The family of small fresh-water fish known zoologically as Characidae and known commonly as Piranhas has a reputation for ferocity and voraciousness that is more legend than reality. That's not to say that piranhas are vegetarians, or that they are dainty eaters, it's more that everything most people know about piranhas is exaggerated at the minimum and untrue at the maximum. The myth that a school of piranhas can reduce a human or cow to an instant skeleton appears to have been started by American President Theodore Roosevelt's visit to Brazil in the early 20th Century. At that time local Amazonian fisherman, in a successful attempt to impress the President blocked off a tributary of the Amazon with nets and filled it with starving piranhas. They then chopped up a slaughtered cow and threw the pieces into the stream, thereby setting off a "feeding frenzy" which quickly reduced the carcass to bones and provided the inspiration for hundreds of bad horror films, including at least 6 films entitled Piranha, according to IMDb.
Pantanal. What all piranhas have in common is a mouthful of particularly sparp and efficient teeth which makes them very good predators, their small size notwithstanding. All species of piranhas have a single row of sharp teeth in both jaws; the teeth are tightly packed and interlocking and are employed for rapid puncture and shearing.
Although the name piranha is well-known outside South America, it's not very well known that humans eat many more piranhas every year than the other way around. In the Amazonian region of Brazil, as well as in the Pantanal in the Brazilian state of Mato Grosso do Sul, piranhas are a commercial food fish and are eaten in a number of ways - grilled, roasted, and in soups and broths. As the piranha is a small and relatively bony fish, it takes of number of them to serve a tableful of eaters - but as the rivers and streams of the region abound in them, they can be eaten in good conscious. And with a bit of a sense of revenge.