Prionace glauca

Blue sharks are viviparous, giving birth to live young after a gestation period of nine to twelve months (6) (7). Up to 135 pups can be born per litter, partially depending on the size of the female, but the average is 25 to 50 (5) (6). Maturity is reached at approximately five to six years old and blue sharks are known to have lived to 20 years (7). Although often observed cruising slowly and sluggishly the blue shark is capable of rapid movement if it is excited or feeding (6). This species will often circle its prey before moving in to attack it. Blue sharks primarily feed upon relatively small prey, such as bony fish and squid, but will also take larger prey including mammalian carrion (1).

The blue shark is easily identified by its beautifully coloured slender body, which is a deep indigo-blue across the back, shading to a vibrant blue on the sides, and paling to white underneath (4). This shark has large eyes, triangular teeth, a conical snout, long pectoral fins and a second dorsal fin much smaller than the first (2) (4). While its elongated caudal fin provides swimming power, its sleek, tapered body makes it a graceful mover (5).

  Common names: shark (English), tiburón (Espanol)
 
Prionace glauca (Linnaeus, 1758)

Blue shark

Very elongate and fusiform; snout long and narrowly rounded; no spiracles; eyes round, with nictitating membrane; teeth serrated, long and triangular, broader and curved on top jaw, center tooth of top jaw very large; 5 short gill slits, last 2 over pectoral base; 1st  dorsal fin low, its origin well behind pectoral fins; no ridge between dorsals; pectorals very long, narrow, slightly curved, pointed tips; tail base with small keel; tail asymmetric, well developed lower lobe, upper lobe notched under tip.

Back dark blue, flanks intense blue; belly white; tip of pectoral and anal dark.

Size: 380 cm.

Habitat: oceanic, epipelagic.

Depth: 0-350 m.

Southern California to the lower 2/3 of the Gulf of California and to Peru, and probably all the oceanic islands.   

Oceanic, but may be found close inshore where the continental shelf is narrow (Ref. 6871, 58302). Usually found to at least 150 m (Ref. 26938). Reported from estuaries (Ref. 26340). Epipelagic, occasionally occurs in littoral areas (Ref. 58302). Feeds on fishes (herring, silver hake, white hake, red hake, cod, haddock, pollock, mackerel, butterfish, sea raven and flounders (Ref. 5951)), small sharks, squids, pelagic red crabs, cetacean carrion, occasional sea birds and garbage (Ref. 5578). Viviparous (Ref. 50449). Sexual dimorphism occurs in skin thickness of maturing and adult females (Ref. 49562). May travel considerable distances (one specimen tagged in New Zealand was recaptured 1,200 km off the coast of Chile) (Ref. 26346). Potentially dangerous to humans (Ref. 6871, 13513). Marketed fresh, dried or salted, and frozen; meat utilized for consumption, hides for leather and fins for soup (Ref. 9987). Sexually mature at 250 cm long and 4-5 years old. The female gives birth up to 80 young measuring 40 cm long, gestation lasts almost a year (Ref. 35388). Produces from 4 to 135 young a litter (Ref. 26938).

 Blue sharks can grow up to 3.8 m long and are easily distinguished by their bright blue dorsal coloration and white underside. Generally, blue sharks have a slender body, long conical snout, long and narrow pectoral fins and a caudal fin with a long upper lobe.The blue shark is often seen cruising slowly at the surface, with its large pectoral fins outspread, and its first dorsal fin and terminal caudal lobe out of the water. It is a viviparous species and the number of young varies from 4 to 135 per litter, with a size at birth around 40 cm. The gestation period is from 9 to 12 months, and possible maximum longevity is around 20 years. Males mature around 180 to 200 cm and females around 220 cm in length.  

The blue shark feeds on relatively small prey, especially squid and bony fishes, though other invertebrates, small sharks, and mammalian carrion is readily taken and seabirds occasionally are caught at the surface of the water. Squid are a very important prey of the blue shark and some species form huge breeding aggregations, which are attended by blue sharks. Much of the prey of the blue shark is pelagic, though bottom fishes and invertebrates figure in its diet also.

