Influência da dieta sobre a abundância de Moenkhausia dichroura (Characiformes, Characidae) no reservatório de Manso, Estado de Mato Grosso Diet influencing abundance of Moenkhausia dichroura (Characiformes, Characidae) in Manso Reservoir, State of Mato Grosso, Brazil

Este estudo teve por objetivo avaliar a dieta e abundância de Moenkhausia dichroura Kner, 1858 após a formação do reservatório de Manso, Estado de Mato Grosso. A dieta foi comparada espacial (montante, reservatório e jusante) e temporalmente (fase I, primeiro ano do represamento e fase II, quarto ano do represamento). Conteúdos estomacais de 392 indivíduos foram analisados e a dieta foi descrita através da representação volumétrica dos recursos alimentares. A montante a espécie mostrou tendência à insetivoria (V% = 51,46 de insetos aquáticos na fase I e V% = 56,07 de insetos terrestres na fase II), no reservatório à zooplanctivoria (V% = 77,11 e V% = 64,73 de microcrustáceos, nas fases I e II, respectivamente) e a jusante à herbivoria (V% = 56,02 e V% = 62,84 de vegetais, nas fases I e II, respectivamente). Constatou-se diferença espacial significativa na dieta (Kruskal-Wallis; H = 197,11, p This study aimed to analyze the diet and abundance of Moenkhausia dichroura Kner, 1858, after the filling of Manso Reservoir, State of Mato Grosso, Brazil. The diet was compared spatially (upstream, reservoir and downstream) and temporally (phase I, first year after damming and phase II, fourth year after damming). Stomach contents of 392 fishes were analyzed and the diet was described through volumetric representation of the food categories. Upstream the reservoir this species showed tendency to insectivory (V% = 51.46 of aquatic insects in phase I and V% = 56.07 of terrestrial insects in phase II). In the Reservoir it showed tendency to zooplanktivory (V% = 77.11 and V% = 64.73 of microcrustaceans, in phases I and II, respectively) whereas downstream the reservoir to herbivory (V% = 56.02 and V% = 62.84 of plants in phases I and II, respectively). We verified significant spatial differences in the diet (Kruskal-Wallis; H = 197.11, p < 0.05). Significant temporal differences was verify between diet of the individuals of upstream I and upstream II (test a posteriori - multiple comparison; p < 0.05). There was an abrupt increase of M. dichroura abundance during the studied period, mainly during the fourth year after damming, inside the reservoir. This fact seems closely related to the high abundance and availability of zooplankton in the dammed environment in addition to the ability of the species to exploit this resource