斑马贻贝（Dreissena Polymorpha）已被引入五大湖，预计将在北美大部分地区传播。在水处理厂中，为了确定何时应用控制策略，有必要对Veliger进行监测。在本案例研究中，从尼亚加拉河取水的处理厂三年（1990年、1991年和1992年）的采样结果表明，veliger密度差异很大，在>60%的样本中发现了低密度（<10/L）。1991年的采样数据显示，从5月到12月，该河中存在veligers和postveligers。根据这些数据，旨在防止veliger定居点的策略每年可能需要应用多达八个月。包括11个参考文献、表格、图表。

The zebra mussel (Dreissena Polymorpha) has been introduced into the Great Lakes and is expected to spread throughout much of North America. Monitoring for veligers is necessary in water treatment plants in order to determine when control strategies should be applied. In this case study, three years (1990, 1991, and 1992) of sampling results from a treatment plant that withdrew water from the Niagara River show that veliger densities varied considerably, with low densities (<10/L) found in >60 percent of samples. The sampling data for 1991 show that veligers and postveligers were present in the river from May to as late as December. On the basis of these data, strategies aimed at preventing veliger settlement may have to be applied for up to eight months per year. Includes 11 references, tables, figures.