Climate change is turning shellfish toxic — and threatening Alaska Natives

In a typical Alaska Native community, 30 percent of the households harvest 70 percent or more of that enclave’s wild food. The bounty is shared among family members and given to single mothers, the elderly, and the disabled. It’s impossible to separate the communal aspect of subsistence living from the sustenance it provides. “It’s the Native way to share,” Delores Stokes, a Qagan Tayagungin Alaskan who grew up in Sand Point, a town on an island southwest of Kodiak, said. “If I got some clams I would offer, ‘Would you like some or do you want to come over?’”

She, too, has reason to be wary of shellfish. When she was a little kid fishing with her parents in Sand Point one summer, a man in a boat next to theirs ate some butter clams and died before he could even get to the beach. Years later, as a teenager, Stokes saw toxic shellfish poisoning up close again, when a man was medevaced to a clinic she was working in with a severe case of PSP. “His tongue was starting to swell up and he had red blotches on his face,” she said. “His fear, you could feel it.”

The last time she ate shellfish was in late April, when her neighbor harvested a batch of butter clams and called her with the good news. “I’ll be right there,” she said, and headed to the harbor. She ate the clams roasted on the half shell. “It was wonderful,” she recalled, relishing the memory. Stokes follows a simple tradition like many others — including Mary Haakanson: only harvest shellfish in months with an “R” in the name: September, October, November, December, January, February, March, and April. Following this rule didn’t eliminate the risk of PSP, but it reduced it.

At least, that was true in the past. Now, times are changing.

This summer, independent shellfish testing sites all over the state reported spikes in toxin levels, possibly related to the historic high temperatures in the water surrounding Alaska. And those warming waters are creating the ideal conditions for the algae that produce the toxin to propagate year-round, some researchers say.

Grist / Clayton Aldern

Already, the incidence of PSP is creeping up in cooler months: September, October, March, and April. When Bruce Wright, senior scientist with the Aleutian Pribilof Islands Association, visits Native communities in Southeast Alaska, elders tell him that they’ve seen more PSP incidents, more months of the year when the PSP toxin is active, and higher toxicity levels than in the past. The “R” rule could soon become unreliable, if it hasn’t already.

The data coming out of the few areas of the state with regular testing hint that PSP’s toxin could one day become omnipresent in Alaskan waters, intensifying in places where it’s already found, and also creeping toward the North Pole, where it could spread into the North Atlantic and North Pacific oceans. The consequences for harvesters who are unfamiliar with PSP or have long believed that its toxin disappears when the seasons change has the potential to be catastrophic.

A small cadre of environmental researchers, tribal community members, and concerned citizens are trying to keep tabs on the chemical agent in shellfish in Southeast Alaska in order to protect subsistence fishers from this hidden threat. But challenges abound, ranging from lack of government funding to a simple lack of manpower to the fact that many Alaska Natives will likely never stop eating shellfish, no matter the risks.

Shellfish, said Coral Chernoff, a Cheyenne artist living in Kodiak, are part of the fabric of Native life, so ubiquitous they’re nearly unnoticeable — until they’re gone. Her ancestors used shells for beads and earrings, a tradition she continues in her studio. She and her family used to harvest butter clams and eat them roasted or steamed on the beach. Her Alutiiq father could eat dozens of clams, she said, as many as she could cook. But she harvests alone now. The rest of her family, scared off by the threat of PSP, may never hunt shellfish again.


A journal kept by the Russian navy officer Gavriil Davydov documents one of the first written accounts of PSP. A hunting party returning to Kodiak from Sitka, in southeastern Alaska, in 1799 stopped to spend the night in a cove where clams and mussels grew in abundance. Minutes after finishing their dinner, six Native Americans died. “All those who had eaten the shellfish grew very frightened — but no one knew what to do to help,” Davydov wrote. “Some ate sulphur, others rotting iukola [strips of dried or smoked fish], others tobacco or powders to induce vomiting.” Over the course of the next few hours, nearly 100 men died — an invisible massacre. The officer’s account noted that “the same shellfish can be harmful at one time of the year and at other times harmless.”

