|The tiger shark is one of the largest ocean predators and relies on camouflage and stealth to capture its prey. This solitary, nocturnal carnivore is nomadic and can be found in the epipelagic and mesopelagic zones of neritic and oceanic habitats. The only viviparous species of its family, it gives birth to live young.|
Tiger sharks are large with a sizeable, blunt nose on the end of a wedge-shaped head. They are one of the largest predators in the ocean. Adults range from 3.25 to 4.25 meters in total length, although tiger sharks of 6 to 7.5 meters (25 feet) in length have been documented. Individuals larger than 5 meters, or 16 feet, in total length are rarely seen.
Tiger sharks display sexual dimorphism in body size as females are smaller than males. Female tiger sharks average 2.92 meters in total length while males average 3.20 meters in total length.
Adult tiger sharks typically weigh 385 to 635 kilograms, with the largest sharks reaching 862 kilograms.
Tiger sharks have serrated teeth, making it easy to tear flesh and crack the bones and shells of their prey. Serrated teeth give this species the ability to penetrate the shells of sea turtles.
Tiger sharks have a heterocercal tail, meaning the dorsal lobe of the caudal fin is longer than the ventral lobe. In tiger sharks, the heterocercal tail, or caudal fin, is the primary source of propulsion. The caudal fin produces a downward thrust of water behind the center of balance in a shark, which should cause its head to turn upwards. However, because the tail also moves side to side, it keeps the head from turning upwards. Because of this, tiger sharks move in an S-shaped fashion.
Tiger sharks live longer in the wild than in captivity, averaging 27 years. The maximum age of a tiger shark is estimated at 27-37 years. Tiger sharks in captivity do not live as long, living a maximum of 17 to 20 years. In captivity, this species tends to die of starvation rather than old age, as food that is already dead is less appealing to tiger sharks.
Based on data from the Western North Atlantic and Australia, the generation length is estimated at 17.5-22.5 years.
The tiger shark’s genus, Galeocerdo, is derived from the Greek galeos, which means shark, and kerdo, the word for fox. The tiger shark is often colloquially called the man-eater shark.
The tiger shark’s common name derives from the unique camouflage patterning of juveniles. Tiger shark pups are born with tiger-like stripes on their back and a lightly colored yellow or white belly. This camouflage patterning and coloration provides protection against predators and allowed the juveniles to to blend in with the environment. These stripes fade as the juveniles reach adulthood, which is around 6 to 8 years.
The tiger shark was first described by Peron and Lesueur in 1822 and was given the scientific name Squalus cuvier. In 1837, Müller and Henle renamed it Galeocerdo tigrinus.
The tiger shark is the largest member of the Carcharhinidae family, commonly referred to as requiem sharks. Carcharhiniformes is the most species-rich order of sharks with more than 270 species including the small catsharks and hammerhead sharks. Members of this order are characterized by the presence of a nictitating membrane over the eyes, two dorsal fins, an anal fin, and five gill slits. This family consists of mostly slender but powerful mid- to large-sized sharks and includes some other well-known sharks, such as the blue shark (Prionace glauca), lemon shark (Negaprion brevirostris), and bull shark (Carcharhinus leucas).
The tiger shark has a circumglobal range in subtropical and tropical, warm, temperate oceans, ranging between latitudes of approximately 40°N to 36°S.
In the western Atlantic, the species ranges from the state of Massachusetts in the United States of America to Uruguay, including the Gulf of Mexico, Latin America, islands of the Caribbean, and isolated islands such as Fernando de Noronha. Tiger sharks have been sighted from the eastern coast of North America to the eastern coast of Brazil. In the eastern Atlantic, it is found along the West Africa coast, from Morocco to Angola, including the Canary Islands and the Azores. It has been reported off Libya in the Mediterranean, though whether it is resident or vagrant is unknown.
