Variability in the carbon isotope signature of Prochilodus lineatus (Prochilodontidae, Characiformes) a bottom‐feeding fish of the Neotropical region

The spatial and seasonal variability of stable carbon isotopes in detritivorous Prochilodus lineatus, primary producers and particulate organic carbon (POC) were examined to promote a better understanding of the trophic dynamics of food webs in Neotropical ecosystems. Spatial variability in carbon isotope composition in the species showed a decreasing gradient in the Upper Parana River system, from the Parana River and Itaipu Reservoir subsystems to the Baia and Ivinheima subsystems. Fish δ13C followed the isotopic trend of POC along the Parana River and Baia subsystem. Seasonal differences were not observed in fish. The analysis of percentile contribution of C3 and C4 sources in the species diet revealed the predominance of C3 plants (phytoplanktonic and periphytic algae and riparian vegetation) in most of the analysed subsystems and seasons. Nevertheless, the considerable participation of riparian vegetation was verified, especially in the Ivinheima subsystem in the dry season. C4 macrophytes presented a maximum contribution along the Upper Parana River. These results demonstrate the existence of specific variability for the consumer and their food sources in different environments of the same ecosystem.