.3–6,003.9 ft) in the eastern Mediterranean. Water temperature does not appear to be an important factor in determining the distribution of this species.
Found on or near the bottom, the blackmouth catshark favors a muddy habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
. There is little evidence for segregation by sex. A number of studies in the northern and western Mediterranean have reported that adults occur deeper than juveniles. Other studies though have found no such pattern. It is possible that areas such as the waters off southern France offer a habitat suitable for sharks of all ages. Another explanation with some scientific support is that adults are most common at intermediate depths, while young sharks are restricted to shallower water and both adults and juveniles are found in deeper water. If true, the age-depth inconsistencies observed from previous research could have resulted from incomplete depth sampling
Sampling (statistics)
In statistics and survey methodology, sampling is concerned with the selection of a subset of individuals from within a population to estimate characteristics of the whole population....
.
Description
Nictitating membrane
The nictitating membrane is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten it while maintaining visibility. Some reptiles, birds, and sharks have a full nictitating membrane; in many mammals, there is a small...
s (protective third eyelids). Beneath each eye is a subtle ridge, and behind is a small spiracle
Spiracle
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...
. The mouth forms a short, wide arch, and bears moderately long furrows around the corners. The upper and lower jaws contain around 69 and 79 tooth rows respectively. Each tooth is small, with a narrow central cusp
Cusp (dentistry)
A cusp is an occlusal or incisal eminence on a tooth.Canine teeth, otherwise known as cuspids, each possess a single cusp, while premolars, otherwise known as bicuspids, possess two each. Molars normally possess either four or five cusps...
flanked by one or two smaller cusplets on either side. There are five pairs of gill slit
Gill slit
Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of Cartilaginous fish such as sharks, rays, sawfish, and guitarfish. Most of these have five pairs, but a few species have 6 or 7 pairs...
s, with the fifth pair over the pectoral fin bases.
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 roughly equal in size and placed far back on the body: the first originates behind the midpoint of the pelvic fin bases and the second behind the midpoint of the anal fin base. The pectoral fins are large, while the pelvic fins are small and low, with angular margins. The anal fin is much larger than either dorsal fin; its base measures 13–18% of the total length and greatly exceeds the distance between the pelvic and anal fins, or between the dorsal fins. The caudal peduncle is laterally compressed, with the end of the anal fin very close to the caudal fin. The caudal fin comprises around a quarter of the total length; the upper lobe is low with a ventral notch near the tip, while the lower lobe is indistinct. The skin is very thick and covered by well-calcified
Calcification
Calcification is the process in which calcium salts build up in soft tissue, causing it to harden. Calcifications may be classified on whether there is mineral balance or not, and the location of the calcification.-Causes:...
dermal denticles. There is a prominent row of enlarged denticles, resembling saw teeth, along the upper edge of the caudal fin. The body is grayish-brown above, with 15–18 dark, rounded saddles, blotches, and/or spots that run onto the tail; each marking is highlighted by a paler border. The underside is white, as are the tips of the dorsal and caudal fins. The inside of the mouth is black.
Biology and ecology
Within its range, the blackmouth catshark is one of the most abundant sharks over the upper and middle continental slope. It is nomadic in nature and may be found alone or in groupsShoaling and schooling
In biology, any group of fish that stay together for social reasons are said to be shoaling , and if, in addition, the group is swimming in the same direction in a coordinated manner, they are said to be schooling . In common usage, the terms are sometimes used rather loosely...
. Relatively slow, this shark swims with strong eel-like (anguilliform) undulations of its body. It often cruises just above the sea floor, perhaps taking advantage of the ground effect (a reduction in the drag
Drag (physics)
In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...
on a wing when close to the ground) to save energy. It has also been seen resting motionless on the bottom. Known predators of the blackmouth catshark include the kitefin shark
Kitefin shark
The kitefin shark or seal shark is a species of dogfish shark in the family Dalatiidae, and the only species in its genus. It is found sporadically around the world, usually close to the sea floor at depths of . With a sizable oil-filled liver to maintain neutral buoyancy, this shark is able to...
(Dalatias licha) and the European flying squid (Todarodes sagittatus). Parasites that have been documented from this species include the tapeworm Ditrachybothridium macrocephalum and the protist
Protist
Protists are a diverse group of eukaryotic microorganisms. Historically, protists were treated as the kingdom Protista, which includes mostly unicellular organisms that do not fit into the other kingdoms, but this group is contested in modern taxonomy...
Eimeria palavensis.
Feeding
The blackmouth catshark is an active, generalistGeneralist and specialist species
A generalist species is able to thrive in a wide variety of environmental conditions and can make use of a variety of different resources . A specialist species can only thrive in a narrow range of environmental conditions or has a limited diet. Most organisms do not all fit neatly into either...
predator that feeds on both bottom-dwelling and free-swimming organisms. Its diet is dominated by decapod
Decapoda
The decapods or Decapoda are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crayfish, crabs, lobsters, prawns and shrimp. Most decapods are scavengers. It is estimated that the order contains nearly 15,000 species in around 2,700 genera, with...
s, krill
Krill
Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world...
