Carcharhinus Melanopterus
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The blacktip reef shark (''Carcharhinus melanopterus'') is a
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
of
requiem shark Requiem sharks are sharks of the family Carcharhinidae in the order Carcharhiniformes. They are migratory, live-bearing sharks of warm seas (sometimes of brackish or fresh water) and include such species as the bull shark, lemon shark, blac ...
, in the
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Carcharhinidae, which can be easily identified by the prominent black tips on its fins (especially on the first
dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...
and its
caudal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...
). Among the most abundant sharks inhabiting the
tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...
coral reef A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in group ...
s of the
Indian Indian or Indians may refer to: Associated with India * of or related to India ** Indian people ** Indian diaspora ** Languages of India ** Indian English, a dialect of the English language ** Indian cuisine Associated with indigenous peoples o ...
and
Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...
s, this species prefers shallow, inshore waters. Its exposed first dorsal fin is a common sight in the region. The blacktip reef shark is usually found over reef ledges and sandy flats, though it has also been known to enter
brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...
and
freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...
environments. It typically attains a length of . Like other sharks, the females are larger than the males. The blacktip reef shark has extremely small home ranges and exhibits strong site fidelity, remaining within the same local area for up to several years at a time. It is an active
predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...
of small
bony fish Osteichthyes ( ; ), also known as osteichthyans or commonly referred to as the bony fish, is a Biodiversity, diverse clade of vertebrate animals that have endoskeletons primarily composed of bone tissue. They can be contrasted with the Chondricht ...
,
cephalopod A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...
s, and
crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...
s, and has also been known to feed on
sea snake Sea snakes, or coral reef snakes, are Elapidae, elapid snakes that inhabit Marine (ocean), marine environments for most or all of their lives. They belong to two subfamilies, Hydrophiinae and Sea krait, Laticaudinae. Hydrophiinae also includes ...
s and
seabird Seabirds (also known as marine birds) are birds that are adaptation, adapted to life within the marine ecosystem, marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent ...
s. Accounts of the blacktip reef shark's life history have been variable and sometimes contradictory, in part reflecting geographical differences within the species. Like other members of its family, this shark is
viviparous In animals, viviparity is development of the embryo inside the body of the mother, with the maternal circulation providing for the metabolic needs of the embryo's development, until the mother gives birth to a fully or partially developed juve ...
, with females giving birth to two to five young on a biennial, annual, or possibly biannual cycle. Reports of the
gestation period In mammals, pregnancy is the period of reproduction during which a female carries one or more live offspring from implantation in the uterus through gestation. It begins when a fertilized zygote implants in the female's uterus, and ends once i ...
range from 7–9, through 10–11, to possibly 16 months.
Mating In biology, mating is the pairing of either opposite-sex or hermaphroditic organisms for the purposes of sexual reproduction. ''Fertilization'' is the fusion of two gametes. '' Copulation'' is the union of the sex organs of two sexually repr ...
is preceded by the male following closely behind the female, likely attracted by her chemical signals. Newborn sharks are found further inshore and in shallower water than adults, frequently roaming in large groups over areas flooded by
high tide Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables ...
. Timid and skittish, the blacktip reef shark is difficult to approach and seldom poses a danger to humans unless roused by food. However, people wading through shallow water are at risk of having their legs mistakenly bitten. This shark is used for its meat, fins, and liver oil, but is not considered to be a commercially significant species. The
International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the stat ...
has assessed the blacktip reef shark as Vulnerable. Although the species as a whole remains widespread and relatively common,
overfishing Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing Fish stocks, fish stock), resu ...
of this slow-reproducing shark has led to its decline at a number of locales.


