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Pygocentrus nattereri KNER, 1858

Red Bellied Piranha

SynonymsTop ↑

Pygocentrus altus Gill, 1870; Serrasalmo ternetzi Steindachner, 1908


Pygocentrus: from the Ancient Greek πυγή (puge), meaning ‘tail, rump’, and κέντρον (kentron), meaning ‘sharpo  point, thorn, spine0, in reference to the serrated abdomen.

nattereri: named for Austrian naturalist Johann Natterer (1787-1843).


Order: Characiformes Family: Serrasalmidae


Currently accepted to occur throughout much of the Amazon basin (Brazil, Ecuador, Peru, Bolivia and questionably Colombia) as well as the Río Essequibo (Guyana and Venezuela), some smaller, coastal drainages in north-east Brazil/the Guianas plus further south in the Río Paraná (Brazil, Paraguay and Argentina) and Río Uruguay (Brazil, Uruguay and Argentina).

Type locality is ‘Cuiabá and Mato Grosso, Brazil’.


Found in most habitat-types across its range including major river channels, smaller tributaries, oxbows, floodplain lakes, and artificial lakes formed by dams.

Maximum Standard Length

250 – 350 mm.

Aquarium SizeTop ↑

Suitable only for public installations or the very largest private aquaria with an aquarium measuring 240 ∗ 90 ∗ 60 cm or equivalent the minimum requirement for a group.


Some aquarists maintain this species in bare-bottomed arrangements for ease of maintenance but standard aquarium gravel or sand are both suitable substrates. Other décor is basically down to personal taste but plants may be eaten, especially if the fish decide to spawn. Lighting is relatively unimportant and can be dim to strong as preferred.

Pygocentrus spp. typically produce a lot of waste so the use of one or more over-sized external filter is essential. If possible buy units with inbuilt heaters or at least fit a sturdy heater-guard as adults have been known to damage submerged equipment. Sump systems also work well and the heater can be housed within.

Aim to change 30-50% of the tank volume each week and exercise extreme care when performing such maintenance or when netting the fish for any reason.

Water Conditions

Temperature20 – 28 °C

pH6.0 – 7.5

Hardness36 – 215 ppm


Pygocentrus spp. are not exclusive carnivores and are more accurately described as opportunistic generalists.

The natural diet consists not only of live fishes but also aquatic invertebrates, insects, nuts, seeds and fruits. Each jaw contains a single row of sharp, pointed, triangular teeth which are used like blades to puncture and tear but equally chop and crush.

They also attack sick or dying fishes, feed on the fins of larger species, and scavenge carcasses, but assaults on live animals entering the water are very rare and mostly relate to accidental biting or cases in which they’ve become trapped in small pools during dry periods, i.e., when food is scarce and the fish present in high densities.

In the aquarium juveniles can be offered chironomid larvae (bloodworm), small earthworms, chopped prawn and suchlike while adults will accept strips of fish flesh, whole prawns/shrimp, mussels, live river shrimp, larger earthworms, etc.

This species should not be fed mammalian or avian meat such as beef heart or chicken since some of the lipids contained in these cannot be properly metabolised by the fish and may cause excess fat deposits and even organ degeneration.

Similarly there is no benefit in the use of ‘feeder’ fish such as livebearers or small goldfish which carry with them the risk of parasite or disease introduction and at any rate tend not have a high nutritional value unless properly conditioned beforehand.

Behaviour and CompatibilityTop ↑

Best-maintained alone although adults tend to leave much smaller fishes alone if well-fed. In very large aquaria similarly-sized species may not be killed outright but their fins are likely to be viewed as food.

It’s often said that wild P. nattereri hunt in voracious packs but usually only juveniles group together in numbers. Older individuals exist in loose aggregations and form dominance hierarchies so purchasing a single specimen or group of 5-6+ is recommended, with the latter preferable.


P. nattereri is relatively easily to breed. Sexual maturity is reached at around a year of age and 10-15 cm in length. Unless you can find a sexed pair start with 6+ and allow a pair or two to form naturally. In some cases spawning has been initiated by large, cool water changes whereas in others it occurred without intervention.

As males come into sexual condition they become isolated from the rest of the group and excavate a patch of substrate using the mouth and caudal-fin. Aquatic plants may also be cropped if present and the resultant ‘nest’ is defended against other males.

