You may have heard about the commercial California Dungeness crab season getting a very late start this year due to domoic acid levels that took fresh crab off the menu. Another poison that you may not have heard about is paralytic shellfish poisoning. It’s a toxin to keep on your radar if you are a shellfish hunter, or just a fan of eating locally harvested shellfish.
The good news is that paralytic shellfish poisoning is on San Mateo County Environmental Health Services’ radar, with regular monitoring of ocean conditions for this poison by collecting mussels and plankton samples as part of a state and Mussel Monitoring Program.
Every few weeks at lower tides, EHS staff spends a few hours along our beautiful coastline traveling from Pescadero to Pacifica to pluck mussels by hand from rocks and collect plankton samples by dragging large, fine-mesh nets through the water. Mussels are then shucked, frozen and shipped along with plankton samples to the California Department of Public Health’s Marine Biotoxin Monitoring Laboratory to be analyzed for phytoplankton species producing biotoxins.
What are biotoxins and how do they impact our shellfish dinner plans and health? Phytoplankton (also known as algae or microalgae) are tiny organisms that are naturally occurring and are the foundation of the food chain. When certain species of phytoplankton become too abundant they produce biotoxins that accumulate in shellfish like mussels, clams, oysters, crabs and lobsters. If humans or wildlife eat these critters with high levels of biotoxins sickness or death can occur.
While these harmful algal blooms are hard to predict, the samples collected and a mandatory quarantine period set on mussels from May 1 – October 31 helps protect us against harmful effects of contaminated shellfish.
While biotoxins typically impact shellfish from May through October, remember to never assume that sport-harvested (vs. commercially harvested) mussels are safe to eat, even when a quarantine is not in effect, because biotoxins can occur any time. To find out if mussels harvested in San Mateo County should be on your menu, call the information line at 1-800-553-4133 to get updates on current quarantines and health advisories.