Hydropeaking effects of on the diet of a Neotropical fish community

The impact of hydropeaking by dams is still poorly understood. Studying the diet of fish subjected to that variation allows us to test the following hypotheses: 1) seasonal and daily changes in river flow, causes changes in the use of the feeding resources; 2) species presenting larger differences in diet between seasons will be those with larger diet changes due to hydropeaking; 3) hydropeaking effects will be more evident in species feeding on items that can be more affected by variable flows. Fish diet collected from the Grande River, downstream from Itutinga Dam, in January and July 2010, was characterized by the feeding index (IA). NMDS, ANOSIM and SIMPER analyses were used to compare the diets under different hydropeaking and season. Relationship among diet dissimilarity between treatments was tested using Pearson Correlation. Seasonality and flow effects were not resulted in changes in the diet of species (hypothesis 1 rejected). In July, there was correlation of differences in the diet between stable and hydropeaking periods with the divergence caused by seasonality (hypothesis 2 accepted). The invertivores guild was the most affected by hydropeaking effects (hypothesis 3 accepted). This is the first study in Brazil that evaluates hydropeaking effects on ichthyofauna.

Differences in diet; Flow fluctuation; Rio Grande fish; Invertivorous; Seasonality