Here's Why The State Closed California's Crab Fishery

Pacific rock crabs like this one aren't safe to eat for now. | Photo: Oregon Department of Fish and Wildlife


Some Californians are getting an impromptu lesson in bioaccumulation this week, following a vote by the California Fish and Game Commission on Friday to close the commercial rock crab fishery, which operates year-round, and to delay the opening of the Dungeness crab season, which was to start on November 15.

The problem is a nasty little chemical called domoic acid, made up of 15 carbon atoms, 21 hydrogen atoms, six oxygen atoms, and a single atom of nitrogen. Unlike other nasties that bioaccumulate in wild animals, like anticoagulant rodenticides, domoic acid is one hundred percent natural. It's produced inside some species of a group of algae called Pseudonitzschia. These are single-celled plants that drift through the water, occasionally linked together in strands or ribbons.

Together with the California Department of Public Health, the California Department of Fish and Wildlife (CDFW) has been testing crabs in nine ports between Santa Barbara and Crescent City since September, and the most recent set of results suggested that the domoic acid had accumulated to levels that were too high to be safely consumed by humans.


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You've heard of "toxic algal blooms"? These are the microscopic plants to blame. Small critters gobble up the toxic algae, which are then gobbled up by bigger critters, which are then swallowed by even bigger ones, like a predatory set of Russian nesting dolls. As each animal becomes lunch for another, the domoic acid continues to build up at increasingly toxic levels. By the time it's dunked in batter, deep fried, and piled onto your taco, it can be deadly.

The molecule acts as a neurotoxin, affecting the ability of brain cells to operate normally, especially in the hippocampus, part of the brain devoted to memory encoding and retrieval. That helps to explain why short-term memory loss is a common symptom of domoic acid poisoning, also known appropriately as amnesic shellfish poisoning.

More generally, exposure can lead to brain damage, and in the most extreme cases, to coma and death. To that list you can add nausea, vomiting, diarrhea, and abdominal hemorrhaging. The toxins can also attack the kidneys and the heart. Think of it as the worst kind of food poisoning, ever.

"Crab is an important part of California's culture and economy, and I did not make this decision lightly," said CDFW Director Charlton H. Bonham in an official statement. "But doing everything we can to limit the risk to public health has to take precedence."

Unfortunately, the toxins are not affected by freezing or cooking, so the best thing to do when shellfish are chock full of the stuff is to simply avoid eating them. That's is exactly why the CDFW has elected to close coastal crab fisheries for now, while they continue to test shellfish to determine when they may once again be eaten safely.

Algal blooms, toxic or otherwise, are a fairly common phenomenon, but this one seems to be larger and hardier than usual. This could be yet another example to add the long list of weird things lurking off the California coast thanks to the El Niño. To which we say: bring it on! As long as the venomous sea serpents and toxic shellfish come with a heaping side of rainfall.


For ongoing environmental coverage in March 2017 and afterward, please visit our show Earth Focus, or browse Redefine for historic material.
KCET's award-winning environment news project Redefine ran from July 2012 through February 2017.

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