 This common oceanic shark is usually caught with pelagic longlines but also pelagic trawls, and even bottom trawls near coasts.

Depth Range (m): 0 (S) - 350 (S)

See Map (including site records) of Distribution in the Tropical Eastern Pacific 
 
Global Endemism: All species, TEP non-endemic, Circumtropical ( Indian + Pacific + Atlantic Oceans), "Transpacific" (East + Central &/or West Pacific), All Pacific (West + Central + East), East Pacific + Atlantic (East +/or West), Transisthmian (East Pacific + Atlantic of Central America), East Pacific + all Atlantic (East+West)

Regional Endemism: All species, Eastern Pacific non-endemic, Tropical Eastern Pacific (TEP) non-endemic, Continent + Island (s), Continent, Island (s)

Residency: Resident

Climate Zone: North Temperate (Californian Province &/or Northern Gulf of California), Northern Subtropical (Cortez Province + Sinaloan Gap), Northern Tropical (Mexican Province to Nicaragua + Revillagigedos), Equatorial (Costa Rica to Ecuador + Galapagos, Clipperton, Cocos, Malpelo), South Temperate (Peruvian Province )

Newfoundland to Argentina

Blue sharks are one of the most wide ranging shark species and can be found in all major oceans (except the Arctic), as well as the Mediterranean Sea and in temperate and tropical pelagic waters.

Biogeographic Regions: indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native ); mediterranean sea (Native )

Other Geographic Terms: cosmopolitan

The Blue Shark is one of the most wide ranging of all sharks, being found throughout tropical and temperate seas from latitudes of about 60°N'50°S. It is oceanic and pelagic, found from the surface to about 350 m depth; occasionally it occurs close inshore where the continental shelf is narrow. The Blue Shark prefers temperatures of 12'20°C and is found at greater depths in tropical waters (Last and Stevens 1994).

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Circumglobal in temperate and tropical waters. Western Atlantic: Newfoundland, Canada to Argentina. Central Atlantic. Eastern Atlantic: Norway to South Africa, including the Mediterranean. Indo-West Pacific: East Africa to Indonesia, Japan, Australia, New Caledonia, and New Zealand. Eastern Pacific: Gulf of Alaska to Chile. Probably the widest ranging chondrichthyian. Highly migratory species, Annex I of the 1982 Convention on the Law of the Sea (Ref. 26139).

Circumglobal in tropical through temperate seas (including Mediterranean Sea, western Baltic Sea, North Sea, Seychelles, Madagascar, Mascarenes, Hawaiian Islands).

Cosmopolitan on the high seas in the warmer parts of all the oceans. Including in the western Atlantic: outer Nova Scotia and the banks of Newfoundland; in the eastern Atlantic: England and Scotland with some found at the Orkneys and southern Norway; Mediterranean.

Blue sharks are probably the most wide-ranging and (at least initially) one of the most abundant of all shark species, occurring in temperate and tropical waters from 50°N to 40°S around the globe (2). A migratory species, they periodically travel clockwise around the Atlantic, seemingly riding the Gulf Stream to Europe, taking various currents down the European and African coasts, and riding the Atlantic North Equatorial Current to the Caribbean region (1).

Length max (cm): 380.0 (S)

The striking coloration of blue sharks makes them one of the most distinctive species in the family Carcharhinidae (requiem or whaler sharks). The dorsum is a deep shade of indigo, while the flanks are a vibrant blue. The ventral surface fades to a light grey, exhibiting the typical pelagic countershaded coloration that deceives the eyes of bottom-dwelling prey or predators by blending in with light coming from the sun. The body is streamlined and thin, with an elongated heterocercal caudal (tail) fin, making it one of the fastest sharks in the ocean. The second dorsal fin is approximately half the size of the first, and the pectoral fins are proportionately longer than in most other shark species. The eyes are large, and the mouth is lined with several rows of triangular, serrated teeth; each tooth is usually replaced every 8 to 15 days. Blue sharks can reach 4 m in total length and weigh up to 240 kg.

