Millions, perhaps billions, of 'By-the-wind sailors' wreck in the South-west.

16/07/2006 00:00:00 The By-the-Wind Sailor, Velella velella, looks like a tiny jellyfish up to 10 cm across, but is in fact a very distant relative. This brilliant blue colonial animal probably comes from the Azores or Western Atlantic and is blown across the ocean driven by a small sail, supported by a paper-like float. The sail has a twist, which may be to the right or the left. It is thought that the two types end up on different beaches. Most in North Cornwall seem to twist to the left. They can be found at any time of year but are most common in the autumn, often occurring after the first south-westerly gales of the winter They are not true jellyfish but colonies of tiny animals called hydroids. One animal forms the float, another the mouth and stomach, hundreds are the catching tentacles, while others do nothing except produce minuscule medusae. Their short tentacles catch very small fish and large plankton and they themselves are eaten by the Violet Sea Snails, which are seldom seen in Britain. They are siphonophores, members of the same group as Portuguese men-of-war, but unlike these their sting is harmless to humans.

They get washed ashore in groups most years particularly along the North Cornish coast. There was a major invasion in 1981. Quite a few were found in 2002 and 2003 was a bumper year. But in September 2004 they turned up from Dorset, South Devon, and the south coast of Cornwall and right up to Islay in the west of Scotland, with reports of millions (or more likely billions) at sea in the Western Channel. In 2004 yachtsmen crossing the Atlantic reported seeing masses 200 miles west of the Azores in May, sometimes sailing through swarms for three days on end. It would have been these or their offspring that arrived on our coasts in their billions the autumn. This year the major wrecks of the autumn were first reported from St Martins in the Scilly Islands in the middle of October. They were subsequently seen in Guernsey, then from the Welsh coast from Anglesey to Swansea and also from the north coast of the south west peninsula as far up as North Devon. At the end of November they were turning up on the south coast with ‘thousands’ at Portwrinkle on the south east Cornish coast and as December came in millions could be found on South Devon beaches from Bantham to Exmouth and even along to Bournemouth in Dorset.

By now billions have turned up on our shores, even being found as far north as the Isle of Skye. However no Violet Sea Snails have yet been reported; anyone seeing one of these or finding any fish among the strandings should report it to Douglas Herdson, Information Officer, National Marine Aquarium, Rope Walk, Coxside, Plymouth, PL4 0LF, Telephone: 01752 275216/01752 600301 or Email Douglas Herdson at the National Marine Aquarium

Courtesy of Douglas Herdson, National Marine Aquarium, November 2006.