Taxonomy

French
naturalist Natural history is a domain of inquiry involving organisms, including animals, fungi, and plants, in their natural environment, leaning more towards observational than experimental methods of study. A person who studies natural history is cal ...
s
Jean René Constant Quoy Jean René Constant Quoy (10 November 1790 in Maillé, Vendée, Maillé – 4 July 1869 in Rochefort, Charente-Maritime, Rochefort) was a French naval surgeon, zoologist and anatomist. In 1806, he began his medical studies at the school of naval ...
and
Joseph Paul Gaimard Joseph Paul Gaimard (31 January 1793 – 10 December 1858) was a French naval surgeon and naturalist. Biography Gaimard was born at Saint-Zacharie on January 31, 1793. He studied medicine at the naval medical school in Toulon, subsequen ...
originally described the blacktip reef shark during the 1817–1820 exploratory voyage of the
corvette A corvette is a small warship. It is traditionally the smallest class of vessel considered to be a proper (or " rated") warship. The warship class above the corvette is that of the frigate, while the class below was historically that of the sloo ...
''Uranie''. In 1824, their account was published as part of ''Voyage autour du monde...sur les corvettes de S.M. l'Uranie et la Physicienne'',
Louis de Freycinet Louis Claude de Saulces de Freycinet (7 August 1779 – 18 August 1841) was a French Navy officer. He circumnavigated the Earth, and in 1811 published the first map to show a full outline of the coastline of Australia. Biography He was born at M ...
's 13-volume report on the voyage. The
type specimen In biology, a type is a particular wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...
was a -long juvenile male caught off the island of
Waigeo Waigeo is an island in the Southwest Papua province of eastern Indonesia. The island is also known as Amberi or Waigiu. It is the largest of the four main islands in the Raja Ampat Islands archipelago, between Halmahera and about to the nort ...
, west of
New Guinea New Guinea (; Hiri Motu: ''Niu Gini''; , fossilized , also known as Papua or historically ) is the List of islands by area, world's second-largest island, with an area of . Located in Melanesia in the southwestern Pacific Ocean, the island is ...
. Quoy and Gaimard chose the name ''Carcharias melanopterus'', from the Greek ''melas'' meaning "black" and ''pteron'' meaning "fin" or "wing", in reference to this shark's prominent fin markings. Subsequent authors moved the blacktip reef shark to the
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
''Carcharhinus''; in 1965 the
International Commission on Zoological Nomenclature The International Commission on Zoological Nomenclature (ICZN) is an organization dedicated to "achieving stability and sense in the scientific naming of animals". Founded in 1895, it currently comprises 26 commissioners from 20 countries. Orga ...
designated it as the
type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...
for the genus. In some earlier literature, the scientific name of this shark was mistakenly given as ''C. spallanzani'', now recognized as a
synonym A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...
of the spottail shark (''C. sorrah''). Other
common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often con ...
s for this species include blackfin reef shark, black-finned shark, blacktip shark, reef blacktip shark, and guliman.


Phylogeny

Like most other members of its genus, the
phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...
position of the blacktip reef shark remains indeterminate. Based on
morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...
,
Jack Garrick John Andrew Frank Garrick (24 March 1928 – 30 August 2018) was a New Zealand ichthyologist. Career Garrick specialised in elasmobranchs and published many books and articles about shark and ray biology. In 1982, he published a thorough taxonom ...
proposed in 1982 that the closest relative of the blacktip reef shark was the nervous shark (''C. cautus'').
Leonard Compagno Leonard Joseph Victor Compagno (1943-2024) was an international authority on shark taxonomy and the author of many scientific papers and books on the subject, best known of which is his 1984 catalogue of shark species produced for the Food and Agri ...
's 1988 morphological analysis suggested affinity not only between this species and the nervous shark, but also four other species, and could not resolve their relationships further. A 1998
allozyme Alloenzymes (or also called allozymes) are variant forms of an enzyme which differ structurally but not functionally from other allozymes coded for by different alleles at the same locus. These are opposed to isozymes, which are enzymes that p ...
analysis by Gavin Naylor again yielded ambiguous results, finding that the blacktip reef shark forms a
polytomy An internal node of a phylogenetic tree is described as a polytomy or multifurcation if (i) it is in a rooted tree and is linked to three or more child subtrees or (ii) it is in an unrooted tree and is attached to four or more branches. A tree ...
(irresolvable group) with 10 other ''Carcharhinus'' species.


