View source for Blue shark

{{Short description|Species of shark}}
{{Use dmy dates|date=July 2022}}
{{speciesbox
| fossil_range = [[Miocene]]-recent{{Fossil range|Early Miocene|Recent|<ref>{{cite journal
 |last=Sepkoski
 |first=Jack
 |title=A compendium of fossil marine animal genera (Chondrichthyes entry)
 |journal=Bulletins of American Paleontology
 |volume=364|isbn=978-0-87710-450-6
 |page=560
 |year=2002
|url=http://strata.ummp.lsa.umich.edu/jack/showgenera.php?taxon=575&rank=class
 |access-date=2008-01-09
 |archive-url=https://web.archive.org/web/20120510170834/http://strata.ummp.lsa.umich.edu/jack/showgenera.php?taxon=575&rank=class
 |archive-date=2012-05-10
}}</ref>
}}
| image = Tiburón azul (Prionace glauca), canal Fayal-Pico, islas Azores, Portugal, 2020-07-27, DD 31.jpg
| image_caption = A blue shark in the [[Azores]]
| status = NT
| status_system = IUCN3.1
| status_ref = <ref name="iucn" />
| status2 = CITES_A2
| status2_system = CITES
| status2_ref = <ref name="fishbase"/>
| genus = Prionace
| parent_authority = [[Theodore Edward Cantor|Cantor]], 1849
| species = glauca
| authority = ([[Carl Linnaeus|Linnaeus]], [[10th edition of Systema Naturae|1758]])
| range_map = Cypron-Range Prionace glauca.svg
| range_map_caption = Range of the blue shark
| synonyms = {{species list|hidden=yes
|Carcharhinus macki| (Phillipps, 1935)
|Carcharias aethiops| Philippi, 1902
|Carcharias glaucus| (Linnaeus, 1758)
|Carcharias gracilis| Philippi, 1887
|Carcharias hirundinaceus| Valenciennes, 1839 
|Carcharias pugae| Pérez Canto, 1886
|Carcharias rondeletii| (Risso, 1810)
|Carcharinus glaucus| (Linnaeus, 1758)
|Galeus thalassinus| Valenciennes, 1835
|Glyphis glaucus| (Linnaeus, 1758)
|Hypoprion isodus| Philippi, 1887
|Isurus glaucus| (Linnaeus, 1758)
|Prionace mackiei |Phillipps, 1935
|Prionacea glauca |(Linnaeus, 1758)
|Squalus adscensionis| Osbeck, 1765
|Squalus caeruleus| Blainville, 1816
|Squalus glaucus |Linnaeus, 1758
|Squalus rondeletii| Risso, 1810
|Thalassinus rondeletii| (Risso, 1810)
|Thalassinus rondeletti |(Risso, 1810)
|Thalassinus rondelettii |(Risso, 1810)
|Thalassorhinus vulpecula |Valenciennes, 1839}}
|synonyms_ref = <ref name="fishbase"/>
}}

The '''blue shark''' ('''''Prionace glauca'''''), also known as the '''great blue shark''', is a [[species]] of [[requiem shark]] in the [[family (biology)|family]] [[Requiem shark|Carcharhinidae]] which inhabits deep waters in the world's [[temperate]] and [[tropical]] oceans. It is the only species of genus '''''Prionace'''''.<ref>{{Cite journal |last1=Silva |first1=Thaísy Emmanuelle Florentino da |last2=Lessa |first2=Rosangela |last3=Santana |first3=Francisco Marcante |date=2021-01-21 |title=Current knowledge on biology, fishing and conservation of the blue shark (Prionace glauca) |url=https://neotropical.pensoft.net/article/58691/ |journal=Neotropical Biology and Conservation |language=en |volume=16 |issue=1 |pages=71–88 |doi=10.3897/neotropical.16.e58691 |bibcode=2021NeoBC..16...71D |doi-access=free |issn=2236-3777}}</ref> Averaging around {{convert|3.1|m|ft|abbr=on}} and preferring cooler waters,<ref name="FAO">{{cite book|author= Compagno, Leonard J.V. | 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 |year=1984|pages=521–524, 555–561, 590|url=http://www.fao.org/3/ad123e/ad123e32.pdf}}</ref> the blue shark [[Fish migration|migrates]] long distances, such as from [[New England]] to South America. It is listed as [[near-threatened species|Near Threatened]] by the [[International Union for Conservation of Nature|IUCN]].

