What Causes Starfish to Be Washed Ashore?

A year after the mass starfish stranding in Ireland made the news, a similar event occurred on the beaches near Lincolnshire, England. An estimated 4,000 starfish, along with whelks’ eggs, washed up on the shore after a winter storm. Whelks’ eggs and the common starfish both reside in shallow water. Richard Harrington, a representative of the Marine Conservation Society, suggests that these creatures are dislodged easily and carried to shore during stormy weather.

Starfish tend to feed on mollusks, whose beds are typically in shallow water. Millions of starfish will congregate around mussel beds at any time, and when strong currents pass through these habitats during a storm, starfish can be lifted away from their meal and carried to the shore. While seeing thousands of starfish on land might be a striking sight, it is not uncommon given the huge numbers of these sea creatures that gather around mollusk beds.

Although the second syllable of its name might suggest some level of swimming ability, the starfish is a weak swimmer. Instead, it typically crawls from surface to surface and does particularly well in rocky areas. It has tube-like suction cups on the bottom of its feet that help it to move and to cling to its terrain. If the ocean current is strong enough, the starfish will not be able to hold onto any surface and will drift, unable to control where it travels.

Some starfish move closer to the shore when they are ready to breed, so it is possible that this is what causes them to be washed ashore in large numbers. However, starfish breeding usually takes place in spring and summer, and since most of the mass strandings have been reported in the winter, it is more likely that storms are the cause. One other possibility is that boats dredging the ocean floor for mollusks stir up starfish and cause them to float ashore.