<P> The total number of piranha species is unknown and contested, and new species continue to be described . Estimates range from fewer than 30 to more than 60 . </P> <P> Piranhas are indigenous to the Amazon basin, in the Orinoco, in rivers of the Guianas, in the Paraguay--Paraná, and the São Francisco River systems, but there are major differences in the species richness . In a review where 38--39 piranha species were recognized, 25 were from the Amazon and 16 from Orinoco, while only 3 were present in Paraguay--Paraná and 2 in São Francisco . Most species are restricted to a single river system, but some (such as the red - bellied piranha) occur in several . Many species can occur together; for example, seven are found in Caño Maporal, a stream in Venezuela . </P> <P> Aquarium piranhas have been unsuccessfully introduced into parts of the United States . In many cases, however, reported captures of piranhas are misidentifications of pacu (e.g., red - bellied pacu Piaractus brachypomus is frequently misidentified as red - bellied piranha Pygocentrus nattereri). Piranhas have also been discovered in the Kaptai Lake in southeast Bangladesh . Research is being carried out to establish how piranhas have moved to such distant corners of the world from their original habitat . Some rogue exotic fish traders are thought to have released them in the lake to avoid being caught by antipoaching forces . Piranhas were also spotted in the Lijiang River in China . </P> <P> Depending on the exact species, most piranhas grow to between 12 and 35 cm (5--14 in) long . A few can grow larger, with the largest living species, the red - bellied, reaching up to 50 cm (20 in). There are claims of São Francisco piranhas at up to 60 cm (24 in), but the largest confirmed specimens are considerably smaller . The extinct Megapiranha which lived 8--10 million years ago reached about 71 cm (28 in) long, and possibly even 100 cm (40 in). </P>

Where do piranhas live in the united states
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