Oysters are exotic, bizarre, sexy, provocative. No matter how you feel about them, there’s a good chance they compel you to ask a question or two.

I don’t know about you guys, but I Google a lot of weird stuff. Sometimes, a simple answer comes up immediately. Other times, not so much. I thought it might be helpful to provide some straightforward (and caveated) answers to all of your most wondered-about oyster queries. So when the next time when someone asks about oysters, you can drop some impressive knowledge on them.

Oh, and don’t forget the basics. That’s what the Oyster 101 is here for!

Disclaimer: a few might be a little “TMI” for the casual oyster eater, so uhhh please read with caution. Ignorance can be bliss!


What do oysters eat?


Oysters eat phytoplankton or small bits of algae suspended in the water. They are filter feeders, which means that they obtain their food by filtering water in and over their gills. Adult Virginica oysters can filter up to 50 gallons of water per day. Sometimes they’re referred to as bottom feeders or detritivores, but don’t turn your nose up at them because of that.

To demonstrate their fascinating ability, here is a time-lapse of oysters in filtering action.


So now you’re probably thinking… if oysters are equal opportunity eaters, and they’re in water that’s full of “nutrients,” thennnn aren’t we just all eating crap?

Well, that is why you still can’t order New York Harbor oysters right now, and also why we seriously need to protect our waters from becoming even more mucked up. The Clean Water Act has really helped improve water quality in New York Harbor and elsewhere in the U.S., but we’ve still got a long way to go.

Oysters are voracious vegetarians, but fairly picky about what they nosh on. Despite the absence of a brain, oysters “know” what they can and cannot digest. Bob Rheault, Executive Director of the East Coast Shellfish Growers Association elaborates, “Even as a dust-speck sized larvae they do this. The oyster sorts identically-sized algal particles (say Isochrysis and Chlorella) with 90% efficiency, even when mixed with a soup of thick silt. The Isochrysis goes into the gut and the Chlorella and silt goes into the pseudofeces (rendering it bright green!). I have done this with radiotracers and the degree of efficiency is remarkable. It is one reason why the American oyster is so adaptable and can survive in high silt loaded waters while many other organisms struggle and suffocate with fouled gills.”


Knowing that oysters taste like where they’re from—everything in the environment has an impact—my continuing question is just how do specific algaes or water composition affect the taste, and is there a science-based way to measure it? If you’re working on this type of research, please get in touch with me!!

Do oysters poop?


Yes, yes they do. Oysters expel both real poop AND pseudofeces, which are particles of non-food things in their food.


See Erin Byers Murray, author of “Shucked: Life on a New England Oyster Farm,” blog post about it.


When you Google “oysters” and “poop” together, the conversation takes on a depressingly misinformed, ignorant, fearful form. Some particularly one-sided, skewed articles by fairly prominent publications aren’t helping the cause. I mean, can someone just register oysterpoop.com and clear the air about the whole subject of oysters and foodborne illness? It happens, but it doesn’t happen nearly as much as it does with other stuff we eat. I just don’t understand why the same people who cringe at raw oysters are happily scarfing down mystery meat from sketchy fast food joints.

Still Life with Fruit, Oysters, and Wine by Everhart Kuhn, ca. 1865 (source:  Smithsonian Magazine ).

Still Life with Fruit, Oysters, and Wine by Everhart Kuhn, ca. 1865 (source: Smithsonian Magazine).

Are oysters aphrodisiacs?


Probably not. There is limited scientific evidence that supports this claim, but what we lack in science-based data, we humans love to fill in with anecdotal truth! Basically, if eating a dozen oysters get you in the mood, then just call it a win.

How did oysters get such an amorous reputation? Blame the Romans, Casanova (who claimed to eat 50 oysters for breakfast every day and swore they were the reason for his world-famous libido), King Henry the IV, and cliché oyster marketing.

Oysters do contain a pretty high amount of zinc and other great nutrients (vitamin B12, thiamin, riboflavin, niacin, vitamins C, D, and E, iron, magnesium, and selenium), which are important in reproductive development and overall health. A study published in 2005 found two amino acids, D-aspartic acid (D-Asp) and N-methyl-D-aspartate (NMDA), in shellfish, like oysters, that were shown—at least in animals—to increase testosterone production. So there is that.

But to cite WebMD’s great post about aphrodisiacs, “No food has been scientifically proven to stimulate the human sex organs. But foods and the act of eating can suggest sex to the mind, which in turn can help stimulate desire in the body.”


