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Mussel found on boat hull at South Lake Tahoe

By Jeff DeLong • jdelong@rgj.com • August 28, 2008

A boat encrusted with invasive mussels and about to be launched into Lake Tahoe was stopped in what officials describe as a first-of-its-kind close call. The harbor master at South Lake Tahoe's Tahoe Keys Marina first saw mussels on the stern of a 32-foot cabin cruiser as it was about to be hoisted into the water Friday.

Experts later confirmed the mollusks were quagga mussels, which apparently attached to the vessel while in Lake Mead in late July, said Ted Thayer, natural resource and science team leader for the Tahoe Regional Planning Agency. The boat remains under quarantine as ordered by wardens with the California Department of Fish and Game.

"This is the first one we've actually found that actually had mussels on it," said Jenny Francis of the Tahoe Resource Conservation District, which is leading inspection efforts at the lake.

The incident, Thayer said, makes clear the danger posed by mussel-infested boats and the importance of mounting a program to detect any before they are put into the lake.

"This tells us boats do come from Mead and there may be live mussels on board," Thayer said. "It is both scary and encouraging at the same time."

The vessel owner said it was decontaminated when it left Lake Mead. The area where the mussels were found were near the boat's out-drive sprayed with hot water, Thayer said. That, combined with the time the vessel was out of the water, could mean the mussels were dead when discovered at the Tahoe Keys.

"They could have already been dead, but we decided: better safe than sorry," Thayer said of the decision to put the boat under quarantine. Biologists plan to recheck the vessel Sept. 3 to ensure it is clean and can be released to its owner, he said.

Quagga mussels, previously found only in the Midwest and Northeast, were first discovered in Lake Mead in early 2007 and have since spread to other parts of Nevada, Arizona and Southern California. In January, zebra mussels -- a close cousin of the quagga -- turned up in a California reservoir 250 miles from Lake Tahoe. Both types of mussels could cause widespread problems if they were to become established in Lake Tahoe. The rapidly reproducing mollusks could quickly disrupt the lake's ecosystem, clog drinking water intakes, encrust boats, foul docks and litter beaches with sharp and stinking shells.

In June, the TRPA board approved regulations requiring mandatory inspections of boats being launched into the lake in effort to prevent introduction of mussels.