CHAPTER 18 INTRODUCED ANADROMOUS SALMONIDS IN PATAGONIA: RISKS, USES, AND A CONSERVATION PARADOX MIGUEL A. PASCUAL, PH.D. AND JAVIER E. CIANCIO, PH.C. Centro Nacional Patago ´nico—CONICET, Blvd. Brown 2825, (9120) Puerto Madryn, Chubut, Argentina (E-mail: pascual@cenpat.edu.ar) Abstract: Because of their peculiar life cycle, introduced anadromous salmonids can have cascading effects on both marine and freshwater communities. From an ecological standpoint, there are three aspects of exotic salmonids that merit special attention: the factors that govern the establishment of wild populations, the impact of the introduced fish on the receiving communities, and their adaptations to the new environments. Here, we examine several case studies dealing with anadromous sal- monids introduced in Patagonia, the southern region of Argentina, from these three viewpoints. Key words: alien species, aquaculture, environment, exotic species, Patagonia, salmonids, stock enhancement, sport fishing, trout 1. INTRODUCTION Patagonia, the southernmost region of Argentina and Chile (Figure 1), has today firmly established populations of trout, red deer, and wild roses, among many other exotic species. While many early introductions were driven by aesthetic or recreational reasons, a new wave of exotic imports is arriving into Patagonia. This time the driving force is development and economic progress—the introduction of exotic species for hatcheries and animal farms. These new activities differ in several ways from the import of species by European immigrants, who took a favorite plant or animal when they immi- grated to South America. The new introductions include freshwater, marine, and terrestrial species. New hatcheries and farms are commercial enterprises Bert: Ecological and Genetic Implications ch18 Revise Proof page 333 16.5.2007 6:51pm Compositor Name: PDjeapradaban 333 Theresa M. Bert (ed.), Ecological and Genetic Implications of Aquaculture Activities, 333–353. ß 2007 Springer.