Harbour Seal Numbers in the Wadden Sea and on Helgoland in 2014
Trilateral Seal Expert Group (TSEG)
In 2014 the coordinated aerial surveys for harbour seal counts of the entire Wadden Sea were performed as in previous years (started in 1975) according to the Seal Management Plan. The counts are synchronized between the three Wadden Sea countries Denmark, Germany and the Netherlands, in order to obtain a single estimate for the number of harbour seals in the entire Wadden Sea and the number of pups born. Seals are counted when hauling out on land and counts are planned to be carried out when low-tide occurs around midday.
The variation in the number of seals hauling out from year to year and over a longer period may be affected by different weather conditions, disturbance, food availability close to the haul out sites, or a change in the age and sex composition of the population (Härkönen et al. 1999). Also, the timing of birth has been shown to change over time potentially affecting the percentage of pups counted at the same time of year over a long period (Reijnders et al. 2010).
Authors: Anders Galatius, Sophie Brasseur, Richard Czeck, Britta Diederichs, Lasse Fast Jensen, Peter Körber, Ursula Siebert, Jonas Teilmann, Sascha Klöpper