Researchers face a mystery

Seahorses are back in the German Wadden Sea

Short-beaked common seahorses (pictured), which were thought to have disappeared long ago, are increasingly appearing on German North Sea beaches.(Bild: APA/dpa/Peter Kuchenbuch-Hanken)

Almost 100 years ago, the short-snouted seahorse disappeared from the German Wadden Sea because a fungal infection in the 1930s destroyed almost all seagrass meadows - thus destroying the habitat of the cute little animals. Now the cute creatures seem to have returned to the North Sea.

Short-beaked seahorses, which were thought to have disappeared long ago, are increasingly appearing on German North Sea beaches. In the past two years alone, 70 finds of washed-up specimens of the species have been recorded in the database of the BeachExplorer portal. By comparison, there were only twelve reports between 1949 and 2019. Scientists are now investigating where the animals come from.

"Finds in the Wadden Sea are becoming more frequent"
Where the animals come from or whether there are possibly fixed populations in the German North Sea has not yet been clearly established. "The findings show that seahorses are becoming more common in the mudflats of the Wadden Sea," said Hans-Ulrich Rösner, Head of the WWF Wadden Sea Office. "Even if the animals are still rare, this is cause for celebration."

The seahorses' habitat is kelp, algae or seagrass meadows - but no such habitats are known in the German Wadden Sea. However, such habitats do exist off the Dutch coast and in the English Channel, which is why the researchers believe that the animals drift from there and wash up on the German coast.

This is also supported by the fact that only young males have been found to date. If there was a stable population, older or female animals would also have to be discovered over time, but this has not yet been the case, according to the scientists.

Males are responsible for pregnancy
In seahorses, which belong to the bony fish family, the males become pregnant. The females produce the eggs and inject them into the male's abdominal pouch during sexual intercourse, where they are fertilized by the male's sperm.

Depending on the species, females lay between 150 and 2000 eggs in the male's abdominal pouch. There, the eggs are surrounded by tissue that primarily regulates the breathing of the embryos by absorbing carbon dioxide from the eggs and releasing oxygen to them.

From the moment of birth, the seahorse offspring are immediately on their own and the tiny animals immediately begin hunting their prey, plankton and tiny crustaceans.