Deadly toxin shuts down some Southeast Alaska oyster farms

Some oyster farmers in Southeast Alaska are closed for business due to high levels of paralytic shellfish poison, or PSP, found in the mollusks.

The toxin, created when the Alexandrium algae bloom produces the chemical saxitoxin, can be consumed by clams and oysters, where it can accumulate to levels that are deadly to humans without affecting the mollusks. Crabs feasting on shellfish can also collect deadly levels of the toxin in their guts without problems — for them.

Paralytic shellfish poisoning in humans often starts with a tingling of the lips and tongue, followed by numbness in the extremities and difficulty breathing. The toxins accumulate in the body and block sodium channels in neurons, eventually leading to paralysis. Consuming large amounts of the toxin can result in death less than two hours after eating the tainted food.

Last year, a clammer with PSP was rushed to Anchorage, where he was placed on ventilators to help with breathing. The first and worst outbreak in Alaska history was in 1799, when a hundred otter hunters in the Russian fur trade died from eating toxic mussels. From 1993 to 2014, the Alaska Department of Health and Social Services recorded 117 cases of PSP, resulting in four deaths.

The exact cause of PSP-causing Alexandrium blooms, common in the U.S. East and Gulf coasts, is unknown and attributed to a variety of water conditions, according to a fact sheet from the Alaska Division of Public Health. Algae blooms thrive in warmer water, though, and increased precipitation and glacial melt might promote further growth in Alaska.

While PSP has been observed for many years in Southeast Alaska, Prince William Sound and Kodiak, Kimberly Stryker, program manager for Alaska's Food Safety and Sanitation Program, says that over the last couple of years the program has seen elevated levels of the toxin in places not accustomed to it.

"This is definitely something that is concerning for us," Stryker said. "We are very fortunate to have pristine water in Alaska, but we have a long history with PSP. And it's a scary thing."

Shikat Bay Oysters, located in Naukati Bay on Prince of Wales Island, is one of the oyster farms currently with high levels of PSP. Elevated levels of PSP were first recorded in tests in early June, according to Abby Twyman, Shikat Bay Oysters' director of operations. The next week the farm was officially closed after oysters tested over the limit of 80 micrograms per 100 grams. It has been closed since.

Southeast Alaska Tribal Ocean Research, which monitors recreational shellfish harvesting spots in the region, has also found elevated toxin levels in multiple sites. Its latest update Friday showed 10 spots in Southeast Alaska with an advisory in place for all shellfish species in the area.

Twyman said that this is the longest Shikat Bay Oysters has had issues with PSP since her parents started the farm in 2009. The first and only other time the farm detected the toxin was last year, an event that lasted one week

And it's not only her operation that has been affected: According to Twyman, all of the farms in the area have been testing "hot" for PSP since early June, and only one has reopened.


The shutdown has come during the busiest season for Shikat Bay Oysters, according to Twyman, when a rush of tourists and fisherman to the area usually brings in the bulk of sales for the year.

"This is abnormal and we are just trying to get a sense of it, if this is the new reality," Twyman said.

This long period of suspended business is not uncommon when an area tests positive for high PSP levels, according to Stryker. This is because a farm needs three consecutive clean samples — taken a minimum of four days apart — to reopen, and oysters can take several weeks to pass out the poisons from harmful blooms.

Still, Stryker said that the state is seeing "all sorts of strange things" when it comes to PSP in oysters and clams.

"Alaska seems to be a canary in the coal mine when it comes to these kinds of things," Stryker said. "We are vigilant and paying attention and trying to draw conclusions — but that takes a lot of research."

For now, Stryker recommends that people be hyper aware when they choose to dig for clams on Alaska's coasts, or put off recreational harvesting altogether. While she says that all Alaska shellfish found in stores is safe, clams found outside of commercial businesses are risky.

"If people don't want to heed our advice, and go out and harvest — I recommend they make sure they know the symptoms of PSP and where the nearest medical care is," Stryker said.

As for Shikat Bay Oysters, taking inventory and developing new baby oysters will keep the team busy until they are able to sell again.

"We are hardy Alaska stock and we aren't going to let something like this keep us down," Twyman said. "We are just making a new plan."

Kelsey Lindsey

Kelsey Lindsey is a 2017 graduate of the Columbia University Graduate School of Journalism and is covering Arctic-related issues as part of an Alaska Dispatch News-Columbia fellowship.