The Piranha fish is found predominantly in the Amazon basin, in the Orinoco, the Guiana rivers, Paraguay-Paranà, and in the São Francisco river systems. However, unfortunately, this species of fish has developed a reputation that it does not deserve.
Theodore Roosevelt described in his book Through The Brazilian Wilderness, about an incident where a school of Piranhas brutally devoured a cow within minutes, after having been starved for days, leaving behind only the skeleton of the unfortunate bovine. He also writes that they can snap off a finger of any person who dips his hand in the water. Tales such as these have accorded Piranhas the status of fearsome predators with an astounding hunting ability. However, most of these theories have been eventually disproved. They have no scientific bearing whatsoever. These fish swim in schools not to attack, but to protect themselves from predators.
Unfortunately, academicians and scientists have not done much to shatter these myths. One of the reasons may be that humans do not hunt and kill Piranhas in large numbers. The only threat that they seem to face is loss of habitat. It has also not been conclusively proven that they are huge contributors to the river ecosystem.
Scientifically called serrasalmus nattereri, these fish are usually 5.5 to 10.5 inches long, but ones that are 17 inches are also known. Similarly, their color also varies from silver to orange. Depending on the species, they can live from 3 to 10 years. When they are born, they feed on the river zooplankton. They move on to small fish once they become adults. These fish have the propensity to feed on carcasses of animals that lie on the riverbeds. However, this usually happens only if the water level is low or the fish are hungry. Those bred in captivity have generally been afraid of human presence, but there have been instances when people have put their hands in the tanks and been bitten. However, this could be attributed to the fact that the fish were under fed in the first place.
In Argentina, 70 bathers were attacked in 2013 by a school of Piranha. In the Brazilian state of Piauí, a hundred people were injured in a series of attacks over a period of time. Many lakes have warning signs to let bathers know of the imminent danger. These fish tend to attack in the dry season when there is scarcity of food and the water levels are low, which leads to a large population of them concentrating in the water than usual. These attacks may have also been caused because of the damming of rivers. Dams slow the flow of river water, which can cause an increase in piranha population, because these fish favor gentle stretches of water for breeding.
It provides a very fertile environment for the young fish to survive because of the presence of water hyacinths. They lay their larvae in submerged or floating waterweeds, which collects in slow-moving rivers. When rivers flood, much of this vegetation is swept away and this probably controls their populations. However, damming of the rivers prevents these floods. The vegetation offers protection for these nests of larvae, and the parents often "brood" over or guard them. The fish usually bite their victims once, ripping a chunk out of the person and leaving a round, crater-shaped wound with accompanying loss of tissue and bleeding. They mostly go for the extremities such as fingers and toes. A few victims have said to have got their toes amputated after being bitten, but this is still not enough justification to provide these fish with the 'man-eater' moniker.
It is illegal to store Piranhas in most states in America. Philippines also prohibits importing these fish, and the perpetrators can face a six months to four years jail term. However, if they have to be kept in captivity, then a minimum of 50 gallons of water at a temperature between 75 and 80 degrees Fahrenheit is required. When they are young, they must be fed normal fish food and freeze-dried bloodworms. As they grow bigger, they can be fed chunks of fish. It is recommended that beef be avoided because it is difficult to digest. It is a known practice in America for aquarium owners to pass off other similar-looking fish as Piranhas, most notably - Plecostomus Catfish, Silver Dollars, and Pacus.