The disappearance of oysters from privately-owned relaid beds has been an all too frequent occurrence in both relatively recent and historical times. Mostly this would have been an act of poaching or stealing by unscrupulous individuals out to make quick money with minimal effort. Sometimes the vanishing oyster stocks were blamed on other more natural phenomena such as severe storm conditions or more mysterious agents such as the curious one photographed and described here.
When I first saw one of the strange green gelatinous bubbles shown above, I didn’t know what to make of it. I thought maybe it was an accidental form of that bobbly slimey weed you sometimes get on the surface of water in hot weather. I certainly didn’t think of it as being a particular species of seaweed – but I was wrong.
It is Colpomenia peregrina Sauvageau, a brown seaweed commonly called the Oyster Thief because the strange mythology that has arisen around it. It attaches to stones and shells in the sea. Frequently it grows on large shells like those of the common oyster. Usually the hollow sphere is intact. However, if the capsule is damaged, the plant may be filled with air when exposed at low tide. It can then act like a float when re-immersed, rising in the water, and floating away – still sometimes attached to lighter stones or shells, including live oysters. The ‘behaviour’ of this organism was therefore sometimes blamed for whisking away the valuable oysters from relaid beds.
The picture at the top of the post shows an Oyster Thief in perfect condition from Ringstead Bay. More usually I have found them squashed as in the pictures below from Studland where holidaymakers and horseriders have trodden on one.
Revision of a post first published 22 April 2009
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