Characins: Characiformes

Physical characteristics: River hatchetfish are about 1 to 2 inches (3.8 centimeters) long. The deep body is very narrow from side to side. The belly looks like a semicircle from the side, and the chest muscles are large. The pectoral fins are long and high on the body near the head. These fish are yellow to silver with a dark stripe running along the length of the body. The fins are clear.

Geographic range: River hatchetfish live in South America.

River hatchetfish can swim very fast to rise out of the water and catch insects flying above the water level. (Illustration by Patricia Ferrer. Reproduced by permission.)

Habitat: River hatchetfish live near the surface of slow water in creeks and swamps.

Diet: River hatchetfish eat worms, crustaceans (krus-TAY-shuns), or water-dwelling animals that have jointed legs and a hard shell but no backbone, and insects on the surface of the water but also capture flying insects.

Behavior and reproduction: River hatchetfish live in groups near the surface of the water. They can be aggressive or calm. To avoid predators and capture insect prey, these fish swim very fast to rise out of the water, then fly above the surface using their long pectoral fins. River hatchetfish spawn after a lengthy courtship. The female scatters eggs in the water or onto floating plants, and the male fertilizes them. The eggs then fall to the bottom or onto plants.

River hatchetfish and people: River hatchetfish are common in aquariums.

Conservation status: River hatchetfish are not threatened or endangered. ∎