|Scientific Name:||Galeocerdo cuvier|
|Species Authority:||(Peron & Lesueur, 1822)|
Squalus cuvier Péron & Lesueur, 1822
|Red List Category & Criteria:||Near Threatened ver 3.1|
|Reviewer/s:||Musick, J.A. & Fowler, S.L. (Shark Red List Authority)|
This assessment is based on the information published in the 2005 shark status survey (Fowler et al. 2005).
This large (>550 cm), omnivorous shark is common world wide in tropical and warm-temperate coastal waters. It is a relatively fast growing and fecund species. The Tiger Shark (Galeocerdo cuvier) is caught regularly in target and non-target fisheries. There is evidence of declines for several populations where they have been heavily fished, but in general they do not face a high risk of extinction. However, continued demand, especially for fins, may result in further declines in the future.
|Range Description:||The Tiger Shark has a worldwide distribution in tropical and warm temperate seas. Randall (1992) described its distribution as follows: 'In the western Atlantic it ranges from Cape Cod to Uruguay, including the Gulf of Mexico, Bermuda and islands of the Caribbean; in the eastern Atlantic it is found on the West African coast from Morocco to Angola; it remains unknown from the Mediterranean Sea, but there are reports from Iceland and the United Kingdom (these were probably based on vagrants transported there during a warm year by the Gulf Stream) (Compagno 1984). It occurs throughout the Indo-Pacific region from the northern Red Sea to South Africa and east through the islands of Oceania and northern New Zealand (though not yet reported from Easter Island); in the eastern Pacific it ranges from southern California to Peru, including the Galapagos and Revillagigedo Islands.'
Little is known of the Tiger Shark's depth range. Clark and Kristof (1990) illustrate a female Tiger Shark of about 250 cm total length (TL) from a photograph taken from a submersible in 350 m of water off Grand Cayman. The species is also encountered in very shallow water.
Native:American Samoa (American Samoa); Angola (Angola); Anguilla; Antigua and Barbuda; Aruba; Australia; Barbados; Belize; Benin; Bermuda; Brazil; Cameroon; Cayman Islands; Colombia; Congo; Cook Islands; Costa Rica; Côte d'Ivoire; Cuba; Djibouti; Dominica; Dominican Republic; Ecuador; Egypt; Equatorial Guinea; Eritrea; Fiji; French Guiana; French Polynesia; Gabon; Gambia; Ghana; Grenada; Guadeloupe; Guam; Guatemala; Guinea; Guinea-Bissau; Guyana; Haiti; Honduras; Iceland; Indonesia; Jamaica; Kenya; Kiribati; Liberia; Marshall Islands; Martinique; Mauritania; Mexico; Micronesia, Federated States of; Montserrat; Morocco; Mozambique; Nauru; New Caledonia; New Zealand; Nicaragua; Nigeria; Niue; Norfolk Island; Northern Mariana Islands; Palau; Panama; Papua New Guinea; Peru; Pitcairn; Puerto Rico; Saint Kitts and Nevis; Saint Lucia; Saint Vincent and the Grenadines; Samoa; Saudi Arabia; Senegal; Sierra Leone; Solomon Islands; Somalia; South Africa; Sudan; Suriname; Tanzania, United Republic of; Timor-Leste; Togo; Tokelau; Tonga; Trinidad and Tobago; Tuvalu; United Kingdom; United States (Alabama, California, Connecticut, Delaware, Florida, Georgia, Hawaiian Is., Louisiana, Maryland, Massachusetts, Mississippi, New Jersey, New York, North Carolina, Rhode Island, South Carolina, Texas, Virginia); United States Minor Outlying Islands; Uruguay; Vanuatu; Venezuela; Virgin Islands, British; Virgin Islands, U.S.; Wallis and Futuna; Western Sahara; Yemen
|FAO Marine Fishing Areas:||
Atlantic – eastern central; Atlantic – northeast; Atlantic – northwest; Atlantic – southeast; Atlantic – southwest; Atlantic – western central; Indian Ocean – eastern; Indian Ocean – western; Pacific – eastern central; Pacific – northwest
|Range Map:||Click here to open the map viewer and explore range.|
|Habitat and Ecology:||
Randall (1992) reviewed a large number of studies on the feeding behaviour of Tiger Sharks, including Norman and Fraser (1937), Springer (1938), Whitley (1940), Bigelow and Schroeder (1948), Gudger (1948a,b, 1949), Kauffman (1950), Ikehara (1960), Springer in Gilbert (1963), Gohar and Mazhar (1964), Clark and von Schmidt (1965), Randall (1967, 1980), Tester (1969), Fujimoto and Sakuda (1972), Bass et al. (1975), De Crosta et al. (1984) and Stevens (1984). He concluded that this species has probably the most diverse diet of any shark species. Prey includes numerous bony fish, sharks, rays, turtles, sea birds, seals, dolphins, sea snakes, cephalopods, crabs, lobsters, gastropods and jellyfish. They consume carrion and readily take baited hooks. Tiger Sharks also have a propensity to consume ?garbage? of human origin, including plastics, metal, sacks, kitchen scraps and almost any other item discarded in the sea.
