August Elasmobranch of the Month: Tiger Shark
Author: Linda Weiss
Tiger sharks get their name from the vertical stripes and spots that run down both sides of their broad bodies. These markings are distinct, dark black when young. As the animal ages, these markings spread and fade, often appearing gray or light gray in adulthood. On some larger, older sharks, these patterns are barely visible. The topside of the shark is gray in color and cream to white on the underside. This shark has a very broad head with a rounded snout. Its eyes are large and black. The first dorsal fin is broad and begins behind the pectoral fins. The second dorsal fin is significantly smaller and located above the anal fin. An inter-dorsal ridge is present. The caudal (tail) fin has two, lobes with the upper lobe longer than the lower lobe. Tiger shark teeth, are shaped similarly in both the upper and lower jaws. They are curved, triangularly shaped with serrated edges. Tiger sharks grow to lengths of 5.5 m (18 feet) and weigh 907 kg (2,000 pounds).
Habitat and Distribution
Tiger sharks are found around the globe in tropical and temperate waters in the Atlantic, Pacific and Indian oceans. Their primary habitat is in coastal areas. They do migrate large distances, and regularly use the pelagic zone for these migrations. They also move inshore to more shallow water to feed at night and spend day-time hours in deeper waters. These sharks can be found in depths ranging from the surface to 350 m (1148 feet). Juveniles are also known to reside in bays and estuaries which offers more protection and smaller prey items.
The Tiger shark is known as the garbage can of the sea, for the variety of prey items, as well as inanimate objects it is known to consume. Its serrated teeth allow it to saw through the shells of sea turtles. Also, on their menu are fish, squid, dolphins, birds, crustaceans, and sharks. They will eat live prey as well as injured and dead prey. A variety of trash objects have been found inside the stomachs of these sharks, including license plates, bottles, bags, and tires.
Tiger shark with a sea turtle Image Credit: Daniel Thomas Browne
Tiger sharks reproduce ovoviviparously, where the embryos develop inside the mother initially nourished from egg yolks. After the yolk is gone, the embryo begins to drink uterine fluid to complete their development. The gestation period is roughly 15 months with litter sizes between 10-80 live pups.
The IUCN Red List of Threatened Species currently lists the Tiger shark as Near Threatened, with a decreasing population trend.
This shark species is targeted by both the commercial and sport fishing industries. The commercial fishing industry targets the Tiger shark for its liver, teeth, jaws, skin and fins. Orca, are the only known natural predator of the Tiger shark.
Bimini Shark Lab
The IUCN Red List of Threatened Species
Ferreira, L.C. & Simpfendorfer, C. 2019. Galeocerdo cuvier. The IUCN Red List of Threatened Species 2019: e.T39378A2913541. https://dx.doi.org/10.2305/IUCN.UK.2019-1.RLTS.T39378A2913541.en. Downloaded on 10 July 2020.