Distribution and habitat

The blacktip reef shark is found throughout nearshore waters of the tropical and subtropical
Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...
. In the
Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), ...
, it occurs from
South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...
to the
Red Sea The Red Sea is a sea inlet of the Indian Ocean, lying between Africa and Asia. Its connection to the ocean is in the south, through the Bab-el-Mandeb Strait and the Gulf of Aden. To its north lie the Sinai Peninsula, the Gulf of Aqaba, and th ...
, including
Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...
,
Mauritius Mauritius, officially the Republic of Mauritius, is an island country in the Indian Ocean, about off the southeastern coast of East Africa, east of Madagascar. It includes the main island (also called Mauritius), as well as Rodrigues, Ag ...
, and the
Seychelles Seychelles (, ; ), officially the Republic of Seychelles (; Seychellois Creole: ), is an island country and archipelagic state consisting of 155 islands (as per the Constitution) in the Indian Ocean. Its capital and largest city, Victoria, ...
, and from there eastward along the coast of the
Indian Subcontinent The Indian subcontinent is a physiographic region of Asia below the Himalayas which projects into the Indian Ocean between the Bay of Bengal to the east and the Arabian Sea to the west. It is now divided between Bangladesh, India, and Pakista ...
to
Southeast Asia Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...
, including
Sri Lanka Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka, also known historically as Ceylon, is an island country in South Asia. It lies in the Indian Ocean, southwest of the Bay of Bengal, separated from the Indian subcontinent, ...
, the
Andaman Islands The Andaman Islands () are an archipelago, made up of 200 islands, in the northeastern Indian Ocean about southwest off the coasts of Myanmar's Ayeyarwady Region. Together with the Nicobar Islands to their south, the Andamans serve as a mari ...
, and the
Maldives The Maldives, officially the Republic of Maldives, and historically known as the Maldive Islands, is an Archipelagic state, archipelagic country in South Asia located in the Indian Ocean. The Maldives is southwest of Sri Lanka and India, abou ...
. In the
Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...
, it is found from southern
China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
and the
Philippines The Philippines, officially the Republic of the Philippines, is an Archipelagic state, archipelagic country in Southeast Asia. Located in the western Pacific Ocean, it consists of List of islands of the Philippines, 7,641 islands, with a tot ...
to
Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...
, northern
Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
and
New Caledonia New Caledonia ( ; ) is a group of islands in the southwest Pacific Ocean, southwest of Vanuatu and east of Australia. Located from Metropolitan France, it forms a Overseas France#Sui generis collectivity, ''sui generis'' collectivity of t ...
, and also inhabits numerous oceanic islands, including the
Marshall Marshall may refer to: Places Australia *Marshall, Victoria, a suburb of Geelong, Victoria ** Marshall railway station Canada * Marshall, Saskatchewan * The Marshall, a mountain in British Columbia Liberia * Marshall, Liberia Marshall Is ...
, Gilbert,
Society A society () is a group of individuals involved in persistent social interaction or a large social group sharing the same spatial or social territory, typically subject to the same political authority and dominant cultural expectations. ...
, and
Hawaiian Islands The Hawaiian Islands () are an archipelago of eight major volcanic islands, several atolls, and numerous smaller islets in the Pacific Ocean, North Pacific Ocean, extending some from the Hawaii (island), island of Hawaii in the south to nort ...
and
Tuamotu The Tuamotu Archipelago or the Tuamotu Islands (, officially ) are a French Polynesian chain of just under 80 islands and atolls in the southern Pacific Ocean. They constitute the largest chain of atolls in the world, extending (from northwest to ...
. Contrary to what most sources state, there is a report suggesting that the specimens of this species from
Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...
ese waters might be from
Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main geography of Taiwan, island of Taiwan, also known as ''Formosa'', lies between the East China Sea, East and South China Seas in the northwestern Pacific Ocea ...
, however a number of sightings and captures of this species have been reported from the inshore waters of
Ishigaki Island , also known as ''Ishigakijima'', is a Japanese island south-west of Okinawa Hontō and the second-largest island of the Yaeyama Island group, behind Iriomote Island. It is located approximately south-west of Okinawa Hontō. It is within t ...
of
Okinawa Prefecture is the southernmost and westernmost prefecture of Japan. It consists of three main island groups—the Okinawa Islands, the Sakishima Islands, and the Daitō Islands—spread across a maritime zone approximately 1,000 kilometers east to west an ...
in southern
Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...
. A
Lessepsian migrant The Lessepsian migration (or Erythrean invasion) is the migration of marine species along the Suez Canal, usually from the Red Sea to the Mediterranean Sea, and more rarely in the opposite direction. When the canal was completed in 1869, fish, ...
, this shark has colonized the eastern
Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...
by way of the
Suez Canal The Suez Canal (; , ') is an artificial sea-level waterway in Egypt, Indo-Mediterranean, connecting the Mediterranean Sea to the Red Sea through the Isthmus of Suez and dividing Africa and Asia (and by extension, the Sinai Peninsula from the rest ...
. Although it has been reported from a depth of , the blacktip reef shark is usually found in water only a few meters deep, and can often be seen swimming close to shore with its dorsal fin exposed. Younger sharks prefer shallow, sandy flats, while older sharks are most common around reef ledges and can also be found near reef drop-offs. This species has also been reported from
brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...
estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environm ...
and
lake A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from ...
s in Madagascar, and
freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...
environments in
Malaysia Malaysia is a country in Southeast Asia. Featuring the Tanjung Piai, southernmost point of continental Eurasia, it is a federation, federal constitutional monarchy consisting of States and federal territories of Malaysia, 13 states and thre ...
, though it is not able to tolerate low
salinity Salinity () is the saltiness or amount of salt (chemistry), salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensio ...
to the same degree as the
bull shark The bull shark (''Carcharhinus leucas''), also known as the Zambezi shark (informally zambi) in Africa and Lake Nicaragua shark in Nicaragua, is a species of requiem shark commonly found worldwide in warm, shallow waters along coasts and in riv ...
(''C. leucas''). At
Aldabra Aldabra, the world's second-largest coral atoll (the largest is Kiritimati), is located east of the continent of Africa. It is part of the Aldabra Group of islands in the Indian Ocean that are part of the Outer Islands (Seychelles), Outer Islands ...
in the Indian Ocean, blacktip reef sharks congregate in the channels between reef flats during
low tide Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables c ...
and travel to the
mangrove A mangrove is a shrub or tree that grows mainly in coastal saline water, saline or brackish water. Mangroves grow in an equatorial climate, typically along coastlines and tidal rivers. They have particular adaptations to take in extra oxygen a ...
s when the water rises. There is equivocal evidence that sharks from the northern and southern extremes of its distribution are migratory. Blacktip reef shark (Carcharhinus melanopterus) Moorea.jpg Blacktip reef sharks (Carcharhinus melanopterus) Moorea.jpg Blacktip reef shark (Carcharhinus melanopterus) Moorea 4.jpg


