Blue shark
Encyclopedia
The blue shark is a species
of requiem shark
, family
Carcharhinidae, that inhabits deep waters in the world's temperate
and tropical oceans. Preferring cooler waters, blue sharks migrate
long distances, for example from New England
to South America
. Although generally lethargic, they can move very quickly. Blue sharks are viviparous and are noted for large litters of 25 to over 100 pup
s. They feed primarily on small fish
and squid
, although they can take larger prey. Blue sharks often school
segregated by sex and size, and this behavior has led to their nickname "wolves of the sea".
, delivering 4 to 135 pups per litter. The gestation period is between 9 and 12 months. Females mature at 5 to 6 years of age and males at 4 to 5. Courtship is believed to involve biting by the male, as mature specimens can be accurately sexed according to the presence or absence of bite scarring. Female blue sharks have adapted to the rigorous mating ritual by developing skin 3 times thicker than male skin.
and tropical waters from the surface to about 350 meters. 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 20°
and 50° North
but with strong seasonal fluctuations. In the tropics it spreads evenly between 20° N
and 20° S
. It prefers waters with a temperature range of 7–16 °C (44.6–60.8 F) but will tolerate temperatures of 21 °C (69.8 °F) or above. Records from the Atlantic show a regular clockwise migration within the prevailing currents.
are important prey for blue sharks, but their diet includes other invertebrates such as cuttlefish
and pelagic octopus
es, as well as lobster
, shrimp
, crab
, a large number of bony fishes, small sharks, mammalian carrion and occasional sea birds. 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. Blue sharks rarely eat tuna
.
on a regular basis, except by humans. Young and smaller individuals may get eaten by any sufficiently larger sharks such as the Great White Shark
and the Tiger Shark
. However, they are host to several species of parasites. For example, the blue shark is the definite host of the tetraphyllidea
n tapeworm, Pelichnibothrium speciosum (Prionacestus bipartitus). They become infected by eating intermediate hosts, probably Opah
, (Lampris guttatus), and/or longnose lancetfish, (Alepisaurus ferox).
. It is estimated that 10 to 20 million individuals are killed each year as a result of fishing. The flesh is edible, but not widely sought after; it is consumed fresh, dried, smoked and salted and diverted for fishmeal. The skin is used for leather
, the fins for shark-fin soup and the liver for oil. Blue sharks are occasionally sought as game fish
for their beauty and speed.
Blue sharks are not considered an aggressive species and rarely attack humans. Most interactions take place in deep water and on small boats as they rarely venture close to shore. As of 2009 there have been 13 attacks on humans and 4 fatalities.
s were added to the tank; the bulls ate the blues. The captivity record for blue sharks as of 2008 was held by The New Jersey
Aquarium for a specimen that lasted roughly 7 months before expiring of an apparent bacterial infection.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of requiem shark
Requiem shark
Requiem sharks are a family, Carcharhinidae, of sharks in the order Carcharhiniformes, containing migratory, live-bearing sharks of warm seas such as the tiger shark, the blue shark, the bull shark, and the milk shark.The name may be related to the French word for shark, "requin", itself of...
, family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Carcharhinidae, that inhabits deep waters in the world's temperate
Temperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...
and tropical oceans. Preferring cooler waters, blue sharks migrate
Fish migration
Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousands of kilometres...
long distances, for example from New England
New England
New England is a region in the northeastern corner of the United States consisting of the six states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut...
to South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
. Although generally lethargic, they can move very quickly. Blue sharks are viviparous and are noted for large litters of 25 to over 100 pup
Pup
Pup may refer to:In zoology:*Puppies, younger dogs*Pinniped young*Shark young*Rodent youngIn other uses:* Sopwith Pup, an aircraft used by the British in World War I* Beagle Pup, a 1960s British light aircraft...
s. They feed primarily on small fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
and squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
, although they can take larger prey. Blue sharks often school
Shoaling and schooling
In biology, any group of fish that stay together for social reasons are said to be shoaling , and if, in addition, the group is swimming in the same direction in a coordinated manner, they are said to be schooling . In common usage, the terms are sometimes used rather loosely...
segregated by sex and size, and this behavior has led to their nickname "wolves of the sea".
