Smalltooth sand tiger
Encyclopedia
The smalltooth sand tiger or bumpytail ragged-tooth (Odontaspis ferox) is a species of mackerel shark
in the family
Odontaspididae, with a patchy but worldwide distribution in tropical and warm temperate waters. They usually inhabit deepwater rocky habitats, though they are occasionally encountered in shallow water, and have been known to return to the same location year after year. This rare species is often mistaken for the much more common grey nurse shark
(Carcharias taurus), from which it can be distinguished by its first dorsal fin
, which is larger than the second and placed further forward. It grows to at least 4.1 m (13.5 ft) in length.
Very little is known of the biology and behavior of the smalltooth sand tiger. It is an active predator of benthic bony fishes, invertebrate
s, and cartilaginous fishes. This species is thought to be ovoviviparous with oophagous
embryo
s like other mackerel sharks
. In contrast to its formidable size and appearance, this shark is harmless, having never been known to behave aggressively towards humans. There is concern that its numbers are declining due to human activities in the Mediterranean and elsewhere, though existing data is inadequate for a full assessment of its conservation status.
Antoine Risso
in 1810, based on a specimen from Nice, France. In 1950, Gilbert Percy Whitley
described O. herbsti from Australian specimens, separating them from O. ferox on the basis of dentition and the absence of spots. Leonard Compagno
synonymized
the two species in 1984, as subsequently discovered Pacific specimens had blurred Whitley's distinguishing characters. The specific epithet ferox is Latin
for "fierce". Other common name
s for this shark include blue nurse shark, fierce shark, Herbst's nurse shark, and sand tiger shark.
A phylogenetic study based on mitochondrial DNA
, performed by Naylor et al. in 1997, suggests that the smalltooth sand tiger and its relative, the bigeye sand tiger
(O. noronhai), are more closely related to the thresher shark
s than to the grey nurse shark, to which it bears a strong resemblance. If true, this would indicate that the similarities between this species and the grey nurse shark arose as the result of convergent evolution
. Fossil
teeth belonging to the smalltooth sand tiger have been found from Lower Pliocene (5.3–3.6 Ma) deposits in Italy
and Venezuela
.
, it is known from the Bay of Biscay
south to Morocco
, including the Mediterranean Sea
, the Azores
, and the Canary Islands
. In the western Atlantic, it has been reported from off North Carolina
and Florida
(USA), the Yucatan Peninsula
(Mexico
), and Fernando de Noronha
(Brazil
). It occurs throughout the Indian Ocean
, from South Africa
, Madagascar
, and Tanzania
in the west to the Maldives
and the Southwest Indian Ridge
in the east. In the northern Pacific it is known from off Japan
, Hawaii
, California
, and Colombia
, and in the southern Pacific it is known from New Caledonia
, eastern Australia
, and New Zealand
.
Typically regarded as a deepwater species, the smalltooth sand tiger has been caught down to a depth of 880 m (2,900 ft). They are usually found near the bottom in rocky, boulder-strewn regions on continental shelves and the upper continental slope, as well as around submarine ridges and mountains. There are also reports of this species near the drop-offs of rocky or coral reef
s and in the upper layers of the open ocean
. In the Mediterranean, smalltooth sand tigers occur at depths less than 250 m (820 ft), including at depths accessible to divers. They have been seen swimming over sandy flats at Cocos Island
and Fernando de Noronha. The temperature range favored by this species is 6–20 °C (43–63 °F); in hot climates they are found below the thermocline
in cooler water.
s (as opposed to slit-like in the grey nurse shark), and lack nictitating membrane
s. The mouth is large and filled with projecting teeth. Each tooth has a narrow, tall central cusp flanked by 2-3 pairs of lateral cusplets. There are 48–56 tooth rows in the upper jaw and 36–46 tooth rows in the lower jaw; the front large teeth in the upper jaw are separated from the lateral teeth by 2–5 intermediate teeth.
