New Mussel Larvae Suspected in Missouri River Near Townsend

State officials have identified another possible presence of invasive mussels in Montana, this time in the Missouri River south of Townsend.

The state Department of Fish, Wildlife and Parks announced Wednesday that mussel larvae were confirmed from water samples taken Tuesday in the Missouri River near the York’s Islands Fishing Access Site.

FWP officials are searching for mussels to identify if an adult population has already been established.

The Missouri River is now the third water body in Montana that is suspected of being infiltrated by aquatic invasive species. Tiber Reservoir in north-central Montana east of Shelby tested positive for the larvae of aquatic mussels, and tests from Canyon Ferry Reservoir near Helena show “suspect” but inconclusive results.

“We are continuing to test water samples collected from the Missouri River basin, which is our area of focus now,” said Eileen Ryce, FWP fisheries division administrator.

FWP officials also identified inconclusive test results from the Milk River downstream of Nelson Reservoir. The water sample showed the presence of a larvae shell, which indicates it had dried out at some point and died, according to Ryce.

The results are inconclusive because “there’s no way of knowing if the dried larval shell came from the river itself or was brought in already dead by an outside source,” Ryce said.

Water samples from Fresno, Holter, and Hauser reservoirs have come back negative, along with samples from Lake Frances and the Marias River, according to FWP. Testing at Fort Peck Reservoir and the entire Missouri River system is ongoing. Once sample processing is complete in these close proximity areas, FWP will continue with water bodies west of the Continental Divide, according to the agency.

Local efforts are underway to study the possible presence of mussels in Northwest Montana waters, including Flathead Lake, which is considered one of the cleanest lakes in the world.

The Flathead Lake Biological Station announced this week it is immediately increasing its monitoring efforts while collecting samples across the Flathead basin to test for any possible signs of aquatic invasive species.

“If these mussels arrive in Flathead Lake, their impact will be catastrophic, damaging water quality, disrupting the food web and our trout fishing, ruining the lakeshore for recreational use, decreasing shoreline property values and increasing the cost of hydroelectricity. Our lake will never be the same,” Bio Station Director Jim Elser said in an alert newsletter published this week.

“But it’s not too late for Flathead Lake. We need to intensify our monitoring efforts on our lakes, our catchment, and incoming boats for invasive species using the best possible scientific methods, including advanced DNA technologies that are being pioneered here at the Bio Station. By comprehensively monitoring the incoming watercraft and the surrounding catchment we stand a better chance of preventing mussel invasion and in getting rid of mussels at an early stage if they get established.”

The miniscule mussels, which cling to boats and other watercraft and can colonize rapidly, threaten to have ecological and economic consequences in the last stronghold in America without a devastating infestation. Other lakes across the U.S., including the Great Lakes and Lake Mead, have fallen victim to mussel infestation, which leads to cascading effects throughout the ecosystem, including deleterious impacts to the food web and water clarity. Most noticeably, mussels promote the growth and spread of deadly algae blooms.

Once zebra and quagga mussels become established in a water body, they are impossible to fully eradicate.

At Tiber Reservoir, detection dogs searched the shoreline and docks that were removed from the water for the winter season. The dogs found a potential positive hit at one point on the shoreline and at one dock. However, no adult mussels were found, FWP said.

At Canyon Ferry, the dogs searched several docks that are still in the water and found a potential hit on a dock at the Silos and on a boat and a section of riprap at Yacht Basin Marina. These hits prompted FWP staff to snorkel around docks at both locations looking for adult mussels. U.S. Fish and Wildlife Service divers trained in searching for adult mussels continued the search this week and no adult mussels have yet been found.

To combat the possible spread of AIS, the National Park Service has temporarily closed all waters in Glacier National Park to watercraft, along with the Blackfeet Nation, which closed reservation waters to all boats. The U.S. Fish and Wildlife Service closed the Jessup Mill Pond near Creston to all boating access.

The Flathead Lake Biological Station is calling for increased investment in aquatic invasive species monitoring and prevention activities by state and federal agencies as well as nonprofit and philanthropic groups.

Montana spends roughly $1 million annually to defend against aquatic invasive species, with awareness campaigns and detection stations established during the summer. In comparison, Idaho spends roughly $10 million in the battle against AIS.

U.S. Sen. Steve Daines, R-Montana, issued a letter to the U.S. Army Corps of Engineers on Nov. 21 requesting expedited funding for increased preventative measures in Montana.

“Should the larvae propagate, it will have detrimental impacts on Montana’s ecosystem, obstruct irrigation and hydropower infrastructure, and negatively impact our economy,” Daines said in the letter.

In Montana, the FWP lab in Helena analyzes more than 540 samples from 141 water bodies across the state each year.

“We’ve developed an extensive testing protocol in Montana because of the importance of early detection,” Ryce said. “The fact we’ve discovered these mussel larvae at very low densities in Tiber and Canyon Ferry indicates this testing protocol is proving effective.”

Additionally, through the spring and summer FWP operates 17 aquatic invasive species check stations around Montana. New this year was a law requiring recreationists with watercraft to stop at any check station they encountered. More than 37,000 watercraft came through FWP’s check stations this year. Of those inspected, seven were found positive for aquatic invasive mussels.

FWP officials said the key part of Montana’s monitoring and education efforts is its “Clean, Drain and Dry” message, which encourages watercraft users to fully clean their boats and drain all water from the craft before drying it out.

“We need all of our water users to understand and follow the Clean Drain Dry message and procedures,” Ryce said. “The success we have at preventing any spread or introduction of AIS in Montana depends on it.”