Description

A robustly built species with a streamlined "typical shark" form, the blacktip reef shark has a short, wide, rounded snout and moderately large, oval eyes. Each
nostril A nostril (or naris , : nares ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called turbinates ...
has a flap of skin in front that is expanded into a nipple-shaped lobe. Not counting small symphysial (central) teeth, the tooth rows number 11–13 (usually 12) on either side of the upper jaw and 10–12 (usually 11) on either side of the lower jaw. The upper teeth are upright to angled and narrowly triangular in shape, bearing serrations that are more coarse on the bases; the lower teeth are similar, but more finely serrated. The teeth of adult males are more abruptly curved than those of females.Press, M
Biological Profiles: Blacktip Reef Shark
. Florida Museum of Natural History Ichthyology Department. Retrieved on October 3, 2009.
The
pectoral fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...
s are large and narrowly falcate (sickle-shaped), tapering to points. The sizable first
dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...
is high with a curving S-shaped rear margin, and originates over the free rear tips of the pectoral fins. The second dorsal fin is relatively large with a short rear margin, and is placed opposite the
anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...
. There is no ridge between the dorsal fins. This shark is a pale grayish-brown above and white below, with an obvious white band on the sides extending forward from above the anal fin. All the fins have black tips highlighted by lighter-colored borders, which are especially striking on the first dorsal fin and lower caudal fin lobe. Most blacktip reef sharks are no more than long, though rarely individuals may reach or possibly . The maximum weight on record with the
International Game Fish Association The International Game Fish Association (''IGFA'') is the leading authority on angling pursuits and the keeper of the most current world record fishing catches by fish categories. Fishermen who are sport fishers and anglers are careful to follow ...
is . Carcharhinus melanopterus jaws.jpg, Jaws Carcharhinus melanopterus upper teeth.jpg, Upper teeth Carcharhinus melanopterus lower teeth.jpg, Lower teeth


Biology and ecology

Along with the
grey reef shark The grey reef shark or gray reef shark (''Carcharhinus amblyrhynchos'', sometimes misspelled ''amblyrhynchus'' or ''amblyrhinchos'') is a species of requiem shark, in the family (biology), family Requiem shark, Carcharhinidae. One of the most com ...
(''C. amblyrhinchos'') and the
whitetip reef shark The whitetip reef shark (''Triaenodon obesus'') is a species of requiem shark, in the family Carcharhinidae, and the only member of its genus. A small shark that does not usually exceed in length, this species is easily recognizable by its sle ...
(''Triaenodon obesus''), the blacktip reef shark is one of the three most common sharks inhabiting coral reefs in the Indo-Pacific. This species predominates in shallow habitats, while the other two are mostly found deeper. Fast-swimming and active, the blacktip reef shark may be encountered alone or in small groups; large "social" aggregations have also been observed. For the most part, juvenile and adult sharks are not segregated by sex, save for the movements of pregnant females to give birth. Individuals exhibit strong fidelity to particular areas, where they may remain for several years. A tracking study off
Palmyra Atoll Palmyra Atoll (), also referred to as Palmyra Island, is one of the Line Islands, Northern Line Islands (southeast of Kingman Reef and north of Kiribati). It is located almost due south of the Hawaiian Islands, roughly one-third of the way be ...
in the central Pacific has found the blacktip reef shark has a home range of around , among the smallest of any shark species. The size and location of the range does not change with time of day. Within this range, 3–17% of the area constitute favored hunting patches that are disproportionately occupied by the resident shark. The sharks spend most of their time swimming back and forth along reef ledges, making occasional short forays onto sandy flats. Their average swimming speed decreases when the tide rises at night, possibly because the influx of cooler water reduces their
metabolism Metabolism (, from ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the co ...
, or the accompanying movement of
prey fish Forage fish, also called prey fish or bait fish, are small pelagic fish that feed on planktons (i.e. planktivores) and other small aquatic organisms (e.g. krill). They are in turn preyed upon by various predators including larger fish, seabird ...
es makes foraging easier. Blacktip reef sharks at Aldabra tend to be more mobile than those at Palmyra, with recorded individual movements of up to over 7 hours. Blacktip reef sharks, particularly small individuals, fall prey to larger fishes, including
grouper Groupers are a diverse group of marine ray-finned fish in the family Epinephelidae, in the order Perciformes. Groupers were long considered a subfamily of the seabasses in Serranidae, but are now treated as distinct. Not all members of this f ...
s,
grey reef shark The grey reef shark or gray reef shark (''Carcharhinus amblyrhynchos'', sometimes misspelled ''amblyrhynchus'' or ''amblyrhinchos'') is a species of requiem shark, in the family (biology), family Requiem shark, Carcharhinidae. One of the most com ...
s,
tiger shark The tiger shark (''Galeocerdo cuvier'') is a species of ground shark, and the only extant member of the genus '' Galeocerdo'' and family Galeocerdonidae. It is a large apex predator, with females capable of attaining a length of over . Popula ...
s (''Galeocerdo cuvier''), and members of their own species. At Palmyra Atoll, adults avoid patrolling tiger sharks by staying out of the central, deeper lagoon. Their known
parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...
s include the
tapeworm Eucestoda, commonly referred to as tapeworms, is the larger of the two subclasses of flatworms in the class Cestoda (the other subclass being Cestodaria). Larvae have six posterior hooks on the scolex (head), in contrast to the ten-hooked Ce ...
s ''Anthobothrium lesteri'', ''Nybelinia queenslandensis'', ''Otobothrium alexanderi'', and ''Platybothrium jondoeorum'', a myxosporidian in the genus ''Unicapsula'', and the
monogenea Monogeneans, members of the class Monogenea, are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish. They have a direct lifecycle and do not require an intermediate host. Adults are hermaphrodites, meaning they ...
n ''Dermophthirius melanopteri''. One of the few documented examples of
infectious disease An infection is the invasion of tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmis ...
in a shark was a fatal case of
hemorrhagic Bleeding, hemorrhage, haemorrhage or blood loss, is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethra, va ...
septicemia Sepsis is a potentially life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage of sepsis is followed by suppression of the immune system. Common signs and s ...
in a blacktip reef shark, caused by the
bacterium Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the ...
''
Aeromonas salmonicida ''Aeromonas salmonicida'' is a pathogenic bacterium that severely impacts salmonid populations and other species. It was first discovered in a Bavarian brown trout hatchery by Emmerich and Weibel in 1894. ''Aeromonas salmonicida's'' ability to in ...
'' subsp. ''salmonicida''.


