Shark

Sleek predators of the sea

Many people think that all sharks are ferocious, dangerous animals. This is untrue! There are more than 360 species of sharks, but just 3 kinds of shark (the great white shark, the tiger shark and the bull shark) are involved in most attacks on humans. In fact, a shark is more likely to be killed by a human than the other way around!

Class: Elasmobranchii (cartilaginous fish)

The first sharks lived around 400 million years ago, with most sharks developing during the Cretaceous Period (64 million years ago) – the time of the dinosaurs!

Big sharks, small sharks
Sharks vary greatly in size and habit. Whale sharks are the largest of all fish and can grow up to 12 m long and weigh up to 12,000 kg. The smallest sharks are the tiny pygmy sharks which are fully grown at 25 cm long.

Shark food
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. Blue sharks swim in leisurely circles when they are hungry and become increasingly excited when they sense food.

Baby sharks
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.

Because sharks cannot breed fast like other fish, it means that their numbers can be easily be reduced by too much fishing. This is why scientists believe that shark fishing should be regulated.

The growing trade in shark fins - often used to make an expensive Asian soup - has become a serious threat to many shark species.

Conservation concerns
Millions of sharks are killed each year by humans. Many are killed deliberately for their fins, which are made into shark's fin soup. This practice is cruel and wasteful, as 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. Shark meat is popular in many parts of the world. Some species of sharks are now endangered.

WWF is among other conservation organisations leading the fight to save the world's sharks. It is seeking the ban on certain kinds of fishing nets and working to regulate the trade in shark fins.