Ocean-swapping Pacific salmon are moving into Atlantic waters, scientists say.
The fish, native to the North Pacific, have started colonizing and breeding in rivers in southern Argentina, a new study shows (see map).
Although the sight of salmon leaping in Argentina's world-renowned trout rivers may be enticing to anglers, the silvery predators could become a nightmare for the region's marine life.
The invaders threaten to deprive penguins and sea mammals of food—an ever-increasing risk given the number of invasive salmon currently escaping from fish farms in neighboring Chile, researchers say.
The warning stems from the first study to show salmon swimming from the Pacific to the South Atlantic, where salmon don't naturally occur.
The study focused on chinook salmon, a Pacific species that has recently become established in the Santa Cruz River system in the Patagonia region of Argentina.
DNA analysis of the Santa Cruz salmon traced the fish back to failed salmon-ranching experiments on Chile's Pacific Coast during the 1980s.
Don Staniford, who was not involved in the new study, is the European representative for the Washington, D.C.-based environmental group Pure Salmon Campaign. He said the new findings could mean dire consequences for the region's marine habitat.
"Salmon have a very healthy appetite, so they're going to consume native fish and prey that other species are dependent on," he said.
"You've got a recipe for potential ecological disaster."
Threat to Penguins
Chinook salmon were first discovered accidentally in the headwaters of the Santa Cruz in 1998 as researchers surveyed trout spawning sites.
Another breeding population has recently been identified in a river in Tierra del Fuego, at the southern tip of Argentina.
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