“…This is especially due to distinct annual periodicity of the growth that produces observable winter-lines through the shell layers (Mutvei et al, 1994. Increments provide the ontogenetic age of individuals (Ziuganov et al, 2000; thus allowing the age vis-à-vis size comparisons (Bauer, 1991(Bauer, , 1992Hastie et al, 2000a, b;San Miguel et al, 2004;. Importantly, maximum age and shell length as well as growth rate have shown to bear great biogeographical variability with correlation to reproductive output of M. margaritifera (Bauer, 1992).…”