食人鱼的攻击能力

Piranha teeth are often used to make tools and weapons by the indigenous population. Piranhas are also popular as food, although if an individual piranha is caught on a hook and line, it may be attacked by others.

Piranhas can be bought as pets in some areas, but they are illegal in many parts of the United States. It is illegal to import piranhas into the Philippines and violators could face six months to four years in jail.

The most common aquarium piranha is Pygocentrus nattereri, the red-bellied piranha. Piranhas can be bought fully grown or as young, often no larger than a thumbnail. It is important to keep Pygocentrus piranhas alone or in groups of four or more, not in pairs, since aggression among them is common, not allowing the weaker fish to survive, and is distributed more widely when kept in larger groups. It is not uncommon to find individual piranhas with one eye missing due to a previous attack.

Attacks
Attacks resulting in deaths have occurred in the Amazon basin. In the city of Palmas, Tocantins, 190 piranha attacks were reported in the first half of 2007. In 2011, a series of attacks in the Brazilian state of Piauí resulted in 100 people being injured. In the state of São Paulo, another attack in the Tietê River resulted in 15 injured people. In 2011, a drunk 18-year-old man was attacked and killed in Rosario del Yata, Bolivia.In 2012, a five-year-old Brazilian girl was attacked and killed by a shoal of P. nattereri. Some Brazilian rivers have warning signs about lethal piranhas. On 25 December 2013, 70 bathers were attacked in Argentina. And in February 2015, a six-year-old girl died after being eaten by piranhas when her grandmother's boat capsized during a holiday in Brazil.

According to one study in Suriname, piranha attacks tend to peak in the dry season when food is relatively scarce and the water levels are lower, leading to heavier than usual concentrations of fish in the water. Fatal attacks are rare, and most attacks take the form of individual nips and bites to extremities such as the feet and hands. Splashing tends to make piranhas more likely to attack, and children are often attacked for this reason.