Cold frosts during the Irish winters of 1962 and 1963 may have started their decline in those years. There is evidence, however, that they may be on the increase again. Despite their fascinating lifestyle, there is no suitable use for them and they do not taste particularly nice. They attach, one above the other, to form a chain. These chains provide each individual with the opportunity of having sex, firstly as a male and then as a female.
Females have males that climb on to their backs and remain there.
These males in time become females and a male may then climb on its back, and so the chain is formed. But they can radically change seabottom sediments, smothering many sea animals and stealing the food of oysters, clams and mussels. In northern France it is estimated that the population may exceed one million tonnes. Their shells in some areas are so dense that they completely cover the sea bed. Dr Dan Minchin, Marine Institute, Fisheries Research Centre, Abbotstown, Dublin 15.