Gambusia affinis is native to fresh/low-salinity waters of the eastern and southeastern US and Gulf of Mexico, from New Jersey to central Mexico (Hoese and Moore 1977). They may be found in fresh water as far inland as Illinois (Ray et al. 1986).Mosquitofish now also occur throughout much of the world as a result of intentional and non-intentional introductions beginning approximately 100 years ago. Intentional introductions have largely been for purposes of mosquito control, although G. affinis is not considered to be any more effective against mosquitoes than most native mosquito-eating species (ISSG 2006). Gambusia affinis is a common inhabitant of lower salinity portions of the lagoon and associated upland freshwater systems. Salt marshes, mosquito impoundments, and mesohaline seagrass beds are among the habitats utilized by this species.