Whelks reach sexual maturity at five to seven years. In Canada, whelks breed from mid-May to the beginning of July. Two to four weeks later, female whelks will lay their eggs in protective capsules, attached to rocks, shells or stones. Each capsule contains as many as 1,000 eggs, and the capsules of several females are grouped together in large masses of over 2,000. Only a few of these eggs will develop, though, as most are used as a source of food by the growing embryos. Whelks have no free-swimming larval stage; instead, the young emerge from the capsules after five to eight months as tiny, fully developed whelks. The life cycle of European whelks is slightly different than their Canadian counterparts due to colder winter ocean temperatures in Canada.