Feeding

As often the most abundant
apex predator An apex predator, also known as a top predator or superpredator, is a predator at the top of a food chain, without natural predators of its own. Apex predators are usually defined in terms of trophic dynamics, meaning that they occupy the hig ...
within its
ecosystem An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...
, the blacktip reef shark plays a major role in structuring inshore
ecological communities In ecology, a community is a group or association of populations of two or more different species occupying the same geographical area at the same time, also known as a biocoenosis, biotic community, biological community, ecological community ...
. Its diet is composed primarily of small
teleost fish Teleostei (; Ancient Greek, Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts (), is, by far, the largest group of ray-finned fishes (class Actinopterygii), with 96% of all neontology, extant species of f ...
es, including mullet, groupers, grunters, jacks,
mojarra The mojarras are a family, Gerreidae, of fish in the order Perciformes. The family includes about 53 species found worldwide in tropical and warm temperate regions. They mostly inhabit coastal salt and brackish waters, although some occur in fre ...
s,
wrasse The wrasses are a family, Labridae, of marine ray-finned fish, many of which are brightly colored. The family is large and diverse, with over 600 species in 81 genera, which are divided into nine subgroups or tribes. They are typically small, ...
s,
surgeonfish Acanthuridae are a family (biology), family of ray-finned fish which includes surgeonfishes, tangs, and Naso (fish), unicornfishes. The family includes about 86 Extant taxon, extant species of ocean, marine fish living in tropical seas, usually ...
, and smelt-whitings. Groups of blacktip reef sharks in the Indian Ocean have been observed herding
schools A school is the educational institution (and, in the case of in-person learning, the building) designed to provide learning environments for the teaching of students, usually under the direction of teachers. Most countries have systems of ...
of mullet against the shore for easier feeding.
Squid A squid (: squid) is a mollusc with an elongated soft body, large eyes, eight cephalopod limb, arms, and two tentacles in the orders Myopsida, Oegopsida, and Bathyteuthida (though many other molluscs within the broader Neocoleoidea are also ...
,
octopus An octopus (: octopuses or octopodes) is a soft-bodied, eight-limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids. Like oth ...
,
cuttlefish Cuttlefish, or cuttles, are Marine (ocean), marine Mollusca, molluscs of the order (biology), suborder Sepiina. They belong to the class (biology), class Cephalopoda which also includes squid, octopuses, and nautiluses. Cuttlefish have a unique ...
,
shrimp A shrimp (: shrimp (American English, US) or shrimps (British English, UK)) is a crustacean with an elongated body and a primarily Aquatic locomotion, swimming mode of locomotion – typically Decapods belonging to the Caridea or Dendrobranchi ...
, and
mantis shrimp Mantis shrimp are carnivorous marine crustaceans of the order Stomatopoda (). Stomatopods branched off from other members of the class Malacostraca around 400 million years ago, with more than 520 extant species of mantis shrimp known. All li ...
are also taken, as well as
carrion Carrion (), also known as a carcass, is the decaying flesh of dead animals. Overview Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters (or scavengers) include crows, vultures ...
and smaller
sharks and rays Elasmobranchii () is a subclass of Chondrichthyes or cartilaginous fish, including modern sharks ( division Selachii), and batomorphs (division Batomorphi, including rays, skates, and sawfish). Members of this subclass are characterised by hav ...
, though this is rare. Off northern Australia, this species is known to consume
sea snake Sea snakes, or coral reef snakes, are Elapidae, elapid snakes that inhabit Marine (ocean), marine environments for most or all of their lives. They belong to two subfamilies, Hydrophiinae and Sea krait, Laticaudinae. Hydrophiinae also includes ...
s, including ''
Acrochordus granulatus ''Acrochordus granulatus'' is a snake species found from India through Southeast Asia to the Solomon Islands. It is known as the little file snake, marine file snake, and little wart snake.
'', '' Hydrelaps darwiniensis'', ''
Hydrophis ''Hydrophis'' is a genus of sea snakes, venomous snakes in the subfamily Hydrophiinae of the Family (biology), family Elapidae. Species in the genus ''Hydrophis'' are typically found in Indo-Australian and Southeast Asian waters. Currently, arou ...
