Invasive clam matting pays off in Lake George

Increasing the amount of weight holding down plastic mats on parts of the lake bottom helped in last winterâ€™s effort to smother invasive Asian clams in Lake George. (Photo provided)

An effort last winter to smother invasive Asian clams in the southern end of Lake George was very successful, officials said Monday — much more so than the campaign a year earlier.

The Lake George Park Commission reported that the use of plastic mats on parts of the lake bottom last winter was 98 percent effective in killing the tiny but prolific mollusks.

The findings were contained in a report issued by the Darrin Freshwater Institute of Bolton Landing, a research facility on the lake operated by Rensselaer Polytechnic Institute in Troy.

The mat treatment was a big improvement over a smaller matting effort in the winter of 2011-2012, when as much as 35 percent of the clams survived in some of the treated areas, leading park officials to make some adjustments.

“We found that mats had moved around and we hadn’t put enough weight on them, so we significantly increased the amount of weight on them, which significantly increased the cost,” said David Wick, the park commission’s executive director.

Last winter’s project cost about $400,000, Wick said. It isn’t yet clear how similar matting projects will be paid for in the future.

“Now that we know we have an effective treatment, we have to identify other areas for priority treatment,” Wick said Monday.

Asian clams were first found in the lake in late 2010, leading to an aggressive effort to eliminate them — one that has so far cost more than $1.5 million.

Left unchecked, the species could multiply rapidly, unsettling the lake’s ecological balance. But officials believe their efforts to reduce the population have been successful, due in large part to the matting.

Over seven months this past winter, seven acres of the lake — out of 27 acres known to contain the clams — were treated using plastic mats on the bottom of the lake to smother the clams. Among the areas treated were those immediately off the Shepard Park beach in the middle of Lake George village, several sites in Boon Bay, and near Shelving Rock.

The Darrin Freshwater Institute in May and June had divers take samples and check for the presence of remaining live clams in those areas. They found 2,603 dead clams and 141 live clams, according to the institute’s report.

In two areas where the clams had newly arrived, officials believe eradication efforts were 100 percent successful. It’s also possible, the Darrin report said, that some of the live clams divers found came from peripheral areas not covered by the mats, or were clams able to move from matted areas to open peripheral areas to survive.

Wick said the mats appear to be effective where the lake bottom is sandy and flat, but may not work where it’s rocky, or a number of docks interfere with areas that need to be covered.

“Not every area is suitable. We don’t have an answer for that yet,” he said.

Suction-harvesting and heat treatment are among the other possibilities, according to the Darrin research team.

“While we still have considerable work to do, this report is very encouraging,” said Lake George Park Commission Chairman Bruce Young. “We still have a chance to keep this threat in check, but we have to stay the course and continue to make eradication efforts a priority.”

About $1.2 million in state Department of Environmental Conservation invasive species funding has come to Lake George since 2006. “The results of the Darrin Freshwater Institute’s study suggest we are making good progress,” DEC Commissioner Joseph Martens said in a statement.

Asian clams are just one of five invasive species that state and local officials are trying to control at the lake, which has a worldwide reputation as a recreational destination for its water clarity and surrounding Adirondack beauty.

This year, there are stepped-up efforts to get people bringing boats from other bodies of water to go through voluntary inspections and decontaminations, while state and local officials debate whether to impose mandatory boat inspections in the future.

Boats coming from other lakes are believed to be a primary source of invasive species contamination. In addition to Asian clams, the lake has problems with plants like Eurasian milfoil and animal species like zebra mussels — and there are concerns about new invasives like the quagga mussel being introduced.

The eradication work has the support of local leaders, who are concerned about protecting the region’s recreational economy.

“With the passage of the county invasive species transportation law and our considerable financial commitment to the Asian clam control project, Warren County takes the protection of Lake George and its economy very seriously,” said Warren County Board of Supervisors Chairman Kevin Geraghty, R-Warrensburg.

The lake’s Asian Clam Rapid Response Task Force will be meeting over the next two months to plan a treatment program for this fall, assuming funding is available. Wick said the commission would like to start this winter’s project in September, and possibly include additional locations for mat treatment — but it will depend on finding funding.

“It’s a huge level of physical and logistical effort,” he said.