Piranhas are freshwater fish native to South American rivers, known for their distinctive sharp teeth and powerful jaws. These fish belong to the family Serrasalmidae, which also includes the herbivorous pacu. While often portrayed as aggressive predators, their dietary habits vary widely across species, ranging from carnivorous to omnivorous. Many species are relatively small, yet their reputation has captured public imagination for centuries.
The Largest Piranha Species
The largest piranha species in the world is the black piranha, scientifically known as Serrasalmus rhombeus. It is recognized for its substantial size. While common names can sometimes be confusing, Serrasalmus rhombeus is frequently referred to as the redeye piranha, black piranha, or white piranha, with the latter name sometimes used for its juvenile silvery coloring.
Serrasalmus rhombeus can reach lengths of up to 18 inches (approximately 45.7 cm) in the wild, with some reports suggesting individuals can exceed 20 inches. Its maximum recorded weight can be up to 8.4 pounds (3.8 kg). It belongs to the genus Serrasalmus, which is considered one of the “true” piranha genera.
Physical Traits and Environment
The black piranha (Serrasalmus rhombeus) has a compressed body shape and a deep, broad back. Adults typically display a dark, grayish-black coloration, which contributes to their “black piranha” moniker, though juveniles may exhibit lighter, silvery tones. A distinctive feature in mature individuals is a deep red eye. Its teeth consist of a single row of sharp, triangular teeth in both jaws, designed for a scissor-like bite. The black piranha has one of the most powerful bites relative to its body mass among living piranha species, exerting a force of over 30 times its body weight.
It is widely distributed across northern South America, primarily inhabiting the Amazon and Orinoco River basins, as well as rivers in the Guiana Shield and northeastern Brazil. Serrasalmus rhombeus adapts to various aquatic environments, found in both fast-flowing river rapids and deeper, slower-moving sections of main rivers. It prefers warmer waters, typically ranging from 75°F to 80°F (24°C to 27°C). Unlike some other piranha species that prefer vegetated areas, adult black piranhas often occupy the open water column, hunting in deeper channels.
As a carnivore, the black piranha’s diet primarily consists of smaller fish, crustaceans, insects, and occasionally small mammals and lizards. It is an opportunistic feeder, known to scavenge on carrion. While generally timid towards humans, its powerful jaws and sharp teeth can inflict serious bites if provoked or when defending its territory, particularly during breeding season. Black piranhas are typically solitary and are known for their ambush predatory behavior, making swift passes at potential prey.