At least 60 different fish species make Fairfax County their home. Some of the species are native to the county while others are non-native, which means they have been brought into the county from other parts of the state, country or different countries.

Distribution of fish across the county can vary depending on the biology, tolerance to pollution or temperature and habitat preference of the fish species. Some fish species, like the Longnose dace (Rhinichthys cataractae), are found in streams in western portion of the county within highly oxygenated riffles while other fish species such as the Eastern Mosquitofish (Gambusia holbrooki) live in much warmer slack waters in the southeast part of the county.  By assessing the fish communities we can learn more about the health of our streams and Fairfax County as a whole.

The fish listed below were collected by the staff of Fairfax County's Stream Quality Assessment Program.