Receptive females demonstrate interest by mouthing the substrate around the nest, and when ready to spawn both male and female darken in body colour. Eggs and spawn are deposited in several batches and guarded by the male, sometimes assisted by the female. In large aquaria multiple pairs may spawn simultaneously.

The eggs hatch in 2-3 days with fry free-swimming by the fifth. At this point it’s best to siphon them into smaller sponge-filtered set-ups. Several meals of Artemia nauplii/microworm and water changes of ~10% tank volume are required daily.

The fry become increasingly cannibalistic as they grow so should be moved to progressively larger aquaria in batches of similar size. Think carefully before taking on such a project, however, as you could end up with 1000+ young piranhas with very little sell-on value.

NotesTop ↑

Famed as a rapacious predator capable of rapidly stripping flesh from bone and a danger to any animal entering its native waters P. nattereri is among the most notorious freshwater fishes in the world.

As a result displays featuring this “bloodthirsty” creature are found in most public aquaria, grisly Hollywood movies have been released, and the species has subsequently become popular in the aquarium trade.

According to Herbert Axelrod (1976) the myth began when American president Theodore Roosevelt made a visit to Amazonian Brazil in 1913. He was accompanied by many journalists and the Brazilians organised a number of publicity stunts, one of which was that the president would ‘discover’ a river which would then be named after him. A tributary of the Río Aripuanã previously known as the Río da Dúvida (River of Doubt) was chosen and is today still referred to as the Río Roosevelt or Río Teodoro.

When Roosevelt arrived at the river the Brazilians had a surprise prepared; a stretch of several hundred yards had been netted off and for a number of weeks fishermen had been catching hundreds of adult piranhas and isolating them there. They told the president that he and his men shouldn’t enter the water as they would be eaten alive by vicious fish. Naturally this news was met with scepticism, so a cow, variously quoted as being “sick”, “old” and “in season” was introduced. Some even say its udders had been sliced open. This caused a spectacular feeding frenzy among the trapped, starving piranhas and newspapers were filled with stories of terrifying, flesh-eating fishes, but there remains not a single record of wild piranhas killing a human being.

Thankfully informed captive maintenance of piranhas and their relatives has undergone a relative boom over the last 15 years with a number of websites and forums now dedicated to the subject.

Many different species are available but the majority are wild caught, costly and thus beyond the means of most hobbyists. P. nattereri is however farmed in numbers with coin-sized juveniles sold rather cheaply for a fish requiring specialised and ultimately expensive care. For the enthusiast it makes an excellent aquarium subject but considerable thought and research are essential prior to purchase.

The name ‘piranha’ is commonly applied to all members of the genera Pygocentrus, Serrasalmus, Pristobrycon, Pygopristis, and Catoprion but in truth is only applicable to the first.

Pygocentrus spp. are thus often referred to as ‘true piranhas’, and are also the fishes referred to as ‘piranha’ (‘caribe’ in Venezuela) in their countries of origin with most of the others known as ‘pirambeba’. All are members of the family Serrasalmidae, a group currently comprising 16 genera including some other well-known ones like Metynnis, Myleus, Colossoma, and Piaractus.

Their taxonomy is confused and continues to undergo revision with Serrasalmus and Pristobrycon in particular presenting a number of identification problems. Current knowledge suggest the existence of several clades (groups of closely-related genera) within the family of which the ‘piranha clade’ contains all piranhas/pirambebas plus the genus Metynnis (Ortí et al. 2008).

In terms of ‘true’ piranhas most modern workers continue to follow the nomenclatural system proposed by Fink (1993) in which there exist only three species; Pygocentrus piraya (Cuvier, 1819), P. cariba (Humboldt, 1821) and P. nattereri. While the identities of the first two remain in little doubt Fink was unable to accurately diagnose P. nattereri, and it remains uncertain whether the species represents a single evolutionary lineage or not. There is also the enigmatic P. palometa Valenciennes 1850, described from the Río Orinoco and still listed as valid by some sources, which is generally regarded a nomen dubium despite the occasional appearance on trade lists.

P. nattereri has proven difficult to identify for a number of reasons. For example, P. piraya and P. cariba are endemic to single river basins (the Río São Francisco, Brazil and Río Orinoco, Venezuela/Colombia, respectively) and possess morphological details allowing relatively easy diagnosis.

P. nattereri, however, has an incredibly wide distribution, while colour and patterning vary considerably depending on locality and even within fish from a single location. Colour is also known to vary with habitat-type; fish inhabiting blackwater environments tend to be darker with less red/orange than those from clear or white waters, although blackwater populations are apparently rare.

