Invasive fishes in a high value conservation area, the Valcheta stream (Río Negro, Argentina): Invasion status and preliminary management strategies.

QUIROGA SOFÍA; VELASCO, MELINA ALICIA; POVEDANO, HERNÁN; KACOLIRIS, FEDERICO PABLO

Ciudad Autónoma de Buenos Aires

Congreso; Marine and Freshwater Invasive Species: Ecology, Impact, and management; 2016

Aquatic Invasive Species organized by the AEHMS

The Valcheta stream is an endorheic basin which originates in several thermal springs located within the Natural Protected Area Somuncurá Plateau, Río Negro province, Argentina. The isolation of this stream and its thermal condition have led to the evolution of several endemic species, including two vertebrates, the Naked-characin (Gymnocharacinus bergii) and the Valcheta frog (Pleurodema somuncurense), categorized on the IUCN Red List as Endangered and Critically Endangered respectively. One of the most important threats that face these species is the presence of two exotic predatory salmonids (Oncorhynchus mykiss and Salvelinus fontinalis) that were introduced in the lower basin of the Valcheta stream in 1941. Moreover, the invasive Silver bream, Cheirodon interruptus, was recently discovered in the stream and is probably competing for food with the Naked-characin. The main goal of this work is to present new and updated information related to the distribution range of these exotic fish species in the headwaters of the Valcheta stream. Since 2012, we are working on the area to develop research and conservation activities. We conducted different types of sampling (diving transects; visual transects on the shore next to the stream, and also several types of fishnets). As a result, we updated the distribution range for both, exotic and endemic aquatic vertebrates of the Valcheta stream. We also documented the first case of predation of Naked-characin by trout. Our results have shown the current situation is concerning. Exotic fishes are thriving at the stream, showing an increase in its ranges, probably in coincidence with a confirmed decline of the Naked-characin and the Valcheta Frog. We discussed the relevance of our results in the frame of the conservation status of the Naked-characin and the Valcheta frog. In this context we are starting management actions in order to reduce the number of invasive species.