Least Killifish (Heterandria formosa)

Description: 

Least Killifish are distributed in coastal drainages from North Carolina to Texas. They can be found in slow-flowing fresh or brackish waters with heavy vegetation. Like other Livebearers, males have a modified anal fin (gonopodium) that is used for internal fertilization. As their common name suggests, Least Killifish are one of the smallest fish in the Southeast, reaching no more than 1.5 inches.