What is a fish?
All fish are called vertebrates.A person who studies fish is called an ichthyologist.The difference between a male and female fish is,the different shapes of there bodies,the colouring,or in some cases no visible signs at all.Most fish breathe through there gills,but there are some fish that breathe through there lungs.Fish are slimy,they secrete mucus from their skin,this is important as it helps to protect against parasites and diseases,it covers up wounds to prevent infection.This also helps the fish to move through water faster.Some fish species release toxins which ward off creatures,but other fish species use their slime to feed their young.Below is a video clip of a tranquil tropical fish aquarium
