Basking shark 898756 224667872 2008-07-09T21:57:23Z A.b.s 795474 {{Taxobox | name = Basking shark | fossil_range = Early [[Oligocene]] to Present<ref>{{cite journal | last = Sepkoski | first = Jack | authorlink = | coauthors = | title = A compendium of fossil marine animal genera (Chondrichthyes entry) | journal = Bulletins of American Paleontology | volume = 364 | issue = | pages = p.560 | publisher = | location = | date = 2002 | url = http://strata.ummp.lsa.umich.edu/jack/showgenera.php?taxon=575&rank=class | doi = | id = | accessdate = 2008-01-09 }}</ref> | status = VU | trend = not known | status_system = iucn2.3 | status_ref =<ref name="iucn">{{IUCN2006|assessors=Fowler|year=2000|id=4292|title=Cetorhinus maximus|downloaded=11 May 2006}} Database entry includes justification for this species' status </ref> | image = Basking Shark.jpg | image_width = 200px | regnum = [[Animal]]ia | phylum = [[Chordate|Chordata]] | classis = [[Chondrichthyes]] | subclassis = [[Elasmobranchii]] | ordo = [[Lamniformes]] | familia = '''Cetorhinidae''' | familia_authority = [[Theodore Nicholas Gill|Gill]], 1862 | genus = '''''Cetorhinus''''' | genus_authority = [[Henri Marie Ducrotay de Blainville|Blainville]], 1816 | species = '''''C. maximus''''' | binomial = ''Cetorhinus maximus'' | binomial_authority = ([[Johann Ernst Gunnerus|Gunnerus]], 1765) | range_map = Basking shark distribution.gif | range_map_width = 200px | range_map_caption = Range (in blue) }} The '''basking shark''', ''Cetorhinus maximus'', is the second largest [[fish]], after the [[whale shark]]. It is a [[cosmopolitan species]] — it is found in all the world's temperate oceans. It is a slow moving and generally harmless [[filter feeder]]. Like other large [[shark]]s, basking sharks are at risk of [[extinction]] due to a combination of low resilience and [[overfishing]] to supply the worldwide market for the shark's fins, flesh and organs. ==Taxonomy== This shark is called the ''basking'' shark because it is most often observed when feeding at the surface and appears to be [[wikt:bask|basking]]. It is the only member of the family Cetorhinidae. It was first described and named ''Cetorhinus maximus'' by [[Gunnerus]] in 1765 from a specimen found in [[Norway]]. The genus name ''Cetorhinus'' comes from the Greek, ''ketos'' which means marine monster or whale and ''rhinos'' meaning nose, the species name ''maximus'' is from Latin and means "greatest". It was later described as ''Squalus isodus'' by Macri in 1819, ''Squalus elephas'' by [[Lesueur]] in 1822, ''Squalus rashleighanus'' by Couch in 1838, ''Squalus cetaceus'' by Gronow in 1854, ''Cetorhinus blainvillei'' by Capello in 1869, ''Selachus pennantii'' by Cornish in 1885, ''Cetorhinus maximus infanuncula'' by Deinse & Adriani 1953, and finally as ''Cetorhinus maximus normani'' by Siccardi 1961.<ref name=FLMNH>{{cite web|author=C. Knickle, L. Billingsley & K. DiVittorio|title=Biological Profiles basking shark|publisher=Florida Museum of Natural History|accessdate=2006-08-24|url=http://www.flmnh.ufl.edu/fish/Gallery/Descript/baskingshark/baskingshark.html}}</ref> ==Distribution and habitat== The basking shark is a coastal-[[pelagic]] shark found worldwide in boreal to warm-temperate waters around the continental shelves. It prefers waters between 8 and 14°&nbsp;[[Celsius|C]] (46 and 57°&nbsp;[[fahrenheit|F]]). It is often seen close to land and will enter enclosed bays. The shark will follow concentrations of [[plankton]] in the water column and is therefore often visible on the surface. They are a highly migratory species leading to seasonal appearances in certain areas of the range.