Friday, September 3rd, 2010

Lake Tahoe: Divers fight clams with tarps

Lake Tahoe (Global Adventures): In an effort to eradicate non-native freshwater mollusks known as Asian clams, scuba divers started to place long rubber mats suspended underwater by flotation devices across the bottom of Lake Tahoe. The clams promote so much algae growth that they can turn the blue lake water green.

Asian clams have been introduced into many parts of the world, including North America and Europe. They can self-fertilize and release up to 2,000 juveniles per day, and more than 100,000 in a lifetime. Juveniles are only a fraction of an inch (1 millimeter) long when discharged, and take one to four years to reach maturity. At this time they are about 0.4 inches (1 centimeter) long. They can reach populations of 5,000 per square yard.

Divers have already covered a south shore bay with the rubber mats in an attempt to suffocate the clams. They are planning to cover another half-acre soon. Scientists overseeing the project that will cost $1.4 million plan to keep the mats in place all summer long.

Asian clams were first spotted in Lake Tahoe in 2002. Researchers believe that the invasive species either hitched a ride on boats or trailers or originated from residential aquariums. They hope that the rubber mats will prevent the clams from reproducing and starve them of oxygen.

The mats will be removed in fall. At this time, scientists will re-evaluate the project and decide if they seek further financing to cover other sections of the lake floor in 2011. While there is little chance to eradicate the clams, they hope the efforts will help to control the species.

The economic impact of clams adds up to billions of Dollars. They can grow in such numbers that they clog water intake pipes and contribute to the decline and replacement of highly vulnerable, already threatened native clams. The species is native to Russia, Thailand, the Philippines, China, Taiwan, Korea, Japan, and parts of Africa.

Hal Sloane did upload a short video to vimeo that shows divers installing the rubber mats on the clam infested lake bottom.