Last week Wrangell’s Indian Environmental General Assistance Program office issued an alert regarding potentially dangerous shellfish.
Readings for butter clam samples taken from the south side of Zarembo Island earlier this month came back surprisingly high for saxitoxin, the root cause of paralytic shellfish poisoning (PSP) in humans. The Food and Drug Administration sets a safety threshold for consuming saxitoxin at 80 micrograms (μg) per 100 grams of shellfish. The butter clams sampled at Zarembo came back at 884 μg.
As a contrast, the IGAP office issued alerts at Shoemaker Bay beaches last August for readings of 212 μg, and this January issued a similar warning for butter clams near Pats Landing reading 115 μg.
Saxitoxin is produced by the phytoplankton Alexandrium, large blooms of which can taint nearby waters. Area filter feeders like clams and oysters absorb the toxin, which can be transmitted to humans upon ingestion. Symptoms of PSP tend to begin with numbness of the oral membranes, and severe cases can entail nausea, vomiting, neurological effects, paralysis, respiratory failure and ultimately death.
While not being harmed by it themselves, shellfish eventually process out the saxitoxin levels in their bodies over time. For example, butter clams measuring 212 μg last summer showed readings of 104 μg by Thanksgiving.
Different species absorb but also
relinquish toxin levels differently than others. Blue mussels do so relatively quickly, and Wrangell IGAP technician Kim Wickman explained this quality makes them a particularly good test subject to gauge current water conditions at local beaches. While a cautionary alert remains in effect for butter clams at Shoemaker and Pats, blue mussels tested there last week showed saxitoxin levels of 47 and 36 μg, respectively, and are fine to consume.
“They’re kind of our indicator species,” said Wickman. Another batch was sent out on Tuesday.
Wickman takes samples on a regular basis from Shoemaker and Pats, and the Zarembo sampling was a surprising outlier. The site had been chosen by a local family, which nominated the site after winning a drawing from the IGAP booth at the April 1 community health fair.
“It means there’s a lot more areas with PSP than we thought,” Wickman explained.
Resources are also available for those wishing to arrange a test for specimens from their preferred gathering-grounds. The Sitka laboratory that runs the tests prefers its samples live, and some forms and arrangements need to be taken care of through the office beforehand.
Information on different shellfish species is available at the IGAP office, inside the Wrangell Cooperative Association quarters on Lynch Street.
“People also need to know their shellfish,” she added, and materials helpful to identifying different species are on hand.
Shellfish conditions are made public through the Sitka-based organization Southeast Alaska Tribal Ocean Research. Its Southeast Alaska Tribal Toxins website is maintained at http://www.seator.org/data. The site collects updated data from 28 different sites in 16 communities around Southeast, focused on saxitoxin, domoic acid and other harmful toxins to be found in shellfish.
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