Oyster Species
Just like with any critter, an oyster's genetics play a huge role in how it looks and grows. Of course, over the course of an oyster's development, many other variables come into play - what kind of food did it eat, was it crowded as it grew, was it grown on the beach or higher up in the water column etc. We'll get to those factors in other blog posts.
But when you're eating a new oyster, we always recommend first going back to basics: what species is it?
This post outlines the five species that you're likely to find for sale in restaurants, online stores, and retail stores in the United States.
Two species, the Pacific and the Virginica, dominate: The Pacific on the West Coast, and the Virginica on the East Coast. They meet in the middle, in a zig zaggy transitional zone determined by the cost of transporting the oysters from farms to restaurants, where some of the country's most interesting and unpredictable raw bars flourish. Be sure to lookup a good raw bar if you're ever in Denver or St. Paul.
Then, there are two other species that are fairly common on the West Coast - the Olympia and the Kumamoto.
Finally, if you're lucky, you might find a European Flat for sale, usually around Christmas, and usually on the East Coast.
So, we'll start with those 5!
The five species commonly found on menus in the U.S., photographed by Jim Henkins. Caveat - in this photo, some of these oysters are smaller (or larger) than they usually appear in the marketplace.
Pacific Oysters
We're West Coasters, so we'll start with with Pacifics.
Pacifcs make up the vast majority of the oysters grown, sold, and served on the West Coast. Shibumi, Shigoku, Kusshi, Chelsea Gem, Blue Pool, Hama Hama, Baywater Sweet, Hog Island Sweetwater, Lucky Penny, etc.. these are all varieties or brand names of Pacific oysters, grown in various places by various oyster companies. It is safe to assume that if you're eating oysters anywhere from Anchorage to Los Angeles, and the restaurant, farm, or retail store isn't making a big deal about what species the oysters are - they're Pacifics.
Pacifics are native to Japan, and were introduced to the PNW in the early part of the 20th century by enterprising Japanese immigrants looking for an oyster to replace the dwindling supply of native Olympia oysters. (See below!) The oysters ended up loving the West Coast, and have since naturalized throughout much of the region, especially in Hood Canal (where we farm!).
Pacifics are easy to grow, tolerant of a wide variety of environmental conditions, and have a long shelf life, so they're usually the go-to oyster for commercial operations worldwide (although notably, not on the East Coast of the United States).
Five years ago, we would have said their scientific name is Crassostrea gigas... but there's an effort underway to rename them Magallena gigas. This is not without controversy in the scientific community. We'll just wait until the dust settles and then do what we're told because honestly, would the oysters, by any other name, taste as sweet and salty? Yes. Yes they would.
Flavor:
Pacifics are here to surprise and delight. They have a wide range of flavor possibilities and can be earthy, fruity, buttery, sweet, or coppery depending on how and where they were grown, as well as the season. (More on those factors later!) In general though - they're sweeter and fruitier than most of the other species except their close cousin, the Kumamoto.
Appearance & Size
Growing conditions play a big role in their appearance and shape. Pacifics can be rounded, long and slender, or flat. If protected from wave action, their shells are fluted, frilly, and deep cupped. When tumbled, Pacifics can be as round and smooth as a golf ball cut in half.
Pacifics will grow extremely large if given the chance, but they're usually harvested at around 2 to 3 inches.
Other Notable Facts:
Pacifics start out as male, and become female after a few years. They are extremely fecund, and take a "go big or go home" approach to reproduction: a female oyster can produce something like 90 million eggs in a single year. They are broadcast spawners, and larvae swim around in the water column for about two weeks before settling down and becoming sedentary. Typically all the Pacifics in a reef or bed will spawn at the same time, which can turn the surrounding seawater milky white.
Kumamoto
Kumamotos (Crassostrea or Magallena sikamea) are closely related to the Pacific oyster, but they haven't naturalized in the US and are much harder to find. They're very popular oysters - so the rarity is mainly due to lack of seed supply rather than lack of demand. But they're also slow growing and require a specialized habitat. They don't grow well at our farm in Hood Canal, so we grow our Kumos (aka our Hamamotos) in South Puget Sound. (We think this has to do with food availability - there's more algae in South Puget Sound than Hood Canal - but we're not 100% sure.)
