In addition to Lake Granby reservoir, invasive mussel larvae has been detected in natural Grand Lake, in Shadow Mountain Reservoir and Willow Creek Reservoirs in Grand County.
Results from an independent laboratory confirm that both zebra and quagga mussels are present in Grand Lake, while only quagga mussels have been found at Willow Creek, Shadow Mountain and Lake Granby, according to the Colorado Division of Wildlife.
Quagga mussel larvae were discovered in Lake Granby earlier this summer. Shadow Mountain and Willow Creek reservoirs, as well as Grand Lake, are physically connected to Lake Granby.
Identified by a microscopic analysis of water samples, the larvae was confirmed as invasive mussels by DNA testing.
Zebra and quagga mussels are closely related species that have similar biology, impacts and mechanisms for spread. Zebra and quagga mussels are small barnacle-like mollusks with dark- and light-colored stripes.
They usually spread to other lakes by hitchhiking in motorboat engines, or by attaching themselves to boat trailers.
Although, individually, they appear harmless, their ability to adapt and rapidly multiply and spread has experts baffled.
In other parts of the country, large fish declines have resulted because mussels remove plankton from fresh water and smother bottom dwelling organisms.
They are also prolific reproducers.
Up to 1 million eggs can be laid by a single female mussel in a spawning season.
"Zebra Mussel densities have been reported to be over 700,000 individuals per square meter in some facilities in the Great Lakes area," states the 100th Meridian Initiative Web site, the aim of which is to help stop the spread of invasive species (http://www.100thmeridian.org/zebras.asp). "Monitoring and control of Zebra and Quagga Mussels costs millions of dollars annually."
The invasive mussels originally spread from Eurasia to northeastern United States in the 1980s by way of the Great Lakes in contaminated ballast water of ships, on anchors and anchor lines.
They quickly spread to the Mississippi River - from Minnesota to Louisiana - its tributaries and inland lakes.
They have now established a presence in the Western states. In Colorado, monitoring also confirmed the presence of both zebra and quagga mussel larvae in Lake Pueblo.
Adult mussels litter beaches with shells and damage equipment by attaching to boat motors or hard surfaces and clog water treatment facilities.
"Zebra mussels represent one of the most important biological invasions into North America, having profoundly affected the science of invasion biology, public perception, and policy," states the United States Geological Survey.
How can a lake be rid of them? The short answer is, it can't.
"There is no known control method," said Invasive Species Coordinator for the Division of Wildlife Elizabeth Brown.
But there does exist a small sliver of hope for the Colorado Big Thompson lakes.
It's still a big question mark whether the mussels will be able to achieve large densities of adults, Brown said.
"We truthfully don't know how these species are going to behave in Colorado," she said. "They've never been found in waters like this before anywhere in the United States. We don't know if they can sustain a population here."
The species can live as deep as 300 feet. So, whether a reproducing population already exists somewhere in the four lakes is also still unknown, she said.
Calcium is needed for maturing mussels to grow shells. Against the mussels' favor, high-elevation lakes do not contain a lot of calcium.
On top of that, cold high-country lake temperatures could result in short breeding seasons.
"We're hoping they do not achieve high reproductive success because the habitat is not conducive," Brown said.
Brown added that adult mussels are not likely to survive in the upper Colorado River because they tend to avoid moving water.
Their prevalence in the Mississippi River is attributed to a great number of dams, levies and other stops along the way, she said.
They've already been found in the lower Colorado River and in Nevada and California lakes.
For those who keep their boats seasonally moored, in boat houses or attached to docks, the presence of adult mussels would mean a stricter protocol of motor-boat maintenance on the lakes that make up the C-BT.
"Once the adults (mussels) start showing up, it's going to mean people are going to have to monitor and check boats more frequently," said Jerry Neal, spokesperson for the Division of Wildlife. "Owners who store their boat on the lake in marina slips or boathouses should inspect and remove their vessel from the water regularly to ensure that mussels have not attached to their motor or propellers. Mussels can plug water intake ports, causing outboard motors to overheat and possibly seize."
And hope is not yet lost for other lakes in Colorado.
Public awareness and participation is the best weapon in the containment of invasive species.
Boaters are reminded to take the simple precaution of making sure that they "Clean, Drain, and Dry" their boat when they leave any of the C-BT lakes: Willow Creek Reservoir, Lake Granby, Shadow Mountain Reservoir and Grand Lake.
All boaters should remember to follow these steps to ensure they are not spreading the mussels to clean waters elsewhere:
DRAIN the water from the vessel, live well and the lower unit of the engine.
CLEAN the hull of the vessel.
DRY the vessel, fishing gear and other equipment.
INSPECT all exposed surfaces.
REMOVE all plant and animal material.
"We need to keep the critters from taking over all the water bodies in Colorado," Brown said.
For more information about zebra and quagga mussels visit www.wildlife.state.co.us/WildlifeSpecies/Profiles/InvasiveSpecies/ZebraandQuaggaMussels.htm.
- Tonya Bina can be reached at 887-3334 ext. 19603 or e-mail firstname.lastname@example.org.