The aim of the Seal Agreement is to promote close cooperation amongst the parties in order to achieve and maintain a favourable conservation status for the harbour seal population in the Wadden Sea. This population was reduced by about 60 per cent in 1988 and 47 per cent in 2002, as a result of two disastrous Phocine Distemper virus (PDV)-epizootics. The trilateral Agreement was concluded between Denmark, Germany and the Netherlands on 16 October 1990 in Bonn, Germany, and entered into force one year later, also in the framework of the Trilateral Cooperation on the Protection of the Wadden Sea. The conservation area is situated within the Wadden Sea, and consists of certain areas in the Netherlands, Germany and Denmark. In 2009 the Dutch and the German parts of the Wadden Sea were also inscribed on the World Heritage list, while the Danish part is expected to be added during 2014. The Secretariat for the Agreement and the coordinating institution for the Seal Management Plan is the Common Wadden Sea Secretariat (CWSS) in Wilhelmshaven, Germany.
The harbour (or common) seal (Phoca vitulina vitulina) may be regarded as an indigenous Wadden Sea species, but it is also the most widely distributed seal species found in coastal waters of the northern Atlantic and Pacific oceans, the Baltic and North Seas. While these year-round residents spend an exceptionally large part of their lifetime in the water, they also use habitats such as sand banks, tidal areas or coastal strips on which to haul themselves out. Such habitats are essential for the maintenance of the seals’ vital biological functions, such as whelping, nursing, breeding, moulting, resting and feeding. The harbour seal is listed on an Annex II of the EC Habitats Directive and special areas have been designated for its conservation. Furthermore, the harbour seal and the grey seal are listed in Annex V, which subjects taking from the wild and exploitation to management measures. In 2013 the greatest number of harbour seals since the beginning of the Wadden Sea-wide seal counts in 1975 was observed. The total count was over 26,000 animals and considering the individuals in the water (and therefore not being counted), the overall harbour seal population is estimated at almost 40,000. Since the seal epidemic in 2002, in which almost half of the population died, harbour seal numbers in 2013 have shown a continuous growth for ten seasons in a row.
Although probably still not at the level of around 1900, the harbour seal population has recovered well from the very low numbers observed in the mid-1970s when hunting was first forbidden, and also after the 1988 and 2002 epidemics. The total population size indicates that the present harbour seal population can be regarded as viable. Comparison with other populations elsewhere leads to the conclusion that the reproduction capacity of the Wadden Sea harbour seal population is satisfactory. This status has to be maintained for the future. With a growing population, the risk of a new epidemic might increase, but with further protection activities, which should include the improvement of the quality of the whole ecosystem, the likelihood of such event should be limited. The increasing industrial marine activities (shipping, sand mining, wind farming etc.) in the off shore areas adjacent to the Wadden Sea are expected to have a negative influence on the marine mammal population. The still growing seal populations will occupy further habitat space e.g. on beaches, and interaction with humans will have to be managed carefully.
The Seal Management Plan (SMP) (v. 2018-2022) builds on the obligations of the Seal Agreement and contains objectives and action points on habitat protection, research and monitoring, pollution and wardening, taking and public information.
The plan covers the Wadden Sea stock of the Harbour Seal (Phoca vitulina vitulina) and is also extended to cover the breeding stocks of the Grey Seal (Halichoerus grypus) in the area, the latter not covered by the Wadden Sea Seal Agreement. The overall aim is to restore and maintain viable stocks and a natural reproduction capacity, including the survival of juveniles of the two seal species. The SMP is an essential instrument that seeks a balance between conservation and economic development and management of the area. The Parties continuously amend the plan in order to meet the challenge of protecting this iconic species of the Wadden Sea.
The implementation of the Seal Management Plan and the monitoring activities developed and accompanied by the Trilateral Seal Expert Group (TSEG) and coordinated by the Common Wadden Sea Secretariat are part of the intense management activities fulfilling the goals of the Bonn Agreement on the conservation of seals in the Wadden Sea.