This shark is distributed throughout the Indo-Pacific. In the Indian Ocean, the tiger shark is found from the east coast of Africa to South Africa, including remote islands such as Reunion and Chagos Archipelago, north to the Red Sea, and throughout the tropical Indian Ocean. In the western and central Pacific, it occurs from Australia north to eastern China, India, and Japan, and throughout Pacific islands including Palau, east to the Solomon, Marshall, and Hawaiian Islands, south to northern New Zealand, as well as French Polynesia and more isolated atolls. In the eastern Pacific, it ranges from southern California to Peru, including the Galapagos and Revillagigedo Islands.
The tiger shark also appears seasonally in cool temperate waters, most likely following warmer currents. The presence of this shark in temperate regions has been reported from the United Kingdom and Iceland in the Atlantic, Alaska in the Northeast Pacific, the southern coasts of New South Wales and Western Australia in Australia, and in South Africa.
The tiger shark is a saltwater species and inhabits marine neritic and oceanic habitats. It can be found near shelf, reef, and slope habitats and is sometimes associated with coral reefs. Although it prefers the sea grass ecosystems of the coastal areas, it occasionally inhabits other areas due to prey availability.
Tiger sharks have also been documented in river estuaries and harbors.
The tiger shark is found in the epipelagic zone of 0-200 meters and occasionally makes longer-distance excursions into the mesopelagic zone of 200-1,000 meters. Tiger sharks spend approximately 36% of their time in shallow coastline habitats, generally at depths of 2.5 to 145 meters. The species mostly occurs to 100-meter depth but has also been documented several kilometers from the shallow areas and at depths greater than 1,000 meters with 1,136 meters being the maximum recorded.
Female tiger sharks are observed in shallow areas more often than males.
The tiger shark is highly mobile and has been noted to travel hundreds, and in some cases thousands, of kilometers.
Tiger sharks are solitary except during the mating seasons or while communally feeding on large carcasses.
The tiger shark is nomadic and highly mobile. This species has been noted to travel hundreds, and in some cases thousands, of kilometers. Individuals attached with transmitters swam up to 16 kilometers in a single day and did not return to that area for close to a year. As a result, tiger sharks have very large home ranges and territories of about 23 square kilometers.
The tiger shark relies on electromagnetic receptors to perceive its environment and to hunt prey. Sensing organs called Ampullae of Lorenzini, located on the end of their nose, are filled with a jelly-like substance that reads electromagnetic signals. These signals are sent from the pores to the sensory nerve, and then to the brain. While hunting, tiger sharks use this ability to detect electromagnetic signals given off by fish. Tiger sharks also use these organs to sense changes in water pressure and temperature. Members of this species also have a lateral line on both sides of the body that runs from the gill line to the base of the tail. The lateral line reads the vibrations in the water from the movement of other animals nearby. Ampullae of Lorenzini and lateral lines also help detect electromagnetic signals from other sharks. While communally feeding on carcasses, sharks give off signals signifying dominance and thus the order in which they feed.
The diet of tiger sharks includes mollusks, birds, snakes, crustaceans, sea turtles, and dugongs (Dugong dugon). Tiger sharks also often scavenge dead or injured whales.
As top predators in their ecosystem, it is possible that tiger sharks control populations of prey species, although this has not been verified.
Tiger sharks are nocturnal predators and most likely rely on stealth rather than strength and speed to catch prey. Tiger sharks are well camouflaged, allowing them to get within striking range of prey. They are blue or green in color with a light yellow or white under-belly. If prey flee, tiger sharks may back off, not taking part in high-speed pursuits. However, tiger sharks are capable of short bursts of speed once their prey are within range. They are very strong and fast and are not quickly or easily exhausted.
While communally feeding on carcasses, sharks give off signals signifying dominance and thus the order in which they feed. During these group feedings, tiger sharks have a loose social hierarchy where larger sharks feed first. Smaller sharks circle around the carcass until the larger sharks are full, then move in to feed. Violence is minimal during these scavenging feasts.
Large tiger sharks can survive several weeks without feeding.
