Eastern oysters offer an environmental value? One oyster can filter up to 48 gallons of water in 24 hours! Unlike Pacific oysters, which are mostly cultivated, Eastern oysters are harvested mainly from wild beds in the Gulf of Mexico, Long Island Sound and parts of Atlantic Canada. All oysters vary in taste depending on where they are from, due to differences in water nutrients, salinity levels, temperature, and more. Average market size of this shellfish is three to four inches, and they are harvested in shallow saltwater.