Range mass: 240 (high) kg.

Range length: 4 (high) m.

Average length: 3.35 m.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: female larger

Dorsal spines (total): 0; Dorsal soft rays (total): 0; Analspines: 0; Analsoft rays: 0

Maximum size: 3850 mm TL

400 cm TL (male/unsexed; (Ref. 35388)); max. published weight: 205.9 kg (Ref. 40637); max. reported age: 20 years (Ref. 27347)

to 400.0cm TL; max. weight: 200 kg.

A slim, graceful blue shark with a long, conical snout, large eyes, and curved triangular upper teeth with saw edges; pectorals long and narrow; no interdorsal ridge (Ref. 5578). Dark blue dorsally, bright blue on the sides, white ventrally (Ref. 5578). Tips of pectoral fins and anal fin dusky (Ref. 9997).

Salinity: Marine, Marine Only

Inshore/Offshore: Offshore Only, Offshore

Water Column Position: Surface, Near Surface, Mid Water, Water column only

Habitat: Water column

FishBase Habitat: Pelagic

nektonic

Prefers waters if 7-16 C, often near surface.

Blue sharks inhabit the epipelagic and mesopelagic zones (from the surface to about 350 m in depth), in water temperatures ranging between 12 and 20°C. While they are mainly found in pelagic, open-ocean waters, they may sometimes be found closer to shore in the neritic zone, near the edge of continental shelves.

Range depth: 0 to 350 m.

Habitat Regions: temperate ; tropical ; saltwater or marine

Aquatic Biomes: pelagic

Habitat and Ecology

Systems

• Marine

Habitat Type: Marine

pelagic-oceanic; oceanodromous (Ref. 51243); marine; depth range 1 - 1000 m (Ref. 89422), usually 80 - 220 m (Ref. 55193)

Depth range based on 12253 specimens in 1 taxon.
Water temperature and chemistry ranges based on 11381 samples.

Environmental ranges
  Depth range (m): 0 - 4700
  Temperature range (°C): 1.478 - 27.155
  Nitrate (umol/L): 0.165 - 33.615
  Salinity (PPS): 30.381 - 36.430
  Oxygen (ml/l): 0.732 - 7.210
  Phosphate (umol/l): 0.147 - 2.618
  Silicate (umol/l): 1.436 - 80.155

Graphical representation

Depth range (m): 0 - 4700

Temperature range (°C): 1.478 - 27.155

Nitrate (umol/L): 0.165 - 33.615

Salinity (PPS): 30.381 - 36.430

Oxygen (ml/l): 0.732 - 7.210

Phosphate (umol/l): 0.147 - 2.618

Silicate (umol/l): 1.436 - 80.155
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

 The blue shark is probably the widest ranging shark found in the main oceans and seas of the world, from the surface to at least 400 m depth. Blue sharks are a migratory species.

Depth: 0 - 350m.
Recorded at 350 meters.

Habitat: pelagic. Blue shark.  (Linnaeus, 1758)  Brilliant bright blue above , white below. Vivaporous; the most fecund of all sharks with 35 -135 pups per litter; born at 50 cm; mature at 2,2 m; Attains 3,5 m.; Scavenger / predator; can be dangerous to man. The well known video footage of a shark attacking the chain clad arm of Valerie Taylor shows this shark. Widespread throughout all major oceans, favours waters with a temperature of 12-16 deg C. In tropical areas found offshore at some depth (80 - 220 m) but occurring close to shore and near surface in warm temperate areas.

Pelagic; marine; depth range to 350 m. Oceanic, but may be found close inshore where the continental shelf is narrow. Usually found to at least 150 m.

The blue shark is a pelagic species occurring in the open ocean near the surface, inhabiting slightly deeper, cooler waters when in tropical environments (4). Although typically an offshore species, the blue shark may venture inshore, especially at night (1).

