They are a noxious species! They were introduced to control mosquitos and other insects in there larval stages around housing developements and reserves. But it didnt work. World wide they have caused the extinction of over 25 fish species. And are proficient at breeding. They have spreed all over the world, including Nth American, SthAmerica, Australia and can put up with and breed in a variety of harsh habitats, including cold and warm water, low oxygenated waters, high polluted water ways, and even slightly saline water.