The 10th Wadden Sea Day, held on 27 August 2015 in Wilhelmshaven, was dedicated to marine mammals in the Wadden Sea World Heritage. More than 80 scientists, managers, policy makers and other Wadden Sea stakeholders participated in the event to discuss challenges and prospects for the future of these top predators of the Wadden Sea ecosystem. The Wadden Sea Seal populations (mainly harbour seals but increasingly also grey seals) have shown steady growth rates in recent years. The number of animals has reached record values over the last couple of years, despite the major epizootics of 1988 and 2002.