Anatomy and appearance
Blue sharks are light-bodied with long pectoral fins. The top of the body is deep blue, lighter on the sides, and the underside is white. It grows to 3.8 meters (12.5 ft) long and can weigh up to 204 kilograms (449.7 lb). The highest reported weight was 391 kilograms (862 lb).Reproduction
They are viviparous, with a yolk-sac placentaPlacenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...
, delivering 4 to 135 pups per litter. The gestation period is between 9 and 12 months. Females mature at 5 to 6 years of age and males at 4 to 5. Courtship is believed to involve biting by the male, as mature specimens can be accurately sexed according to the presence or absence of bite scarring. Female blue sharks have adapted to the rigorous mating ritual by developing skin 3 times thicker than male skin.
Range and habitat
The blue shark is the most widely distributed animal in the world. It is an oceanic and epipelagic shark found worldwide in deep temperateTemperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...
and tropical waters from the surface to about 350 meters. 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
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
and as far south as Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
. Blue sharks are found off the coasts of every continent, except Antarctica. Its greatest Pacific concentrations occur between 20°
20th parallel north
The 20th parallel north is a circle of latitude that is 20 degrees north of the Earth's equatorial plane. It crosses Africa, Asia, the Indian Ocean, the Pacific Ocean, North America, the Caribbean and the Atlantic Ocean....
and 50° North
50th parallel north
The 50th parallel north is a circle of latitude that is 50 degrees north of the Earth's equatorial plane. It crosses Europe, Asia, the Pacific Ocean, North America, and the Atlantic Ocean....
but with strong seasonal fluctuations. In the tropics it spreads evenly between 20° N
20th parallel north
The 20th parallel north is a circle of latitude that is 20 degrees north of the Earth's equatorial plane. It crosses Africa, Asia, the Indian Ocean, the Pacific Ocean, North America, the Caribbean and the Atlantic Ocean....
and 20° S
20th parallel south
The 20th parallel south is a circle of latitude that is 20 degrees south of the Earth's equatorial plane. It crosses the Atlantic Ocean, Africa, the Indian Ocean, Australasia, the Pacific Ocean and South America....
. It prefers waters with a temperature range of 7–16 °C (44.6–60.8 F) but will tolerate temperatures of 21 °C (69.8 °F) or above. Records from the Atlantic show a regular clockwise migration within the prevailing currents.
Feeding
SquidSquid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
are important prey for blue sharks, but their diet includes other invertebrates such as cuttlefish
Cuttlefish
Cuttlefish are marine animals of the order Sepiida. They belong to the class Cephalopoda . Despite their name, cuttlefish are not fish but molluscs....
and pelagic octopus
Octopus
The octopus is a cephalopod mollusc of the order Octopoda. Octopuses have two eyes and four pairs of arms, and like other cephalopods they are bilaterally symmetric. An octopus has a hard beak, with its mouth at the center point of the arms...
es, as well as lobster
Lobster
Clawed lobsters comprise a family of large marine crustaceans. Highly prized as seafood, lobsters are economically important, and are often one of the most profitable commodities in coastal areas they populate.Though several groups of crustaceans are known as lobsters, the clawed lobsters are most...
, shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
, crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
, a large number of bony fishes, small sharks, mammalian carrion and occasional sea birds. Whale
Whale
Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga...
and porpoise blubber
Blubber
Blubber is a thick layer of vascularized adipose tissue found under the skin of all cetaceans, pinnipeds and sirenians.-Description:Lipid-rich, collagen fiber–laced blubber comprises the hypodermis and covers the whole body, except for parts of the appendages, strongly attached to the musculature...
and meat have been retrieved from the stomachs of captured specimens and they are known to take cod
Cod
Cod is the common name for genus Gadus, belonging to the family Gadidae, and is also used in the common name for various other fishes. Cod is a popular food with a mild flavor, low fat content and a dense, flaky white flesh. Cod livers are processed to make cod liver oil, an important source of...
from trawl nets. Blue sharks rarely eat tuna
Tuna
Tuna is a salt water fish from the family Scombridae, mostly in the genus Thunnus. Tuna are fast swimmers, and some species are capable of speeds of . Unlike most fish, which have white flesh, the muscle tissue of tuna ranges from pink to dark red. The red coloration derives from myoglobin, an...
