Factors,such as wave action,ice scouring and even the bio-harvest,may have modified population structure as well as shell morphology.

• 菲尔德斯东、西海岸环境因子,如风浪、冰块冲击作用以至生物捕食产生的环境压力,不仅作用于种群个体的生长状态,而且也作用于种群结构。