Question: We've certainly had a lot of press recently about the quaggas. Could anyone tell me what areas have been worst impacted by quaggas?

Answer:The impacts from the quagga mussels in the lower Colorado River are just beginning. We fear that the impacts might be substantial. They certainly were in the Great Lakes after the invasion of zebra and quagga mussels. It seems that the epicenter for this western quagga mussel invasion is in the Boulder Basin of Lake Mead. Quaggas have been found attached to boats and equipment held in the water at several sites within Boulder Basin. They have also been found in the Nevada state fish hatchery on Lake Mead and at the Willow Beach National Fish Hatchery, just south of Lake Mead. It is my understanding that both fish hatcheries have either shut down or have stopped transporting fish to non-infested areas. Willow Beach National Fish Hatchery helps with two imperiled fish species (razorback sucker and bonytail chub). We hope that their efforts to improve the populations of these species will not be hampered by the quagga mussel problem.

The quagga mussel population at Lake Mead seems to be in an explosive growth phase right now. That means that the impacts we’ll see next year will most likely be much worse than what we see today. This is the first time in North America that quagga mussels have invaded a large water body that was not already invaded by zebra mussels. This is also the first time that zebra or quagga mussels have established a population west of the continental divide. So, we are very interested to see how this infestation may be different from what happened in the east. It seems very probable that pipes for delivering water from Lake Mead and the lower Colorado River (including municipal water supplies, irrigation, and other uses) will become clogged with quagga mussels, slowing or stopping flow. We are already seen mussels in the intake pipes and in the fish hatcheries that use water from the lower Colorado. Maintenance to mitigate these problems and keep water flowing will be expensive (as evidenced by situation in the Great Lakes).

Ecological impacts are a considerable concern as well. As extremely efficient filter feeders, quagga mussels can deplete energy and nutrients in the phytoplankton. The phytoplankton is at the base of a complex food web that almost certainly will be altered as a result. We do not have much information to forecast how this will affect specific aquatic organisms in the west, but we do know that, in general, aquatic invaders can dramatically alter a native ecosystem. At this stage, the possibility of eradicating quagga mussels from Lake Mead is practically zero. Never before have zebra or quagga mussels been eradicated from such a large reservoir. Moreover, only one successful eradication event has been recorded. This was for a small quarry pond in Virginia where impacts to drinking water and native species were not an issue.

The strategy for the West, then, forwarded by the U.S. Fish & Wildlife Service, the National Park Service, and affected western states will be one of containment. Serious efforts to prevent overland transport of quagga mussels from the lower Colorado River are currently being implemented, particularly by way of public outreach and education. This is consistent with the strategy the Minnesota has adopted successfully for years. The State of Minnesota is very serious about aquatic invasive species, and, despite two decades with zebra mussels along their eastern border, Minnesota has been able to successfully prevent spread into their many inland waters. Our hope is that we can do the same for the West.

David Britton, Ph.D.