German Federal Agency for Nature Conservation (BfN)


Scientists identify Baltic Sea Grey Seals Video Transcript

Last century, grey seals were endangered throughout the Baltic Sea. For many decades, they almost vanished from the northeast German coast. Conservation work enabled numbers slowly to recover across the Baltic. These large seals are now returning to the German Baltic coast, most of all in winter and spring – including in waters around the island of Rügen. The Federal Agency for Nature Conservation (BfN), South-East Rügen Biosphere Reserve and conservation organisations are now taking coordinated census counts in Greifswald Bay.

Zitat Mähler: When I came to Greifswalder Oie island about seven years ago, grey seals were an absolute rarity. But they have become more and more common in the last few years and we now have a growing population, so we regularly see grey seals in fairly large numbers.

In 2016, the German Oceanographic Museum and the University of Rostock, in cooperation with the Federal Agency for Nature Conservation, launched the first research project on the German Baltic Sea coast for photo identification of grey seals in the bay. This makes use of the distinct markings of each seal – the light and dark patches on their fur.

For the census, the researchers photograph each and every seal, where possible with a frontal and a side shot. The photos are put in a database with the date and precise location. Key features such as the eyes or an ear are marked along with the outline. A specially developed software rectifies the picture. Predefined areas – such as the side of the neck – with notable fur markings are picked out for analysis. The software now compares the picture with those already in the database. The best matches are shown to the user as ‘hits’. If it is indeed the same animal, it is given the same ID number.

The method gives an idea of whether individuals stick to one location and of their seasonal movements. By comparing with data from other countries around the Baltic, the researchers can infer where the grey seals originate. The outcomes of the project, which in future will also be supported by the BfN’s marine nature conservation division on the Isle of Vilm, are important for targeted conservation activities. In this way, the grey seal population can be secured also in the German part of the Baltic Sea for the long term.