Pseudo-nitzschia, a naturally occurring single-celled, marine alga, produces the potent neurotoxin domoic acid under certain ocean conditions. Bivalve shellfish, like clams and mussels, accumulate the toxin without being harmed. In fact, razor clams are known to bioaccumulate domoic acid, meaning it may not clear their system until long after a bloom has abated.
Sampling of razor clams from Crescent Beach in Crescent City in late October found clams exceeding the current federal action level for domoic acid of greater than or equal to 20 parts per million.
Domoic acid poisoning in humans may occur within minutes to hours after consumption of affected seafood and can result in signs and symptoms ranging from vomiting and diarrhea to permanent loss of short-term memory (Amnesic Shellfish Poisoning), coma or death. There is no way to prepare clams for consumption that will remove the toxin – cooking and freezing have no effect.
CDFW will continue to work with the California Department of Public Health (CDPH) and Office of Environmental Health Hazard Assessment to collect, monitor and analyze razor clams to determine when the recreational clam fishery in Del Norte County can be reopened safely.