The California Department of Public Health’s (CDPH’s) biotoxin monitoring program began in 1927 in response to a massive poisoning event that occurred after people ate mussels containing high levels of paralytic shellfish poisoning toxin. Several deaths and over 100 illnesses were attributed to the event, according to CDPH.
Domoic acid, which causes amnesic shellfish poisoning, is another potentially deadly and naturally occurring toxin that may be produced after a “bloom” of a single-celled plant called Pseudo-nitzschia. Blooms of Pseudo-nitzschia do not always produce domoic acid, and there is currently no reliable way to predict where or when a bloom will produce the toxin. Crustaceans such as spiny lobster and Dungeness crab, as well as fish and shellfish such as clams and mussels, are capable of accumulating elevated levels of domoic acid without becoming ill themselves.
CDPH began monitoring for domoic acid in 1991 after it was detected in Monterey Bay. While the agency has occasionally posted local consumption warnings in the intervening years, especially in the Santa Barbara Channel and Monterey Bay regions, biotoxin-related events expanded coastwide in 2015 to unprecedented levels.
In fall 2018, CDPH issued a warning to avoid consuming Dungeness crab ten days before the recreational season opened. The announcement warned the public not to eat crab taken from waters north of Patrick’s Point, Humboldt County to the California-Oregon state line. The California Department of Fish and Wildlife (CDFW) issued an official closure of the season in this area following the CDPH warning, delaying the recreational season north of Patrick’s Point until domoic acid no longer poses a threat to human health there. Two days before the season opened, CDPH issued another warning to avoid eating the internal organs (or viscera) of Dungeness crab from the Bodega Bay and Russian River areas, again due to high levels of domoic acid in the viscera.
CDPH’s current domoic acid testing results indicate that crab in some portions of state waters are fine to eat because results come in below FDA thresholds – 20 parts per million in the meat, 30 parts per million in the viscera. The areas where Dungeness crab may be safely taken currently (as of mid-November, 2018) include:
- All areas south of Bodega Head, Sonoma County and
- The area between Salt Point, Sonoma County and Trinidad Head, Humboldt County.
In the areas below, Dungeness crab have tested above FDA thresholds and pose a threat to human health:
- The area between Patrick’s Point, Humboldt County and the California-Oregon border, which remains closed.
- Viscera from Dungeness crab caught near the Russian River have also tested above FDA thresholds. CDPH has issued an advisory to not eat the viscera of Dungeness crab from this area.
CDPH will continue to test crab in California waters, especially from areas that exceed allowable levels, until the threat has declined; state agencies will notify the public accordingly. CDPH posts the latest sampling results on its website – scroll down and click on the first link under “Analytical Data – Crabs”.
Before going crabbing, call CDPH’s Shellfish Biotoxin Information Line toll-free at (800) 553-4133 for the latest advisories. The web pages below provide up-to-date information on health advisories, changes to fishing regulations and seasons, and the latest domoic acid test results by area. You can also contact CDFW environmental scientist Christy Juhasz for further information.
post by Mary Patyten, CDFW Research Writer and Christy Juhasz, CDFW Environmental Scientist