Oysters have always been in the Wadden Sea.

Especially in the 17th century, oysters were popular with Danish kings and Holstein dukes. King Frederik III. of Denmark lent the isles under the Diocese of Ribe along with all the royal sand banks to field marshal Schak. Later on, the sand banks were returned and the oysters were partly used as means of payment. 13 priests in Tønder as well as on Fanø, Rømø, Sylt and Amrum received 1,000 oysters to include the oystering into their public prayers.

Three factors are assumed to have caused the extinction of the original Wadden Sea oysters.
The first factor is the over-oystering of Wadden Sea oysters around 1900. The second factor is the fierce winters at that time. The third factor is the changed currents due to the construction of the Hindenburg Dam (1923-1927) to the German isle Sylt. All three factors together are said to have caused the extinction of the Wadden Sea oysters. The lack of Wadden Sea oysters led to the settling of foreign oysters in England. These oysters were Pacific oysters who originally came from Japan or Southeast Asia.

This new oyster species is more resistant to environmental changes in the Wadden Sea. About one million of these pacific oysters are nowadays produced in cages outside Sylt. Unfortunately, the settling of pacific oysters had also disadvantages. They spread immensely. Unfortunately, this oyster species has no natural enemies and thus it spreads without restraint in the Danish waters. Only fierce winters and collections on a grand scale could stop this development.

According to the Danish fishing analyses, the incidence of oysters highly increased in the Lister Tief [=depth of the North Sea between Rømø and Sylt] in 2004. 2005 and 2006, a lot of adnate samples were observed and they had an estimated weight of up to 3,300 tons. In 2007, oysters were found throughout the Wadden Sea. They are spreading northwards and they reached the Limfjord and Nissum. Some oysters were even found in Issefjord and in Horsens Fjord.

Pacific oysters grow up to 100 millimetres in the first years and some copies were found which have a diameter of around 30 centimetres. They filter eight to ten litres water per hour (common mussel around two litres per hour).

In Holland, there are whole oyster reefs. This caused a change of the ecosystem.

The collection of oysters is not completely harmless! One has to know the surroundings and the tide. The Tønnisgård Nature Centre on Rømø recommends to collect oysters only in the cold season. The reason is that at a higher temperature, the number of bacteria increases in the water. The Tønnisgård Nature Centre offers tours, where you can go for a ”Big Catch”, but please keep in mind that oyster collecting happens at your own risk.