Kitefin shark
| Kitefin shark Temporal range: Eocene to Present
| |
|---|---|
| |
| Scientific classification | |
| Kingdom: | |
| Phylum: | |
| Class: | |
| Subclass: | |
| Order: | |
| Family: | |
| Genus: | Dalatias Rafinesque, 1810
|
| Species: | D. licha
|
| Binomial name | |
| Dalatias licha (Bonnaterre, 1788)
| |
| |
| Range of the kitefin shark | |
| Synonyms | |
|
Dalatias sparophagus* Rafinesque, 1810 * ambiguous synonym | |
Template:FixHTML Template:Sharksportal Template:FixHTML The kitefin shark, Dalatias licha, 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 200–600 m (660–2,000 ft). This shark has a slender body with a very short, blunt snout, large eyes, and thick lips. Its teeth are highly differentiated between the upper and lower jaws, with the upper teeth small and narrow and the lower teeth large, triangular, and serrated. Its typical length is 1.0–1.4 m (2.5–4.0 ft).
With a sizable oil-filled liver to maintain neutral buoyancy, the kitefin shark is able to cruise slowly through the water while expending little energy. Armed with large teeth and a strong bite, it is a powerful, solitary predator that takes many different types of prey, ranging from bony fishes, sharks and rays, to cephalopods, crustaceans, polychaete worms, siphonophores, and possibly carrion. It also takes bites out of animals larger than itself, similar to its smaller relative, the cookiecutter shark (Isistius brasiliensis). This shark is ovoviviparous and gives birth to 10–14 young. The kitefin shark is fished commercially for its meat, skin, and liver oil, primarily by Portugal and Japan. A fishery targeting this species existed off the Azores from the 1970s to the 1990s, but collapsed due to overfishing and falling liver oil prices; the rapid depletion of the Azores stock is often cited as an example of the susceptibility of deep-sea sharks to human exploitation. The World Conservation Union does not yet have sufficient data to assess the global conservation status of this species.
Taxonomy
The kitefin shark was originally described as Squalus licha by French naturalist Pierre Joseph Bonnaterre, in his 1788 Tableau encyclopédique et méthodique des trois regnes de la nature; the type specimen from "Le cap Breton" has since been lost. This species was later placed in its own genus, Dalatias, which came from the synonymy of Constantine Rafinesque's 1810 Dalatias sparophagus with S. licha. However, some authorities dispute this on the grounds that D. sparophagus is a nomen dubium, and prefer to use the next available genus name Scymnorhinus.[3] The genus name Dalatias is derived from the Greek dalos or dalou, meaning "torch".[4] The specific epithet licha comes from la liche, an old French name for this shark.[5] Other common names for the kitefin shark include seal shark, black shark, and darkie Charlie.[4]
Phylogeny and evolution
Clastic studies have consistently found that the closest relatives of the kitefin shark are the cookiecutter sharks (Isistius), with which they share several dentitional, skeletal, and muscular similarities.[6][7] Dalatias and Isistius are believed to have evolutionarily diverged shortly after the transition between the Cretaceous and Tertiary periods (65.5 Ma), as part of a larger adaptive radiation of dogfish sharks from the deep sea into relatively shallower habitats.[6]
The oldest fossil teeth that definitively belong to the kitefin shark date to the Middle Miocene epoch, such as those recovered from Bortonian-stage deposits (43.0–37.0 Ma) in New Zealand.[1] Dalatias fossil teeth dating to various ages have also been discovered in Europe, the former U.S.S.R., Japan, and western India.[8] The fossil material now recognized as belonging to this species were historically described under a multitude of different names.[1]
Distribution and habitat
The kitefin shark has an almost circumglobal range in tropical and warm-temperature waters, consisting of a number of widely separated populations with likely little interchange between them.[9] This shark has not been reported from the eastern Pacific and northern Indian Oceans. In the northern Atlantic, it occurs in the Georges Bank and the northern Gulf of Mexico, and from the North Sea to Cameroon, including around the British Isles, the Mediterranean Sea, Madeira, and the Azores. In the Indian Ocean, it is found off South Africa and Mozambique. In the Pacific, it occurs off Japan, Java, Australia and New Zealand, and the Hawaiian Islands. There is a single known record of this species in the southern Atlantic, from off southern Brazil.[3][10]
