Levels of domoic acid 10 times the “action level” in certain shellfish along the Central Coast spurred California officials to issue a public warning against eating rock crabs and bivalve shellfish caught in the area. Specifically, Half Moon Bay rock crabs and Monterey Bay rock crabs and bivalve shellfish are on the danger list for now, according to the California Department of Public Health. rock crab warning illustrationThe high levels of the naturally occurring toxin are related to unpredictable “blooms” of a particular single-celled aquatic plant. No illnesses had been reported as of the Friday evening warning. Commercially sold clams, mussels, scallops or oysters from approved sources are not included in the warning. State law permits only state-certified commercial shellfish harvesters or dealers to sell these products. Shellfish sold by certified harvesters and dealers are subject to frequent mandatory testing to monitor for toxins. “This advisory covers consumption of recreationally or commercially caught rock crab or recreationally caught mussels, clams, and the internal organs of scallops caught in the specified area,” according to the health department notice. “The warning is effective for crabs and bivalve shellfish caught in state waters south of Latitude 37° 11′ N, near Pigeon Point, and north of Latitude 36° 35′ N, near Cypress Point in Monterey County.” Symptoms of domoic acid poisoning can occur within 30 minutes to 24 hours after eating toxic seafood. In mild cases, symptoms may include vomiting, diarrhea, abdominal cramps, headache and dizziness. These symptoms disappear within several days. In severe cases, the victim may experience trouble breathing, confusion, disorientation, cardiovascular instability, seizures, excessive bronchial secretions, permanent loss of short term memory — a condition known as Amnesic Shellfish Poisoning — coma or death. The California health department will continue to coordinate its efforts with the state’s Department of Fish and Wildlife and the fishing community to collect rock crab samples from the central and northern California coast until the domoic acid levels have dissipated. To receive updated information about shellfish poisoning and quarantines, call CDPH’s toll-free Shellfish Information Line at 800-553-4133. (To sign up for a free subscription to Food Safety News, click here.)