the invasion could spread to the interior of Arizona
Divers have found quagga mussels at the Central Arizona
Project (CAP) intakes at Lake Havasu, and officials fear
this invasive mollusk could spread into central Arizona
The CAP canal is one pathway for these
mussels to spread into central Arizona, but these aquatic
invaders could also hitchhike on boats coming from the
Colorado River lakes that have already been infested.
“Quagga mussels could spread into Lake
Pleasant, if they haven’t already. These prolific invaders
pose a significant, multimillion-dollar threat to our lakes,
rivers, streams and water systems,” says Larry Riley, the
fisheries chief for the Arizona Game and Fish Department.
The CAP canal provides water to the
interior of Arizona and stretches into the Phoenix and
Tucson areas. Lake Pleasant on the northern edge of Phoenix
is filled each year with Central Arizona Project water.
Efforts are underway to examine this long
canal stretching across the state to determine if these
mussels have established themselves.
Bob Barrett, a spokesperson for the
Central Arizona Project, emphasized that quagga mussels do
not pose a threat to the public health or to the water
supply. “We’ll do whatever it takes to keep the water
flowing. If they begin to build up, we’ll scrape them off.”
During the last two weeks since their
discovery at Lake Mead on Jan. 6, quagga mussels have been
confirmed at lakes Mohave and Havasu, including adjacent to
the structure that pumps water from Havasu to parts of
southern California. The invasive mussels have also been
found at a fish hatchery in Nevada that provides trout to
Lake Mead and Lake Mohave. Fish deliveries from that
hatchery have been suspended until new procedures are in
place to avoid the spread of these mussels. Efforts are
continuing to determine the extent of the spread so far.
The Dreissena species of mussels, which
includes two closely related mussels, the zebra and quagga,
are less than an inch long, but are extremely prolific. A
single one of these mollusks is capable of producing up to a
million microscopic larvae in a year.
Quagga mussels can be found at much lower
depths than zebra mussels, which is not good news for the
deep reservoirs often found in the West. These
rapidly-spreading invaders can clog pipelines; damage
machinery, such as boat engines; harm fishery resources and
befoul bodies of water with waste. In time, they can
permanently alter a lake’s ecosystem.
The Arizona Game and Fish Department,
National Park Service, California Department of Fish and
Game, and the Nevada Division of Wildlife are urging boaters
and other water recreationists to take positive action to
avoid spreading this aquatic invasive species. Boaters
(including personal watercraft, canoe and kayak users),
divers and anglers should take the following precautions:
Drain the water from
your boat motor, livewell and bilge on land before
leaving the lake.
Flush the motor and
bilges with hot, soapy water or a 5-percent solution of
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
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.
Remove any mud or
vegetation from your boat or trailer – mussels can hide
and hitchhike in this material.
Do not reuse bait
once it has been in the water.
Clean sensitive gear
(diving and fishing gear) with hot water (140 degrees F)
or a soak in warm saltwater (1/2 cup of iodized salt per
gallon of water) and air-dry before use elsewhere.
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
For additional information on this
aquatic invader and others, visit the Arizona Game and Fish
Department Web site at
100thMeridian.org, and the U.S. Geological Survey
Frequently Asked Questions
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
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
Why should we be concerned about
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
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
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
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.