Quagga mussel invasion confirmed at Lake Pleasant
Boaters asked to inspect their vessels for aquatic hitchhikers

PHOENIX -- Quagga mussels have been discovered at multiple sites at Lake Pleasant, and state wildlife officials are requesting that boaters and other recreationists take simple steps to help prevent this Eastern European menace and other aquatic hitchhikers from spreading to other lakes.

On Dec. 17, small adult mussels were collected from a dry-docked boat that had been moored at Pleasant. A team of biologists from the Arizona Game and Fish Department also discovered mussels in the southern end of the lake from boat slips at the Lake Harbor Marina, at the Pleasant Harbor Marina boat launch, and the 10-lane boat ramp courtesy dock. Those invasive mollusks have been confirmed as quagga mussels.

Quagga mussels, which have caused millions of dollars in damage in the Great Lakes region, were first discovered at Lake Mead in January of this year. Since then, they have been confirmed in lakes Mohave and Havasu and their presence has been suspected, but not confirmed, at Lake Powell. This past fall, quagga mussels were discovered in a segment of the Central Arizona Project (CAP) Canal in Scottsdale. The CAP canal originates at Lake Havasu. Water from the CAP is used to fill Lake Pleasant.

“We suspected that it was just a matter of time before quagga mussels became established in Lake Pleasant, but we hoped it wouldn’t happen so soon,” said Larry Riley, a fisheries biologist with the Arizona Game and Fish Department.

Riley, who is heading the Quagga Team for the state wildlife department, pointed out that a single quagga mussel can produce 30,000 to 40,000 fertilized eggs in a single breeding cycle. One adult female quagga can release up to a million eggs in a single year.

Game and Fish Department officials are asking all boaters and anglers throughout the state to help fight the continuing spread of these and other invaders by routinely taking simple precautionary steps each time they visit a waterway anywhere in the state.

Riley added that the presence of other invasive species, such as golden algae, means all boaters and other water recreationists should take simple, precautionary steps – every time they go to a lake, river or stream.

Before leaving a lake or other waterway, always:

• CLEAN the hull of your boat, remove all plant and animal material.
• DRAIN the water from the boat, livewell and the lower unit.
• DRY the boat, fishing gear, and equipment.

If you are a day user, please wait five days before launching your boat someplace else. This five-day waiting period will aid tremendously in killing those hidden hitchhikers on your boat, such as the microscopic quagga larvae. Also, it is a good idea to wash the hull of your boat with high-pressure water, either at the lake, if washers are available, or after leaving the waterway.

Visiting a self-help car wash that has high-pressure soapy water is an excellent idea either on your way home, or while on the way to the next lake – it can even help keep your boat looking new.  Or, giving your boat a hot soapy bath when you get home can also help protect your investment and while also helping protect the next lake you visit.

Remember, many of these aquatic hitchhikers can harm your boat as well. These invaders will attach themselves to boats and can cause damage to boat motors if they block the flow of cooling water through the engine.

If you are moving a boat that has been moored on a mussel-positive lake, please take at least one of these extra precautions:

* Power wash the hull so that it is clean “to the touch”
* Bilge decontamination that consists of either a 140-degree hot water flush of the bilge spaces or
* A household vinegar flush of the bilge spaces, or
* A mandatory minimum 27-day desiccation period where the boat is removed from the waterway and allowed to dry out; all through-hull fittings and bilge plugs must be opened to the air with no residual lake water allowed to remain standing in the bilge spaces; if, for any reason, water cannot drain or standing water remains in the bilge, it must be treated with heated water or vinegar solution.

Quagga mussels do not pose a known threat to human health. Biologists are concerned that quagga mussels may cause ecological shifts in the lakes they invade, with consequences to valued wildlife resources.

Because these invasive mussels attach to hard surfaces like concrete and pipes, they will affect canals, aqueducts, water intakes and dams, resulting in increased maintenance costs for those facilities.

Quagga mussels 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, a close relative of the quagga, gets its name from the black- (or dark brown) and white-striped markings that appear on its shell.

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.

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. 

They are primarily algae feeders. They feed by filtering up to a liter of water per day through a siphon. These mussels 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 species and a disruption of the ecological balance of a lake or other waterway.

These mussels can 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.
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