ABSTRACT
There are three levels of inspection for nding invasive mollusks, and each has its own purpose. (1) One level is for detecting the species in waters that do not yet have the species but the water quality and dispersal attributes are suf cient to warrant a monitoring program for early detection. (2) Once the species has invaded a system, then a postinvasion monitoring program is needed. The postinvasion monitoring program is largely a temporal one and is used to determine the level of infestations at different times of the year, the periods of reproduction, of settlement, and periods of most and least intense infestation levels. Growth rates and longevities are also part of the analyses at this level. Postinvasion monitoring is especially important to industries and utilities in order to determine when larvae are arriving in the cooling systems, follow the changes in numbers of veligers and attached adults within different parts of a facility; determine the effectiveness of a control program; and minimize the costs of a control program. (3) The third level is for long-term monitoring in large bodies of water, and involves spatial studies to determine variations in infestation levels in different parts (e.g., bays and depths) of the lake/reservoir. Due to horizontal and vertical currents, and differences in water quality among inlets, not all parts of a lake will be affected at the same level. Hence, some industries and utilities may experience low infestation levels while others will suffer from high infestation levels.
