Spinner shark
Encyclopedia
The spinner shark is a species of requiem shark
, family
Carcharhinidae, named for the spinning leaps it makes as a part of its feeding strategy. This species occurs in tropical and warm temperate waters worldwide, except for in the eastern Pacific Ocean
. It is found from coastal to offshore habitats to a depth of 100 m (330 ft), though it prefers shallow water. The spinner shark resembles a larger version of the blacktip shark
(C. limbatus), with a slender body, long snout, and black-marked fins. This species can be distinguished from the blacktip shark by the first dorsal fin
, which has a different shape and is placed further back, and by the black tip on the anal fin (in adults only). It attains a maximum length of 3 m (10 ft).
Spinner sharks are swift and gregarious predators that feed on a wide variety of small bony fishes and cephalopod
s. When feeding on schools
of forage fish
, they will speed vertically through the school while spinning on their axis, erupting from the water at the end. Like other members of its family, the spinner shark is viviparous, with females bearing litters of 3–20 young every other year. The newborns are born in shallow nursery areas near the coast, and are relatively fast-growing. This species is not usually dangerous to humans but may become belligerent when excited by food. Spinner sharks are valued by commercial fisheries
across their range for their meat, fins, liver oil
, and skin. They are also esteemed as strong fighters by recreational fishers
. The International Union for Conservation of Nature (IUCN) has assessed this species as Near Threatened
worldwide and Vulnerable
off the southeastern United States
.
and Friedrich Gustav Jakob Henle
in their 1839 Systematische Beschreibung der Plagiostomen, based on the mounted skin of a 79 cm (31 in) long specimen collected off Java
. This species was subsequently moved to the genera Aprion, Squalus, and Aprionodon before being placed within the genus Carcharhinus. The tooth shape and coloration of this species varies significantly with age and between geographical regions, which caused much taxonomic confusion. Other common names include blacktipped shark, great blacktip shark, inkytail shark, large blacktip shark, long-nose grey shark, longnose grey whaler, and smoothfang shark.
Based on similarities in morphology
, tooth shape, and behavior, the closest relatives of the spinner shark were originally believed to be the blacktip shark
and the graceful shark
(C. amblyrhynchoides). However, this interpretation was not supported by Gavin Naylor's 1992 allozyme
analysis, which suggested that these similarities are the product of convergent evolution
and that the closest relative of the spinner shark is the copper shark (C. brachyurus). In a 2007 ribosomal DNA
study by Mine Dosay-Akbulut, the spinner shark was found to be the most genetically divergent
of all the requiem shark species examined save for the tiger shark
(Galeocerdo cuvier), being less related to other Carcharhinus species than the lemon shark
(Negaprion brevirostris).
, it occurs from North Carolina
to the northern Gulf of Mexico
, including the Bahamas and Cuba
, and from southern Brazil
to Argentina
. In the eastern Atlantic, it occurs from off North Africa
to Namibia
. In the Indian Ocean
, it is found from South Africa
and Madagascar
, to the Red Sea
and the Gulf of Aden
, to India
and nearby islands, to Java
and Sumatra
. In the Pacific Ocean
it occurs off Japan
, Vietnam
, Australia
, and possibly the Philippines
. Parasitological evidence suggests that Indian Ocean spinner sharks have passed through the Suez Canal
into the Mediterranean Sea
, becoming Lessepsian migrants.
The spinner shark has been reported from ocean surface to a depth of 100 m (330 ft), though it prefers shallow water less than 30 m (100 ft) deep, and occupies all levels of the water column. This species may be found from coastal waters to well offshore, over continental and insular shelves. Juveniles have been known to enter bays but avoid brackish conditions. The northwest Atlantic subpopulation is known to be migratory
; in spring and summer they are found in warm inshore waters, and in winter they move south into deeper water.
The average spinner shark is 2 m (6.4 ft) long and weighs 56 kg (123 lbs); this species attains a maximum known length and weight of 3 m (10 ft) and 90 kg (198 lbs). Indo-Pacific sharks are generally larger than those from the northwest Atlantic. This species has a slim, streamlined body with a distinctive long, pointed snout. The eyes are small and circular. There are prominent forward-pointing furrows at the corners of the mouth. The tooth rows number 15–18 in each half of the upper jaw and 14–17 in each half of the lower jaw, with 2 and 1 tiny symphysial (central) teeth respectively. The teeth have long, narrow central cusps and are finely serrated in the upper jaw and smooth in the lower jaw. The five pairs of gill slit
s are long.
