Graceful shark
Encyclopedia
The graceful shark or Queensland shark (Carcharhinus amblyrhynchoides) 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 50 m (164 ft). A stoutly built shark growing up to 1.7 m (5.6 ft) long, the graceful shark has a short, wedge-shaped snout, large, sickle-shaped pectoral fins and first dorsal fin
, and black tips on most fins.
Graceful sharks prey mainly on bony fishes, and to a much lesser extent on cephalopod
s and crustacean
s. It is viviparous, with females bearing litters of up to nine pups following a 9–10 month gestation period
. Off northern Australia, birthing occurs in January and February, with mating
shortly after. This species is potentially dangerous but has not been implicated in any attacks
. It is caught incidentally
by commercial fisheries throughout its range for meat, fins, and liver oil
, though specific information is lacking. The International Union for Conservation of Nature (IUCN) has listed it under Near Threatened
.
originally described the graceful shark as Gillisqualus amblyrhynchoides, in an 1834 issue of Memoirs of the Queensland Museum. He based his account on a 60 cm (23.6 in) long immature female caught off Cape Bowling Green in Queensland
, hence the alternate common name
Queensland shark. Later authors have synonymized
Gillisqualus with Carcharhinus.
As with most Carcharhinus species, the evolutionary relationships
of the graceful shark are poorly resolved. Based on morphology
, Jack Garrick concluded in 1982 that its closest relative was the blacktip shark
(C. limbatus), and that the two were closely related to the spinner shark
(C. brevipinna). Leonard Compagno
, in his 1988 phenetic study, also grouped those species together, along with the smoothtooth blacktip shark (C. leiodon) and the finetooth shark
(C. isodon). However, molecular phylogenetic techniques have since found this interpretation to be invalid for the spinner, blacktip, and finetooth sharks.
, having been reported from the Gulf of Aden
, southwestern India and Sri Lanka, the Gulf of Thailand
, Vietnam, the Philippines to Borneo
and Java
, and Papua New Guinea
to northern Australia from Townsville
to Eighty Mile Beach. Given its rarity and the difficulty in distinguishing it from related species, its range is probably continuous and wider than the present patchy records suggest. The graceful shark is an open water inhabitant that can be found from close to shore to the outer continental and insular shelves
, diving at least 50 m (164 ft) down.
s (protective third eyelids). The mouth has short, indistinct furrows at the corners and contains 31–33 upper and 29–33 lower tooth rows. The upper teeth have a single narrow cusp with serrated edges, upright at the center of the jaw and becoming more oblique on the sides. The lower teeth are similar to the upper teeth but more upright and slender. The five pairs of gill slit
s are fairly long.
The pectoral fins are falcate (sickle-shaped) and taper to pointed tips; their leading margins measure about a fifth as long as the total length in sharks over 80 cm (31.5 in) long. The first dorsal fin
is high and broad, with a pointed apex and a concave trailing margin; its origin lies roughly over the insertion (the rear of the fin base) of the pectoral fins. The second dorsal fin is relatively large and located about opposite the anal fin, which is about of equal size. There is no ridge between the dorsal fins. The caudal fin has a well-developed lower lobe and a ventral notch near the tip of the upper lobe. This species is bronze above and white below, which extends onto the flanks as a pale stripe. The pectoral fins, dorsal fins, lower caudal fin lobe, and sometimes the pelvic fins usually have black tips, while the upper caudal fin lobe darkens towards the trailing edge and the anal fin may be completely light. The fin markings tend to fade with age. The maximum known length is 1.7 m (5.6 ft).
s and crustacean
s being of minor importance. Jacks
make up over 60% of its fish diet in the Gulf of Carpentaria
. Like other members of its family, this species is viviparous: once the developing embryo
s exhaust their supply of yolk, the depleted yolk sac
is converted into a placenta
l connection to the mother. Off northern Australia, males and females likely mate every year in February, with ovulation
following shortly after. Females typically bear litters of three, though individuals gestating up to nine pups have been reported. The young are born in January or February, following a gestation period
of 9–10 months. Sexual maturity
is attained at a length of 1.1–1.2 m (3.6–3.9 ft) for both sexes. A known parasite of this species is a tapeworm in the genus Cathetocephalus.
have been recorded. It is caught incidentally
by commercial fisheries in Thailand, India, Sri Lanka, and probably elsewhere, using gillnet
s and longlines. It is a minor component of shark catches off northern Australia, comprising around 1.5% and 0.2% of all sharks caught in gillnets and on longlines respectively in the mid-1980s. Catches in the region have declined from historical highs in the 1970s and 1980s, due to the departure of foreign fishing vessels following new gillnet regulations. The meat is sold fresh or dried and salted, the fins are shipped to East Asia
for shark fin soup
, and the liver
is processed for vitamin
s. The International Union for Conservation of Nature (IUCN) has assessed this species as Near Threatened
, noting that more biological and fishery information is needed.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of requiem shark
Requiem shark
Requiem sharks are a family, Carcharhinidae, of sharks in the order Carcharhiniformes, containing migratory, live-bearing sharks of warm seas such as the tiger shark, the blue shark, the bull shark, and the milk shark.The name may be related to the French word for shark, "requin", itself of...
