The European flat oyster, Ostrea edulis, a native of Europe, occurs naturally from Norway to Morocco in the North-Eastern Atlantic and in the whole Mediterranean Basin. Natural populations are also observed in eastern North America, from Maine to Rhode Island, following intentional introductions in the 1940s and 1950s (MacKenzie et al. 1997). Cultivation and collection using Shellfish Raft Spat Collectors, Tray Racks / Overwintering Cage (Maine DMR).

Since the discovery of natural beds in the 1980´s, considerable interest has developed in the commercial harvesting of these oysters. Unfortunately, very little is known about these natural populations that appear to be unique along the Eastern coast of the United States (Heinig 1984, Vercaemer et al. 2006).

The European oyster was imported to Maine in the 1950s for aquaculture. It is believed to have escaped from the former Salem Harbor marine aquaculture facility in Massachusetts during the 1980s. A 1997 survey revealed dense concentrations of O. edulis in Salem Harbor, Danvers River, and Manchester Bay (Salem Sound), Massachusetts. Lower densities were observed north to Cape Ann and south to Boston Harbor. O. edulis continue to be harvested in Casco Bay, Maine, while all shellfish harvesting for human consumption is prohibited in Salem Sound. In the Northeast, O. edulis appears to occupy a different niche than the native oyster population, and it is yet to be determined if there are ecological impacts (MacKenzie et al. 1997).