Mussel Frequently Asked Questions

FAQ: Quagga Mussel Update for Lake Powell March 3, 2023


1. What is the status of quagga mussels in Lake Powell?
The reproducing population of quagga mussels expanded to all areas of Lake Powell, including the Escalante and San Juan arms of the lake. Adult mussels can be obvious near the surface in all parts of the lake, but they are less numerous and harder to find near inflows. Even with the high population levels in the southern lake, which are becoming a nuisance, no major infrastructure failures have been noted. The population of mussels has been expected to continue to grow and become more dense in all areas, but in 2017, mussel spring reproduction in the southern portion of Lake Powell was lower than in 2016. As the lake level fluctuates, the NPS is monitoring for other ecosystem effects, not only from mussels, but also aquatic vegetation. These effects can include increased aquatic vegetation, algal blooms, and decreased sport fish. Visitors are encouraged to report anything unusual. So far, not many ecological effects from mussels have been seen, except several waterfowl species (coots and common goldeneye) seem to be eating mussels. Evidence also exists that some sportfish are eating mussels.

2. Are quagga mussels in the river below the dam?
Quagga mussels were identified in sampling locations between Glen Canyon Dam and Lees Ferry in November 2014. Mussels continue to be found in the river below the dam. Their distribution is patchy and highly influenced by fluctuating water levels and location-specific flow regimes.
Adult mussels have also been found downstream in Grand Canyon. Mussel larvae (veligers) pass through the Glen Canyon Dam and seek to attach to substrates in the river. In 2007, the U.S. Geological Survey published an assessment on the risk of quagga mussels establishing in the Colorado River Ecosystem below Glen Canyon Dam. The report found that while establishment within Glen Canyon was likely, that the sediment levels in Grand Canyon might limit their ability to become established below the Paria River. The report also points out that negative ecological impacts in the river could be low and that moderate densities of quagga mussels may increase food available to fish, increase the complexity of habitat and stimulate additional benthic production. A link to the report can be found at

3. Can the NPS eliminate or stop the spread of mussels within Lake Powell?
There are no current technologies or treatments that would allow for eradication in an open water environment the size of Lake Powell. When mussels were still isolated in the southern portion of the lake, options to slow the spread of mussels within Lake Powell, such as restrictions on boat movements, were considered. However, due to questionable efficacy, significant disruption to visitors and lake operations, and the difficulty of enforcing restrictions, these options were not implemented. Veligers are also dispersed upstream by wind-generated currents and were always expected to colonize the entire reservoir regardless of any boat movements. In 2016, mussel reproduction was detected in all areas of the lake.

4. What changes will occur for boaters now that mussels exist at Lake Powell?
The Aquatic Invasive Species (AIS) Program at Glen Canyon National Recreation Area has transitioned from a focus on prevention of mussels being introduced into the lake, to a focus on containing the spread of quagga mussels from Lake Powell to other bodies of water. Boaters are still contacted on the ramp, but a higher priority is placed on boats leaving to assure they have taken the necessary steps to protect other waters and comply with the law.

5. Will different types of boats be treated differently?
The NPS identified and ranked the relative risks of different pathways for both the introduction of aquatic invasive species to Lake Powell and the potential spread of quagga mussels from Lake Powell. For spread of adult mussels, long-term slipped and moored watercraft were identified as a high risk vector. Short-term come-and-go watercraft were identified as a lower risk for spreading adult mussels. The NPS has developed appropriate strategies to prevent mussels spread for each of these classes of boats.

ALL VESSELS AND EQUIPMENT BEFORE LAUNCHING: Required self-decontamination (Clean, Drain, and Dry). If visible mussels or other invasive species are identified the vessel will be prevented from launching until the threat can be removed.
ALL VESSELS AND EQUIPMENT BEFORE LEAVING: Required self-decontamination—Clean and Drain before leaving the area; Dry before re-launch. Professional decontamination will be required if the boat is going to be launched without adequate dry time. (See state laws for specifics).
SLIPPED AND MOORED VESSELS: Required to be inspected and if necessary, professionally decontaminated in accordance with Arizona and Utah state laws and as a condition of slip rental.
COMMERCIAL ACTIVITY (permit holders, commercial businesses that operate in the park, contractors): Required to be inspected and if necessary, professionally decontaminated in accordance with Arizona and Utah state laws. This requirement will apply to agency controlled watercraft upon exit from Lake Powell for transport to other waters. This will be managed as a concessioner, contractor, and permittee responsibility as law and policy allow.

6. Where can boats get a hot wash or decontamination?
Glen Canyon offers decontamination services for any non-agency-controlled vessel (other than concessioner, contractor, permittee) observed entering or exiting the park with confirmed visible (or detectable) aquatic invasive species when no other options for control exist. Glen Canyon National Recreation Area does not have the infrastructure or the resources to decontaminate the hundreds of thousands of watercraft using Lake Powell. The NPS will work with local entities to increase inspection and decontamination capability to serve Lake Powell boaters. If self-decontamination will not work for a visiting boater, professional decontamination is available from private businesses near Lake Powell as well as state operated facilities in Utah. NPS employees as well as staff from the states of Utah ( and Arizona ( can provide information on professional decontamination services, when necessary.

