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Least Killifish


SCIENTIFIC NAME: Heterandria formosa

Characteristics: One of the smallest fish species in the world, Heterandria formosa has a stout body, small, upturned mouth, and a rounded caudal fin. A dark lateral stripe extends from the snout to the caudal fin. Faint bars project upward toward the back and occasionally downward toward the venter. Both sexes have a large black dot at the base of their dorsal fin, but only the female has a dot on her anal fin. The body is the color of straw, and the dorsal fin is light orange or yellow distal on the black dot.

 ADULT SIZE: 0.5 to 1.2 in (12 to 30 mm)

DISTRIBUTION: The least killifish occurs sporadically across southern Alabama from the Chattahoochee River drainage in Houston County to Fowl River, a western tributary to Mobile Bay. Recent sampling efforts indicate that this species occurs considerably further inland in Alabama than was previously believed (Martin, 1978; Boschung, 1992). In 1990 and 1995, we collected least killifish 92 miles upstream of Mobile Bay in an overflow pool of the lower Tombigbee River near Jackson, Clarke County. This record was subsequently broken in 1994 when Royal D. Suttkus, a longtime collector of Alabama fishes, took several species at Evan’s lower bar on the Alabama River, Wilcox County, approximately 120 miles upstream of Mobile Bay. William Mike Howell recently reported to us his observation of H. formosa in ponds near the Choctawhatchee River, Geneva County.

HABITAT AND DESCRIPTION: The least killifish occurs along weedy margins of deep, plant-filled blackwater habitats of the Southern Pine Hills and Coastal Lowlands of Alabama. Heterandria formosa is a daytime surface feeder, and its diet consists mainly of microcrustaceans and occasionally plant material (Reimer, 1970). Aquarists have cultured this species for its diminutive size and tolerant nature, including an ability to survive at temperatures ranging from 50° to 90°F (10º to 32° C) and the fact that it will readily sustain itself on water fleas (Daphnia). Axelrod and Schultz (1971) report that breeding females in aquariums drop two or three fry a day for 10 days and begin another reproductive cycle approximately four weeks afterwards.

REMARKS: Agassiz (1885) listed the type locality as Mobile, Alabama.

ORGINAL DESCRIPTION: Agassiz described the least killifish in 1855.

Heterandria means different male.
Formosa means beautiful or finely formed.

The copyrighted information above is from Fishes of Alabama and the Mobile Basin.

Note: In Alabama, it is illegal to stock or move a bass or any fish, mussel, snail or crayfish to any public water without a permit.

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