Non-native anadromous salmonids in the La Plata Basin: Long distance colonization?

Abstract

The introduction and dispersal of salmonids have been widespread in Patagonian basins,including anadromous species such as Chinook salmon (Oncorhynchus tshawytscha),rainbow trout or steelhead (O. mykiss), sea-run brown trout (Salmo trutta), and, to alesser extent, coho salmon (Oncorhynchus kisutch). In recent years, Chinook salmonand steelhead have been reported in the Paraná and Uruguay rivers and in the estuary ofLa Plata River. This could be a result of long-distance movements, where strayindividuals travel northward along the cold Malvinas current. They enter these riverswhen it collides with the warm current originating from Brazil. However, this entrytakes place within a specific timeframe when the water temperature remains belowits lethal thermal threshold. Due to this temperature constraint and their reproductivecharacteristics, the introduction of salmonids into this basin would not present a risk tothe native species. The projected impact of climate change, which anticipates anincrease in river temperatures and a southward shift of the Brazilian current, wouldfurther support this hypothesis.