Outlaw mussels invade the West

This post contributed by Adele Conover, a freelance science writer specializing in natural history. On Halloween night 2005, an anonymous trickster left a jar crammed with zebra mussels on the doorstep of the Charles M. Russell Wildlife Refuge office in Lewiston, Montana. Dr. Eileen Ryce, Montana Fish, Wildlife and Parks Aquatic Nuisance Coordinator, was stunned. “We assume that the anonymous someone knew what a threat zebra mussels pose.” However, there’s been no sign of the zebra invader in Montana waters, or unfortunately the perp’s identity.   At that point neither the mussel nor its equally notorious cousin, the quagga, had crossed the Continental Divide as far as anyone knew.  (Today, despite a recent scare in Flathead Lake, Ryce notes, Montana is still free of these mussels). Other western states have not been so lucky. Two years later on January 7, 2007 a sharp-eyed marina employee at Lake Mead (which straddles the Arizona-Nevada border) spotted what he thought was a single zebra mussel attached to a cable anchoring a breakwater.   But, the lone mussel was not a zebra, but a quagga that had slipped into the huge lake with nary a splash. It was the first discovery of an invader mussel west of the Continental Divide. Divers rapidly discovered many more quagga, which soon migrated down the Colorado River into Lake Mojave and Lake Havasu on the California/Arizona border. The California-bound Colorado River water flows out of Lake Havasu via the Colorado River Aqueduct to California. By March 2007, much to the alarm of the Metropolitan Water District of Southern California, quaggas were “coursing” down miles of concrete-lined canal surfaces in the California Colorado River Aqueduct system. “As a remedy,” says Bob Muir, Public Information Officer for the Water District, “we shut down major stretches of the 242-mile Colorado River Aqueduct to dry out the system during the last ten days of July 2007”—to little avail. Now, according to the Metropolitan Water District’s Microbiology Unit Manager, Dr. Ricardo De Leon, all the southern California reservoirs, lakes and watersheds receiving Colorado River water are infested. (Periodic shut downs of the Aqueduct continue to be part of the Water District’s efforts to contain the quagga.)   The Lake Justo Reservoir in Northern California’s San Benito County hosts only zebra mussels. As Lake Justo is not on the Colorado Aqueduct system, biologists believe that this infestation arrived via trailered recreational boats. The mussels, master filter feeders not only roil ecosystems but clog intake openings and other structures of water systems.  Officials in the Midwest and Northeast have spent billions to rid the waters of the scourge yet they persist.  The invaders also disrupt the aquatic food...

Read More