The concern caused by the explosive spread of the zebra mussel,
(Dreissena polymorpha), within the United States resulted in passage of
the Nonindigenous Aquatic Nuisance Prevention and Control Act of 1990
(P.L. 101-646). The impact of this biofouling pest on the economy and
ecological processes in the U.S. and Canada has required prompt action
on a large scale to prevent further infestations and minimize ecological
degradation. This map layer is a compilation of reports of confirmed
zebra mussel sightings in the United States from 1988 to January 2008.
It provides geographical and historical information to show distribution
over time. The reports came from a variety of Federal, State, and
municipal agencies, public utilities, universities, engineering and
private consultant firms. The locations of confirmed sightings were
registered at 1:100,000-scale on EPA Reach File Version 3.0 and are
maintained as an ArcInfo export file. This is a revised version of the
May 2003 map layer.