Grey Seal Numbers in the Wadden Sea and on Helgoland in 2020-2021

Expert Group Marine Mammals

In accordance with the annual Wadden Sea grey seal monitoring scheme, which started in 2008, coordinated aerial surveys were carried out around the end of 2020 and the beginning of 2021, covering the sandbanks in Denmark, Germany and the Netherlands. Additional land-based counts were conducted on Helgoland. The pup production, which is indicative of the development of the local breeding population in the Wadden Sea, is monitored by three counts between November and January. The two surveys that take place during the moult in March and April, provide information on the number of grey seals using the Wadden Sea. While peak numbers of seals are observed on the Wadden Sea sandbanks during the moult, it is
important to note that these numbers include both individuals breeding locally as well as migrating seals from the much larger population in the UK. Therefore, more grey seals are counted during the moult than would be expected from the pup production in the Wadden Sea (Brasseur et al., 2015).

Authors: Members of the trilateral Expert Group Marine Mammals (EG-MM): Sophie Brasseur, Christian Abel, Anders Galatius, Armin Jeß, Peter Körber, Kristine Meise, Jessica Schop, Ursula Siebert, Jonas Teilmann, Charlotte B. Thøstesen.

This report was published 2021-07-12.
This report should be cited as: Brasseur S., Carius F., Diederichs B., Galatius A., Jeß A., Körber P., Meise K., Schop J., Siebert U., Teilmann J., Bie Thøstesen C. & Klöpper S. (2021) EG-Marine Mammals grey seal surveys in the Wadden Sea and Helgoland in 2020-2021. Common Wadden Sea Secretariat, Wilhelmshaven, Germany.