Abstract
Abstract: In order to assess the influence of the Três Marias dam on the reproduction of the white piranha, Serrasalmus brandtii, 1569 specimens captured from June 2011 to May 2012 in three sections of the São Francisco River basin were analyzed: section 1 = Três Marias reservoir (TMR); section 2 = São Francisco River (SFR) segment immediately downstream of TMR; and section 3 = SFR segment at the confluence with the Abaeté River. Total length (TL), body weight (BW), gonadosomatic index (GSI), and gonadal maturation stages were determined for each specimen, while vitellogenic follicle diameter, and absolute (AF) and relative (RF) fecundities were also determined for females. Reproductive activity, including spawned females and spermed males, was recorded throughout the year in the three river segments. Higher frequencies of females and males at the maturing/mature stage were found in the November/December and January/February, which coincided with the period of higher temperature, rainfall, and dissolved oxygen concentration. Mean GSI and vitellogenic follicle diameter were higher in sections 1 and 3 than in section 2 (P <0.05), while AF and RF were higher in section 1 (P <0.05) than in sections 2 and 3. The results of the present study showed that S. brandtii had lower reproductive performance in section 2, probably due to thermal disturbances caused by the dam, thus confirming the influence of dams on the reproduction of fish downstream from hydroelectric plant reservoirs.
Highlights
Most of the world’s major rivers have some kind of damming that causes negative impacts to entire fish communities (Olden & Naiman 2010)
In the São Francisco River in the Southeast Region of Brazil, negative impacts of the Três Marias dam on the reproductive activity of the ichthyofauna have been detected in migratory species, such as Prochilodus argenteus (Arantes et al 2010), Leporinus reinhardti (Weber et al 2013) and Brycon orthotaenia (Nunes et al 2015), and foraging species, such as Astyanax fasciatus and A. bimaculatus (Normando et al 2014), but there have been no studies evaluating impacts on typically sedentary species or species pre-adapted to lentic environments such as Serrasalmus brandtii
Females and males had statistically higher values for Total length (TL), body weight (BW), and gonadosomatic index (GSI) in the section immediately downstream from the Três Marias reservoir, than in sections 2 and 3 (Table 2)
Summary
Most of the world’s major rivers have some kind of damming that causes negative impacts to entire fish communities (Olden & Naiman 2010). Important for economic development, dams cause serious and irreversible impacts to the natural hydrological regime of rivers including altering the downstream flow (Agostinho et al 2010, Nunes et al 2015) Such impacts have been detected downstream of several hydroelectric plants in different parts of the world (Clakson & Childs 2000, Todd et al 2005, Olden & Naiman 2010). The white piranha, S. brandtii, is native to Brazil and endemic to the São Francisco River basin It belongs to the Serrassalmidae family (Mirande 2010), which includes piranhas and pirambebas, which are voracious carnivorous freshwater fish that are restricted to South America and occur in Brazilian reservoirs (Jégu 2003). Males of the species perform uni-parental care and the species is pre-adapted to lentic environments (Braga 1981, Agostinho 2003)
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