The fins are broad-based and angular in shape. The first dorsal fin
is larger than the second and placed closer to the pectoral fins than the pelvic fins. The caudal fin is strongly asymmetrical with the upper lobe much longer than the lower. The coloration is gray to gray-brown above and lighter below. Juveniles are uniform in color with darker fin margins, while adults often exhibit dark spots or blotches that vary widely in pattern, size, and density. Coloration also appears to vary by region, with some individuals from the Mediterranean displaying a patchy, "piebald
" pattern. The smalltooth sand tiger attains a maximum length of 4.1 m (13.5 ft) and a maximum weight of 289 kg (637 lbs). There are unconfirmed reports of much larger individuals from Malpelo Island
off Colombia.
, which allows it to maintain neutral buoyancy
in the water column with minimal effort. At a location called "Shark Point" off Beirut
, Lebanon
, small groups of smalltooth sand tigers appear every summer on rocky reefs at a depth of 30–45 m (100–150 ft). The same individuals have been documented returning to this site year after year. Their purpose there is unknown, being speculated to relate to mating. When confronted, these sharks have been observed to stall, gape their mouths, turn around, and shake their tails towards the perceived threat.
Adult smalltooth sand tigers have no known predators, though they are bitten by cookiecutter shark
s (Isistius brasiliensis). A known parasite is the tapeworm Lithobothrium gracile, which infests the shark's spiral valve intestine
. The carcass of a 3.7 m (12.1 ft) long female found off Fuerteventura
in the Canary Islands contained a number of snubnosed eel
s (Simenchelys parasitica) inside her heart, body cavity, and back muscles. It is unknown whether the eels contributed to the shark's death.
(Sebastes spp.), invertebrate
s such as squid, shrimp, and possibly marine isopods, and cartilaginous fishes including rays
and chimaera
s. The largest known prey item taken by this species was a 1.3 m (4.3 ft) long kitefin shark
(Dalatias licha), found inside the stomach of a 2.9 m (9.5 ft) long male from New Caledonia.
that contained "hundreds of ova" in her right ovary
, which would support the embryos being oophagous
. Whether the embryos also cannibalize each other as in the grey nurse shark is unknown. The size at birth is estimated to be 1.0–1.1 m (3.3–3.6 ft). With a few recorded exceptions, juveniles are found in deep water and only adults are present above a depth of 200 m (660 ft); this may serve to reduce predation on young individuals by large, shallow-water predators such as the great white shark
(Carcharodon carcharias). Males mature at a length of 2.0–2.5 m (6.6–8.2 ft) and females at a length of 3.0–3.5 m (9.4–11.5 ft). Faint scars seen on some individuals may be related to courtship.
in gillnet
s, bottom trawls, and on longlines; most captures occur in the Mediterranean and off Japan. It is usually discarded when caught, except in Japan where the meat is consumed (though considered very inferior to the grey nurse shark
) and the liver oil
is utilized. The fins, jaws, and cartilage are also of value.
Discoveries, beginning in the 1970s, of smalltooth sand tigers in shallow water have raised urgent conservation concerns, as this species is apparently more vulnerable to human activity than previously believed. There is at present insufficient data for the International Union for Conservation of Nature (IUCN) to assess the worldwide conservation status of this species. It has been assessed as Vulnerable
in Australian waters, due to a decline of over 50% in catches off New South Wales
since the 1970s. Populations of this species in the Mediterranean are also believed to have declined, due to a combination of habitat degradation, overfishing
, pollution
, and human disturbance. The smalltooth sand tiger has been protected by the Australian government since 1984; this came about concurrently with protection for the grey nurse shark, which had been decimated in Australian waters, so as to prevent any claims of confusing one species for the other. However, these regulations have proven difficult to enforce.
Lamniformes
Lamniformes is an order of sharks commonly known as mackerel sharks . It includes some of the most familiar species of sharks, such as the great white shark, as well as more unusual representatives, such as the goblin shark and the megamouth shark.Members of the order are distinguished by...
in the 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...
Odontaspididae, with a patchy but worldwide distribution in tropical and warm temperate waters. They usually inhabit deepwater rocky habitats, though they are occasionally encountered in shallow water, and have been known to return to the same location year after year. This rare species is often mistaken for the much more common grey nurse shark
Grey nurse shark
The sand tiger shark or grey nurse shark is a species of shark that inhabits coastal waters worldwide. It lives very close to the shorelines and beaches of North America, hence the name, sand tiger shark. Despite a fearsome appearance and strong swimming abilities, it is a relatively placid and...
