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the Legacy continues…………………….
Gregory R. Mann, Ph.D. {ret.}

Tiger Shark

“Galeocerdo cuvier”

Tiger Sharks are one of the largest sharks in the world. Adults commonly reach lengths of 3.3-4.3 meters and weigh between 385-635 kilograms. Length at birth varies from 51-76 centimeters. Males reach sexual maturity at 2.3-2.9 meters, while females mature at 2.5-3.5 meters. The largest adult Tiger Sharks are believed to attain a length of over 7.4 meters and weigh over 900 kilograms. Tiger Sharks are gray in color with vertical tiger-stripe markings which usually fade or disappear in adults. They can also be identified by their characteristic sickle-shaped teeth that are similar in both the upper and lower jaw. This species is a requiem shark with a short, blunt snout, labial furrows and large head. Tiger Sharks have a slender body behind the pectoral fins and low keels on their caudal peduncle and slender and long caudal fins. Tiger Sharks are found worldwide in temperate and tropical seas. They live in coastal and pelagic waters, from the surface to depths of about 350 meters. The Tiger Shark has a wide tolerance for different marine habitats, but seems to prefer turbid waters on or adjacent to the continental and insular shelves. It is often found in river estuaries, close inshore in coral atolls and lagoons.

These solitary hunters are nocturnal and move inshore into shallow waters at night to feed and then move back to deeper waters in the daytime. Research by the Hawaii Institute of Marine Biology has shown that Tiger Sharks have very large home ranges. Tiger Sharks with surgically implanted ultrasonic transmitters all swam more than 16 kilometers within 1 day of their release and it took between 2 weeks and 9 months for them to revisit the area where they were released. They are likely have the widest variety in their diet out of all shark species. These sharks are predatory animals primarily known for their voracious appetites. They seem to be indiscriminate in their food selection and are known to eat fishes, other sharks, sea turtles, mollusks and seabirds. They are also known scavengers. Examination of Tiger Shark stomach contents revealed such diverse items as animal antlers and ship garbage. This wide spectrum of food selection has often been interpreted as these sharks being indiscriminate feeders, however their feeding habits may indicate a highly specialized adaptation to their biology in that they are extremely large animals and need a lot of food. Their uniquely shaped teeth are highly evolved and allow them to feed on a variety of food items, which helps prevent food shortages that might arise in more selective feeders.

Tiger Sharks are ovoviviparous bearing between 10-82 pups per litter. Pups at birth measure between 0.5-1.05 meters. The pups are very slender with clearly defined vertical stripes which fade as they become adults. They grow quite slowly, which makes them vulnerable to declines in population due to over fishing. The eggs are retained within the body of the female in a brood chamber where the embryo develops, receiving nourishment from a yolk sac. This is the method of reproduction for the “live-bearing” fishes where pups hatch from egg capsules inside the mother’s uterus and are born soon afterward. Tiger Sharks are second only to the Great White Shark in the number of reported attacks on humans. Fortunately though, attacks are rare. In Hawaii, Tiger Sharks were responsible for several fatalities in the 1990’s, an average of one shark attack there per year. A low number considering the average number of drownings in Hawaii is 40. Its large size and voracious appetite, make the Tiger Shark an apex predator of the ocean. Because of their indiscriminate appetite, Tiger Sharks can be curious and aggressive towards humans in the water and therefore must be treated with extreme caution.

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