Invasive mussels now confirmed at Lake Havasu as well as Lake Mead - AZBZ Forums
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Old January 23rd, 2007, 10:56 AM   #1

Join Date: Jun 2003
Location: Peoria, Az.
Posts: 34,643
AZ Game & Fish Invasive mussels now confirmed at Lake Havasu as well as Lake Mead

Invasive mussels now confirmed at Lake Havasu as well as Lake Mead

Hydroelectric power, water delivery and ecosystems could be affected

PHOENIX – The quagga mussel invasion of the Colorado River has now been confirmed in Lake Havasu, which is linked to the interior of Arizona by the Central Arizona Project Canal.

These invasive freshwater mussels were first spotted Jan. 6 at the Las Vegas Boat Harbor at the southern end of Lake Mead by an alert marina employee. At first, officials were hopeful that the invasion was limited to the Boulder Basin area of Lake Mead.

This week, California Fish and Game officials confirmed that the invasive mussels are now in Lake Havasu as well. Efforts are continuing to determine if these invaders are in other areas of the Colorado River.

The Dreissena species of mussels, which includes two closely related mussels, the zebra and quagga, can clog water intake pipes, negatively affect hydroelectric power operations, ruin boat engines, and impact water delivery systems. These small invasive mussels, which originally came from Eastern Europe, have been causing multimillion-dollar problems in the Great Lakes and the Mississippi River Basin. The Colorado River is 1,000 miles farther west than any previously known colonies of these mollusk invaders.

Officials say that so far, the infestation at Lake Mead, or at least for the detectable adult population, appears to be limited to the Boulder Basin area. Inspections have found no evidence of adult invasive mussels at the following locations:
  • Temple Bar marina facilities (Arizona side of Lake Mead)
  • Cottonwood Cove marina facilities (Nevada side of Lake Mohave)
  • Willow Beach marina facilities (Arizona side of Lake Mohave)
  • Willow Beach Fish Hatchery (operated by U.S. Fish and Wildlife Service)

Efforts continue to determine the extent of this mussel invasion in the West. While there are places we have not found mussels yet in parts of Lake Mead or in Lake Mohave, we have to be cautious and assume that they may still be present. We have to take reasonable precautions not to move them as hitchhikers.

“These invasive mussels are a serious threat to water delivery, recreation, hydro-power operations, and fish and wildlife resources,” says Larry Riley, fisheries chief for the Arizona Game and Fish Department. “These small mussels can reproduce and spread rapidly, and are often difficult to detect until they have become well established. A long list of agencies and organizations are cooperatively mobilizing to address this threat.”
Officials stressed that while various cooperators are investigating the extent of the threat and coming up with multiple ways to combat this invader, a critical element is getting the public involved.

“Guaranteed, we need the public – especially boaters and anglers – to help prevent the spread of this aquatic invader,” Riley says.

These mussels can survive in a few inches of water in the bilge or livewell of a boat, can attach to boat trailers, or even cling to the hulls of boats and other flat surfaces. The juvenile form or larvae of this aquatic menace is microscopic and not visible to the eye.

Boaters (including personal watercraft, canoe, and kayak users), divers, and anglers should take the following precautions to help by ensure their boats, vehicles, trailers, and other equipment do not become the means of infecting other waters.
  • Remove any mud or vegetation from your boat or trailer – mussels can hide and hitchhike with this material.
  • Drain the water from your boat motor, livewell, and bilge on land before leaving the immediate area of the lake.
  • Flush the motor and bilges with hot, soapy water or a 5-percent solution of household bleach.
  • Completely inspect your vessel and trailer, removing any visible mussels, but also feel for any rough or gritty spots on the hull. These may be young mussels that can be hard to see.
  • Wash the hull, equipment, bilge, and any other exposed surface with hot, soapy water or use a 5-percent solution of household bleach.
  • Clean and wash your trailer, truck or any other equipment that comes in contact with lake water. Mussels can live in small pockets anywhere water collects.
  • Air-dry the boat and other equipment for at least five days before launching in any other waterway.
  • Do not reuse bait once it has been exposed to infested waters.

Riley stressed that these invasive mollusks are just one of the aquatic nuisance species to be concerned about.

“Boaters, anglers, and other water recreationists should really take routine precautions to avoid transporting any nuisance species. A lot of them are out there, such as golden algae or giant salvinia,” he says. “A few precautions now will help us protect our waters for the future.”

For additional information on this aquatic invader and others, visit:, and the U.S. Geological Survey web site.

