Ah the wonderful creatures of the sea. Fish are aquatic vertebrates. This means they have a bone structure that separates them from invertebrates. Their gills allow them to breath under water. Their fins propel them through the sea. The combination of gills, fins and habitat in the water make them uniquely different from other animals on the planet.
They spend all their lives in the water, whether it is the sea or the rivers. Scientists believe there are more than 24,000 different species of fish. However, because it is so difficult to identify and track all the fish in the sea, this is only, at best, a guess. There are certainly many more fish to be discovered, especially in the deepest and darkest part of the oceans.
Apart from the Tuna and Mackerel sharks, fish are typicaly cold-blooded animals. Do not confuse the dolphin and the whale for a fish. Whilst they do swim and live in the ocean and have fins, they are actually mammals. They breath air with lungs just like humans and need to come up for air every so often. They are warm blooded and feed babies with milk.
Another group typically confused as fish is the Jelly Fish. Whilst they have, confusingly, the word ‘fish’ in their name, they are in fact not a fish at all. This is because they do not have any bones. They are invertebrates. Most fish, apart from sharks, have skeleton made of bone.
The biggest fish is the Whale Shark. Whale Sharks can be up to 16 metres (51 feet) long! The smallest recorded fish is the Stout Infant Fish which are as small as 8 mm (1/4 inch)!
