Zebra & Quagga Mussel Invasion in North America David K. Britton, Ph.D. U.S. Fish & Wildlife Service
Two Invading Species Zebra Mussels Driessena polymorpha Quagga Mussels Driessena rostriformis bugensis
Quagga Water color on vellum parchment by Nicolas Marechal (1753-1802), painted at Paris in 1793
Zebra Mussels Invasive Mussels Zebra Mussel Dreissena polymorpha Quagga Mussel Dreissena rostriformis bugensis Freshwater Bivalve Mollusks (clams) Adults about 1 inch long Quaggas slightly larger Dark & light stripes Sometimes all dark Sometimes all light Quagga Mussels
Quagga Mussel
Biology Quagga Mussel Two sexes: Male & Female Indistinguishable externally Generally Sessile as Adults Attach to hard substrates with Byssal Threads Filter Feeders Extremely Prolific Sexually Mature at 3 5 mm First year Broadcast Spawners 100,000-1,000,000 eggs per year May reproduce all year Usually have peak seasons Live about 4-5 years Quagga Mussel Quagga Mussels
Physiological Tolerances Salinity Temperature ph Calcium Emersion Depth Oxygen Zebra < 5 < 30 C 7.4-9.5 > 25 mg/l Seconds to weeks Typically < 100 m > 25% air sat. Quagga < 5 < 25 C? 7.4-9.5 > 25 mg/l Seconds to weeks > 100 m More tolerant
Life Cycle Planktonic Larval Stage (veliger) Generally Sessile (non-motile) as Adults
Clusters Adults attach to any hard surfaces with byssal threads Typically forming clusters
Encrustation
Initial Mode of Introduction A transoceanic vessel from Europe probably carried larvae in ballast water Initial discovery of zebra mussels was in the Great Lakes region near Lake St. Clair in 1988 Initial discovery of quagga mussels was in Erie Canal & Lake Ontario in 1991
Initial Discovery
Current Distribution
Trailered Boats Mussels can attach to weeds that can be carried by boats and trailers Bilge, bait and live wells can carry mussel larvae Mussels can attach to hulls and anchor chains
Impacts & Consequences Environmental damage Habitat alteration Food web disruption Impacts to native species Native Mussels All but gone in St. Clair & Western Lake Erie Up to 10,000 zebra mussels on a single unionid clam
Impacts & Consequences Economic damage Industrial and raw water fouling Municipal Water Supplies Hydro-electric Stations Fossil Fuel Power plants Management & Control costs $1 billion annually
Impacts & Consequences Health Issues Bioaccumulation Concentrate heavy metals and other contaminants Sharp shells = cut hands and feet
Control Methods Eradication is all but impossible Control is costly Chemical molluscicides: Oxidizing (chlorine, chlorine dioxide) Non-oxidizing Manual removal (pigging, high pressure wash) Dewatering / Desiccation (freezing, heated air) Thermal (steam injection, hot water >32 C) Acoustical vibration Electrical current Filters, Screens Coatings: Toxic (copper, zinc) and Non-toxic (silicone-based) Toxic constructed piping (copper, brass, galvanized metals) Carbon dioxide injection Ultraviolet light Anoxia / Hypoxia Flushing
Prevention is the Best Control Method Before trailering Remove all plants, animals and mud Clean and dry everything that comes in contact with water Drain all bilge, bait, and live wells Check all equipment Do not transport bait