There is regional variability in tiger shark sizes and ages at sexual maturity. On average, tiger sharks reach sexual maturity at 4-13 years of age. Male tiger sharks reach maturity earlier than females, maturing when they reach an average total length of 25 to 30.5 meters, whereas females reach sexual maturity when they reach 27.4 to 34.5 meters in length.
Female tiger sharks mate once every three years.
Tiger shark breeding seasons differ in the northern and southern hemispheres. In the northern hemisphere, females delay fertilization until March or May in order to give birth between May and June of the following year. In the southern hemisphere, females delay mating until November or January in order to give birth between February and March of the following year.
Male tiger sharks have diametric testes, which are capable of synthesizing a larger amount of sperm than radial or compound testes. The females have external ovaries that appear on the epigonal organ, which is a primary lymphoid tissue in elasmobranchs.
The tiger shark is the only species of the family Carcharhinidae that is lecithotrophic viviparous, giving birth to live young. Female tiger sharks typically give birth in a nursery, which provides protection during the birthing process and continues to protect the young directly after birth in the absence of parents.
Gestation is approximately 13-16 months with a triennial reproductive cycle in Hawaii and Australia.
Embryos of tiger sharks are fertilized internally and a yolk sac forms around them to provide necessary nutrients during the gestation period. As the yolk begins to run out near the end of the gestation, the embryo draws nutrients directly from the mother.
The tiger shark has a higher intrinsic rate of population increase than many other carcharhinid sharks. Litter sizes are relatively large, ranging from 10-82 pups. With a maximum of 82 embryos recorded, an average tiger shark litter consists of 26-33 pups. Many of these pups will not survive to adulthood.
Tiger sharks have no parental investment as mothers do not help their pups survive or find food or shelter. Male tiger sharks also play no role in the lives of their offspring.
Instead, tiger shark pups are born fully developed and independent with traits that help them survive without parents. This includes camouflage patterning and coloration to provide protection against predators, teeth to help capture prey, and speed to avoid predators. Tiger sharks also have relatively fast growth rates during early life stages. At birth, they range from 51-90 centimeters in total length and weigh 3 to 6 kilograms.
Tiger shark pups are born with tiger-like stripes on their back and a lightly colored yellow or white belly which allows them to blend in with the environment. These stripes fade as the juveniles reach adulthood, which is around 6 to 8 years.
Tiger sharks are some of the largest predators in the ocean and have few species feed on them. Some juvenile tiger sharks, however, fall prey to other sharks. Humans also fish for tiger sharks.
Tiger sharks serve as a host for remoras, which are small suckerfish. Tiger sharks and remoras share a commensal relationship as the remoras attach to the tiger sharks near the underbelly and use the sharks for transportation and protection. Remoras also feed on materials dropped by tiger sharks. Recently, copepods, specifically sea louse (Caligus oculicola), have also been discovered around the eyes of tiger sharks in Australia.
Although very unlikely, tiger sharks enter shallow, populated areas of coastlines and attack humans on rare occasions.
Tiger sharks are a popular gamefish, which are typically captured and released for sport. In some U.S. states, permits such as a saltwater fishing license, allow fishermen to collect the shark as a trophy. Fishing for these sharks is tiring as tiger sharks are very fast, strong, and not quickly or easily exhausted. Tiger sharks often perform aerial acts when hooked.
Globally, the tiger shark is caught by commercial, recreational, small-scale, and artisanal fisheries as a target species or incidental bycatch and is subject to illegal, unreported, and unregulated (IUU) fishing operations. The species is one of the major components in catches from shark control programs that target large shark species in Australia, South Africa, and more recently Reunion Island in the Western Indian Ocean.
The tiger shark is valued for its high quality fins, skin, liver oil, meat, and cartilage. The tiger shark has been increasingly exploited by fisheries since the 1950’s due to the increasing demand from the shark fin trade as the fins of this species are a common component of the Hong Kong fin trade.