Many of us probably unknowingly was introduced to the term aphrodisiac in grade school while studying Greek mythology. The word is derived from Aphrodite, the Greek goddess of sexual love and beauty. Sidebar: the Greek word aphros means “foam,” and Hesiod relates in his Theogony that Aphrodite was born from the white foam produced by the severed genitals of Uranus (Heaven), after his son Cronus threw them into the sea. Lovely.


Why is my oyster green?


If you come across an oyster with green-tinted gills, like the ones as shown above, consider yourself lucky. The greenish color comes from a particular type of blue diatom that the oysters are eating. It’s not harmful to eat an oyster like this, and in fact, its flavor is highly sought after. In France, the “verte” oysters are considered to be a delicacy and demand a higher price than its “blanc” counterparts. You can also find them in US at random, but more frequently in the winter when the blue diatoms are more abundant.


Oysters with green gills tend to be hyped as a “rare specialty” and marked up in price accordingly. Don’t fall for it.


According to a research study published in May 2014, scientists have proposed that the blue pigment, known as marennine, has been found to have powerful antioxidant, antibacterial and antiviral properties. Perhaps the green oyster is our super sexy superfood?

Mount Desert Island Oyster.  See post .

Mount Desert Island Oyster. See post.

Are oysters still alive when I eat them?


You don’t want to eat a dead oyster, raw. Ideally, oysters should be kept alive right up until the moment just before consumption. The heart is right next to the bottom adductor muscle, so in most cases, separating the meat from the shell kills it.

That said, eating dead oysters isn’t necessarily going to make you sick. But from the moment anything dies, it begins to decompose. A few hours isn’t going to do anything. A few days? Eh, I’ll pass.


A living, unshucked oyster will be fully closed up, like a rock. Can’t blame it for working hard to avoid becoming your dinner. If the bill of the oyster gapes open and doesn’t close with a few taps, it’s probably dead (or it might be really cold and sleepy… so give it a minute if you just pulled them out of the fridge). If you bought a bag of freshly harvested oysters and some are dead, they could still be cooked and enjoyed. Just throw them on the grill or fry them up. Masterful shuckers will toss out the dead ones long before they reach your platter. Sometimes, I will poke at the outer edges of the mantle with a fork tong to see just how “lively” they still are.

Some oyster nerds at Business Insider were fascinated by this and decided to create a video:

Random trivia: the French take quality assurance to the next level by leaving the bottom adductor muscle attached. This allows you to experience the freshest, most alive oyster as possible… but prepared to do some work (and get silently judged on it).


Do oysters feel pain?


It’s still up for debate. We don’t really know. Some say no while others say yes. From an anatomical standpoint, oysters do not have a brain or a central nervous system, so it is not likely that they would experience the world in the same way that other animals do. That said, it is unclear whether or not you need a brain in order to “feel” or process pain.

I asked Guinness World Record Oyster Shucker and restaurateur Patrick McMurray for his thoughts. “My belief—as I am not a scientist—is that oysters feel pain as much as plants feel pain. Pain is a perceived sense to us. Oysters do not have sensory perception or ability to sense. Oysters react— close when touched, use cilia to move food particles etc. Some plants react the same way—flowers open and close, Venus Flytrap per se.”


This question seems to be at the crux of another question: “Are oysters ok for vegans to eat?” I’m not a vegan, so I don’t really have an opinion on this. But I really appreciate the dual-sided argument that the Unnatural Vegan brings to the table.

How can you tell if an oyster has gone bad?


Have you guys heard of the egg test (good eggs sink, bad eggs float)? I wish there were something as simple as that to gauge the quality of an oyster. There is no straightforward way to tell, but you can train your senses to pick up red flags. I asked my favorite SF Oyster Nerd, Greg Babinecz to take a crack at this one in a few sentences. Greg, true to his oyster-nerdy-nature, couldn’t help but submit a comprehensive perspective on the matter.


  1. If it’s open and does not close to the touch, throw it away*.

  2. If it smells strongly sulfuric or rotten, throw it away.

  3. If it is very dry and has no juiciness to it, throw it away*.

*or compost.


Smell: Anything slightly afoul to your innate sense of what smells right, I would say is best to avoid. There are oysters that are inherently a little “funky,” and are prized as such. But anything that strongly smells of rotten eggs, petrol, or fish tank gravel, just light a match and toss it in the trash (outdoor trash, preferably).  Some oysters will have unique “low tide” or metallic smells and are good, but those are rare and if you’re seeking those out, you’re probably not a novice shucker.

Look: A good oyster looks plump, juicy, and has a glistening sheen to it.  It simply looks fresh.  Quite often you’ll open an oyster and it will have a dried out, Jackson Pollock-esque splatter look to it.  If they still smell okay, they aren’t necessarily bad, they just aren’t good. Best use them for fried or BBQed oysters, or simply discard.

