Conectividade e análise da estrutura taxonômica e trófica da ictiofauna em lagos do rio das Mortes, Mato Grosso - Brasil

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

This work describes the structure of fish assemblages in relation to environmental characteristics in two lakes with distinct levels of hydrologic connectivity associated to the lower Rio das Mortes, in the Bananal floodplain, Mato Grosso, Brazil. Tartaruga Lake is permanently connected to the main river channel, whereas Cocho Lake is connected to the river only during rainy season. Samplings were performed in quarterly surveys through two complete seasonal cycles, and yielded 114 species and 5607 individuals. Fish assemblage structure was analyzed using two approaches, taxonomic and functional, discussed separately in each chapter. Chapter I investigates fish assemblages in relation to taxonomic structure, with emphasis in the spatial-temporal variations and habitat characteristics. Chapter II describes the trophic structure of fish assemblages based on the relative abundance of trophic groups, determined by stomach content analysis of 59 species. Analyses based on taxonomic groups indicated that the lakes are distinct from each other in both spatial and temporal scale, and these differences are marked during dry periods. Greater variability in relation to environmental variables and fish assemblages attributes were found in the seasonally isolated lake. Additionally, environmental characteristics (mainly depth and water transparency) had influence on the patterns of fish assemblage composition and abundance. Results also suggested that the degree of connectivity determines the relationship between water transparency and temporal variation in fish assemblage organization in the sampled lakes. In relation to trophic structure analyses, results showed significant temporal variation in the proportions of trophic groups, which were also more pronounced in the seasonally disconnected lake. However, except for piscivores, it was not found significant spatial variation in relation to the relative abundance of trophic groups. Data suggest that increasing connectivity during rainy period homogenizes the trophic structure of fish assemblages, probably for allowing lateral migration between floodplain habitats and the main river channel. In conclusion, the data provided by this study highlight the central role of hydrologic connectivity in the organization of fish assemblages in floodplain lakes, mainly the seasonally isolated ones.

ASSUNTO(S)

variáveis ambientais ecologia araguaia river basin araguaia, rio, bacia neotropical fish ecologia aquática pulso de inundação connectivity estrutura trófica conectividade trophic structure ecologia de peixes peixes neotropicais environmental variables

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