Effects of conservation status of the riparian vegetation on fish assemblage structure in neotropical headwater streams

Abstract

The aims of this study were to investigate the relationships between the riparian vegetation and fish assemblages (structure, composition and diet) in forested (Riparian Cover ≥80%; Canopy cover ≥90%) and deforested (RC < 80%; CC < 90%) headwater streams and to test how those assemblage characteristics respond temporally in streams with different conservation conditions. We sampled in five Neotropical headwater streams during dry and wet season in areas of natural and degraded riparian vegetation on central Brazil. The fish assemblage structure was related to the conservation status of the stream, and no differences were observed in the assemblages between seasons. Allochthonous food items represented 47% of the fishes’ diet, followed by items of unknown origin and autochthonous items. Only Astyanax sp. and Astyanax rivularis showed evidence of temporal diet variation. The consumption of a wide spectrum of food items was an outstanding feature, indicating the fishes’ capacity to adapt to ecosystem changes. Differences between natural and deforested streams demonstrated the importance of the riparian zone as an indirect selective force on diets and composition of fish communities in headwater streams, suggesting that changes in the structure and composition of riparian vegetation may significantly affect the integrity of fish communities.