Abstract
A total of 312 adults of matrinxã were captured bimonthly, between 2011-2012, in two sites of the rio São Francisco: immediately downstream of the Três Marias Dam (site 1) and in the confluence with the rio Abaeté (site 2). Specimens of Brycon orthotaenia from site 2 presented higher values of total length (32.24 ± 5.70 cm for females and 26.64 ± 3.79 cm for males) and body weight (506.66 ± 332.17 g for females and 267.36 ± 145.84 g for males), when compared with the site 1. In site 2 was registered the highest GSI means (9.97 ± 2.96 for females and 0.93 ± 0.52 for males), compared with the site 1 means. Reproduction period occurred from October to February. Unlike site 2, no spawned females or spent males were captured in site 1. Significant differences were found between females and males in site 2 (χ2 = 26.84, df = 1, P < 0.05). Physical-chemical parameters of the water presented higher values in site 2. The canonical correlation test indicated that the reproduction of males is less susceptible to environmental factors than that of females. These results show that B. orthotaenia finds favourable conditions to reproduction just in site 2.
Highlights
The impacts of dams on aquatic ecosystems have been a topic for discussion, especially relating to fish communities (Antonio et al, 2007; Taylor et al, 2014)
Considering that there are no studies to evaluate the impacts of damming and the importance of tributaries on the Brycon orthotaenia life-history traits, this study aims to analyse the reproductive ecology of this species in two sections of the upper rio São Francisco, immediately downstream from the Três Marias Dam and in the confluence with a free dam tributary in Brazil
Specimens of Brycon orthotaenia captured from site 2 showed statistically higher values of total length and body weight compared to females and males captured from site 1
Summary
The impacts of dams on aquatic ecosystems have been a topic for discussion, especially relating to fish communities (Antonio et al, 2007; Taylor et al, 2014). The Três Marias is a large dam located in southeastern Brazil and was built in 1960 in the upper rio São Francisco for power generation and flood control. In the power generation process, the colder water from the hypolimnion (3°C colder) is released in the river, causing thermal and hydrodynamic changes that impact fish reproduction just downstream of the dam (Weber et al, 2013). Recent studies have shown the importance, for fish reproduction, of tributaries downstream from dams, acting as alternative routes for migratory species and minimising unfavourable water conditions (Antonio et al, 2007; Arantes et al, 2011; Weber et al, 2013; Freitas et al, 2013)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
