Matt Clarke looks at Castelnau's piranha - the rarely seen Serrasalmus gibbus - which has recently been imported into the UK aquarium trade.
Piranha expert Frank Magallanes said: "The fish in the photo above is not "S. gibbus". By its size, it seems to fit S. eigenmanni or S. serrulatus a complicated group of fishes that fall into several historical scientific names based on locality and vague descriptions. The true S. gibbus is a elongated Serrasalmus species (not discoid as in the photo) and is elongation is between S. elongatus and S. rhombeus. Castelnau wrote four lines of descriptive words that could fit almost any Serrasalmus species. But present research by M. Jegu states the name is valid and the accompanying photographs in the citation do not fit the fish above."
"Another similar group to the above are Pristobrycon. The species it would most resemble is P. striolatus. Without being able to see the spotting on the body, it would be difficult to say for certain based on that photo."
Common name: Gold piranha, Castelnau's piranha, Gibbus piranha, Silver-scaled piranha
Scientific name: Serrasalmus gibbus Castelnau, 1855
Origin: Museum records show that the type specimens came from Goias in the Rio Araguaia basin in Brazil. Subsequent specimens have also been collected from the Rio das Mortes in the Mato Grosso, and the Maroni basin in French Guiana.
Size: FishBase reports a maximum size of 21cm/8", but this specimen was probably pushing 25cm/10".
Diet: Predominantly fish. Recent research on other species of wild piranha has suggested that they eat live, moribund and dead fish, as well as other foods, including plant material - so there's no need to offer live fish, most will readily accept frozen fish.
Aquarium: Best kept individually in a very spacious species tank. A piranha this big deserves a tank of at least 150cm/5' in length.
Breeding: This species has been bred in aquaria. In order to get a breeding pair, you will need to obtain a small group of juveniles, raise them together and allow them to pair-off naturally. Females are normally thicker and stockier than males. They become dark in colour prior to spawning and typically construct a pit, into which several thousand eggs may be laid. The male normally guards the brood.
Notes: The piranha family Serrasalmidae was split into a number of genera, with true piranhas in Pygocentrus, and others such as pirambebas, in Serrasalmus and other genera. Serrasalmus is the largest serrasalmid genus with around 24 species. The Serrasalmus species can be very tricky to identify, and there is little published information on the majority of species.
Availability: This one was on sale at Wharf Aquatics in Nottinghamshire last summer. It was imported as Serrasalmus gibbus by specialist fish wholesale Tom Halvorsen.
Price: This large specimen would have been imported in its own individual plastic drum container, to reduce the likelihood of it biting its way out. As a result, shipping forms the bulk of the fish's price at around 140 at Wharf.