Sand tiger shark

The sand tiger shark (Carcharias taurus), grey nurse shark, spotted ragged-tooth shark, or blue-nurse sand tiger is a species of shark that inhabits subtropical and temperate waters worldwide. It inhabits the continental shelf, from sandy shorelines (hence the name sand tiger shark) and submerged reefs to a depth of around 191 m (627 ft).[2] They dwell in the waters of Japan, Australia, South Africa, the Mediterranean and the east coasts of North and South America. Despite its name, it is not related to the tiger shark Galeocerdo cuvier; however, it is a cousin of the great white shark Carcharodon carcharias.

Despite its fearsome appearance and strong swimming ability, it is a relatively placid and slow-moving shark with no confirmed human fatalities. This species has a sharp, pointy head, and a bulky body. The sand tiger's length can reach 3.2 m (10.5 ft).[3] They are grey with reddish-brown spots on their backs. Shivers (groups) have been observed to hunt large schools of fish. Their diet consists of bony fish, crustaceans, squid, skates and other sharks. Unlike other sharks, the sand tiger can gulp air from the surface, allowing it to be suspended in the water column with minimal effort. During pregnancy, the most developed embryo will feed on its siblings, a reproductive strategy known as intrauterine cannibalism i.e. "embryophagy" or, more colorfully, adelphophagy—literally "eating one's brother". The sand tiger is categorized as vulnerable on the International Union for Conservation of Nature Red List. It is the most widely kept large shark in public aquariums owing to its tolerance for captivity.

Sand tiger shark
Carcharias taurus SI
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Order: Lamniformes
Family: Odontaspididae
Genus: Carcharias
Species:
C. taurus
Binomial name
Carcharias taurus
Carcharias taurus distmap
Range of the sand tiger shark
Synonyms

Carcharias tricuspidatus Day, 1878

Taxonomy

The sand tiger shark's description as Carcharias taurus by Constantine Rafinesque came from a specimen caught off the coast of Sicily. Carcharias taurus means "bull shark". This taxonomic classification has been long disputed. Twenty-seven years after Rafinesque's original description the German biologists Müller and Henle changed the genus name from C. taurus to Triglochis taurus. The following year, Swiss-American naturalist Jean Louis Rodolphe Agassiz reclassified the shark as Odontaspis cuspidata based on examples of fossilized teeth. Agassiz's name was used until 1961 when three palaeontologists and ichthyologists, W. Tucker, E. I. White, and N. B. Marshall, requested that the shark be returned to the genus Carcharias. This request was rejected and Odontaspis was approved by the International Code of Zoological Nomenclature (ICZN). When experts concluded that taurus belongs after Odontaspis, the name was changed to Odontaspis taurus. In 1977, Compagno and Follet challenged the Odontaspis taurus name and substituted Eugomphodus, a somewhat unknown classification, for Odontaspis. Many taxonomists questioned his change, arguing that there was no significant difference between Odontaspis and Carcharias. After changing the name to Eugomphodus taurus, Compagno successfully advocated in establishing the shark's current scientific name as Carcharias taurus. The ICZN approved this name, and today it is used among biologists.[2]

Common names

Because the sand tiger shark is worldwide in distribution, it has many common names. The term "sand tiger shark" actually refers to four different sand tiger shark species in the family Odontaspididae. Furthermore, the name creates confusion with the tiger shark Galeocerdo cuvier, which is not related to the sand tiger. The grey nurse shark, the name used in Australia and the United Kingdom, is the second-most used name for the shark, and in India it is known as blue-nurse sand tiger. However, there are unrelated nurse sharks in the family Ginglymostomatidae. The most unambiguous and descriptive English name is probably the South African one, spotted ragged-tooth shark.[2][4]

Identification

There are four species of sand tiger sharks[2]

  1. The sand tiger shark Carcharias taurus
  2. The Indian sand tiger shark Carcharias tricuspidatus. Very little is known about this species which, described before 1900, is probably the same as (a synonym of) the sand tiger C. taurus[2]
  3. The small-toothed sand tiger shark Odontaspis ferox. This species has a worldwide distribution, is seldom seen but normally inhabits deeper water than does C. taurus.
  4. The large-eyed sand tiger shark Odontaspis noronhai, a deep water shark of the Americas, of which little is known.
Sandtigersharkspecies
Diagram indicating the differences between C. taurus and O. ferox

The most likely problem when identifying the sand tiger shark is when in the presence of either of the two species of Odontaspis. Firstly, the sand tiger is usually spotted, especially on the hind half of the body. However, there are several other differences that are probably more reliable:

  1. The bottom part of the caudal fin (tail fin) of the sand tiger is smaller;
  2. The second (i.e. hind) dorsal fin of the sand tiger is almost as large as the first (i.e. front) dorsal fin.
  3. The first (i.e. front) dorsal fin of the sand tiger is relatively non-symmetric;
  4. The first (i.e. front) dorsal fin of the sand tiger is closer to the pelvic fin than to the pectoral fin (i.e. the first dorsal fin is positioned further backwards in the case of the sand tiger);

