Mass starfish strandings typically occur in winter and as a result of stormy weather. Strong currents pluck the starfish off the seabed. Because of the low water temperature, they are too feeble to reattach themselves, so they keep floating around. Strong currents can carry them to the shore and so they end up on the beach.
The phenomenom of mass strandings shows that the common starfish is widely present in the North Sea and their population seems to be growing. Adult starfish have few enemies, except for the herring gull. Nonetheless, they should be cautious around precisely their own: young starfish are often attacked by bigger ones and certain starfish species actively hunt their colleagues.