Striped Killifish

Fundulus majalis

The striped killifish is a small North American fish known for its distinct sexual dimorphism. Males display vertical black stripes on their elongated bodies, while mature females exhibit horizontal stripes, though juvenile females initially have vertical stripes. These fish typically reach lengths of up to 15 cm, with some individuals growing as long as 18 cm. They inhabit shallow coastal waters, including bays, estuaries, and coastal marshes, from New Hampshire to Florida and the northern Gulf of Mexico. Striped killifish are commonly found in marine and brackish environments, usually at depths of up to 1 meter. Divers might encounter these fish in temperate coastal waters, where they are known to feed on worms, small crustaceans, mollusks, and insects. They are not migratory and can be seen year-round. The species is notable for its ability to survive in tide pools, even flopping over land to reach the ocean when trapped. While they are not typically found in aquariums due to maintenance challenges, they are commercially fished. The striped killifish is classified as Least Concern by the IUCN. Divers observing these fish may notice their active swimming and aggregating behavior, particularly in tide pools. Despite their commercial use, they pose no threat to humans.