Efforts to reseed North Sea oyster banks near the Wadden island of Schiermonnikoog have produced at least four baby oysters, project organisers World Wide Fund for Nature and nature development organisation ARK said at the weekend.

The baby oysters were discovered by divers checking a research cage that was placed in the North Sea along with three other cages and nine 3D printed reef structures for the oysters to cling to. They measure some five centimetres and were hatched around 2018, researchers think.

A fifth of the Dutch part of the North Sea used be covered in oyster banks but most vanished because of overfishing, pollution and a string of cold winters. Some oyster banks in the Oosterschelde in Zeeland survive but there the indigenous oyster is threatened by the Japanese oyster.

The find is ‘a best-case scenario’, head WNF’s oceans unit Stephanie Verbeek told NPO 1 radio  programme Vroege Vogels. ‘It means that the oyster bank is growing naturally.’

Thriving oyster banks are important because they promote diversity, Verbeek said. They filter sea water and the banks offer a spawning ground for plaice, cod and sea bass whose presence attracts sharks, rays, porpoises and seals.

Birds also visit the banks because they feed off the small fish and shrimps that can be found there.

Ark researcher Brenda van Doorn-Deden, who was present when divers found the baby oysters, said she was initially doubtful about the oysters’ chances of survival because of the strong currents and the MSC Zoë container disaster at the beginning of the year.

But although it is early days for the oyster banks, the baby oysters signal hope for North Sea diversity, she said in her blog monitoring the event.