The first dorsal fin
is relatively small and usually originates behind the free rear tip of the pectoral fins. There is no ridge between the first and second dorsal fins. The pectoral fins are moderately short, narrow, and falcate (sickle-shaped). The body is densely covered with diamond-shaped dermal denticles with 7 (rarely 5) shallow horizontal ridges. The coloration is gray above, sometimes with a bronze sheen, and white below, with a faint white band on the sides. Young individuals have unmarked fins; the tips of the second dorsal fin, pectoral fins, anal fin, and lower caudal fin lobe (and sometimes the other fins as well) are black in larger individuals. The spinner shark differs from the blacktip shark in that its first dorsal fin is slightly more triangular in shape and is placed further back on the body. Adults can also be distinguished by the black tip on the anal fin.
, segregated by age and sex. Young individuals prefer cooler water temperatures than adults. Off South Africa, females are found close to shore year-round while males only appear during the summer. Smaller spinner sharks may be preyed upon by larger sharks. Known parasites of the spinner shark include the copepod
s Kroyeria deetsi, Nemesis pilosus, and N. atlantica, which infest the shark's gills, Alebion carchariae, which infests the skin, Nesippus orientalis, which infests the mouth and gill arches, and Perissopus dentatus, which infests the nares and the rear margins of the fins.
s, herring
, anchovies
, sea catfish
, lizardfish, mullet
s, bluefish
, tuna
s, bonito
, croakers
, jacks
, mojarra
s, and tongue-soles. They have also been known to eat stingray
s, cuttlefish
, squid
, and octopus
. Groups of spinner sharks are often found pursuing schools of prey at high speed. Individual prey are seized and swallowed whole, as this shark lacks cutting dentition
. This species employs an unusual tactic when feeding on schools of small fish: the shark charges vertically through the school, spinning on its axis with its mouth open and snapping all around it. The shark's momentum at the end of these spiraling runs often carries it into the air, giving it its common name. The blacktip shark also performs this behavior, though not as often. Off Madagascar, spinner sharks follow migrating schools of mackerel, tunas, and jacks. Like blacktip sharks, they congregate around shrimp
trawlers to feed on the discarded bycatch
, and may be incited into feeding frenzies
.
and two functional uterus
es; each uterus is divided into compartments, one for each embryo
. The embryos are initially sustained by a yolk sac
. When the embryo grows to around 19 cm (7.5 in) long, the supply of yolk has been exhausted and the empty yolk sac develops into a placenta
l connection through which the mother provides nutrients for the remainder of gestation
. This species has the smallest ova
relative to the fully developed embryo of any viviparous shark known. Females give birth to 3–20 (usually 7–11) pups every other year, after a gestation period of 11–15 months. Mating occurs from early spring to summer, and parturition in August off North Africa, from April to May off South Africa, and from March to April in the northwestern Atlantic. Young are birthed in coastal nursery areas such as bays, beaches, and high-salinity estuaries in water deeper than 5 m (20 ft).
The length at birth is 66–77 cm (26–30 in) in the northwestern Atlantic, 61–69 cm (24–27 in) off Tunisia, and 60 cm (24 in) off South Africa. Spinner sharks are relatively fast-growing sharks: 30 cm (12 in) per year for newborns, 25 cm (10 in) per year for one-year-olds, 10 cm (4 in) per year for adolescents, and 5 cm (2 in) per year for adults. In the northwestern Atlantic, males mature at 1.3 m (4.3 ft) long and females at 1.5–1.6 m (4.9–5.2 ft) long, corresponding to ages of 4–5 years and 7–8 years respectively. Off South Africa, males mature at 1.8 m (5.9 ft) and females at 2.1 m (6.9 ft). Spinner sharks generally do not reproduce until they are 12–14 years old. The maximum lifespan has been estimated at 15–20 years or more.
s as prey as their small, narrow teeth are adapted for grasping rather than cutting. However, they can become excited by the presence of food, and so caution is warranted if this species is encountered while spearfishing
. As of 2008, the International Shark Attack File
listed 16 unprovoked attacks and 1 provoked attack attributable to the spinner shark, none of them fatal.
