On the look out

For a decade, every boat launched into Lake Tahoe has been inspected for the presence of unwelcome hitchhikers experts say threaten to ruin a national treasure.

As officials celebrate the 10th anniversary of Tahoe’s watercraft inspection program, they cite an important success story and the importance of a continuing effort to ward off aquatic invaders.

“This program is huge for Lake Tahoe,” said Tom Lotshaw, spokesman for the Tahoe Regional Planning Agency, which initiated the inspection program in 2008 along with other Tahoe agencies.

“We’ve seen the impacts invasive species can have in other water bodies around the country,” Lotshaw said.

The program was initiated the year after quagga mussels were first discovered in Southern Nevada’s Lake Mead. Since then, the invading mollusks have spread across the lake, now numbering in the trillions.

Quagga mussels attach to docks and jetties, damage boat engines and clog water intakes, pipes and filtration systems. They can destroy fish habitat, impact water quality and litter beaches with stinking shells.

One federal study says a quagga infestation could hurt Lake Tahoe tourism to the tune of $70 million annually.

In 2008, inspections were voluntary but became mandatory in 2009. Trained inspectors examine boats at strategic locations around the Tahoe Basin like Spooner Summit, Alpine Meadows and Meyers. Over the past decade, about 75,000 motor boats, sailboats, jet skis and other vessels have been inspected, with 40 to 50 per year typically intercepted carrying some form of aquatic invasive species. Such boats must be decontaminated before entering the lake.

Without the program, funded by Nevada and California at a cost of $1.5 million per year, “there’s a good chance there would now be quagga or zebra mussels in the lake,” Lotshaw said.

The danger was demonstrated this past summer, when Alpine Meadows inspectors intercepted a pontoon boat about to the enter the lake. The boat, which came from the eastern United States, had an inconspicuous crack in a pontoon which allowed water and vegetation to enter. There were also numerous invaders, including adult quagga and zebra mussels, New Zealand mudsnails and other species.

“This incident is the perfect example of how boats are the number one transport mechanism for aquatic invasive species,” said Tahoe Resource Conservation District manager Christopher Kilian. TRCD runs the program.

Last summer, when nearly 8,000 vessels were inspected, 11 were found carrying invasive mussels and 40 harbored other unwelcome species.

“They may hide on the hull, in your bilge, on your anchor, in your ballast system, or, in this case, inside a pontoon,” Kilian said. “We’d like everyone to keep this in mind as they travel to other water bodies or prepare for inspections.”

While the introduction of mussels to Lake Tahoe has thus far been avoided, other invaders are already present. Asian clams were first noticed in southeast Tahoe in 2002 and have since spread around the lake, including to iconic Emerald Bay and Sand Harbor. Efforts are underway to control the spread of clams—which have been linked to noxious blooms of algae—but it’s not expected they can ever be eradicated.

It’s critical that efforts continue to build on the success of the last decade, Lotshaw said.

“With 10 years of no new species in the lake, we can see the program is proving its value and working,” he said.