Catches of tiger shark in directed shark fisheries have been documented for a number of regions including the western Atlantic, Brazil, Australia, Papua New Guinea, Peru, Taiwan, India, and Saudi Arabia.
The tiger shark is a common component of the U.S. east coast/Gulf of Mexico commercial shark bottom longline fishery, accounting for 8-36% of the catch. The fishery catches mostly juvenile and sub-adult tiger sharks, although some larger sharks are also taken.
In Australia, the tiger shark is targeted by commercial shark fisheries in northern New South Wales and in Western Australia. The species accounted for 3 tonne (t) and 5.9% of total catch of the Ocean Trap and Line Fishery in eastern Australia. However, catches by this fishery are probably smaller than landings from recreational fisheries in that same area. In the Western Australia Tropical Shark Fishery, this shark was caught as a target species and annual catches averaged approximately 41 t between 2000 and 2004. This fishery was closed in late 2005. The Offshore Net and Line Fishery operating in the northern Australia catches the species incidentally (27 t in 2012), although mesh size is assumed to prevent capture of greater numbers. This shark is also taken in the Southern and Western Demersal Gillnet and Demersal Longline Fishery in Western Australia with a catch of 112 t reported in 2005-06. The Tiger Shark is a bycatch in trawl fisheries although normally in small numbers and there are few records of catches for these fisheries. The Australian Commonwealth Trawl Sector reported a total catch for the species of 4.7 t from 2004-2011.
The tiger shark is relatively common in the Indonesian shark fishery and contributed 5.2% of the total shark biomass of catches from between 2001 and 2006. The tiger shark is also commonly caught in the seamount gillnet and longline fishery off the west coast of India, where 242 t and 144 t of various shark species were taken during 2010 and 2011, respectively, but species-specific catches were not recorded. The Tiger Shark is caught occasionally in the longline fisheries of Costa Rica, Mozambique, and Saudi Arabia and by purse seiners in the Indian Ocean. Although little species-specific catch data information is available for the Arabian Seas area, the high level of level of fishing pressure in the region is of concern with steep increases in both small-scale and industrial fishing effort between the 1990s and 2000s.
In tuna longline fisheries, the species is typically caught in small numbers relative to pelagic sharks and is often not reported. Between 2007 and 2013, an average of 54 t was landed annually by tuna longline boats regulated by the International Commission for the Conservation of Atlantic Tuna. Tiger shark represented less than 10% of the total bycatch of all shark species in each of the management zones of the U.S. pelagic longline fishery. In the Panama longline fishery, the tiger shark represented 1.6% of shark catches of the estimated total catch of 109,500 t of various sharks since the mid-1980’s. In the Central and Western Pacific, the tiger shark is caught in low numbers (0.025 sharks per set) by tuna longline boats from most countries operating in that region. The tiger shark is a common target of recreational fisheries in the United States, Australia, and South Africa. Approximately 96% of the catch in USA waters are released alive. In the New South Wales Gamefish Tournament, tiger shark catches were approximately 8 t per year between 1993 and 2005. Recreational fishing may account for mortality in the tiger shark population in other countries, although catches are unmonitored.
Artisanal fisheries and IUU fisheries are also likely to be catching tiger shark, however information about landings from these fisheries is scarce as they remain mostly unmonitored. The tiger shark is commonly caught in artisanal fisheries in the tropics and subtropics, including in Mexico, Panama, Brazil, and a few African countries. In Bangladesh, landings of 4.5 t represent on average 1.36% of total catch. There is evidence that the species has been overfished by Indonesian fishing boats at Ashmore and Cartier Islands, and Scott Reef in northern Australian waters. This area had been targeted by Indonesian fishermen since the 1800’s but fishing was banned in 1988 and 2000, respectively. A survey in the region showed the absence of tiger shark at reefs historically fished despite years of protection whereas they were found present at nearby atolls that had been always protected from fishing. The species comprised 19% of the total shark biomass and 7.4% of total catch in numbers from Indonesian and Taiwanese IUU fishing vessels.
