¹3000 Ivyside Park, Division of Math and Sciences, Penn State – Altoona Altoona, PA 16601, U S.A.
²Fisheries and Oceans Canada, Great Lakes Laboratory for Fisheries and Aquatic Sciences 867 Lakeshore Road, Burlington, ON L7R 4A6, Canada.

*Corresponding author: epl1@psu.edu

Abstract

   The invasive New Zealand mud snail, Potamopyrgus antipodarm, is a world-wide invasive species currently found in Europe, Australia, Japan, and, most recently, North America. It was first discovered in Lake Ontario in 1991. The purposes of this study was to update the current known geographic distribution of the snail, determine the relationship between depth and population densities, and examine the relationship between Potamopyrgus and dreissenid mussel densities in Lake Ontario. We sampled several locations in Lake Ontario and determined that the range of Potamopyrgus has expanded. However, densities appear to have moderated in the past ten years. In one location (Wilson, NY), the densities of the snail are dependent upon depth with highest densities occurring between 15 and 25 m. At this location, no snails were found at depths of less than 15 m. We found no correlation between the densities of Potamopyrgus and invasive mussels. The reasons for apparent reduction in densities over time and the apparent lack of Potamopyrgus in shallow water are discussed.