Description

Adult sand tigers range from 2 m (6.6 ft) to 3.2 m (10.5 ft) in length and 91 kg (201 lb) to 159 kg (351 lb) in weight.[5] The head is pointy, as opposed to round, while the snout is flattened with a conical shape. Its body is stout and bulky and its mouth extends beyond the eyes. The eyes of the sand tiger shark are small, lacking eyelids.[2] A sand tiger usually swims with its mouth open displaying three rows of protruding, smooth-edged, sharp-pointed teeth.[6] The males have grey claspers with white tips located on the underside of their body. The caudal fin is elongated with a long upper lobe (i.e. strongly heterocercal). They have two large, broad-based grey dorsal fins set back beyond the pectoral fins.[2] The sand tiger shark has a grey-brown back and pale underside. Adults tend to have reddish-brown spots scattered, mostly on the hind part of the body.[6] In August 2007, an albino specimen was photographed off South West Rocks, Australia.[7] The teeth of these sharks have no transverse serrations (as have many other sharks) but they have a large, smooth main cusp with a tiny cusplet on each side of the main cusp.[2] The upper front teeth are separated from the teeth on the side of the mouth by small intermediate teeth.

Grey nurse shark 2

Snout and mouth of sand tiger shark, showing protruding teeth and small eyes

Carcharias taurus eye

Eye

Carcharias taurus jaws

Jaws

Carcharias taurus central teeth2

Central teeth

Carcharias taurus teeth

Individual teeth

Habitat and range

Geographical range

Sand tiger sharks roam the epipelagic and mesopelagic regions of the ocean,[8] sandy coastal waters, estuaries, shallow bays, and rocky or tropical reefs, at depths of up to 190 m (623 ft).

The sand tiger shark can be found in the Atlantic, Pacific and Indian Oceans, and in the Mediterranean and Adriatic Seas. In the Western Atlantic Ocean, it is found in coastal waters around from the Gulf of Maine to Florida, in the northern Gulf of Mexico around the Bahamas and Bermuda, and from southern Brazil to northern Argentina. It is also found in the eastern Atlantic Ocean from the Mediterranean Sea to the Canary Islands, at the Cape Verde islands, along the coasts of Senegal and Ghana, and from southern Nigeria to Cameroon. In the western Indian Ocean, the shark ranges from South Africa to southern Mozambique, but excluding Madagascar. The sand tiger shark has also been sighted in the Red Sea and may be found as far east as India. In the western Pacific, it has been sighted in the waters around the coasts of Japan and Australia, but not around New Zealand.[1]

RaggyMap2
Annual movements of sand tiger sharks off South Africa and Australia

Annual migration

Sand tigers in South Africa and Australia undertake an annual migration that may cover more than 1,000 km (620 mi).[8] They pup during the summer in relatively cold water (temperature ca. 16 °C [61 °F]). After parturition, they swim northwards toward sites where there are suitable rocks or caves, often at a water depth ca. 20 m (66 ft), where they mate during and just after the winter.[9] Mating normally takes place at night. After mating, they swim further north to even warmer water where gestation takes place. In the Autumn they return southwards to give birth in cooler water. This round trip may encompass as much as 3,000 km (1,900 mi). The young sharks do not take part in this migration, but they are absent from the normal birth grounds during winter: it is thought that they move deeper into the ocean.[8] At Cape Cod (USA), juveniles move away from coastal areas when water temperatures decreases below 16 °C and day length decreases to less than 12 h.[10] Juveniles, however, return to their usual summer haunts and as they become mature they start larger migratory movements.

Behavior

Hunting

The sand tiger shark is a nocturnal feeder. During the day, they take shelter near rocks, overhangs, caves and reefs often at relatively shallow depths (<20 m). This is the typical environment where divers encounter sand tigers, hovering just above the bottom in large sandy gutters and caves.[11] However, at night they leave the shelter and hunt over the ocean bottom, often ranging far from their shelter.[12] Sand tigers hunt by stealth. It is the only shark known to gulp air and store it in the stomach, allowing the shark to maintain near-neutral buoyancy which helps it to hunt motionlessly and quietly.[2] Aquarium observations indicate that when it comes close enough to a prey item, it grabs with a quick sideways snap of the prey. The sand tiger shark has been observed to gather in hunting groups when preying upon large schools of fish.[2]

Diet

Mustelus mustelus2
A bottom-living smooth-hound shark, one of the important prey items of sand tiger sharks

The majority of prey items of sand tigers are demersal (i.e. from the sea bottom), suggesting that they hunt extensively on the sea bottom as far out as the continental shelf. Bony fish (teleosts) form about 60% of sand tigers food, the remaining prey comprising sharks and skates. In Argentina, the prey includes mostly demersal fishes, e.g. the striped weakfish (Cynoscion guatucupa). The most important elasmobranch prey is the bottom-living smooth-hound shark (Mustelus sp.). Benthic (i.e. free-swimming) rays and skates are also taken.[13] Stomach content analysis indicates that smaller sand tigers mainly focus on the sea bottom and as they grow larger they start to take more benthic prey. This perspective of the diet of sand tigers is consistent with similar observations in the north west Atlantic[14] and in South Africa where large sand tigers capture a wider range of shark and skate species as prey, from the surf zone to the continental shelf, indicating the opportunistic nature of sand tiger feeding.[12] Off South Africa, sand tigers less than 2 m (6.6 ft) in length prey on fish about a quarter of their own length; however, large sand tigers capture prey up to about half of their own length.[12] The prey items are usually swallowed as three or four chunks.[13]

