Farmed Pacific salmon invade Atlantic


A study published in a recent issue of the journal Conservation Biology has confirmed that introduced Pacific salmon are successfully invading the Atlantic.

The study by Leandro Becker, Miguel Pascual and Nstor Basso analyzed the mitochondrial DNA of Chinook salmon (Oncorhycnchus tshawytscha), a species native to the northern Pacific (from San Francisco Bay north to the Bering Strait, across the Chukchi Sea to Kamchatka, the Kuriles and Japan), that were caught out of a breeding population in the Santa Cruz River drainage, a river drainage in southern Argentina that drains into the southern Atlantic Ocean.

The authors found that the salmon in the Santa Cruz drainage were descended from fish that were imported from Puget Sound (in Washington) into southern Chile for salmon-ranching experiments in the 1980s (although there were four known unsuccessful attempts to establish Chinook salmon in southern Argentina and adjacent areas dating back to 1906).

The authors conclude that the Southern Pacific and Atlantic oceans provide...a favorable marine environment for the success of invading salmon. In particular, the water belt around the tip of South America associated with fjords; southern channels, including the Magellan Strait with its direct inflow of diluted waters toward the Atlantic Ocean; and the inshore portion of the Patagonian shelf on the Atlantic, appear to provide a rather bounded waterway for exotic anadromous salmonids, rich in diverse forage species.

These characteristics may explain, at least in part, the success of different anadromous species in Southern Atlantic rivers. It also points to the southern Patagonian Shelf as a prime foraging arena for anadromous salmon from spawning populations in both the southern Atlantic and Pacific Oceans.

The effects of the salmon on native wildlife in the region remain unknown, although the authors raise the possibility that they might adversely affect the populations of the fish species they prey on.

For more information, see the paper: Becker, LA, MA Pascual and NG Basso (2007) Colonization of the southern Patagonia Ocean by exotic chinook salmon. Conservation Biology 21, pp. 1347"1352.