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Oceanodromous. Migrating within oceans typically between spawning and different feeding areas, as tunas do. Migrations should be cyclical and predictable and cover more than 100 km.

Feeding Group: Carnivore

Diet: octopus/squid/cuttlefish, Pelagic crustacea, bony fishes, sharks/rays, sea snakes/mammals/turtles/birds

Blue sharks prey on up to 24 species of cephalopods and 16 species of fish. They primarily feed upon non-active, gelatinous, mesopelagic/bathypelagic cephalopods such as blanket octopus (genus Tremoctopus), bathyscaphoid squids (family Cranchiidae), and pelagic octopus (Ocythoe tuberculata). Prey also includes small schooling fishes, such as long-snouted lancetfish (Alepisaurus feroxe), snake mackerel (Gempylus serpens), and castor oil fish (Ruvettus pretiosus). During their reproductive migration cycles off of the coast of Brazil, blue sharks were found to have consumed seabirds, including great shearwaters (Puffinus gravis).

Animal Foods: birds; fish; mollusks

Primary Diet: carnivore (Piscivore , Molluscivore )

Found worldwide in tropical and temperate seas; a pelagic species, sometimes advancing into coastal waters (Ref. 9137). Occurs on the continental shelf (Ref. 75154). Prefer temperatures of 7-16°C; usually found in deeper waters in the tropics (Ref. 5951). A carnivore (Ref. 9137). Parasites of the species include: Hepatoxylon squali pleurocercoid, Phyllobothrium dagnallium, Phyllobothrium sp. and Platybothrium parvum (Ref. 5951).

Bony fishes, small sharks, squids, pelagic red crabs, cetacean carrion, occasional sea birds and garbage.

Blue sharks are top-level predators that help to regulate prey populations in the marine pelagic environment.

Pilotfish (Naucrates ductor) have a mutualistic symbiosis with blue sharks. They clean the shark's teeth and gills and removes any parasitic species that have attached themselves to the shark's skin. In return, pilotfish gain protection from predators and a ready source of food.

Many species of copepods are found on the gills and outer skin of blue sharks. Several tapeworm and one nematode species have been found in the stomach and spiral valve of blue sharks, resulting from consumption of infected fish that are the intermediate hosts of these parasites.

Mutualist Species:

• pilot fish (Naucrates ductor)

Commensal/Parasitic Species:

• Kroyeria carchariaeglauci (Subclass Copepoda, Subphylum Crustacea)
• Kroyeria lineata (Subclass Copepoda, Subphylum Crustacea)
• Pandarus floridanus (Subclass Copepoda, Subphylum Crustacea)
• Phyllothereus cornutus (Subclass Copepoda, Subphylum Crustacea)
• Echthrogaleus sp. (Subclass Copepoda, Subphylum Crustacea)
• Anisakis simplex (Family Anisakidae, Phylum Nematoda)
• Anthrobothrium laciniatum (Class Cestoda, Phylum Platyhelminthes)
• Pelichnibothrium speciosum (Class Cestoda, Phylum Platyhelminthes)
• Platybothrium auriculatum (Class Cestoda, Phylum Platyhelminthes)
• Prosobothrium armigerum (Class Cestoda, Phylum Platyhelminthes)

Aside from predation by humans for the lucrative shark fin trade, blue sharks are not frequently preyed upon. Occasional predators can include larger sharks such as shortfin makos Isurus paucus and great whites (Carcharodon carcharias), as well as killer whales Orcinus orca, while juveniles can also be taken by California sea lions (Zalophus californianus).

Due to their pelagic lifestyle, blue sharks exhibit countershading. The lighter coloration on the ventral surface helps to camouflage the sharks against the background of lighter-colored water when viewed from below. In contrast, the darker shades of blue and silver on the dorsal side allows them to blend in with the depths below when viewed from above. This countershading, along with a streamlined body shape, allows blue sharks to maneuver both swiftly and unnoticed as both predator and prey.

