Food web structure and robustness of fish assemblages in the Uberabinha River, Upper Paraná Basin

Aim We modeled and analyzed the topological structure of the fish food web of the Uberabinha River (Upper Paraná Basin) to characterize its connectance, trophic levels, modularity, and robustness. Methods The network was constructed from a meta-web of 36 fish species and seven basal resource categories, based on diet data from FishBase and peer-reviewed literature. Analyses were performed on a directed binary network using standard ecological network metrics and simulations of random and targeted species extinction. Results The food web showed low connectance (C=0.114), compressed trophic levels (range: 2.0–2.88), and weak modularity (Q=0.113), indicating limited functional compartmentalization. Robustness simulations revealed high tolerance to random species loss (R50=12) but sharp vulnerability to targeted removal of highly connected species (R50=6). Conclusions Network stability appears to be sustained primarily by generalist redundancy while remaining critically dependent on a small set of hub species and top predators, reflecting the functional simplification typical of impacted Neotropical river ecosystems. Conservation strategies should prioritize the maintenance of key trophic interactions over species richness alone.