CAMBIOS EN DIVERSIDAD Y DISTRIBUCIÓN DE PECES NATIVOS CON LA PRESENCIA DE DOS ESPECIES INVASORAS EN EL RÍO ATACAMES, NOROCCIDENTE DEL ECUADOR

The interpretation of biological diversity can be very complex, as it exists a dynamic based on the origin and diversification of species, in addition to anthropogenic effects, such as the introduction of invasive species, which can result in the local extinction of the native ones. The aim of this study was to analyze the temporal variation (2012 and 2017),  in composition and distribution of the ichthyofauna along the Atacames River in northwestern Ecuador. In 2012 we recorded: 1) the presence of  Astyanax ruberrimus , which was reported locally extinct by 2017; and 2) the tilapia ( Orechromis niloticus ) as the only introduced fish species present until 2017, when the addition of the non-native guppy ( Poecilia gillii ) occurred . In addition, the increase in human activities conduced to change in diversity, abundance and distribution of fish along the watercourse, which resulted in dispersing of some species towards the upper reaches of the river basin.