Flavor:
Kumos are here to please. They're considered a beginner oyster due to their consistently sweet, mild and fruity flavor. They're more predictable than Pacifics, whose flavor can vary widely depending on growing conditions.
Appearance & Size:
They're not as spectacularly frilly as Pacifics. Instead, their shells are wavier, with more pronounced ridges on their cupped shells, and a few more ruffles on their top shells. They're naturally deep cupped and petite, so farmers don't bother to tumble them. If you work with oysters, or eat them regularly, you should have no problem telling a Kumo from a Pacific... but don't feel bad if you get them mixed up. They are, after all, close family relatives.
Other Notable Facts:
Kumos and Pacifics can interbreed, creating a Frankenstein known as a Gigamoto. Once the two genomes intermingled scientists had trouble keeping them separate, so it's possible that most of the Kumos we farm on the West Coast are some kind of hybrid. (This is why you'll occasionally see Kumos marketed as "100% pure" Kumamoto oysters, meaning they don't have any Pacific ancestry.)
Olympia
Our native oyster, Olympias, aka Ostrea lurida, were once common up and down the West Coast, from Northern Baja to Southern BC. They were an important food source for Indigenous peoples, and, especially in lower areas of the beaches, would have played an essential role in the nearshore ecology, forming reefs, filtering water, and providing habitat.
As Europeans moved to the West Coast in the 20th century, the Olympias fell victim to over harvesting (they were a prized food during the San Francisco gold rush) and pollution (the pulp mills were no bueno for the oysters). They are called "Olympias" because the last remaining commercial beds were located in South Puget Sound, near the city of Olympia. (The boat voyage north through the Straits of Juan de Fuca and south down to San Francisco was just a bit too long for the oysters to survive, so the Puget Sound oyster beds, unlike those of Willapa Bay, survived the gold rush oyster-eating bonanza.) Today, they are at an estimated 1% of their former population, and many groups are working hard to recover their population, among them the Puget Sound Restoration Fund.
Oyster farmers (like us!) grow Olympias from seed, but they're still hard to find on the marketplace. For one, seed is hard to source. But more importantly, they're incredibly slow growing and tricky to farm. Where a Pacific oyster can reach market size in 1 to 2 years on the beach, and Olympia will need at least 4. They dislike extreme heat and cold, and so they typically grow in wet areas like the far reaches of the tideflats, on the underside of a pacific cluster, or in a slough or other low lying area. This is great, except that's where all the creepy crawlies live, who like to eat baby oysters for dinner. So there's a huge mortality rate on the seed you buy.
Finally, after all that, they only survive a few days post harvest, so the restaurants need to sell them right away. (Pacifics, which have much stronger adductor muscles to keep their shells tightly closed, can survive for a week or more in a refrigerator).
When you see Olympias on a menu, please order them, and reward the farmer for farming them and the restaurant for buying them - a lot of work went into bringing them to your plate!
Flavor:
Olympia's can be a divisive oyster... you either enjoy them, or you don't. They are famously coppery tasting, and can dry your mouth out a bit when you eat them. Sometimes they have really lovely notes of citrus, and can be nicely grassy, but don't ever expect the fruitiness of a Pacific. Texture wise, because of their nonexistent adductor muscles, they lack the satisfying morsel of scallop-like chewiness that you find with a Pacific.
Appearance & Size
Anecdotally, folks will say Olympias are the size of a half dollar, but frequently they're smaller than that. Their shells are greenish and brownish gold inside, flat on the outside, frequently teardrop-shaped, and have very little fluting. Their scientific name, Ostrea lurida, refers to the reflective quality of their shells.
Other Notable Facts:
Olympias brood their young, meaning the female oyster holds onto the fertilized eggs for a certain amount of time. This reproductive strategy might make them less susceptible to climate change, which can interfere with the ability of larval pacific oysters to form their shells.
Virginica aka Eastern Oyster
Native to the East Coast, from Newfoundland down to the Gulf of Mexico, these tear-drop shaped beauties are the oysters of New York speakeasies and Low Country oyster roasts. When you eat oysters on the East Coast, you're eating Virginicas. They are incredibly prolific, and once formed enormous oyster reefs that interfered with boat traffic in New York harbor and the Chesapeake Bay. To this day, you can visit ancient middens in Maine and stand atop piles of oyster shells that are 2000 feet long and as many years old.
