The Wadden Sea is home to two seal species, the harbour seal (Phoca vitulina) and the grey seal (Halichoerus grypus). Archaeological findings suggest that grey seals were the dominant seal species until medieval times and then vanished entirely. The cause was most probably the ease with which this species could be hunted during whelping on the upper beaches. The harbour seal population also suffered severely, but has been recovering since the establishment of conservation areas in the 1970s. The grey seal gradually returned in the mid-1900s and has been growing in numbers.

The trilateral Expert Group Seals conducts coordinated aerial surveys on an annual basis that cover the entire Wadden Sea World Heritage site and the island of Helgoland. Since 1975, when the first counts were undertaken, the number of harbour seals has grown from below 5,000 to an estimate of 40,800 individuals in 2019. In the light of the growing number of grey seals, trilateral surveys of this species were taken up in 2005. Since then the counted population has grown from less than 2,000 to 6,500 counted individuals. The reports are published annually and can be downloaded in the “Resources” section and below.


Seal Agreement (WSSA)

In 1991, the Agreement on the Conservation of Seals in the Wadden Sea (WSSA) negotiated by Denmark, Germany and the Netherlands entered into force. The Agreement was concluded under the auspices of the UN Convention on the Conservation of Migratory Species of Wild Animals (Bonn Convention, CMS). The WSSA was the first daughter agreement concluded under CMS. The Common Wadden Sea Secretariat (CWSS) acts as the secretariat of the WSSA. The aim of this trilateral environmental agreement is to cooperate closely in achieving and maintaining a favourable conservation status for the harbour seal population of the Wadden Sea. The WSSA contains provisions, amongst others, on research and monitoring, taking, protection of habitats and awareness.


Seal Management Plan

One of the requirements under the Seal Agreement is the establishment and implementation of a conservation and management plan for the harbour seal population. The Seal Management Plan (SMP) contains a comprehensive statement of actions that are or are to be undertaken by the signatories. The plan is under continual review and amended based on the results of scientific research. Since the grey seal population has increased significantly and its habitat protection requirements are similar to the harbour seal, it is now incorporated in the SMP (though not in the WSSA).

The objectives of the SMP are

  • to achieve and maintain a comprehensive conservation and management of both harbour and grey seal populations in the Wadden Sea through common, coordinated measures of the responsible authorities; and
  • to achieve and maintain a public understanding and awareness of the Wadden Sea seal populations as an entity and as an integrated part of the ecosystem.

As part of the SMP, seal reserves have been established in the entire Wadden Sea Conservation Area. They are closed for all activities during the whelping and nursing period, basically from May to September.


Monitoring results

Harbour seal monitoring reports

1999 2000 2001 2002 2003
2005 2006 2007 2008 2009
2010 2011 2012 2013 2014
2015 2016 2017 2018 2019
2020 2021 2022 2023  


Grey seal monitoring reports

2006 2009 2010 2011 2012
2013 2014 2015 2016 2017
2018 2019 2020 2021 2022
2023 2024