[7] Zebra Mussels Found In California's Lake Mead

A colony of dreaded zebra mussels, or one of its cousins, was spotted in early January in California's Lake Mead, the huge reservoir created by Hoover Dam. The mussels have created havoc in the Great Lakes and elsewhere, decimating natural ecosystems, and proliferating in cooling system pipes in everything from nuclear power plants to Mississippi River towboats.

Until now, the tiny mussels, pretty much the number one critter on the invasive species list, have kept east of the Continental Divide, though some live ones had been intercepted on boats that were trailered west. A program called "The 100th Meridian Initiative" has been developed by resource agencies in a coordinated effort to keep them from reaching the West Coast.

The latest discovery at a marina near Las Vegas has California and Arizona agency officials stunned. Marina personnel monitor nearby waters monthly for any sign of zebra mussels. They've had several close calls. In 2004, a park service employee spotted mussels on a boat about to be put into the lake.

In ideal conditions, up to 800,000 mussels per square meter have been observed where plankton levels are high. That could limit mussel productivity in places like the Columbia River, but the news of the Lake Mead find still had Basin biologists nervous.

The news was discussed at the January meeting of mid-level policymakers for the Columbia River hydro system. "Though they're not here yet, it's only a matter of time," said Jim Ruff, hydro analyst for the Northwest Power and Conservation Council. Biologists think the mussels could grow in the intake pipes of fish passage systems at federal dams. Steps to end a potential mussel infestation at mainstem Columbia River dams could cost $20 million or more, according to a 2005 BPA study

Last September, some Columbia Basin biologists released a working draft of a rapid response plan to be ready for any future infestation. According to information in the plan, more than 100 cases were reported between 2004 and 2006 of mussels intercepted on trailered boats in western states. -B. R.

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