Known Predators:

• short fin mako sharks (Isurus paucus)
• great white sharks (Carcharodon carcharias)
• orcas (Orcinus orca)
• California sea lions (Zalophus californianus)
• humans (Homo sapiens)

Anti-predator Adaptations: cryptic

Primarily squids and fishes, including herring, silver hake, white hake, red hake, cod, haddock, pollock, mackerel, butterfish, sea raven and flounders

Most sharks are known to use body language to signal aggression, but there is little data available on whether sharks utilize other forms of communication between individuals. Like all sharks, blue sharks have highly developed senses of smell, sight, and touch. The lateral line is a sensory organ running down the length of their body that detects pressure waves from movements in the water, allowing the sharks to perceive movements of prey. They also possess electroreceptors called Ampullae of Lorenzini on the underside of the snout, which detect electrical fields generated by the muscle contractions of prey items.

Communication Channels: visual

Perception Channels: visual ; tactile ; acoustic ; vibrations ; chemical ; electric

After fertilization, embryos develop inside the female's uterus, nourished by a placenta-like yolk sac. Females give birth to fully-developed, live young. Blue sharks have one of the fastest growth rates of all sharks, growing up to 30 cm annually until maturity. Blue sharks are 35to 50 cm in length at birth, and will grow up to 400 cm (although the average length is 335 cm). Both sexes reach adulthood at about 220 cm in length. Juveniles usually stay in pupping areas of the sub-Arctic boundary (42°N North Pacific Ocean) until they reach maturity at 5 years of age.

Development - Life Cycle: indeterminate growth

Distinct pairing with embrace (Ref. 205). Viviparous (Ref. 26281), placental (Ref. 50449); 4-63 young in a litter (Ref. 9997); 4-135 (usually 15-30) pups (Ref.58048), about 35-44 cm at birth. Gestation period ranges from 9 to 12 months (Ref. 244).Sexual dimorphism is evident in skin thickness of maturing and adult females (Ref. 49562). Females have thicker skin layer than males of the same size (Ref. 49562).

Blue sharks in the wild have an average lifespan of 15 to 16 years. Blue shark life expectancy decreases to an average of 8 years when held in captivity, likely due to their inability to engage in their pelagic and migratory lifestyle.

Range lifespan
Status: wild: 20 (high) years.

Range lifespan
Status: captivity: 8 (high) years.

Average lifespan
Status: wild: 15 years.

Typical lifespan
Status: captivity: 8 (high) years.

Maximum longevity: 20 years (wild)

Egg Type: Live birth, No pelagic larva

Blue sharks congregate together on continental shelves during the summer. Mating begins when a male bites a female between her first and second dorsal fins. For this reason, the skin over most of a female's dorsum may be up to three times as thick as in males. Insemination occurs via insertion of one of the claspers into the female's urogenital opening. Pair bonding does not occur, and after mating, individuals separate.

Mating System: polygynandrous (promiscuous)

Males reach sexual maturity at 187 cm in length, while females become mature at 220 cm. It is not definitively known if females breed every year and deposited sperm may be stored within the female's oviductal gland for several months after mating. Once pregnant, females migrate north to birthing and pupping grounds in the sub-Arctic boundary. Gestation lasts from 9 to 12 months, and up to 130 pups in a litter have been documented, but 25 to 50 pups are born on average. Pups average 39 cm at birth. Unlike bony fish, sharks utilize internal fertilization. The male bites down and insert a clasper inside the female to transfer sperm. Females have thick skin to protect them from injury when the males bite them during mating. Blue sharks are viviparous.

Breeding interval: It is unknown whether female blue sharks breed annually, or less frequently.

Breeding season: In the northern Pacific, most births occur from December to April.

Range number of offspring: 25 to 130.

Range gestation period: 9 to 12 months.

Range age at sexual or reproductive maturity (female): 5 to 6 years.

