Does the oscillation of the water volume of the reservoir influence in the same way, in fish diet?

Aim : To evaluate the fish feeding and to establish the preferential and secondary items of their diets, in order to determine the trophic guilds and to associate possible trophic structure variations in function of the water volume in Umari reservoir, Rio Grande do Norte, Brazilian semiarid. Methods: The fish were captured quarterly between February and November of 2013, with gill nets with different meshes, being the apparatuses exposed at 5:00 p.m., with removal at 5:00 p.m. The food items were identified using stereoscopic and optical microscopes and evaluated through the Feeding Index (IAi), being the results of this procedure used in food similarity analysis. The volume of the items was orderly in NMDS and the time differences were tested in PERMANOVA. Results: A total of 734 individuals belonging to 11 species were sampled, being analyzed a total of 258 stomachs and eight intestines. From the IAi values used in the trophic similarity analysis, the species were classified into five trophic guilds: detritivorous, insectivorous, malacophagous, carcinophagous and piscivorous. Conclusion: The oscillation in the water volume of the reservoir had influenced the diet of the insectivorous, malacophagous and carcinophagous guild, and not for the detritivorous category, which demonstrates that the water volume variations of the reservoir do not influence in the same way, the diet of the local ichthyofauna.