Taste: Several oysters I’ve shucked have passed the previous two tests, but then just taste like they’re spoiled. It will look great, smell fine, but upon consumption, taste terrible.  And there is a discernible difference between a strongly flavored oyster and a bad one.  Copper, musky, and even low tide flavors don’t mean it’s bad.  A very noticeable lack of salinity and a sulfuric-gaseous pop once bitten and you’ll immediately know it’s bad.  These rogue goblin oysters are the bane of many shuckers around the world.

Lastly, shell inspection: This should come first, but not without understanding smell and look.  A good rule for any bivalve is that if its shell is cracked, has holes, or is open and will not close to the touch, it’s best to avoid (mussels and scallops are kind of an exception).  An open bill that will not close to the touch usually indicates the oyster is dead.  All oysters should be alive right before consumption, and eating a dead one can be dangerous (see #4). Even if it smells and looks fine, but was open, I’d say best to avoid.  I’ve certainly gambled on some open bivalves before and been okay, but it’s best to play it safe.  But hey, it’s your stomach and your dice to roll.


There’s a tiny crab in my oyster… is that normal??


“Sure it’s normal; it’s called a pea crab and lives her entire life inside the oyster. The crab doesn’t hurt the oyster and it won’t hurt you to eat both. In fact it’s good luck to eat the pea crab. Enjoy!” That’s reassurance from Chris Ludford, grower of Pleasure House Oysters and full-time fire boat captain for Virginia Beach.

If you shuck your own oysters, you’ll probably encounter one or two. Raw bar shuckers will most likely remove them for you before you even see them.


Not much. Salty like the sea, and the texture is like kind of like alfalfa sprouts. If eating them alive makes you squeamish, then pan fry them up with a dash of Old Bay.


In my experience, pea crabs are most common in Eastern oysters from brackish water. In fact, I only recall seeing them in oysters from the Long Island Sound and inlets along the Chesapeake Bay. That doesn’t mean they’re not elsewhere though! 

Random fact: male pea crabs will move from oyster to oyster to do “house calls,” while the ladies stay put.

There’s a creepy looking worm in my oyster… is that normal??


Every time I hang out with a buddy of mine from LA (who’s not an oyster fan, but we get along anyway), he never fails to tell his story about that one time when he encountered a massive, horrendously large worm in his oyster, “like it was Dune or something.” It’s a disturbing visual and pretty unappetizing. Fortunately, it’s not abnormal or alien. That said, I don’t take photos of oyster worms so I’m sharing a photo from the Eastern Shore to help relax you instead.

If you don’t want to take my word for it, here’s oyster farmer Matt Gregg of Forty North Oyster Farms, who has encountered his fair share of weirdness, on the subject: “Oysters can be the perfect host for many tiny marine invertebrates, none of which, to my knowledge are harmful to humans. Oysters that grow in muddy and lower salinity environments tend to harbor an organism called a bloodworm. If you’re squeamish (most oyster eaters are not), stick to ocean-grown oysters. Bloodworms can’t survive those conditions.”


Can you recycle oyster shells?


In most cases around the country, the shells that we leave behind at the raw bar go straight into the garbage, which is truly a damn shame. Oyster shells can be recycled and repurposed for a number of things such as chicken feed boostergarden fertilizerwedding decor, and most notably, as the perfect substrate for baby oysters to grow on. Unfortunately, running a shell collection program is logistically challenging and pretty expensive. The opportunity cost? One seaside village in China has put a reclaimed value of approximately $3200 USD per ton of shell (for fertilizer and construction material.) That number would certainly be higher if you considered its restorative value back into our environment.


The symbiotic relationship between a traditional oyster planter and the oyster shucking house creates a closed loop system. The shells return to the oyster farmer as the base for the next crop. But demand is starting to swing in favor of half shell consumption, which means we’re still running on a national shell deficit.


Oyster shell collection and oyster restoration initiatives have been building momentum around the country, such as along the Chesapeake and the Gulf. I’m personally rooting for NYC’s own oyster restoration & education program. Pete Malinowski, Executive Director of Billion Oyster Project explains:

“The vast majority of oyster shells generated in New York City’s restaurants are packed into plastic bags and driven to points South to be landfilled. At Billion Oyster Project, we need oyster shells for our restoration projects and work hard to recover as many as we can from restaurants. Right now, we are collecting shells from 45 restaurants four days per week. We average over one ton of shell per day and are on track to collect 210 tons this year. The shells spend one year curing at the NRG Arthur Kill Power Plant in Staten Island. Once cured, we place the shells in tanks with oyster larvae. The larvae set on the shells creating the clusters of oysters we use for reef building.”