The eastern mosquitofish (Gambusia holbrooki) is a species of freshwaterfish, closely related to the western mosquitofish, Gambusia affinis. It is a member of the familyPoeciliidae of orderCyprinodontiformes. The eastern mosquitofish is native to the eastern and southern United States from Florida to Delaware and inland to Alabama and Tennessee, while the western mosquitofish has a larger distribution throughout the United States.