Although generally [[Lethargy|lethargic]], they can move very quickly. Blue sharks are [[viviparous]] and are noted for large litters of 25 to over 100 pups. They feed primarily on small fish and [[squid]], although they can take larger prey. Some of the blue shark's predators include the killer whale and larger sharks like tiger sharks and the great white shark.<ref name="orcashark"/> Their maximum lifespan is still unknown, but it is believed that they can live up to 20 years.<ref>[http://www.fishaq.gov.nl.ca/research_development/fdp/sharks.pdf Sharks, Emerging Species Profile Sheets, published by the Department of Fisheries and Aquaculture, Government of Newfoundland and Labrador] in ''Emerging Species Profile Sheets''. Department of Fisheries and Aquaculture, Canada. {{webarchive |url=https://web.archive.org/web/20131007032759/http://www.fishaq.gov.nl.ca/research_development/fdp/sharks.pdf |date=October 7, 2013}}</ref> They are one of the most abundant [[pelagic]] sharks, with large numbers being caught by fisheries as bycatch on longlines and nets.<ref>Nakano, H., & Stevens, J.D. (2008). The biology and ecology of the blue shark, Prionace glauca. Sharks of the open ocean: Biology, fisheries and conservation, 140–151.</ref>

The earliest fossil teeth of this species are known from the [[Miocene]] of [[Sri Lanka]]. Other fossil teeth of this species are known from the Miocene and Pliocene of Chile, Italy, and possibly Belgium.<ref>{{Cite journal |last1=Höltke |first1=Olaf |last2=Maxwell |first2=Erin E. |last3=Rasser |first3=Michael W. |date=2024-02-26 |title=A Review of the Paleobiology of Some Neogene Sharks and the Fossil Records of Extant Shark Species |journal=Diversity |language=en |volume=16 |issue=3 |page=147 |bibcode=2024Diver..16..147H |doi=10.3390/d16030147 |issn=1424-2818 |doi-access=free}}</ref>

==Taxonomy==
A 2023 study suggested that the species should be reclassified into the genus ''[[Carcharhinus]]''.<ref>{{cite journal|last1=da Silva|first1=Rodrigues-Filho LF|last2=da Costa Nogueira|first2=P|last3=Sodré|first3=D|last4=da Silva|first4=Leal JR|last5=Nunes|first5=JL|last6=Rincon|first6=G|last7=Lessa|first7=RP|last8=Sampaio|first8=I|last9=Vallinoto|first9=M|last10=Ready|first10=JS|last11=Sales|first11=JB|doi=10.1155/2023/4798805|title= Evolutionary History and Taxonomic Reclassification of the Critically Endangered Daggernose Shark, a Species Endemic to the Western Atlantic|date= 22 July 2025|journal= Journal of Zoological Systematics and Evolutionary Research |volume=2023 |pages=1–16 |doi-access=free }}</ref>

