Salmonid Introductions in Patagonia: A Mixed Blessing

Abstract

The fish communities of Argentine Patagonian basins are characterized by low species diversity. Their fish community structure and underlying intra- and interspecific dynamic relationships have been and are still poorly understood. Around 1904, 10 species from Northern Hemisphere hatcheries were introduced for sportfishing. Following the original introductions, unplanned stocking was widely practiced. Of all introduced species, Oncorhynchus mykiss, Salmo trutta, and Salvelinus fontinalis thrived; they colonized almost any available water body in Andean Patagonia. In addition, Salmo salar and Salvelinus namaycush established self-sustaining populations at a few locations. The various populations that inhabit different water bodies seem to have diverged and given rise to what are believed to be particular stocks. Some of these became world-class sportfisheries and attained importance as generators of economic improvement. Simultaneously, and although no detailed studies exist, it has been thought that salmonids have a tremendous negative impact on the native biota. Thus, in less than 100 years, salmonids have been perceived as trophy sportfish, ecological nemeses, and promoters of social well-being through sportfisheriesassociated economic development. In addition, the Chilean salmonid aquaculture boom led people to believe that this could be replicated in Argentine Patagonia and fostered the establishment of mostly O. mykiss caged-fish farming facilities. This raised concerns about a possible decrease in the quality of Argentine wild-salmonid (those salmonids that have successfully colonized and adapted to local waterways) sportfisheries due to negative effects associated with escapement of aquacultured fish. This scenario may be realized because escaped individuals of Salmo salar, O. gorbuscha, O. keta, O. kisutch, O. nerka, and O. tshawytscha, all introduced in Chile, may be finding their way into Argentine rivers that drain into the Pacific Ocean. These complexities have generated three interest groups: (1) people concerned with possible ecological damage upon the native biota, (2) promoters of sportfisheries as generators of economic revenue and development, and (3) promoters of salmonid aquaculture. Ironically, after almost 100 years, little is known about fish communities in Patagonia and the interactions that govern them. These communities may continue to change due to uncontrolled stocking, new arrivals of nonindigenous fishes from Chile, and escapes from aquaculture facilities. Salmonid introductions have thus become a mixed blessing- culprits of an ecological impact that may never be quantified or completely understood and promoters of economic development that would otherwise be impossible. The challenge for the future is to develop a consensus among Patagonian provinces regarding the leading policy for the introduced-salmonid resource and to establish the steps needed to generate information for its sound management.