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Environment | Water

Marine Toxins Stop Northwest Shellfish Harvesting

Mussels are indiscriminate feeders and are often the first indicators of contamination by toxic algae that cause Diarrhetic Shellfish Poisoning.

Mussels are indiscriminate feeders and are often the first indicators of contamination by toxic algae that cause Diarrhetic Shellfish Poisoning.

Ashley Ahearn

Diarrhetic Shellfish Poisoning is about as much fun as it sounds.

It doesn’t cause paralysis or death like some red tide algae do. But eating DSP-contaminated shellfish can cause vomiting, chills and other flu-like symptoms.

The closure of recreational shellfish harvesting is in effect for Quilcene, Dabob and Discovery bays.

Last year, three people got sick after eating infected mussels harvested near Sequim on the Olympic Peninsula. They were the first documented cases of DSP in the country. There were an estimated 60 cases in British Columbia last summer.

Now for the first time, three bays in Puget Sound have been closed to recreational shellfish harvest because of high levels of DSP toxins while health officials wait for more test results.

Dinophysis, the single-celled organism behind DSP, is a native of Puget Sound. Scientists have been seeing them for decades but they’re not exactly sure what’s making the organisms more toxic now.

“We have some of the largest numbers of dinophysis here in this area,” says Vera Trainer, an expert on harmful algal blooms with the National Oceanic and Atmospheric Administration’s Northwest Fisheries Science Center in Seattle. “They’re not all toxic. Sometimes we see high numbers and no toxins, sometimes we see low numbers and we do see toxins.”

View shellfish closures - Puget Sound in a larger map

Trainer added that dinophysis and other phytoplankton thrive in places like Puget Sound where large amounts of freshwater from rivers mixes with ocean water.

Cooking infected shellfish doesn’t get rid of this toxin so the state has an extensive monitoring system to prevent people from harvesting infected shellfish.

Washington’s Department of Health has purchased new equipment to test for DSP. They’ve been sampling for the toxin for over a year, but the sample analysis was done out of state. Oregon does not test for DSP.

“It gets us very concerned because in France there are outbreaks where hundreds of people that get sick with this so we definitely need to be monitoring for it,” says Frank Cox. He handles marine biotoxins for the Washington Department of Health.

There have been no reported cases of Diarrhetic Shellfish Poisoning in people in the Northwest this season.

Meanwhile, the Oregon Agriculture Department has closed recreational mussel harvesting on a large portion of the Oregon coast because of elevated levels of paralytic shellfish toxins.

View Mussel closure, Oregon in a larger map

The closure affects an area from Tillamook Head south to Heceta Head, about 13 miles north of Florence on the central coast.

The closure does not affect recreational clam harvesting on the Oregon coast. Also, crab are not affected by this level of toxin and are safe to eat.

All coastal areas north of Tillamook Head and south of Heceta Head remain open to all recreational shellfish harvesting.

Shellfish contaminated with the toxins can cause minor to severe illness or even death. Cooking will not destroy the toxins, which are produced by algae.

(The Associated Press contributed to this report.)