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Two adult mussels and one immature specimen were found on substrate sampling gear, and the larva -- called veliger -- was found by performing plankton tows. That indicates the zebra mussels have already reproduced at least once.

"I expect the fact that zebra mussels appeared on Jan. 14, 2008, will be cited in probably a thousand plans to do with water in Colorado in the next 5-10 years," Rob Billerbeck of Colorado State Parks told attendees of the Colorado Water Congress' annual meeting in Denver last week. "I'll be shocked if it's not in the governor's 'state of the state' speech within a couple of years."

The state has been conducting field sampling efforts for several years to detect the presence of invasive aquatic species in Colorado's lakes and reservoirs. Aside from a reservoir in California, before the recent discovery at Lake Pueblo, the mussels had not been found farther west than the Arkansas River in central Nebraska.

Despite a national effort to stop the spread of the mussels, they have been successful in expanding their territory since being discovered in the United States in 1988. Officials say they probably were transported to Colorado by someone who boated in waters infested with mussels. Given their ability to attach to hard surfaces and survive out of water, adult mussels can easily spread by hitching rides on watercraft or transported in bilges, ballast water, live wells, or any other equipment that holds water.

The invasive species, native to eastern Europe, are notorious for their ability to eat large amounts of plankton, depriving native species of the food they need to survive. The zebra mussels may cause ecological shifts in the lakes they invade, with consequences to valued wildlife resources.

"They do pull a lot of nutrients out of the water column with, therefore, expected major impacts on fish populations. That has been the case in the Great Lakes. That is what we would expect in waters in Colorado," Billerbeck said.

Because these invasive mussels attach to hard surfaces like concrete and pipes, the colonies can also affect canals, aqueducts, water intakes, dams, fish ladders, fish screens and boat motors. They have been known to grow to densities of 700,000 a square meter.

"Picture all of your structures to do with endangered fish covered in a foot of mussels," Billerbeck said. He predicted that fish ladders and fish screens in Colorado could be hugely affected by the zebra mussels within five years.

Congressional researchers estimate zebra mussels cost the power industry $3.1 billion from 1993 to 1999, affecting industries, business and communities to the tune of more than $5 billion.

Pueblo Reservoir provides 52 billion gallons of water a year to several cities in Colorado, including Colorado Springs. The city is currently planning to transport even more water to its residents via the Southern Delivery System, a $1 billion pipeline project to carry water 40 miles from the reservoir to the springs.

"How are they going to affect the water delivery systems in Pueblo Reservoir? Right now, we don't know," said Peter Soeth, a spokesman for the Bureau of Reclamation.

One key to answering that question will be finding out more about just how bad the situation is in Lake Pueblo. A dive team is expected to go out to the reservoir in the next two to three weeks to determine the extent of the mussel infestation.

Officials with the statewide aquatic nuisance species working group met with Harris Sherman, executive director of the Department of Natural Resources, this week to present their draft plan to address species such as zebra mussels. Elizabeth Brown, co-chair of Colorado's aquatic nuisance species steering committee, said the group hopes to have its plan finalized by this summer, so that Colorado will be eligible for invasive species funding from the federal government.

"The zebra mussel is a great example of why this [plan] is necessary," Brown said. "The goals of the plan are to prevent new species from entering into Colorado and limit the spread of what we already have by controlling it or containing it."

Bills and bills ...

To be truly effective, though, Brown said the state needs an aquatic nuisance species program, which would require enabling legislation, and more funding, something Sherman said the state is working on.

"We have a budget request into the state Legislature to create a number of programs so that we can be more proactive in quickly stopping the introduction of species into our waters and reservoirs," Sherman said in an interview during the conference. Sherman and his staff said they are still drawing up the estimates for the budget request.

For the moment, most of the prevention efforts are focused on boater education. State Parks and the Division of Wildlife are planning a concerted effort to notify recreational users at Pueblo Reservoir and other state parks about the potential effects of zebra mussels.

The Pueblo State Fish Hatchery, located below Pueblo Dam, will undergo an assessment to determine options to prevent the spread of adult mussels and veligers. To date, no zebra mussels or larvae have been detected in the hatchery unit.

The hatchery raises a variety of warm and cold water species of fish, including walleye, crappie, smallmouth bass, rainbow and brown trout. No fish are planned to be stocked from the Pueblo Hatchery until April, and the water will be treated to eliminate zebra mussels prior to the fish being stocked.

"A plan is in place to treat the fish before they're loaded on any distribution trucks and treat the water in those trucks, which should dramatically reduce, if not completely eliminate, the risk of any kind of transport," said Greg Gerlich, Colorado's chief of fisheries.

While boater education is seen as crucial to preventing the spread of the mussels, Gerlich acknowledged that there is not much that can be done to stop an infestation. "Once [an infestation] occurs, then we may do localized treatments, but we may never be able to completely eradicate them from the system," he said.

Officials are also concerned about the spread of other aquatic invasive species, particularly the quagga mussel, which was discovered in Lake Mead last year and has since spread to six other lakes.

"In the Great Lakes, the zebra mussels have largely disappeared. They've been replaced by quagga mussels, which are their evil cousin that grow at higher growth rates, grow in deeper, colder waters, softer sediments -- all the things we have in Colorado," said State Parks's Billerbeck. "This is not good news."

Gable is an independent energy and environmental writer in Woodland Park, Colo.