While Lake Waco hasn’t seen signs of reproducing zebra mussels the last two times waters were tested, city and state officials are still warning visitors to be aware of the invasive species this summer as they work to get the lake removed from Texas Parks and Wildlife Department’s growing list of infested lakes.

A zebra mussel outbreak in Lake Waco in late 2014 led to the listing and was linked to an infested work barge.

During a zebra mussel watch Thursday morning, city officials went knee-deep in the water to turn over rocks near about 12 boat ramps. They were checking to see if the small, potentially destructive creatures have shown up in the most-used areas of the lake, said Nora Schell, Lake Waco Wetlands program director.

Though city officials said the lake shows no signs of a reproducing population of the species, it is still one of 16 lakes in Texas on the state’s infested list. Lake Waco has tested positive for the presence of zebra mussels, but no known reproducing populations persist, according to TexasInvasives.org, a website run by the Parks and Wildlife Department and the Texas Invasive Plant and Pest Council.

But with zebra mussels being discovered in other lakes in the region, most recently on boats and marina infrastructure in Lake Travis, near Austin, the need for inspection continues, Schell said. The city hired about eight people to go out throughout the summer and help boaters check for the pests, and a team of environmental inspectors goes out about every three months throughout the year to check the water near boat ramps, she said.

“They come in on any substrate or surface of boat trailers or water that’s left in boats,” Schell said. “That’s why we don’t want you to carry water off or out of Lake Waco or into Lake Waco, especially if they’ve come from lakes like Lake Belton, and now Travis or Canyon Lake (other infested lakes).”

The group inspecting Tuesday started at Midway Park, then went to Reynolds Park, which reopened to the public recently after flooding filled the area with debris last year, Schell said.

“We go into the water and basically kick rocks up to look and see if they’ve attached to any substrate,” Schell said. “Usually, we don’t do this all together, except for Ridgewood because it takes all our eyes and effort. Usually, we split up.”

Zebra mussels were initially discovered near the Ridgewood Country Club marina at Lake Waco in 2014. City officials feared at the time the Eurasian species, which has no natural predator here and is difficult to eradicate, would quickly spread and clog to the pipes in the city’s water intake system.

But last year’s flooding seems to have actually helped keep the mussels at bay, following the city’s efforts to smother the mollusks by placing tarps over populations, she said.

“The flood last year pretty much nixed everything, so we weren’t able to come back out until everything receded,” Schell said. “According to all the literature we’ve read, zebra mussels don’t like the fluctuation of the water rising and falling, so maybe that’s sort of a biological control we’re unknowingly getting because of natural events that are happening or have happened in the past.”

Clean, drain, dry

Officials also have placed signs near boat ramps to remind visitors to clean, drain and dry their boats and gear immediately after leaving and before entering the lake. Otherwise, boats pose a high risk for spreading the species, according to the Parks and Wildlife Department.

“There’s not a heightened concern because of Lake Travis. It’s a lake-by-lake basis,” said John Tibbs, the Texas Parks and Wildlife Department district fisheries supervisor based in Waco. “We’ve hopefully eradicated the zebra mussels out of Lake Waco, and it looks like we have. It would be just a matter of someone bringing them back in. But with our campaign, we’re just trying to make everyone aware of that: to clean, drain, dry.”

Even if Lake Waco is removed from the infested lakes list, city officials will likely continue checking for zebra mussels, officials said. As much as she would like to see the lake be removed from the list, Schell said she’s afraid the removal would just give visitors a sense they can relax and not worry about them.

“We’re trying to go check monthly during the summer,” city environmental inspector Sally French said. “Because we’re so close, we’ll never quit. The city of Waco will never stop looking for them as long as they’re in the state.”

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