, bony fishes (including lanternfish
Lanternfish
Cooper Lanternfishes are small mesopelagic fish of the large family Myctophidae. One of two families in the order Myctophiformes, the Myctophidae are represented by 246 species in 33 genera, and are found in oceans worldwide. They are aptly named after their conspicuous use of bioluminescence...
es, bristlemouths, dragonfish
Stomiidae
Stomiidae is a family of deep-sea ray-finned fish, including the barbeled dragonfishes, stareaters and loosejaws.Stomiids are generally elongated fish with black or near-black bodies, but they are highly variable in form, and are sometimes grouped into multiple different families as a result. The...
es, and mora
Common mora
The common mora, Mora moro, is a deep-sea fish, the only species in the genus Mora. It is found worldwide in temperate seas, at depths of between 300 and 2,500 m. Its length is up to about 80 cm...
s), and cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...
s. The most significant prey species generally reflect what is most available in the environment, for example the shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
s Calocaris macandreae and Pasiphaea multidentata off southern France and the prawn
Prawn
Prawns are decapod crustaceans of the sub-order Dendrobranchiata. There are 540 extant species, in seven families, and a fossil record extending back to the Devonian...
s Sergestes arcticus and Sergia robusta off 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...
. Juveniles consume a greater amount and variety of crustaceans than adults, including smaller types such as mysid
Mysidacea
Mysida is a group of small, shrimp-like crustaceans, an order in the malacostracan superorder Peracarida. Their common name opossum shrimps stems from the presence of a brood pouch, or marsupium, in females. Mysids are mostly found in marine waters throughout the world, but are also important in...
s and hyperiid amphipod
Hyperiidae
Hyperiidae is a family of amphipods, containing the following genera:*Euthemisto Bovallius, 1887*Hyperia Latreille in Desmarest, 1823*Hyperiella Bovallius, 1887*Hyperoche Bovallius, 1887*Laxohyperia M. Vinogradov & Volkov, 1982...
s. Adults favor relatively large fish prey and have been known to take other sharks and rays and smaller members of the same species. The importance of cephalopod prey across ages differs between regions. The stomachs of some blackmouth catsharks have found to contain pieces of animals too large for a single shark to overwhelm, suggesting that it may sometimes attack in groups. Scavenging has been infrequently documented, including of human refuse.
When foraging, the blackmouth catshark swings its head from side to side to employ its senses more effectively. It likely relies mainly on vision and electroreception
Electroreception
Electroreception is the biological ability to perceive natural electrical stimuli. It has been observed only in aquatic or amphibious animals, since water is a much better conductor than air. Electroreception is used in electrolocation and for electrocommunication.- Overview :Electroreception is...
to find food, and less on smell
Olfaction
Olfaction is the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and, by analogy, sensory cells of the antennae of invertebrates...
. As in most sharks, its visual acuity
Visual acuity
Visual acuity is acuteness or clearness of vision, which is dependent on the sharpness of the retinal focus within the eye and the sensitivity of the interpretative faculty of the brain....
is greatest along the median horizontal plane. The lens
Lens (anatomy)
The crystalline lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a...
and cone cell
Cone cell
Cone cells, or cones, are photoreceptor cells in the retina of the eye that are responsible for color vision; they function best in relatively bright light, as opposed to rod cells that work better in dim light. If the retina is exposed to an intense visual stimulus, a negative afterimage will be...
s of its eyes are large, allowing smaller or farther objects to be discerned from the background. The rod cell
Rod cell
Rod cells, or rods, are photoreceptor cells in the retina of the eye that can function in less intense light than can the other type of visual photoreceptor, cone cells. Named for their cylindrical shape, rods are concentrated at the outer edges of the retina and are used in peripheral vision. On...
s of its eyes are most sensitive to the wavelengths emitted by bioluminescence
Bioluminescence
Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...
, which is exhibited by most of the organisms it hunts. For electroreception, the blackmouth catshark has a high number of ampullae of Lorenzini
Ampullae of Lorenzini
The ampullae of Lorenzini are special sensing organs called electroreceptors, forming a network of jelly-filled pores. They are mostly discussed as being found in cartilaginous fishes ; however, they are also reported to be found in Chondrostei such as Reedfish and sturgeon. Lungfish have also been...
that are evenly arranged, which enhances spatial resolution and is best suited for localizing fast-moving prey.
Life history
Unlike most members of its genus, the blackmouth catshark exhibits multiple oviparityOviparity
Oviparous animals are animals that lay eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, reptiles, all birds, the monotremes, and most insects, some molluscs and arachnids....
