Fishes (Osteichthyes: Actinopterygii) from the Pirapó River drainage, upper Paraná River basin, Paraná state, Brazil

In this study we conducted an ichthyofaunistic survey in the Pirapó River drainage, upper Paraná River basin, based on voucher specimens deposited in the Coleção Ictiológica do Nupélia/UEM. We reported a total of six orders, 23 families, and 76 species, in which four of them were classified as allochthonous and two as exotics. Twenty-eight percent of these species were recorded only for tributaries, whereas the commercially important migratory species, Dourado - Salminus brasiliensis (Cuvier, 1816), was recorded in the main channel, indicating that the Pirapó River, still free from impoundments, may be one of the last rivers in the upper Paraná River basin that can be used to protect migratory fish species

Is coexistence between non-native and native Erythrinidae species mediated by niche differentiation or environmental filtering? A case study in the upper Paraná River floodplain

ABSTRACT The limiting similarity theory predicts that divergence in the functional traits of native and introduced species is an essential component in species establishment, as introduced species must occupy a niche that is unoccupied by resident species. On the other hand, the environmental filtering hypothesis predicts convergence between introduced and native species, as both possess traits that make them adapted to the local abiotic environment. Morphology, spatial co-occurrence, diet, feeding selectivity, and niche breadth and overlap of Erythrinidae were evaluated to detect possible mechanisms acting in the coexistence between non-native and native species. Native (Hoplias sp. B and Hoplias cf. malabaricus) and non-native (Hoplerythrinus unitaeniatus and Hoplias mbigua) species presented differences in morphological traits, spatial co-occurrence, diet, selectivity, and niche breadth and overlap. The mechanisms mediating species coexistence seem to vary according to species. The absence of spatial and feeding overlap suggests that non-native species H. unitaeniatus occupy a different niche than native species, supporting its successful establishment without eliminating the native species. However, low feeding overlap and similar morphologies between non-native and native species of Hoplias point to environmental filters; in this case, the non-native H. mbigua is able to establish due to similarities in functional traits