2005 Highlights: Zebra mussels continue to be a major threat to native mussels on the Upper Mississippi River System and appear to be increasing in abundance at some locations. The U.S. Army Corps of Engineers completed the report “Distribution and Density of Zebra Mussel Veligers at Sites in the Upper Mississippi River System and its Major Tributaries,  2004”.

Zebra mussels (Driessena polymorpha) attached to native mussels in Lower Pool 4, Upper Mississippi River, 2005.  Photos by Mike Davis, Minnesota Department of Natural Resources.