European oysters or just flat oysters have for many years not been part of the fauna in the Danish waters, except for the western_cc781905-5cde-3194-bb3b-136bad5cf5cf where the Limfjord entered after the breakthrough of the Agger Strait in 1825. Therefore also better known under the name "Limfjordsøsters".
It has actually been here for thousands of years and has been an important part of the diet right back to the Stone Age. The Danish flat oyster was widespread in most fjords completely to the western part of the Baltic Sea but has been extinct for approx. 200 years.