The meat of the spinner shark is of high quality and sold fresh or dried and salted. In addition, the fins are used for shark fin soup
in East Asia
, the liver oil
is processed for vitamin
s, and the skin is made into leather
products. Spinner sharks are an important catch of the US commercial shark fisheries operating in the northwestern Atlantic and the Gulf of Mexico. The meat is marketed under the name "blacktip shark" in the United States, due to that species being considered superior in quality by consumers. It is likely also caught by other fisheries across its range, going unreported owing to confusion with the blacktip shark. The spinner shark is also highly regarded by recreational fishers, being described as a "spectacular fighter" that often leaps out of the water.
The International Union for Conservation of Nature (IUCN) has assessed the spinner shark as Near Threatened
worldwide and Vulnerable
in the northwest Atlantic; its frequent use of coastal habitats render it vulnerable to human exploitation and habitat degradation. The Northwest Atlantic fishery for this species is managed under the US National Marine Fisheries Service
(NMFS) 1999 Fishery Management Plan (FMP) for Atlantic Tunas, Swordfish and Sharks. For the purposes of commercial quotas and recreational bag limits, the spinner shark is categorized as a "Large Coastal Shark" (LCS).
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, named for the spinning leaps it makes as a part of its feeding strategy. This species occurs in tropical and warm temperate waters worldwide, except for in the eastern Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
. It is found from coastal to offshore habitats to a depth of 100 m (330 ft), though it prefers shallow water. The spinner shark resembles a larger version of the blacktip shark
Blacktip shark
The blacktip shark is a species of requiem shark, family Carcharhinidae. It is common to coastal tropical and subtropical waters around the world, including brackish habitats. Genetic analyses have revealed substantial variation within this species, with populations from the western Atlantic Ocean...
(C. limbatus), with a slender body, long snout, and black-marked fins. This species can be distinguished from the blacktip shark by the first dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
, which has a different shape and is placed further back, and by the black tip on the anal fin (in adults only). It attains a maximum length of 3 m (10 ft).
Spinner sharks are swift and gregarious predators that feed on a wide variety of small bony fishes and cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...
s. When feeding on schools
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...
of forage fish
Forage fish
Forage fish, also called prey fish or bait fish, are small fish which are preyed on by larger predators for food. Predators include other larger fish, seabirds and marine mammals. Typical ocean forage fish feed near the base of the food chain on plankton, often by filter feeding...
, they will speed vertically through the school while spinning on their axis, erupting from the water at the end. Like other members of its family, the spinner shark is viviparous, with females bearing litters of 3–20 young every other year. The newborns are born in shallow nursery areas near the coast, and are relatively fast-growing. This species is not usually dangerous to humans but may become belligerent when excited by food. Spinner sharks are valued by commercial fisheries
Commercial fishing
Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often pursue fish far into the ocean under adverse conditions...
across their range for their meat, fins, liver oil
Shark liver oil
Shark liver oil is obtained from sharks that are caught for food purposes and are living in cold, deep oceans. The liver oil from sharks has been used by fishermen for centuries as a folk remedy for general health...
, and skin. They are also esteemed as strong fighters by recreational fishers
Recreational fishing
Recreational fishing, also called sport fishing, is fishing for pleasure or competition. It can be contrasted with commercial fishing, which is fishing for profit, or subsistence fishing, which is fishing for survival....
. The International Union for Conservation of Nature (IUCN) has assessed this species as Near Threatened
Near Threatened
Near Threatened is a conservation status assigned to species or lower taxa that may be considered threatened with extinction in the near future, although it does not currently qualify for the threatened status...
worldwide and Vulnerable
Vulnerable species
On 30 January 2010, the IUCN Red List of Threatened Species identified 9694 Vulnerable species, subspecies and varieties, stocks and sub-populations.-References:...
off the southeastern United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
.
Taxonomy and phylogeny
The spinner shark was originally described as Carcharias (Aprion) brevipinna by Johannes Peter MüllerJohannes Peter Müller
Johannes Peter Müller , was a German physiologist, comparative anatomist, and ichthyologist not only known for his discoveries but also for his ability to synthesize knowledge.-Early years and education:...
and Friedrich Gustav Jakob Henle
Friedrich Gustav Jakob Henle
Friedrich Gustav Jakob Henle was a German physician, pathologist and anatomist. He is credited with the discovery of the loop of Henle in the kidney. His essay "On Miasma and Contagia" was an early argument for the germ theory of disease...
in their 1839 Systematische Beschreibung der Plagiostomen, based on the mounted skin of a 79 cm (31 in) long specimen collected off Java
Java
Java is an island of Indonesia. With a population of 135 million , it is the world's most populous island, and one of the most densely populated regions in the world. It is home to 60% of Indonesia's population. The Indonesian capital city, Jakarta, is in west Java...
