The eastern mosquitofish (Gambusia holbrooki) is a species of freshwater fish, closely related to the western mosquitofish, Gambusia affinis. It is a member of the family Poeciliidae of order Cyprinodontiformes. The eastern gambusia is the most widespread exotic freshwater fish in Australia and one of the most widely introduced freshwater fish in the world (dwer.wa.gov). The eastern mosquitofish is native to the eastern and southern United States from Florida to Delaware and inland to Alabama and Tennessee.