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Toxic algae closes Samish Bay shellfish harvest

September 28, 2018

All recreational shellfish harvesting and all commercial oyster harvesting were closed Tuesday in Samish Bay after a biotoxin was found in regularly obtained samples.

A biotoxin that can cause paralytic shellfish poisoning was found in one oyster from the bay in high enough concentrations to make consumers sick, the state Department of Health’s marine biotoxin lead Jerry Borchert said.

The state agency monitors year-round for several biotoxins, which are produced by algae in the water, including that which can cause paralytic shellfish poisoning.

Samples are collected every two weeks as a precaution, and if a biotoxin is present, the frequency of sampling increases.

“Whenever we see toxins come in at all we ramp up and start getting more samples coming in,” Borchert said.

Paralytic shellfish poisoning can cause symptoms within minutes and last as long as two days after contaminated shellfish is consumed, according to the Department of Health.

It affects the central nervous system and paralyzes muscles, which can cause an upset stomach, dizziness, numbness and difficulty breathing, and in some cases may be fatal.

Because trace amounts of the biotoxin that causes paralytic shellfish poisoning were seen in shellfish from Samish Bay on Sept. 18, weekly sampling was initiated, Borchert said.

With the discovery Tuesday of higher concentrations, additional sampling is being done to determine if only certain parts of the bay are affected and if the harvest closures could be limited to those areas.

Borchert said the toxic algae that produces the biotoxin may be coming into Samish Bay from Bellingham Bay, where higher concentrations of the biotoxin are being found.

There, the toxin has reached alarming levels of more than 1,000 micrograms per 100 grams of shellfish — a level that can be deadly if the shellfish is consumed, he said.

While the levels found in Samish Bay are lower — the highest being 245 micrograms in a Pacific oyster — it’s still enough to make consumers sick and exceeds the internationally accepted precautionary threshold of 80 micrograms, Borchert said.

“It is definitely unsafe. ... We take it very seriously,” he said.

The biotoxins that cause paralytic shellfish poisoning last closed shellfish harvesting in Samish Bay in July 2010, according to the Department of Health.

“It has been a while since we’ve seen elevated levels of PSP in Samish Bay,” Borchert said. “We don’t know why these things happen when they do. That’s why we do testing all year.”

Skagit County Public Health urges those with symptoms of paralytic shellfish poisoning after eating mussels, oysters or clams to immediately go to an emergency room or call 911.

For more information about shellfish harvest closures, call the Marine Biotoxin Hotline at 1-800-562-5632 or visit fortress.wa.gov/doh/eh/maps/biotoxin.

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