The fight against zebra and quagga mussel invasion continues

By Caitlin Mitchell, Program Assistant and Field Technician

On a cloudy day in September, with the sky threatening rain, I met with Rob Rich from Swan Valley Connections at the Upsata Lake boat launch. Rain or shine, we were here for business, joined by dedicated volunteer Barry Gordon and his trusty old skiff. Thus began the 2018 aquatic invasive species (AIS) lake monitoring season for the Blackfoot Challenge, Clearwater Resource Council, and Swan Valley Connections. Working collaboratively along with the Missoula County Weed District, this spring we set out to monitor and collect samples from 13 lakes across the two watersheds for Dreissenid mussels, the family for both zebra and quagga mussel species.

Caitlin Mitchell and Brooke Schoonen collecting water samples on Coopers Lake. Photo by Jennifer Schoonen.

While limited funding cut this year’s monitoring trips to half of the number completed in 2017, the protocol remains vigorous, testing our most vulnerable lakes each three times for microscopy analysis and twice for environmental DNA analysis. In the Blackfoot Valley that testing includes Upsata, Coopers and Browns lakes. The microscopy analysis done by Fish, Wildlife and Parks uses a process called cross-polarized light microscopy to detect the mussel larvae, named veligers. Environmental DNA (eDNA) analysis done by the Flathead Lake BioStation, extracts DNA from cells in a water sample and processes it to see if the DNA matches that of  zebra or quagga mussel. These cells can exist in a water body for a short period of time even if mussel adults or larvae have departed, much like a human leaving skin or hair cells at the office once they’ve left for home.

While the state is sticking to using microscopy analysis, other agencies that manage lands adjacent to the lakes we monitor and lake homeowners associations provide funds for eDNA analysis. Utilizing both detection processes enables us to be as far ahead of a potential mussel infestation as possible, so if zebra and quagga mussels do invade we discover them early enough to try to contain.

Every offense requires a strong defense, and our proactive monitoring is very much complemented by the state’s increase in watercraft inspection stations to box out infested boats from entering our waterbodies. Montana has more than doubled the number of watercraft inspection stations in the last two years, going from 21 stations in 2016 to 46 stations in 2018. Following Labor Day weekend, some of those stations closed up shop for winter, but others will remain open until the end of October. Two watercraft inspection stations live within the Blackfoot watershed: one at the junction of MT Highway 200 and MT Highway 83 will shut down after Labor Day, and the second located east of Lincoln will remain open until October 14.

Watercraft inspection station. Photo courtesy

As of July, more than 50,000 watercraft have been inspected. Twelve of those were identified as hosts of adult Dreissenid mussels. When a boat is found to harbor mussels, the watercraft inspectors decontaminate the vessel with a minimum five-minute power wash of 100 degree F water, lock the boat to its trailer, and notify the destination state or province where the boat is headed. Most of the “mussel boats” were passing through the state headed for Idaho, Washington, or Canada coming from California, Arizona, or the Great Lakes. Six of these 12 watercraft were newly purchased and being transported to their new owners.

Aside from actively monitoring our vulnerable lakes in the Blackfoot to help prevent AIS spread from east of the Continental Divide into the Columbia River Basin, the AIS monitoring partners aim to raise public awareness about the threat that AIS pose. Dreissenid mussel adults are highly invasive, attaching to any substrate they can find with their foot of byssal threads, including each other. This can create walls of mussels inches deep covering shorelines, watercraft bilges, and docks, clogging hydroelectric dams, irrigation pipes, water intake channels, and fire hoses. In a landscape where surface water not only supports recreation, but also sustains agriculture and protects communities from wildfire, your help in protecting our watershed from these AIS is as important as ever. Clean your gear, drain your boats and pipes, and let it all dry out before moving to the next waterbody. Clean, Drain, Dry, and encourage your friends to do the same.

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