Tidal creeks are the habitat of choice for Fundulus heteroclitus heteroclitus. They are also found in saltwater marshes, estuaries, and in sheltered shores where tides flow over eelgrass. The common feature between all of these habitats is that there is submerged vegetation where the fish can spawn and feed (Rutherford, 1996).
Fundulus heteroclitus heteroclitus is a remarkable fish. It has proven to be one of the most hardy and adaptable fish known. Most fish cannot survive for any period of time in waters as warm as 34° C. However, the mummichog can survive in this temperature for up to 63 minutes before falling victim to heat shock. It can also withstand temperature fluctuations from 6° C to 35° C (Abraham, 1985).
The mummichog also has a great tolerance to changes in salinity. Some mummichogs, such as the ones inhabiting the Chesapeake Bay area, prefer to live in freshwater and rarely, if ever, find themselves in salt water. Other mummichogs live along the coast in bays filled with seawater. The fish's upper limit for salinity is 106 - 120.3 ppt, while the average salinity of sea water is 32-33 ppt. This demonstrates the huge range of salinities that the mummichog can survive in (Abraham, 1985).