7. What is Glen Canyon National Recreation Area doing to stop the spread of mussels to other lakes and rivers?
The invasive species education program has been expanded to include additional information on the procedures required by both Utah and Arizona state laws concerning mussels and other invasive species.

  • Rangers contact boaters both entering and exiting the park.

  • Websites and other online media are utilized to inform boaters before they visit Lake Powell.

  • Flyers, posters and other written materials are produced and distributed to the public.

  • Partnerships with Arizona and Utah wildlife divisions to stop the spread of mussels continue.

As agencies and stewards of the resources at Glen Canyon National Recreation Area, we are actively working to create and implement Hazard Analysis Critical Control Point (HACCP) plans for all aquatic and terrestrial construction, resource work, and research permits, to prevent introductions of new species and containment with respect to the species already present in Lake Powell. HACCP plans are a risk management strategy which includes five (5) integrated steps (activity description, flow of activity, identifying potential non-targets [invasive species], analyzing risk of moving non-targets [invasive species], and completion of the action plan) aimed to reduce the risk of spreading invasive species and other non-targets [invasive species] via human-based pathways [human activities]. Where potential for introductions exist, HACCP plans highlight the opportunities for prevention and containment and provide specific control measures with safeguards to ensure those control measures are operating as intended.

8. What has the NPS done to slow the introduction of mussels into Lake Powell?
The NPS operated a very aggressive mussel prevention program at Lake Powell from 2000 to 2013. The approximate cost of the program was over $7.5 million dollars.

  • Inspections, limited ramp hours, and decontaminations were implemented to prevent the introduction of mussels into the lake.

  • In 2013, 20,000 high-risk vessels were identified and inspected; approximately 6,000 of these high-risk vessels required a decontamination treatment.

  • Thirty-eight vessels with adult mussels transported from other waters were stopped at Lake Powell in 2012.

  • Scientists' prediction that Lake Powell would be the first Western mussel infestation was thwarted.

9. What impacts could occur from mussels in Lake Powell?
Impacts from an invasive species in a new environment cannot be predicted with precision; however, mussel impacts are well documented in the Great Lakes and Lake Mead provides a relatively similar system to Lake Powell that can be used to anticipate impacts. Glen Canyon works closely with Lake Mead NRA. Quagga mussel impacts in the Great Lakes includes

  • Disruption of the aquatic food chain,

  • Degraded sport fishing,

  • Fouled boats and marina facilities such as docks and ramps,

  • Clogged intake pipes and increased maintenance costs for water related facilities and boat engines, and

  • Littered beaches with sharp and foul smelling shells.

10. Are there other Aquatic Invasive Species (AIS) of concern for Lake Powell?
Even with quagga mussels already in Lake Powell, potential invasion by other aquatic invasive species are of concern. Zebra mussels (a close relative of quagga mussels) remain a threat to Lake Powell, as do a virtually unlimited number of other aquatic species that could be spread to the Lake. Any aquatic species that is transported to new waters can become a problem. All water resource users should Clean, Drain, and Dry their equipment after each use.

11. Are other agencies/partners helping to control the spread of mussels?
Preventing the spread of mussels is everyone's responsibility. Glen Canyon National Recreation Area participates in meetings with approximately twenty partner organizations representing local, state, and federal entities and businesses to coordinate mussel prevention and containment efforts at Lake Powell. The states of Utah and Arizona have established laws and regulations to prevent the spread of mussels, begun development of inspection and decontamination capability across the states, and mounted aggressive education campaigns. Other Department of Interior agencies, such as the Bureau of Reclamation, U.S. Geological Survey, and the U.S. Fish and Wildlife Service are very active with research to control mussels, educate boaters, and fund efforts to stop the spread.

12. What can the public do to help? How can boaters find information on the new state regulations?

  • When leaving Lake Powell, all watercraft and equipment are required by state laws to be decontaminated. Most boaters need only self-decontaminate: clean, drain, and dry their boats, watercraft, and equipment.

  • Regulations vary depending on the state, so boaters should review the regulations of any states they will enter with their equipment after being in Lake Powell, including but not limited to Arizona and Utah. For more specific information concerning:

Clean, drain, and dry! The spread of mussels and other aquatic invasive species is preventable. Cooperate with prevention and containment program efforts at Lake Powell and other water bodies. Spread the message, not the mussels.

Last updated: March 14, 2023

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Contact Info

Mailing Address:

PO Box 1507
Page, AZ 86040


928 608-6200
Receptionist available at Glen Canyon Headquarters from 7 am to 4 pm MST, Monday through Friday. The phone is not monitored when the building is closed. If you are having an emergency, call 911 or hail National Park Service on Marine Band 16.

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