Domoic acid continues to hamper west coast shellfish economy

Blog_ClamsAfter a difficult summer for shellfish, levels of domoic acid (DA) are slowly starting to decrease after peaking in late spring and early summer. Linked to an algae bloom along the U.S. west coast, the high levels of the toxin caused some of the largest shellfish closures ever, a recent article states.

While the closures inevitably caused many shellfish industries to suffer, reports are showing that the level of toxin is slowly starting to decline again and some business are beginning to reopen. The razoring clamming and Dungeness crab industries were some of the hardest hit and while razor clams seem to be getting rid of toxins more quickly than in previous years, Dungeness crab, a multi-million dollar industry for the west coast, has not been as lucky.

“That’s the first time we’ve ever had [crab] closures to such an extent of area for such long periods…that’s a puzzle to us because razor clams have been toxic in the areas in the past and the crab didn’t pick it up at the same rate,” David Ayres of the shellfish division of Washington Fish and Wildlife, said in the article.

Botoxins such as DA can result not only marine wildlife mortality but human mortality as well. The clinical toxicological effects attributed to DA can include permanent loss of short-term memory, nausea, vomiting, headache, disorientation and loss of balance. Most countries have established a maximum permitted level of 20 mg DA per kg whole shellfish (20 ppm).

In Oregon, the algae bloom has also hampered the shrimp industry, due to the algae getting stuck in shrimper’s nets and taking several days to clean out. In Washington, the entire northwest peninsula remained closed to shellfish fishing, while the rest of the Washington coastline varies from beach to beach.

Although these algae blooms are far from uncommon, the article states that this time it came as a surprise both in terms of timing and severity.

“This one is so much bigger than what we’ve seen before, it’s still unclear as to how it’s spread out,” Michael Milstein of National Oceanic and Atmospheric Administration (NOAA) said in the article. “It’s the biggest in terms of geographic extent with higher concentrations than we’ve seen before on the West coast.”

When these types of algae blooms do occur, they tend to happen in the fall, so the late spring start is something of an enigma which the industry was not prepared for.

NOAA launched a coast-wide study earlier this summer soon after the closures began to try to more accurately map the extent of the bloom, and are expecting concrete results in the coming weeks.

“They have collected a lot of samples and those are undergoing analysis,” Milstein said.

Scientists cannot say for sure how long levels will remain high, as it largely depends on water temperatures.

“It all depends on the temperatures, and all indications show that temperatures are still warm, and that’s going to continue until storms come along or something breaks it up and circulates more water to reduce the temperatures,” Milstein added.

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