Courtship and mating

Mating occurs around the months of March and April in the northern hemisphere and during August–October in the southern hemisphere. The courtship and mating of sand tigers has been best documented from observations in large aquaria. In Oceanworld, Sydney, the females tended to hover just above the sandy bottom ("shielding") when they were receptive.[15] This prevented males from approaching from underneath towards their cloaca. Often there is more than one male close by with the dominant one remaining close to the female, intimidating others with an aggressive display in which the dominant shark closely follows the tail of the subordinate, forcing the subordinate to accelerate and swim away. The dominant male snaps at smaller fish of other species. The male approaches the female and the two sharks protect the sandy bottom over which they interact. Strong interest of the male is indicated by superficial bites in the anal and pectoral fin areas of the female. The female responds with superficial biting of the male. This behaviour continues for several days during which the male patrols the area around the female. The male regularly approaches the female in "nosing" behaviour to "smell" the cloaca of the female. If she is ready, she swims off with the male, while both partners contort their bodies so that the right clasper of the male enters the cloaca of the female. The male bites the base of her right pectoral fin, leaving scars that are easily visible afterwards. After one or two minutes, mating is complete and the two separate. Females often mate with more than one male.[16] Females mate only every second or third year.[17] After mating, the females remain behind, while the males move off to seek other areas to feed,[17] resulting in many observations of sand tiger populations comprising almost exclusively females.

Reproduction and growth

Growth curve for raggedtooth shark
Growth curve for sand tiger sharks in the north Atlantic

Reproduction

The reproductive pattern is similar to that of many of the Lamnidae, the shark family to which sand tigers belong. Female sand tigers have two uterine horns that, during early embryonic development, may have as many as 50 embryos that obtain nutrients from their yolk sacs and possibly consume uterine fluids. When one of the embryos reaches some 10 cm (4 in) in length, it eats all the smaller embryos so that only one large embryo remains in each uterine horn, a process called intrauterine cannibalism i.e. "embryophagy" or, more colorfully, adelphophagy—literally "eating one's brother."[2][16] While multiple male sand tigers commonly fertilize a single female, adelphophagy sometimes excludes all but one of them from gaining offspring. These surviving embryos continue to feed on a steady supply of unfertilised eggs.[18] After a lengthy labour, the female gives birth to 1 m (3.3 ft) long, fully independent offspring. The gestation period is approximately eight to twelve months. These sharks give birth only every second or third year,[17] resulting in an overall mean reproductive rate of less than one pup per year, one of the lowest reproductive rates for sharks.

Growth

In the north Atlantic, sand tiger sharks are born about 1 m in length. During the first year, they grow about 27 cm to reach 1.3 m. After that, the growth rate decreases by about 2.5 cm each year until it stabilises at about 7 cm/y.[19] Males reach sexual maturity at an age of five to seven years and approximately 1.9 m (6.2 ft) in length. Females reach maturity when approximately 2.2 m (7.2 ft) long at about seven to ten years of age.[19] They are normally not expected to reach lengths much over 3 m. In the informal media, such as YouTube, there have been several reports of sand tigers around 5 m long, but none of these have been verified scientifically.

Interaction with humans

Attacks on humans

The sand tiger is often associated with being vicious or deadly, due to its relatively large size and sharp, protruding teeth that point outward from its jaws; however, these sharks are quite docile, and are not a threat to humans. Their mouths are not large enough to cause a human fatality. Sand tigers roam the surf, sometimes in close proximity to humans, and there have been only a few instances of unprovoked sand tiger shark attacks on humans, usually associated with spear fishing, line fishing, or shark feeding.[5] As of 2013, the database of Shark Attack Survivors does not list any fatalities due to sand tiger sharks.[20] When the sharks become aggressive, they tend to steal fish or bait from fishing lines rather than attack humans. Owing to its large size and docile temperament, the sand tiger is commonly displayed in aquariums around the world.[5]

Nets around swimming beaches

In Australia and South Africa, one of the common practices in beach holiday areas is to erect shark nets around the beaches frequently used by swimmers. These nets are erected some 400 m (1,300 ft) from the shore and act as gill nets that trap incoming sharks:[21] this was the norm until about 2005. In South Africa, the mortality of sand tiger sharks caused a significant decrease in the length of these animals and it was concluded that the shark nets pose a significant threat to this species that has a very low reproductive rate[22] Before 2000, these nets snagged about 200 sand tiger sharks per year in South Africa, of which only about 40% survived and were released alive.[23] The efficiency of shark nets for the prevention of unprovoked shark attacks on bathers has been questioned, and since 2000 there has been a reduced use of these nets and alternative approaches are being developed.