==Distribution and habitat==
The blue shark is an oceanic and [[epipelagic zone|epipelagic]] shark found worldwide in deep [[temperate]] and [[tropical]] waters from the surface to about {{convert|350|m|ft|abbr=on}}.<ref name="fishbase">{{FishBase|id=898||genus=Prionace|species=glauca|date=September 2006}}</ref> In temperate seas it may approach shore, where it can be observed by divers; while in tropical waters, it inhabits greater depths. It lives as far north as [[Norway]] and as far south as [[Chile]]. Blue sharks are found off the coasts of every continent, except [[Antarctica]]. Its greatest [[Pacific]] concentrations occur between [[20th parallel north|20°]] and [[50th parallel north|50°&nbsp;North]], but with strong seasonal fluctuations. In the tropics, it spreads evenly between [[20th parallel north|20°&nbsp;N]] and [[20th parallel south|20°&nbsp;S]].<ref name="FAO" /> It prefers water temperatures between {{convert|12|and(-)|20|C|F|abbr=on}}, but can be seen in water ranging from {{convert|3.9|to(-)|31|C|F|abbr=on}}.<ref>{{cite book|last1=Domingo |first1=A. |last2=Forselledo |first2=R. |last3=Mas |first3=F. |last4=Miller |first4=P. |year=2022 |chapter=Blue shark |title=ICCAT Manual|url=https://www.researchgate.net/publication/372241153}}</ref> Records from the [[Atlantic]] show a regular clockwise migration within the prevailing currents.<ref name="FAO" />
==Description==
<gallery mode="packed">
Prionace glauca jaw.jpg|Jaws
Prionace glauca upper teeth.jpg|Upper teeth
Prionace glauca lower teeth.jpg|Lower teeth
</gallery>
[[File:Blauhai (128648419) (cropped).jpeg|thumb|In the Azores]]
Blue sharks are light-bodied with long [[pectoral fin]]s. Like many other sharks, blue sharks are [[countershading|countershaded]]: the top of the body is deep blue, lighter on the sides, and the underside is white. The male blue shark commonly grows to {{convert|1.82|to|2.82|m|ft|abbr=on}} at maturity, whereas the larger females commonly grow to {{convert|2.2|to|3.3|m|ft|abbr=on}} at maturity.<ref name="flmnh">[http://www.flmnh.ufl.edu/fish/Gallery/Descript/blueshark/blueshark.html FLMNH Ichthyology Department: Blue Shark] {{Webarchive|url=https://web.archive.org/web/20130517114454/http://www.flmnh.ufl.edu/fish/Gallery/Descript/BlueShark/BlueShark.html |date=2013-05-17 }}. Flmnh.ufl.edu. Retrieved on 2012-12-19.</ref> Large specimens can grow to {{convert|3.8|m|ft|abbr=on}} long. Occasionally, an outsized blue shark is reported, with one widely printed claim of a length of {{convert|6.1|m|ft|abbr=on}}, but no shark even approaching this size has been scientifically documented.<ref name="flmnh"/> The blue shark is fairly elongated and slender in build and typically weighs from {{convert|27|to|55|kg|lb|abbr=on}} in males and from {{convert|93|to|182|kg|lb|abbr=on}} in large females.<ref>[http://www.irelandswildlife.com/2011/07/blue-shark-prionace-glauca/ Blue Shark (Prionace glauca) – Ireland's Wildlife] {{Webarchive|url=https://web.archive.org/web/20130421010358/http://www.irelandswildlife.com/2011/07/blue-shark-prionace-glauca/ |date=2013-04-21 }}. Irelandswildlife.com (2011-07-21). Retrieved on 2012-12-19.</ref><ref>[http://www.fishaq.gov.nl.ca/research_development/fdp/sharks.pdf Sharks – Greenland (''Somniosus microcephalus''), Shortfin Mako (''Isurus oxyrinchus''), Blue Shark (''Prionace glauca''), Basking Shark (''Cetorhinus maximus''), and Porbeagle (''Lamna nasus'').] {{webarchive |url=https://web.archive.org/web/20131007032759/http://www.fishaq.gov.nl.ca/research_development/fdp/sharks.pdf |date=October 7, 2013 }} fishaq.gov.nl.ca</ref><ref>[http://www.sea-angling-ireland.org/shark%20-%20blue.htm Sea Angling in Ireland – Blue Shark]. Sea-angling-ireland.org (2006-10-21). Retrieved on 2012-12-19.</ref> Occasionally, a female in excess of {{convert|3|m|ft|0}} will weigh over {{convert|204|kg|lb|abbr=on}}. The heaviest reported weight for the species was {{convert|391|kg|lb|abbr=on}}.<ref>{{usurped|1=[https://web.archive.org/web/20131007000204/http://elasmollet.org/Pg/Pg_large.html Summary of Large Blue Sharks ''Prioncae glauca'' (Carl Linnaeus, 10th edition of Systema Naturae) in progress]}}. elasmollet.org (March 2008)</ref> However, anecdotal claims exist for the species to exceptionally reach {{Cvt|800|-|900|kg|lb}} in weight, though these are not verified.<ref>{{cite book |last1=Flindt |first1=Rainer |title=Amazing Numbers in Biology |date=21 December 2006 |publisher=Springer Science & Business Media |isbn=978-3-540-30147-9 |page=12 |url=https://books.google.com/books?id=9t7Tht1kf88C |language=en}}</ref><ref>{{cite book |last1=Berger |first1=Wolf H. |title=Ocean: Reflections on a Century of Exploration |date=6 May 2009 |publisher=University of California Press |isbn=978-0-520-94254-7 |page=264 |url=https://books.google.com/books?id=nMUqEdOd3NEC |language=en}}</ref> The blue shark is also [[ectotherm]]ic and it has a unique sense of smell.{{Citation needed|date=June 2024}}

==Sensory==
The five senses that blue sharks share with other members of the [[Requiem shark|Carcharhinidae]] family are vision, hearing, lateral line, [[Chemoreceptor|chemoreception]], and [[Electroreception and electrogenesis|electroreception]]. These senses allow them to perceive and react to a variety of [[Biotic material|biotic]] or [[Abiotic component|abiotic]] stimuli in their immediate environment and across a different range of spatial scales.<ref name="Hart">Hart, N.S., & Collin, S.P. (2015). Sharks senses and shark repellents. Integrative zoology, 10(1), 38–64.</ref>

The well-developed eyes of blue sharks exhibit interspecific variations in their eye structure, which are characteristic of adaptations for vision in a variety of light environments, from the brightly lit surface waters to the darkness of the deep sea. The lateral position of the eyes in the head allows a cyclopean visual field of 360° in the vertical plane and between 308° and 338° in the horizontal plane.<ref name="Hart"/>

The morphology of the inner ears of blue sharks is similar to that of other [[Gnathostomata|gnathostomes]]. It consists of a membranous labyrinth that is made up of three semicircular canals that are filled with fluid and arranged orthogonally, as well as three otolithic organs, which are the sacculus, utriculus, and lagena. These sharks are most sensitive to frequencies below roughly 100 Hz, but they can hear sounds up to roughly 1000 Hz.<ref name="Hart"/>

The blue shark's lateral line is a mechanosensory structure that can detect particle motion. As such, it can react to mechanical disturbances caused by [[Fluid dynamics|hydrodynamic]] stimuli that are not auditory. It is used to determine the direction and speed of water currents as well as the vibrations produced by prey, predators, and similar species moving through the water.<ref name="Hart"/>

Blue sharks' chemosensory system is made up of [[Taste|gustation]], and [[Sense of smell|olfaction]], which is a common chemical sense. Functions like intraspecific social interactions, communication, reproduction, and food detection are all linked to smell. [[Gustation]] is mainly related to feeding and involves using taste buds to process food and assess its [[palatability]] through direct contact, which usually results in a decision to swallow or reject it.<ref name="Hart"/>

Blue sharks can detect weak electrical potentials generated by [[wikt:inanimate#Synonyms|inanimate]] objects and other animals through specialized receptors. These sharks use their [[Electromagnetic hypersensitivity|electrical sense]] to locate and capture prey, as well as to avoid [[predators]]. As they move through the Earth's [[magnetic field]], they may also sense the weak electrical fields produced by nearby water [[Ocean current energy|currents]] or their own bodies, which can aid in navigation and orientation.

