Domoic acid, a naturally occurring toxin produced by certain types of algae, can be harmful or even fatal to humans if contaminated shellfish is consumed. The toxin was detected initially on the west coast in 1991.
Shellfish and fish can accumulate domoic acid without apparent ill effects. Research has shown that razor clams accumulate domoic acid in edible tissue and are slow to expel the toxin. In Dungeness crab, domoic acid primarily accumulates in the viscera (internal organs) or “butter.”
Amnesic shellfish poisoning
Cooking or freezing shellfish does not destroy domoic acid in shellfish. Domoic acid can be fatal to people if consumed in high doses. There is no antidote for domoic acid, which causes a condition called amnesic shellfish poisoning (ASP). Symptoms include vomiting, nausea, diarrhea, and abdominal cramps within 24 hours of ingestion. In severe cases, neurological symptoms develop within 48 hours and include headache, dizziness, confusion, loss of short-term memory, motor weakness, seizures, profuse respiratory secretions, cardiac arrhythmia, and coma.
Testing for domoic acid
Since the discovery of domoic acid along the Washington coast, regular samples of razor clams are collected by Washington Department of Fish and Wildlife (WDFW) staff in cooperation with the Quinault Indian Nation. Samples are analyzed by the Washington Department of Health (DOH). State health officials have determined levels of domoic acid above 20 parts per million in shellfish meat tissue are unsafe for human consumption. This is also an accepted standard both federally and internationally.
The most recent test results for domoic acid on Washington’s beaches can be found on the department’s domoic acid reports webpage.
Outbreaks in Washington
WDFW curtailed spring razor clamming early in 2015 due to elevated levels of domoic acid. Commercial and recreational crabbing also was closed on the Washington coast for part of the summer of 2015 due to domoic acid, which continued to disrupt fisheries in 2016 and 2017.
Previous outbreaks have prompted the cancellation of three entire razor clam seasons in Washington in 1991-92, 1997-98 and 2002-03. Kalaloch Beach, jointly managed by WDFW and Olympic National Park, also was closed for much of the 2004 season due to high toxin levels. In 2005, WDFW closed Long Beach for two days due to elevated toxin levels.