|Scientific Name:||Carcharias taurus|
|Species Authority:||Rafinesque, 1810|
|Infra-specific Taxa Assessed:|
|Red List Category & Criteria:||Vulnerable A2ab+3d ver 3.1|
|Assessor/s:||Pollard, D. & Smith, A.|
|Reviewer/s:||Musick, J.A. & Fowler, S.L. (Shark Red List Authority)|
This assessment is based on the the information published in the 2005 shark status survey (Fowler et al. 2005).
The Grey Nurse Shark (Carcharias taurus) is a large, coastal shark with a disjunct distribution, occurring in most subtropical and warm temperate oceans, except for the Eastern Pacific. It has a strongly K-selected life history and produces only two large pups per litter. As a result, annual rates of population increase are very low, greatly reducing its ability to sustain fishing pressure. Populations in several locations have been severely depleted by commercial fishing, spearfishing and protective beach meshing, requiring the introduction of specific management measures.
|Range Description:||Historically, the Grey Nurse Shark is regarded as having a broad inshore distribution, primarily in subtropical to warm temperate waters around the main continental landmasses, except in the eastern Pacific off North and South America (Compagno 1984a). In the Western Atlantic, this shark occurs from the Gulf of Maine to Florida (USA), in the northern Gulf of Mexico, around the Bahamas and at Bermuda, and also from southern Brazil to northern Argentina. In the eastern Atlantic it is found from the Mediterranean 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 it ranges from South Africa to southern Mozambique, but does not occur around Madagascar. This species has also been reported from the Red Sea and may occur as far east as India (where it appears to have been referred to as C. tricuspidatus; see Compagno 1984a). In the western Pacific, it has been reported from Japan and Australia, but not New Zealand (Last and Stevens 1994).|
Native:Albania; Algeria; Argentina; Australia (New South Wales, Queensland); Bahamas; Bermuda; Bosnia and Herzegovina; Brazil; Cameroon; Cape Verde; Croatia; Egypt; Eritrea; France; Gambia; Ghana; Greece; Guinea; Guinea-Bissau; India; Italy; Japan; Lebanon; Liberia; Libya; Mexico; Montenegro; Morocco; Mozambique; Nigeria; Saudi Arabia; Senegal; Sierra Leone; South Africa; Spain; Sudan; Syrian Arab Republic; Tunisia; Turkey; United States (Connecticut, Delaware, Florida, Georgia, Maine, Maryland, New Jersey, North Carolina, Rhode Island, South Carolina, Virginia); Uruguay; Yemen
|FAO Marine Fishing Areas:||
Atlantic – eastern central; Atlantic – northwest; Atlantic – southeast; Atlantic – southwest; Atlantic – western central; Indian Ocean – eastern; Indian Ocean – western; Mediterranean and Black Sea; Pacific – northwest; Pacific – southwest; Pacific – western central
|Range Map:||Click here to open the map viewer and explore range.|
|Habitat and Ecology:||
The maximum size of this species has been given variously as ~3.2 m by Compagno (1984a), ~2.75 m and ~142 kg by Hutchins and Swainston (1986) and ~3.2 m and ~300 kg by Hutchins and Thompson (1983). Catch records from beach meshing in NSW, however, suggest that these sharks may grow to 4.3 m, though this maximum length is doubtful and may be due to a misidentification (Reid and Krough 1992).
Branstetter and Musick (1994) described the age and growth of C. taurus in the western North Atlantic based on banding patterns on vertebral centra and stated the maximum age to be 30?35 years. The largest (oldest) male examined (248 cm TL) from the south-eastern USA was 7.5 years old, and the largest (oldest) female examined (272 cm TL) was 10.5 years old. The hypothesis of double annual ring formation is currently being re-examined. If only one ring is deposited each year, the ages cited above would be approximately doubled (J. Musick pers. comm.). The oldest individuals recorded in aquaria were 13 years in Australia (Roughley 1955) and 16 years in South Africa (Govender et al. 1991).
The Grey Nurse Shark occurs either alone or in small to medium-sized aggregations of 20?80 individuals (Silvester 1977, Aitken 1991, Cliff unpubl.). These sharks are often observed hovering motionless just above the seabed in or near deep sandy-bottomed gutters or rocky caves, usually in the vicinity of inshore rocky reefs and islands. They are generally coastal, usually being found from the surf zone down to depths of around 25 m. However, they may also occasionally be found in shallow bays, around coral reefs and, very rarely, to depths of around 200 m on the continental shelf. They usually live near the bottom, but may also move throughout the water column (Compagno 1984a).
Males and females both mature at approximately 2 m in length off the south-eastern USA (Gilmore et al. 1983). They are ovoviviparous and usually only two pups are born per litter once every two years. This is because the remaining eggs and developing embryos are eaten by the largest and/or most advanced embryo in each horn of the uterus (a phenomenon known as adelphophagy or uterine cannibalism). The gestation period may last from 9?12 months and size at birth is relatively large, at about 1 m (Gilmore et al. 1983, Gilmore 1993).
Grey Nurse Shark populations off South Africa and the east coast of the USA are known to undertake complex size and sex segregated migrations. These have been documented by Bass et al. (1975c), Gilmore (1993) and Musick et al. (1993). In other parts of its range and particularly in south-eastern Australia, this species appears to undertake similar migrations.
The species feeds on a wide range of teleost fishes, as well as smaller sharks (Carcharhinidae and Triakidae), rays (Myliobatidae), squids, crabs and lobsters (Compagno 1984, Gelsleichter et al. 1999). Scott et al. (1974) reported that Grey Nurse Sharks in south-eastern Australia fed on shoals of Australian salmon (Arripidae) and other pelagic fish species.
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.
Because of its large size and fearsome appearance, and because it occurs in relatively shallow water where it often hovers almost motionless near the sea floor, C. taurus can be readily approached and is now a very popular attraction with SCUBA divers. Dive guides tend to highlight locations where these sharks regularly occur (e.g., Byron 1985), and divers can observe C. taurus at the same locations on many occasions, suggesting a high degree of site-attachment by these sharks. On the other hand, concern has been expressed (most recently in South Africa) that disturbance by divers may be detrimental to natural behaviour patterns and could even result in the exclusion of some sharks from critical habitat and/or important refuge areas (Andrew Cobb in litt.).
|Conservation Actions:||Carcharias taurus was protected in NSW in 1984 because of serious declines in the population due to commercial and recreational fishing, spearfishing and beach meshing. In early 1997, the Queensland State Government also declared C. taurus a totally protected species in that State?s waters, and the Australian Commonwealth Government followed suit with protection of C. taurus as a Vulnerable species in all Commonwealth waters and throughout Australia?s Exclusive Economic Zone (EEZ) (i.e., out to two hundred nautical miles offshore). Also in 1997, C. taurus received full protection on the Atlantic and Gulf coasts of the USA, under the Atlantic Fishery Management Plan. The main current threat to this species in south-eastern Australia is probably the accidental (bycatch) capture of juveniles by recreational line fishers.|
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|Citation:||Pollard, D. & Smith, A. 2009. Carcharias taurus. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 22 May 2013.|
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