, family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Carcharhinidae, found in the tropical Indo-Pacific
Indo-Pacific
The Indo-Pacific is a biogeographic region of the Earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia...
from 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 northern Australia
Northern Australia
The term northern Australia is generally known to include two State and Territories, being Queensland and the Northern Territory . The part of Western Australia north of latitude 26° south—a definition widely used in law and State government policy—is also usually included...
. It is a midwater species that has been recorded to a depth of 50 m (164 ft). A stoutly built shark growing up to 1.7 m (5.6 ft) long, the graceful shark has a short, wedge-shaped snout, large, sickle-shaped pectoral fins and 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...
, and black tips on most fins.
Graceful sharks prey mainly on bony fishes, and to a much lesser extent on 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 and crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s. It is viviparous, with females bearing litters of up to nine pups following a 9–10 month gestation period
Gestation period
For mammals the gestation period is the time in which a fetus develops, beginning with fertilization and ending at birth. The duration of this period varies between species.-Duration:...
. Off northern Australia, birthing occurs in January and February, with mating
Mating
In biology, mating is the pairing of opposite-sex or hermaphroditic organisms for copulation. In social animals, it also includes the raising of their offspring. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization...
shortly after. This species is potentially dangerous but has not been implicated in any attacks
Shark attack
A shark attack is an attack on a human by a shark. Every year around 60 shark attacks are reported worldwide, although death is quite unusual. Despite the relative rarity of shark attacks, the fear of sharks is a common phenomenon, having been fueled by the occasional instances of serial attacks,...
. It is caught incidentally
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...
by commercial fisheries throughout its range for meat, fins, and 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...
, though specific information is lacking. The International Union for Conservation of Nature (IUCN) has listed it under 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...
.
Taxonomy and phylogeny
Australian ichthyologist Gilbert Percy WhitleyGilbert Percy Whitley
Gilbert Percy Whitley was a British-born Australian ichthyologist and malacologist who was Curator of Fishes at the Australian Museum in Sydney for about 40 years. He was born at Swaythling, Southampton, England, and was educated at King Edward VI School, Southampton and Osborne House...
originally described the graceful shark as Gillisqualus amblyrhynchoides, in an 1834 issue of Memoirs of the Queensland Museum. He based his account on a 60 cm (23.6 in) long immature female caught off Cape Bowling Green in Queensland
Queensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
, hence the alternate common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
Queensland shark. Later authors have synonymized
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...
Gillisqualus with Carcharhinus.
As with most Carcharhinus species, the evolutionary relationships
Phylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...
of the graceful shark are poorly resolved. Based on 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....
, Jack Garrick concluded in 1982 that its closest relative was 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), and that the two were closely related to the spinner shark
Spinner shark
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...
(C. brevipinna). Leonard Compagno
Leonard Compagno
Leonard Joseph Victor Compagno is 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 Agriculture Organization of the United Nations.-Career:*Ph.D,...
, in his 1988 phenetic study, also grouped those species together, along with the smoothtooth blacktip shark (C. leiodon) and the finetooth shark
Finetooth shark
The finetooth shark is a species of requiem shark, family Carcharhinidae, found in the western Atlantic Ocean from North Carolina to Brazil. It forms large schools in shallow, coastal waters and migrates seasonally following warm water...
(C. isodon). However, molecular phylogenetic techniques have since found this interpretation to be invalid for the spinner, blacktip, and finetooth sharks.
Distribution and habitat
The graceful shark is distributed widely in the tropical Indo-PacificIndo-Pacific
The Indo-Pacific is a biogeographic region of the Earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia...
, having been reported from 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....
, southwestern India and Sri Lanka, the Gulf of Thailand
Gulf of Thailand
The Gulf of Thailand , also known in to Malays as Teluk Siam literally meant Gulf of Siam, is a shallow arm of the South China Sea.-Geography:...
