MUMMICHOG (FUNDULUS HETEROCLITUS) The Mummichog is an estuarine Killifish that can tolerate a wide range of salinities. It frequently occurs together with the Banded Killifish in fresh water marshes, swamps, backwaters, and areas of low salinity. It can tolerate rather high temperatures, up to 93 F at 14 ppt salinity. The general range of the mummichog is from northeastern Florida to the Gulf of St. Lawrence. The normal color of my Fundulus Heteroclitus is steel gray or brownish on the back and sides. This color gradually fades to white or yellowish on the stomach and breast. Most of the body is covered with a faint netlike pattern produced by the darkened edge of each scale. As the water temperature reaches from 68-70 F, and as the male and female mummichog achieve prime conditions, body changes take place--most noticeably in the tail. Small white or pale-blue spots, arranged in a vertical pattern on the males' sides, seem to glow on the steel-gray background of their bodies. The normally discrete spots in the caudal, dorsal, and anal fins become bright. A large, dark spot becomes very noticeable in the posterior parts of the dorsal and anal fins. In some specimens vertical blue bars in the posterior part of the body appear, and the fins take on gaudy yellow or yellow-orange margins. The color of the female changes little from the normal steel gray described earlier, but her body becomes fuller as it fills with eggs. The leading ray on the anal fin is long and quite opaque. The Mummichog consumes a variety of plant and animal matter including diatoms, amphipods, mollusks, crustaceans, small fishes, fish eggs, and sea grass fragments. It is widely used as an experimental animal, especially for studies of endocrinology. This Killifish is quite adaptable, and in nature adjusts to many variable conditions. It is a subject of scientific studies as it thrives in some of our nations most polluted waterways. Normal fishkeeping maintenance and care in a permanently set-up aquarium should give good breeding results. The Mummichog is rarely seen in aquarium stores. Photo by Aaron Norman