“It is simply not possible to produce fish on an industrial scale in a sustainable way,” said Wolfram Heise, director of the marine conservation program at the Pumalin Project, a private conservation initiative in Chile. “You will never get it into ecological balance.”

Researchers in Chile say the problems of salmon farming go well beyond the latest virus. Their concerns mirror those of the Organization for Economic Cooperation and Development in Paris, which heavily criticized Chile’s farm-fishing industry in a 2005 report.

Meanwhile, neighboring fishermen who have been affected by the fish-farming industry can only hope for better days. Mr. Guttierrez, 33, said that just six years ago he and his fishing partner would haul in 1,100 pounds of robalo on a typical day. On a recent day he pointed to that morning’s catch of only 88 pounds in a cooler in the bed of a pickup truck.

He lamented the changes he had observed in the fish: they are rosier than before, and their skin is flabbier. He said he suspected that the wild fish were eating the same food pellets that the salmon were being fed, which he said were falling to the sea floor.