April 14, 2012 in City

Dive team will investigate Asian clam infestation

Associated Press photo

A handful of Asian clams are shown after removal from the bottom of the lake in 15 feet of water near South Lake Tahoe, Calif., in 2010.
(Full-size photo)

Divers will descend Monday into Lake Pend Oreille to take a closer look at a recently discovered invasion of Asian clams.

The aggressive, nonnative species spreads quickly in lakes, rivers and canals, overtaking native invertebrates, altering habitats and spoiling beaches.

The Asian clam was found along 150 feet of shoreline in the Ellisport Bay area of Hope, Idaho, during a recent drawdown of Lake Pend Oreille. No other areas of Idaho’s largest lake have shown signs of the clam.

The Bonner County Sheriff’s Office dive team, Boundary County dive team and Idaho Department of Agriculture are teaming up to determine the distribution area of the clam. A joint dive in Ellisport Bay is scheduled for 10:30 a.m. Monday, according to Bonner County sheriff’s Detective Phil Stella, the county’s dive team coordinator.

The Asian clam, Corbicula fluminea, has spread rapidly throughout North America since it first was detected in the Western United States in 1938.

They can grow as large as a silver dollar, but those found in Lake Pend Oreille are about the size of a nickel, Stella said.

Asian clams are also found in parts of the Snake River and the Lower Columbia River. However, they appear to be most destructive in freshwater lakes, which is why officials are concerned about their presence in Lake Pend Oreille.

The clams were found in 2002 in Lake Tahoe, the Sierra Nevada lake that straddles the California-Nevada border, after they were likely inadvertently brought in by boaters.

In 2010, scuba-diving scientists unrolled long rubber mats across the bottom of Lake Tahoe coves in an attempt to quell the clam invasion, fearing the species could cloud the world-renowned cobalt waters.

The half-acre mats are designed to smother the clams, which can reach populations of 5,000 per square yard.

Geoffrey Schladow, director of the Tahoe Environmental Research Center run by the University of California, Davis, told the Associated Press that the clams promote so much algae growth that they can turn some coves from blue to green.

“They suck in the water and they filter out the algae. Their excretions are highly concentrated packages of nutrients,” he said.

After the divers learn more about the size of the Lake Pend Oreille infestation, the Idaho Department of Agriculture will work with the U.S. Fish and Wildlife Service and local officials to determine how to respond to the outbreak, said Tom Woolf, a department manager in Coeur d’Alene.

Any work proposed would have to be done in a way that doesn’t harm threatened bull trout in Lake Pend Oreille, he said.

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