. This species was subsequently moved to the genera Aprion, Squalus, and Aprionodon before being placed within the genus Carcharhinus. The tooth shape and coloration of this species varies significantly with age and between geographical regions, which caused much taxonomic confusion. Other common names include blacktipped shark, great blacktip shark, inkytail shark, large blacktip shark, long-nose grey shark, longnose grey whaler, and smoothfang shark.
Based on similarities in morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
, tooth shape, and behavior, the closest relatives of the spinner shark were originally believed to be the blacktip shark
Blacktip shark
The blacktip shark is a species of requiem shark, family Carcharhinidae. It is common to coastal tropical and subtropical waters around the world, including brackish habitats. Genetic analyses have revealed substantial variation within this species, with populations from the western Atlantic Ocean...
and the graceful shark
Graceful shark
The graceful shark or Queensland shark is a species of requiem shark, family Carcharhinidae, found in the tropical Indo-Pacific from the Gulf of Aden to northern Australia. It is a midwater species that has been recorded to a depth of...
(C. amblyrhynchoides). However, this interpretation was not supported by Gavin Naylor's 1992 allozyme
Allozyme
Variant forms of an enzyme that are coded by different alleles at the same locus are called allozymes. These are opposed to isozymes, which are enzymes that perform the same function, but which are coded by genes located at different loci....
analysis, which suggested that these similarities are the product of convergent evolution
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...
and that the closest relative of the spinner shark is the copper shark (C. brachyurus). In a 2007 ribosomal DNA
Ribosomal DNA
Ribosomal DNA codes for ribosomal RNA. The ribosome is an intracellular macromolecule that produces proteins or polypeptide chains. The ribosome itself consists of a composite of proteins and RNA. As shown in the figure, rDNA consists of a tandem repeat of a unit segment, an operon, composed of...
study by Mine Dosay-Akbulut, the spinner shark was found to be the most genetically divergent
Genetic divergence
Genetic divergence is the process in which two or more populations of an ancestral species accumulate independent genetic changes through time, often after the populations have become reproductively isolated for some period of time...
of all the requiem shark species examined save for 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...
(Galeocerdo cuvier), being less related to other Carcharhinus species than the lemon shark
Lemon shark
The lemon shark, Negaprion brevirostris, is a shark in the family Carcharhinidae, that can grow to long. It is known as the lemon shark because, at certain depths, light interacting with the local seawater can give this shark a tanned and yellow pitted appearance, much like the surface of a...
(Negaprion brevirostris).
Distribution and habitat
Some uncertainty exists in the distribution data for the spinner shark due to confusion with the blacktip shark. In the western Atlantic OceanAtlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
, it occurs from North Carolina
North Carolina
North Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte...
to the northern Gulf of Mexico
Gulf of Mexico
The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...
, including the Bahamas and Cuba
Cuba
The Republic of Cuba is an island nation in the Caribbean. The nation of Cuba consists of the main island of Cuba, the Isla de la Juventud, and several archipelagos. Havana is the largest city in Cuba and the country's capital. Santiago de Cuba is the second largest city...
, and from southern Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
to Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
. In the eastern Atlantic, it occurs from off North Africa
North Africa
North Africa or Northern Africa is the northernmost region of the African continent, linked by the Sahara to Sub-Saharan Africa. Geopolitically, the United Nations definition of Northern Africa includes eight countries or territories; Algeria, Egypt, Libya, Morocco, South Sudan, Sudan, Tunisia, and...
to Namibia
Namibia
Namibia, officially the Republic of Namibia , is a country in southern Africa whose western border is the Atlantic Ocean. It shares land borders with Angola and Zambia to the north, Botswana to the east and South Africa to the south and east. It gained independence from South Africa on 21 March...
