Aquatic Nuisance Species

With the summer months fast approaching, boating, fishing and other watersports will be on the increase. Unfortunately, concerns about the spread of invasive aquatic creatures such as zebra and quagga mussels will accompany those who enjoy lakes and streams in Colorado.

Zebra and quagga mussels have previously been confined to roughly the eastern half of the United States. But in the early part of 2008 they were found in Pueblo Reservoir and in the fall of '08 the larval form (veligers) of the mussels were detected in Grand County reservoirs.

Although there are other species on the aquatic nuisance list, the speed with which quagga and zebra mussels can spread has made them a top priority for control by state agencies. Once a body of water is contaminated with these species, massive colonies can develop in a short period of time with the potential for serious damage to habitat, agricultural operations, recreational equipment and other infrastructure.

Zebra and quagga mussels have no natural controls in the United States. They are also virtually impossible to eradicate once they get into a body of water. Therefore, they can populate a body of water with virtually no restraint. Without predation or some other control, unlimited population growth has a fundamental and destructive effect on an ecosystem.

It is also unfortunate that this problem emerges at a time when the resources needed for a vigorous attack are limited by a weakened economy. It is possible that operators and owners of the various reservoirs around the state will close bodies of water to boating if the threat of invasive aquatic pests cannot be adequately addressed.

The fish screen on the outlet side of Elkhead Reservoir is an example of a structure that would be threatened by zebra and quagga mussels. The purpose of the screen is to keep non-native predatory fish from getting into the Yampa River. If the screen becomes encrusted with invasive mussels, its purpose is defeated to the detriment of the Endangered Fish Recovery Program.

This is an unacceptable outcome and it is possible that the reservoir would be closed to boating as a result.


There is now a mandatory inspection program in place to help prevent the spread of zebra and quagga mussels. But the ultimate solution to the problem is for those who enjoy Colorado watersports to take proper preventive measures and educate themselves about the problem.