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 Tiger Shark

Image Credit: NOAA


 Tiger Shark
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 National Marine Sanctuaries Where Tiger Sharks Can Be Found:
  Papahānaumokuākea Marine National Monument
Hawaiian Islands Humpback Whale

 Related Environmental Issues:
  Point Source - Oil Spills
Non-Point Source - Runoff
Overfishing
Bycatch

 Activities Related to Tiger Sharks:
 

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Scientific Name: Galeocerdo cuvier

Category: Fish

The Tiger Shark gets its name from the dark vertical stripes and spots that appear on the young sharks. These markings generally fade and disappear in the adults. This Shark lives in tropical, sub-tropical, and temperate waters world-wide. In the Pacific, large populations are found around the Hawaiian Islands. The Sharks roam in the surface waters of harbors, shallow reefs, lagoons, and along coastlines where the waters are dark and murky. Sharks do attack people, but these attacks are rare. The International Shark Attack File reports that only 155 people have been attacked by the Tiger Shark since 1580. However, since the Tiger Shark is an indiscriminate eater and their sense of taste is not very well developed, if they bite you, they will eat you! Many people fear being attacked by a shark because these rare encounters have been exaggerated by Hollywood, especially in the movie Jaws.

Although known to reach 20-25 feet in length and weigh close to 2000 pounds, the average adult Tiger Shark is 3.25-4.25 m (10-14 feet) in length and weighs 385-635kg (850-1400 pounds). The Sharks can be blue to green to dark grey in color with a yellow underbelly. Their long fins help them to swim through the ocean. They have excellent eyesight because of a special layer of cells behind the eyes that improves their vision in darker, deeper, ocean waters. Their triangular shaped head has a blunt snout that widens toward the neck. This allows the shark to turn its head quickly from side to side while hunting prey. Through the use of small electrical sensors in the skin along their sides, the Tiger Shark can detect the movements of potential prey. This allows them to easily hunt at night. They have been known to reach 50 years of age, but generally live for twelve years.

Tiger Sharks have a low reproduction rate. The females mate on average only every three years. During mating, the males use their teeth to hold on to the females. The eggs are fertilized and develop internally within the females body. Most other marine organisms lay eggs that hatch outside of the female. After about 16 months, litters of 10-80 pups are born that are fully independent at birth. Newborn pups weigh 2.7-4.5kg (6-10 pounds) and are generally 51-76 cm (25-30 inches) in length. Litters are born from April through June in the Northern Hemisphere and November to January in the Southern Hemisphere.

Tiger Sharks usually hunt alone, at night in warm shallow water and return to the deeper ocean during the day. Scientists are still working out whether this shark migrates daily/seasonally to warmer waters because it is sensitive to the colder waters or whether they are just following prey that inhabits warmer water. However, in Hawaii the Tiger Shark often hunts during the day because it feeds on monk seals that are active during daylight hours. Tiger Shark teeth are very sharp and serrated (like a steak knife) to cut through the shells, bones and flesh of their prey. Like all sharks, lost teeth are replaced with new ones that move forward from inside their jaws. Tiger Sharks will eat just about anything. Their diet includes sea turtles, squid, fish, seabirds, mammals, and human trash like plastic, tires, baseballs, dogs, beer bottles, deer antlers, and even license plates! Although generally considered a slow and sluggish swimmer, when hunting prey, the Tiger Shark darts with great speed and becomes vicious when feeding.

Tiger Shark fins are used for medicine and are the source for shark fin soup. Shark cartilage shows some promise in the treatment of cancer. Their skin is used to make leather goods like wallets, but a sharkskin suit is made from a type of wool and not the skin of a shark. Since Tiger Sharks are harvested in great numbers from the sea, one would think that their population would decrease dramatically. However, scientists have found that in places where the adult population has decreased, there are a greater number of juvenile Tiger Sharks, somehow compensating for the adult loss.

A tagging project in Hawaii is being used to determine the geographic range of these sharks. Acoustic transmitters are attached to the larger sharks (actually embedded in their tissue) that allow scientists to track their movements with monitors placed on the seafloor. Some scientists have suggested that the Tiger Shark be put on the threatened list. However, the IUCN (International Union for the Conservation of Nature) does not currently consider this shark to be threatened and, the ICUN Red List of Threatened Species continues to place the Tiger Shark in the lower risk/nearly threatened category.




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 Sponsored by:
NASA logoNational Aeronautics and
Space Administration

(NASA Award NCC5433)
NOAA logoNational Oceanic &
Atmospheric Administration

(NOAA Award NA06SEC4690006)

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