Differential Invasion Success of Atlantic and Pacific Salmon in Southern Chile: Patterns and Hypotheses

Biological invasions represent one of the greatest threats to aquatic ecosystems, particularly in locations a high degree of isolation and endemism, such as southern South America. In this region, salmonids are top-level invaders, but information about their dispersal, persistence, and population dynamics is still limited. Here, we used available historical information from field surveys conducted in lakes and streams of Southern Chile to evaluate patterns of establishment of both Atlantic and Pacific salmon. Atlantic and coho salmon show little evidence of establishing self-sustaining populations and thus may be considered less successful, whereas Chinook salmon is rapidly expanding its distribution. We develop a series of hypotheses about key factors that may account for differential success among these three species, including human, environmental, and invader characteristics.  More specifically, these factors relate to propagule pressure, biotic and environmental resistance, and invader plasticity.  In the context of these hypotheses and existing information, we provide a series of recommendations for future study to better understand the differential success of salmon invasions in southern Chile.