Carcharias taurus newport
Sand shark in the Newport Aquarium

Competition for food with humans

In Argentina, the prey items of sand tigers largely coincided with important commercial fisheries targets.[13] Humans affect sand tiger food availability and the sharks, in turn, compete with humans for food that, in turn, has already been heavily exploited by the fisheries industry. The same applies to the bottom-living sea catfish (Galeichthys feliceps), a fisheries resource off the South African coast.[12]

Effects of scuba divers

Sand tiger sharks are often the targets of scuba divers who wish to observe or photograph these animals. A study near Sydney in Australia found that the behaviour of the sharks is affected by the proximity of scuba divers.[24] Diver activity affects the aggregation, swimming and respiratory behaviour of sharks, but only at short time scales. The group size of scuba divers was less important in affecting sand tiger behaviour than the distance within which they approached the sharks. Divers approaching to within 3 m of sharks affected their behaviour but after the divers had retreated, the sharks resumed normal behaviour. Other studies indicate sand tiger sharks can be indifferent to divers.[25] Scuba divers are normally compliant when it comes to observing the Australian regulations for shark diving.[26] In North America World War II shipwrecks off the coast of North Carolina provide both a habitat for the sharks and the opportunity for close encounters between sharks and divers.[27]

In captivity

Its large and menacing appearance, combined with its relative placidity, has made the sand tiger shark among the most popular shark species to be displayed in public aquaria.[28] However, as with all large sharks, keeping them in captivity is not without its difficulties. Sand tiger sharks have been found to be highly susceptible to developing spinal deformities, with as many as one in every three captive sharks being affected, giving them a hunched appearance.[29] These deformities have been hypothesized to be correlated to both the size and shape of their tank.[30] If the tank is too small, the sharks have to spend more time actively swimming than they would in the wild, where they have space to glide. Also, sharks in small, circular tanks often spend most of their time circling along the edges in only one direction, causing asymmetrical stress on their bodies.

Threats and conservation status

Threats

There are several factors contributing to the decline in the population of the sand tigers. Sand tigers reproduce at an unusually low rate, due to the fact that they do not have more than two pups at a time and because they breed only every second or third year. This shark is a highly prized food item in the western northern Pacific, off Ghana and off India and Pakistan where they are caught by fishing trawlers, although they are more commonly caught with a fishing line.[2] Sand tigers' fins are a popular trade item in Japan.[1] Off North America, it is fished for its hide and fins. Shark liver oil is a popular product in cosmetic products such as lipstick.[6] It is sought by anglers in fishing competitions in South Africa and some other countries. In Australia it has been reduced in numbers by spear fishers using poison and where it is now protected.[2] It is also prized as an aquarium exhibit in the United States, Europe, Australia and South Africa because of its docile and hardy nature.[2] Thus, overfishing is a major contributor to the population decline. All indications show that the world population in sand tigers has been reduced significantly in size since 1980.[2] Many sand tigers are caught in shark nets, and then either strangled or taken by fishermen.[1] Estuaries along the United States of America's eastern Atlantic coast houses many of the young sand tiger sharks. These estuaries are susceptible to non-point source pollution that is harmful to the pups.[6] In Eastern Australia, the breeding population was estimated to be fewer than 400 reproductively mature animals, a number believed to be too small to sustain a healthy population.[31]

Conservation status

This species is therefore listed as vulnerable on the International Union for Conservation of Nature Red List,[1] and as endangered under Queensland's Nature Conservation Act 1992. It is a U.S. National Marine Fisheries Service [Species of Concern], which are those species that the U.S. Government’s National Oceanic and Atmospheric Administration, National Marine Fisheries Service (NMFS), has some concerns regarding status and threats, but for which insufficient information is available to indicate a need to list the species under the U.S. Endangered Species Act. According to the National Marine Fisheries Service, any shark caught must be released immediately with minimal harm, and is considered a prohibited species, making it illegal to harvest any part of the sand tiger shark on the United States' Atlantic coast.[6]

A recent report from the PEW Charitable Trusts suggests that a new management approach used for large mammals that have suffered population declines could hold promise for sharks. Because of the life-history characteristics of sharks, conventional fisheries management approaches, such as reaching maximum sustainable yield, may not be sufficient to rebuild depleted shark populations. Some of the more stringent approaches used to reverse declines in large mammals may be appropriate for sharks, including prohibitions on the retention of the most vulnerable species and regulation of international trade.[32]