The [[ampullae of Lorenzini]] are [[Electroreception and electrogenesis|electroreceptors]] of the ampullary type and develop from the lateral line placodes. Each ampulla consists of a pore on the surface of the [[skin]], connected to a narrow dermal chamber called an ampullary bulb by a small canal with a [[diameter]] of about one [[millimetre]]. These sharks are most responsive to fluctuating [[Electric field|electrical fields]] between 0.1 and 10 Hz, with peak sensitivity around 1 Hz.

Although the receptors primarily detect low-frequency alternating currents, they are particularly attracted to steady direct current electric fields. However, for the shark to detect a continuous DC voltage, it must move relative to the voltage source.<ref name="Hart"/>

In the northeastern coast of the United States, it was discovered that blue sharks are able to maintain a straight course for hundreds of kilometres over many days. It appears that the only continuously available cue that could be used to accomplish this is the [[Earth's magnetic field|geomagnetic field]].<ref>Paulin, M.G. (1995). "Electroreception and the compass sense of sharks". ''Journal of Theoretical Biology'', 174(3), 325–339.</ref>

==Reproduction==
===Sexual maturity===
Maturity is assessed by observing sexual products and the developmental stage of [[reproductive organs]].
Five reproductive variables are examined for their relationship to body growth: presence or absence of [[semen]] in the [[ductus deferens]] ampullae, length and wet weight of the [[testicle]], Size and rigidity of the [[claspers]]. To assess maturity, the clasper's inner length and degree of [[calcification]] are recorded: <ref name="Linnaeus">Sexual development, size at maturity, size at maternity and fecundity of the blue shark Prionace glauca (Linnaeus, 1758) in the Southwest Atlantic. ''Fisheries Research'', 160, 18–32.</ref>
Mature males have fully calcified claspers that extend beyond the inner margin of their [[pelvic fins]].<ref name="Mas">Mas, F., Cortés, E., Coelho, R., Defeo, O., Forselledo, R., & Domingo, A. (2023). "New insights into the reproductive biology of the blue shark (Prionace glauca) in the South Atlantic Ocean". ''Fisheries Research'', 262, 106643.</ref>
Immature males have claspers that are either shorter or longer than the inner border but not fully calcified.<ref name="Montealegre">Montealegre-Quijano, S., Cardoso, A.T., Silva, R.Z., Kinas, P.G., & Vooren, C.M. (2014).</ref>

===Mating behaviour===
Male blue sharks primarily court non-pregnant mature females since mating marks on females are common, appearing as several tiny incisions arranged in a semicircle on their [[Anatomical terms of location#Dorsal and ventral|Dorsal]] [[fins]]. These marks are the result of non-feeding bites during [[courtship]] and [[mating]]. Female Blue sharks have [[evolved]] skin three times thicker than that of males to withstand the rigors of [[mating]].<ref name="Montealegre"/>
Female blue sharks are classified as immature, subadult, or mature based on the size and development of their [[ovary]], [[oviducal gland]], and [[uterus]].
Mature females have enlarged [[uterine walls]], a fully differentiated [[oviducal gland]], visible and enlarged [[Ovarian follicle]]s and a right ovary separated and developed from the epigonal organ.
Immature females have an undifferentiated oviducal gland and uterus, a small right ovary lodged within the epigonal organ, and no visible follicles.<ref name="Mas"/>

===Reproductive strategy and lifecycle===
[[File:Juvenile blue shark (cropped).jpg|thumb|Juvenile in [[Galicia (Spain)|Galicia]], [[Spain]]]]Blue sharks are [[viviparous]], with a yolk-sac [[placenta]], giving birth to 4 to 135 pups per litter after a [[gestation]] period of 9 to 12 months. After birth, young sharks are left in specific [[Nursery habitat|nursery]] areas outside adult regions to develop independently. These nurseries offer a safe environment for newborns during their early months. Females mature at five to six years of age,<ref name="FAO" /> while males mature at four to five years. Research suggests that females may exhibit natal and reproductive [[philopatry]], meaning they return to specific sites to give birth.<ref>Mourier, J., & Planes, S. (2021). Kinship does not predict the structure of a shark social network. Behavioral Ecology, 32(2), 211–222.</ref>

