Common name(s)
Sandtiger Shark, Sand Tiger Shark, Raggedtooth Shark, Grey Nurse Shark.
Identification
Head dorsally flattened. Snout conical with a bluntly rounded tip. Lower jaw contains rows of thin curved teeth that are always visibible; snaggle-toothed. First dorsal fin origin roughly one fin length behind free rear tips of pectoral fins. Second dorsal fin almost as large as first dorsal. Second dorsal posterior to pelvic fin free rear tip. Heterocercal caudal fin has a small lower lobe. Upper caudal lobe has a deep subterminal notch.
Dorsal coloration greenish-grey, brown, or tan. Ventral surface off-white. Juveniles often have scattered dark spots or small blotches.
Size
Maximum size approximately 300cm. Size at birth 85-105cm.
Habitat
Coastal and offshore temperate/sub-tropical rocky reefs. Usually close to the substrate but sometimes found schooling in midwater. Surface to at least 191m.
Distribution
Widely distributed in coastal environments but absent from the eastern Pacific. In the western Pacific, the sandtiger is found from Japan, China and Australia. In the western Atlantic it is found from Maine to Florida including the Gulf of Mexico, And in Southern Brazil and Argentina. In the eastern Atlantic it occurs in the Mediterranean and along most of the African coastline. It is also found in the red sea and probably off of India.
Conservation Status
VULNERABLE
Grey Nurse Sharks have been fished throughout their range in the past, but are of variable economic importance regionally (Compagno 1984a). The species is highly regarded as a food fish in Japan, but not in the western Atlantic. It is caught primarily with line fishing gear, but is also taken in bottom-set gillnets and trawls. The meat is utilised fresh, frozen, smoked, and dried and salted, for human consumption. This species has also been used for fishmeal, its liver for oil, and its fins for making soup via the oriental sharkfin trade (Compagno 1984a).
This species has been taken along the Atlantic coast of the United States in a commercial shark fishery directed towards a wide array of large coastal species, but supported primarily by catches of Carcharhinus plumbeus and C. limbatus. Musick et al. (1993) showed that several species of sharks, including the sand tiger, had declined by as much as 75% during the decade from 1980-1990 because of overfishing. Recently, this fishery has come under management and C. taurus has been accorded full protection (see below).
In the 1850s, this species was fished by hook-and-line in and around Botany Bay, New South Wales (NSW), Australia, during October and November, to provide a source of oil “of excellent quality for burning in lamps” (Grant 1982). In the late 1920s this species was also fished, together with other shark species, at Port Stephens, NSW (Roughley 1955). It was the second most commonly captured shark after the whaler sharks (Carcharhinidae) in this area. According to Roughley (1955), Grey Nurse Sharks produced the best quality shark leather but their fins were not as desirable as those from some of the other sharks commonly caught in this fishery. Commercial fishing for C. taurus reputedly continued on and off in NSW using various methods up until the Second World War.
Pepperell (1992) summarised catch records of gamefishermen in south-eastern Australia and found that C. taurus constituted 11% (161 sharks) of the total recorded shark catch (1,461) during the 1960s and 7% (244 sharks) in the 1970s (total catch 3,466 sharks). The weights of C. taurus specimens caught by game fishermen ranged from less than 10 to around 190 kg (Pepperell 1992). Capture of this species was banned voluntarily by game fishermen throughout Australia in 1979 (Pepperell 1992).
Meshing of beaches was instituted in NSW in the late 1930s to protect bathers from shark attack (Reid and Krough 1992). Since then, shark meshing has also been adopted in Queensland, Australia (Paterson 1986) and in Natal, South Africa (Cliff and Dudley 1992). Carcharias taurus comprised 3.8% (n = 369) of the total NSW (i.e. Newcastle-Sydney-Wollongong area) beach meshing catch of sharks from 1950-1990 (Reid and Krough 1992). The number of C. taurus taken in these mesh nets in NSW over this 40-year period is thus slightly less than that taken by game fishermen during the 1960s and 1970s. Overall, there have been large declines over time in the meshing catch and catch per unit effort for the species. During the early 1950s, 24-36 C. taurus were meshed per year, but since the late 1970s only 0-3 were caught each year (Pollard et al. 1996). Prior to this 40-year period, Coppleson (1958) reported 58 Grey Nurse Sharks being caught in these beach meshing nets between October and December 1937.
