PORTLAND, Maine (AP) — Officials have shut down virtually the entire Maine coast to clam digging because of a widespread outbreak of red tide.

Other than two small areas of mud flats in eastern Maine, the entire coast is closed to clam and mussel harvesting, said Darcie Couture of the Department of Marine Resources.

It’s the worst case of the toxic algae bloom Couture has ever seen, forcing hundreds of clam diggers to put down their rakes and driving up prices at retail stores and restaurants. It could be weeks before the flats reopen.

“We’ve never seen anything like this before,” Couture said.

Red tide is caused by naturally occurring algae that produce a toxin that shellfish absorb as they feed. Red tide taints clams and mussels, making them unsafe for people to eat, but poses no risk to people who eat fish, lobster, scallops and shrimp. Officials stress that clams and mussels on the market are safe, given the safeguards in place.

When toxicity levels get too high, officials close clam flats in those areas. This year, the toxin levels are high — as much as 50 times above the threshold — putting the state’s 1,600 licensed harvesters out of work.

As supplies go down, prices are going up. Clams were selling Friday at some Portland-area stores for $4.79 to $4.99 a pound, up from $2.99 to $3.99 a pound a couple of weeks ago.

Clam dealers have been paying more to diggers, as well. But that hasn’t done most diggers any good, said Chad Coffin, a longtime clam digger from Freeport.

“Prices have skyrocketed,” he said, “but there aren’t any clams to dig.”

Many clam dealers in Maine will turn to Canada and Massachusetts for their supplies, said Jim Markos, general manager of Maine Shellfish Co. Inc., based in Ellsworth and Kennebunk. Many restaurants and retailers will probably find themselves without any clams in the days ahead, he said.

And people with a hankering for steamers should “go out and get some tonight,” he said.

A Shaw’s supermarket in South Portland was out of clams on Friday. Bayley’s Lobster Pound in Scarborough was expecting to sell out of its remaining clams during the day.

“When that happens, I’ll just put ‘sold out’ on the board,” said owner Bill Bayley.

Clam diggers have faced off-and-on clam flat closures in recent weeks because of concerns about pollution from runoff due to the heavy rains that have fallen.

Nobody knows for sure why the red tide outbreak is so bad this year, but Couture suspects it’s somehow connected to the cool wet weather so far this summer.

“I can’t predict when it’s going to stop,” she said.

Only subscribers are eligible to post comments. Please subscribe or to participate in the conversation. Here’s why.

Use the form below to reset your password. When you've submitted your account email, we will send an email with a reset code.