==Ecology==
[[Image:Tiburón azul (Prionace glauca), canal Fayal-Pico, islas Azores, Portugal, 2020-07-27, DD 24.jpg|thumb|right|Dorsal view]]
===Migration===
Blue sharks are a highly [[Sharks#Behavior|migratory]] species, travelling vast distances across temperate and tropical waters. Their migrations are influenced by [[seasonal]] changes, [[prey]] availability, and the need for optimal environmental conditions.<ref>Vandeperre, F., Aires-da-Silva, A., Fontes, J., Santos, M., Serrão Santos, R., & Afonso, P. (2014). Movements of blue sharks (Prionace glauca) across their life history. PloS one, 9(8), e103538.</ref> These sharks move both horizontally and vertically. Their swimming behaviour varies depending on the time of day. During the day, blue sharks move at a mean rate of 1.2 kilometers per hour, with a mean [[aquatic locomotion|swimming]] [[speed]] of 1.3 kilometers per hour. At night, their activity increases, with a mean movement rate of 1.8 kilometers per hour and a swimming speed of 2.8 kilometers per hour. These increases in speed often occur during brief dives, particularly at night when sharks exhibit more vertical movement, ranging from [[Shallow water marine environment|shallow waters]] to depths exceeding 100 meters.<ref name ="Sciarrotta">Sciarrotta, T. C., & Nelson, D. R. (1977). Diel behavior of the blue shark, Prionace glauca, near Santa Catalina Island, California. Fish. Bull, 75(3), 519–528.</ref>

Blue sharks are most active at night, particularly in the early evening, with their lowest activity occurring during the early morning hours. During the day, they tend to remain around a depth of 30 meters, while at night they venture slightly deeper, around 40 meters. Most of their time is spent within a depth range of 18 to 42 meters, although they sometimes dive deeper. Their behaviour is also influenced by [[water]] [[temperature]], preferring a narrow range of 14 to 16°C, though they are found in waters between 8.5 and 17.5°C. Blue sharks often swim near the surface in cooler months, but this behaviour decreases during the coldest or warmest months, likely due to surface temperature changes.<ref name="Sciarrotta"/>

===Feeding===
[[Squid]] are the most important prey for blue sharks, but their diet includes other invertebrates, such as [[cuttlefish]], [[blanket octopus]]es, and [[Ocythoe tuberculata|pelagic octopuses]], as well as [[lobster]], [[shrimp]], [[crab]], a large number of bony fishes (such as [[Alepisaurus ferox|long-snouted lancetfish]], [[snake mackerel]] and [[oilfish]]), small sharks, mammalian carrion and occasional sea birds (such as [[great shearwater]]s).<ref name="ADW">{{cite web | url=https://animaldiversity.org/accounts/Prionace_glauca/ | title=Prionace glauca (Blue Shark) | website=[[Animal Diversity Web]] }}</ref> [[Whale]] and porpoise [[blubber]] and meat have been retrieved from the stomachs of captured specimens and they are known to take [[cod]] from trawl nets.<ref name="FAO" /> Sharks have been observed and documented working together as a "pack" to [[herd]] prey into a concentrated group from which they can easily feed. Blue sharks may eat [[tuna]], which have been observed taking advantage of the herding behaviour to opportunistically feed on escaping prey. The observed herding behaviour was undisturbed by different species of shark in the vicinity that normally would pursue the common prey.<ref name=Baitball>{{cite web|last=Monique|first=Fallows|title=Blue Sharks Feeding on Anchovy Baitball|url=http://www.apexpredators.com/blog/blue-sharks-feeding-on-anchovy-baitball.html|publisher=Apex Predators Blog|access-date=6 February 2013|date=29 January 2013|archive-url=https://web.archive.org/web/20130421010928/http://www.apexpredators.com/blog/blue-sharks-feeding-on-anchovy-baitball.html|archive-date=21 April 2013}}</ref> The blue shark can swim at fast speeds, allowing it to catch up with prey easily. Its triangular teeth allow it to easily catch hold of slippery prey.

===Predators===
Younger and smaller individuals may be eaten by larger sharks, such as the [[great white shark]] and the [[tiger shark]]. [[Orca]]s have been reported to hunt blue sharks.<ref name="orcashark">{{cite journal|last1=Fertl|first1=D.|last2=Acevedo-Gutierrez|first2=A.|last3=Darby|first3=F. L.|year=1996|title=A report of killer whales (''Orcinus orca'') feeding on a carcharhinid shark in Costa Rica|journal=Marine Mammal Science|volume=12|issue=4|pages=606–611|doi=10.1111/j.1748-7692.1996.tb00075.x|bibcode=1996MMamS..12..606F |url=http://biol.wwu.edu/mbel/media/pdfs/MarMamSci1996_12.pdf|access-date=2016-11-17|archive-url=https://web.archive.org/web/20170712203600/http://biol.wwu.edu/mbel/media/pdfs/MarMamSci1996_12.pdf|archive-date=2017-07-12}}</ref> This shark may host several species of [[parasite]]s. For example, the blue shark is a [[definitive host]] of the [[tetraphyllidea]]n [[tapeworm]], ''Pelichnibothrium speciosum'' (''[[Prionacestus bipartitus]]''). It becomes infected by eating intermediate hosts, probably [[opah]] (''Lampris guttatus'') and/or [[longnose lancetfish]] (''Alepisaurus ferox'').<ref name=Scholz/>