'' spp. and '' Lapemis hardwickii''. Sharks off Palmyra Atoll have been documented preying on
seabird Seabirds (also known as marine birds) are birds that are adaptation, adapted to life within the marine ecosystem, marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent ...
chicks that have fallen out of their
nest A nest is a structure built for certain animals to hold Egg (biology), eggs or young. Although nests are most closely associated with birds, members of all classes of vertebrates and some invertebrates construct nests. They may be composed of ...
s into the water. Miscellaneous items that have been found inside the
stomach The stomach is a muscular, hollow organ in the upper gastrointestinal tract of Human, humans and many other animals, including several invertebrates. The Ancient Greek name for the stomach is ''gaster'' which is used as ''gastric'' in medical t ...
s of this species include
algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...
, turtle grass,
coral Corals are colonial marine invertebrates within the subphylum Anthozoa of the phylum Cnidaria. They typically form compact Colony (biology), colonies of many identical individual polyp (zoology), polyps. Coral species include the important Coral ...
,
hydrozoa Hydrozoa (hydrozoans; from Ancient Greek ('; "water") and ('; "animals")) is a taxonomy (biology), taxonomic class (biology), class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline wat ...
,
bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic animal, aquatic invertebrate animals, nearly all living in sedentary Colony (biology), colonies. Typically about long, they have a spe ...
,
rat Rats are various medium-sized, long-tailed rodents. Species of rats are found throughout the order Rodentia, but stereotypical rats are found in the genus ''Rattus''. Other rat genera include '' Neotoma'' (pack rats), '' Bandicota'' (bandicoo ...
s, and stones. Researchers working at
Enewetak Atoll Enewetak Atoll (; also spelled Eniwetok Atoll or sometimes Eniewetok; , , or , ; known to the Japanese as Brown Atoll or Brown Island; ) is a large coral atoll of 40 islands in the Pacific Ocean and with its 296 people (as of 2021) forms a leg ...
in the Marshall Islands have found the blacktip reef shark can be readily attracted by splashing or striking metal tools against hard objects underwater, as well as by the scent of both healthy and injured fish. As with most sharks, the blacktip reef shark does not have any
cone cell Cone cells or cones are photoreceptor cells in the retina of the vertebrate eye. Cones are active in daylight conditions and enable photopic vision, as opposed to rod cells, which are active in dim light and enable scotopic vision. Most v ...
s in its
retina The retina (; or retinas) is the innermost, photosensitivity, light-sensitive layer of tissue (biology), tissue of the eye of most vertebrates and some Mollusca, molluscs. The optics of the eye create a focus (optics), focused two-dimensional ...
, limiting its ability to discriminate colors and fine details. Instead, its vision is adapted for sensitivity to movement or contrast under low light conditions, which is further enhanced by the presence of a reflective
tapetum lucidum The ; ; : tapeta lucida) is a layer of tissue in the eye of many vertebrates and some other animals. Lying immediately behind the retina, it is a retroreflector. It Reflection (physics), reflects visible light back through the retina, increas ...
. Experiments have shown that this shark is capable of detecting small objects up to away, but is unable to clearly discern the shape of the object.
Electroreception Electroreception and electrogenesis are the closely related biological abilities to perceive electrical stimuli and to generate electric fields. Both are used to locate prey; stronger electric discharges are used in a few groups of fishes, such ...
is another means by which this shark can locate prey; its
ampullae of Lorenzini Ampullae of Lorenzini (: ''ampulla'') are electroreceptors, sense organs able to detect electric fields. They form a network of mucus-filled pores in the skin of Chondrichthyes, cartilaginous fish (sharks, Ray (fish), rays, and chimaeras) and of ...
have a sensitivity of approximately 4 nV/cm and an effective range of . Similar to the grey reef shark, this species becomes more excited and "confident" in the presence of other individuals of its species, and in extreme situations can be roused into a
feeding frenzy In ecology, a feeding frenzy is a type of animal group activity that occurs when predators are overwhelmed by the amount of prey available. The term is also used as an idiom in the English language. Examples in nature For example, a large schoo ...
. Feeding activity may be greater at night than during the day.


