Bladder Wrack  Fucus vesiculosus

This wrack is one of Somerset’s commonest seaweeds. It is dark brown and usually has pairs of air bladders embedded in its thick, waxy fronds either side of a midrib -although these may be absent when it is young. There are swollen jelly-filled fruiting bodies at the tips of mature fronds. We would like to find out which beaches it thrives best on. (Only photograph attached individuals please!)

Channelled Wrack – Pelvetia canaliculata

This wrack is rarer on Somerset shores than the bladder wrack. It grows as small clumps nearer the top of the seashore on large boulders often just below a zone of black, yellow or grey lichens. The fronds are short and narrow and are ‘in rolled’ to help retain moisture. They don’t have bladders or a midrib. We would like a better idea of its distribution in Somerset.

Common Limpet – Patella spp.

This ubiquitous snail is found on many Somerset shores. We need to make sure we have recorded its occurrence fully all along our coast.  Limpets feed on microscopic algae that grows on any intertidal hard surfaces. You can often see ‘tracks’ on the rocks or boulders where limpets have grazed at high tide using their hard rasping tongues (radula). They attach very tightly to the rocks when the tide goes out as a protection against drying out, wave action and predators. There are many several species of limpet but they can’t easily be told apart without removing them. Please photograph only live limpets and don’t try to remove them as you may damage or kill them.

Thick/Toothed Topshell – Phorcus lineatus

This snail is only found in the South West corner of the British Isles as it needs the warmer waters of the gulf stream to survive. Like limpets it grazes on micro-algae on the rocks. Especially in the summer it can be found quite high up the shore ‘sunbathing’ on the rocks. As its distribution is affected by temperature, this species is an important indicator species for the effects of global warming. We would like to better determine where it is found in the Bristol Channel. It appears to be much commoner at the western end and we are currently not sure if this is related to temperature or to other factors like water turbidity or salinity. Like all topshells it can be told apart from other snails like periwinkles or whelks because it has a ‘mother of pearl’ lustre to the whiter parts of is shell. It tends to have a dark colour on its upper shell surface with a white, pearly base. On the inner edge of its open is a small bump or tooth.  Only record live specimens. These will have a hard trap-door (operculum) that they close over their opening when they are picked up.

Flat/Purple Topshell – Steromphala umbilicalis

This topshell is smaller and flatter then the thick/toothed topshell. It has purple bands across its shell over a light green background which is particularly clear in younger, cleaner specimens. Like all topshells any white areas of the shell have a mother of pearl lustre. If you turn it upside down you can sometimes see a small hole – like a belly button - on the base of the shell (hence is latin name: ‘umbilicalis’). It tends to live lower down the shore than its cousin and is most often found in rockpools. It is also affected by temperature, but seems to have a slightly different range along the coast than the common/toothed topshell. Only record live specimens. These will have a hard trap-door (operculum) that they close over their opening when they are picked up.

Pacific Oyster – Magallana gigas

There were once large populations of native oyster (Ostrea edulis) all along the Somerset Coast, but these largely disappeared last century probably due to over-fishing. In recent decades, we have seen the arrival of the Pacific Oyster (Magallana gigas). These have probably ‘escaped’ as planktonic larvae from commercial oyster farms in France and then spread along the English Channel coast and gradually around and up the south peninsula into the Bristol Channel. In some estuaries in Devon and Cornwall they have become so common they are smothering and outcompeting native marine life. They are still relatively rare on Somerset shores found as isolated individuals rather than extensive colonies. It is important we closely monitor their distribution and potential spread. Pacific Oyster tend to be more elongated with a very scaley and sharp shell compared with native oysters. Only photograph and observe attached living shells.