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Toxic Rock Crabs: Cal Dept. of Public Health Warning About Seafood

Dangerous acid detected in Half Moon Bay and Monterey Bay


August 25, 2016

Until the advisory is lifted, Rock Crabs caught in the designated areas may cause severe illness.

The California Department of Public Health (CDPH) is warning consumers not to eat rock crabs caught in Half Moon Bay and bivalve shellfish or rock crabs caught in Monterey Bay, due to the detection of dangerous levels of domoic acid, a naturally occurring toxin.

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. There have been no reported illnesses associated with this event.

This advisory covers consumption of recreationally or commercially caught rock crab or recreationally caught mussels, clams, and the internal organs (viscera) of scallops caught in the specified area. Dangerous levels of domoic acid have been detected in some of these species and are also likely to be present in the other species mentioned above. Domoic acid accumulation in seafood is a natural occurrence that is related to a 'bloom' of a particular single-celled plant. The conditions that support the growth of this plant are impossible to predict.

Analysis of rock crabs recently caught in Half Moon Bay found domoic acid levels in the viscera at more than ten times the action level, which is set at 30 ppm. While portions of Half Moon Bay, north of Pigeon Point, remain under a fishery closure, the spike in these levels in conjunction with an increase of the levels of domoic acid found in rock crabs and bivalves to the south in Monterey Bay, raise concern for crabs and bivalves taken from this entire geographic region.

Bivalve shellfish have a two-part, hinged, shell.

This warning does not apply to commercially sold clams, mussels, scallops or oysters from approved sources. 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.

CDPH will continue to coordinate its efforts with the California 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. For additional information, visit CDPH's Natural Marine Toxins: PSP and Domoic Acid Web page and CDPH's Domoic Acid health information Web page.


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