This study defined some population parameters for growth of the Red-bellied Piranha (Pygocentrus nattereri) in the Pantanal, based on the bimonthly length-frequency distribution of individuals in samples taken from October 2005 through August 2008 in the Negro River. The samples were taken by means of gill nets and cast nets, with meshes of 1.5–8 cm between adjacent knots. The standard length of the fish ranged from 10.2 to 30.2 cm with a mean of 20.51 ± 3.39. The gonadosomatic index (GSI) varied significantly among months (F = 5.45; p < 0.01), it was significantly higher from October to February, and was positively correlated and synchronized with day length (rs = 0.92; p < 0.01) and rainfall (rs = 0.70; p < 0.01). It was desynchronized from and not correlated with river level (rs = 0.12; p = 0.69). The GSI reached the highest values and ripe individuals were more frequent in December, prior to the months of highest river levels from February to April. The estimated growth parameters were L∞ = 31.8; k = 0.45; Rn = 0.204. In the Pantanal, P. nattereri has a life expectancy (6.9 years) compatible with the 7 cohorts indicated by the growth curve. Sexual maturation occurred at around 15.4 cm, after 1.6 years.
September 26, 2010
Heiko Bleher wrote on facebook on photo:
“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.” ?
the must to read about piranha systematics
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'.
Is it a nice fish Heiko is showing? No access to social networking from the office.
P.S. just noticed you also added this to the profile comments so have pasted this answer in there, too. Must edit that one!
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