Common Mummichog (Fundulus heteroclitus), Striped Killifish (Fundulus majalis)
Alternate common names for killifish: Mummy,
Color: Common mummichog - Olive green to blue back, white belly; males have irregular silvery bars or mottling. Striped killifish - Males have irregular vertical black bars along the sides; females have three horizontal bars, with the lowest bar divided into two.
Size: 5 to 7 inches long.
Habitat: Sheltered salt marshes, tidal creeks, brackish water.
Seasonal appearance: Year round; more abundant in spring, summer, fall.
The name killifish is often used to describe small fish of the Fundulus genus. In Rhode Island, at least two species of Fundulus are present: the common mummichog and the striped killifish. The body shape of these fish is standard for both species. Both have a rounded back and belly, a soft dorsal fin situated far back on the body, a thick and rounded tail, a flattened head, a blunt snout, and a small mouth.
The head of the striped killifish is slightly longer and thinner than that of the common mummichog. Although they are generally the same size, the striped killifish is slightly larger and more slender than the common mummichog. During the breeding season, the male striped killifish becomes brilliantly colored; its back turns black, its sides become golden orange, and its fins turn bright yellow. Although coloring also intensifies for the common mummichog, it remains paler than the striped killifish.
Life History and Behavior
Killifish live close to shore and rarely stray more than 100 yards from the shoreline. They are omnivores and scavengers, feeding in salt marshes on phytoplankton, mollusks, crustaceans, mosquito larvae, and dead fish. During the receding tide, they are often stranded in tide pools and puddles and can flop head over tail to reach the water when puddles dry up. It is believed that they can travel in this way for several yards. Killifish winter in tidal creeks where the salinity conditions are lower than in marshes, and they are often observed in a sluggish state, buried by up to 8 inches of mud.
Adapted from The Uncommon Guide to Common Life on Narragansett Bay. Save The Bay, 1998.