For conservationists who have long advocated measures to protect the fish, the government's announcement Wednesday was a welcome relief.
"It's a real light in the darkness to have this happening," said Casson Trennor, conservationist and author of "Sustainable Sushi." "With Obama on the side of the fish, I think we have a really good shot."
The Obama administration's support will dramatically shift the balance of power at next week's meeting in Doha, Qatar, where representatives of 175 nations will decide whether to protect the Atlantic bluefin population under the United Nations Convention of International Trade of Endangered Species.
The European Union is divided on the measure, proposed by Monaco, and Japan has firmly decided not to support it, saying that the fish should instead be regulated by the International Commission for the Conservation of Atlantic Tunas.
The United States has supported the commission but has said more drastic action is needed.
"We recognize that the parties to ICCAT took some unprecedented steps," said Tom Strickland, assistant Interior secretary for fish and wildlife and parks. "However, in light of the serious compliance problems that have plagued the eastern Atlantic and Mediterranean fishery and the fact that the 2010 quota level adopted by ICCAT is not as low as we believe is needed, the United States continues to have serious concerns about the long-term viability of either the fish or the fishery."
The overfishing of bluefin tuna is a recent phenomenon. It was once considered a trash catch among commercial fisherman, selling for about a nickel a pound to cat- and dog-food manufacturers.
In Japan, all tuna was once considered inferior fish. But as Japanese tastes and the international economy changed in the decades after World War II, bluefin became more popular. After sushi became popular in the United States, commercial demand increased exponentially.
Studies show that since 1980, the Atlantic bluefin population declined more than 80 percent.
Japan, the consumer of 80 percent the world's bluefin, has announced that if a ban is accepted, it will exercise its right not to comply. If the nations supplying Japan with fish comply, however, then the measure would still put a sizable dent in Japan's seafood supply.

