And on days the ocean cooperates, mussels seem like the most manageable kind of seafood. They come alive and briny, politely packaged in something like their own armor. But on the days when the sea doesn’t behave, when harmful algal blooms (HABs) flare and shellfish quietly start to concentrate toxins, mussels are among the most tightly policed food in America.
If you want to know why, don’t go back to the dock. You begin with the thresholds, those figures that make schools close and supply chains reroute and determine whether a coastal town has a decent weekend or a long, nervous summer.
The Numbers That Take Beaches Home (and Save Lives)
Washington state imposes paralytic shellfish poisoning (PSP) closures based on test results that, in general, have more than 80 micrograms PSP per 100 grams of shellfish tissue, but those numbers can spike quickly. A press release by Skagit County issued for the closures in July 2024 reported that mussel samples from several locations, including Penn Cove, had over 270 micrograms PSP/100g.
There are two things that make these events especially disruptive:
Cooking doesn’t fix it. Cooking and freezing do not kill PSP and other biotoxins, the Skagit County notice said.
Closures don’t lift on vibes. The fish and wildlife agency of Oregon explains harvest closures upon highs exceeding alert levels and states that those alert levels are 80 µg/100g for PSP and 20 ppm for domoic acid, both with a margin of safety.
Those numbers aren’t random. As directed by NSSP, harvest areas must be closed when levels of domoic acid reach 20 ppm or more in the edible portion of raw shellfish. And in a separate section of NSSP guidance, there are closure triggers above 5,000 cell/L (a red flag level for neurotoxic shellfish poisoning risk along affected coastlines).
So the first big insight is this: shellfish safety is a story about measurement. And in a HAB year, the readings have the power to determine the entire market.
Habs, Simplified: Why Mussels Are the ‘Canaries of the Sea’
Mussels are filter feeders. That’s also partly why they’re seen as lower-impact protein, and part of why they can be sponges for what’s going on in the water column.
The review of perch harmful algal bloom, published as a peer-reviewed journal article in Washington D.C., found more frequent toxic blooms and the growing risk to shellfish access and public health in the state. The HAB overview from Washington Sea Grant has some of the key offender species that matter there, such as Alexandrium and Pseudo-nitzschia (or both).subseteqAlexandrium/par = PSP) and chaetoceros (DA-C) are some of those in the region moving: alexandrium, pseudo nitschia Alexa parva cHt Deadly habs.org doc.
Public health agencies interpret that ecology into routine monitoring and closings. A science review conducted by the Encyclopedia of Puget Sound notes that Washington’s Department of Health tests for biotoxins among both commercial and recreational shellfish areas (it can close an area when lab results come back showing high levels).
Or put another way: When there’s a bloom, the mussels are out of luck. They test clean or they do not move.
Under the Microscope: What Testing Is Really Like
The term biotoxin testing tends to get waved around as a way of reassuring. But what does that, you know, actually mean?
In the public realm, that typically involves periodic sampling and laboratory analysis of shellfish tissue, as well as growing use of phytoplankton monitoring as an early indicator.
In the Pacific Northwest, for example, the Olympic Region Harmful Algal Blooms (ORHAB) Partnership was born in June 1999, when marine biotoxin-related “seemingly random” closures of coastlines (from paralytic shellfish toxins and domoic acid) spurred eight tribes to form a partnership.
The Pacific Northwest HAB Bulletin (the result of regional ocean observing efforts) is clear about what it is and isn’t. It points out that closures are made by state agencies and coastal treaty tribes after the toxin concentrations in shellfish samples collected at each beach has been tested, not from the bulletin itself. It also provides some insight on supplementary sampling with an Environmental Sample Processor which was moored off La Push, WA in late spring and late summer.
In Washington, meanwhile, the state’s Department of Health operates a Shellfish Safety Map and hotline — for closures because as they say “biotoxin levels change frequently.”
If this seems a lot, it is. But that’s the thing: in a HAB year, “safe mussels” are the outcome of a system, not an individual test.
Where Pacific Seafood Fits in: Getting Ahead of Closures Without Cheating the System
Pacific’s mussel sourcing page reads like a hushed hedging of ocean volatility; New Zealand-grown greenshell mussels, as well as blue mussels from Maine or Prince Edward Island and Mediterranean ones from Washington State. That absence of geographic focus is more than simple culinary variety, it’s bastion presence. If one area is in cycle of closures, supply can move around.
