Morphological patterns of five fish species (four characiforms, one perciform) in relation to feeding habits in a tropical reservoir in south-eastern Brazil

Described are the ecomorphological attributes of five abundant fish species and their relationships to the feeding ecology in a tropical reservoir in south-eastern Brazil. A total of 140 individuals were used. All specimens were collected between October 2006 and September 2007. Nine ecomorphological indexes were used and patterns detected by principal components analysis. The carnivorous species (Oligosarcus hepsetus) showed higher relative height of mouth to the mouth width aspect. On the other hand, the herbivorous species (Metynnis maculatus) had a higher compression index to the relative height. Geophagus brasiliensis (perciform) exhibited a larger relative length of the head to the relative length of the caudal peduncle. The two Astyanax species (A. bimaculatus and A. parahybae), although with taxonomic and morphological proximities to each other, exhibited indications of morphological adjustments probably associated to adaptive divergence. Three well-defined trophic groups were confirmed by the cluster analysis. The ecomorphology was effective in predicting feeding habits and aspects of locomotion, and the eventual consequences of the impoundment may be triggering a morphological divergence between closely related species. The authors hope that knowledge with regard to the effects of these man-made ecosystems on ichthyofauna ecomorphology will be further elucidated in the coming years, perhaps providing advice for their implementation in future hydropower projects.