The unpredictable nature of PSP is one of the most terrifying things about it. Mary Haakanson ate dozens of clams from the same catch that made her daughter, Phyllis Clough, sick all those years ago, and walked away without any reaction.

Grist / FreeTransform / Getty Images

The truth is that without lab equipment, it’s impossible to know when shellfish “go hot.” Saxitoxin, the poison that causes PSP, has no detectable effect on shellfish flesh. You can’t neutralize it by frying, boiling, or freezing like you would with bacteria. Alaskan subsistence fishers call harvesting your own shellfish “Alaskan roulette” — a nod to the fact that shellfish toxicity can vary beach to beach, harvest to harvest, clam to clam.

The poison itself is produced by a tenacious type of algae called alexandrium catenella, which hibernates in hard cysts on the ocean floor when water temperatures drop, biding its time until the sun comes back. When it reemerges, shellfish, one of the ocean’s most efficient filtration systems, rapidly accumulate the algae and the toxin it produces.

Once saxitoxin enters the human bloodstream, it prevents neurons from firing normally. Signs of PSP tend to develop within a half hour: First, a tingling or burning sensation in the fingertips and lips. Then nausea, vomiting, diarrhea, and finally full paralysis of the respiratory system and death. Just one milligram can be fatal, and there is no antidote.

People who have experienced a run-in with PSP and lived to tell the tale aren’t quick to forget it. Dan Clarion, another Old Harbor resident, remembers eating dozens of butter clams one summer when he was a young commercial fisherman with a couple of days to kill in between jobs. Within minutes, he was laid flat on his back, struggling to fill his half-paralyzed lungs with air. Like the majority of people who have survived PSP, he emerged from the incident with a terrifying anecdote and a healthy dose of fear. Now he helps researchers test shellfish for toxins in his village.

According to data collected by the state, four people have died from PSP since 1993, and 120 have fallen ill total. But that number is almost certainly an underestimate, considering tests of butter clams and blue mussels throughout Alaska in the past 30 years have consistently turned up some of the highest levels of saxitoxin in the world.

The size of the state and the far-flung nature of its communities makes keeping track of PSP incidents nearly as difficult as establishing a shellfish-monitoring network. Part of the problem is that folks who have experienced a run-in with the toxin are charged with self-reporting it to the Alaska Department of Health and Social Services, the agency that logs illnesses and, depending on the circumstance, issues public service announcements warning Alaskans of heightened danger. But residents might not know who to call to report the incident, or even know that they’re supposed to report it in the first place, said Louisa Castrodale, an epidemiologist with the department. Those who have experienced a mild case might take it for food poisoning or the flu. Doctors might even confuse symptoms of severe shellfish poisoning with a heart attack. The official records of a problem the department has classified as a public health emergency could be just a tiny fraction of what’s actually playing out on the ground.

According to the statistics on hand, toxic shellfish poisoning hits Kodiak particularly hard. Roughly a third of all reported PSP incidents in Alaska between 1993 and 2014 came from Kodiak and the smaller islands that surround it. Scientists don’t know why area shellfish frequently turn up such high levels of saxitoxin, but data collected by researchers in the Gulf of Alaska over the past several decades show levels many thousands of times greater than the federal limit of 80 micrograms per 100 grams of shellfish flesh (for reference, that’s a little less than one part per million). In the late 1980s — around the time Clough got sick — saxitoxin levels in Kodiak topped 20,000 micrograms. For context, butter clams with just 1,000 micrograms of the chemical have caused near-instant death.

opened clam
A researcher holds a shucked butter clam. The tip of her knife is pointing toward the siphon — the part of the clam that sucks in water and can hold the most concentrated amounts of saxitoxin. Zoya Teirstein / Grist

Tribes have been aware of PSP since long before researchers first extracted its toxin from the flesh of an Alaskan butter clam in 1957. A series of tips and tricks ranging from dubious to mildly effective were all that stood between Alaska Native populations and PSP. Alexandrium thrives in warm water and sunlight, which is a big reason why the “R” rule has served many communities relatively well in the past. Some harvesters also scrape out the gut of the clam and snip off its siphon — the two areas that testing has shown hold the highest concentrations of saxitoxin.