[[California sea lion]]s (Zalophus californianus), [[Northern elephant seal]]s (''Mirounga angustirostris'') and [[Brown fur seal|Cape fur seals]] (''Arctocephalus pusillus pusillus'') have been observed to feed on blue sharks.<ref>{{cite journal|doi=10.2307/1380857|jstor=1380857|title=California Sea Lions Breeding at Ano Nuevo Island, California|journal=Journal of Mammalogy|volume=65|issue=4|page=695|year=1984|last1=Keith|first1=E. O.|last2=Condit|first2=R. S.|last3=Le Boeuf|first3=B. J.}}</ref><ref>{{Cite journal |last1=Fallows |first1=C. |last2=Benoît |first2=H.P. |last3=Hammerschlag |first3=N. |date=2015-03-16 |title=Intraguild predation and partial consumption of blue sharks Prionace glauca by Cape fur seals Arctocephalus pusillus pusillus |url=https://sharkresearch.rsmas.miami.edu/wp-content/uploads/2012/06/Intraguild-predation-and-partial-consumption-of-blue-sharks-Prionace-glauca-by-Cape-fur-seals-Arctocephalus-pusillus-pusillus-ilovepdf-compressed.pdf |journal=African Journal of Marine Science |volume=37 |issue=1|pages=125–128 |doi=10.2989/1814232X.2015.1013058 |bibcode=2015AfJMS..37..125F |s2cid=2563222 }}</ref>

Despite having excellent [[binocular vision]] and the capacity to see ahead when pursuing [[prey]], research indicates that blue sharks are not always adept at spotting [[predators]] approaching from behind. According to an experiment, a large predator's best attack angle when pursuing a blue shark is probably from the caudal direction. This puts the predator in a position to strike the [[caudal fin]] of the shark and immobilize it. Blue sharks are not totally helpless against a tail-on approach, though, as they can adjust their escape performance based on the reaction distance.<ref name="Seamone">Seamone, S., Blaine, T., & Higham, T.E. (2014). "Sharks modulate their escape behavior in response to predator size, speed and approach orientation". ''Zoology'', 117(6), 377–382.</ref>

Rather than reacting at a greater distance and trying to swim away at a high sustained speed, blue sharks likely concentrate their [[energy]] on outmaneuvering predators with sharp turns and brief bursts of [[acceleration]].<ref name="Seamone"/>

==Relationship to humans==
[[File:Pamtu - blue shark meat on sale in Malta (cropped).jpg|thumb|Blue shark meat on sale in [[Malta]]]]
[[File:Blue shark, capture production, thousand tonnes, 1950-2022.svg|thumb|Global capture production of Blue shark (''Prionace glauca'') in thousand tonnes from 1950 to 2022, as reported by the [[Food and Agriculture Organization|FAO]]<ref>{{Cite web |title=Fisheries and Aquaculture – Global Production |url=https://www.fao.org/fishery/en/collection/global_production?lang=en |access-date=2024-05-06 |website=Food and Agriculture Organization of the United Nations (FAO)}}</ref>]]
Blue shark [[shark meat|meat]] is edible, but not widely sought after; it is consumed fresh, dried, smoked and salted and diverted for [[fishmeal]]. There is a report of high concentration of heavy metals ([[Mercury (element)|mercury]] and [[lead]]) in the edible flesh.<ref>{{cite journal|author=Lopez, S.|author2=Abarca, N.|author3=Meléndez, R.|title= Heavy Metal Concentrations of two highly migratory sharks (''Prionace glauca'' and ''Isurus oxyrinchus'') in the south-eastern Pacific waters: comments on public health and conservation|journal= Tropical Conservation Science |volume=6 |issue=1|pages= 126–137|year= 2014|url=https://tropicalconservationscience.mongabay.com/content/v6/TCS-2013_Vol_6(1)_126-137_Lopez_et_al.pdf|doi=10.1177/194008291300600103|doi-access=free}}</ref> The skin is used for [[leather]], the fins for [[shark-fin soup]] and the liver for oil.<ref name="FAO" /> Blue sharks are occasionally sought as [[game fish]] for their beauty and speed.

Blue sharks rarely bite humans. From 1580 up until 2013, the blue shark was implicated in only 13 biting incidents, four of which ended fatally.<ref>[https://www.flmnh.ufl.edu/fish/sharks/statistics/species3.htm Species Implicated in Attacks :: Florida Museum of Natural History]. Flmnh.ufl.edu. Retrieved on 2016-11-17.</ref>

