ABSTRACT
ABSTRACT Once introduced into North America in the 1980s, zebra mussels (Dreissena polymorpha) spread quickly through an arti‘cial connection from the Great Lakes into the Mississippi Riversystem. From there, navigable waterways provided conduits for invasion into much of the eastern United States. Conservation agencies in the West expected zebra mussels to threaten their waters too, but limited resources, personnel, and other factors constrained prevention efforts. Meanwhile, quagga mussels (Dreissena bugensis), which were not notorious for spreading beyond the Great Lakes, slipped past our defenses and entered the lower Colorado River sometime before 2007. Once introduced, spread was rapid, again, through arti‘cial water connections. The Colorado River Aqueduct brought quagga mussels rapidly into Southern California, while the Central Arizona Project carried them into Arizona. The extent of the current quagga and zebra mussel distribution is largely a re¬ection of the navigable waterways in the East and the aqueduct and canal systems in the southwest. These pathways are largely uncontrollable. Western agencies have focused efforts, instead, on preventing overland transport of invasive mussels on boats carried on trailers. Only ‘ve states in the West have found evidence for dreissenid mussel introductions: California, Utah, Nevada, New Mexico, and Colorado. The introductions in Colorado, New Mexico, and Nevada (except for the original introductions in the lower Colorado River) have not developed into successful invasions. By 2013, all Western states have recognized the serious nature of existing and potential invasions. Many states have enacted new laws and stepped up prevention and containment programs. This chapter highlights some of the management actions taken in response to quagga and zebra mussel discoveries in the West and some of the obstacles that we have
How Mussels Spread to North America ..................................................................................................... 4 How Mussels Spread to the West ............................................................................................................... 5
California .............................................................................................................................................. 7 Colorado ................................................................................................................................................ 7 Utah ....................................................................................................................................................... 8 Nevada .................................................................................................................................................. 9 New Mexico .......................................................................................................................................... 9
WhatWe Are Doing about the Problem ................................................................................................... 10 Early Detection ....................................................................................................................................11
