As Mark Kurlansky explains in The Big Oyster, all North American East Coast oysters are the same species: Crassostrea virginica. That means that the ones of Prince Edward Island, Wellfleet, Long Island, the Chesapeake and Louisiana are, Linnaeus-wise, the same. For connoisseurs, though, the differences are vast, and all point to the individual qualities of the waters in which the bivalves are raised.
“Merroir” (taken from the winemaking term terroir) is the flavor in oysters that expresses qualities of the water in a particular location. Those unique flavors come from variations in temperature, salinity and type and quantity of available nutrients (algae, phytoplankton and zooplankton). This is why wordy diners who were raised eating, say, the slow-growing, briny, three-inch oysters of cold water Maine sometimes quail when faced with the massive, bland ones that grow quickly in the warm waters of the Gulf of Mexico. They look and taste alarmingly different.
Another huge variability comes with how the oysters were raised. New York City’s first oysters were wild, growing in jumbled clusters that might randomly yield fingernail-sized, gnarled, banana-shaped and hand-sized variants. Their shells were likely thick, pitted, brittle, barnacled and scarred by calcareous worm tubes, not that anyone minded.
In contrast, modern farmed oysters are not allowed to form reefs; they grow in containers suspended by floats above a bay floor and are regularly handled. Mechanically tumbling these mollusks diminishes shell brittleness; it also helps their shell develop a deeper belly to hold brine. Farmed oysters are seeded and harvested at regular intervals, so they grow in marketable uniformity. It would be tough to count and price a dozen oysters pried from a reef.
Crassostrea virginica thrives in relatively warm, brackish waters in intertidal and subtidal areas that are fed by freshwater rivers rich with organic matter. The Hudson estuary surrounding the island of Manhattan and lowing out to the sea was, essentially, Crassostrea heaven.