Wageningen Marine Research conducting fish research on the Marker Wadden islands, October 2023. Photo Resource The Marker Wadden islands, which were created in 2016, offer an attractive habitat for various fish species. That is clear from three new publications resulting from joint research by Wageningen Marine Research (WMR), the Dutch angling association and the Netherlands Institute of Ecology.
The gentle, shallow zones on the banks of the Marker Wadden islands turn out to be particularly rich in species. The construction of the islands has increased the extent of this type of bank substantially. There is now 16 per cent more bankside in the Marker lake, and five times as much shallow bankside as before, even though the island group only covers one per cent of the total area of the lake.
The gentle, shallow banks have an important function as nurseries as they offer young fish protection, food and a high probability of reaching maturity. However, there are few fish around the bare sandy banks, especially the banks exposed to the wind and waves. Banks made up of pebbles with vegetation and space between the pebbles have more to offer.
Predatory fish
The waters around the Marker Wadden islands also seem to appeal to adult fish, although to varying degrees during the year. Species that feed on fauna on the lake bed leave the islands during the summer to spread out across the lake. But the area remains attractive all year round to predatory fish, like the perch and pike-perch, due to the large numbers of young fish in the shallows between the islands. Research with fish fitted with transmitters also shows that many fish regularly visit the 30-metre-deep pits created when sand was dug up for the new Marker Wadden islands. However, it is not clear why: are they looking for safety, food or somewhere quiet?
WMR researchers will continue to study the fish around the Marker Wadden for the coming years as part of the Marker Wadden II Knowledge and Innovation Programme. They will be monitoring the extent to which the islands bring about the intended ecological recovery. Last October, Resource published a reportage article with WMR researchers Joep de Leeuw, Joey Volwater and Olvin Keeken on how they monitor the fish around the Marker Wadden islands.
