Wild-caught mussels in California can’t be eaten for 5 months. Here’s why

Harvesting mussels to eat was prohibited starting Sunday through October due to potentially dangerous levels of biotoxins, according to a state order.

An annual quarantine for sports-harvested mussels protects against the high-risk period of paralytic shellfish poisoning (PSP) and domoic acid poisoning, also known as Amnesic Shellfish Poisoning, according to the California Department of Public Health.

The San Luis Obispo Public Health Department said mussels that are commercially grown by certified companies are exempt from this order.

Certified companies are required to submit shellfish samples to the CDPH for toxin testing. The department’s website says that commercial shellfish are produced in hatcheries with defined leases, so it’s easier to track their toxin levels.

Typically around this time of year, phytoplankton, or algae, bloom, increasing the likelihood of toxin-producing phytoplankton. When mussels and other shellfish eat the algae, they take some of those toxins with them.

Other shellfish may be prohibited on a case-by-case basis, officials say, but wild-caught mussels contain an especially high concentration of the toxins, making them high-risk.

Biotoxins don’t harm shellfish, but it can be anywhere from days to months before the toxin is flushed from their system and they’re safe to eat again.

An updated view of California’s toxic phytoplankton can be found on a state Health Department map.

These biotoxins can be found in mussels across California’s coast, including all bays, inlets and harbors.

The quarantine will be in place through Oct. 31. The state’s website says the May-through-October period has encompassed more than 99% of all shellfish poisonings and deaths reported in California since 1927.

CDPH reported that since 1903, there have been 543 illnesses and 39 deaths attributed to PSP in the state. The department says there are no known antidotes to the toxins found in mussels, and the toxicity can’t be destroyed just by cooking.

The state warns that death can occur within 30 minutes of eating toxic shellfish.

“You should never assume that sport-harvested mussels are safe to eat when the annual quarantine is not in effect,” CDPH wrote on its website.

CDPH monitors shellfish for toxins year-round. With help from local agencies and citizen volunteers who collect shellfish and plankton samples, California State Public Health Laboratory scientists analyze the samples to monitor levels throughout the year.

For more information, visit https://bit.ly/3OTJzDa.

This story was originally published May 2, 2022 at 5:00 AM with the headline "Wild-caught mussels in California can’t be eaten for 5 months. Here’s why."