China has closed its doors to all shellfish imports from an area that stretches from northern California to Alaska. The state of Washington says it's losing as much as $600,000 a week.

Among the shellfish not being harvested is the geoduck, a long-necked clam that can fetch up to $150 per pound in China. It's a major export for the Pacific Northwest.

The Chinese government instituted the ban earlier this month after finding two bad clams. One from Alaska had high levels of the biotoxin that causes paralytic shellfish poisoning. The other came from Washington's Puget Sound and tested high for inorganic arsenic. Officials in Washington state do not test for arsenic in shellfish.

Ninety percent of the geoduck harvested in Washington is sold to China and Hong Kong, and the ban's impact is being felt by members of the Suquamish Tribe near Seattle.

"As you can see, we dive right out here in this area," says Lydia Sigo as she stands on a dock on the tribe's reservation. "That's all just houses, and that's where we get the majority of our pounds is off this tract right here."

It's quiet on the water, with no boats anywhere to be seen. The tribe is losing $20,000 each day the ban is in place.

"That's been really frustrating because there's about 25 divers in our tribe, and that's 25 families that really need to pay their mortgage or pay their rent," Sigo says. "For me, I can't keep going on like this for very long."

To make matters worse, Sigo says, 40 percent of the money the tribal divers get from selling their geoducks goes to support tribal elders.

"So this is affecting the entire tribe, and other state divers, geoduck farms, people all over the state — it's a huge industry, and we all spend that money in our local economies," Sigo says.

The shellfish industry in Washington is worth $270 million annually, and China is the biggest market for exports. This is the broadest shellfish ban the Chinese have ever put in place. But it's not the first time China has banned a major import from the U.S.

Beef imports from the U.S. have been banned for the past 10 years over fears related to mad cow disease. More recently, China rejected about a half-million tons of U.S. corn because it was genetically modified.

Chinese officials have been slow to reveal details of their shellfish testing methods. That has prompted some to raise concerns about political motivations behind the shellfish ban.

"It is possible that it could be retaliation for something that has happened in the past," says Tabitha Mallory, a postdoctoral research fellow at the Princeton-Harvard China and the World Program.

In 2010 China banned salmon imports from Norway after the Nobel Peace Prize was awarded to Chinese political activist Liu Xiaobo.

Mallory says it's unclear what kind of larger political statement China could be making with the shellfish ban. "It's good to consider all the possible motivations for this, but I don't think that we should write off the possibility that it is a legitimate accusation."

The contaminated clam was harvested near the former site of a copper smelter in Tacoma, which had leached arsenic into the surrounding area. Washington state officials have closed the area and are testing shellfish for arsenic. Federal officials have sent a letter to China asking for the ban to be lifted.

All of this comes at a particularly bad time. Geoduck is a delicacy in China, with peak demand for the clam around Chinese New Year, which falls on Jan. 31.

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