Despite aggressive efforts to eliminate them, it looks like invasive Asian clams are in Lake George to stay.
The prolific invader reached three new locations this year, bringing to 19 its known colonies around the popular lake, widely acclaimed for its beauty and clear waters.
The dime-size bivalve has spread since it was first found in 2010 despite $2 million in eradication efforts, at least some of which looked initially successful.
The problem is, only one clam has to survive for an entire new colony to grow.
The lake's Asian Clam Rapid Response Task Force is ending intensive efforts to eliminate the tiny clams and hoping to monitor and manage the population instead.
"We're not going to put money into areas where we know they'll be coming right back," said Walt Lender, executive director of the Lake George Association, one of the participants in the task force.
Based on a survey completed in early September, about 100 acres of lake bottom now have the Asian clams; eradication can cost up to $80,000 per acre.
Until now, there was some hope the clams could be killed off, although "every year it's gotten a little bleaker," said David Wick, executive director of the Lake George Park Commission.
Lake George has other invasives: Eurasian milfoil, spiny water flea, curly leaf pondweed, and zebra mussels. But Asian clams are among the most threatening, because they are so prolific. A single clam can self-fertilize and produce more than 100,000 offspring in its lifetime.
In a worst-case scenario, its continued spread could litter beaches with sharp shells and consume plankton that fish rely on for food and forms of algae that feed on clam waste could cloud the clear waters.
So far, though, Wick said there's been no significant impact on water quality or recreation.
Lender acknowledged task force members are disappointed that the clams have been a permanent part of the environment.
"We wish they had never gotten here to begin with, and we tried our level best to come down on them as hard as we could, but it's one of those deals where you have to get all of them or they come right back," Lender said.
What their long-term impact will be is unclear.
"As we see Asian clams expanding their presence in Lake George, it's a fair question how the lake will respond," said Eric Siy, executive director of the Fund for Lake George, which helped pay for anti-clam measures.
At Lake Tahoe, the famed lake on the California-Nevada border, programs spend about $1 million annually to try to manage an Asian clam population without totally eliminating it.
The clam is native to China, Korea and other Asian countries, and was first reported in the United States in the 1920s. It has spread across the country.
In previous winters, officials concluded that ice-cold water in the winter killed as many as 90 percent of the clams, helping slow their spread.
But the mild winter of 2015-16 didn't have the same impact. The lack of winter die-off is believed to be a major factor in their spread this year.
"None of the sites was knocked back to any significant degree," Wick lamented in an interview last week.
Originally, officials believed the clams couldn't survive in such cold water, but Wick noted that historical records show that Lake George has warmed an average of four degrees Fahrenheit over the last 30 years.
The primary strategy for fighting the clams has been spreading plastic mats on the lake bottom to suffocate them. The mats aren't effective, however, in areas where docks or other obstacles are present - and they aren't practical to use over a wide area.
The new clam sites are at Sand Pebble Beach in Lake George, Cape Cod Village in Hague and the south side of the Edmunds Brook delta in Lake George. All have conditions that make treating them with plastic mats difficult, the task force's new survey found.
"The challenge is that 99 percent (die-off) is a failure, because they come right back," Wick said.
The surveyors also believe the previously identified clam beds got larger and denser this year.
The task force's future plan is to continue monitoring, deciding on a case-by-case basis whether it's feasible to attack the sites.
"Eradication on a lakewide basis is not feasible at this point," said Lender. "We still hope to do eradication on a limited basis at some locations. It has to be really isolated, away from other infestations, with good conditions on the bottom of the lake."
The Darrin Freshwater Institute in Bolton Landing continues to conduct research on new ways to eliminate the invasive - but one basic strategy is just to hope for a return of hard-freeze winters.
"If there's a cold winter every other year with 90 percent die-off, that would knock the population down," Wick said. "They're a warm-water species."
It's likely that a boat coming from another body of water introduced Asian clams to the lake, where it likes shallow and sandy areas. In their larval stage, Asian clams are microscopically small, making them impossible to detect during a routine boat inspection.
The park commission and Lake George Association will be encouraging boaters to clean their anchors and other equipment frequently to prevent moving microscopic clam larvae from one part of the lake to another.
Officials said the clam situation also reemphasizes the need for inspection of boats coming into the lake from other places.
Since 2014, the park commission has had mandatory boat inspection and decontamination in an effort to prevent the arrival of more invasive species. In the last two years, the state has established similar voluntary inspection programs across the Adirondacks.
"I think this underscores the imperative for invasives prevention, the situation with Asian clams and the difficulty of containing their influence of clams on Lake George," Siy said.
Siy said the Asian clam story highlights the need for continued vigilance against invasive species all across New York state, since the Great Lakes, St. Lawrence River and New York Harbor are all prime pathways for invasive species to reach the United States.
"The Adirondacks is in the crosshairs more than any other region in the entire country," Siy said.
Reach Gazette reporter Stephen Williams at 395-3086, firstname.lastname@example.org or @gazettesteve on Twitter.