, Vietnam, the Philippines to Borneo
Borneo
Borneo is the third largest island in the world and is located north of Java Island, Indonesia, at the geographic centre of Maritime Southeast Asia....
and 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 Papua New Guinea
Papua New Guinea
Papua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...
to northern Australia from Townsville
Townsville, Queensland
Townsville is a city on the north-eastern coast of Australia, in the state of Queensland. Adjacent to the central section of the Great Barrier Reef, it is in the dry tropics region of Queensland. Townsville is Australia's largest urban centre north of the Sunshine Coast, with a 2006 census...
to Eighty Mile Beach. Given its rarity and the difficulty in distinguishing it from related species, its range is probably continuous and wider than the present patchy records suggest. The graceful shark is an open water inhabitant that can be found from close to shore to the outer continental and insular shelves
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
, diving at least 50 m (164 ft) down.
Description
Contrary to its common name, the graceful shark's spindle-shaped body has been described as "tubby". The wedge-like snout is short and pointed. The eyes are rather large and circular, and equipped with nictitating membraneNictitating membrane
The nictitating membrane is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten it while maintaining visibility. Some reptiles, birds, and sharks have a full nictitating membrane; in many mammals, there is a small...
s (protective third eyelids). The mouth has short, indistinct furrows at the corners and contains 31–33 upper and 29–33 lower tooth rows. The upper teeth have a single narrow cusp with serrated edges, upright at the center of the jaw and becoming more oblique on the sides. The lower teeth are similar to the upper teeth but more upright and slender. The five pairs of gill slit
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 fairly long.
The pectoral fins are falcate (sickle-shaped) and taper to pointed tips; their leading margins measure about a fifth as long as the total length in sharks over 80 cm (31.5 in) 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 high and broad, with a pointed apex and a concave trailing margin; its origin lies roughly over the insertion (the rear of the fin base) of the pectoral fins. The second dorsal fin is relatively large and located about opposite the anal fin, which is about of equal size. There is no ridge between the dorsal fins. The caudal fin has a well-developed lower lobe and a ventral notch near the tip of the upper lobe. This species is bronze above and white below, which extends onto the flanks as a pale stripe. The pectoral fins, dorsal fins, lower caudal fin lobe, and sometimes the pelvic fins usually have black tips, while the upper caudal fin lobe darkens towards the trailing edge and the anal fin may be completely light. The fin markings tend to fade with age. The maximum known length is 1.7 m (5.6 ft).
Biology and ecology
The graceful shark feeds predominantly on bony fishes, with cephalopodCephalopod
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 and crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s being of minor importance. 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...
make up over 60% of its fish diet in the Gulf of Carpentaria
Gulf of Carpentaria
The Gulf of Carpentaria is a large, shallow sea enclosed on three sides by northern Australia and bounded on the north by the Arafura Sea...
. Like other members of its family, this species is viviparous: once the developing 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...
s exhaust their supply of yolk, the depleted 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...
is converted 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 to the mother. Off northern Australia, males and females likely mate every year in February, with ovulation
Ovulation
Ovulation is the process in a female's menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum . Ovulation also occurs in the estrous cycle of other female mammals, which differs in many fundamental ways from the menstrual cycle...
following shortly after. Females typically bear litters of three, though individuals gestating up to nine pups have been reported. The young are born in January or February, following a gestation period
Gestation period
For mammals the gestation period is the time in which a fetus develops, beginning with fertilization and ending at birth. The duration of this period varies between species.-Duration:...
of 9–10 months. Sexual maturity
Sexual maturity
Sexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...
is attained at a length of 1.1–1.2 m (3.6–3.9 ft) for both sexes. A known parasite of this species is a tapeworm in the genus Cathetocephalus.
Human interactions
Given its size, the graceful shark is potentially dangerous to humans, though no attacksShark attack
A shark attack is an attack on a human by a shark. Every year around 60 shark attacks are reported worldwide, although death is quite unusual. Despite the relative rarity of shark attacks, the fear of sharks is a common phenomenon, having been fueled by the occasional instances of serial attacks,...
have been recorded. It is caught incidentally
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...
by commercial fisheries in Thailand, India, Sri Lanka, and probably elsewhere, using gillnet
Gillnet
Gillnetting is a common fishing method used by commercial and artisanal fishermen of all the oceans and in some freshwater and estuary areas. The gillnet also is used by fisheries scientists to monitor fish populations. Because gillnets can be so effective their use is closely monitored and...
s and longlines. It is a minor component of shark catches off northern Australia, comprising around 1.5% and 0.2% of all sharks caught in gillnets and on longlines respectively in the mid-1980s. Catches in the region have declined from historical highs in the 1970s and 1980s, due to the departure of foreign fishing vessels following new gillnet regulations. The meat is sold fresh or dried and salted, the fins are shipped to East Asia
East Asia
East Asia or Eastern Asia is a subregion of Asia that can be defined in either geographical or cultural terms...
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...
, and the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
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. 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...
, noting that more biological and fishery information is needed.