Grey seal numbers in Wadden Sea show continuous growth in 2024-2025 survey season
The latest grey seal surveys conducted across the Wadden Sea and on Helgoland (Schleswig-Holstein) reveal an increase in both the number of pups born and seals counted during the moulting season. A total of 3,051 grey seal pups and 12,064 moulting seals were recorded during the 2024-2025 survey season - marking a continuing positive trend in the region. These are the findings of the “Grey Seal Surveys of the Wadden Sea and Helgoland 2024-2025” report, published under the Trilateral Cooperation on the Protection of the Wadden Sea.
According to the trilateral Expert Group on Marine Mammals, comprised of researchers and site managers from Denmark, Germany, and the Netherlands, these numbers represent stable growth. Over the past five years, grey seal pup production in the Wadden Sea has increased at an average annual rate of just over 12%, while the number of moulting seals has increased by nearly 10% annually. “This consistent growth reflects the importance of the Wadden Sea as a vital habitat for grey seals,” said Jessica Schop, lead author of the report and researcher at Wageningen Marine Research. “However, differences in regional patterns also highlights the need to better understand seasonal movements to support long-term conservation efforts.”
In 2025, 8,638 grey seals were recorded in the Dutch part of the Wadden Sea—an increase of 10.4 percent compared to 2024. This area accounted for over 70 percent of all observed grey seals. In Lower Saxony, 1,564 individuals were counted, representing 13 percent of the total and a 14.7 percent increase from the previous year. The number of grey seals observed on the island of Helgoland dropped by 37 percent to 1,060 animals, corresponding to 8.8 percent of the total count. Numbers in the Schleswig-Holstein part of the Wadden Sea increased by 74.5 percent to 499 grey seals. On the Danish side, 303 grey seals were counted, a decrease of 16.1 percent compared 2024.
To help interpret these population trends and translate them into management, researchers emphasise the need for more detailed studies on variability in time and space in seal numbers and how environmental factors affect these numbers. “While we present relative changes in abundance, obtaining absolute population estimates will require much more data on seal behaviour and movement,” said Schop. “This will help account for factors like site disturbance and seal migration, especially in areas with fewer sightings.”
Grey seals are the largest predators along the Wadden Sea coast and, like harbour seals, one of the iconic species of the region. Although the Wadden Sea Seal Agreement (WSSA) under the auspices of the Convention of Migratory Species in Bonn does not cover the grey seals, they do benefit from their inclusion in the trilateral Seal Management Plan. Regularly updated, this document assures adequate management of the seals in the Wadden Sea, including monitoring via annual counts. The aerial surveys are coordinated and analysed by the trilateral Expert Group on Marine Mammals.