. In the Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
, it is found from South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
and Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
, to the Red Sea
Red Sea
The Red Sea is a seawater inlet of the Indian Ocean, lying between Africa and Asia. The connection to the ocean is in the south through the Bab el Mandeb strait and the Gulf of Aden. In the north, there is the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez...
and the Gulf of Aden
Gulf of Aden
The Gulf of Aden is located in the Arabian Sea between Yemen, on the south coast of the Arabian Peninsula, and Somalia in the Horn of Africa. In the northwest, it connects with the Red Sea through the Bab-el-Mandeb strait, which is about 20 miles wide....
, to India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
and nearby islands, to Java
Java
Java is an island of Indonesia. With a population of 135 million , it is the world's most populous island, and one of the most densely populated regions in the world. It is home to 60% of Indonesia's population. The Indonesian capital city, Jakarta, is in west Java...
and Sumatra
Sumatra
Sumatra is an island in western Indonesia, westernmost of the Sunda Islands. It is the largest island entirely in Indonesia , and the sixth largest island in the world at 473,481 km2 with a population of 50,365,538...
. In the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
it occurs off Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...
, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, and possibly the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
. Parasitological evidence suggests that Indian Ocean spinner sharks have passed through the Suez Canal
Suez Canal
The Suez Canal , also known by the nickname "The Highway to India", is an artificial sea-level waterway in Egypt, connecting the Mediterranean Sea and the Red Sea. Opened in November 1869 after 10 years of construction work, it allows water transportation between Europe and Asia without navigation...
into the Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
, becoming Lessepsian migrants.
The spinner shark has been reported from ocean surface to a depth of 100 m (330 ft), though it prefers shallow water less than 30 m (100 ft) deep, and occupies all levels of the water column. This species may be found from coastal waters to well offshore, over continental and insular shelves. Juveniles have been known to enter bays but avoid brackish conditions. The northwest Atlantic subpopulation is known to be migratory
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...
; in spring and summer they are found in warm inshore waters, and in winter they move south into deeper water.
Description
Gill slit
Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of Cartilaginous fish such as sharks, rays, sawfish, and guitarfish. Most of these have five pairs, but a few species have 6 or 7 pairs...
s are long.
The first dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
is relatively small and usually originates behind the free rear tip of the pectoral fins. There is no ridge between the first and second dorsal fins. The pectoral fins are moderately short, narrow, and falcate (sickle-shaped). The body is densely covered with diamond-shaped dermal denticles with 7 (rarely 5) shallow horizontal ridges. The coloration is gray above, sometimes with a bronze sheen, and white below, with a faint white band on the sides. Young individuals have unmarked fins; the tips of the second dorsal fin, pectoral fins, anal fin, and lower caudal fin lobe (and sometimes the other fins as well) are black in larger individuals. The spinner shark differs from the blacktip shark in that its first dorsal fin is slightly more triangular in shape and is placed further back on the body. Adults can also be distinguished by the black tip on the anal fin.
Biology and ecology
The spinner shark is a fast, active swimmer that sometimes forms large schoolsShoaling 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 age and sex. Young individuals prefer cooler water temperatures than adults. Off South Africa, females are found close to shore year-round while males only appear during the summer. Smaller spinner sharks may be preyed upon by larger sharks. Known parasites of the spinner shark include the copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s Kroyeria deetsi, Nemesis pilosus, and N. atlantica, which infest the shark's gills, Alebion carchariae, which infests the skin, Nesippus orientalis, which infests the mouth and gill arches, and Perissopus dentatus, which infests the nares and the rear margins of the fins.
Feeding
Spinner sharks feed primarily on small bony fishes, including tenpounders, sardineSardine
Sardines, or pilchards, are several types of small, oily fish related to herrings, family Clupeidae. Sardines are named after the Mediterranean island of Sardinia, around which they were once abundant....
s, herring
Herring
Herring is an oily fish of the genus Clupea, found in the shallow, temperate waters of the North Pacific and the North Atlantic oceans, including the Baltic Sea. Three species of Clupea are recognized. The main taxa, the Atlantic herring and the Pacific herring may each be divided into subspecies...
, anchovies
Anchovy
Anchovies are a family of small, common salt-water forage fish. There are 144 species in 17 genera, found in the Atlantic, Indian, and Pacific Oceans. Anchovies are usually classified as an oily fish.-Description:...
, sea catfish
Ariidae
The Ariidae or ariid catfish are a family of catfish that mainly live in marine waters with many freshwater and brackish water species. They are found worldwide in tropical to warm temperate zones.-Taxonomy:...