<ref name="FAO">{{cite book|author=Leonard J. V. Compagno| title=Sharks of the World: An annotated and illustrated catalogue of shark species known to date|publisher=Food and Agriculture Organization of the United Nations|date=1984}}</ref> ==Anatomy and appearance== [[Image:basking shark.png|thumb|220px|right|Male basking shark]] The basking shark is one of the largest known sharks, second only to the [[whale shark]]. The largest specimen accurately measured was trapped in a herring net in the [[Bay of Fundy]], [[Canada]] in 1851. Its total length was {{convert|12.27|m|ft|lk=on}}, and it weighed an estimated 19&nbsp;[[ton]]s. There are reports from [[Norway]] of three basking sharks over 12&nbsp;m (the largest being 13.7&nbsp;m), but those are considered dubious since few if any sharks anywhere near such size have been caught in the area since. Normally the basking shark reaches a length of between {{convert|6|m|ft}} and a little over {{convert|8|m|ft}}. Some specimens surpass 9 or even {{convert|10|m|ft}}, but after years of hard fishing, specimens of this size have become exceedingly rare. These sharks possess the typical [[lamniform]] body plan and have been mistaken for [[great white shark]]s. The two species can be easily distinguished, however, by the basking shark's cavernous jaw (up to 1&nbsp;m in width, held wide open whilst feeding), longer and more obvious [[gill]] slits (which nearly encircle the head and are accompanied by well-developed [[gill raker]]s), smaller eyes, and smaller average girth. Great white sharks possess large, dagger-like teeth, whilst those of the basking shark are much smaller (5&ndash;6&nbsp;mm) and hooked; only the first 3 or 4 rows of the upper jaw and 6 or 7 rows of the lower jaw are functional. There are also several behavioural differences between the two (see [[#Behaviour|Behaviour]]). Other distinctive characteristics of the basking shark include a strongly keeled [[caudal peduncle]], highly textured skin covered in [[placoid scale]]s and a layer of mucus, a pointed snout (which is distinctly hooked in younger specimens), and a lunate [[caudal fin]]. In large individuals the [[dorsal fin]] may flop over when above the surface. Colouration is highly variable (and likely dependent on observation conditions and the condition of the animal itself): commonly, the colouring is dark brown to black or blue dorsally fading to a dull white ventrally. The sharks are often noticeably scarred, possibly through encounters with [[lamprey]]s or [[cookiecutter shark]]s. The basking shark's liver, which may account for 25% of its body weight, runs the entire length of the abdominal cavity and is thought to play a role in [[buoyancy]] regulation and long-term energy storage. In females, only the right [[ovary]] appears to be functional: if so, this is a unique characteristic among sharks. ==Diet== The basking shark is a passive [[filter feeder]], filtering [[plankton|zooplankton]], small fish and [[invertebrate]]s from up to 2,000 tons of water per hour.<ref name="FLMNH"/> Unlike the [[megamouth shark]] and [[whale shark]], the basking shark does not appear to actively seek its quarry, but it does possess large [[olfactory bulb]]s that may guide it in the right direction. Unlike the other large filter feeders, it relies only on the water that is pushed through the gills by swimming; the megamouth shark and whale shark can suck or pump water through their gills.<ref name="FLMNH"/> == Behaviour == [[Image:Basking head.jpg|thumb|right|250px|Head of a basking shark.]] Studies in 2003 have disproved the idea that basking sharks hibernate and have shown that they are active throughout the year.