(Carcharias taurus), from which it can be distinguished by its 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 is larger than the second and placed further forward. It grows to at least 4.1 m (13.5 ft) in length.
Very little is known of the biology and behavior of the smalltooth sand tiger. It is an active predator of benthic bony fishes, invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s, and cartilaginous fishes. This species is thought to be ovoviviparous with oophagous
Oophagy
Oophagy , literally "egg eating", is the practice of embryos feeding on eggs produced by the ovary while still inside the mother's uterus. The word oophagy is formed from the classical Greek ᾠόν and classical Greek φᾱγεῖν ....
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 like other mackerel sharks
Lamniformes
Lamniformes is an order of sharks commonly known as mackerel sharks . It includes some of the most familiar species of sharks, such as the great white shark, as well as more unusual representatives, such as the goblin shark and the megamouth shark.Members of the order are distinguished by...
. In contrast to its formidable size and appearance, this shark is harmless, having never been known to behave aggressively towards humans. There is concern that its numbers are declining due to human activities in the Mediterranean and elsewhere, though existing data is inadequate for a full assessment of its conservation status.
Taxonomy and phylogeny
The smalltooth sand tiger was originally described as Squalus ferox by Italian-French naturalistNaturalist
Naturalist may refer to:* Practitioner of natural history* Conservationist* Advocate of naturalism * Naturalist , autobiography-See also:* The American Naturalist, periodical* Naturalism...
Antoine Risso
Antoine Risso
Giuseppe Antonio Risso , called Antoine Risso, was a Niçard naturalist.Risso was born in Nice, County of Nice, a part of the Duchy of Savoy, and studied under Giovanni Battista Balbis. He published , and . Risso's dolphin was named after him...
in 1810, based on a specimen from Nice, France. In 1950, Gilbert Percy Whitley
Gilbert 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...
described O. herbsti from Australian specimens, separating them from O. ferox on the basis of dentition and the absence of spots. 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,...
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...
the two species in 1984, as subsequently discovered Pacific specimens had blurred Whitley's distinguishing characters. The specific epithet ferox is Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
for "fierce". Other 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...
s for this shark include blue nurse shark, fierce shark, Herbst's nurse shark, and sand tiger shark.
A phylogenetic study based on mitochondrial DNA
Mitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...
, performed by Naylor et al. in 1997, suggests that the smalltooth sand tiger and its relative, the bigeye sand tiger
Bigeye sand tiger
The bigeye sand tiger is a species of mackerel shark in the family Odontaspididae, possibly found worldwide at depths of 60–1,000 m . It is extremely rare and poorly-known: despite intense fishing activity in many parts of its presumed range, only around 15 specimens have ever been captured...
(O. noronhai), are more closely related to the thresher shark
Thresher shark
Thresher sharks are large lamniform sharks of the family Alopiidae. Found in all temperate and tropical oceans of the world, the family contains three species all within the genus Alopias.-Taxonomy:...
s than to the grey nurse shark, to which it bears a strong resemblance. If true, this would indicate that the similarities between this species and the grey nurse shark arose as the result 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...
. Fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
teeth belonging to the smalltooth sand tiger have been found from Lower Pliocene (5.3–3.6 Ma) deposits in Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
and Venezuela
Venezuela
Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...
.
Distribution and habitat
Smalltooth sand tigers have been caught at widely scattered locations throughout the world, indicating a possibly circumtropical distribution. In the eastern 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 is known from the Bay of Biscay
Bay of Biscay
The Bay of Biscay is a gulf of the northeast Atlantic Ocean located south of the Celtic Sea. It lies along the western coast of France from Brest south to the Spanish border, and the northern coast of Spain west to Cape Ortegal, and is named in English after the province of Biscay, in the Spanish...
south to Morocco
Morocco
Morocco , officially the Kingdom of Morocco , is a country located in North Africa. It has a population of more than 32 million and an area of 710,850 km², and also primarily administers the disputed region of the Western Sahara...
, including 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...
, the Azores
Azores
The Archipelago of the Azores is composed of nine volcanic islands situated in the middle of the North Atlantic Ocean, and is located about west from Lisbon and about east from the east coast of North America. The islands, and their economic exclusion zone, form the Autonomous Region of the...
