Trophic aspects of the ichthyofauna: impoundment effects and sampling sufficiency

Abstract

Seasonal flow changes have major influence on the functioning and integrity of aquatic ecosystems. Flooding periods are important for maintaining biodiversity in these ecosystems and also increase the availability of shelter and food resources. Hydroelectric plants constructions causes several changes in the aquatic environments that will consequently change the dynamics of the local fauna. Dams interrupt migration routes, retain sediment and nutrients in the upstream region, and interfere with the quality and availability of food resources for fish downstream the dam. Stomachal content studies of fishes allows the distinction of trophic groups, helps to understand the trophic structure and the relationships between the components of a community. As feeding is a dynamic process, it can generate changes in the trophic structure of communities due to changes in ecological conditions. In order for robust inferences to be made through the information provided by stomach content analysis studies, it is necessary that the number of individuals collected is sufficient to describe the species' diet appropriately. In this work, we discuss how the impacts generated by the installation of hydroelectric plants affect the trophic structure of the fish community in the regions of influence of a dam (Chapter 1), and we used three species of fish as a model to evaluate the sampling sufficiency for the description of the diet (Chapter 2).