Browsing by Autor "Silvia Eugenia Barrera Berdugo"

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Changes of taxonomic and trophic structure of fish assemblages along an environmental gradient in the Upper Beni watershed (Bolivia)
(Wiley, 2006) Marc Pouilly; Silvia Eugenia Barrera Berdugo; Claudio Rosales
The distribution and the diet of 28 fish species were evaluated, during the dry season, in 12 streams of the Upper Beni watershed (Amazon basin, Bolivia). The 12 streams were of similar size (stream width and water depth) but situated on a gradient of altitude in the Andean and sub‐Andean areas. The environmental conditions in the stream changed in relation to the altitude. As altitude decreased, slope and water velocity also decreased, while temperature, conductivity, pH and the proportion of pools increased. Although the diets of the species were mainly based on two aquatic autochthonous food resources, invertebrates and sediment, species were classified into five trophic guilds: detritivores, algivores, piscivores, invertivores‐omnivores and aquatic specialist invertivores. In all streams invertivores dominated or co‐dominated with detritivores. The trophic structure of the assemblages, however, changed in relation to the environmental gradient. The fish species richness increased and the trophic composition became more diverse at lower altitudes, when slope decreased and temperature increased. At the same time, the relative number of invertivore species decreased, whereas the relative number of detritivore, algivore and piscivore species increased. Decreasing altitude appeared to play a role similar to increasing stream size along the longitudinal gradient. This could be explained by geomorphological and temperature variations that may generate environmental conditions favourable to an increase of productivity.
Hydro-ecoregions of the Bolivian Amazon: a geographical framework for the functioning of river ecosystems
(2002) J.G. Wasson; Silvia Eugenia Barrera Berdugo; B. Barrère; Delphine Binet; D. Collomb; Isabel E. Gonzales; F. Gourdin; Jean‐Loup Guyot; Giovanna Rocabado
We present in this chapter the regional approach of the BIOBAB project, whose aim was to define homogeneous regions as regards the ecological functioning of running waters. The approach consisted of identifying at different hierarchical levels the ecohydrological links between physical control factors and ecosystem structures. Such an approach should provide a global outlook of the natural diversity of aquatic ecosystems in the basin, and by understanding the distribution of the main functional types, to allow some spatial prediction of their most important physical characteristics and associated biota. We shall define, map, and briefly describe the "hydro-ecoregions" of the Bolivian Amazonian basin and present some important aquatic ecosystem characteristics about morphology, hydro-chemistry, and fish and invertebrate communities in the Andean zone. This work is the first attempt to regionalize running water ecosystems in South America, with the end objective to provide a geographical frame for management and conservation. / Nous présentons dans ce chapitre l'approche régionale du projet BIOBAB, dont le but était de définir des régions homogènes par rapport au fonctionnement écologique des eaux courantes. L'approche consiste à identifier à différents niveaux hiérarchiques les liens hydroécologiques entre les facteurs de contrôle physiques et les structures des écosystèmes. Une telle approche devrait fournir des perspectives globales sur la diversité naturelle des écosystèmes aquatiques au niveau du bassin, et par la compréhension de la distribution des principaux types fonctionnels, devrait permettre des prédictions spatiales de leurs plus importantes caractéristiques physiques et des peuplements associés. Nous définirons, cartographierons, et décrirons brièvement les "hydro-écoregions" du bassin Amazonien Bolivien et présenterons certaines caractéristiques importantes des écosystèmes aquatiques concernant la morphologie, l'hydro-chimie, et les communautés de poissons et d'invertébrés de la zone andine. Ce travail est la première tentative de régionalisation des écosystèmes d'eau courante en Amérique du Sud, avec pour objectif final de fournir un cadre géographique pour la gestion et la conservation.