, and the Canary Islands
Canary Islands
The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...
. In the western Atlantic, it has been reported from off 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...
and Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
(USA), the Yucatan Peninsula
Yucatán Peninsula
The Yucatán Peninsula, in southeastern Mexico, separates the Caribbean Sea from the Gulf of Mexico, with the northern coastline on the Yucatán Channel...
(Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
), and Fernando de Noronha
Fernando de Noronha
Fernando de Noronha is an archipelago of 21 islands and islets in the Atlantic Ocean, offshore from the Brazilian coast. The main island has an area of and had a population of 3,012 in the year 2010...
(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...
). It occurs throughout 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...
, 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...
, Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
, and Tanzania
Tanzania
The United Republic of Tanzania is a country in East Africa bordered by Kenya and Uganda to the north, Rwanda, Burundi, and the Democratic Republic of the Congo to the west, and Zambia, Malawi, and Mozambique to the south. The country's eastern borders lie on the Indian Ocean.Tanzania is a state...
in the west to the Maldives
Maldives
The Maldives , , officially Republic of Maldives , also referred to as the Maldive Islands, is an island nation in the Indian Ocean formed by a double chain of twenty-six atolls oriented north-south off India's Lakshadweep islands, between Minicoy Island and...
and the Southwest Indian Ridge
Southwest Indian Ridge
The Southwest Indian Ridge is a divergent tectonic plate boundary located along the floor of the southwest Indian Ocean. It separates the African Plate to the north from the Antarctic Plate to the south....
in the east. In the northern Pacific it is known from 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...
, Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
, California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, and Colombia
Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...
, and in the southern Pacific it is known from New Caledonia
New Caledonia
New Caledonia is a special collectivity of France located in the southwest Pacific Ocean, east of Australia and about from Metropolitan France. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre, the Loyalty Islands, the Belep archipelago, the Isle of...
, eastern 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 New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
.
Typically regarded as a deepwater species, the smalltooth sand tiger has been caught down to a depth of 880 m (2,900 ft). They are usually found near the bottom in rocky, boulder-strewn regions on continental shelves and the upper continental slope, as well as around submarine ridges and mountains. There are also reports of this species near the drop-offs of rocky or coral reef
Coral reef
Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps...
s and in the upper layers of the open ocean
Pelagic zone
Any water in a sea or lake that is not close to the bottom or near to the shore can be said to be in the pelagic zone. The word pelagic comes from the Greek πέλαγος or pélagos, which means "open sea". The pelagic zone can be thought of in terms of an imaginary cylinder or water column that goes...
. In the Mediterranean, smalltooth sand tigers occur at depths less than 250 m (820 ft), including at depths accessible to divers. They have been seen swimming over sandy flats at Cocos Island
Cocos Island
Cocos Island is an uninhabited island located off the shore of Costa Rica . It constitutes the 11th district of Puntarenas Canton of the province of Puntarenas. It is one of the National Parks of Costa Rica...
and Fernando de Noronha. The temperature range favored by this species is 6–20 °C (43–63 °F); in hot climates they are found below the thermocline
Thermocline
A thermocline is a thin but distinct layer in a large body of fluid , in which temperature changes more rapidly with depth than it does in the layers above or below...
in cooler water.
Description
The smalltooth sand tiger has a bulky body with a long, bulbous, slightly flattened snout. The eyes are medium-sized, with large round pupilPupil
The pupil is a hole located in the center of the iris of the eye that allows light to enter the retina. It appears black because most of the light entering the pupil is absorbed by the tissues inside the eye. In humans the pupil is round, but other species, such as some cats, have slit pupils. In...
s (as opposed to slit-like in the grey nurse shark), and lack nictitating membrane
Nictitating 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. The mouth is large and filled with projecting teeth. Each tooth has a narrow, tall central cusp flanked by 2-3 pairs of lateral cusplets. There are 48–56 tooth rows in the upper jaw and 36–46 tooth rows in the lower jaw; the front large teeth in the upper jaw are separated from the lateral teeth by 2–5 intermediate teeth.
