By the end of july 2015 the media reported a sudden death of 90 % of the young Japanese oysters in the Oosterschelde. The formation of oyster reefs changed the ecosystem in the delta of Zeeland and the Waddensee largely. For the culturing of oysters this mass mortality might now cause a big decrease in production. The reason can be the successful settlement of Ocenebra inornata since its introduction in 2007. That is what oyster growers think. Another reason can be an oyster herpes virus which is found in the oysters since 2010. That is at least the current opinion of marine biologists.