Jefferson County Health Department officials closed Port Ludlow Bay, Mats Mats Bay and Discovery Bay last week for the recreational harvest of shellfish, after water samples showed high levels of the biotoxin that causes Paralytic Shellfish Poisoning (PSP), which can be fatal.

County public health staff posted warning signs at public access points at all bays.

The closure applies to all species of molluscan shellfish including, clams, oysters, mussels and scallops.

Crab and shrimp are not included in the closure. However, crab that have fed on shellfish can also become toxic. Even if the crab meat is safe, toxins can accumulate in crab guts and “butter” — the white-yellow fat inside the back of the shell. Crabbers are encouraged to clean crab thoroughly and avoid eating the crab butter and guts.

Health officials warn the biotoxin is not destroyed by cooking or freezing.

People can become ill from eating shellfish contaminated with Paralytic Shellfish Poison. This biotoxin affects the nervous system and paralyzes muscles, thus the term “paralytic” shellfish poison.

Symptoms of PSP can appear within minutes or hours and usually begin with tingling lips and tongue, moving to the hands and feet, followed by difficulty breathing and paralysis. Anyone experiencing any of these symptoms after consuming shellfish should contact a health care provider immediately. For extreme reactions, call 911.

Paralytic Shellfish Poison is a naturally occurring marine biotoxin that is produced by some species of microscopic algae. Shellfish are filter feeders. They pump water through their systems, filtering out and eating algae and other food particles. When shellfish eat the biotoxin producing the algae, however, the biotoxin can accumulate in their tissue.

It’s normal for biotoxin-producing algae to be present in marine water. They are usually in low numbers that cause no problems. But when the algae “blooms,” the number 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 before the shellfish are safe to eat again.

Health officials caution that the appearance of the water does not indicate the presence of a toxic algae bloom. In fact, waters contaminated with Paralytic Shellfish Poison are rarely tinged red or other colors. Paralytic Shellfish Poison can be present in large amounts even if the water looks clear. Shellfish containing toxic levels of Paralytic Shellfish Poison don’t look or taste any different from shellfish that are safe to eat. Laboratory testing of shellfish meat is the only way to detect Paralytic Shellfish Poison.

To learn where it’s safe to harvest shellfish, and for harvesting seasons and rules, go to www.doh.wa.gov/ShellfishSafety.htm. You can also call the Biotoxin Hotline at 1-800-562-5632. For the latest information on regulations and seasons, visit wdfw.wa.gov/

places-to-go/shellfish-beaches or call the WDFW Fish Program’s customer service at 360-902-2700.