The fins are broad-based and angular in shape. 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 larger than the second and placed closer to the pectoral fins than the pelvic fins. The caudal fin is strongly asymmetrical with the upper lobe much longer than the lower. The coloration is gray to gray-brown above and lighter below. Juveniles are uniform in color with darker fin margins, while adults often exhibit dark spots or blotches that vary widely in pattern, size, and density. Coloration also appears to vary by region, with some individuals from the Mediterranean displaying a patchy, "piebald
Piebald
A piebald or pied animal is one that has a spotting pattern of large unpigmented, usually white, areas of hair, feathers, or scales and normally pigmented patches, generally black. The colour of the animal's skin underneath its coat is also pigmented under the dark patches and unpigmented under...
" pattern. The smalltooth sand tiger attains a maximum length of 4.1 m (13.5 ft) and a maximum weight of 289 kg (637 lbs). There are unconfirmed reports of much larger individuals from Malpelo Island
Malpelo Island
Malpelo Island is an island located from Colombia's Pacific coast, and approximately from Panama's coast. It has a land area of . It is uninhabited except for a small military post manned by the Colombian Army, which was established in 1986. Visitors need a written permit from the Colombian...
off Colombia.
Biology and ecology
The smalltooth sand tiger is a strong-swimming shark that may be encountered singly or in aggregations of up to five individuals. Catch records suggest that this species may cover long distances in oceanic waters along underwater ridges or "hopping" between seamounts. It has a very large, oily liverLiver
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...
, which allows it to maintain neutral buoyancy
Buoyancy
In physics, buoyancy is a force exerted by a fluid that opposes an object's weight. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the...
in the water column with minimal effort. At a location called "Shark Point" off Beirut
Beirut
Beirut is the capital and largest city of Lebanon, with a population ranging from 1 million to more than 2 million . Located on a peninsula at the midpoint of Lebanon's Mediterranean coastline, it serves as the country's largest and main seaport, and also forms the Beirut Metropolitan...
, Lebanon
Lebanon
Lebanon , officially the Republic of LebanonRepublic of Lebanon is the most common term used by Lebanese government agencies. The term Lebanese Republic, a literal translation of the official Arabic and French names that is not used in today's world. Arabic is the most common language spoken among...
, small groups of smalltooth sand tigers appear every summer on rocky reefs at a depth of 30–45 m (100–150 ft). The same individuals have been documented returning to this site year after year. Their purpose there is unknown, being speculated to relate to mating. When confronted, these sharks have been observed to stall, gape their mouths, turn around, and shake their tails towards the perceived threat.
Adult smalltooth sand tigers have no known predators, though they are bitten by cookiecutter shark
Cookiecutter shark
The cookiecutter shark , also called the cigar shark, is a species of small dogfish shark in the family Dalatiidae. This shark occurs in warm, oceanic waters worldwide, particularly near islands, and has been recorded from as deep as . It migrates vertically up to every day, approaching the...
s (Isistius brasiliensis). A known parasite is the tapeworm Lithobothrium gracile, which infests the shark's spiral valve intestine
Spiral valve
A spiral valve is the lower portion of the intestine of some sharks, rays, skates and bichirs. A modification of the ileum, the spiral valve is internally twisted or coiled to increase the surface area of the intestine, to increase nutrient absorption....
. The carcass of a 3.7 m (12.1 ft) long female found off Fuerteventura
Fuerteventura
Fuerteventura , a Spanish island, is one of the Canary Islands, in the Atlantic Ocean off the coast of Africa. It is situated at 28°20' north, 14°00' west. At 1,660 km² it is the second largest of the Canary Islands, after Tenerife...
in the Canary Islands contained a number of snubnosed eel
Snubnosed eel
The snubnosed eel, Simenchelys parasitica, also known as the pug-nosed eel, slime eel, or snub-nose parasitic eel, is a species of deep-sea eel and the only member of its genus...
s (Simenchelys parasitica) inside her heart, body cavity, and back muscles. It is unknown whether the eels contributed to the shark's death.
Feeding
Compared to the grey nurse shark, the dentition of the smalltooth sand tiger is less robust and lacks specialized cutting and crushing teeth, suggesting that it tends to tackle smaller prey. The diet of the smalltooth sand tiger consists of bottom-dwelling bony fishes such as rockfishRockfish
Rockfish may refer to one of the following fishes:* One of several species in the Sebastes genus of the Sebastidae family, including the Shortraker rockfish, Rougheye rockfish, Blue rockfish, Yellow tail rockfish and many others....
