1. Domoic acid: a naturally occurring neurotoxin with the chemical composition of C15H21NO6. This amino acid is produced by certain types of microscopic algae, especially of the genus Pseudo-nitzschia, of which 23 of the known 48 species generate the toxin responsible for amnesic shellfish poisoning.
While there are always scant amounts of domoic acid present in ocean waters where the algae is found, it is when the algae blooms that shellfish, sardines and anchovies absorb levels of the toxin that can become dangerous to the birds, sea mammals and humans that consume them. Amnesic shellfish poisoning can cause confusion, vomiting, seizures, brain damage and death.
The bivalves, crustaceans and small forage fish that regularly consume this phytoplankton are unaffected by the degenerative effects that occur higher up the food chain and, with time, will excrete the concentrated toxin and be safe to eat again. The international and national standard for domoic acid in shellfish meat unfit for human consumption is 20 parts per million
Also called demoate in neurophysiological jargon, domoic comes from the Japanese, dōmoi, ドウモイ, which is a regional word from the Tokunoshima Island dialect meaning, “seaweed,” where the toxin was first isolated from a species of red algae known as Chondria armata in 1958. For many years, the toxin was used there as an antiparasitic drug, often to deworm Japanese children.
Its first known use as domoic in English is traced to 1982. It is now widely believed that an August 1961 incident in which hundreds of sea-birds dive-bombed the city of Capitola, California, which served in part as inspiration for Alfred Hitchcock’s “The Birds,” was the result of domoic acid poisoning the fowl after a feast on local anchovy.
The toxin was first officially detected on the west coast in 1991 and has been the scourge of Dungeness and razor clam seasons for many years since.
“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 or ‘butter.’ Cooking or freezing affected fish or shellfish tissue does not lessen the toxicity.”
— Washington Department of Fish & Wildlife, “DOMOIC ACID - A major concern to washington state’s shellfish lovers,” http://wdfw.wa.gov/fishing/shellfish/razorclams/domoic_acid.html, accessed Aug. 7, 2017
“Just as the unexplainable avian attacks in ‘The Birds’ have terrified movie buffs for more than half a century, the 1961 frenzy puzzled scientists for decades. They now believe the culprit was domoic acid — the same neurotoxin that has delayed this year’s Dungeness crab season in California.”
— Laurel Hamers, “This Hitchcock movie was inspired by crab toxin frenzy in Capitola,” The Mercury News, Dec. 7, 2015