Physical: Mummichog range in color from olive-gray to green-brown, with dark silver horizontal stripes. F. heteroclitus have blunt, curved heads, and reach an average size of 4 inches. Juvenile F. heteroclitus are very similar to the mature Mummichog; the males lack the orange on their fins and have an olive color.
Habitat: This species ranges from the Gulf of St. Lawrence to northeast Florida. They shelter primarily in salt marshes, tidal creeks, and occasionally enter freshwater bodies. Juvenile F. heteroclitus spend much of their time in marsh tidal pools and open spaces until they are bigger.
Feeding: F. heteroclitus consume various plants and animals, including diatoms, amphipods, mollusks, crustaceans, and small fishes. Juveniles feed on small shrimp, larval insects, amphipods, zooplankton, as well as other smaller species that come into their area.
Breeding: Mummichog spawn from April until the end of August in a cycle correlating with spring tides (a tide just after a full or new moon). Eggs are laid at levels reached only by spring tides, and are deposited in hidden clutches of 10 to 300.