(Sebastes spp.), invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s such as squid, shrimp, and possibly marine isopods, and cartilaginous fishes including rays
Batoidea
Batoidea is a superorder of cartilaginous fish commonly known as rays and skates, containing more than 500 described species in thirteen families...
and chimaera
Chimaera
Chimaeras are cartilaginous fish in the order Chimaeriformes, known informally as ghost sharks, ratfish , spookfish , or rabbitfishes...
s. The largest known prey item taken by this species was a 1.3 m (4.3 ft) long kitefin shark
Kitefin shark
The kitefin shark or seal shark is a species of dogfish shark in the family Dalatiidae, and the only species in its genus. It is found sporadically around the world, usually close to the sea floor at depths of . With a sizable oil-filled liver to maintain neutral buoyancy, this shark is able to...
(Dalatias licha), found inside the stomach of a 2.9 m (9.5 ft) long male from New Caledonia.
Life history
No pregnant smalltooth sand tigers have ever been found; this species is presumed to be ovoviviparous as in other mackerel sharks. Villaviencio-Garayzar (1996) described a 3.6 m (11.8 ft) female from the Gulf of CaliforniaGulf of California
The Gulf of California is a body of water that separates the Baja California Peninsula from the Mexican mainland...
that contained "hundreds of ova" in her right ovary
Ovary
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...
, which would support the embryos being oophagous
Oophagy
Oophagy , literally "egg eating", is the practice of embryos feeding on eggs produced by the ovary while still inside the mother's uterus. The word oophagy is formed from the classical Greek ᾠόν and classical Greek φᾱγεῖν ....
. Whether the embryos also cannibalize each other as in the grey nurse shark is unknown. The size at birth is estimated to be 1.0–1.1 m (3.3–3.6 ft). With a few recorded exceptions, juveniles are found in deep water and only adults are present above a depth of 200 m (660 ft); this may serve to reduce predation on young individuals by large, shallow-water predators such as the great white shark
Great white shark
The great white shark, scientific name Carcharodon carcharias, also known as the great white, white pointer, white shark, or white death, is a large lamniform shark found in coastal surface waters in all major oceans. It is known for its size, with the largest individuals known to have approached...
(Carcharodon carcharias). Males mature at a length of 2.0–2.5 m (6.6–8.2 ft) and females at a length of 3.0–3.5 m (9.4–11.5 ft). Faint scars seen on some individuals may be related to courtship.
Human interactions
Encounters with divers have shown that, despite their size, smalltooth sand tigers are docile and do not react aggressively even when closely approached. This species is taken as bycatchBycatch
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...
in 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, bottom trawls, and on longlines; most captures occur in the Mediterranean and off Japan. It is usually discarded when caught, except in Japan where the meat is consumed (though considered very inferior to the grey nurse shark
Grey nurse shark
The sand tiger shark or grey nurse shark is a species of shark that inhabits coastal waters worldwide. It lives very close to the shorelines and beaches of North America, hence the name, sand tiger shark. Despite a fearsome appearance and strong swimming abilities, it is a relatively placid and...
) and 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 utilized. The fins, jaws, and cartilage are also of value.
Discoveries, beginning in the 1970s, of smalltooth sand tigers in shallow water have raised urgent conservation concerns, as this species is apparently more vulnerable to human activity than previously believed. There is at present insufficient data for the International Union for Conservation of Nature (IUCN) to assess the worldwide conservation status of this species. It has been assessed as 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 Australian waters, due to a decline of over 50% in catches off New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
since the 1970s. Populations of this species in the Mediterranean are also believed to have declined, due to a combination of habitat degradation, overfishing
Overfishing
Overfishing occurs when fishing activities reduce fish stocks below an acceptable level. This can occur in any body of water from a pond to the oceans....
, pollution
Pollution
Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...
, and human disturbance. The smalltooth sand tiger has been protected by the Australian government since 1984; this came about concurrently with protection for the grey nurse shark, which had been decimated in Australian waters, so as to prevent any claims of confusing one species for the other. However, these regulations have proven difficult to enforce.