Oysters, classified as bivalve mollusks, are a popular delicacy enjoyed globally, but the question of how many kinds exist is more complex than a simple number. While there are hundreds of oyster species worldwide, only a small fraction are cultivated or harvested for human consumption. The true answer depends on whether you are counting the biological species or the commercial names used on restaurant menus. The vast majority of all commercially available oysters fall into just a handful of distinct species, each with unique biological traits and origins.
The World’s Major Edible Oyster Species
The global oyster market is dominated by four main biological species, with a fifth species playing a smaller, but significant, role in North America. The most widespread is the Pacific oyster, Magallana gigas (or Crassostrea gigas). Originating in Asia, it accounts for the bulk of worldwide production due to its hardiness and fast growth rate. This species was introduced to the West Coast of North America and Europe in the 20th century, where it quickly became established.
North America’s native oyster is the Eastern oyster, Crassostrea virginica, which thrives along the Atlantic coast from Canada down to the Gulf of Mexico. This species has a long, teardrop-shaped shell and is the traditional oyster of the East Coast. In Europe, the native species is the European Flat oyster, Ostrea edulis, which is historically significant and is often referred to as the Belon, after a river in France.
The smaller Kumamoto oyster, Magallana sikamea, originated in the Kumamoto Bay area of Japan. While closely related to the Pacific oyster, it is valued for its small size and deep cup. A final notable species, the Olympia oyster, Ostrea lurida, is the only oyster truly native to the West Coast of the United States, though its population remains small compared to the introduced Pacific species.
Understanding Regional and Commercial Naming
The complexity in counting oyster “types” arises because a single biological species can be marketed under dozens of different names. This naming convention is based on the concept of merroir, the aquatic equivalent of terroir in wine, referring to the influence of the environment on the final product. The specific body of water an oyster is grown in—including its salinity, water temperature, and available plankton—directly shapes its flavor profile.
For example, the Eastern oyster, Crassostrea virginica, is sold under names like Bluepoint, Wellfleet, and Malpeque. Although they are all genetically the same species, the distinct conditions of their respective bays and estuaries cause them to develop unique tastes and shell characteristics. The Pacific oyster is marketed as names such as Shigoku, Kusshi, and Hama Hama when grown in different West Coast locations.
These commercial names serve as appellations, informing the consumer about the oyster’s provenance and the resulting sensory experience, rather than its genetics. A restaurant menu listing thirty “varieties” is actually presenting thirty different growing locations for perhaps only three or four biological species. The method of cultivation also contributes to the final texture and shell shape, further multiplying the commercial names.
Key Differences in Flavor and Appearance
The major oyster species can be distinguished by differences in their flavor, texture, and shell morphology. Pacific oysters are known for a sweet and creamy flavor profile, often with notes of cucumber or melon. Their shells are typically ruffled, large, and irregularly shaped. The Kumamoto oyster is prized for its intense sweetness, clean finish, and a distinctively small, deep, cup-like shell.
In contrast, the Eastern oyster offers a higher brine content, resulting in a pronounced salty flavor often described as biting into the sea. This species is characterized by a smooth, teardrop or crescent-shaped shell that is thicker than the Pacific variety. The European Flat oyster, or Belon, presents a unique, savory, and intense metallic or copper-like finish. Its shell is notably flat and round, unlike the deep cups of the other major species.