Another exotic mollusc in the Laurentian Great Lakes: the New Zealand native<i>Potamopyrgus antipodarum</i>(Gray 1843) (Gastropoda, Hydrobiidae)

Abstract

In 1991, the hydrobiid snail Potamopyrgus antipodarum (Gray 1843), native to New Zealand, was found 1 km offshore Wilson, New York, in Lake Ontario. This is the first known occurrence of the snail in eastern North America. Densities of P. antipodarum have increased since its discovery, and the snail is expected to spread quickly throughout the Great Lakes area. The biofouling potential of P. antipodarum is probably low; however, its most serious threat may be resource competition with native molluscs. This species was probably introduced in ballast water from transoceanic vessels, thus increasing the list of nonindigenous aquatic organisms introduced into the Great Lakes since the 1800s to 140 different organisms. The risk of other species invasions into the Great Lakes is still possible, despite the now mandatory ballast water regulations.