Freshwater streams, lakes and flooded forests.
Trahiras are freshwater characiform fishes, inhabiting the rivers, streams, lakes and floodplains of South America. They are very common and are important to artisanal fisheries.
Most Trahiras are predators, feeding on other fishes. These fishes have a long gape that extends beyond the anterior portion of the eye socket, with numerous teeth on the palate. The body is long and cylindrical. Some are capable of breathing air and even can move over land from pond to pond.
Unlike some other members of the order Characiformes, Trahiras lack an adipose fin (the small fleshy fin located between the dorsal and caudal fins). They also have relatively few pectoral fin rays, only 9 to 14. Trahiras have five branchiostegal rays (the small slender bones that support the gill membranes).The origin of the dorsal fin is front of the anal fin and usually over the pelvic fins, however Erythrinus males have an elongated dorsal fin.
This family comprises three genera, Erythrinus, Hoplias, and Hoplerythrinus, and about 14 species. The maximum length in this family is 1.0 m, attained in the genus Hoplias, by H. macrophthalmus and H. lacerdae.