Then there’s Penn Cove Shellfish, the Washington-based farm brand in Pacific’s stable. On Pacific’s Penn Cove brand page, the company says Penn Cove Farms raises and harvest three million pounds of mussels every year from two mussel farms in Washington: Penn Cove on Whidbey Island and Quilcene Bay in the upper Hood Canal.
When HABs do hit, those numbers don’t infer that mussels keep coming in at the same rate without interruption; but they do illustrate what’s at risk: much of a robust, domestic supply that relies on clean test results and open-water classifications.
The Penn Cove safety page itself lays bare the regulatory reality: certified shellfish growing areas are monitored by State Health Agencies for hazards, which includes but is not limited to marine biotoxins, and proper tagging is a must. It also refers to the Federal Shellfish Tagging Program as a control measure to avoid moving shellfish found in an unsafe area into commerce.
So how, exactly, are “harvest windows” planned?
1) You Think: With, Not Around the Closure System
In a HAB world, harvest timing agencies can give only contingency answers: open categories and recent tissue results and killer phytoplankton must factor into whether there is even a window to work with. NSSP guidance emphasizes that marine biotoxins are frequently capricious and plans for action are meant to do early warning and rapid response.
2) You Clip Water and Cold Chain duration
When the harvesting window opens, speed is a discipline of quality and safety. Penn Cove claims that orders are harvested, hand packed and shipped within 24 hours of coming out of the water. That doesn’t “solve” toxins — only testing and closures do that — but it does reduce other risks of spoilage and make more likely that the mussels that are legally harvested are in prime condition.
3) You Mix it Up in Terms of Formats and Origins
Pacific’s multi-origin mussel offering (New Zealand / ME or PEI / Washington) is a pragmatic hedge; when West Coast closures limit some products, availability can be supplemented with mussels from other regions (assuming those supply chains are equally compliant and inspected).
4) You Create A Culture Of Food-Safety That Doesn’t Flinch During Stress.
Though HAB toxins are “pre-harvest” hazards managed at the “growing area” level, the downstream system still counts: sanitation, training, verification and audit decrease the probability that a bad week becomes even worse.
In its 2024 CSR report, Pacific Seafood says it needs regular environment and pathogen testing based on a sampling plan and that its ready-to-eat products are tested every day, once a week or per month. That CSR report also features some audit results as at 2024 for individual facilities such as SQF “98%” (Galveston Shrimp Company / Warrenton) and SQF “100%” (Phoenix), along with BRC AA+ and BAP 100%, are revealed for specific sites.
Again: those audit scores are not a replacement for biotoxin monitoring. But they indicate a company that is trying to run a high-verification operation all across its product types, which would be exactly what you’d want if the elements are adding more uncertainty.
The Human Factor: Closures Aren’t Just Public Health. They’re Economic and Trust Closures are not just public health — they’re economic, and trust-based
The time PSP surged along parts of the Pacific Northwest in 2024, coverage emphasized scale and anxiety: Oregon expanded its closure area on the coast, and at least 31 people in Oregon were sickened during that episode, according to AP reporting.
The local can be intensely personal: One local paper mentioned months-long Penn Cove and Holmes Harbor bay closures causing damage to the bottom lines of Penn Cove Shellfish because the toxic levels were so high.
This is why the real currency in shellfish is trust: When an agency says “closed” and growers bow to it, they are not only protecting consumers but the integrity of a category. The other is one bad commercial mistake can blot every oyster bar and seafood counter for a season.
What Consumers (And Chefs) Can Do With This Information
If you’re buying commercially harvested mussels from responsibly operating suppliers, then you are relying on the NSSP and state monitoring that exists to keep toxic product out of commerce.
If you’re harvesting for fun, the best thing to do is also the dullest: Keep an eye on the most recent closures before digging or picking. The Shellfish Safety Map and hotline are among many reasons Washington DOH releases them: Conditions can change in an instant.
And if you’re a restaurant, the safety narrative is procurement discipline: demand legitimate tags, purchase from reputable sources and treat we know our grower as an idea that needs compliance, not a vibe.
