© Linda Tonk
Four new-born flat oysters were found on a diving expedition by DDNZS, a foundation that uses divers to clean up the North Sea. This is a sign that the reintroduction of flat oysters in the North Sea is having success, says researcher Linda Tonk of Wageningen Marine Research.
Is Wageningen Marine Research celebrating the births?
‘We were certainly pleased. This is the first time broods have been found. Probably the descendants of 80,000 flat oysters that were placed in the Borkumse Stenen section of sea, just north of Schiermonnikoog, in May 2018 by the conservation organizations WWF and ARK Nature in partnership with us. Oysters reproduce at the start of the summer so we were hoping there would already be babies. There are probably more than just those four but we would need more extensive monitoring to investigate that.’
Has the tide turned for the flat oyster?
‘In the 20th century, about 20 per cent of the North Sea bottom was covered with oysters. But over time they all but disappeared, mainly due to overfishing and diseases. The fact that the oysters we put out are now reproducing is a promising result. We hope they make it through the winter and that we get more baby oysters next year. If there is enough growth from offspring, the oyster bed will be self-sustaining, which is an important part of this experiment.’
Why is it important to get the flat oyster back?
‘Oyster beds provide important ecosystem services: they generate more diversity and they regulate the water quality. The bottom of the North Sea consists mainly of sand but the oyster beds offer a hard substrate. All sorts of creatures can live on that, such as lobsters, crabs and sea anemones. The beds also function as a nursery for sharks and rays, for instance, which lay their eggs there, and as a shelter and place to hide for little fish. That in turn attracts predatory fish and sea birds due to the opportunities for hunting. In this way, the oyster beds help create a more diverse and healthier North Sea.’