Wadden Sea seal population grew five-fold in 30 years

In the past 30 years, the number of harbor seals living in the Wadden Sea increased five-fold to about 40,000 animals, estimated researchers from the Joint Wadden Sea Secretariat in Wilhelmshaven, Germany. More than 8,000 seals were observed in the Netherlands, 8 percent more than a year earlier. Thirty years ago, the Netherlands, Germany, and Denmark signed a treaty on the conservation of seals in the Wadden Sea. The population is now about the same as it was in 1900.

The seals were counted in August when they were molting and mostly on land. During the census, researchers observed about 27,000 seals in the Wadden Sea. Because many seals were probably in the water during the count and therefore not seen, the count was adjusted to estimate how many animals were omitted. This brought the researchers to the estimate of 40,000 harbor seals in the Wadden Sea in 2021.

The population growth seems to be leveling off. Since 2012 the annual growth has averaged 1 percent. Growth also differs significantly from country to country. In the Netherlands, the number of seals has grown by 8 percent since 2020, while Denmark saw a 40 percent drop. The Danish seal population has been declining almost every year since 2012. In Germany, the numbers fluctuate. The state of Schleswig-Holstein saw an 18 percent decline from a year earlier, while Lower Saxony and Hamburg recorded a 10 percent increase.

More seal pups were born in several areas, but this did not always lead to population growth, like in Denmark. Experts want to investigate what exactly is going on there.