There is significant concern related to the effect of introduced species in an ecosystem. Salmonids were introduced in Chile at the early 1900’s into rivers and lakes for recreational proposes, but it was not until 1970’s that salmon farms start to do business at the Southern regions of the Chilean coast. There is scarce information about the impacts of the presence of this escaped/introduced species on the native fish population. Chilean fishes are unique due the geographic isolation of the territory. Freshwater fish species are 44 species, with 40% of these species classified as endangered. The present proposal aims to study the effects of salmonids cohabiting with endemic fishes from Patagonia.