 This forms extremely tough, strong, elastic, byssal threads that secure the mussel to its substrate allowing it to remain sessile in areas of high flow.The byssal thread is also sometimes used by mussels as a defensive measure, to tether predatory molluscs, such as dog whelks, that invade mussel beds, immobilising them and thus starving them to death.In cooking, the byssus of the mussel is known as the "beard" and is removed before the mussels are prepared.