Live Zebra Mussels Found at Lake Mead; Resource Agencies Initiate Program to Assess Extent and Prevent Spread 1-07

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Date: January 10, 2007
Contact: Roxanne Dey, 702.293.8947

Live zebra mussels, a nuisance invasive species, were discovered in Lake Mead on Saturday, January 6, by a Las Vegas Boat Harbor marina employee. The alert marina employee found a suspected live zebra mussel on a cable anchoring the breakwater and immediately notified notified NPS zebra mussel monitoring program volunteer, Wen Baldwin. Baldwin then checked the zebra mussel substrate sampler where additional suspect samples were found at Las Vegas Boat Harbor and subsequently at Lake Mead Marina. NPS resource management staff then collected samples that were sent to an independent laboratory for specimen confirmation. We expect to receive the final results within the next week Also, on Tuesday, January 9, NPS divers were in the water beginning to evaluate the extent of the zebra mussel colonization in the Boulder Basin area of Lake Mead. Zebra mussels negatively affect the environment by reproducing quickly and in large numbers. Zebra mussels are biofoulers that obstruct pipes in municipal and industrial raw-water systems.

In 2003, Baldwin, a dedicated park volunteer, placed substrate samplers at all marina locations on Lakes Mead and Mohave. All locations are checked monthly by Baldwin. The substrate samplers were checked in November during regularly schedule monitoring at Boulder Basin locations. Neither sampler tested positive for zebra mussels in November. The NPS is evaluating whether zebra mussels are at other locations in Lakes Mead and Mohave.

“We are very concerned about this discovery, and its potential impacts on Lake Mead,” said Bill Dickinson, Lake Mead National Recreation Area Superintendent. “We are taking immediate action, in cooperation and consultation with other resource agencies, to assess the extent of the problem, and to develop a management plan.”

Since then, the National Park Service has been working with other federal (US Fish and Wildlife, Bureau of Reclamation), state (Nevada Department of Wildlife, Arizona Game and Fish Department, and California Fish and Game), other regional agencies (100th Meridian Initiative, the Pacific States Marine Fisheries, and the Southern Nevada Water Authority) and local agencies on zebra mussel prevention programs including: 

  • entrance station monitoring for boats entering with license plates from known infected lakes
  • decontamination of boats from suspect states
  • working with concessioners on training and identification of suspect specimens
  • invasive species information as part of boater education programs
  • invasive species prevention information with annual vessel renewals
  • educational materials for participants of national fishing tournaments 

A new agenda item to address this find at Lake Mead has been added to the annual 100th Meridian Initiative Colorado River Basin Meeting, which was already scheduled January 31, at Nevada Department of Wildlife headquarters in Las Vegas, Nevada. Experts from federal, state, regional, and local entities will be discussing a plan of action for preventing the spread of zebra mussels at Lake Mead, and into other bodies of water in the region. The 100th Meridian Initiative is a comprehensive partnership made up of federal, state, private industry and user groups dedicated to help prevent the spread of zebra mussels.  

Zebra mussels were first intercepted at Lake Mead at Temple Bar in May 2004. A park ranger noticed zebra mussels on a vessel and was able to intercept the boat before it entered Lake Mead. There have been several other successful interceptions by park rangers and marina employees. 

Background on Zebra Mussels:

Zebra mussels are freshwater bivalve mollusks that typically have a dark and white (zebra-like) pattern on their shells, but may be any combination of colors from off-white to dark brown. Zebra mussels are usually about an inch or less long, but may be larger. When healthy, they attach to hard substrates.

Until the mid 1980s there were no zebra mussels in North America. That changed when they were inadvertently introduced into waters near the Great Lakes region. It is suspected that zebra mussels hitched a ride in ballast water tanks of commercial ships. Zebra Mussels were first discovered in the United States in Lake St. Clair near Detroit, Michigan in 1988.  Since the 1980s, zebra mussels have spread, unchecked by natural predators, throughout much of the eastern United States. They currently infest much of the Great Lakes basin, the St. Lawrence Seaway, and much of the Mississippi River drainage system. The have begun to spread up the Missouri River and Arkansas River.

Zebra mussels negatively affect the environment by reproducing quickly and in large numbers. Zebra Mussel densities have been reported to be over 700,000 individuals per square meter in some facilities in the Great Lakes area. Zebra mussels are biofoulers that obstruct pipes in municipal and industrial raw-water systems, requiring millions of dollars annually to treat. They produce microscopic larvae that float freely in the water column, and thus can pass by screens installed to exclude them. Monitoring and control of Zebra Mussels costs millions of dollars annually. As filter feeders, zebra mussels remove suspended material from the habitat in which they live. This includes the planktonic algae that is the primary base of the food web. Thus, zebra mussels may completely alter the ecology of water bodies in which they invade.

How can boaters help prevent the spread of zebra mussels:

These aquatic nuisance species can hitch a ride on our clothing, boats, and items used in the water. When visitors go to another lake or stream, the nuisance species can be released. And, if the conditions are right, these introduced species can become established and create drastic results. By following a simple procedure each time boaters leave the water, they can help stop aquatic hitchhikers. Knowing which waters contain nuisance hitchhikers is not as important ---- as doing the procedure every time boaters leave any lake, stream or coastal area:

Additional information can be found at the and

Last updated: February 28, 2015

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