The tiger shark is a target species of shark control programs in Queensland and New South Wales, Australia, in South Africa, and more recently at Reunion Island. In Australia, the Queensland Shark Control Program (QSCP) captured 4,757 tiger shark individuals between 1993 and 2010 and the species represented approximately 10-30% of total catch in the northern locations of the QSCP between 1964 and 2007. Standardized catch rates from 1964-2007 for the QSCP in northern Queensland showed an increase in the relative importance of the tiger shark, from approximately 10 to 30% of total catch. This pattern is most likely due to the move in fishing gear from nets to drumlines. In southeast Australia, the tiger shark was commonly captured by the New South Wales Shark Meshing Program from 1950-2010 with approximately 30 sharks per year between 1950 and 2008, representing approximately 10% of the common shark species caught by the program in each of its locations. In South Africa, the KwaZulu-Natal beach protection program has caught approximately 50 individuals annually from 1978-2003. Since 1989, sharks caught alive are released; however, fishing mortality of the tiger shark in nets is 27% of captures.
In Australia, the Queensland Shark Control Program showed declines in catch rates since the 1980’s and in New South Wales, evidence of a decline was also seen in the last 20 years. Additionally, a significant reduction of the proportion of mature sharks in catches over 60 years suggests shifts in population structure and raises concerns over possible effects from this program on the Tiger Shark population off New South Wales. The decline off eastern Australia is likely to continue while the shark control programs off Queensland and New South Wales remain active.
In the U.S. fisheries of the Western North Atlantic, observer surveys variously recorded increases in tiger shark relative abundance and no change in abundance. In South Africa, the beach protection program showed a 3% increase per year in tiger shark catch rates. The increasing rates in the Western North Atlantic and South Africa seem consistent with the pattern observed in the first 20 years in Queensland and the interpretation of such upward trends should be made with caution.
In the Arabian Seas region, the tiger shark has been assessed as Vulnerable based on a suspected decline of at least 30% over the past three generations based on levels of exploitation, with the continued demand from the shark fin market suspected to result in further population reduction in the future.
Globally, the tiger shark is suspected to have declined by close to 30% over the past three generations (53-68 years) due to exploitation from commercial, recreational, and unregulated fisheries, as well as shark control programs. A further population reduction is suspected over the future three generation lengths (2018-2086) based on current levels of exploitation that are likely to continue into the future.
As such this species is assessed as Near Threatened and is close to meeting Vulnerable A2bd+3d.
Currently, the total number of tiger sharks worldwide is unknown.
Given the wide range of the species and the localities of the shark control programs, the tiger shark is suspected to have undergone an overall population reduction of close to 30% globally over the past three generations (53- 68 years) based on actual levels of exploitation from commercial, recreational, and unregulated fisheries, as well as shark control programs.
A further population reduction is suspected over the future three generation lengths (2018-2086) based on current levels of exploitation that are likely to continue into the future.
The tiger shark has relatively fast growth rates and large litters, but the likely triennial reproductive cycle reduces its ability to recover from fishing pressure. The tiger shark has been shown to be at risk in the Arabian Seas region from fishing pressure and from some shark control programs in other regions. The widespread distribution of this species increases the likelihood that it will survive increasing levels of exploitation in certain areas.
Records of tiger shark catches by many fisheries globally are still largely unknown. The species is not commonly caught in large numbers by most commercial fisheries and its catch is rarely recorded. Long-term trends of tiger shark catch rates are available from regional shark control programs and United States fisheries observer programs. Available trends in catch rates are based on analyses of the long-term shark control programs and on observer surveys from the Western North Atlantic. Consequently, there is a lack of adequate data for stock assessment, definition of population structure, and documentation of overall global population trends for the tiger shark.
