Zebra Mussels Confirmed in Lake Sharpe

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PIERRE, S.D. — The South Dakota Department of Game, Fish & Parks has confirmed the presence of zebra mussels in Lake Sharpe, a mainstem Missouri River reservoir in central South Dakota. Boaters enjoying Lake Sharpe should be aware that the waterbody is now classified as infested for zebra mussels and precautions must be taken to prevent spreading mussels to other waters.

“The mussels were initially discovered by members of the U.S. Army Corps of Engineers while performing maintenance at Big Bend Dam, at the lower end of Lake Sharpe,” said Fisheries Chief John Lott in a statement issued by GFP.  “They were positively identified as zebra mussels by GFP staff. Additional sampling efforts by GFP and the U.S. Fish & Wildlife Service have confirmed that adult zebra mussels are present in multiple areas in the lower portion of the lake.”

Reproducing populations of zebra mussels were discovered in Lewis and Clark Lake and the Missouri River below Gavins Point Dam in 2015. The discovery of the mussels in Lake Sharpe indicates their continued spread upstream in the mainstem Missouri River system. Initial surveys conducted in Lake Francis Case, immediately below Big Bend Dam, have not shown the presence of adult zebra mussels. The elevation of Lake Francis Case is drawn down 20 feet each fall. Mussels less than 20-feet deep would dry out or freeze over the winter, meaning any existing mussels may be harder to find. Additional mussel surveys will be conducted in the coming weeks to determine the extent of the infestation in Lake Sharpe and if zebra mussels are also present in Lake Francis Case.

“The discovery zebra mussels in Lake Sharpe is a game changer for Aquatic Invasive Species management in South Dakota,” Lott said. “Sharpe and Francis Case are two of the most used lakes in South Dakota. Many anglers and recreational boaters who use these lakes are from other areas and use their local lakes soon after being on Sharpe or Francis Case.”

How to Help Stop the Spread

Boaters and anglers should remember to do these three things every time they leave the water:

  • Clean watercraft and trailers of all aquatic plants and mud.
  • Drain all water by removing all drains, plugs, bailers, or valves that retain water.
  • Dispose of unwanted bait in trash or fish cleaning stations when leaving the water.

Completely draining a boat is the first step toward ensuring invasive species are not transferred to other waters. Boaters who have used any water body should clean their boats with hot water (140 degrees) or let them completely dry for at least 5 days before launching in other water bodies.

What is a Zebra Mussel?

Zebra mussels are small, invasive clams native to the Black and Caspian seas in Eastern Europe. Although usually less than an inch in size as adults, they can rapidly reproduce and spread under the right conditions. These mussels can attach to vegetation and hard surfaces, forming dense colonies that can clog intakes for hydroelectric dams, water supplies and irrigation pipes, causing significant economic damages. Zebra mussels may also compete with native species, alter water quality, damage boat motors and docks, and their sharp shells can wash up on shorelines in large numbers.

Zebra mussels can produce up to one million eggs per year, rapidly colonizing new waters. The larval stage of zebra mussels, called veligers, are smaller than the width of a human hair and nearly impossible to detect due to their size. This makes South Dakota’s boat draining and fish and bait transportation laws even more critical in stopping the spread of this species. Veligers float in water for up to a month. This means they can be easily transported to new water bodies in even small amounts of water remaining anywhere in a boat, bait container, or gear used during a fishing or boating trip. While it is difficult to determine exactly how mussels entered Lake Sharpe, all boaters and anglers can help prevent introducing the mussels to new waters.

For more information on zebra mussels and other aquatic invasive species, visit sdleastwanted.com.