An offshore, deepwater species, the kitefin shark is most common at a depth of 200–600 m (660–2,000 ft), but has been captured from the surface to as deep as 1,800 m (5,900 ft).[10][11] It inhabits the outer continental shelves and upper continental slopes, and is also found around oceanic islands and seamounts.[8] This shark is the only member of its family that tends to be found close to the sea floor as opposed to in the middle of the water column, though on occasion it has been captured well above the bottom.[8]
Description
The kitefin shark has a moderately elongated body with a very short, rounded snout. The eyes and spiracles are large. The lips are thick with pleats or fringes, though are not modified to be suctorial. There are 16–21 tooth rows in the upper jaw and 17–20 tooth rows in the lower jaw.[3] The upper teeth are small and spike-shaped, curving slightly towards the corners of the mouth. The lower teeth are very large, knife-shaped, and serrated, with their bases interlocking to form a continuous cutting surface.[11]
The first dorsal fin is slightly smaller and shorter-based than the second, and neither has spines. The first dorsal fin originates behind the free rear tip of the pectoral fins, while the second originated above the middle of the pelvic fin bases. The pectoral fins are short and rounded. The caudal fin has a prominent upper lobe with a well-developed notch near the tip, and a barely present lower lobe.[3] The form and arrangement of the fins is similar to the Portuguese dogfish (Centroscymnus coelolepis), from which this species can be distinguished by the lack of fin spines.[11] The dermal denticles are small and flat, with a single horizontal ridge ending in a point.[3]
The coloration is a uniform dark brown or gray, sometimes with faint black spots on the back. The fins have white or translucent margins, and the tip of the caudal fin is black.[11] An 90 cm (3.0 ft) long kitefin shark with partial albinism, lacking pigment on 59% of its body, was caught in the Gulf of Genoa in 2003. Unlike in a previous case of an albino Portuguese dogfish, the abnormal coloration of this individual had not diminished its ability to capture prey.[12] Most kitefin sharks are 1.0–1.4 m (2.5–4.0 ft) long; the maximum reported length is 1.6 m (5.2 ft), possibly 1.8 m (6.0 ft).[11]
Biology and ecology
Relatively common where it occurs, kitefin sharks are usually solitary in nature but may form small groups.[10] It is a slow swimmer with a large liver filled with squalene, a lipid less dense than water, allowing it to maintain neutral buoyancy and hover above the bottom with little effort.[3] Studies off the coast of North Africa and in the Gulf of Genoa have found males outnumbering females by 2:1 and 5:1 respectively; this imbalanced sex ratio has not been observed off South Africa and may reflect sampling bias.[13] The kitefin shark is preyed upon by larger fishes and sharks,[11] as well as by sperm whales (Physeter macrocephalus).[14] Parasite data on this species is limited; an examination of two sharks caught off Ireland found three nematodes in the stomach lumen. One could be identified as Anisakis simplex L3, while another may have been a larval Raphidascaris.[15]
A powerful and versatile deepwater predator, the short, robust jaws of the kitefin shark give it an enormously strong bite. It feeds mainly on bony fishes (including deepwater smelts, viperfishes, scaly dragonfishes, barracudinas, greeneyes, lanternfishes, bristlemouths, cod and other gadids, grenadiers, deepwater scorpionfishes, bonito, snake mackerels, deepwater cardinalfishes, and sea toads), but also takes a wide variety of other animals, including skates, smaller sharks (Galeus, Squalus, Etmopterus and Centrophorus), squid and octopus, crustaceans (amphipods, isopods, shrimp and lobsters), polychaete worms, and siphonophores.[3] Like the related cookiecutter shark, the kitefin shark is also capable of excising chunks of flesh from animals larger than itself, including other sharks and whales.[10][16] The presence of fast-swimming fishes in its diet suggests the kitefin shark may scavenge, or have some other means of capturing faster prey. In the Mediterranean, bony fishes are the most important food year-round, with the second-most important prey being sharks in the winter and spring, crustaceans in the summer, and cephalopods in the fall. Captured males are more likely to have full stomachs than females for unknown reasons.[3]