, in which more than one egg can mature within each oviduct
Oviduct
In non-mammalian vertebrates, the passageway from the ovaries to the outside of the body is known as the oviduct. The eggs travel along the oviduct. These eggs will either be fertilized by sperm to become a zygote, or will degenerate in the body...
simultaneously. Females may contain up to 13 developing eggs, though 1–4 per oviduct is typical. The number of eggs laid annually per female has been estimated at between 60 to 100, increasing with female size. Only the right ovary
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...
is functional in mature females. The egg case is vase-shaped and bears a slight flange along the lateral margins; the anterior end is squared off, with a pair of stubby, coiled horns at the corners, while the posterior end is rounded. The surface of the case is somewhat translucent, smooth, and glossy. The case is a golden brown color when first laid, and becomes dark brown in sea water. Egg cases produced by Atlantic sharks measure 3.5–6.5 cm (1.4–2.6 in) long and 1.4–3 cm (0.551181102362205–1.2 in) across. Those produced by Mediterranean sharks tend to be smaller at 4.2–5.5 cm (1.7–2.2 in) long and 1.7–2.5 cm (0.669291338582677–0.984251968503937 in) across. Larger females produce slightly larger egg cases.
Mating
Mating
In biology, mating is the pairing of opposite-sex or hermaphroditic organisms for copulation. In social animals, it also includes the raising of their offspring. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization...
and egg-laying proceeds year-round; reproductive activity is highest in winter and summer, though not all studies have found such a seasonal pattern. The eggs are deposited on muddy substrates
Substrate (marine biology)
Stream substrate is the material that rests at the bottom of a stream. There are several classification guides. One is:*Mud – silt and clay.*Sand – Particles between 0.06 and 2 mm in diameter.*Granule – Between 2 and 4 mm in diameter....
in relatively shallow water. Maturation size
Sexual maturity
Sexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...
varies between geographical regions, and is generally larger in the Atlantic than in the Mediterranean. Lengths at maturity for males and females have been variously reported from 48 to 79 cm (18.9 to 31.1 in) and 56 to 79 cm (22 to 31.1 in) respectively in the Atlantic, and from 42 to 55 cm (16.5 to 21.7 in) and 39 to 61 cm (15.4 to 24 in) respectively in the Mediterranean.
Human interactions
Harmless to humans and of little economic value, the blackmouth catshark is caught incidentallyBycatch
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...
in large numbers by commercial
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...
bottom trawl and longline fisheries. In particular, it is among the most commonly bycaught sharks in trawls targeting deepwater lobsters and shrimps (Nephrops norvegicus, Parapenaeus longirostris, Aristeus antennatus, and Aristaeomorpha folicea), operating off Portugal and in the Mediterranean. Most captured sharks are discarded, probably with heavy mortality. Some fisheries, such as those off Portugal and Italy, retain and utilize a small subset of the largest individuals for human consumption fresh or dried and salted, and for leather
Leather
Leather is a durable and flexible material created via the tanning of putrescible animal rawhide and skin, primarily cattlehide. It can be produced through different manufacturing processes, ranging from cottage industry to heavy industry.-Forms:...
; the fishing fleet of Viareggio
Viareggio
Viareggio is a city and comune located in northern Tuscany, Italy, on the coast of the Tyrrhenian Sea. With a population of over 64,000 it is the main centre of the northern Tuscan Riviera known as Versilia, and the second largest city within the Province of Lucca.It is known as a seaside resort...
, Tuscany
Tuscany
Tuscany is a region in Italy. It has an area of about 23,000 square kilometres and a population of about 3.75 million inhabitants. The regional capital is Florence ....
reported landing 700 kg (1,543.2 lb) in 2005. In the northeastern Atlantic, this shark is being increasingly targeted by fishers following the decline of other deepwater shark species.
Off Corsica
Corsica
Corsica is an island in the Mediterranean Sea. It is located west of Italy, southeast of the French mainland, and north of the island of Sardinia....
, Sicily
Sicily
Sicily is a region of Italy, and is the largest island in the Mediterranean Sea. Along with the surrounding minor islands, it constitutes an autonomous region of Italy, the Regione Autonoma Siciliana Sicily has a rich and unique culture, especially with regard to the arts, music, literature,...
, and southern Portugal, and in the Ionian
Ionian Sea
The Ionian Sea , is an arm of the Mediterranean Sea, south of the Adriatic Sea. It is bounded by southern Italy including Calabria, Sicily and the Salento peninsula to the west, southern Albania to the north, and a large number of Greek islands, including Corfu, Zante, Kephalonia, Ithaka, and...
, southern Adriatic, and Aegean Seas, most of the blackmouth catsharks captured are immature, suggesting there has been a negative impact of fishing pressure. However, the species remains extremely abundant in a number of areas, and survey and fishery data have not shown any evidence of overall population decline. The wide range of depths it occupies likely afford it some protection against fishing, particularly given a 2005 ban on trawling deeper than 1000 m (3,280.8 ft) in the Mediterranean. Therefore, the International Union for Conservation of Nature (IUCN) has listed the blackmouth catshark under Least Concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...
. In the waters of the European Commission
European Commission
The European Commission is the executive body of the European Union. The body is responsible for proposing legislation, implementing decisions, upholding the Union's treaties and the general day-to-day running of the Union....
, fishing for this species is managed as part of the Total Allowable Catch (TAC) for deepwater sharks.