Life history

Like the other members of its family, the blacktip reef shark is
viviparous In animals, viviparity is development of the embryo inside the body of the mother, with the maternal circulation providing for the metabolic needs of the embryo's development, until the mother gives birth to a fully or partially developed juve ...
, though the details of its life history vary across its range. Its reproductive cycle is annual off northern
Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
, with mating taking place from January to February, as well as off Moorea in
French Polynesia French Polynesia ( ; ; ) is an overseas collectivity of France and its sole #Governance, overseas country. It comprises 121 geographically dispersed islands and atolls stretching over more than in the Pacific Ocean, South Pacific Ocean. The t ...
, where mating occurs from November to March. The cycle is biennial off Aldabra, where intense competition within and between species for food may constrain females to only bearing young every other year. Earlier accounts from the Indian Ocean by Johnson (1978), Madagascar by Fourmanoir (1961), and the Red Sea by Gohar and Mazhar (1964), indicated a biannual cycle in these regions with two breeding seasons per year from June to July and December to January. If accurate, the shorter reproductive cycles of these subpopulations may be a consequence of warmer water. When receptive to mating, a female blacktip reef shark swims slowly in a
sinusoidal A sine wave, sinusoidal wave, or sinusoid (symbol: ∿) is a periodic wave whose waveform (shape) is the trigonometric sine function. In mechanics, as a linear motion over time, this is '' simple harmonic motion''; as rotation, it correspond ...
pattern near the bottom with her head pointed down; observations in the wild suggest female sharks release chemical signals that allow males to track them. Once the male finds her, he closes to around and follows her with his snout oriented towards her vent. A courting male may also bite the female behind her gills or on her pectoral fins; these mating wounds heal completely after 4–6 weeks. After a period of synchronous swimming, the male pushes the female on her side and positions her so her head is against the bottom and her tail is raised. Once the female is in position, the male inserts one of his
claspers In biology, a clasper is a male anatomical structure found in some groups of animals, used in mating. Male cartilaginous fish have claspers formed from the posterior portion of their pelvic fin which serve to channel semen into the female's c ...
into her
cloaca A cloaca ( ), : cloacae ( or ), or vent, is the rear orifice that serves as the only opening for the digestive (rectum), reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles, birds, cartilagin ...
.
Copulation Sexual intercourse (also coitus or copulation) is a sexual activity typically involving the insertion of the erect male penis inside the female vagina and followed by thrusting motions for sexual pleasure, reproduction, or both.Sexual inte ...
lasts for several minutes, after which the sharks separate and resume their regular behavior. Off Moorea, individual older females mate and give birth at a consistent time every year, often to within a week's precision, whereas younger females exhibit more variability in their timing. Younger females are also more likely to fail to become pregnant after mating. The
gestation period In mammals, pregnancy is the period of reproduction during which a female carries one or more live offspring from implantation in the uterus through gestation. It begins when a fertilized zygote implants in the female's uterus, and ends once i ...
has been reported as 10–11 months long in the Indian Ocean and Pacific islands, and 7–9 months long off northern Australia. Earlier authors, such as Melouk (1957), have estimated a gestation period as long as 16 months, though the validity of this figure has subsequently been challenged. The female has a single functional
ovary The ovary () is a gonad in the female reproductive system that produces ova; when released, an ovum travels through the fallopian tube/ oviduct into the uterus. There is an ovary on the left and the right side of the body. The ovaries are end ...
(on the right) and two functional
uterus The uterus (from Latin ''uterus'', : uteri or uteruses) or womb () is the hollow organ, organ in the reproductive system of most female mammals, including humans, that accommodates the embryonic development, embryonic and prenatal development, f ...
es, divided into separate compartments for each
embryo An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sp ...
. Newly ovulated egg cases measure by ; after hatching the embryos are sustained by a
yolk sac The yolk sac is a membranous wikt:sac, sac attached to an embryo, formed by cells of the hypoblast layer of the bilaminar embryonic disc. This is alternatively called the umbilical vesicle by the Terminologia Embryologica (TE), though ''yolk sac' ...
during the first stage of development. After two months, the embryo measures long and has well-developed external gills. After four months, the yolk sac has begun to be converted into a
placenta The placenta (: placentas or placentae) is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas, and waste exchange between ...
l connection that attaches to the uterine wall; at this time, the embryo's dark fin markings develop. By five months, the embryo measures and has resorbed its external gills; the placenta is fully formed, though some yolk remains until seven months into gestation. Parturition occurs from September to November, with females making use of shallow nursery areas interior of the reef. Newborn pups measure long in the Indian Ocean and off northern Australia, while free-swimming pups as small as long have been observed in the Pacific islands. The litter size is 2–5 (typically 4), and is not correlated with female size. Young blacktip reef sharks commonly form large groups in water barely deep enough to cover their bodies, over sand flats or in mangrove swamps close to shore. During high tide, they also move onto flooded coral platforms or
seaweed Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of ''Rhodophyta'' (red), '' Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as ...
beds. Growth is initially rapid; one documented captive shark grew an average of per year in its first two years of life. The growth rate slows to around per year in juveniles and adults. Males and females
mature sexually Sexual maturity is the capability of an organism to reproduce. In humans, it is related to both puberty and adulthood. ''Puberty'' is the biological process of sexual maturation, while ''adulthood'', the condition of being socially recognized as ...
at lengths of and respectively off northern Australia, and and , respectively, off Aldabra. Males mature at long off Palmyra Atoll.