References

  1. ^ a b c d e Pollard, D. & Smith, A. (2009). "Carcharias taurus". The IUCN Red List of Threatened Species. IUCN. 2009: e.T3854A10132481. doi:10.2305/IUCN.UK.2009-2.RLTS.T3854A10132481.en. Retrieved 15 January 2018.
  2. ^ a b c d e f g h i j k l m n o Compagno, L. J. V. (1984). FA0 Species Catalogue, Vol. 4. Sharks of the World. An annotated and illustrated catalogue of shark species known to date. Part 1, "Hexanchiformes to Lamniformes", FAO Fisheries Synopsis, No. 125, ISBN 92-5-101384-5.
  3. ^ "FLMNH Ichthyology Department: Sandtiger Shark". ufl.edu.
  4. ^ "Common names of Carcharias taurus". FishBase. 2011. Retrieved December 4, 2011.
  5. ^ a b c "Sand Tiger Shark". National Geographic Society. 2009. Retrieved October 26, 2011.
  6. ^ a b c d e "Sand tiger shark" (PDF). NOAA National Marine Fisheries Service. 2011. Retrieved November 28, 2011.
  7. ^ Williams, Samantha (8 August 2007). "Rare albino shark rules deep". thetelegraph.com.au.
  8. ^ a b c Dicken, M. L.; Booth, A. J.; Smale, M. J.; Cliff, G. (2007). "Spatial and seasonal distribution patterns of juvenile and adult raggedtooth sharks (Carcharias taurus) tagged off the east coast of South Africa" (PDF). Marine and Freshwater Research. 58: 127. doi:10.1071/MF06018.
  9. ^ Bansemer, C. S.; Bennett, M. B. (2011). "Sex- and maturity-based differences in movement and migration patterns of grey nurse shark, Carcharias taurus, along the eastern coast of Australia". Marine and Freshwater Research. 62 (6): 596. doi:10.1071/MF10152.
  10. ^ Kneebone, J.; Chisholm, J.; Skomal, G. B. (2012). "Seasonal residency, habitat use, and site fidelity of juvenile sand tiger sharks Carcharias taurus in a Massachusetts estuary". Marine Ecology Progress Series. 471: 165. doi:10.3354/meps09989.
  11. ^ Bray, Dianne J. (2011) "Greynurse Shark, Carcharias taurus", in Fishes of Australia, accessed 26 Aug 2014, http://www.fishesofaustralia.net.au/home/species/3285
  12. ^ a b c d Smale, M. J. (2005). "The diet of the ragged-tooth shark Carcharias taurus Rafinesque 1810 in the Eastern Cape, South Africa" (PDF). African Journal of Marine Science. 27: 331–335. doi:10.2989/18142320509504091. Archived from the original (PDF) on 2012-04-02. Retrieved 2011-09-10.
  13. ^ a b c Lucifora, L. O.; García, V. B.; Escalante, A. H. (2009). "How can the feeding habits of the sand tiger shark influence the success of conservation programs?". Animal Conservation. 12 (4): 291. doi:10.1111/j.1469-1795.2009.00247.x.
  14. ^ Gelsleichter, J.; Musick, J. A.; Nichols, S. (1999). "Food habits of the smooth dogfish, Mustelus canis, dusky shark, Carcharhinus obscurus, Atlantic sharpnose shark, Rhizoprionodon terraenovae, and the sand tiger, Carcharias taurus, from the northwest Atlantic Ocean". Environmental Biology of Fishes. 54 (2): 205. doi:10.1023/A:1007527111292.
  15. ^ Gordon, I. (1993). "Pre-copulatory behaviour of captive sandtiger sharks, Carcharias taurus". Environmental Biology of Fishes. 38: 159–164. doi:10.1007/BF00842912.
  16. ^ a b Chapman, D. D.; Wintner, S. P.; Abercrombie, D. L.; Ashe, J.; Bernard, A. M.; Shivji, M. S.; Feldheim, K. A. (2013). "The behavioural and genetic mating system of the sand tiger shark, Carcharias taurus, an intrauterine cannibal". Biology Letters. 9 (3): 20130003. doi:10.1098/rsbl.2013.0003. PMC 3645029. PMID 23637391.
  17. ^ a b c Bansemer, C. S.; Bennett, M. B. (2009). "Reproductive periodicity, localised movements and behavioural segregation of pregnant Carcharias taurus at Wolf Rock, southeast Queensland, Australia". Marine Ecology Progress Series. 374: 215. doi:10.3354/meps07741.
  18. ^ Gilmore, R.G.; Dodrill, J.W. & Linley, P. (1983). "Reproduction and embryonic development of the sand tiger shark, Odontaspis taurus (Rafinesque)" (PDF). Fishery Bulletin. 81 (2): 201–225.
  19. ^ a b Branstetter, Steven; Musick, John A. (1994). "Age and Growth Estimates for the Sand Tiger in the Northwestern Atlantic Ocean". Transactions of the American Fisheries Society. 123 (2): 242. doi:10.1577/1548-8659(1994)123<0242:AAGEFT>2.3.CO;2.
  20. ^ Shark Attack Survivors. sharkattacksurvivors.com
  21. ^ Dudley, S. F. J. (1997). "A comparison of the shark control programs of New South Wales and Queensland (Australia) and KwaZulu-Natal (South Africa)". Ocean & Coastal Management. 34: 1–9. doi:10.1016/S0964-5691(96)00061-0.
  22. ^ Dudley, S. F. J.; Simpfendorfer, C. A. (2006). "Population status of 14 shark species caught in the protective gillnets off KwaZulu–Natal beaches, South Africa, 1978–2003". Marine and Freshwater Research. 57 (2): 225. doi:10.1071/MF05156.
  23. ^ Brazier, W.; Nel, R.; Cliff, G.; Dudley, S. (2012). "Impact of protective shark nets on sea turtles in KwaZulu-Natal, South Africa, 1981–2008". African Journal of Marine Science. 34 (2): 249. doi:10.2989/1814232X.2012.709967.
  24. ^ Barker, S. M.; Peddemors, V. M.; Williamson, J. E. (2011). "A video and photographic study of aggregation, swimming and respiratory behaviour changes in the Grey Nurse Shark (Carcharias taurus) in response to the presence of SCUBA divers". Marine and Freshwater Behaviour and Physiology. 44 (2): 75. doi:10.1080/10236244.2011.569991.
  25. ^ Viegas, Jennifer. "Sand Tiger Sharks Are Curious About People". Retrieved 17 June 2015.
  26. ^ Smith, K.; Scarr, M.; Scarpaci, C. (2010). "Grey Nurse Shark (Carcharias taurus) Diving Tourism: Tourist Compliance and Shark Behaviour at Fish Rock, Australia". Environmental Management. 46 (5): 699–710. doi:10.1007/s00267-010-9561-8. PMID 20872140.
  27. ^ Decker, Robert. "Ghosts in the Graveyard: N.C. Shark Diving". ScubaDiving.com. Retrieved 17 June 2015.
  28. ^ "Sand Tiger Shark". National Geographic.
  29. ^ "The Campus : A Mystery in Captivity". alleghenycampus.com.
  30. ^ Tate, Erin E. (2013). "Correlations of Swimming Patterns with Spinal Deformities in the Sand Tiger Shark, Carcharias taurus" (PDF). International Journal of Comparative Psychology. 26: 75–82. Archived from the original (PDF) on 2013-09-27.
  31. ^ https://www.mq.edu.au/newsroom/2019/02/05/critically-endangered-grey-nurse-shark-mapped-for-the-first-time-in-landmark-study
  32. ^ "Considering Shark Biology in Management". pewtrusts.org. Retrieved 5 July 2015.

