Shellfish harvesting halted for toxicity

By James Robinson
Posted 6/19/24



Mystery Bay remains closed to all shellfish harvesting after recent shellfish samples showed high levels of the biotoxin that causes Diarrhetic Shellfish Poisoning.

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Shellfish harvesting halted for toxicity




Mystery Bay remains closed to all shellfish harvesting after recent shellfish samples showed high levels of the biotoxin that causes Diarrhetic Shellfish Poisoning.

Jefferson County Public Health and Washington State Parks officials have posted warning signs at public access points, since county health officials first announced the closure on June 13. The closure remained at the top of the state department of health’s Marine Biotoxin Bulletins on June 17.

A county health department news release said the closure does not affect Kilisut Harbor.

According to health officials and wildlife managers, “all species” means clams (including geoduck), oysters, mussels and other invertebrates such as the moon snail. All areas are closed for the sport harvest of scallops. The closure does not apply to shrimp or seaweed. Crab are not included in closures unless specifically listed. Biotoxins and other contaminants are known to concentrate in crab guts (butter). To be safe, health officials recommend cleaning crab thoroughly and discarding the guts.

In addition to Mystery Bay, the following Jefferson County areas are also closed to some shellfish harvesting.

Discovery Bay, and the Quimper Peninsula to Point Hudson, is closed to harvesting butter clams and varnish clams.

Admiralty Inlet south to Port Ludlow, including Oak Bay and Mats Mats Bay, are also closed to the harvesting of butter clams and varnish clams.

Diarrhetic Shellfish Poison toxin is non-lethal to humans, according to health officials.

Diarrhetic Shellfish Poisoning toxin is not destroyed by cooking or freezing. It causes nausea, vomiting, abdominal pain, and diarrhea, with diarrhea the most commonly reported symptom. If symptoms are mild, call your health care provider and your local public health agency. If symptoms are severe, call 911 or have someone take you to your family doctor.

Diarrhetic Shellfish Poison is a marine biotoxin toxin produced by a naturally occurring microscopic algae. Shellfish are filter feeders. They pump water through their systems, filtering out and eating algae and other food particles. When shellfish eat biotoxin producing algae, the biotoxin can accumulate in their tissue. People can become ill from eating shellfish contaminated with Diarrhetic Shellfish Poison.

It's normal for biotoxin-producing algae to be present in marine water. They are usually in low numbers that cause no problems. However, when the algae "blooms," the amount of biotoxin-producing algae can increase. The increased algae becomes a greater food source for shellfish. The more algae the shellfish eat, the more biotoxin they accumulate. Biotoxins don't harm shellfish, so the level in their tissue will rise until the bloom subsides.

When the number of toxin producing algal cells returns to normal low levels, the shellfish eventually flush the toxin from their bodies. It can take several days to several months or longer before shellfish are safe to eat again.

The algae that produces Diarrhetic Shellfish Poison toxin has been detected in Washington's marine waters for some time, but has not produced toxin at unsafe levels until recently. In June 2011, three people became ill after eating recreationally harvested mussels from Sequim Bay. Testing confirmed the shellfish were contaminated with the Diarrhetic Shellfish Poison toxin.

Shellfish containing toxic levels of Diarrhetic Shellfish Poison don't look or taste any different from shellfish that are safe to eat. Laboratory testing of shellfish meat is the only known method of detecting Diarrhetic Shellfish Poison.

Before harvesting shellfish, health officials recommend checking the state’s “Shellfish Safety Map” for beach closures on the day you plan to harvest. State officials regularly test shellfish for biotoxins and close areas when unsafe levels are detected. Beaches are sometimes posted with warning signs. Don't assume a beach is safe if there are no signs – beach closure signs sometimes disappear.

Shellfish harvested commercially and sold to the public come from licensed, certified growers. Commercial harvest operations must meet stringent state and federal health standards, and the shellfish they harvest are regularly tested for biotoxins

To find out which areas in Washington are safe to harvest shellfish, please check the Shellfish Safety map at or call the Biotoxin Hotline at 1-800-562-5632. You can view the Marine Biotoxin Bulletin on the Washington State Department of Health website. Go to the “Marine Biotoxins” page and click on the link for the “List of Biotoxin Closures by County.”