The Conservation Implications of Introduced Trout and Beaver on Native Fish in the Cape Horn Biosphere Reserve, Chile

Abstract

Introduced species are a threat to native species conservation worldwide and can cause an overall reduction in biodiversity. In the Cape Horn Biosphere Reserve in southern Chile, introduced beaver and trout are highly successful invaders in the landscape and alter stream ecosystem function. Our research suggests introduced beaver create favorable feeding habitats for native puye (Galaxias maculatus) by increasing available macrobenthic biomass and creating ideal feeding conditions for puye. A negative effect of trout on puye was only detectable in favorable beaver-altered habitats where puye abundance was significantly reduced. A negative relationship between trout density and aquatic macrobenthic biomass suggests introduced trout reduce prey availability at the patch-scale. Our findings also show the presence of endangered Aplochiton spp. on Navarino and Hoste islands and the absence of brown trout completely from the southeast fringe of the Cape Horn Biosphere Reserve. Conservation measures be taken to prevent the spread of brown trout into the area in order to protect rare Aplochitons spp. These results emphasize the need for understanding introduced species distributions and their influence on native biota and stream ecology so conservation measures to preserve native species and the pristine status of the Cape Horn Biosphere Reserve can be implemented.