Fish are vertebrate animals that live in water. Their body is covered in scales. Most fish lay eggs and have gills.
Australia is thought to have 4,500+ species of fish including the largest fish in the world, the whale shark. Given the huge area that Australia covers, the number of freshwater fish in Australia is relatively low. Australia is home to 30 introduced species of fish, including the mosquito fish (Gambusia) which is a live bearer (ovoviviparous). Live bearers retain the eggs inside the female’s body, giving birth to live young.
The Queensland lungfish (Neoceratodus forsteri) is an ancient fish which does not have gills. Instead, the lungfish uses lungs in the same way as humans to meet their oxygen needs.