Feeding trends of Psalidodon paranae in an impacted Neotropical basin: a multifactor and integrative approach

Psalidodon paranae is an endemic small Characidae from the Upper Paraná River ecoregion (Neotropical region, Brazil), where many watercourses are affected by anthropic activities. The Verde River ( VR ) was chosen as a model to study the feeding trends of P. paranae. Based on empirical observations, hypotheses were set concerning its occurrence, the environmental representativeness of its diet and the multifactors modulating ontogenetic, spatial, and temporal diet variations. To evaluate these hypotheses for the first time, an integrative approach was applied (modelling and multivariate techniques). Standardized samplings were performed monthly during one year at four sites. Influence of environmental variables on fish distribution was evaluated by means a general linear model. Stomach content analysis of P. paranae allowed the calculation of gravimetric frequency of consumed food categories. Ontogenetic, spatial, and temporal differences on diet were evaluated by means a permutational multivariate analysis of variance, and the influence of environmental variables on them with a canonical correspondence analysis. From the total of 301 specimens caught (4.6–13.4 cm total length range), 216 individuals of P. paranae presented stomach with contents. The species consumed 32 different food categories in VR , highlighting aquatic and terrestrial angiosperms, and beetles. The methods applied identified significative spatial and temporal differences in P. paranae diet as result of multifactors (palaeogeomorphology, abiotic, biotic, and anthropic) operating in the VR . Heterogeneity and complexity of VR and P. paranae occurrence and feeding trends evidenced that the opportunistic and generalist behavior lead to intrinsic patterns of each fish population at each watercourse.