Frequently Asked Questions
  • What are quagga or zebra mussels?
  • Where did quagga or zebra mussels come from?
  • How did these invasive mussels get to Lake Mead?
  • What do they eat?
  • Why should we be concerned about these mussels?
  • Mussels were only found in one area of Lake Mead. How can that become a problem?
  • Do the mussels have any predators?
  • What can I do to help?
  • Map of Lake Mead

What are quagga or zebra mussels?
Zebra mussels (Dreissena polymorpha) are small, freshwater bi-valve mollusks (relatives to clams and oysters) that are triangular in shape with an obvious ridge between the side and bottom. The zebra mussel gets its name from the black- (or dark brown) and white-striped markings that appear on its shell.

Where did quagga or zebra mussels come from?
Quagga mussels are native to the Dneiper River drainage of the Ukraine. Zebra mussels are native to the Caspian, Black, and Azov seas of Eastern Europe. These exotic mussels were first discovered in the United States in Lake Saint Clair, Michigan, in 1988 and are believed to have been introduced in 1986 through ballast water discharge from ocean-going ships. Since their initial discovery, zebra mussels have spread rapidly throughout the Great Lakes and Mississippi River Basin states and other watersheds throughout the eastern and central United States. Quagga mussels have not spread as extensively.

How did these invasive mussels get to Lake Mead?
These invasive mussels in Lake Mead are 1,000 miles farther west than any other known colony of zebra mussels. The primary method of overland dispersal of these mussels is through human-related activities. Given their ability to attach to hard surfaces and survive out of water, many infestations have occurred by adult mussels hitching rides on watercraft. The microscopic larvae also can be transported in bilges, ballast water, live wells, or any other equipment that holds water.

What do they eat?
They are primarily algae feeders. They feed by filtering up to a liter of water per day through a siphon.

Why should we be concerned about these mussels?
These mussels are filter feeders that consume large portions of the microscopic plants and animals that form the base of the food web. The removal of significant amounts of phytoplankton from the water can cause a shift in native species and a disruption of the ecological balance of the lake.

These mussels often settle in massive colonies that can block water intake and affect municipal water supply and agricultural irrigation and power plant operation. In the United States, Congressional researchers estimated that zebra mussels alone cost the power industry $3.1 billion in the 1993-1999 period, with their impact on industries, businesses, and communities more than $5 billion.

Mussels were only found in one area of Lake Mead. How can that become a problem?
These invasive mussels can live for three to five years and can release 30,000 to 40,000 fertilized eggs in a breeding cycle and one million fertilized eggs in a year.

Do these mussels have any predators?
These mussels do not have many natural predators in North America, but it has been documented that several species of fish and diving ducks have been known to eat them.

What can I do to help?
  • It is up to each of us to take extra precautions to stop the spread of mussels or any other invasive species. The following actions should be taken with any equipment used in potentially infested waters:
  • All equipment (e.g., dive gear, boats, trailers, motors, etc.) should be visually and tactically (by feel) inspected for the presence of zebra mussels prior to and after use in any water body. Additionally, any vegetation attached to this equipment must be removed and left at the site of origin.
  • Remove all sediment and gritty organic materials; these could actually be zebra mussel veligers (juveniles).
  • Clean and scrub boat hulls, motors, anchors and trailers. Then hose equipment with hot (140° F) and/or high-pressure water. Bilges, live wells, and any other compartments that could hold water should be drained at the site of origin, and, if possible, flushed with disinfectant or hot water. All boat equipment should be allowed to remain completely dry for at least 24 hours before being used again.
  • Thoroughly clean all equipment in a saltwater bath (1/2 cup per gallon) or with warm tap water (104 ° F). Ensure that all equipment remains completely dry for at least 24 hours before being used again. Pay special attention to those areas and equipment that can hold water.
  • Take similar precautions with waders, bait buckets, and other equipment that can hold water or comes into contact with water.

Del – I know you saw the article on the front page of the republic today. We’ve been getting the word out to boaters, anglers, and others. Heavy focus on the Colorado River at this point. Would appreciate if you can share information with anglers that visit AZ Bass Zone. This isn’t an issue that will stay on the Colorado River. Is it the end of the world? No, but it is an important change. Anglers and boaters can help limit the accidental movement of these critters. There are protocols and steps that people can take to help in the body of the message below, and at the very end of it. These aren’t new messages, but they seem to keep getting more important. The note below is a little dated (and will be updated today). Mussels were detected by divers at Lake Mohave too (confirmed on Sunday). With Havasu involved, there is a direct connect to the CAP and central Arizona. Boaters are the other direct connect to central Arizona. I need your help to spread the word.

Most up to date info is on the 100th meridian web site at Info on the critter can also be found at Appreciate any help you can offer. Larry.
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