Neither method is reliable. While amounts of the chemical found in shellfish typically dip below 80 micrograms in cold months, dangerous levels have turned up even in the dead of Alaskan winter. A researcher who tested indigenous cleaning methods found that while gutting and snipping the catch did make some types of shellfish less toxic, it did not eliminate the toxin entirely. PSP also affects people differently depending on their body weight, what they ate that day, and how much shellfish they consumed.

Other methods some Natives swear by include first feeding a bit of your catch to the neighborhood cat to see what happens, boiling clams with a silver dollar, or avoiding red tides — which are related to algae but not necessarily to alexandrium. These shaky methods have been used for so long they’re thought of as fail-safes. Every few years, another death proves that they are not. But without a consistent, reliable network to detect outbreaks and warn the population, people along the Alaska coast have few options.


At 6 a.m., the tide was nearly out at Mission Beach, a rocky length of shoreline minutes from Kodiak’s main road. As the sun began to lighten the sky, pinks — a type of salmon that takes Alaskan waterways by storm in autumn — glinted in the waves, and an eagle made slow circles overhead. Across the water, a cluster of dark islands formed a loose line between Kodiak and the Gulf of Alaska. Many of those islands and the islands beyond them are majority Native and only accessible by seaplane, helicopter, or boat.

Andie Wall, an environmental technician, pulled into the parking lot and jumped out of her car. She popped the trunk and began pulling on a pair of waders for her morning’s work. The organization she works for, a health and social services nonprofit called the Kodiak Area Native Association, or KANA, started an initiative in 2019 to test blue mussels, butter clams, and seawater at two traditional harvesting sites in Kodiak for saxitoxin and two other shellfish-borne poisons.

“Part of the reason I took this job is because my family used to eat clams all the time, especially in the summer,” Wall said. After someone got PSP in her town, located on the opposite end of Kodiak Island, word of the danger started to spread through her community. KANA serves indigenous communities in Koniag — one of Alaska’s 13 Native regions — even the villages you can only get to by boat.

Andie Wall and colleagues
In 2019, Andie Wall (left), an environmental technician with the Kodiak Area Native Association, started testing blue mussels and butter clams at two traditional harvesting sites. Courtesy Andie Wall

Wall and a couple of volunteers spread out over the beach, tailed by Wall’s energetic white labrador, Izzy. First, they plucked 70 blue mussels from the beds exposed by the receding tide. Using shovels and rakes, they dug holes three feet deep in the sand, looking for elusive butter clams. Every once in a while a little spout of water shot up out of the hole in the sand inches from where the volunteers were scraping around in the muck — proof the clams were down there. Half an hour later, the volunteers had about a dozen clams, which is enough to send off for testing.

During the previous several months, Wall had recorded three potent marine toxins at each location where she had conducted tests. One of them, of course, causes PSP; the other two respectively cause diuretic shellfish poisoning, which can induce prolonged bouts of diarrhea, and amnesic shellfish poisoning, which can cause short- and long-term memory loss. That data goes on the KANA website and various community Facebook pages. When toxins spike into the thousands of micrograms, Wall and other researchers in Kodiak will reach out to local media outlets, who can disseminate the information to a wider audience. “We’re not going to go red alert every time it’s above the regulatory limit because chances are, in Kodiak, it’s above the regulatory limit,” she said.

Back at the lab, Wall stood over the sink and cracked open the butter clams and mussels dug up at Mission Beach and Trident Basin, another testing site a few miles away. She packaged up the soft flesh and sent it by plane to Sitka, where the state’s only lab dedicated to testing non-commercially harvested shellfish is located. It’s run by Chris Whitehead, a shellfish biologist who spent years working on a statewide warning system for toxic shellfish poisoning in Washington state.

Now in its third year of operation, Whitehead’s lab works with 16 tribes in the southeastern portion of Alaska — the region that consistently experiences the highest levels of PSP toxin — analyzing shellfish from beaches that those tribes frequently fish. The initiative, called Southeast Alaska Tribal Ocean Research (SEATOR), has blossomed into Alaska’s first coordinated effort to date to help launch and streamline testing efforts. The program keeps track of shellfish data from 42 beaches across Southeast Alaska, including the ones in Kodiak. As of February, however, many of those sites had no recent data to report.

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