Range age at sexual or reproductive maturity (male): 5 to 6 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); viviparous ; sperm-storing ; delayed fertilization

As in other viviparous species, female blue sharks provide nourishment and protection to their young as they develop. After birth, shark pups separate from their mother and have no further contact.

Parental Investment: female parental care ; pre-hatching/birth (Provisioning: Female, Protecting: Female)

Viviparous with up to 80 young in a litter but usually less. Pups are 35 - 45 cm TL at birth; gestation period 9 - 12 months.

IUCN Red List: Listed, Near threatened

CITES: Not listed

Although not usually a targeted species, blue sharks are caught as bycatch by longline and dragnet fishing fleets, and to a lesser extent by sport fishermen. International conservation projects have been implemented to decrease the harvest of pelagic sharks, including this species. In 1991, the Australian Government implemented legislation that banned Japanese longline fishing fleets from taking shark fins without their attendant carcasses. Canada issued a fishery management plan for shark species in 1995 that established catch limits of 250,000 kg for blue sharks, and implemented limitations on finning and gear use, licenses, areas and seasons, and bycatch limits. Management plans have been in place in the US since 1993. Proper licensing and commercial quota limits have been introduced, and finning has also been banned within the US Exclusive Economic Zone. However, exploitation by the shark finning industry has still decreased populations globally, and the IUCN lists this species as "Near Threatened".

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: near threatened

Year Assessed

Assessor/s

Reviewer/s

Contributor/s

Justification

Canada

Rounded National Status Rank: N4 - Apparently Secure

Rounded Global Status Rank: GNR - Not Yet Ranked

Classified as Lower Risk / Near Threatened (LR/nt) on the IUCN Red List (1).

Population Trend

Major Threats

Near Threatened (NT)

Although blue sharks are among the most abundant, widespread, fecund and faster growing of the sharks, they are one of the most heavily fished sharks in the world. With an estimated 10 to 20 million individuals caught and killed each year, there is concern not only about what this is doing to blue shark populations, but also about the effect the removal of such an important predator might be having on the oceanic ecosystem (1). Blue sharks are one of the most important species in the international shark fin trade. However, their meat, while eaten in a few countries, is not very popular (8). They are also an important angling species in some areas (1).

Conservation Actions

International obligations that regulate the fishing of sharks include the Code of Conduct for Responsible Fishing of the Food and Agriculture Organisation (FAO) of the United Nations, the International Plan of Action for Sharks (IPOA-SHARKS), the United Nations' Agreement on Straddling Stocks and Highly Migratory Species, and the Sustainable Fisheries Act. Although some countries have banned finning, there are no binding international treaties for the management of sharks, including the regulation or outlawing of finning (9). The blue shark is listed on Annex I of the 1982 Convention on the Law of the Sea (3), which stresses the need for international cooperation in the conservation, management and utilization of living aquatic resources, especially of migratory species. This does not, however, enforce any regulations (9). Fortunately, the blue shark is a prolific species with good rebound potential, and the abundance and wide distribution of this species offers a reasonable buffer against extinction (7).

Blue sharks are considered by commercial fishermen (particularly those of mackerel, pilchard, and salmon) to be a nuisance species, as they prey on target species and ruin nets by becoming entangled in them.

Due to their pelagic lifestyle, blue sharks are not often encountered by divers and swimmers. They are considered to be a dangerous species, however, with the International Shark Attack File recording a dozen confirmed, unprovoked attacks (4 fatal), and nearly two dozen additional, provoked attacks.

Negative Impacts: injures humans (bites or stings)

Although mainly caught indirectly as bycatch on long lines and in gill nets, blue sharks, like many shark species, are valued commercially for their fins, squalene (liver oil), skin, cartilage, and their teeth and jaws. Their meat is less valued because of its high ammonia content.

Positive Impacts: food ; body parts are source of valuable material

fisheries: minor commercial; gamefish: yes; price category: medium; price reliability: reliable: based on ex-vessel price for this species