Fish Distribution in a Deep, Glacially Originated, Ultraoligitrophic Lake of Patagonia-Argentina

Nahuel Huapi Lake with its 554 km², 150 m average and 454 m maximum depths is the largest waterbody of northern Patagonia, Argentina and center of the homonymous National Park. Its fish community composed by 5 native and three introduced salmonid species has been scarcely studied and managed up to the present. Effective management of natural resources is contingent on simplifying the multidimensional information that influences the distribution and dynamics of organisms in ecosystems. The goal of our ongoing study is to explore patterns and causes of fish distribution through standard analysis and Geographic Information Systems. Fish community composition and distribution were determined from gill net catches from multiple sites during three years. Relevant physico-chemical parameters were collected seasonally throughout the lake. Analysis showed that even though specimens off all species are widely distributed in the lake, differential distribution patterns can be found. These species specific patterns are both spatial (vertical and horizontal) and seasonal, and can be explained by species specific and lake habitat characteristics. The present study shows that fish resource management authorities should consider the described differential distributions to maximize outcomes in relation to the National Park conservation objectives.