Monday, June 4, 2007 - 1:00 PM
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Zebra Mussel Eradication in Virginia: A 1st Open-Water Success Story

Brian T. Watson and Raymond T. Fernald. Wildlife Diversity Division, VA Department of Game and Inland Fisheries, 1132 Thomas Jefferson Road, Forest, VA 24551

In September 2002, the Virginia Department of Game and Inland Fisheries (VDGIF) confirmed that a zebra mussel infestation was present in Millbrook Quarry, documenting the first known population within the Commonwealth.  Given the potential impacts if zebra mussels were to escape, VDGIF worked with federal, state, and local agencies; industry and conservation organizations; and individuals to pursue eradication.  The 3½-year effort involved establishing an interagency workgroup to assess the feasibility of eradication; investigating the hydrologic, geochemical, and biological characteristics of the quarry and infestation; evaluating eradication options; ensuring that zebra mussels had not escaped into other waters; issuing a Request for Proposals for eradication; and selecting a process and contractor to conduct the eradication.  Eradication was accomplished by elevating potassium concentrations in the quarry through the introduction of potash – a commercial grade fertilizer.  The quarry was injected with 174,000 gallons of potash solution (12% potassium) over a 3-week period, with a 100 ppm target concentration.  Eradication was confirmed via visual confirmation by scuba divers, video documentation by robotic camera, and 100% mortality of 80 bioassays of 100 zebra mussels placed at various locations and depths throughout the quarry.  In contrast, other aquatic wildlife continues to thrive in the quarry.