In the Western North Atlantic, data from observer surveys taken between 1960 and 2000 from the Northeast Fisheries Science Center showed an upward trend of the relative abundance of the tiger shark with an increase of 6.7% per year since the 1980’s. Catch-per-unit-effort (CPUE) logbook data indicated a slow decline from 1986 to 2000 in tiger shark relative abundance. When logbook and observer data were combined, the relative abundance declined slightly then increased. The Shark Bottom Longline Observer Program also showed an increase of 8% per year in tiger shark relative abundance between 1994 and 2013. However, the Pelagic Observer Program from the Southeast Fisheries Science Center showed no change in abundance for the same period.
In northeast Australia, the Queensland Shark Control Program (QSCP) has used a combination of nets and drumlines to target large sharks since 1962. The standardized catch rate of tiger
sharks in northern Queensland increased until the 1980’s and then decreased by the 2000’s to approximately 66% of its original value. This trend in catch rate suggests a possible decline in the population between 1964 and 2007. The CPUE of tiger sharks showed an overall declining trend for the QSCP between 1993 and 2010, with the most significant decline in southern Queensland.
In southeast Australia, New South Wales has operated a netting program since 1937. The CPUE of tiger sharks showed marked fluctuations in the first four decades of records, and did not significantly change between 1950 and 2010, although a downward trend in CPUE was observed in the last two decades. The size frequency of tiger sharks caught by the program has changed over 60 years with a significant reduction in the proportion of large mature individuals being caught. The recent decline in catch rate and decrease in the proportion of large individuals suggests changes in the population structure and raises concern over the effects the program is having on the tiger shark population off New South Wales. The New South Wales
game fishing tournaments reported a decline in CPUE from approximately 1.2 to 0.5 shark vessel per day between 1993/94 and 2004/05, with fishers still targeting tiger sharks during the tournaments, suggesting a decline in the population.
The decline off eastern Australia is likely to continue while the shark control programs off Queensland and New South Wales remain active.
In South Africa, the KwaZulu-Natal beach protection program has deployed large-mesh gillnets since 1952. There has been an annual increase of 3% in the CPUE of tiger sharks between 1978 and 2003. This pattern seems comparable to the pattern observed in the first two decades of the Queensland Shark Control Program in northern Queensland, but the interpretation of such upward trends should be made with caution.
In the Arabian Seas, a significant decrease in shark biomass, mainly carcharhinids, has been reported since the 1970’s from trawl surveys and interviews with fishers. The tiger shark was formerly common in Eritrea and Iranian Gulf waters, but interviews with fishermen have indicated large declines in landings. Surveys in the UAE have recorded a decline of approximately 90% in the landings of the tiger shark and the species has been absent from recent surveys in the Red Sea, where once it was reported to be common. In Pakistan and India, declines of 20-30% in the tiger shark have been recorded with an absence of individuals larger than 3 meters in length in catches. The tiger shark is suspected to have undergone declines of at least 30-50% in the Arabian Sea over the last three generations (53 years) based on current levels of exploitation. The tiger shark was assessed as Vulnerable A2cd+3cd in the Arabian Seas region and the decline is likely to be ongoing with the continued demand from the shark fin market suspected to result in further population reduction in the future.
There are no specific conservation or management measures in place for the tiger shark. However, there has been an increasing interest to intensify protection of the species in the Western North Atlantic.
The current Fisheries Management Program for the U.S. Atlantic and Gulf of Mexico includes quotas and fishing seasons to regulate catch of coastal shark species including the tiger shark. On the west and south coasts of Western Australia, a maximum size of 70 centimeters interdorsal length is applied for whaler sharks taken by recreational shark fishing, which includes the tiger shark. In Queensland, the maximum size allowed is 150 centimeters for all shark species and a possession limit of one shark of any species is imposed to recreational fishing. Similarly, in New South Wales, only one tiger shark can be taken per person per day.
Some countries in the Arabian Seas region, such as Kuwait, Saudi Arabia, Sudan, and the Maldives, have banned the targeted fishing for sharks, whereas others, such as Iran and the UAE, impose seasonal bans on shark fishing.