International project reveals historical fish assemblages in the Wadden Sea

The trilateral Wadden Sea is a highly dynamic area, providing shelter from predators and rich feeding grounds for a host of fish species. Present long-term data sets used for determining conservation strategies and targets only go back as far as 1960, a period in which the area was already under extensive anthropogenic pressure. To be able to set realistic targets for conservation strategies aimed at pre-defined objectives such as the trilateral fish-targets, additional data is required that go further back in time. In 2022, a team of experts and students from DTU Aqua (Denmark), the University of Kiel (Germany), Groningen University (Netherlands), and the Common Wadden Sea Secretariat (CWSS) worked on the reconstruction of the historical fish assemblage of the Wadden Sea in the project "Systematic review for historical reconstruction of the Wadden Sea fish assemblage – Swimway historical reference" (SHIRE), funded by the Dutch Ministry of Agriculture, Nature and Food Quality (LNV). Using the PRISMA approach for conducting a systematic review, the study aimed to fill the gap in historical knowledge by providing a database on fish assemblages in the Wadden Sea between 1500-1970. In total 4240 individual records were screened of which 109 were eventually included in the synthesis. The final project report has now been published.

"With data on the historical occurrence of 148 species of fish the present database forms a significant informative framework on historic fish assemblages in the Wadden Sea", says Paddy Walker, project manager of SHIRE. "This could be used as a foundation for future conservation efforts". Since 2019, conservation objectives for fish in the Wadden Sea have been implemented via the trilateral Wadden Sea Swimway Vision Action Programme (2019 - 2024). This programme describes actions to improve knowledge of relevant processes, optimise population monitoring, adjust policies and develop, realise, and evaluate measures towards reaching the Trilateral Fish Targets. "The SHIRE project supports the implementation of the trilateral Wadden Sea Swimway Vision and Action programme. We look forward to continuing this promising work towards using historical data to inform the future," adds Julia Busch, project lead from CWSS. The project results are also of relevance for the work of the trilateral Expert Group Swimway (EG-Swimway).