The δ 15 N composition of bottom-feeding fish (iliophagous = Apareiodon affinis, Cyphocharax nagelii, Prochilodus lineatus, Steindachnerina brevipinna and S. insculpta; detritivorous = Loricariichthys platymetopon and Liposarcus anisitsi; benthophagous = Satanoperca pappaterra and Hoplosternum littorale) and their primary food sources were investigated in the upper Paraná River floodplain during rainy seasons in different environments (lotic and lentic). Two hypotheses were tested: i) that the trophic position and isotopic values of the investigated organisms (fish and food resources) vary spatially; and ii) that trophic position and isotopic compositions differ among iliophagous, detritivorous and benthophagous fish. C 4 macrophytes, periphyton and phytoplankton were isotopically different in sites analyzed. Significant isotopic differences occurred in the species of each trophic category. Spatial differences were observed in the isotopic composition of P. lineatus and L. platymetopon, whose values were more enriched in the Paraná River and Pau Véio Lake. Significant spatial differences in trophic position were observed for L. platymetopon and H. littorale, which presented the highest values in the Paraná and Baía rivers, respectively. Trophic positions were significantly different among the species that composed each trophic category. These findings demonstrate that in energy-flow studies in detrital food chains generalizations concerning the grouping of fish into trophic categories and/or habitats should only be carried out after careful investigations of the local/specific trophic dynamics of the organisms.Keywords: bottom-feeding fish, trophic position, nitrogen stable isotope, Upper Paraná River floodplain. aquatic environments, as well as to trace the trophic relations involved in the strategy and ecological role of the species. Such information is fundamental for carrying out effective management and conservation tasks, which aim at maintaining fish populations at sustainable exploitation levels in the only dam-free section of the Paraná River in Brazilian territory. Therefore, the objective of the present study was to investigate the δ 15 N composition of bottom-feeding fish (iliophagous = Apareiodon affinis, Cyphocharax nagelii, Prochilodus lineatus, Steindachnerina brevipinna and S. insculpta; detritivorous = Loricariichthys platymetopon and Liposarcus anisitsi; and benthophagous = Satanoperca pappaterra and Hoplosternum littorale) and their potential primary food sources in the upper Paraná River floodplain during rainy seasons, testing the hypotheses that: i) the trophic position of the fish and the isotopic values of the organisms investigated (fish and food sources) vary spatially, and ii) trophic position and isotopic compositions differ among iliophagous, detritivorous and benthophagous fish.
Posição trófica de peixes exploradores de fundo na planície de inundação do Alto Rio Paraná