Human interactions

Under most circumstances, the blacktip reef shark has a timid demeanor and is easily frightened away by swimmers. However, its inshore habitat preferences bring it into frequent contact with humans, and thus it is regarded as potentially dangerous. As of early 2009, 11 unprovoked attacks and 21 attacks total (none fatal) were listed on the International Shark Attack File that are attributable to the blacktip reef shark.ISAF Statistics on Attacking Species of Shark
International Shark Attack File, Florida Museum of Natural History, University of Florida. Retrieved on May 18, 2009.
Most attacks involve sharks biting the legs or feet of waders, apparently mistaking them for their natural prey, and do not result in serious injury. In the Marshall Islands, native islanders avoid blacktip reef shark attacks by swimming rather than wading through shallow water, as a way of discouraging these sharks is to submerge one's body. The blacktip reef shark has also been known to become aggressive in the presence of bait, and may pose a threat while attempting to steal the catches of spear fishers. The blacktip reef shark is a normal catch of coastal
fisheries Fishery can mean either the enterprise of raising or harvesting fish and other aquatic life or, more commonly, the site where such enterprise takes place ( a.k.a., fishing grounds). Commercial fisheries include wild fisheries and fish farm ...
, such as those operating off
Thailand Thailand, officially the Kingdom of Thailand and historically known as Siam (the official name until 1939), is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. With a population of almost 66 million, it spa ...
and
India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...
, but is not targeted or considered commercially important. The meat (sold fresh, frozen, dried and salted, or smoked for human consumption), liver oil, and
fins A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foil (fluid mechanics), foils that produce lift (force), lift or thrust, or provide the ability to steer or stabilize motion while travelin ...
are used. The
International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the stat ...
has assessed the blacktip reef shark as Vulnerable and declining. Though it remains widespread and common overall, substantial local declines due to
overfishing Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing Fish stocks, fish stock), resu ...
have now been documented in many areas. This species has a low reproductive rate, limiting its capacity for recovering from depletion. Blacktip reef sharks are popular subjects of
public aquarium A public aquarium () or public water zoo is the aquatic counterpart of a zoo, which houses living aquatic animal and aquatic plant, plant specimens for public viewing. Most public aquariums feature tanks larger than those kept by home aquarists, ...
exhibits, because of their stereotypically "shark-like" appearance, ability to breed in captivity and modest size, and are also attractions for
ecotourism Ecotourism is a form of nature-oriented tourism intended to contribute to the Ecological conservation, conservation of the natural environment, generally defined as being minimally impactful, and including providing both contributions to conserv ...
divers.


See also

*
Oceanic whitetip shark The oceanic whitetip shark (''Carcharhinus longimanus'') is a large requiem shark inhabiting the pelagic zone of tropical and warm temperate seas. It has a stocky body with its iconic elongated rounded fins, with white tips. The species is ...
and
Whitetip reef shark The whitetip reef shark (''Triaenodon obesus'') is a species of requiem shark, in the family Carcharhinidae, and the only member of its genus. A small shark that does not usually exceed in length, this species is easily recognizable by its sle ...
– another species of requiem sharks known for and named after the coloration of the tips of its fins


References


External links


''Carcharhinus melanopterus'', Blacktip reef shark
a
FishBase


a
Florida Museum of Natural History Ichthyology Department
* {{Good article Carcharhinus Fish of the Indian Ocean Fish of the Pacific Ocean Fish described in 1824