The age and growth characteristics of Tiger Sharks have been investigated by a number of authors, most notably De Crosta et al. (1984) and Branstetter et al. (1987). Working in the north-west Hawaiian Islands De Crosta et al. (1984) estimated that a Tiger Shark with a precaudal length of 200 cm is about five years old and that one of 300 cm is about 15 years old. Branstetter et al. (1987) used similar techniques to De Crosta et al. (1984) to produce growth curves for Tiger Sharks from the coast of Virginia and the northern Gulf of Mexico. They estimated that initial growth was very fast, but that the rate of growth of very large animals is 5?10 cm year-1; thus, individuals of 400?450 cm TL would be 20?25 years of age. Branstetter et al. (1987) gave a maximum age of 45?50 years. Smith et al. (1998) estimated the intrinsic rate of increase of a tiger shark population at MSY to be 0.043 year-1. Randall (1992) summarised that the size at maturity of male Tiger Sharks is 226?290 cm TL and in females 250?350 cm TL.
The Tiger Shark is the only species of the family Carcharhinidae that is ovoviviparous. Litter sizes are large, with between 10?82 embryos reported from a single female. Mean litter sizes of 30?35 have been reported (Tester 1969, Bass et al. 1975, Simpfendorfer 1992). The size at birth is 51?90 cm TL (Randall 1992, Simpfendorfer 1992). Clark and von Schmidt (1965) gave the gestation period as 13?16 months. There have been few other estimates of gestation period. Mating is reported to take place in the Northern Hemisphere in spring, with pupping the following spring to summer. Mating occurs before full-term females have given birth to young, indicating that litters are produced every two years or less. In the Southern Hemisphere Stevens and McLoughlin (1991) and Simpfendorfer (1992) have reported pupping during summer. The young are very slender with a flexible body and caudal fin; they swim with an inefficient anguilliform motion. Branstetter et al. (1987) concluded that they are probably very vulnerable to predation at this stage, especially by sharks, including their own kind.
Tagging studies, particularly in the western Atlantic, have provided the best information on the movements of Tiger Sharks. Randall (1992) provided data from a range of studies that indicated that two patterns of movement are observed in tagging studies. The first of these is where the release and recapture positions are close together, suggesting that the individual may have remained in a relatively small area. The other pattern observed is where the individual is recaptured a long distance from the release site, often after a short period at liberty. The maximum reported distance between release and recapture for a Tiger Shark was approximately 3,430 km.
Tiger sharks are caught in numerous fisheries world wide, both as target species and bycatch. Products utilised from Tiger Sharks include flesh, fins, skin, liver oil and cartilage. Although not considered of high quality, the mercury content of this shark's flesh is lower than other large carcharhinid species (Simpfendorfer pers. data). The fins, skin and liver oil from Tiger Sharks are all considered to be of high quality and can fetch good prices. The high value of products has increased commercial fishing pressure on this and similar species worldwide, especially since demand for high quality shark fins has increased. Catches of Tiger Sharks in directed shark fisheries have been documented for a number of areas including the western Atlantic (e.g., Kleijn 1974, Hoey and Casey 1986, Berkeley and Campos 1988, Bonfil 1994, GSAFDF 1996), Australia (Stevens et al. 1982, Lyle et al. 1984), India (Burman 1994), Papua New Guinea (Chapau and Opnai 1986), Brazil and Taiwan (Province of China) (Bonfil 1994). Commercial catches are also taken in many other areas but few records of their capture exist. Tiger Sharks are not typically the target species in these fisheries but are bycatch in fisheries targeting other shark species. Catches of Tiger Sharks in these fisheries are often not reported directly, but observer data on the species composition can be used to make estimates.
In the US East Coast/Gulf of Mexico shark fishery tiger sharks are the third most common large, coastal species caught in the fishery, accounting for 12?20% of the catch (GSAFDF 1996). However, they account for only 5% of the landed weight as they are considered of limited value since finning is not allowed in this fishery. Most of the individuals caught in this fishery are juveniles less than 150 cm FL, although large animals are also taken (S. Branstetter pers. comm.).
In northern Australia gillnet fisheries catch Tiger Sharks, although the mesh sizes used have precluded the capture of significant numbers (Lyle et al. 1984). In northern West Australia a number of fishers have used heavy drumlines to fish for large sharks. Tiger Sharks have been a major target of these fishers, with catches reaching 116 t (live weight) in 1994/95 (Simpfendorfer and Lenanton 1995). All operators who have targeted Tiger Sharks in this area have now ceased fishing.