Cliff and Dudley (1992) reported an average annual catch of 246 spotted ragged tooth sharks in the Natal (South Africa) beach meshing programme for the period 1978-1990, with 38% of the catch being found alive in the nets. Whenever possible these live sharks were released, many with tags. Between 1966-1972 there was a significant decline in the catch rate of this species, followed by a significant increase between 1972-1990 (Dudley and Cliff 1993a). Maximum and minimum catches were 20 (1966) and two (1981) sharks per km of net per year (Dudley and Cliff 1993a).
Interactions between skindivers and C. taurus in Australia are nowadays rare. There are reports of Grey Nurse Sharks stealing speared fish from skindivers, but this is not common. During the 1950s and 1960s, however, skin and SCUBA divers armed with barbless or barbed spears, hypodermic spears containing strychnine nitrate, and especially explosive powerheads, killed many C. taurus off the NSW coast (Cropp 1964). Divers also took them alive, often with lassos, to sell to aquariums (Cropp 1964). Carcharias taurus are still taken, under permit, for aquariums (Smith 1992), but with the assigning of their protected status (see later) and an increased awareness of the need for their conservation, there are now no reports of divers killing these sharks deliberately.
Citation
Pollard, D. & Smith, A. 2009. Carcharias taurus. The IUCN Red List of Threatened Species 2009: e.T3854A10132481. https://dx.doi.org/10.2305/IUCN.UK.2009-2.RLTS.T3854A10132481.en. Downloaded on 16 December 2020.
Reproduction
Aplacental viviperous. Like other lamnids, sandtigers are oophagous; consuming large quantities of unfertilized eggs once their small yolk sac has been depleted. However, by the time they reach around 50mm, they have developed precocious dentition. Once they are 80-100mm long, they start seeking out smaller developing embryos to feed upon until they are the sole embryo within that uterus. This unusual feeding strategy is known as ’embryonic cannibalism’.
Diet
Sandtigers will readily feed on any available fish species within their habitat that are small enough to consume. There is a record of a sandtiger biting off the flipper of a loggerhead turtle.
Behavior
Sandtiger sharks have the unique ability (among sharks) to hover in the water column without sinking. To achieve this, they periodically swim to the surface and ‘gulp’ air; essentially turning their stomach cavity into a swim bladder.
They are also capable of creating a ‘whip crack’ sound with their tail when they move quickly from a stationary position. This may be incidental but it could be a way to shock or confuse prey fishes, or perhaps even a threat display.
Reaction to divers
Easily approached with slow non-threatening movements. Chumming is not necessary to encounter this species where it naturally occurs.
Diving logistics
There are numerous spots around the world where sandtigers can be reliably encountered.
In North Carolina, operators run day trips out of various ports to dive on wrecks that are scattered around the Outer Banks and infamous Diamond Shoals. Many of the wrecks have resident populations of sandtiger sharks. The sharks sometimes move from one wreck to another but one that seems to be consistently good is the Carib Sea. Another good wreck for sandtigers is the Proteus.
In South Africa, Sandtigers (locally known as raggies or raggedtooth sharks) are easily encountered at Protea Banks. The Cathedral is one dive site that is particularly good for sharks.
In Australia, sandtigers (locally known as grey nurse sharks) are common off of numerous spots along the coast of New South Whales. One of the best places to see them is at Fish Rock; an exceptional dive site that generally has lots of sand tigers in the valleys around the central island, and a cave with a large entrance where they often congregate. The site is also home to a variety of wobbegong species, and large sharkfin guitarfishes.
Similar species
Smalltooth Sandtiger Distinguished by heavier body, less pronounced snaggletooth look, and second dorsal which is noticeably smaller than the first.
Lemon Shark Similar in coloration and in having two dorsal fins of equal size. Distinguished by broadly rounded snout, and more anterior pectoral fins that originate below the third gill slit.
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