PENINSULA — Health officials hit the pause button on fall razor clam digging on Oct. 21 because samples taken from outer coast beaches are trending toward having too much marine toxin.
Clams harvested in the past week were within the safety threshold and are still safe to eat, according to the Washington Department of Health.
“Razor clams screened for DA [domoic acid] on Friday [Oct. 16] did show an increase in DA, however they remained below the closure level,” Zach Forster, the Nahcotta-based coastal shellfish biologist with the Washington Department of Fish and Wildlife, said in an Oct. 22 email. “Projections by DOH [the Washington Department of Health] predicted that clams would be approaching closure levels by Wednesday, and that clams dug before then would therefore still be safe to consume.”
Domoic acid is sometimes produced as a bi-product of the otherwise harmless microscopic marine organism Pseudo-nitzschia. DA symptoms range from gastrointestinal distress to loss of memory functions as a result of amnesic shellfish poisoning. The worst-case result is death, though this most often occurs in birds and marine mammals that consume large quantities of tainted shellfish.
In Washington state, clam harvests are stopped when DA levels in the meat surpass 20 parts per million. Levels were about 1 ppm most of the summer and fall through Oct. 8, before starting to increase.
WDFW and DOH are sometimes able to predict DA trends by sampling offshore seawater, but such work isn’t currently being done. So the decision to close was based on beach monitoring by the Olympic Region Harmful Algal Bloom program.
In the present situation, DOH’s decision to close was based on pre-screening results that showed a DA increase in samples collected on state beaches between Oct. 16 and 20. DA levels doubled in that period. “In previous DA events, there is a high correlation between these DA concentrations and DA concentrations in razor clams,” Forster said. Results on Oct. 20 showed particulate DA levels that were significantly higher than those that caused clams to spike to 29 ppm over a similar period in 2016, he said.
Domoic acid has been the bane of numerous razor clam digs in the past 30 years, when DA first started to be detected on the Pacific Northwest coast. Sometimes it passes within weeks, but it has been known to scuttle entire seasons. At this point, it’s too soon to predict how this outbreak will play out.
“State shellfish managers will consider openings tentatively scheduled to start Oct. 31, depending on the results of upcoming marine toxin tests and public health officials’ ongoing monitoring of covid-19 trends,” Larry Phillips, WDFW’s coastal region director, said in an Oct. 21 press release announcing the emergency closure.
The factors that cause Pseudo-nitzschia to produce DA are still incompletely understood. However, warmer than normal ocean water is often viewed as a contributing reason for the phenomenon. This fall has seen the development of another warm-water “blob” in the North Pacific — especially just off the Oregon and Washington coast — sparking concerns about the potential for domoic acid production.
On Oct. 14, the waters off the Washington coast were as high as 5 to 9 degrees above normal, University of Washington meteorologist Cliff Mass reported in his popular weather blog. The average over the preceding month was around 3 to 5 degrees above average.
An unexpected surge in recreational clam diggers descended on the peninsula over the weekend.
The second fall dig of the season, which started Oct. 14, drew a considerably larger crowd than the first scheduled dig in late September.
Participation estimates for the Long Beach Peninsula over the weekend were 5,500 on Friday, Oct. 16, 9,500 on Saturday, Oct. 17 and 3,000 on Sunday, Oct. 18, according to WDFW.
“Coast-wide, the turnout was surprisingly high and a lot of us remarked that it resembled a morning spring dig,” said WDFW Coastal Shellfish Technician Bryce Blumenthal on Oct. 19.
Diggers reported finding fast limits and fat clams from Seaview to Oysterville, including some behemoth mossbacks that exceeded six inches. The heavier clams come with the changing season, Blumenthal explained.
“The main spawn occurs during the summer and the clams gain body mass after that, especially when storms and high surf begin bringing more clam feed to the shore,” Blumenthal said.