Tiger Sharks are taken as bycatch in a variety of fisheries including tuna and swordfish longline fisheries (e.g., Anderson 1985, Berkeley and Campos 1988), particularly those operating on, or close to, the continental and insular shelves. They are also taken in trawl fisheries (e.g., squid, fish and crustacean trawl fisheries), although normally in small numbers. There are few records of Tiger Shark catches for these fisheries. Tiger Sharks are undoubtedly caught in tropical and subtropical artisanal fisheries. However, gear limitations in these fisheries probably precludes the capture of large numbers, especially of larger individuals. There are few published data on artisanal fishery captures and it is not possible to quantify catches or the impact that these may have on Tiger Shark populations.
Tiger Sharks are caught by recreational fishers. The species is one that has International Game Fish Association (IGFA) status, the current record being 596 kg. Catches have been documented off the east coast of the United States, Australia and South Africa (e.g., Stevens 1984, Anderson 1985, Casey and Hoey 1985, Pepperell 1992, Anon. 1994). Estimates of total catches of shark by recreational anglers off the east coast of the United States (including the Gulf of Mexico) in 1978 are 10,300 t (Casey and Hoey 1985) and in 1980 over 15,000 t (Anderson 1985). Estimates of the species composition of the recreational catch indicates that Tiger Sharks represent 0.8?2.1% of the catch. Based on these estimates of species composition, the recreational Tiger Shark catches in 1978 and 1980 would have been approximately 10?20 t and 15?30 t, respectively. More recently recreational catches have declined, and tagging and release has become more common. In Australian waters Pepperell (1992) estimated that Tiger Sharks represented approximately 10% of the sharks captured by IGFA associated clubs off the New South Wales coast during the 1970s. This increased to approximately 20% during the 1980s, due to increased targeting. Size composition data provided by Pepperell (1992) indicate that the bulk of the catch was 80?130 kg. Stevens (1984) estimated that Tiger Sharks comprised 17% of the recreational catch by anglers off New South Wales between 1979 and 1982, based on catch sampling.
Tiger Sharks are undoubtedly caught by recreational fishers in many countries, and not only those documented above. Recreational fishing is likely to account for significant mortality in Tiger Shark populations in coastal waters of some countries.
The large size, and propensity to occasionally attack humans, makes Tiger Sharks a target of shark control programmes, particularly those operating in tropical areas (e.g., Queensland (Paterson 1990) and Hawaii (Wetherbee et al. 1994)). However, they are also taken in other programmes (e.g., South Africa (Dudley and Cliff 1993) and New SouthWales (Reid and Krough 1992)). These control programmes use either large mesh gillnets and/or heavy lines to capture large, dangerous sharks. The theory behind the programmes is that fishing reduces the abundance of the large, dangerous sharks and so reduces the probability of attacks in areas where there has previously been relatively high records of shark attacks. There is conflicting evidence as to whether these control programmes are effective in reducing the abundance of Tiger Sharks. Evidence from Paterson (1990), Simpfendorfer (1992) and Dudley and Cliff (1993) indicates that Tiger Shark abundance has either remained steady, or even increased in ?meshed? areas. Catch rate data from Hawaii indicated that shark control programmes did reduce Tiger Shark abundance (Wetherbee et al. 1994). These data suggest that at best the use of shark control programmes to reduce population levels of Tiger Sharks may be of only limited value.
Tiger Shark populations face a variety of threats. These include not only a large range of directed and bycatch fisheries, but also problems such as the ingestion of human garbage. The high value of some products (especially fins) from Tiger Sharks has resulted in increased fishing pressures on this species in recent years. Musick et al. (1993) noted a precipitous decline in Tiger Sharks off Virginia, USA, due to both recreational and commercial harvesting between 1980 and 1992. There is anecdotal evidence that in areas where catches in commercial fisheries are high, abundance has been significantly reduced (e.g., Taiwan (POC) (Bonfil 1994)). There is some evidence from shark control programmes that localised catches of Tiger Sharks do not affect abundance.
The widespread distribution of this species increases the likelihood that it will survive increasing levels of exploitation in certain areas. Its growth and reproductive rates are also relatively high, making the levels of mortality that the Tiger Shark can survive higher than for many other species of shark. Additionally, juvenile survivorship increases where adult Tiger Shark populations have been depleted by fisheries and hence predation of young is lessened. However, the overall life history constraints to increased mortality applicable to all sharks must also be borne in mind when considering the conservation status of this species.
|Conservation Actions:||There are no specific conservation or management measures in place for the Tiger Shark. However, in the US Atlantic and Gulf of Mexico this species is managed under a Fisheries Management Program (FMP) introduced in 1993. It is included in the large coastal group which has an annual quota of 1,285 t. This group is dominated by Sandbar Shark (C. plumbeus) and the Blacktip Shark (C. limbatus). A new FMP was introduced in early 1999, placing Tiger Sharks in the ridgeback large coastal group which have a quota of 622 t and a minimum size of 137 cm fork length. A court placed an injunction on these new regulations pending further court action by commercial fishers.|
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|Citation:||Simpfendorfer, C. 2009. Galeocerdo cuvier. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 22 May 2013.|
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