US Fish & Wildlife Service



Published by the U.S. Fish and Wildlife Service


Zebra mussels are prolific alien invaders that have rapidly become
established in waters of the eastern United States and Canada. These
natives of the Black, Caspian, Azov and Aral Sea drainage basins were first
discovered in Lake St. Clair near Detroit, Michigan, in 1988. By 1991, they
had spread throughout the Great Lakes basin and are now established
throughout the Mississippi River basin and are spreading west into
Oklahoma. Except for Oklahoma, zebra mussels have not been detected in
open waters of the West. However, without effective prevention measures,
their invasion into the West is a real and imminent possibility.

Zebra mussels are causing significant economic and ecological impacts
throughout their range. They have biofouled thousands of municipal and
industrial water delivery systems, resulting in annual expenditures of up to
several $100,000 for control and detection activities. They are significantly
impacting aquatic ecosystems, altering nutrient flow, decimating native
mussel populations, and providing a sink for environmental contaminants.

The major pathway for zebra mussels to invade the West is not from the
ballast water of ships but from boats, personal watercraft, and related
equipment transported from infested to uninfested waters. Zebra mussels
attach to hulls, trailers, and other exposed locations on boats, boating
equipment, and personal watercraft. Their free-living larva can enter
motors, live wells, or other moist areas and may remain viable for more
than 10 days when attached to boat hulls (Tyus, Dwyer, and Whitmore
1993). Their adaptability, their lack of natural predators, and the propensity
of boaters to move their boats from one body of water to another have
facilitated the rapid spread of zebra mussels throughout their current

Additional pathways for the spread of zebra mussels and other ANS are
also a major concern for western States and Tribes and public and private
entities. These other pathways must be addressed, but formulating plans to
deal with them will take time and resources. Consequently, this Initiative’s
primary focus is on the transfer of zebra mussels and other ANS through
recreational activities and commercial boat hauling. Additional pathways
will be addressed as resources permit.

Amendments to Public Law 101-636 call for the development of a program
to prevent the spread of zebra mussels west of the 100th meridian. This
100th Meridian Initiative outlines management activities that will help
prevent, detect, and control zebra mussels and other ANS in 100th
meridian jurisdictions and west. The 100th meridian jurisdictions include
Texas, Oklahoma, Kansas, Nebraska, North and South Dakota, and

The goals of the 100th Meridian Initiative are to: 1) prevent the spread of
zebra mussels and other ANS in the 100th meridian jurisdictions and west
and 2) monitor and control zebra mussels and other ANS if detected in
these areas. These goals will be achieved by addressing seven components:
1) information and education, 2) voluntary boat inspections and boater
surveys, 3) commercially hauled boats, 4) monitoring, 5) rapid response, 6)
identification and risk assessment of additional pathways, and 7) evaluation.

The 100th Meridian Initiative represents the first comprehensive and
strategically focused effort, involving Federal, State, Tribal and Provincial
entities, potentially affected industries, and other interested parties to
begin addressing pathways to prevent the westward spread of zebra
mussels and other ANS. Success will depend on the commitment and
support of these groups to aggressively combat the introduction and spread
of these destructive invaders.