<ref>http://www.baskingsharks.org/view_folder.asp?folderid=6230&level2id=6212&rootid=6212&depth=2&level1=&toptab=1</ref> In winter, basking sharks move to deeper water (depths of up to 900 m) feeding on deep water plankton. Satellite tagging confirmed that basking sharks move thousands of kilometres during the winter months locating plankton blooms. It was also found that basking sharks shed and renew their gillrakers in an ongoing process, rather than over one short period. They feed at or close to the surface with their mouths wide open and gill rakers erect. They are slow-moving sharks (feeding at about 2&nbsp;[[knot (speed)|knot]]s) and do not attempt to evade approaching boats (unlike great white sharks). They are harmless to humans if left alone and will not be attracted to chum. Basking sharks are social animals and form schools segregated by sex, usually in small numbers (3 or 4) but reportedly up to 100 individuals.<ref name="FAO" /> Their social behaviour is thought to follow visual cues, as although the basking shark's eyes are small, they are fully developed and have been known to visually inspect boats, possibly mistaking them for conspecifics.<ref name=ELASMO>{{cite web|author=Martin, R. Aidan|title=A Curious Basker|publisher=SHARK-L|accessdate=2006-08-03|url=http://web.archive.org/web/20041020005715/http://www.elasmo.com/martin/curious.html}}</ref> Females are thought to seek out shallow water to give birth. These sharks have few predators, but [[orca]]s and [[tiger shark]]s are known to feed on them, and the aforementioned [[lamprey]]s are often seen attached to them, although it is unlikely that they are able to cut through the shark's thick skin.<ref name="FAO" /> Even though the basking shark is large and slow it can [[Breaching|breach]] and has been reported jumping fully out of the water.<ref name="PSRF">{{cite web| author=Pelagic Shark Research Foundation| title=PSRF Shark Image Library | publisher=PSRF| accessdate=2006-06-01| url=http://www.pelagic.org/image_lib/basking.html}}</ref> This behaviour could be an attempt to dislodge parasites or [[comensals]].<ref name="FAO" /> There are doubts as to the accuracy of these observations - since the basking shark has a recorded top swimming speed of {{convert|4|mi/h|km/h|abbr=on}} and has not been observed to jump, even under the stress of harpooning.<ref name="FAO" /> == Reproduction == Basking sharks are [[Ovoviviparity|ovoviviparous]]: the developing embryos first rely on a [[yolk]] sac, and as there is no [[placenta]]l connection, they later feed on unfertilized [[ovum|ova]] produced by the mother (a behaviour known as [[oophagy]]). [[Gestation]] is thought to span over a year (but perhaps 2 or 3 years), with a small though unknown number of young born fully developed at 1.5&ndash;2&nbsp;m (5&ndash;6.5&nbsp;ft). Only one pregnant female is known to have been caught; she was carrying 6 unborn young.<ref name="Trust">{{cite web| author=The Shark Trust| title=Basking Shark Factsheet | publisher=The Shark Trust| accessdate=2006-07-07| url=http://www.sharktrust.org/do_download.asp?did=26369}}</ref> Mating is thought to occur in early summer and birthing in late summer, following the female's movement into shallow coastal waters. The onset of maturity in basking sharks is not known but is thought to be between the age of 6 and 13 and at a length of between 4.6 and 6&nbsp;m. Breeding frequency is also unknown, but is thought to be 2 to 4 years. The seemingly useless teeth of basking sharks may play a role before birth since the basking shark seems to feed on unfertilized eggs in utero.