Morphology and patterning in adults can vary in terms of head and body shape, presence or absence of dark spots or reticulated markings on the flanks and fin pigmentation.

Such differences have led to some populations being described as distinct species, notably P. altus Gill, 1870 from the Upper Amazon and P. ternetzi Steindachner 1908 from the Río Paraguay. Although piranhas continue to be traded under both names, Fink (1993) studied over 100 specimens from different parts of the Amazon and Río Paraguay drainages and was unable to find any consistent character (shape, colour pattern, meristic counts) that could be used to define them according to origin. Having found all three species non-diagnosable he decided to synonymise P. altus and P. ternetzi with P. nattereri as the latter is the oldest available name for the group.

Though he admitted himself it was an unsatisfactory best option Fink’s classification is still in place today. In a later study (Fink & Zelditch, 1997) differences in body form between ‘northern’ and ‘southern’ populations of P. nattereri were observed but evidence that they represent different species was still insufficient.

A phylogenetic analysis using samples from many different localities may help to resolve some of the confusion but the huge scope of such a study appears to have been a major limiting factor to date.


  1. Kner, R., 1858 - Mathematisch-Naturwissenschaftliche Classe 32(22): 163-168
    Zur Familie der Characinen. Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften.
  2. Axelrod, H. R., 1976 - TFH Publications, Inc. Neptune City, NJ: 79-87
    Breeding Aquarium Fishes.
  3. Fink, W. L., 1993 - Copeia 1993(3): 665-687
    Revision of the piranha genus Pygocentrus (Teleostei, Characiformes).
  4. Fink, W. L. and M. L. Zelditch, 1997 - Copeia 1997(1): 179-182
    Shape analysis and taxonomic status of Pygocentrus piranhas (Ostariophysi, Characiformes) from the Paraguay and Paraná River basins of South America.
  5. Ortí, G., A. Sivasundar, K. Dietz, and M. Jégu, 2008 - Genetics and Molecular Biology 31(1): 343-351
    Phylogeny of the Serrasalmidae (Characiformes) based on mitochondrial DNA sequences.
  6. Reis, R. E., S. O. Kullander and C. J. Ferraris, Jr. (eds), 2003 - EDIPUCRS, Porto Alegre: i-xi + 1-729
    Check list of the freshwater fishes of South and Central America. CLOFFSCA.
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5 Responses to “Pygocentrus nattereri – Red Bellied Piranha (Pygocentrus altus, Serrasalmo ternetzi)”

  • Bojan Dolenc

    Heiko Bleher wrote on facebook:
    “This is the real Pygocentrus nattereri, from the type locality: upper Rio Guapore, Mato Grosso, Brazil. This species has almost never been seen in the aquarium hobby, and much less in public aquaria. Almost all Piranhas in aquaria named as P. nattereri are in fact Pygocentrus altus … — with Pablo Matias Viera Lind.” ?

  • Hi Bojan only part of the P. nattereri type series came from the rio Guaporé, the rest came from Cuaibá which is upper rio Paraguay I think?

    As far as I understand it the last revision of the group was by Fink (1993) and he found P. altus (upper Amazon) to be non-diagnosable from both P. nattereri (rio Cuaibá and rio Guaporé) and P. ternetzi (rio Paraguay) when specimens from across all three species’ ranges were compared, thus the other two were synonymised with P. nattereri as it was the first to be described.

    Also from Fink’s paper: ‘The extent and color of the belly pigmentation is variable ontogenetically, individually,m geographically, and according to water conditions in which the fish live’.

  • Bojan Dolenc

    Heiko Bleher wrote today on that topic:
    Géry never agreed with Fink, specially not lately. Unfortunately he could not see my recent work/published paper on this group (in the two recent PFK issues) – (nattereri – the true one almost no one has ever seen, nor is it in the hobby – stay smaller, much smaller).
    See PFK April and Spring issues 2012 for more details of all species – discribed and undescribed.

  • Heiko might be right, but those magazine articles surely don’t represent a review of the genus?

  • siksu

    Speaking the suitable tank size for Serrasalmus nattereri written above, I strongly disagree. Because of the size and shooling behaviour (this fish feels best if kept in groups at least 5-6, better 10 specimens), besides it’s messy fish, all things considered the MINIMUM TANK SIZE should be AT LEAST 150 cm FOR ONE SPECIMEN.

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