Overall, the grey seal population continues to show a stable growth in the Wadden Sea World Heritage. A 15 percent increase in the number of grey seal pups has been detected and, in total, 5,445 adult grey seals were observed – an increase of ten percent. These are the main findings of the report “TSEG Grey Seal surveys in the Wadden Sea and Helgoland in 2016-2017”, published by the Trilateral Seal Expert Group (TSEG) of the Trilateral Wadden Sea Cooperation.
“Since our first trilateral survey of grey seals in 2008 we have observed a stable growth of the populations,” states Sascha Klöpper, Deputy Executive Secretary of the Common Wadden Sea Secretariat (CWSS): “Keeping in mind that the grey seal has only been returning to the Wadden Sea from UK waters since the second half of the 20th century, these results show how the protection of marine mammals enables species that had previously disappeared to re-establish themselves in an area.” CWSS, together with the TSEG, coordinates the seal surveys in the Danish, Dutch and German parts of the Wadden Sea, including the island of Helgoland.
Adult grey seals are generally counted during the moulting season since they spend substantially more time on land during that period. The total count of 5,445 adult grey seals is distributed as follows: 221 grey seals (+49% compared to 2016) were observed in Denmark, reinforcing the expansion northwards, 141 (+200%) in Schleswig-Holstein, 422 (+40%) in Lower Saxony/Hamburg and 4,045 (+9%) in the Dutch Wadden Sea. With 616 adults counted, a decrease in numbers was observed on Helgoland (-17%). The report states that there are several aspects that could cause this fluctuation. To learn more about the movement of grey seals, the TSEG suggests tracking individual animals.
Even more significant for the population development is the number of newly born pups during the winter counts. An increase of 15 percent was recorded compared to the previous season. In mid-December, during the peak of the pupping season, the number of newborn pups in the Wadden Sea was the highest ever recorded, with a total of 1,279. Pup numbers dropped slightly in Helgoland with a count of 287 pups (-4%). One pup was counted in the Wadden Sea area of Schleswig-Holstein, and no pups were recorded in Denmark during the coordinated counts. However, a pup was seen there in January. It is unclear whether it was born in Denmark. In Lower Saxony/Hamburg pup numbers increased by almost 28 percent to 197 pups and in the Netherlands 794 pups were counted, 21 percent more than last year.
Grey seals are the largest predators along the Wadden Sea coast and, like harbour seals, they are one of the iconic species of the region. In former times grey seals were frequently observed in the Wadden Sea until they disappeared most probably after excessive hunting practices. They re-emerged in the second half of the 20th century, traveling from UK waters. CWSS acts as the secretariat to the Wadden Sea Seal Agreement (WSSA) concluded under the umbrella of the UN Convention on Migratory Species (CMS).
The full report can be downloaded at www.waddensea-secretariat.org/monitoring-tmap/topics/marine-mammals