Mummichog Identification Guide
How to recognize the stout, bar-sided Mummichog of Atlantic coast salt marshes and tell it from similar killifish.
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Key identification features
- Stout, thick-bodied killifish with a blunt, rounded head
- Olive-brown to dark green back, lighter belly
- Numerous thin, pale vertical bars on the sides of males; females plainer with faint spots
- Single dorsal fin set well back on the body, with a rounded tail fin
- Small, upturned mouth
- Thick caudal peduncle and a heavy-set overall build
- Rounded pectoral and pelvic fins
- Typically 5-10 cm
Common look-alikes
- Striped killifish: shows bold, continuous dark horizontal stripes rather than the mummichog's thin vertical bars.
- Sheepshead minnow: has a deeper, more rounded body and a steeper head profile than the more cylindrical mummichog.
- Banded killifish: more slender bodied with thinner, more numerous vertical bars and a less blunt snout.
Where you'll see one
Common in salt marshes, tidal creeks, and brackish estuaries along the Atlantic coast of North America from the Gulf of St. Lawrence to Florida, extremely tolerant of fluctuating salinity, temperature, and oxygen levels that few other fish can handle.
Frequently asked questions
How do I tell a mummichog from a striped killifish in the same tide pool?
Striped killifish show bold horizontal stripes, while mummichogs have thin, faint vertical bars instead.
What body shape confirms a killifish is a mummichog rather than a banded killifish?
Mummichogs are stockier and more thick-bodied, while banded killifish are slimmer with more numerous, thinner vertical bars.