Dungenness crab toxicity a vexing issue

Note: The following is one of several stories about the crab and fisheries calamities.

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Paul Mann
Mad River Union

SACRAMENTO – Lifting California’s ban on crab fishing depends on registering two weeks’ worth of test results that show levels of a neurotoxin called domoic acid are no more than 30 parts per million (ppm) in crab viscera and 20 ppm in crab meat.

With recent samples below alert levels, the belated opening of the commercial Dungeness crab fishery could occur as soon as this week. That is according to a communiqué issued Feb. 11 by the state’s Department of Fish and Wildlife, in consultation with the Dungeness Crab Task Force Executive Committee.

Statistics published Feb. 12 by the California Department of Public Health and based on six samples taken Feb. 1 showed an average domoic acid level for Crescent City north of 2.5 to 21 ppm. The Crescent City south reading was 2.5-17.FacebookLikeButton.THISONE

Feb. 2 readings for Trinidad north averaged 28 ppm; Trinidad south 4.9-25 ppm.

In Eureka, the Samoa average was 14 ppm; the Eel River reading was 21 ppm.

Six samples were taken in each test and all three locations exhibited toxic levels both above and below the 20 ppm regulatory threshold.

It is these divergent and persistent fluctuations in acid levels that throw the lifting of the ban into continuing doubt. And state authorities are worried that 2016 may see more of the large and long-lasting algal blooms that produce high volumes of domoic toxin, as happened last year.

Although several weeks of tests have been reassuring in some coastal areas, state public health agencies have cautioned against eating crab viscera (internal organs, “butter” or “guts”). Water or broth used to cook whole crabs should be discarded, not used as sauces, soups or stews, the agencies say.

When whole crabs are cooked in liquid, domoic acid may leach from the viscera into the cooking liquid. The viscera usually contain much higher levels of domoic acid than crab body meat.

The historic crab shutdown and the likely persistence of warm Pacific waters have triggered intensive debate in Sacramento and in the industry about whether the 30 ppm and 20 ppm regulatory levels are the right ones.

At a hearing last week of the state legislature’s Joint Committee on Fisheries and Aquaculture, Dr. Clarissa Anderson of the Institute of Marine Sciences faculty at UC Santa Cruz said rock crab have been found with levels as high as 1,000 ppm; Dungeness crab 270 ppm; mussels up to 270 ppm. Very high levels have been found in razor clams, ling cod and other rock fish.

She described crab viscera as “extremely hot” – sky-high acid levels – and anchovies as “extremely contaminated.”

FacebookLikeButton.THISONEMuch more needs to be understood about how the toxin affects vertebrates, Anderson testified. It is an ongoing area of study “and I will not be popular in this room when I say that a lot of the recent research indicates that maybe our [20 ppm and 30 ppm] thresholds are not strong enough. I don’t know what’s going to become of that and it’s going to be an FDA [Food and Drug Administration] issue,” which is already being debated internally.

What is known, Anderson continued, is that humans who subsist, for example, on razor clams in the Pacific northwest, with chronic exposure to low levels of domoic acid, experience definite physiological effects. She did not spell them out but said as a reference point that the brains of California sea lions “are extremely damaged from lifetime exposure. We need to figure out what those acute [threshold] levels should be” for humans.     

Lawmakers, industry leaders and scientists agree that California will have to finance millions of dollars in extensive research to determine the enduring effects of domoic acid and how best to regulate it for public safety.


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