Gray Reef Shark

Sharks

Selachii

Sharks belong to a family of fish that have skeletons made of cartilage, a tissue more flexible and lighter than bone. Their bodies are rounded and tapering at the ends. They breathe through a series of five to seven gill slits located on either side of their bodies. All sharks have multiple rows of teeth, and while they lose teeth on a regular basis, new teeth continue to grow in and replace those they lose. Shark ‘skin’ is made up of a series of scales that act as an outer skeleton for easy movement and for saving energy in the water. The upper side of a shark is generally dark to blend in with the water from above and their undersides are white or lighter colored, blends in with the lighter surface of the sea from below. This helps to camouflage them from predators and prey. Sharks also have a very acute sense of smell that allows them to detect blood in the water from miles away.

Size The spined pygmy shark, a deep-sea shark at only about 7-8 inches, is one of the smallest sharks, while the whale shark is the largest shark, and fish, at about 50 feet in length.

Lifespan Although lifespan varies by shark species, most sharks are long-lived and generally tend to live for 20-30 years. Species like the spiny dogfish and the whale shark are believed to live for over 100 years.

Diet

Variety depending on shark species, including fish, crustaceans, mollusks, plankton, krill, marine mammals and other sharks.

Population

It is difficult to estimate population numbers since there are many different species spanning a large geographic area. However, overall shark numbers are on the decline due to the many threats they face in the wild.

Range

Sharks have adapted to living in a wide range of aquatic habitats at various temperatures. While some species inhabit shallow, coastal regions, others live in deep waters, ocean floors and the open ocean. Some species, like the bull shark, are even known to swim in both salt and fresh waters and deltas.

Behavior

Most sharks are especially active in the evening and night when they hunt. Some sharks migrate over great distances to both feed and breed. This can take them over entire ocean basins. While some shark species are solitary, others display social behavior at various levels. Hammerhead sharks, for instance, school during mating season around seamounts and islands.

Some shark species like the great white shark attack and surprise their prey, usually seals and sea lions, from below. Species that dwell on the ocean floor have developed the ability to bottom-feed. Others attack schooling fish in a feeding frenzy, while large sharks like the whale and basking sharks filter feed by swimming through the ocean with their mouths open wide and filtering large quantities of plankton and krill.

Reproduction
Mating Season Various times depending on the species.
Gestation 2 months to 2 years depending on the species. Some species lay eggs, some have young covered by a thin membrane, and others give birth to live young.
Number of offspring Depending on the species, could be 1-2 pups or more than 100 eggs or pups.
Soon after birth, sharks pups swim away to fend for themselves. They are born with fully-fledged sets of teeth and are able to take care of themselves.

Threats

Every year, sharks are killed in various fisheries, either intentionally for their fins and meat or accidentally as bycatch. Shark finning to provide for delicacies like shark fin soup is one of the biggest threats facing sharks. They are usually ‘finned’ alive and the body is thrown back into the water where the shark either bleeds to death or drowns. With bycatch, they generally become accidentally entangled in fishing lines or nets put out in the ocean to catch other species of fish, and when fishermen haul in their catch, the dead or dying sharks are thrown back into the water.

Defenders of Wildlife has been working to ban shark finning internationally. In Mexico, Defenders was successful in enacting a ban on shark finning.

Legal Status/Protection

CITES* (the great white shark, whale shark and basking shark are listed under Appendix II), **Magnuson Stevens Fishery Conservation and Management Act.

*Convention on International Trade in Endangered Species of Wild Fauna and Flora, an international treaty with more than 144 member countries. Appendix I species cannot be traded commercially. Appendix II species can be traded commercially only if it does not harm their survival.

**Magnuson Stevens Fishery Conservation and Management Act governs the conservation and management of ocean fisheries. This Act regulates U.S. fisheries and provides the U.S. management authority over fisheries in the exclusive economic zone and the continental shelf.

How You Can Help

Help sharks and other wildlife by adopting an animal today at our Wildlife Adoption Center.
Take Action for Wildlife at our Wildlife Action Center.