| Summary: | Riparian zones are intimately linked to aquatic ecosystems and affect a number of processes including the maintenance of many fishes species that feed directly on insect prey of both allo and autochtonous origin. Mimagoniates microlepis is a Glandulocaudinae species whose diet is broadly based on unsects. Registers mentioned that Mimagoniates species are generally opportunistic foragers, consuming prey approximately in proportion to what is available in the environment. Coastal streams from Mata Atlântica in the east cost of South America has been suffering drastic losses of natural cover because of forest cutting to supply the growing demands for food, development of agricultural fields, intensive cultivation of sugar cane and soya beans. In the present study we aimed to access how much the availability of insect prey changes along the stream course of a coastal stream from Mata Atlântica (southeast Brazil). We addressed if changes in the availability of prey insects are reflected in the diet of Mimagoniates populations occurring in different sites along the stream. We sampled prey availability and fishes at five sites with different degrees of canopy coverture (shaded vs. non shaded sites). We found that prey availability changes according to physical environmental variables (coverture, water velocity and substratum). Although adaptable to prey availability, relative importance of different insect groups changed in the diet of individuals according to sampling site, M. microlepis was not registered in sites without canopy coverture and allochthonous insect prey.
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