I bet there's someone on here who knows way more about this than me. Come out of your "shell"! 'Til then I'm taking the oyster beat. A brainless animal eaten alive and whole? wtf? Decided to learn:
  1. Pacific
    By far the most commonly farmed, and almost all oysters are farmed, so: most oysters are this. You can spot Pacific oysters because they usually have a black fringe or mantle around the edge of their body. Sometimes said to be "creamy." I dunno -- let me be clear here, I think as food oysters are kind of gross. Just find them fascinating. Most oysters from British Columbia, Washington, Oregon and California are Pacific. Crassostrea gigas is their science name.
  2. Atlantic/Eastern
    From the North American Atlantic (although sometimes farmed on the West Coast, as far as I can tell as a novelty or like a marketing stunt?) Oysters from Prince Edward Island, Nova Scotia, Massachusetts, Connecticut, Long Island, Virginia, Maryland are Eastern, also called Atlantic. Most of the oysters in New Orleans, the gulf coast are eastern. Bluepoints, Wellfleets, Chincoteague are Eastern. Supposedly the best for cooking for some reason. Crassostrea virginica.
  3. Kumamoto
    Native to Japan, now farmed all over the North American west coast. Shells are sometimes deeper, like you could do a shot out of them. Cassastrea sikamea.
  4. Olympia
    Rare. Tiny. Once abundant in Puget Sound, now almost gone. Not often farmed. Myself, I've never seen them in LA in six months of half-looking.
  5. European/Belon
    A whole other genus than these other oysters, whatever the fuck that means. Rare in the US, but if you hear about oysters in Europe before 1950, this is probably what they're talking about (these days most oysters farmed in Europe are Pacifics). Flatter than the others. They're said to have a coppery taste like sucking on a penny. Found them once at Connie & Ted's in LA. I dunno, I've never sucked on a penny, but they were slightly more gross. Ostrea edulis is the science.
  6. Triplioid science oysters
    I guess this is a subcategory of Pacific and Atlantic (for now) You know how there's two chromosomes, like XX, XY? This has three. A genetically modified oyster that's sterile, so it grows extra fast, big and doesn't get disgusting during its reproduction time (summer). These days, far as I can tell, most farmed oysters - so most oysters - are triploids. But here I am well beyond my understanding. To even get triploids you first make tetraploids?Oyster sexuality is wack. They switch "gender."
  7. Whole other deal in Australia.
    As usual with animals. But who cares. Go there if you want to eat a "southern mud oyster." Or New Zealand (or Chile) if you want a "dredge oyster." Good oysters come from the north half of Earth, at places where cold fresh water meets salt water.
  8. The "oysters" pearls come from are a different thing
    They're clams, actually, apparently, if you want to be a dick about it.
  9. There's also a Chinese oyster
    C. ariakensis. Don't know much about this except they're working on farming it in the Chesapeake, though it's been suggested that's a disastrous idea and they'll overrun everything.
  10. Defunct: Portuguese oyster
    Man, oysters just can't stop being interesting. This used to be a type but it's basically been wiped out by disease. But get this: science tells us the Portuguese oyster was actually some kind of relative of the Pacific, introduced to the waters of Portugal via ships in the 16th century! Anyway, unlikely you'll see these.
  11. There's other species.
    It's a whole scene, there are just the food ones.