Reproduction in the kitefin shark is ovoviviparous, with the embryos hatching inside the uterus and being sustained to term by a yolk sac. Adult females have two functional ovaries and two functional uteruses; the uterus is not divided into compartments. In the Mediterranean, breeding occurs in the fall and birthing in summer; females may have a year of rest in between pregnancies.[13] The litter size is 10–16, increasing with female size.[9] The young are born at a length of 30–42 cm (12–17 in), varying by geographic location, after a possible gestation period of two years.[17] The males mature sexually at a length of 77–121 cm (2.5–4.0 ft), and the females at a length of 117–159 cm (3.8–5.2 ft).[9] There is no relationship between an individual's size at birth, size at maturity, and maximum size.[13]
Human interactions
The kitefin shark inhabits depths too great for it to be a danger to humans.[11] Its upper teeth have been found lodged in underwater fiberoptic cables.[16] This species has a long history of human exploitation: the meat is consumed in the eastern Atlantic and Japan, and the offal processed into fishmeal. The liver oil is utilized in Portugal, Japan, and South Africa. The skin is made into a type of shagreen useful in the making of furniture and jewelry, and is also favored for the manufacture of "boroso", a Spanish polished leather. This shark has no commercial value in the western Atlantic.[9][11]
Fisheries operating off Portugal and Japan are responsible for most commercial landings of the kitefin shark, generally as bycatch in bottom trawls and on hook-and-line.[11][18] Portugal reported a kitefin shark bycatch of 282 tons in 2000 and 119 tons in 2003; in other areas of the northeastern Atlantic this shark is rare and reported catches are likely to be misidentifications of other species.[19] Catches by the Australian South East Trawl Fishery are increasing following the relaxation of regulations regarding seafood mercury content; this species is not included under Australian fishery quotas.[11] New Zealand kitefin shark catches peaked from 1986 to 1997.[20]
Due to a paucity of specific fisheries data, the kitefin shark is listed as Data Deficient on the IUCN Red List. However, the continuing expansion of commercial fisheries into the deep sea has raised concerns about the vulnerability of this and other deepwater shark species to overfishing, as these sharks have slow growth and reproductive rates. This is exemplified by the rapid stock depletion and collapse of the Azores kitefin shark fishery.[2] This targeted fishery began in the early 1970s for the production of liver oil. In the early 1980s, the fishing fleet was enlarged with the addition of industrial vessels equipped with demersal gillnets, resulting in a fishery peak in 1984 of 937 tons landed. After 1991, kitefin shark catches declined precipitously to under 15 tons annually which, along with a drop in the global price of liver oil, led to the fishery becoming unprofitable by the end of the decade. Population assessments suggested the northwestern Atlantic stock had fallen to 50% of the pre-exploitation biomass.[19][20]
See also
References
- ^ a b c Keyes, I.W. (1984). "New records of fossil elasmobranch genera Megascyliorhinus, Centrophorus, and Dalatias (Order Selachii) in New Zealand". New Zealand Journal of Geology and Geophysics. 27: 203–216.
- ^ a b Template:IUCN2008
- ^ a b c d e f g h Compagno, L.J.V. (1984). Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date. Rome: Food and Agricultural Organization. pp. 63–64. ISBN 9251013845.
- ^ a b Froese, Rainer; Pauly, Daniel (eds.) (2009). "Dalatias licha" in FishBase. June 2009 version.
