Introduction: The floodplains of the large Amazonian rivers are very productive as a result of seasonal fluctuations of water levels. This favors the fishes as they are provided with a wide range of habitats and food resources; Aim: In this study, we identified the trophic structure of fish assemblages in the upper river Urucu area (State of Amazonas -Brazil), observing seasonal changes determined by the hydrological cycle; Methods: Samples were collected with the aid of gillnets, during the flood season (April/2008) and the dry season (August/2008) in areas upstream and downstream of ports of the Urucu river within the municipality of Coari, Amazonas, Brazil; Results: 902 individuals of seven orders, 23 families and 82 species were collected. Fishes were more abundant in the dry season than in the flood season, and the piscivores and carnivores (Serrasalumus rhombeus and Osteoglossum bicirrhosum) were the most significant trophic categories in the dry season whereas piscivores and insectivores (Serrasalumus rhombeus, Bryconops alburnoides and Dianema urostriatum) were more abundant in the flood season. The trophic diversity, dominance and evenness were very similar in all sampling periods and show lower values than taxonomic index patterns, except for the trophic dominance in the dry season. Taxonomic diversity and dominance were higher in the flood season if compared to the dry season, but figures were quite uniform and there were no great discrepancies between seasons. Conclusion: We found through our studies that the dry and flood seasons work as regulatory factors of abundance of fishes of certain trophic categories in the Urucu river, what can be possibly explained by the availability of resources and the food spectrum of each category.
Resumo: Introdução:As áreas inundáveis dos grandes rios amazônicos são muito produtivas, como resultado das flutuações sazonais no nível da água, favorecendo os peixes que passam a dispor de um amplo espectro de habitats e recursos alimentares; Objetivos: Neste estudo, identificamos a estrutura trófica das assembléias de peixes do curso superior do rio Urucu (Amazonas -Brasil), observando mudanças sazonais determinadas pelo ciclo hidrológico; Métodos: As coletas foram realizadas com auxilio de baterias de malhadeiras, no período de cheia (abril/2008) e seca (agosto/2008), em áreas a montante e jusante de portos localizados no rio Urucu, no município de Coari, Amazonas, Brasil; Resultados: Foram coletados 902 indivíduos compreendidos em sete ordens, 23 famílias e 82 espécies, a abundância de peixes no período da seca foi superior ao período da cheia. Piscívoros, onívoros e carnívoros foram as categorias com abundância mais elevada na seca; sendo essas mesmas categorias, incluso o grupo dos detritívoros, mais abundantes na cheia. Bryconops alburnoides, Dianema urostriatum e Serrasalumus rhombeus foram as mais abundantes no período da cheia e Osteoglossum bicirrhosum, Serrasalumus rhombeus e no período da seca; Conclusão: Constatamos através de nossos estudos a importância dos ...