<ref name="elasmo">{{cite web| author="Martin, R. Aidan"| title="Biology of the Basking Shark(Cetorhinus maximus)"| Publisher="ReefQuest Centre for Shark Researc"| accessdate=2008-06-08| url=http://www.elasmo-research.org/education/shark_profiles/cetorhinus.htm}}</ref> ==Importance to humans == [[Image:Basking shark Harper's Weekly October 24, 1868.jpg|thumb|200px|right|The "wonderful fish" described in ''Harper's Weekly'' on [[October 24]], [[1868]], was likely the remains of a basking shark.]] Historically, the basking shark has been a staple of fisheries because of its slow swimming speed, unaggressive nature and previously abundant numbers. Commercially it was put to many uses: the flesh for food and fishmeal, the hide for [[leather]], and its large [[liver]] (which has a high [[squalene]] content) for [[oil]].<ref name="FAO" /> It is currently fished mainly for its fins (for [[shark fin soup]]). Parts (such as [[Shark cartilage|cartilage]]) are also used in [[traditional Chinese medicine]] and as an [[aphrodisiac]] in [[Japan]], further adding to demand. As a result of rapidly declining numbers, the basking shark has been protected and trade in its products restricted in many countries. It is fully protected in the [[UK]], [[Malta]], [[Florida]] and [[US]] Gulf and [[Atlantic Ocean|Atlantic waters]]. Targeted fishing for basking sharks is illegal in [[New Zealand]].<ref name="Trust"/> It is tolerant of boats and divers approaching it and may even circle divers, making it an important draw for dive tourism in areas where it is common. ==Basking sharks and cryptozoology== On several occasions, "[[globster]]" corpses initially thought to be [[sea serpent|sea serpents ]] or [[plesiosaurs]] have later been identified as likely to be the decomposing carcasses of basking sharks, as in the [[Stronsay beast]] and the ''[[Zuiyo Maru]]'' cases. ==See also== {{Sharksportal}} * [[List of sharks]] * [[List of fish common names]] * [[List of fish families]] ==References== {{reflist}} ;General references {{refbegin}} * {{FishBase_species|genus=Cetorhinus |species=maximus|year=2005|month=10}} * {{ITIS|ID=159907|taxon=Cetorhinus maximus|year=2006|date=23 January}} * David A Ebert, ''Sharks, Rays and Chimaeras of California'', ISBN 0-520-23484-7 * {{marinebio|id=193|name=Basking shark, ''Cetorhinus maximus''}} * Marine Conservation Society [http://www.mcsuk.org/marineworld/baskingsharks/welcome| Basking shark page] * FAO Figis [http://www.fao.org/figis/servlet/species?sname=Cetorhinus%20maximus Species Fact Sheet for basking shark ] {{refend}} == External links == {{commonscat|Cetorhinus maximus}} * {{marinebio|id=193|name=Basking shark, Cetorhinus maximus}} * [http://www.arkive.org/species/GES/fish/Cetorhinus_maximus ARKive entry on the Basking Shark] * [http://www.sharkinformation.org/sharkprofiles/basking-shark/ Basking Shark Profile and Photos] * [http://www.youtube.com/watch?v=lkXThN6gTcU&eurl=http%3A%2F%2Fwww%2Ejapanprobe%2Ecom%2F%3Fp%3D1649 9 m Basking Shark captured in Japan] * [http://www.baskingsharks.org/view_folder.asp?folderid=6230&level2id=6212&rootid=6212&depth=2&level1=&toptab=1 Basking Shark Project] * [http://195.12.2.23/basking/base.htm The basking shark web page] * [http://www.pac.dfo-mpo.gc.ca/sci/sa-mfpd/elasmobranchs/baskingshark.htm Fisheries & Oceans Canada - Basking sharks on the west coast of Canada] [[Category:Cetorhinidae]] [[Category:Ovoviviparous fish]] [[ca:Tauró pelegrí]] [[cs:Žralok veliký]] [[da:Brugde]] [[de:Riesenhai]] [[es:Cetorhinus maximus]] [[fr:Requin pèlerin]] [[ko:돌묵상어]] [[id:Hiu penjemur]] [[is:Beinhákarl]] [[it:Cetorhinus maximus]] [[he:כריש ענק]] [[hu:Óriáscápa]] [[nl:Reuzenhaai]] [[ja:ウバザメ]] [[no:Brugde]] [[nn:Brugde]] [[pl:Długoszpar]] [[pt:Tubarão-elefante]] [[ru:Гигантская акула]] [[fi:Jättiläishai]] [[sv:Brugd]] [[tr:Dev köpekbalığı]] [[zh:姥鲨]]