- ^ Bonnaterre, P.J. (1788). Tableau encyclopédique et méthodique des trois regnes de la nature. Chez Panckoucke. p. 12.
- ^ a b Adnet, S. and Cappetta, H. (September 2001). "A palaeontological and phylogenetical analysis of squaliform sharks (Chondrichthyes: Squaliformes) based on dental characters". Lethaia. 34 (3): 234–248.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Shirai, S. (1996). "Phylogenetic Interrelationships of Neoselachians (Chondrichthyes: Euselachii)". In Stiassny, M.L.J., Parenti, L.R. and Johnson, G.D. (ed.). Interrelationships of Fishes. Academic Press. pp. 9–34. ISBN 0126709505.
{{cite book}}: CS1 maint: multiple names: editors list (link) - ^ a b c Carrier, J.C., Musick, J.A. and Heithaus, M.R. (2004). Biology of Sharks and Their Relatives. CRC Press. p. 58. ISBN 084931514X.
{{cite book}}: CS1 maint: multiple names: authors list (link) - ^ a b c d Fowler, S.L., Cavanagh, R.D., Camhi, M., Burgess, G.H., Cailliet, G.M., Fordham, S.V., Simpfendorfer, C.A. and Musick, J.A. (2005). Sharks, Rays and Chimaeras: The Status of the Chondrichthyan Fishes. International Union for Conservation of Nature and Natural Resources. pp. 230–231. ISBN 2831707005.
{{cite book}}: CS1 maint: multiple names: authors list (link) - ^ a b c d Soto, J.M.R. and Mincarone, M.M. (2001). "First record of kitefin shark, Dalatias licha (Bonnaterre, 1788) (Chondrichthyes, Dalatiidae), in the south Atlantic". Mare Magnun. 1 (1): 23–26.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ a b c d e f g h i j Bester, C. and Burgess, G. Biological Profiles: Kitefin Shark. Florida Museum of Natural History Ichthyology Department. Retrieved on June 15, 2009.
- ^ Bottaro, M., Ferrando, S., Gallus, L., Girosi, L. and Vacchi, M. (2005). "First record of albinism in the deep water shark Dalatias licha" Reference No. 5115. JMBA2–Biodiversity Records.
- ^ a b c Capapé, C., Hemida, F. and Quignard, J.P. (2008). "Biological observations on a rare deep-sea shark, Dalatias licha (Chondrichthyes: Dalatiidae), off the Maghreb coast (south-western Mediterranean)". Pan-American Journal of Aquatic Sciences. 3 (3): 355–360.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Gómez-Villota, F. (2007). Sperm whale diet in New Zealand. Master of Applied Science thesis. Auckland University of Technology.
- ^ Henderson, A.C., Flannery, K. and Dunne, J. (2003). "Biological observations on shark species taken in commercial fisheries to the west of Ireland". Biology and Environment. 103B: 1–7.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ a b Musick, J.A. and McMillan B. (2003). The Shark Chronicles: A Scientist Tracks the Consummate Predator. Macmillan. pp. 122–123. ISBN 0805073590.
- ^ da Silva, H.M. (1988). "Growth and reproduction of kitefin shark, Dalatias licha (Bonn 1788) in Azorean waters." ICES, Demersal Fish Committee CM 1988/G:21. pp. 1–16.
- ^ Castro, J.I., Woodley, C.M. and Brudek, R.L. (1999). A preliminary evaluation of the status of shark species. FAO Fisheries Technical Paper No. 380.
- ^ a b ICES. (2007). Report of the Working Group Elasmobranch Fishes (WGEF), 22–28 June 2007, Galway, Ireland. ICES CM 2007/ACFM:27. pp. 52–55.
- ^ a b Perrotta, R. (2004). "Kitefin shark, Dalatias licha (dalatiidae) fishery in the north eastern Atlatic and some recommendations for elasmobranchs exploitation". Revista de Investigación y Desarollo Pesquero. 16: 97–101.