Beware of eating shellfish caught by friends and relatives and friends of relatives this holiday weekend.

California health officials issued a warning Wednesday about all sport-fished bivalves — including mussels, clams, and scallops — found in waters off the coasts of San Francisco, San Mateo, Santa Cruz, and Monterey counties. The shellfish have recently been found to contain dangerous levels of a toxin known to cause paralytic shellfish poisoning (PSP), and one the can not be destroyed by cooking. And this is not a poisoning that anyone wants.

Per the California Department of Public Health:

PSP toxins affect the central nervous system, producing a tingling around the mouth and fingertips within a few minutes to a few hours after eating toxic shellfish. These symptoms are typically followed by loss of balance, lack of muscular coordination, slurred speech and difficulty swallowing. In severe poisonings, complete muscular paralysis and death from asphyxiation can occur.

The warning doesn't apply to commercially harvested bivalves, or to shellfish from approved states outside of California.

As the department says, "Shellfish sold by certified harvesters and dealers are subject to frequent mandatory testing to monitor for toxins."

This PSP toxin is different from domoic acid, which has been found in local Dungeness crabs in recent years due to toxic algae blooms in the Northern Pacific. Such blooms have delayed and/or ruined the Dungeness crab season more than once.

You can check the department's Marine Biotoxin Monitoring page for more updates.