Science - October 16, 2009

Grey seal boom in the Wadden Sea

The population of grey seals in the Wadden Sea has increased by a quarter, with baby seals even doubling their numbers, according to the latest count made by Wageningen Imares.

This group of seals was spotted on a sand bank in the Wadden Sea during a counting trip.
The seal count, carried out from aircrafts, registered 2108 grey seals in the (international) Wadden Sea. This is four hundred more than last year. Most of the seals (eighty percent) are found in the Dutch part of the Wadden Sea. The increase in the number of baby grey seals is remarkable. The pups have doubled in numbers to 387. Imares attributes this to the mild winter. The young make up a sixth of the total population.
Colonies
This was the first time grey seal colonies were counted in the entire Wadden Sea. In the past, only those in the western Wadden Sea were counted. The area under survey was extended after the animals were also spotted in Ameland and Schiermonnikoog. The grey seals are slowly colonizing the Wadden Sea. They had almost disappeared from Dutch waters during the Middle Ages until the first of its kind made it here across the North Sea from the English coastal waters in the 1990's.
No growth
The common seal is by far still the prevalent type in the Wadden Sea. Its count is at 21,571 this year in the entire area (the Netherlands, Denmark and Germany). A little above a quarter of these have been spotted in Dutch waters. The growth in their numbers has fallen by more than six percent compared to last year. However, Imares thinks it is still too early to conclude that the population has peaked. The number of pups has grown twice as fast as the total population. Pups make up a quarter of the total number of common seals.

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