Bibliography

  • Parker, Steve; Parker, Jane (2002). "Design for Living". The Encyclopedia of Sharks. Firefly Books. p. 100.

External links

Bigeye sand tiger

The bigeye sand tiger (Odontaspis noronhai) is an extremely rare species of mackerel shark in the family Odontaspididae, with a possible worldwide distribution. A large, bulky species reaching at least 3.6 m (12 ft) in length, the bigeye sand tiger has a long bulbous snout, large orange eyes without nictitating membranes, and a capacious mouth with the narrow teeth prominently exposed. It can be distinguished from the similar smalltooth sand tiger (O. ferox) by its teeth, which have only one lateral cusplet on each side, and by its uniformly dark brown color.

Inhabiting continental margins and oceanic waters at depths of 60–1,000 m (200–3,280 ft), the bigeye sand tiger may make vertical and horizontal migratory movements. It feeds on bony fishes and squid, and its sizable eyes and dark coloration suggest that it may spend most of its time in the mesopelagic zone. Reproduction is probably viviparous with oophagous embryos like in other mackerel shark species. This shark is caught incidentally by commercial fisheries, though so infrequently that the International Union for Conservation of Nature (IUCN) cannot yet determine its conservation status.

Carcharias

Carcharias is a genus of sand tiger sharks belonging to the family Odontaspididae.

Crocodile shark

The crocodile shark (Pseudocarcharias kamoharai) is a species of mackerel shark and the only extant member of the family Pseudocarchariidae. A specialized inhabitant of the mesopelagic zone, the crocodile shark can be found worldwide in tropical waters from the surface to a depth of 590 m (1,940 ft). It performs a diel vertical migration, staying below a depth of 200 m (660 ft) during the day and ascending into shallower water at night to feed. Typically measuring only 1 m (3.3 ft) in length, the crocodile shark is the smallest living mackerel shark. It can be distinguished by its elongated cigar-shaped body, extremely large eyes, and relatively small fins.

An active-swimming predator of pelagic bony fishes, squid and shrimp, the crocodile shark has a sizable oily liver that allows it to maintain its position in the water column with minimal effort. The size and structure of its eyes suggests that it is adapted for hunting at night. The crocodile shark is aplacental viviparous, with females typically giving birth to litters of four. The fetuses are oophagous, meaning that they feed on undeveloped eggs ovulated for this purpose by their mother. Due to its small size, the crocodile shark poses little danger to humans and is of little commercial importance. However, substantial numbers are caught as bycatch, leading it to be assessed as Near Threatened by the International Union for Conservation of Nature (IUCN). This species was responsible for damaging deep sea fiberoptic cables when the technology was first deployed in 1985.

Isurus

Isurus is a genus of mackerel sharks in the family Lamnidae, commonly known as the mako sharks.

Kattegatcentret

Kattegatcentret (The Kattegat Center) is a public aquarium in Grenå, Denmark. Its name refers to the Kattegat sea.

