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 are born alive. For example, a great white shark only has four to 10 pups. Most other kinds of fish have hundreds of young.
Some sharks are pregnant for two to three years before giving birth.
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. Conservation concern 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.