Aquatic Invasive Species Prevention Update
Montana Fish Wildlife and Parks recently published information about statewide efforts to prevent the introduction of Aquatic Invasive Species into Montana waterways including the Flathead Watershed. Below is a summary of activities that took place in 2025.
Prevention / Watercraft Inspection:
Over 119,000 watercraft have been inspected this season.
38 mussel fouled watercraft have been intercepted to date and more than 570 have been intercepted transporting aquatic weeds.
Roadside watercraft inspection stations are closed for the season. Stations will open again in March 2026. Inspections are available by appointment through the winter at FWP regional offices. To arrange for an inspection call 406-444-2440.
Of particular interest to the Lakers, the Flathead County Conservation District posted volunteers at the Somers Fishing Access Site on weekends during the summer months to ask questions to boaters departing and landing at the site. The volunteers 124 watercraft that failed to meet mandatory AIS inspection requirements prior to launching in Flathead Lake. 124 watercraft, from one site, only on weekends during the summer months. This is a huge threat to the health of the watershed. We must remind our friends, family, and visitors from outside of the watershed to get their boats inspected and do their part to prevent the accidental introduction of damaging species like Zebra and Quagga mussels.
New AIS detections in 2025 include:
New Zealand mudsnails at new locations in Alder, Bozeman, Bearmouth, Billings, Bridger, Dillon and Warm Springs
Curlyleaf pondweed at new locations in Billings and Chinook.
Red rim melania snails at new locations in Chico, Bearmouth and Alder.
Facet snails at a new location at Seely Lake.
Finally, Zebra mussels have been discovered in Sheridan Reservoir in the Black Hills, the second western South Dakota water body confirmed with this invasive species, following the earlier case at Pactola Reservoir in 2022. South Dakota Game Fish & Parks (GFP), working with federal agencies, reported that in 2025 over 1,600 boat inspections were conducted at Sheridan and emphasized the increased risk posed by mussel larvae this time of year. GFP is urging all boaters and lake users to follow the “Clean, Drain, Dry” protocol, remain vigilant, and report any sightings of invasive mussels to help prevent further spread.
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