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Previous story Are there more dangerous piranhas lurking in the depths of a Louisiana lake? Next story
Published on June 1, 2021 9:36 AM

by Sarah Olson - The Oregon Herald

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World Stories Search World World Index
 
Although often described as extremely dangerous in the media, piranhas typically do not represent a serious risk to humans. Most piranha attacks on humans only result in minor injuries, typically to the feet or hands, but they are occasionally more serious and very rarely can be fatal.
 
A piranha mysteriously turned up in a Louisiana lake — and officials are on the hunt for others that may be skulking in the water.

The red piranha, a species native to South America, was caught last week at the University Lakes in Baton Rouge.

But piranhas aren't supposed to be found anywhere near Louisiana. But the find led wildlife officials to believe it was illegally kept as a pet and released into the lake.

All piranha species are illegal to possess or sell in Louisiana.

Now, wildlife officials are investigating whether there could be more lurking in the University Lake system.

Piranhas vary extensively in behavior depending on the species. Piranhas, especially the red-bellied, have a reputation as ferocious predators that hunt their prey in schools. Recent research, however, which 'started off with the premise that they school as a means of cooperative hunting', discovered they are timid fish that schooled for protection from their own predators, such as cormorants, caimans, and dolphins. Piranhas are 'basically like regular fish with large teeth'. A few other species may also occur in large groups, while the remaining are solitary or found in small groups.

A piranha is freshwater fish that inhabits mostly South American rivers, floodplains, lakes and reservoirs. Although often described as extremely predatory and mainly feeding on fish, their dietary habits vary extensively, and they will also take plant material, leading to their classification as omnivorous.

Although generally described as highly predatory and primarily feeding on fish, piranha diets vary extensively, leading to their classification as omnivorous. In addition to fish , documented food items for piranhas include other vertebrates , invertebrates , fruits, seeds, leaves and detritus. The diet often shifts with age and size. Research on the species Serrasalmus aff. brandtii and Pygocentrus nattereri in Viana Lake in Maranhão, which is formed during the wet season when the Pindaré River floods, has shown that they primarily feed on fish, but also eat vegetable matter. In another study of more than 250 Serrasalmus rhombeus at Ji-Paraná River, 75% to 81% of the stomach content was fish, but about 10% was fruits or seeds. In a few species such as Serrasalmus serrulatus, the dietary split may be more equal, but this is less certain as based on smaller samples: Among 24 S. serrulatus from flooded forests of Ji-Paraná River, there were several with fish remains in their stomachs, but half contained masticated seeds and in most of these this was the dominant item. Piranhas will often scavenge, and some species such as Serrasalmus elongatus are specialized scale-eaters, feeding primarily on scales and fins of other fish. Scale- and fin-eating is more widespread among juvenile and sub-adult piranhas.

Piranhas lay their eggs in pits dug during the breeding season and swim around to protect them. Newly hatched young feed on zooplankton, and eventually move on to small fish once large enough.

A piranha, lightly grilled, served as food in the Peruvian Amazon

A souvenir piranha Piranha teeth are often used as tools themselves or to modify other tools . This behavior has been documented among several South American tribes, including the Camayura and Shavante in Brazil and the Pacahuara in Bolivia. Piranhas are also popular as food. They are often considered a nuisance by fishers since they steal bait, eat catches, damage fishing gear and may bite when accidentally caught.

Piranhas can be bought as pets in some areas, but they are illegal in many parts of the United States, and in the Philippines, where importers face six months to four years in jail, and the piranhas destroyed to prevent proliferation in the latter.

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 Although often described as extremely dangerous in the media, piranhas typically do not represent a serious risk to humans. However, attacks have occurred, especially when the piranhas are in a stressed situation, such as the dense groups that may occur when the water is lower during the dry season and food is relatively scarce. Swimming near fishermen may increase the risk of attacks due to the commotion caused by struggling fish and the presence of bait in the water. Splashing attracts piranhas and for this reason children are more often attacked than adults. Being in the water when already injured or otherwise incapacitated also increases the risk. There are sometimes warning signs at high-risk locations, and beaches in such areas are sometimes protected by a barrier.

Most piranha attacks on humans only result in minor injuries, typically to the feet or hands, but they are occasionally more serious and very rarely can be fatal. Near the city of Palmas in Brazil, 190 piranha attacks, all involving single bites to the feet, were reported in the first half of 2007 in an artificial lake, which appeared after the damming of the Tocantins River. In the state of São Paulo, a series of attacks in 2009 in the Tietê River resulted in minor injuries to 15 people. In 2011, another series of attacks at José de Freitas in the Brazilian state of Piauí resulted in 100 people being treated for bites to their toes or heels. On 25 December 2013, more than 70 bathers were attacked at Rosario in Argentina, causing injuries to their hands or feet. 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. In February 2015, a six-year-old girl died after being attacked by piranhas when her grandmother's boat capsized during a vacation in Brazil.

Reputation Various stories exist about piranhas, such as how they can skeletonize a human body or cattle in seconds. These legends refer specifically to the red-bellied piranha.

A common falsehood is that they can be attracted by blood and are exclusively carnivores. A Brazilian legend called 'piranha cattle' states that they sweep the rivers at high speed and attack the first of the cattle entering the water allowing the rest of the group to traverse the river. These legends were dismissed through research by Hélder Queiroz and Anne Magurran and published in Biology Letters.

Theodore Roosevelt When former American President Theodore Roosevelt visited Brazil in 1913, he went on a hunting expedition through the Amazon Rainforest. While standing on the bank of the Amazon River, he witnessed a spectacle created by local fishermen. After blocking off part of the river and starving the piranhas for several days, they pushed a cow into the water, where it was quickly torn apart and skeletonized by a school of hungry piranhas.

Roosevelt later described piranhas as vicious creatures in his 1914 book Through the Brazilian Wilderness.

Physical Description
Red-bellied piranhas are red on their undersides from chin and cheeks to belly. The head and body are various shades of gray; their sides are flecked with bright silver scales. The piranha's distinctly rounded and snub-nosed profile serves a function.

Beneath the high forehead are powerful muscles that attach to a short, stout lower jaw fitted with triangular, razor sharp teeth, which interlock neatly with a matching set above. This design allows piranhas to bite down with incredible force and shearing ability. However, these formidable teeth are not usually visible, being covered by thick, fleshy lips.

Size
They can grow to be a little over a foot long and weigh up to 4 pounds .

Native Habitat
Red-bellied piranhas are found throughout the low elevation regions of the Amazon River basin. They inhabit both still and moving sections of the vast fresh-water Amazon River basin system.

Food/Eating Habits
In the wild, a good portion of their diet consists of fins nipped from the tails of larger fish. Additional items on a piranha's menu can include bits of flesh, whole small fish, insects, aquatic invertebrates and occasionally, plant material in the form of figs and other ripe fruit.

At the Smithsonian's National Zoo, red-bellied piranhas receive a gelatin diet , smelt, shrimp, herring and earthworms.

Social Structure
They tend to travel in schools of 20 or more individuals.

Reproduction and Development Red-bellied piranha reproduction begins with a courtship display involving swimming in circles. These piranhas are nest builders, with males creating bowl-shaped crevices in the sediment where eggs are placed. The eggs are laid in clusters and are attached to submerged aquatic vegetation. It is theorized that spawning could potentially correlate to the Amazon's wet season.

Sleep Habits
Smaller piranha search for food during the day, while larger fish tend to be more active at dawn and dusk.

Lifespan
Red-bellied piranhas have a lifespan of 10 years or more.