, lizardfish, mullet
Mullet (fish)
The mullets or grey mullets are a family and order of ray-finned fish found worldwide in coastal temperate and tropical waters, and in some species in fresh water. Mullets have served as an important source of food in Mediterranean Europe since Roman times...
s, bluefish
Bluefish
The bluefish , called tailor in Australia, is a species of popular marine gamefish found in all climates. It is the sole species of the Pomatomidae family....
, 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...
s, bonito
Bonito
Bonito is a name given to various species of medium-sized, predatory fish in the Scombridae family. First, bonito most commonly refers to species in the genus Sarda, including the Atlantic bonito and the Pacific bonito ; second, in Japanese cuisine, bonito refers to the skipjack tuna , which, in...
, croakers
Sciaenidae
Sciaenidae is a family of fish commonly called drums, croakers, or hardheads for the repetitive throbbing or drumming sounds they make...
, jacks
Carangidae
Carangidae is a family of fish which includes the jacks, pompanos, jack mackerels, and scads.They are marine fish found in the Atlantic, Indian and Pacific Oceans...
, mojarra
Mojarra
The mojarras are a family, Gerreidae, of fishes in the order Perciformes. It has seven genera.Mojarras are a common prey and bait fish in many parts of the Caribbean including the South American Coast and Caribbean islands. These species tend to be difficult to identify in the field and often...
s, and tongue-soles. They have also been known to eat stingray
Stingray
The stingrays are a group of rays, which are cartilaginous fishes related to sharks. They are classified in the suborder Myliobatoidei of the order Myliobatiformes, and consist of eight families: Hexatrygonidae , Plesiobatidae , Urolophidae , Urotrygonidae , Dasyatidae , Potamotrygonidae The...
s, 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....
, 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...
, and 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...
. Groups of spinner sharks are often found pursuing schools of prey at high speed. Individual prey are seized and swallowed whole, as this shark lacks cutting dentition
Dentition
Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, the characteristic arrangement, kind, and number of teeth in a given species at a given age...
. This species employs an unusual tactic when feeding on schools of small fish: the shark charges vertically through the school, spinning on its axis with its mouth open and snapping all around it. The shark's momentum at the end of these spiraling runs often carries it into the air, giving it its common name. The blacktip shark also performs this behavior, though not as often. Off Madagascar, spinner sharks follow migrating schools of mackerel, tunas, and jacks. Like blacktip sharks, they congregate around 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...
trawlers to feed on the discarded bycatch
Bycatch
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...
, and may be incited into feeding frenzies
Feeding frenzy
In ecology, a feeding frenzy is a situation where oversaturation of a supply of food leads to rapid feeding by predatory animals. For example, a large school of fish can cause nearby sharks to enter a feeding frenzy. This can cause the sharks to go wild, biting anything that moves, including each...
.
Life history
Like other requiem sharks, the spinner shark is viviparous. Adult females have a single functional ovaryOvary
The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands.-Human anatomy:Ovaries...
and two functional uterus
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
es; each uterus is divided into compartments, one for each embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
. The embryos are initially sustained by a yolk sac
Yolk sac
The yolk sac is a membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals...
. When the embryo grows to around 19 cm (7.5 in) long, the supply of yolk has been exhausted and the empty yolk sac develops into a placenta
Placenta
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...
l connection through which the mother provides nutrients for the remainder of gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....
. This species has the smallest ova
Ovum
An ovum is a haploid female reproductive cell or gamete. Both animals and embryophytes have ova. The term ovule is used for the young ovum of an animal, as well as the plant structure that carries the female gametophyte and egg cell and develops into a seed after fertilization...
relative to the fully developed embryo of any viviparous shark known. Females give birth to 3–20 (usually 7–11) pups every other year, after a gestation period of 11–15 months. Mating occurs from early spring to summer, and parturition in August off North Africa, from April to May off South Africa, and from March to April in the northwestern Atlantic. Young are birthed in coastal nursery areas such as bays, beaches, and high-salinity estuaries in water deeper than 5 m (20 ft).
