EFFECTIVENESS AND ADEQUACY OF WELL SAMPLING USING BAITED TRAPS FOR MONITORING THE DISTRIBUTION AND ABUNDANCE OF AN AQUATIC SUBTERRANEAN ISOPOD

Abstract: Land-use practices in karst can threaten aquatic subterranean species (stygobionts). However, since their habitat is mostly inaccessible, baseline ecological data such as distribution and population size are not known, making monitoring and risk assessment difficult. Wells provide easy and inexpensive access for sampling subterranean aquatic habitats. Over three years, including a two-month period of intensive sampling, the authors sampled sixteen wells (ten repeatedly) in Jefferson County, West Virginia, USA, for a threatened stygobiont, the isopod crustacean Antrolana lira Bowman, in two areas where the species was known to occur. A. lira was collected during 21 of 54 sampling events. A. lira was collected from 6 wells in which a total of 31 of the sampling events took place. Borehole logs suggest that only these 6 wells intersected appropriate habitat. Using the binomial approximation, the authors conclude that a random well has a 29 % to 91 % chance of intersecting appropriate habitat. In a well that intersects appropriate habitat, a single sampling event has a 51 % to 85 % chance of successful capture. The species occurs heterogeneously throughout the aquifer both in space and time, and thus, repeated sampling of multiple wells is needed t