Deadly mussels in Humboldt County

Paralytic shellfish poisoning causes a quarantine of locally harvested mussels

By Alexandria Hasenstab

Eating only four locally harvested mussels in Humboldt County could be fatal. On Feb. 14, the Yurok Tribe’s Facebook page released a warning about consuming mussels that read, “Important Mussel Update. Do not eat mussels right now. Please help get the word out.”

The message also said that mussels from Wilson Creek Beach were sampled by the Yurok Tribe Environmental Program on Feb. 7. Mussels from this area had detections on paralytic shellfish poisoning.

Native American Studies assistant professor Kayla Begay said that mussels are not only an important food source, they are also a big part of the Yurok Tribe’s culture. According to Begay, eating and gathering mussels is a way to keep tradition alive.

“It’s an important part of the culture to know how to do these things and to still do them,” Begay said.

Begay said that the mussels the Yurok Tribe gather are different than commercial mussels that are sold in stores. Although restaurants and grocery stores can still safely sell mussels, locally harvested ones must be carefully watched.

“It’s something that the tribe monitors for the safety of the people,” Begay said.

This isn’t the first that paralytic shellfish poisoning has been found in mussels and it won’t be the last. According to Pete Kalvass, the senior marine biologist for the California Department of Fish & Wildlife and an HSU alumni, the phenomenon happens annually. Kalvass said that paralytic shellfish poisoning in mussels is caused by a group of algae they eat called diatoms. This algae is always present in the water but increases in warmer temperatures.

“This tends to be a seasonal thing,” Kalvass said. “Its unusual to see it this time of year. We always used to say the months with the letter R in them are safe.”

Contrary to usual patterns, February’s waters were not safe from high levels of diatoms. Kalvass believes this is due to increases in oceanic temperatures over recent years.

The diatoms that cause paralytic shellfish poisoning are consumed by mussels through filtration. The diatoms produce a biotoxin that is harmless to mussels, but with enough accumulation in the human body it can cause serious problems.

“This biotoxin affects the central nervous system,” Kalvass said. “You lose muscle control and that would essentially mean death by asphyxiation. That would be in a very rare and severe case.”

According to Kalvass, less severe symptoms of paralytic shellfish poisoning include tingling around the mouth and fingertips.

The California Department of Public Health and the Yurok Tribe Environmental Program test local mussels once a month. Both of their websites post updates on the safety status of local seafood. Kalvass is unsure whether next month’s oceanic concentration of diatoms will allow for safe local mussel consumption.

“It’s possible they’ll all be fine next month, but since we’re coming into the normal quarantine season they probably won’t be safe to eat until fall,” Klavass said.