Class: Elasmobranchii (cartilaginous fish); Superorder: Selachimorpha
Some species are critically endangered; CITES appendix I & II
There are 440 species of shark
Sleek predators of the sea
Sharks vary greatly in size and habit. Whale sharks are the largest of all fish and can grow up to 12m long and weigh up to 12,000kg. The smallest shark is thought to be the dwarf lanternshark, which is just 17cm long.
Sharks are efficient predators. They have a highly developed sense of smell, hearing and sight. They can scent their prey in the water from a great distance. Their sensitive eyes can see clearly even in the dim light of the ocean depths.
Sharks are carnivorous and eat fish, including other sharks. Large species may eat seals, turtles and penguins. Some sharks, like the whale shark and the basking shark feed on plankton.
Most fish lay eggs in the water which are then fertilised by the male. But shark eggs are fertilized inside the female's body. In most species, the eggs hatch inside the female and the babies (called pups) are born alive. Some kinds of sharks, like the catshark do lay eggs, ejecting them in flattened cases known as Mermaid's Purses.
Some sharks that give birth to live babies have as few as 2-3 pups at one time. Others have around 12 and some as many as 70-80. A new born shark is able to swim as soon as it is born and is immediately left to fend for itself by the mother.
What are the main threats?
Demand for shark fins
The growing trade in shark fins - often used to make an expensive Asian soup - has become a serious threat to many shark species. Sharks are caught, the fins are cut off and the rest of the shark is thrown back into the sea.
Other sharks die in fishing nets set for other fish (bycatch) and shark meat is popular in many parts of the world. All this means that some species of sharks are now endangered and critically endangered.
The increase of development, pollution and over-fishing have led to the loss of important marine habitats that support shark populations.
What is WWF doing?
WWF directly works to address the problem of overfishing throughout the world's oceans through its Smart Fishing initiative.
Specific projects aim to raise awareness of the plight of sharks, improve the management of marine protected areas and develop ecotourism projects which support sharks in their natural environment. A 2011 study by the Australian Institute of Marine Science found that a single reef shark in Palau generates nearly $2 million for the tourist industry over its lifetime.
Examples of WWF projects that specifically or indirectly target shark conservation:
How you can help
- Don't support overfishing! Only buy sustainable fish and seafood, look for MSC certification.
- Adopt a blue shark through WWF Canada, or a whale shark or a great white shark through WWF US.
- Spread the word! Click on the button to share this information with others via email or your favourite social networking service.