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Dangerous ocean predators, seen by many as cold blooded killers, sharks have a fearsome
reputation. However, there is more to their story than meets the eye!
Sharks are a special category of fish that live in every ocean in the world, mostly in
warm waters. Some even live in rivers and lakes. Some live near the surface, some live
in deep water, and some live on the ocean floor. Some sharks stay near shore or on coral
reefs, while others live in the open ocean.
Unlike fish that have bones, sharks have skeletons made of cartilage. Cartilage is a tough, flexible
material that is not as hard as bone. You have cartilage in your body, too! One place
you can find cartilage is in your ear. You can bend and move your ear with your fingers
but it will go back to its normal shape because of the cartilage inside.
There are many different species of sharks - more than 500 species are known - and they
vary in size from small sharks not much bigger than a person's hand, to the largest fish
in the world, the whale shark, which can grow up to 50 feet or 15 meters long.
Sharks come in many different shapes, too, although most sharks have streamlined bodies
shaped like torpedoes to help them glide more easily through the water. Some sharks have
flattened bodies that help them to hide in the sand. Some sharks have long noses or long
fins, some sharks have very big mouths, and some sharks - called hammerhead sharks - have
extremely wide heads.
Most sharks are carnivores, with thousands of sharp teeth. In fact, sharks may have up
to 3,000 teeth at one time! Their teeth are arranged in rows. When one tooth is lost,
it is replaced by another. Some sharks may lose as many as 30,000 teeth in their lifetime!
Most sharks have about five rows of teeth at a time, but the teeth in the front are
the biggest and do most of the work.
A few sharks, like the basking shark, are filter feeders instead: they swim with their
mouths wide open and strain tiny plants and animals from the water. It takes huge quantities
of plankton and small fish to feed these huge sharks.
Sharks are fish, and fish do not sleep the way that we do, but they do have active and
resting periods. Some sharks are able to rest motionless on the sea floor, but other sharks
have to keep moving in order to breathe.
Let's learn about some special species of sharks!
The Great White Shark is the largest predatory fish in the world. They regularly reach sizes
of 21 feet or 6.4 meters in length, although some sharks measuring over 26 feet or 8 meters
have been reported. They can be found in oceans all over the world, as long as the waters
are not too cold. Many people are afraid of great whites, and it is true that they are
responsible for more shark attacks on humans than any other shark in the world, but they
would rather not eat humans, much preferring prey like tuna, dolphins, whales, and seals.
The Whale Shark is the largest fish in the world, but it is a filter feeder instead of
a predator. It eats mainly plankton, krill, and small crustaceans, but it will also
eat small fish that get sucked into its mouth. Whale sharks live in warm, tropical
waters, and are easily recognized by their spotted skins.
Hammerhead Sharks are a group of shark species that are recognized by the strange shape of
their heads! They use the wide 'hammer' on the front of their heads to help them catch
their favorite food - stingrays - by trapping them against the sea floor. Most species of
hammerhead are small, but the Great Hammerhead can reach lengths of up to 20 feet or over
6 meters.
Many people are afraid of sharks, and think that sharks will attack any time they see
you. For the most part, however, sharks do not attack humans. Out of hundreds of different
species there are, only 4 shark species have been involved in a significant number of attacks.
Fewer than five people a year are killed by sharks in the whole world!
In fact, many more sharks are killed by humans. It is estimated that about 100 million sharks
are killed by people every year due to fishing. Because of this, many shark species are in
danger of extinction! Now people are trying to protect sharks. They play a very special
role in ocean ecosystems, keeping fish populations from growing too large and helping the entire
food chain remain healthy. Without sharks, the entire ocean would suffer.
I hope you enjoyed learning about sharks today. Goodbye till next time!