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Domoic acid: How the toxin can impact Washington's razor clam season

Digging for razor clams is a time-honored PNW tradition. Scientists, tribes and partners are working to make sure the shellfish are safe to eat.

LONG BEACH, Wash. — The Washington Department of Fish & Wildlife announced tentative razor clam dig days stretching into May as scientists and others work to ensure the shellfish are safe to eat. 

The agency coordinates mandatory toxin testing as required by the Washington State Department of Health, assessing the clams for levels of "domoic acid." 

Shellfish managers, scientists, tribes and partners have worked in recent years to develop and advance early monitoring and warning systems to protect people and safeguard industries and traditions across the northwest. 

Bryce Blumenthal is a coastal shellfish biologist for Fish & Wildlife. He surveys people digging for clams to get a sense of the razor clam population.

"It's a uniquely Northwest activity," Blumenthal said. "It's tied into our identity, it's something that people can do at all ages -- when they're born here, they can do it their whole life." 

He said partners work together to sample razor clams for three different toxins. 

"The toxin that shuts us down most often and gets talked about the most is domoic acid," Blumenthal said. "Domoic acid causes amnesic shellfish poisoning, in severe cases it causes death and permanent brain damage and in mild cases it's an upset stomach and a pretty bad time - so it can be very serious."

The acid was first to blame for closing razor clam digs in the 1990s when more than 20 people got sick from poisoned shellfish. A Department of Health lab first discovered domoic acid in razor clams and the state cancelled the rest of the season. 

The toxin grows after sunlight, warm temperatures and shallow water make algae grow faster into large blooms. There are several types - many harmless - across the northwest. But the type "pseudo-nitzschia" can produce the toxin domoic acid. Razor clams consume it, and while it doesn't kill them, it can cause sickness in people and animals who eat them. 

When levels of domoic acid exceed a safe level, Fish & Wildlife must issue a closure. Both Washington and Oregon have been forced to do so sporadically near summertime or around marine heatwaves, though at this point the agency has not identified a clear trend line. 

"The big question mark is, is this our new normal? Are we gonna see more, every other year or closure every other year?" Blumenthal said. "That's not the work we do, we just manage the fishery and roll with the punches as they come."

Some researchers are looking into what the future could bring. A recent study examined how a marine heatwave sparked a new domoic acid hotspot on the West Coast, and more work is being done to unearth trends.

In the meantime, scientists and local partners have developed early detection and warning systems to help gain a better understanding of exactly which areas are impacted, so closures only happen when they have to. 

"There's a lot of people who come out here and stay in hotels and patron local businesses, so it's a huge economic driver for coastal Washington," Blumenthal said.

Approved and tentative razor clam digs

Confirmed dates during morning (midnight to noon, except until 1 p.m. on April 13-14) low tides:

  • April 8, Monday, 6:44 a.m.; -0.5 feet; Mocrocks
  • April 9, Tuesday, 7:29 am.; -1.2 feet; Long Beach, Mocrocks
  • April 10, Wednesday, 8:14 a.m.; -1.5 feet; Long Beach, Twin Harbors, Copalis
  • April 11, Thursday, 9:00 a.m., -1.4 feet; Long Beach, Twin Harbors, Copalis
  • April 12, Friday, 9:48 a.m., -1.1 feet; Long Beach, Twin Harbors, Mocrocks
  • April 13, Saturday, 10:40 a.m., -0.5 feet; Long Beach, Twin Harbors, Mocrocks (digging extended until 1 p.m.)
  • April 14, Sunday, 11:38 a.m., 0.1 feet; Long Beach, Copalis (digging extended until 1 p.m.)

Tentative dates during morning (midnight to noon) low tides:

  • April 23, Tuesday, 6:58 a.m.; 0.0 feet; Copalis
  • April 24, Wednesday, 7:30 am.; -0.4 feet; Long Beach, Mocrocks
  • April 25, Thursday, 8:03 a.m.; -0.6 feet; Long Beach, Twin Harbors, Mocrocks
  • April 26, Friday, 8:39 a.m., -0.7 feet; Long Beach, Twin Harbors, Copalis
  • April 27, Saturday, 9:19 a.m., -0.7 feet; Long Beach, Twin Harbors, Copalis
  • April 28, Sunday, 10:05 a.m., -0.5 feet; Long Beach, Twin Harbors, Mocrocks
  • April 29, Monday, 10:58 a.m., 0.3 feet; Long Beach, Mocrocks

Tentative dates during morning (midnight to noon) low tides:

  • May 6, Monday, 5:41 a.m.; -0.7 feet; Mocrocks
  • May 7, Tuesday, 6:28 a.m.; -1.5 feet; Long Beach, Mocrocks
  • May 8, Wednesday, 7:13 a.m.; -2.0 feet; Long Beach, Copalis
  • May 9, Thursday, 7:57 a.m.; -2.1 feet; Long Beach, Twin Harbors, Copalis
  • May 10, Friday, 8:41 a.m.; -1.9 feet; Long Beach, Twin Harbors, Mocrocks (Long Beach Razor Clam Festival)
  • May 11, Saturday, 9:27 a.m.; -1.4 feet; Long Beach, Twin Harbors, Mocrocks (Long Beach Razor Clam Festival)
  • May 12, Sunday, 10:16 a.m.; -0.8 feet; Long Beach, Twin Harbors, Copalis

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