Biological invasion at an early stage? First record of the banjo catfish Pseudobunocephalus iheringii (Siluriformes: Aspredinidae) in the Tramandaí river basin, Brazil and the potential invasion pathway to this system

Biological invasion by species that are not naturally present in a native assemblage (nonnative species) is a multi-stage process (Blackburn et al., 2011). However, perception of an invasive process is difficult in early stages of the process, when abundance is very low and distribution is very limited. The presence of nonnative fish species has been reported in the Tramandai river basin, but their introduction pathway in the Tramandai river basin is unknown. The aim of this paper is to report the occurrence of Pseudobunocephalus iheringii in an artificial channel in the watershed divide between the Laguna dos Patos basin and the Tramandai river basin, in southern Brazil. This report represents the first record of an additional nonnative species in the Tramandai basin, documents the early stage of a potential invasion process in this system, and represents the first evidence for the role of artificial water channels as invasion pathways for nonnative fish species into the Tramandai basin, affecting two aquatic ecoregions.