.
Predators
Adult blue sharks do not suffer predationPredation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
on a regular basis, except by humans. Young and smaller individuals may get eaten by any sufficiently larger sharks such as the Great White Shark
Great white shark
The great white shark, scientific name Carcharodon carcharias, also known as the great white, white pointer, white shark, or white death, is a large lamniform shark found in coastal surface waters in all major oceans. It is known for its size, with the largest individuals known to have approached...
and the Tiger Shark
Tiger shark
The tiger sharks, Galeocerdo cuvier, is a species of requiem shark and the only member of the genus Galeocerdo. Commonly known as sea tigers, tiger sharks are relatively large macropredators, capable of attaining a length of over . It is found in many tropical and temperate waters, and is...
. However, they are host to several species of parasites. For example, the blue shark is the definite host of the tetraphyllidea
Tetraphyllidea
Tetraphyllidea is a large tapeworm order that contains some 60 genera and about 800 described species. Tetraphyllideans are remarkable for their scolex morphologies, which are the most varied and morphologically complex amongst all tapeworm orders....
n tapeworm, Pelichnibothrium speciosum (Prionacestus bipartitus). They become infected by eating intermediate hosts, probably Opah
Opah
Opah are large, colorful, deep-bodied pelagic Lampriform fish comprising the small family Lampridae . There are only two living species in a single genus: Lampris...
, (Lampris guttatus), and/or longnose lancetfish, (Alepisaurus ferox).
Relationship to humans
Blue sharks are the most heavily fished sharks mainly as by-catchBy-catch
The term “bycatch” is usually used for fish caught unintentionally in a fishery while intending to catch other fish. It may however also indicate untargeted catch in other forms of animal harvesting or collecting...
. It is estimated that 10 to 20 million individuals are killed each year as a result of fishing. The flesh is edible, but not widely sought after; it is consumed fresh, dried, smoked and salted and diverted for fishmeal. The skin is used for leather
Leather
Leather is a durable and flexible material created via the tanning of putrescible animal rawhide and skin, primarily cattlehide. It can be produced through different manufacturing processes, ranging from cottage industry to heavy industry.-Forms:...
, the fins for shark-fin soup and the liver for oil. Blue sharks are occasionally sought as game fish
Game fish
Game fish are fish pursued for sport by recreational anglers. They can be freshwater or marine fish. Game fish can be eaten after being caught, though increasingly anglers practise catch and release to improve fish populations. Some game fish are also targeted commercially, particularly...
for their beauty and speed.
Blue sharks are not considered an aggressive species and rarely attack humans. Most interactions take place in deep water and on small boats as they rarely venture close to shore. As of 2009 there have been 13 attacks on humans and 4 fatalities.
In captivity
Blue sharks, like most pelagic sharks, tend to fare poorly in captivity. Attempts at keeping them using circular tanks with long glide paths, and pools with 3 metres (9.8 ft) central depth gently ascending to zero depth have met with mixed results at best; most specimens last less than 30 days. As with other pelagic sharks, they seem to have trouble avoiding walls or other obstacles. In one case at Sea World San Diego, the blue did fairly well until bull sharkBull shark
The bull shark, Carcharhinus leucas, also known as Zambezi shark or unofficially known as Zambi in Africa and Nicaragua shark in Nicaragua, is a shark common worldwide in warm, shallow waters along coasts and in rivers...
s were added to the tank; the bulls ate the blues. The captivity record for blue sharks as of 2008 was held by The New Jersey
New Jersey
New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...
Aquarium for a specimen that lasted roughly 7 months before expiring of an apparent bacterial infection.