Escaped farmed salmon and trout in Chile: incidence, impacts, and the need for an ecosystem view

The exponential growth of the salmonid farming industry during the last 3 decades has created conditions for massive escapes of these exotic species into natural environments in southern Chile. Here, we review and update information about salmonid escapes from 1993 to 2012 and examine their potential environmental, social, and economic consequences. We estimate that more than 1 million salmonids escape each year from marine farms, mainly due to weather conditions and technical and operational failures of net-pens. While a decrease in the magnitude of escaped Atlantic and coho salmon has occurred during the last several years, escaped rainbow trout have not followed the same pattern. Rainbow trout have become a greater threat to native ecosystems due to their greater potential to establish self-sustaining naturalized populations. The main ecological effects of escapees are related to short-term predatory effects upon native fish, long-term effects linked to the likelihood of farmed salmon establishing self-sustainable populations, and disease and pathogen transfer to native fauna. More research is needed to identify and develop reliable indicators to estimate the impact of escapees at the ecosystem level in both marine and freshwater systems. An understanding of the mechanisms of coexistence between native fishes and introduced non-native salmonids may be useful to design effective management strategies aimed at protecting native fish from salmonid introductions. A precautionary approach that encourages local artisanal and recreational fisheries to counteract colonization and naturalization of salmon species in southern Chile may constitute another management option.