Zebra mussels invade upper Chesapeake Bay

Pose threat to reservoirs


Zebra mussels, an invasive species from eastern Europe, have spread to the upper Chesapeake Bay, according to the Maryland Department of Natural Resources.
This freshwater mollusk, first spotted in the Great Lakes in the late 1980s has proliferated across North America and poses a threat to native species and to the water supply in the Baltimore area.
Zebra mussels can have a devastating impact on native wildlife. They colonize in large clusters, including on slow-moving aquatic creatures like crayfish, clams and turtles. In some cases the host animal does not survive.  
They also damage wildlife by feeding on algae. While this improves water clarity, it can be harmful to fish and other aquatic life that depend on algae as a principal food source. 
These mollusks also colonize water intake pipes. If they enter Baltimore's Liberty, Loch Raven and Prettyboy Reservoirs, they can restrict the water flow to our municipal treatment plants. Physical and chemical removal of them can be done; however it is costly and time-consuming. Zebra mussels can also create navigational hazards and damage piers, docks and bridges.   
The Department of Public Works says that prevention is the best way to keep local reservoirs free of this invasive species:
  • If you boat in our reservoirs, please do not use your watercraft in any other waters except the three City reservoirs. Due to the potential for zebra mussel contamination, boaters on Liberty, Loch Raven and/or Prettyboy Reservoirs must sign an affidavit stating that their boat will be used only on these reservoirs. Permits are also required.


  • Only use aquatic bait purchased from a MDNR-certified, zebra mussel-free bait store. Do not use live aquatic bait that you have caught yourself. Do not transfer bait water between bodies of water.


  • Never release wildlife of any sort, land or aquatic, at our reservoirs.
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