Variation in the Life Span and Size of the Freshwater Pearl Mussel

Within the distribution area of the freshwater pearl mussel (Margaritifera margaritifera L.), the maximum observed life span attained in a population varies from 30 to 132 years and the maximum shell length from 80 to 145 mm. For both life-history traits, the growth constant k is a major determinant. The growth constant describes the shape of the average individual growth curve, the lower its value, the slower is the asymptote approached. Maximum size and life span increase as the growth constant declines and the maximum age almost equals the time necessary to complete the growth pattern