Deadly Toxin Discovered In Drake Bay Shellfish

MARIN COUNTY, CA – The Marin County Public Health Department has issued a warning to people harvesting mussels, clams and oysters in Drakes Bay because of potentially deadly levels of paralytic shellfish poison, a naturally occurring toxin.

On Tuesday, the California Department of Public Health notified public health staff in Marin about a recent mussel sample from the Chimney Rock sentinel station, within the Point Reyes National Seashore. That sample contained levels of paralytic shellfish poison at 37 times the "alert" level. That is the highest level detected in the county in two decades.

The finding prompted the state's health department to issue a warning for all of Marin County, including Drakes Bay. The National Park Service has been notified to post warning signs at locations along Drakes Bay within the Point Reyes National Seashore.

Paralytic shellfish poison is a marine toxin that causes illness through the consumption of contaminated shellfish. Changes in water conditions, including temperature, flow and salt content, can lead to surges in PSP. Cooking the shellfish does not alleviate the toxicity, county officials said.

"Some PSP is detected regularly in the bay and the ocean, but the latest samples are showing record levels near Chimney Rock and points north of Stinson Beach," Public Health Officer Dr. Matthew Willis said in a statement.

"Because these are potentially lethal levels, we want to make sure no one is out there collecting shellfish until it’s safe again," he said. "Please warn anybody who is out with boots and shovels looking for shellfish at low tide.”

The higher levels typically surface in the summer months, so the fact that they are occurring this early in the year is another sign of an increasingly unpredictable climate, county officials said.

There have been 542 reported illnesses and 39 deaths attributed to paralytic shellfish poison in California over the past 90 years, according to state statistics. Although the poison levels recorded this week are the highest levels detected in Marin in 20 years, Willis said no illnesses have been reported recently in the county.

The state warning does not apply to commercially-sold clams, mussels, scallops or oysters from approved sources. State law permits only state-certified commercial shellfish harvesters or dealers to sell those products. Shellfish sold by certified harvesters and dealers are subject to frequent mandatory testing to monitor for toxins.

Photo: The paralytic shellfish poison levels recorded this week are the highest levels detected in Marin in 20 years. Photo via County of Marin