The length at birth is 66–77 cm (26–30 in) in the northwestern Atlantic, 61–69 cm (24–27 in) off Tunisia, and 60 cm (24 in) off South Africa. Spinner sharks are relatively fast-growing sharks: 30 cm (12 in) per year for newborns, 25 cm (10 in) per year for one-year-olds, 10 cm (4 in) per year for adolescents, and 5 cm (2 in) per year for adults. In the northwestern Atlantic, males mature at 1.3 m (4.3 ft) long and females at 1.5–1.6 m (4.9–5.2 ft) long, corresponding to ages of 4–5 years and 7–8 years respectively. Off South Africa, males mature at 1.8 m (5.9 ft) and females at 2.1 m (6.9 ft). Spinner sharks generally do not reproduce until they are 12–14 years old. The maximum lifespan has been estimated at 15–20 years or more.
Human interactions
Ordinarily, spinner sharks do not pose a substantial danger to humans; they do not perceive large mammalMammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s as prey as their small, narrow teeth are adapted for grasping rather than cutting. However, they can become excited by the presence of food, and so caution is warranted if this species is encountered while spearfishing
Spearfishing
Spearfishing is an ancient method of fishing that has been used throughout the world for millennia. Early civilizations were familiar with the custom of spearing fish from rivers and streams using sharpened sticks....
. As of 2008, the International Shark Attack File
International Shark Attack File
The International Shark Attack File is a global database of shark attacks. It began as an attempt to catalogue shark attacks on servicemen during World War II. The Office of Naval Research funded it from 1958 until 1968. During that time a panel of shark experts developed a standard system for...
listed 16 unprovoked attacks and 1 provoked attack attributable to the spinner shark, none of them fatal.
The meat of the spinner shark is of high quality and sold fresh or dried and salted. In addition, the fins are used for shark fin soup
Shark fin soup
Shark fin soup is a popular soup item of Chinese cuisine usually served at special occasions such as weddings and banquets, or as a luxury item in Chinese culture. The shark fins provide texture while the taste comes from the other soup ingredients.There is controversy over the practice of shark...
in East Asia
East Asia
East Asia or Eastern Asia is a subregion of Asia that can be defined in either geographical or cultural terms...
, the liver oil
Shark liver oil
Shark liver oil is obtained from sharks that are caught for food purposes and are living in cold, deep oceans. The liver oil from sharks has been used by fishermen for centuries as a folk remedy for general health...
is processed for vitamin
Vitamin
A vitamin is an organic compound required as a nutrient in tiny amounts by an organism. In other words, an organic chemical compound is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on...
s, and the skin is made into 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:...
products. Spinner sharks are an important catch of the US commercial shark fisheries operating in the northwestern Atlantic and the Gulf of Mexico. The meat is marketed under the name "blacktip shark" in the United States, due to that species being considered superior in quality by consumers. It is likely also caught by other fisheries across its range, going unreported owing to confusion with the blacktip shark. The spinner shark is also highly regarded by recreational fishers, being described as a "spectacular fighter" that often leaps out of the water.
The International Union for Conservation of Nature (IUCN) has assessed the spinner shark as Near Threatened
Near Threatened
Near Threatened is a conservation status assigned to species or lower taxa that may be considered threatened with extinction in the near future, although it does not currently qualify for the threatened status...
worldwide and Vulnerable
Vulnerable species
On 30 January 2010, the IUCN Red List of Threatened Species identified 9694 Vulnerable species, subspecies and varieties, stocks and sub-populations.-References:...
in the northwest Atlantic; its frequent use of coastal habitats render it vulnerable to human exploitation and habitat degradation. The Northwest Atlantic fishery for this species is managed under the US National Marine Fisheries Service
National Marine Fisheries Service
The National Marine Fisheries Service is a United States federal agency. A division of the National Oceanic and Atmospheric Administration and the Department of Commerce, NMFS is responsible for the stewardship and management of the nation's living marine resources and their habitat within the...
(NMFS) 1999 Fishery Management Plan (FMP) for Atlantic Tunas, Swordfish and Sharks. For the purposes of commercial quotas and recreational bag limits, the spinner shark is categorized as a "Large Coastal Shark" (LCS).
External links
- Spinner shark (Carcharhinus brevipinna) at FishBase
- Spinner shark (Carcharhinus brevipinna) at IUCN Red List
- Spinner shark (Carcharhinus brevipinna) at Florida Museum of Natural History Ichthyology Department
- Spinner shark (Carcharhinus brevipinna) at MarineBio.org
- Chicago Tribune video - Spinner shark jumps over surfer