Zebra Mussel Myth #1: Zebra mussels cannot be eradicated

The notion that zebra mussels cannot be eradicated once they infest a lake appears again and again in the media. It often shows up before zebra mussels themselves are detected. Its purpose at this stage is to increase awareness, heighten vigilance, and instill fear. If you cannot get rid of zebra mussels once they arrive, you had better work hard to keep them out.

This is sound reasoning. Prevention programs involving boat inspections and Clean-Drain-Dry campaigns are the first and best lines of defense. Should prevention fail, however, the perception that zebra mussels are invincible can foreclose on opportunities to knock them out before they become firmly established. Rapid-response programs should be included as a second line of defense in zebra mussel prevention plans.

A growing body of evidence suggests that effective control and even complete eradication of invasive mussels is both feasible and cost-effective under certain conditions. The size of the lake and the extent of the infestation are key factors. For recently infested lakes larger than 500 acres, eradication appears achievable through rapid-response efforts (i.e., immediately treating the portion of the lake where invasive mussels have been discovered).

Rapid-response projects using chemical molluscicides have usually proven successful at eradicating invasive mussels within the treatment area. Zebra mussel larvae, called veligers, are actually very weak. Many introductions fail and die out. Even small additional pressures on a young population can prevent it from gaining a permanent foothold, especially if enacted within weeks or months, as opposed to years. Targeted treatments can fall short of expectations, however, if the treatment area is not large enough, and zebra mussels are later discovered outside the treatment zone.

Even when zebra mussels are discovered in more than one part of a lake, it does not always follow that there is a firmly established and reproducing population. Genomics research has taught us that invasive mussels may well come from more than one vector. This is important because discovery of more than one group of mussels in a lake is sometimes used as a justification for canceling proactive control measures. Rapid-response efforts ought to remain on the table in these cases.

Lakewide treatments are more economical and practical for lakes of 500 acres or fewer. In 2010, the Army Corps of Engineers drained a 337-acre lake in Omaha, NE, to expose and kill zebra mussels. Although veligers were detected five years later, most people familiar with the case believe they were reintroduced after the lake was replenished.

Draining is not always practical, of course, but there are less-dramatic and less-drastic ways to eliminate invasive mussels. The Susquehanna River Basin Commission recently eradicated quagga mussels from an entire lake in Pennsylvania using a low-dose, ionic copper treatment. Posttreatment eDNA analyses and in situ sampling confirmed that the treatment eliminated the quagga mussel infestation with minimal impact on the lake’s rich population of fish and other organisms. At 29 acres and 115 feet deep, the Pennsylvania lake is believed to be the largest waterbody from which quagga mussels have ever been eradicated.

Potash has also been used to successfully eradicate invasive mussels from small lakes. Its cost is approximately four to 10 times that of ionic copper, and the molluscicidal effects linger for 10 to 30 years. Invasive mussels are unlikely to recolonize during this time frame, but neither will native mussels, crustaceans, or non-target zooplankton sensitive to high salt concentrations. These ecological tradeoffs need to be considered, but potash is a viable option in some situations.

We are still relatively early in the learning curve of eradication experiences. Each project brings new lessons and insights, and there is tangible evidence that control is possible. Unfortunately, lakes larger than 500 acres that are fully infested are not currently good candidates for eradication. In those lakes, we must instead learn how best to manage invasive mussels . . . . Continue to read Zebra Mussel Myth #2

This article is the second of a five-part series excerpted from “Four Zebra Mussel Myths and Where They Went Wrong.” It is reprinted here with permission. The full article with references is available at Water Online. Copyright 2019.

About The Author

David Hammond is an environmental chemist who has consulted with private industry on topics including pest management, taste and odor problems, biological wastewater treatment, sustainability, and biomimicry. He holds a master’s degree from the Energy and Resources Group and a Ph.D. in Environmental Chemistry, both from the University of California, Berkeley. Dr. Hammond has four patents and several peer-reviewed publications and currently serves as senior scientist with Earth Science Laboratories, Inc.