Invasive zebra mussels successfully eradicated from Lake Waco

WACO, Texas - The Texas Parks and Wildlife Department (TPWD) says it has determined that invasive zebra mussels have been successfully eradicated from Lake Waco in Central Texas. The successful eradication will help prevent property damage, protect water supply infrastructure, and avoid harm to the aquatic ecosystem.

Zebra mussels were discovered at Lake Waco in late 2014, but officials say quick action at the time killed many of the mussels and helped prevent further spread, which eventually led to the eradication.

"The Lake Waco eradication is a unique success story for Texas. This is one of very few invasive mussel eradications in the U.S. and, to our knowledge, the first successful use of this method," said Monica McGarrity, TPWD Senior Scientist for Aquatic Invasive Species Management, says in a news release. "However, it is now more important than ever for boaters to take action to protect the lake, as it could only take one boat or barge to reintroduce these mussels. TPWD will continue to carefully monitor the lake for early detection."

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Fisheries biologists say that eradication of the invasive mussels is extremely rare and was made possible only by very early detection and a multi-agency rapid response effort.

In September 2014, City of Waco employees found zebra mussels at a single boat ramp on Lake Waco, which were later confirmed by TPWD. Additional surveys in the area found approximately 75 more adult mussels as well as a few zebra mussel larvae, but all were in a localized area around the ramp and adjacent marina.

Additionally, TPWD says that an infested barge believed to be the source of the invasive mussels was identified in the adjacent marina and removed from the lake two days after the mussels were detected. The owner was cited for illegally introducing prohibited zebra mussels. At that time, the lake was designated as "positive" for zebra mussels, but the invasion had not reached fully established, "infested" levels.

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The introduction of zebra mussels into Lake Waco presented a unique opportunity for action, officials say, due to the highly localized nature of the introduction and how quickly the mussels were detected.

In October 2014, TWPD says that partner agencies worked together on a rapid response effort to install nearly an acre of plastic sheeting over the shoreline and lake bottom in the affected area and weighted it down with sandbags. The method was used in an attempt to kill the mussels by blocking oxygen, impede their reproduction, and prevent them from becoming established in the lake. 

The plastic was removed in March 2015 after nearly five months of being in place. While one potentially live mussel was found and eliminated after the plastic was removed, evidence indicated the effort was successful in creating extremely low oxygen conditions not conducive to zebra mussel survival over much of the area.

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Since 2015, TPWD and the City of Waco have continued to monitor the lake intensively, and no zebra mussel larvae, settled adults, or their DNA have been detected in the lake since. The results confirm that the eradication effort was an unprecedented success and Lake Waco will now be downgraded to "undetected/negative" status.

The department says that it is still vital that it gets help from boaters, marina operators, and others to clean, drain, and dry boats before moving them and remain vigilant to stop the spread.

"Boaters can take three simple steps and help stop the spread of zebra mussels," says Brian Van Zee, TPWD Inland Fisheries Regional Director. "Clean, drain and dry your boat when leaving any body of water. Zebra mussels can hide in crevices or residual water and so, even if you don’t see them, you could accidentally take them to a new lake."

"If a boat is stored in the water on a lake with zebra mussels and then taken off the water to be transported to another lake, it will need to be carefully inspected, decontaminated to remove and kill mussels, and then allowed to dry completely," Van Zee says. "We recommend that the vessel be cleaned by someone who is familiar with all the components of the boat, as all livewells, bilges, motors and any other receptacles or water-intake systems coming into contact with public waters must be cleaned and TPWD will provide specifications for proper decontamination."

If you have stored your boat in the water at a lake with zebra mussels, it is likely infested with zebra mussels and poses an extremely high risk for moving this invasive species to a new lake. Before moving your boat to another lake, call TPWD at (512) 389-4848 for guidance on decontamination.

The transport of aquatic invasive species can result in legal trouble for boaters or transporters. Transporting prohibited invasive species in Texas is illegal and punishable with a fine of up to $500 per violation. Boaters are also required to drain all water from their boat and onboard receptacles, including bait buckets, before leaving or approaching a body of fresh water.

An online status map showing all lakes where zebra mussels have been found in Texas. For more information on how to properly clean, drain, and dry boats and equipment, visit the TPWD YouTube channel for a short instructional video or watch it below.

TPWD and partners monitor for zebra mussels in Texas lakes, but anyone who finds them in lakes where they haven’t been found before should report them by emailing photos and location information to aquaticinvasives@tpwd.texas.gov to help identify new introductions.

Anyone who spots them on boats, trailers, or equipment that is being moved should immediately report the sighting to TPWD at (512) 389-4848.