Changing Sealife - Snail Survey

FROM Aug 13 TO Dec 31

As the Earth’s climate changes, warming seas and milder winters are allowing species previously found only in southern and western parts of Ireland and Britain to survive further north and east. On rocky seashores, various species of seaweeds, snails, limpets, barnacles and sea anemones are being found in places where they have never been recorded before. Monitoring these changes is important, as it helps us to understand the impact that climate change has upon our coastal wildlife and ecosystems.

Have you seen a dogwhelk, purple topshell or toothed topshell on the coast of Ireland or Wales? If you have then ECOSTRUCTURE WANT TO KNOW ABOUT IT!



Coastal defences such as sea walls and rock armour protect coastal towns, roads and railways from flooding and storms. These structures are usually made of rock or concrete, so they can provide homes for rocky shore wildlife in places where the natural shore is sandy or muddy. It is possible that by building these defences, we have unintentionally helped southern species move northwards by providing stepping stones across areas of sand or mud. The need for coastal defences is likely to increase as climate change brings higher sea levels and more frequent storms. It is important to understand the effects that these structures have on our wildlife and ecosystems.

The Seashore Snail Survey

Ecostructure is collecting information on the effects of climate change and coastal defences on three species of rocky shore snails. All of them are easy to find and identify. These are:

The toothed topshell Phorcus lineatus
A southern species which is migrating north in Britain and Ireland. Easily recognised by its circular aperture (trap door), distinctive tooth, zigzag markings and pearly underside

The purple topshell Steromphala umbilicalis
Also has a circular aperture but is easily recognised by its purple stripes and the distinctive hole (umbilicus) in its underside.

The dog whelk Nucella lapillus
A predatory snail that is particularly fond of barnacles. It has an unmistakeable pointed shape and its shell opening has a distinctive canal and toothed ridge. The shells of dog whelks are hugely variable in colour. While the majority of dog whelks are white, some are brown, orange, yellow or purple and some have banded colour patterns. See how many different colours and patterns you can find! You can also look for dog whelk egg cases. These look like clusters of yellow rice grains and are usually found in damp crevices.

All three species are found on rocks in the intertidal zone; the part of the shore that is covered by the sea at high tide but exposed at low tide.

Ecostructure website Snail Survey Snail Survey Guide