===In captivity===
[[Image:A Blue shark at the Uminomori Aquarium in Sendai.jpg|thumb|right|A blue shark at the [[Sendai Umino-Mori Aquarium]], having lived for 367 days in captivity]]
[[Image:Prionace glauca in an aquarium.jpg|thumb|right|A blue shark at the [[Tokyo Sea Life Park]]]]
Blue sharks, like most [[Pelagic fish|pelagic sharks]], tend to fare poorly in captivity. The first attempt of keeping blue sharks in captivity was at [[Sea World San Diego]] in 1968,<ref name=Baylina2017>{{cite book| author1=Baylina |author2=Pereira |author3=Batista |author4=João Correia | title=Collection, transport and husbandry of the blue shark, Prionace glauca |editor=Smith |editor2=Warmolts |editor3=Thoney |editor4=Hueter |editor5=Murray |editor6=Ezcurra | year=2017 | series=Elasmobranch Husbandry Manual II | publisher=Special Publication of the Ohio Biological Survey | pages=43–52 | isbn=978-0-86727-166-9 }}</ref> and since then a small number of other [[public aquarium|public aquaria]] in North America, Europe and Asia have attempted it.<ref name=elasmollet>{{usurped|1=[https://web.archive.org/web/20131007000246/http://elasmollet.org/Pg/Pg_captive.html Blue Shark (''Prionace glauca'') in Captivity]}}. elasmollet.org (2007)</ref> Most of these were in captivity for about three months or less,<ref name=elasmollet/> and some of them were released back to the wild afterwards.<ref name=Baylina2017/> The record time for blue sharks in captivity is 246 and 224 days for two individuals at [[Tokyo Sea Life Park]],<ref name=Baylina2017/> 210 days for an individual at [[Adventure Aquarium|New Jersey Aquarium]],<ref name=elasmollet/> and 194 days for one at [[Lisbon Oceanarium]]<ref name=Baylina2017/> and 252 and 873 days for two individuals at [[Sendai Umino-Mori Aquarium]].<ref>{{Cite news|url= https://kahoku.news/articles/20170222kho000000027000c.html |title=<うみの杜水族館>ヨシキリザメ飼育 新記録|newspaper =[[河北新報]]|date=2016-06-24|access-date=30 April 2021}}</ref><ref>{{cite web|url=http://www.uminomori.jp/file/20201217yoshikiri_dqptrgpfckvtszhwmicfnyozsufufrlp.pdf|title=ヨシキリザメ死亡について|date=17 December 2020|access-date=17 December 2020|archive-date=14 March 2022|archive-url=https://web.archive.org/web/20220314205342/http://www.uminomori.jp/file/20201217yoshikiri_dqptrgpfckvtszhwmicfnyozsufufrlp.pdf}}</ref>

The blue shark that survived the longest in captivity was captured in [[Shizugawa, Miyagi|Shizugawa]] Bay on July 27, 2018, and taken to the Sendai Umino-Mori Aquarium.<ref name=uminomori>{{cite web|url=http://www.uminomori.jp/umino/blog/30144/index.html|title=ヨシキリザメ№25について 仙台うみの杜水族館公式サイト|date=24 January 2021|access-date=1 May 2021|archive-date=2 May 2021|archive-url=https://web.archive.org/web/20210502125520/http://www.uminomori.jp/umino/blog/30144/index.html}}</ref> The total length at the time of delivery was {{convert|51|cm|ft|abbr=on}}, the estimated weight was {{cvt|0.345|kg|lb}}, and the age was about 1 year old.<ref name=uminomori/> After that, it lived for 873 days, but died due to factors such as disordered swimming due to [[dehydration]].<ref name=uminomori/> At the time of death, the total length was {{convert|114|cm|ft|abbr=on}} and the weight was {{cvt|4|kg|lb}}.<ref name=uminomori/> This growth rate is said to be the same as that of wild blue sharks.<ref name=uminomori/>

Blue sharks are relatively easy to feed and store in captivity, and the three primary issues appear to be transport, predation by larger sharks and trouble avoiding smooth surfaces in tanks.<ref name=Baylina2017/> Small blue sharks, up to {{convert|1|m|ft|abbr=on}} long, are relatively easy to transport to aquaria, but it is much more complicated to transport larger individuals.<ref name=Baylina2017/> However, this typical small size when introduced to aquaria means that they are highly vulnerable to predation by other sharks that are often kept, such as [[Bull shark|bull]], [[Grey reef shark|grey reef]], [[Sandbar shark|sandbar]] and [[sand tiger shark]]s.<ref name=Baylina2017/><ref name=elasmollet/> For example, several blue sharks kept at Sea World San Diego initially did fairly well, but were eaten when bull sharks were added to their exhibit.<ref name=elasmollet/> Attempts of keeping blue sharks in tanks of various sizes, shapes and depths have shown that they have trouble avoiding walls, aquarium windows and other smooth surfaces, eventually leading to abrasions to the fins or snout, which may result in serious infections.<ref name=Baylina2017/><ref name=elasmollet/> To keep blue sharks, it is therefore necessary with tanks that allow for relatively long, optimum swimming paths where potential contact with smooth surfaces is kept at a minimum. It has been suggested that prominent rockwork may be easier to avoid for blue sharks than smooth surfaces, as has been shown in captive [[tiger shark]]s.<ref name=Baylina2017/>

