Rainwater Killifish (Lucania parva) - Native

Rainwater killifish.

A 1.5-inch rainwater killifish, which differs from others in its family by its large scales, each surrounded by a faint dark outline.

Identification. Large eye. Large scales (fewer than 30 lateral line scales) with faint dark outline around each. Dorsal fin set farther forward. (Base of first dorsal ray ahead of base of first anal ray. Distance from beginning of dorsal fin to beginning of tail fin about equal to distance from beginning of dorsal fin to middle of eye). Soft dorsal rays 11-12. Males typically have a dark spot on lower leading edge of dorsal fin. Dark grayish-green on the back fading to white on the belly.

Size. Commonly 1 to 1.5 inches. State survey max. size 2 inches. Max. reported size 2.8 inches.

Distribution. Patchy distribution along the Atlantic Coast and Gulf of Mexico from Massachusetts to Texas. In Connecticut, they are found in tidal creeks, backwaters and marshes, primarily east of the Connecticut River. They are typically uncommon, but may be locally common in some areas.

Rainwater killifish distribution map.

All maps created in 2009. See CT DEEP Fish Community Data for updated distributions.

Habits. Prefer quiet shallow waters of estuaries and salt marshes, usually near vegetation. Can often be found swimming in schools near the surface. Are tolerant of a wide range of salinity. Will occasionally enter fresh water above estuaries. Can be captured with a small-mesh dip net or seine.

Comments. Where numerous, rainwater killifish are thought to be an effective control of mosquito larvae. Due to their small size and patchy distribution, the range of this species is not well documented in Connecticut.


Text and images adapted from Jacobs, R. P., O'Donnell, E. B., and Connecticut DEEP. (2009). A Pictorial Guide to Freshwater Fishes of Connecticut. Hartford, CT. Available for purchase at the DEEP Store.