The results will be presented on March 25, 2025, with special attention to their application in future management and protection. Rijkswaterstaat is involved in various ways in the projects, both as partners and financiers.

The Wadden Mosaic project focused on the sublittoral nature of the Wadden Sea, the area that is permanently underwater. The research concentrated on species living in or on the seabed, such as shellfish, worms, starfish, crabs, and shrimp. The Swimway Wadden Sea project mapped the role of the Wadden Sea for different fish species, aiming to understand their migration patterns and the importance of the area for biodiversity.

What Hard Structures, Shellfish Banks, and Seagrass Teach Us About the Wadden Sea

Oscar Franken, scientific coordinator of the Waddentools Wadden Mosaic project, reflects: ‘Until recently, a comprehensive picture of the seabed life in the Wadden Sea was missing. Thanks to two large sampling campaigns, we now have detailed data on the distribution of nearly 140 animal species in the sublittoral, the always underwater part of the Wadden Sea, and their interrelationships.

The research focused on the deeper parts of the Wadden Sea and mapped ecologically valuable areas. Additionally, management measures were tested, such as promoting shellfish banks, the impact of hard structures on the seabed, and the barriers to the recovery of large seagrass.

The overlap between protected areas and ecologically important locations was also evaluated. ‘In the deeper parts of the Wadden Sea, only 2% of the valuable locations fall within protected areas,’ says Franken. ‘Protected areas are intended to protect shellfish banks and biodiversity hotspots, but these were not included in the analysis. The research has provided valuable insights overall.’

Fish, Shellfish Banks, and the Hidden Worlds of the Wadden Sea

The Waddentools Swimway project focused on fish in the Wadden Sea, with emphasis on underexplored areas such as the deeper parts, shellfish banks, and the edges of the mudflats. The research mapped how different fish species utilize various habitats, which areas are important, and what the impact of climate change on fish populations might be. These insights are valuable for the future management of the Wadden Sea.

‘With this project, we have filled important knowledge gaps,’ says scientific coordinator Ingrid Tulp. ‘This mainly concerns species that fall outside the regular monitoring, such as larger fish (bass, mullet, sharks), schooling fish (herring, sprat), and fish in little-studied areas, such as salt marshes and mussel beds.

Tulp continues: ‘We investigated how these species move, which places they use, what they eat, and how they develop. We also looked at the impact of climate change on their habitats. For example, we discovered that bass swims to the English Channel in winter but returns to its familiar place every summer, and that fish in salt marsh creeks depend on freshwater supply. Additionally, the deeper channels of the Wadden Sea are essential for small pelagic fish and the birds that depend on them.’

Intensive Collaboration for Research on the Wadden Sea

The Swimway Wadden Sea project is a collaboration between the Royal Netherlands Institute for Sea Research (NIOZ), University of Groningen (RUG), Wageningen Marine Research, the Waddenvereniging, Rijkswaterstaat, and Sportvisserij Nederland, funded by the Waddenfonds, the Ministry of Agriculture, Nature and Food Quality (LVVN), and the provinces of Groningen, Friesland, and North Holland.

The Wadden Mosaic project is a collaboration between Natuurmonumenten, RUG, NIOZ, and Rijkswaterstaat, also funded by the Waddenfonds and the provinces of Groningen, Friesland, and North Holland. Both projects are part of the overarching Waddentools project.