The mission of Kattegatcentret is to mediate knowledge about the sea to the general public, so more people are able to enjoy, understand and guard the seas. Since its opening in 1993, the aquarium has been visited by around 6 million people, with 12,000 schoolchildren and students participating in the centers schoolservice every year. The center was expanded in 2005 and now comprise 5,800 m2 (62,000 sq ft), with all constructions designed by Kjaer & Richter.The aquarium is home to more than 250 species from around the world, from the native herring, wolffish and seals (grey and harbour) to tropical lionfish and coral fish and sharks. The animals are on display in large tanks in a variety of engaging ways. The largest tank, Oceanariet, has a volume of 1,500,000 l (400,000 US gal) and shows a native marine scene from the Kattegat itself. It is possible to dive here for visitors. Another large tank is the 550,000-litre (150,000 US gal) tropical shark tank, Hajtanken, which is equipped with a shark tunnel and is home to species such as sand tiger shark, whitetip reef shark, nurse shark and stingrays. The smallest aquaria at the Kattegatcenter contain 250 l (66 US gal).The Kattegatcenter cooperates on a broad scale with politicians, businesspeople, scientists, institutions and organizations from all over the world. The center is a member of both EAZA and DAZA, two important zoo and aquarium organizations, and are currently working towards being self-sustaining with animals. They have a large breeding program with both native and tropical species.

In cooperation with Danish Technological Institute (DTI) and Aarhus University, The Kattegatcenter created AlgeCenter Danmark in 2011. It is a Danish center for research, innovation and mediation of information about algae. AlgeCenter Danmark has a growing facility for kelp right next to The Kattegatcenter. Every year, the international Nordic Seaweed Conference are held here.

Lamna

Lamna is a genus of mackerel sharks in the family Lamnidae, containing two extant species: the porbeagle (L. nasus) of the North Atlantic and Southern Hemisphere, and the salmon shark (L. ditropis) of the North Pacific.

Lamniformes

The Lamniformes (from the Greek word, Lamna "fish of prey") are an order of sharks commonly known as mackerel sharks (which may also refer specifically to the family Lamnidae). It includes some of the most familiar species of sharks, such as the great white and extinct megalodon, as well as more unusual representatives, such as the goblin shark and megamouth shark.

Members of the order are distinguished by possessing two dorsal fins, an anal fin, five gill slits, eyes without nictitating membranes, and a mouth extending behind the eyes. Also, unlike other sharks, they maintain a higher body temperature than the surrounding water.

Longfin mako shark

The longfin mako shark (Isurus paucus) is a species of mackerel shark in the family Lamnidae, with a probable worldwide distribution in temperate and tropical waters. An uncommon species, it is typically lumped together under the name "mako" with its better-known relative, the shortfin mako shark (I. oxyrinchus). The longfin mako is a pelagic species found in moderately deep water, having been reported to a depth of 220 m (720 ft). Growing to a maximum length of 4.3 m (14 ft), the slimmer build and long, broad pectoral fins of this shark suggest that it is a slower and less active swimmer than the shortfin mako.

Longfin mako sharks are predators that feed on small schooling bony fishes and cephalopods. Whether this shark is capable of elevating its body temperature above that of the surrounding water like the other members of its family is uncertain, though it possesses the requisite physiological adaptations. Reproduction in this species is aplacental viviparous, meaning the embryos hatch from eggs inside the uterus. In the later stages of development, the unborn young are fed nonviable eggs by the mother (oophagy). The litter size is typically two, but may be as many as eight. The longfin mako is of limited commercial value, as its meat and fins are of lower quality than those of other pelagic sharks; it is caught unintentionally in low numbers across its range. The International Union for Conservation of Nature has assessed this species as vulnerable due to its rarity, low reproductive rate, and continuing bycatch mortality.

Megalodon

Megalodon (Carcharocles megalodon), meaning "big tooth", is an extinct species of shark that lived approximately 23 to 2.6 million years ago (mya), during the Early Miocene to the end of the Pliocene. It was formerly thought to be a member of the Lamnidae family, making it closely related to the great white shark (Carcharodon carcharias). However presently there is near unanimous consensus that it belongs to the extinct family Otodontidae, which diverged from the ancestry of the great white shark during the Early Cretaceous. Its genus placement is still debated, authors placing it in either Carcharocles, Megaselachus, Otodus, or Procarcharodon.

Scientists suggest that megalodon looked like a stockier version of the great white shark, though it may have looked similar to the basking shark (Cetorhinus maximus) or the sand tiger shark (Carcharias taurus). Regarded as one of the largest and most powerful predators to have ever lived, fossil remains of megalodon suggest that this giant shark reached a maximum length of 18 meters (59 ft) with the average size being 10.5 meters (34 ft). Their large jaws could exert a bite force of up to 110,000 to 180,000 newtons (25,000 to 40,000 lbf). Their teeth were thick and robust, built for grabbing prey and breaking bone.

Megalodon probably had a major impact on the structure of marine communities. The fossil record indicates that it had a cosmopolitan distribution. It probably targeted large prey, such as whales, seals, and sea turtles. Juveniles inhabited warm coastal waters and fed on fish and small whales. Unlike the great white, which attacks prey from the soft underside, megalodon probably used its strong jaws to break through the chest cavity and puncture the heart and lungs of its prey.

The animal faced competition from whale-eating cetaceans, such as Livyatan and other macroraptorial sperm whales, and smaller ancestral killer whales such as Orcinus citoniensis. As the shark preferred warmer waters, it is thought that oceanic cooling associated with the onset of the ice ages, coupled with the lowering of sea levels and resulting loss of suitable nursery areas, may have also contributed to its decline. A reduction in the diversity of baleen whales and a shift in their distribution toward polar regions may have reduced megalodon's primary food source. The extinction of the shark appeared to affect other animals; for example, the size of baleen whales increased significantly after the shark had disappeared.