==Conservation status==
Blue sharks make up approximately 85–90% of the total elasmobranchs caught by oceanic fisheries as bycatch.<ref>{{Cite journal |last1=da Silva |first1=Thaísy Emmanuelle Florentino |last2=Lessa |first2=Rosangela |last3=Santana |first3=Francisco Marcante |access-date=16 October 2024 |date=2021-01-21 |title=Current knowledge on biology, fishing and conservation of the blue shark (Prionace glauca) |url=https://neotropical.pensoft.net/article/58691/download/pdf/ |journal=Neotropical Biology and Conservation |volume=16 |issue=1 |pages=71–88 |doi=10.3897/neotropical.16.e58691 |bibcode=2021NeoBC..16...71D |doi-access=free |id={{ProQuest|<!-- add ProQuest data here -->}}}}</ref>
In June 2018 the New Zealand [[Department of Conservation (New Zealand)|Department of Conservation]] classified the blue shark as "Not Threatened" with the qualifier "Secure Overseas" under the [[New Zealand Threat Classification System]].<ref>{{Cite book|url=https://www.doc.govt.nz/globalassets/documents/science-and-technical/nztcs23entire.pdf|title=Conservation status of New Zealand chondrichthyans (chimaeras, sharks and rays), 2016|last1=Duffy|first1=Clinton A. J.|last2=Francis|first2=Malcolm|last3=Dunn|first3=M. R.|last4=Finucci|first4=Brit|last5=Ford|first5=Richard|last6=Hitchmough|first6=Rod|last7=Rolfe|first7=Jeremy|publisher=Department of Conservation|year=2018|isbn=978-1-988514-62-8|location=Wellington, New Zealand|pages=11|oclc=1042901090}}</ref> The species is listed as [[Near-threatened species|Near Threatened]] by the [[International Union for Conservation of Nature|IUCN]].<ref name="iucn">{{cite iucn |author=Rigby, C.L. |author2=Barreto, R. |author3=Carlson, J. |author4=Fernando, D. |author5=Fordham, S. |author6=Francis, M.P. |author7=Herman, K. |author8=Jabado, R.W. |author9=Liu, K.M. |author10=Marshall, A. |author11=Pacoureau, N. |author12=Romanov, E. |author13=Sherley, R.B. |author14=Winker, H. |year=2019 |title=Prionace glauca |article-number=e.T39381A2915850 |doi=10.2305/IUCN.UK.2019-3.RLTS.T39381A2915850.en}}</ref>

==See also==
{{Portal|Sharks}}
* [[Outline of sharks]]
* [[List of sharks]]
* [[List of prehistoric cartilaginous fish genera]]

==References==
{{Reflist|30em|refs=
<ref name=Scholz>{{cite journal
|last1=Scholz |first1=Tomáš |last2=Euzet |first2=Louis |last3=Moravec |first3=František
|year=1998
|title=Taxonomic status of ''Pelichnibothrium speciosum'' Monticelli, 1889 (Cestoda: Tetraphyllidea), a mysterious parasite of ''Alepisaurus ferox'' Lowe (Teleostei: Alepisauridae) and ''Prionace glauca'' (L.) (Euselachii: Carcharinidae)
|journal=Systematic Parasitology
|volume=41
|issue=1
|pages=1–8
|doi=10.1023/A:1006091102174
|s2cid=33831101 }}</ref>
}}

==External links==
{{Wikispecies|Prionace glauca}}
{{Commons}}
* {{ITIS |id=160424 |taxon=Prionace glauca |access-date=15 November 2005}}
* {{marinebio|id=35|name=Blue shark, Prionace glauca}}
* {{EOL | 2=Blue shark, Prionace glauca}}
* ARKive – [https://web.archive.org/web/20060422091248/http://www.arkive.org/species/GES/fish/Prionace_glauca/ Images and movies of the blue shark ''(Prionace glauca)'']
* [https://web.archive.org/web/20080922190644/http://www.marinebiodiversity.ca/shark/english/blue.htm Canadian Shark research laboratory]
* [https://www.bbc.co.uk/news/av/world-us-canada-10847838 BBCNews – 'Jaws' comes to a US beach] 3 August 2010.
* [https://www.bbc.co.uk/news/uk-wales-19182452 BBCNews – Footage of shark which closed New Quay (Wales) beach] 8 August 2012.
* [http://shark-references.com/species/view/Prionace-glauca Species Description of Prionace glauca at www.shark-references.com]
* {{sealifephotos|105801}}
* ''Prionace glauca'' discussed on [[Radio New Zealand|RNZ]] ''[[Critter of the Week]]'', [https://www.rnz.co.nz/national/programmes/afternoons/collections/critter-of-the-week 12 August 2022]

{{Selachimorpha|Ca.}}

{{Non-Endemic Marine Fish of New Zealand}}
{{Taxonbar|from=Q26337}}
{{Authority control}}

[[Category:Carcharhinidae|blue shark]]
[[Category:Viviparous fish]]
[[Category:Cosmopolitan fish]]
[[Category:Extant Pliocene first appearances]]
[[Category:Fish described in 1758|blue shark]]
[[Category:Animal taxa named by Carl Linnaeus|blue shark]]