Flavor:
Virginicas are highly variable depending on where they were grown... a Maine oyster is very different from a Gulf Coast oyster... but in general it's safe to say that they are saltier and less fruity tasting than Pacifics. They can be incredibly sweet and buttery tasting. Their texture is usually more hefty and chewier than a Pacific's.
Appearance and Size:
Their shells are less frilly and ruffled than Pacific shells, and more teardrop shaped. Very few farmers on the East Coast tumble their oysters, in part because Virginicas have naturally deep cups. Their new growth is less colorful, but they have bright purple splotches on the insides of their shells, where the adductor muscle attaches.
Other Notable Facts:
After being decimated by a series of disasters (overharvesting, pollution, and disease) the Virginica has seen a tremendous rebound in the last few decades, with oyster farms springing up throughout their growing area. The farms are encouraged by municipalities eager to preserve their working waterfronts and replace dwindling wild capture fisheries, although the transition towards aquaculture has occasionally created user-conflicts with recreational boaters or harvesters used to accessing historically wild reefs.
European Flat
Also known as Belon, after the river in Brittany, France, European Flats are a close relative of the Olympia oyster, but larger and with more personality. European Flats are the oysters of the Romans, the Gauls, and the Irish. They're the reason the French invented mignonette and that people think oysters pair well with stout beer. Ostrea edulis is a sturdy oyster - chewy, strong-flavored, and salty. It is not fruity. It can handle a stout.
This is a legendary oyster - the Ancient Greeks cultivated them on pottery shards, used their shells as voting tokens, and told stories about Aphrodite, their goddess of love, emerging from the sea in an oyster shell. The Romans consumed all their own local wild oysters, and so continued to develop farming methods while also importing oysters from their conquered territory in Gaul and Britain. These are the oysters painted by Renaissance artists and eaten by Casanova, who reportedly at 50 for breakfast every day.
Look sharp, because you can occasionally find them for sale in the United States. Back before the movement of oysters from one spot to another was regulated, farmers introduced European Flats to Maine, where they naturalized in the Damariscotta River, and to the West Coast, where they survived in both Westcott Bay (San Juan Islands), and Tamales Bay (near San Francisco). Hog Island Oyster Company sells a European Flat as the "French Hog," usually around the holiday season.
If you're ever eating oysters in Paris, look for them sold as "huitres plates." (The French are some of the world's largest growers and eaters of Pacifics, aka "huitres creuses" so most of the oysters on display on the streets of Paris are Pacifics.)
Wherever you find them for sale, don't be surprised if they're banded shut with a rubber band. Like their smaller cousin the Olympia, they don't have the musculature to hold their shells shut for very long after harvest. The rubber bands keep their shells closed and extend their shelf life.
Other Species to Watch Out For:
New Zealand Flat: aka Ostrea chilensis or New Zealand Bluff oyster, this oyster, strangely enough, is native to both New Zealand and Chile. Closely related to Olympias and European Flats, they're flat, small, and strong. The only one we've eaten had a bright green interior shell and was frankly a bit pungent tasting. (It was probably a few days past prime, so more research is needed.) Raw bars in southern California are starting to import them during the summertime when west coast supply is scarce... look for them under the trade name Kiwa.
Keep your eyes peeled as you travel internationally and you might find other species, such as the Sydney Rock Oyster, which is native to Australia, the Indian Backwater Oyster which is native to India and Sri Lanka, or the Gaspar Cupped Oyster, native to Senegal and Gambia. If you find an unusual oyster, take a picture, and let us know what you thought of it!
Read More!
About Oysters in General:
The Essential Oyster: A Salty Appreciation of Taste and Temptation by Rowan Jacobsen.
Oysters, a Gastronomic History by Drew Smith. This book makes the amazing claim that Ostrea chilenses traveled between Chile and New Zealand via volcanic eruption. Sure seems like floating debris or ocean-traveling humans was a more likely conduit. But, we're just farmers!
About Olympias:
The Living Shore by Rowan Jacobsen
Katie Gale: A Coast Salish Woman's Life on Oyster Bay, by Llynn de Danaan
About Virginicas:
The Big Oyster: History on the Half Shell by Mark Kurlansky