Salmon Farming May Doom Wild Populations, Study Says

The paper's findings have implications beyond the Broughton Archipelago, where juvenile salmon have to swim past a nearly 50-mile string of fish farms before they reach the open ocean.

With lucrative fish farming now widespread in Atlantic Canada and along the coast of Maine, northern Europe and Chile, the industry has become increasingly controversial. Sea lice is the problem off British Columbia and in some areas of northern Europe, but a dispute over infectious salmon anemia is the central issue off the Maine and Canadian Atlantic coast. The escape of penned salmon is a key problem in Chile, where salmon are an aggressive, invasive species.

As the world's population expands, authorities in the United States and abroad have promoted aquaculture as a way to sustain current levels of fish consumption. Last month, the U.N. Food and Agriculture Organization issued a statement suggesting the global seafood supply will have to increase by 37 million metric tons to satisfy demand, and much of the seafood will have to be farmed.

Sea lice are naturally occurring parasites that attach themselves to wild salmon in the open ocean and feed on skin and muscle tissue. They thrive in open-net salmon farms because the fish are crowded together. Adult salmon living far offshore can cope with the lice, but wild juveniles heading to sea are vulnerable because they are small and thin-skinned.

Daniel Pauly, who directs the University of British Columbia's fisheries center but was not involved in the study, said in an interview that he went into the archipelago a few years ago and collected 20 to 30 juvenile pink salmon, all of which were infected.

"It was like 'Alien,' " he recalled, referring to the movie in which an alien life form invades its victims' bodies before killing them. "They were destined to die."

Critics of current aquaculture practices in coastal areas generally propose two possible remedies: Building enclosed holding tanks that would contain diseases, parasites and escaping fish; and placing open-net farms much farther out to sea. Both alternatives are being studied, but officials say they would increase costs.