Public Service Announcements

Zebra mussels have invaded Holt Lake; Boaters can help prevent their spread

USACE. Mobile District
Published May 19, 2021

Final  Zebra Mussels PSA.PDF

MOBILE, Ala. – The U.S. Army Corps of Engineers, Mobile District (USACE) advises the public that Zebra mussels have become established in Holt Lake, imperiling Alabama’s freshwater resources. The decisions of boaters will largely determine the invasive mussel’s spread and impact.

Alabama is home to beautiful and extremely valuable freshwater resources. Our state is known for its incredible fish, mussel, crayfish, snail, and turtle diversity. Among these groups, however, the mussels stand out as especially impressive. Around two-thirds of mussel species present in North America can be found in our waters. Several of these are Alabama endemics, meaning they cannot be found anywhere else in the world! There is one mussel, however, that many of us hoped would never reach our freshwater ecosystems. 

The zebra mussel, Dreissena polymorpha, is included among the world’s worst invasive species due to its devastating ecological and economic impacts. Since arriving to the Great Lakes in the 1980’s from eastern Europe via ballast water release, they have spread across much of the nation, negatively impacting freshwater biodiversity, ecosystem function, and vital infrastructure along the way. Zebra mussels can attach themselves to solid objects, leading to dense infestations. Resultantly, they are notorious for damaging boats, clogging water intake and filtration pipes, and threatening native mussel species. 

Boat engines can overheat if the mussels colonize on motors, while attachment to hulls can lead to reduced speed, lower fuel efficiency, and/or handling issues. Basic infrastructure – including that of lakeshore municipalities, power plants, and irrigation systems – has been known to suffer from zebra mussel related problems, as well. Further, the zebra mussel not only competes with native mussel species for resources and space, but can also colonize on top of native species which may result in smothering and starvation. 

Unfortunately, an established zebra mussel population has recently been recognized in Holt Lake, and small numbers have also been spotted at other locations on the Black Warrior and Tombigbee Waterway. Army Corps of Engineers personnel and state biologists are working to determine the current scope of the invasion and how best to minimize zebra mussel impacts. 

Though established, reproducing, populations of zebra mussels are currently only recognized in Holt Lake, their spread potential is immense. This is especially true as large numbers of microscopic, planktonic, young can be easily transported without detection. After zebra mussels become established in a lake or reservoir they are generally there to stay, but boaters can make a huge difference by protecting new areas from invasion. 

Proper cleaning, draining, and drying of boats is so important for preventing invasion spread that several states have passed legislation enforcing the issue of citations to anyone failing to follow boat hygiene protocols. So far, however, this is not the case in Alabama. The decision to protect our freshwater resources from zebra mussels rests entirely on individual boaters. 

To adequately clean a boat after leaving zebra mussel infested waters, power washing – either at home or at a self-service car wash, and preferably with hot water – is required after draining. Additionally, any equipment that has touched water (such as minnow buckets, tie downs, anchors, etc.) should be cleaned with a dilute bleach solution. Further, one to two weeks of dry quarantine are generally recommended. More detailed cleaning procedures may be found here.

Caleb Shuler, Army Corps of Engineers Natural Resource Specialist at the Holt Resource Office has advice for boaters leaving Holt Lake —

“When you are done fishing for the day make sure and pull your boat plug when you are safely out of the water. This is a good opportunity to make sure all standing water has a chance to drain. Empty minnow buckets, livewells and anything that was exposed or might be holding lake water. Please make sure your boat and trailer are completely dry and cleared of debris and vegetation before you decide to recreate on a new body of water.”

Author:  Riley Lovejoy is a Ph.D. candidate in Biology at the University of Alabama studying the effects of invasive species on ecological communities.

With an area of operation across Alabama, Mississippi, Georgia, and northern Florida, and a vast military region that includes operations across Central and South America, the Mobile District’s award- winning teams of engineering, construction, regulatory and emergency management professionals are nationally recognized for their leadership in delivery of the U.S. Army Corps of Engineers’ civil works and military programs missions to the Nation.

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