Don’t move a mussel – NOW it’s the LAW:

New regulations are in effect to help fight spread of aquatic invasive species

New state regulations to help prevent the spread of quagga mussels and zebra mussels went into effect in March 2010.

These regulatory measures, known as “Director’s Orders,” were authorized by the Aquatic Invasive Species Interdiction Act passed by the Arizona Legislature in 2009. They give the State of Arizona, particularly the Arizona Game and Fish Department, the authority to identify and assess those species considered aquatic invasives, identify the waters that are affected by those invasives, and establish mandatory conditions for moving watercraft and other equipment from those waters.

The department conducted a series of public meetings and a webcast in January 2010 (click on the photo at left to view the webcast) to describe the proposed Directors Orders and solicit comment.

It is critical for anyone who uses watercraft, or has a business reliant on watercraft, to understand the essential nature of this aquatic invasive species containment effort. The spread of quagga mussels has far-reaching impacts, both financial and ecological, that can touch virtually every resident of the state.

Quagga mussels were first found in Arizona in Lake Mead in January of 2007. They originally came from Eurasia and became established in the Great Lakes in the 1980s. Since being discovered, these prolific invaders have spread rapidly. A single adult quagga mussel can produce a half-million larvae in a single year. They colonize rapidly on hard surfaces and can ruin boat motors and clog water intake structures, such as pipes and screens, thereby impacting pumping capabilities for power and water treatment plants. Invasive mussels such as quaggas and the closely related zebra mussels have cost industries and businesses in the Midwest hundreds of millions of dollars in maintenance and damage repair.

Boaters in Arizona have done a good job so far of voluntarily practicing “clean, drain and dry,” along with waiting five days before visiting another lake,” said Tom McMahon, invasive species coordinator with the Arizona Game and Fish Department. “Now Arizona has Directors Orders in effect requiring boaters to follow those practices at lakes known to have quagga mussels.”

Below are the Arizona Game and Fish Department Director’s Orders (signed, approved and filed with the Secretary of State as of March 1, 2010):

Director’s Order 1 - List of aquatic invasive species (AIS):

  • Quagga Mussel (Dreissena bugensis)
  • Zebra Mussel (Dreissena polymorpha)


Click here to see the complete Director's Order 1 [PDF, 29kb]

Director’s Order 2 - List of AIS affected waters:

  • Lake Mead
  • Lake Mohave
  • Lake Havasu
  • Lower Colorado River from Havasu to Mexico
  • Lake Pleasant

Click here to see the complete Director's Order 2 [PDF, 60kb]

Director's Order 3 - Mandatory Conditions for Movement

The mandatory conditions differ for Day Users (watercraft in listed AIS affected waters for 5 days or less) and Long Term or Moored Watercraft (watercraft in listed AIS Affected Waters for more than 5 days).

Click here to see the complete Director's Order 3 [PDF, 105kb]

Decontamination Protocols

Click here to see the Decontamination Protocols for Day Users and Long Term or Moored Watercraft [PDF, 55kb]

Quagga mussel and aquatic invasive species resource information


Frequently Asked Questions

What are quagga or zebra mussels?

Quagga mussels (dreissena bugensis) and zebra mussels (dreissena polymorpha) are freshwater, bivalve mollusks that have invaded North American waters. Quagga mussels were detected in Lake Mead in early 2007 and are now found in several other Arizona waters. Zebra mussels have not yet been detected in Arizona waters. Despite some minor morphological and ecological differences, both species are very similar and pose a significant threat to our waters. The quagga mussel shell is striped, as is that of the zebra mussel, but the quagga shell is paler toward the hinge. Overall, quaggas are rounder in shape, while zebras are more triangular and can be flat on one side.

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?

The invasive mussels found in Lake Mead in 2007 were 1,000 miles farther west than any other known colony of zebra mussels at the time. 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 for extended periods, 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 planktonic feeders. One individual mussel can filter up to a liter of water per day through their 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 these invasive mussels and any other aquatic invasive species. The following actions should be taken with any equipment used in quagga-infested waters:

  • All equipment (e.g., dive gear, boats, trailers, motors, etc.) should be visually and tactically (by feel) inspected for the presence of invasive 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 invasive 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 (140 F). All boat equipment should be allowed to remain completely dry for at least five (5) days before being used again.
  • Thoroughly clean all other equipment (nets, poles, etc.) in a saltwater bath (1/2 cup per gallon), with vinegar, or with hot tap water. Ensure that all equipment remains completely dry for at least five (5) days 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 lake water.


Quagga mussels and aquatic invasive species (2010).

Retrieved March 7, 2010, from Arizona Game & Fish Department website


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