DOH Marine Biotoxin Bulletin
Beach closure listing due to red tide and other marine toxins
WDFW Olympic Region Harmful Algal Bloom (ORHAB) project

DOMOIC ACID - A major concern to washington state’s shellfish lovers

Check here for the most up-to-date domoic acid levels in razor clams on all beaches
Newsclip of domoic acid beach closure

In 1991, a relatively new marine toxin, domoic acid, was first detected on the West Coast of the U.S. When this marine toxin was discovered in certain West Coast fish and shellfish, recreational and commercial fisheries were closed. These closures had serious economic impacts on those communities dependent on these fisheries. One of the most heavily impacted was Washington’s razor clam fishery, which remained closed for a full year.

In North America, domoic acid has been responsible for several deaths and both permanent and transitory illness in more than 100 people. The toxin is produced by marine diatoms, which are members of the genus Pseudo-nitzschia. Both shellfish and fish can accumulate this toxin without apparent ill effects. However, in humans the toxin crosses into the brain and interferes with nerve signal transmission.

Eating of fish or shellfish containing the toxin causes the human illness known as amnesic shellfish poisoning (ASP). Symptoms include vomiting, nausea, diarrhea and abdominal cramps within 24 hours of ingestion. In more severe cases, neurological symptoms develop within 48 hours and include headache, dizziness, confusion, disorientation, loss of short-term memory, motor weakness, seizures, profuse respiratory secretions, cardiac arrhythmia and coma. People poisoned with very high doses of the toxin can die. There is no antidote for domoic acid. Research has shown that razor clams accumulate domoic acid in edible tissue (foot, siphon and mantle) and are slow to depurate (purify) the toxin. Research has also proven that cooking or freezing affected fish or shellfish tissue does not lessen the toxicity.

In 1987, more than 100 individuals became ill after consuming cultured mussels (Mytilus edulis) harvested off the Canadian province of Prince Edward Island. The mussels were found to be contaminated with domoic acid, which had previously not been observed in shellfish. This 1987 incident led to the subsequent death of three elderly individuals and caused permanent short-term memory loss in several survivors.

The deaths of more than 400 California sea lions in 1998 have been traced to a domoic acid-producing algae. An examination of the animals showed their brain tissue had been almost totally destroyed by domoic acid. It was found that the sea lions had eaten large quantities of anchovies, small fish that had fed on the domoic acid-producing algae.

Since the 1991 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 turned over to the Washington Department of Health (DOH). Domoic acid levels in these samples are then measured using a chemical technique known as high performance liquid chromatography (HPLC) at the DOH Public Health lab in Shoreline, Washington. The level of domoic acid determined to be unsafe for human consumption by the Federal Food and Drug Administration (FDA) is 20 ppm in shellfish meat tissue. In 1992 DOH choose to adopt the lower action level of 15 ppm because of the rapid rate domoic acid levels can rise thus providing an additional safety buffer. In September of 2000, DOH decided to return to the 20 ppm federally accepted action level. This decision was a direct result of the close cooperation between WDFW and DOH speeding the collection, delivery and analysis of razor clam samples for domoic acid.

Washington State Recreational Razor CLam Fishery Economic ContributionThere have been three serious disruptions to the highly popular razor clam fishery: the initial closure that began in November 1991 and ended in November 1992; the year-long closure that began in October 1998 and ended in October 1999; and the most recent closure that began in October 2002 and has continued into 2003. The 2002-03 closure alone is conservatively estimated to represent a $10.4 million loss to the economies of Washington’s small coastal communities.

Currently, WDFW is actively participating in the federally funded Olympic Region Harmful Algal Bloom (ORHAB) project. See also the WDFW ORHAB web page. This study provides the hope of developing an “early warning” system to avoid massive disruptions caused by last-minute fishery closures, while still protecting the health of thousands of consumers.


An interesting side note:

One morning in the summer of 1961, hundreds of crazed birds attacked the seaside town of Capitola, California. The birds "cried like babies" as they dove into street lamps, crashed through glass windows, and attacked people on the ground. Most of the birds were sooty shearwaters, a normally non-aggressive species that feeds on small fish and comes ashore only to breed. This incident fascinated Alfred Hitchcock, who frequently vacationed in nearby Santa Cruz. He included newspaper clippings about the Capitola attack in his studio proposal for THE BIRDS, which appeared in cinemas two years later. The agent responsible for the attack is now widely thought to have been domoic acid.


For additional information:
WDFW Region 6 Office
(360) 249-4628
(ask for the razor clam management staff)