Contemporary distribution of non-native Chinook salmon (Oncorhynchus tshawytscha) in South America

Chinook salmon represent one of the most successful salmonid introductions in South America, and today multiple naturalized populations exist across Patagonia. Here, we present an updated regional distribution of Chinook salmon that includes new records of occurrences collected between 2006 and 2022. We found a significant range expansion in terms of occurrences for adult (18 new basins; 2,854,108 km(2)) and adult spawners or juvenile (12 new basins; 53,262 km(2)) salmon extending both to the north and south of the previously known colonized range in South America. This range expansion (38% of the area considering only occurrences indicating reproduction via adult spawners or juvenile salmon) included major basins draining to both the Pacific Ocean and Atlantic Ocean coasts of the continent. Adult Chinook salmon are currently reported from 48 large basins (33.62 degrees-54.97 degrees S) covering a total drainage area of 3,047,197 km(2). The observed expansion we document here has been likely driven by the dispersal of straying adults from historically naturalized populations. Our findings provide evidence that the invasion of Chinook salmon in South America is ongoing and updated information relevant to the management of this invasive and socio-ecologically important fish.

Automated summary

Chinook salmon have successfully established naturalized populations in South America, particularly in Patagonia. This study presents updated information on the regional distribution of Chinook salmon, revealing a significant expansion of their range both to the north and south of the previously known colonized areas. This expansion includes major basins draining to both the Pacific and Atlantic coasts and highlights the ongoing invasion of Chinook salmon in South America.