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Where the Rubber Hits the Lake: Battling Tahoe's Invasive Clams

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(Sacramento, CA)
Wednesday, October 31, 2012

It's a warm, sunny day at Lake Tahoe, but the water is a brisk 54 degrees.

A team of divers is braving the chilly temperatures to lay down thick rubber mats along 5 acres of lake floor. The mats should suffocate the growing population of Asian clams in Emerald Bay.

Brant Allen with UC Davis swims over to the boat holding a handful of thumb-nail sized Asian clams he's scooped up from the lake floor sediment:

ALLEN: "I'm very optimistic here. It's the relatively early stages of this population, and we're only looking at maybe anywhere from 10 to 200 per square meter, unlike Marla bay, where we have thousands per square meter and they cover a much more vast area." 


Researchers have greatly reduced Asian clams in other parts of the lake using these rubber mats. But Emerald Bay is trickier because water currents and the permeable silt of the lake floor allow oxygen to move through even under the mats.  So researchers are adding a layer of aspen tree chips between the mat and the lake floor.  The chips should decompose and use up the oxygen faster than it flows in. 

The Asian clams can cause problems by crowding out native species, and causing algal blooms. 

Ted Thayer with the Tahoe Regional Planning Agency says an independent analysis calculated that the cost of all invasive species in the Lake Tahoe area to be about $20 million a year.

THAYER: "The longer you wait, the more expensive these things get. And so it is worth it to go ahead and make this investment. When you look at the potential economic damage from aquatic invasives species to our tourist based economy, it's certainly a worthwhile investment."

The Emerald bay project costs about $800,000 and is funded by state and federal monies.

Kim Boyd is with the Tahoe Resource Conservation District.

BOYD: "So while we are learning about how to control Asian clams in lake Tahoe-I mentioned that they are in Donner lake-we eventually hope to use that technology there."

Other nearby lakes so far appear to be free of Asian claims.  Boyd is hopeful the boat inspection program can prevent the invasives from establishing there.


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