National Marine Aquarium, Plymouth

The National Marine Aquarium is a marine aquarium built on reclaimed land in the city of Plymouth, England, in Sutton Harbour, next to the Barbican and fishmarket. It was opened in May 1998, with charitable aims of research, education and conservation. It is the largest aquarium in the United Kingdom.

It is a member of the British and Irish Association of Zoos and Aquariums (BIAZA).

Pacific smalltail shark

The Pacific smalltail shark (Carcharhinus cerdale) is a species of requiem shark, in the family Carcharhinidae. It was described in 1898, but later mistakenly merged with Carcharhinus porosus. The mistake was corrected in 2011.It is relatively small with skin of a light-brownish color, and it can also be found in the Pacific Ocean. Not much is known about this species of shark, and there have been no recorded attacks on humans from this animal. It resembles the copper shark and a sand tiger shark, yet it is much smaller than both. It is probably not dangerous toward humans. It also has a small, slender body, and five gills in front of its pectoral fins.

Pelagic thresher

The pelagic thresher (Alopias pelagicus) is a species of thresher shark, family Alopiidae; this group of sharks is characterized by the greatly elongated upper lobes of their caudal fins. The pelagic thresher occurs in the tropical and subtropical waters of the Indian and Pacific Oceans, usually far from shore, but occasionally entering coastal habitats. It is often confused with the common thresher (A. vulpinus), even in professional publications, but can be distinguished by the dark, rather than white, color over the bases of its pectoral fins. The smallest of the three thresher species, the pelagic thresher typically measures 3 m (10 ft) long.

The diet of the pelagic thresher consists mainly of small midwater fishes, which are stunned with whip-like strikes of its tail. Along with all other mackerel sharks, the pelagic thresher exhibits ovoviviparity and usually gives birth to litters of two. The developing embryos are oophagous, feeding on unfertilized eggs produced by the mother. The young are born unusually large, up to 43% the length of the mother. Pelagic threshers are valued by commercial fisheries for their meat, skin, liver oil, and fins, and are also pursued by sport fishers. The International Union for Conservation of Nature assessed this species as vulnerable in 2007.

Physogaleus

Physogaleus is a small genus of prehistoric shark that lived from the Eocene to Miocene epochs.

Pseudomegachasma

Pseudomegachasma ("false megamouth") is an extinct genus of filter-feeding shark that was closely related to the modern sand tiger shark. It is known from Cretaceous strata in Russia and the United States, and is the only known planktivorous odontaspid, as well as the oldest known planktivorous elasmobranch. It most likely derived from its closest relative, the piscivorous shark Johnlongia. As its name suggests, it was originally classified under Megachasma, before it was found to be an odontaspid.

Ptychodus mortoni

Ptychodus mortoni was a shark believed to be about 10 m long that probably crushed and ate large shelled animals such as giant clams.

The bivalves that lived during this time included gigantic animals, possibly having extremely thick shells, such as the inoceramids (Volviceramus, Platyceramus, etc...).

Given its large size, though, this species of Ptychodus might also have eaten ammonites and primitive turtles, like Desmatochelys.

It is believed to have been a sluggish bottom-dwelling shark, rather than an actively fast swimmer. It lived about 89 million years ago (Turonian stage). Therefore, while only large numbers of its teeth, and jaw fragments are known, it might have resembled a massive nurse shark or a sand tiger shark.

Fossils have been found in the Western Interior Seaway, Kansas, USA.

Sand shark

Sand sharks, also known as sand tiger sharks, grey nurse sharks or ragged tooth sharks, are mackerel sharks of the family Odontaspididae. They are found worldwide in temperate and tropical waters. The three species are in two genera.

Sandbar shark

The sandbar shark (Carcharhinus plumbeus) is a species of requiem shark, and part of the family Carcharhinidae, native to the Atlantic Ocean and the Indo-Pacific. It is distinguishable by its very high first dorsal fin and interdorsal ridge. It is not to be confused with its similarly named shark, the sand tiger shark, Carcharias taurus.

Smalltooth sand tiger

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, invertebrates, and cartilaginous fishes. This species is thought to be ovoviviparous with oophagous embryos 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.

Tiger shark (disambiguation)

The tiger shark, Galeocerdo cuvier, is a large shark in the family Carcharhinidae.

Tiger shark may also refer to:

Tiger Shark (DC Comics), a fictional character from the DC Comics universe

Tiger Shark (film), a 1932 film directed by Howard Hawks

TigerShark, a 1997 PlayStation game

Tiger Shark (Marvel Comics), a fictional character from the Marvel Comics universe

Tigershark (film), a 1987 film directed by Emmett Alston

TigerSharks, a 1980s cartoon series produced by Rankin/Bass

Kozo Urita, a Japanese professional wrestler who goes under the name of Tiger Shark

F-20 Tigershark, a fighter plane built by Northrop in the USA

Grey nurse shark, Carcharias taurus, also known as the sand tiger shark

Tallahassee Tiger Sharks, an ice hockey team which formerly played in the ECHL

Tigershark, a family of 4-cylinder engines introduced by Chrysler in 2012

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