Abstract
The present study investigated energy allocation patterns in three fish species from the family Hemiodontidae (Argonectes robertsi, Hemiodus microlepis, and Hemiodus unimaculatus), before and after the construction of Lajeado Dam, Tocantins River, Amazon basin. Changes in the use of energy (between somatic and reproductive processes) were indirectly evaluated by means of temporal variations in fish body condition, feeding activity, visceral fat storage, and reproductive effort. Fish were collected from October 1999 to September 2004, in periods that preceded and followed the construction of the dam. We recorded significant changes in all ecological traits for the three analyzed species (for males and females). In general, there was an intense reduction in reproductive activity after river damming, whereas visceral fat and body condition increased consistently. In contrast, there was no clear trend in feeding activity (i.e., stomach weight), with little changes in species diet during the analyzed period. These results indicate that the impoundment changed the energy allocation process between somatic and reproductive activities, since fish started to allocate energy mainly to somatic processes. These changes may have a negative effect on the persistence of populations in Lajeado Reservoir, because improvements in somatic condition will not necessarily translate into increased fitness.
Highlights
Large impoundments, especially those for hydropower generation, are found in all Brazilian basins
Argonectes robertsi In Pre-impoundment periods, A. robertsi was captured mainly in upper sites; after the impoundment, most individuals were captured in the Lacustrine zone of the reservoir (Fig. 1)
There was a decrease in reproductive activity after the impoundment, while visceral fat storage and body condition increased
Summary
Especially those for hydropower generation, are found in all Brazilian basins. As many South American species present seasonal reproductive dynamics, it is common to observe temporal variations in the use of energy, including periods of accumulation (i.e., tissue formation) followed by periods of gamete production (Bailly et al, 2008; Santos et al, 2010; Peressin et al, 2012) Changes in such use are expected when rivers are dammed (Abujanra et al, 2009), since reservoirs change the availability of food resources (Mérona et al, 2003; Loureiro-Crippa & Hahn, 2006; Luz-Agostinho et al, 2006) and environmental triggers and conditions (e.g., duration and timing of floods, water flow, conductivity, and transparency) that stimulate and allow reproductive dynamics (Agostinho et al, 2004). Understanding changes in the use of energy, may help explaining the colonization process in reservoirs, since variations in the acquisition and use of energy determine the success of species in occupying the new environment
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