Aquatic Invasive Species

The Missoula County Aquatic Invasive Species (AIS) District is the first and only county AIS district in Montana. Created in spring of 2020, the purpose of the district is to coordinate the prevention, monitoring and management of AIS within the county, as well as educate the people living and recreating within Missoula County on the identification and impacts of aquatic invasive species to the environment and our economy.

Priority Species

ais preventionPriority species that are not present in Missoula County:

  • Quagga mussels (Dreissena bugensis) and zebra mussels (Dreissena polymorpha)
  • Asiatic clam (Corbicula fluminea)
  • Flowering rush (Butomus umbellatus)
  • Eurasian water-milfoil (Myriophyllum spicatum)
  • Brazilian waterweed (Egeria densa)
  • Parrotfeather milfoil (Myriophyllum aquaticum)
  • Hydrilla (Hydrilla verticillata)
  • Yellow floating heart (Nymphoides peltata)

Priority species that are or may be present in Missoula County:

  • Red-eared slider (Trachemys scripta)
  • Snapping turtle (Chelydra serpentine)
  • American bullfrog (Lithobates catesbeianus)
  • Fragrant water-lily (Nymphaea odorata)
  • Curly-leaf pondweed (Potamogeton crispus)


Overland travel of contaminated watercraft and equipment is believed to be the single largest vector for AIS movement from one water system to the next. Watercraft Inspection Stations are located at major travel corridors and important watersheds in Montana.

Missoula County Aquatic Invasive Species District (MCAISD) in partnership with Montana Fish Wildlife and Parks staff and operated the Clearwater Watercraft Inspection Station (WIS) at the junction of Hwy 200 and Hwy 83 in Greenough, Montana.

The Clearwater WIS check all watercraft traveling East and West on Hwy 200. This station serves as a interior line of defense for our local Blackfoot, Clearwater and Swan Watersheds. It also protects the Flathead Watershed and further downstream, the Upper Columbia Watershed.

At Clearwater WIS inspectors are checking to make sure all watercraft are Clean Drained and Dry. Aquatic invasive species are transported on dirty watercraft and in standing water that can be located in boat ballast, live wells and bilge areas.

To learn more about Montana’s Watercraft Inspection program visit

ais preventionMonitoring

The early detection of aquatic invasive species is an extremely important part of our aquatic program. By searching frequently for these aquatic invaders on our lakes and rivers we will hopefully discover new introductions before they become full blown invasions.

Since 2011 Missoula County has been monitoring for aquatic plants in the Clark Fork, Blackfoot, Bitterroot, Clearwater and Swan Watersheds. Each summer we visit between 8 and 12 lakes and rivers. Using a thatch rake will pull up plants along the shoreline of lakes and rivers looking for non-native plants.

Missoula County AISD works with partners such as the Clearwater Resource Council, Swan Valley Connections, Blackfoot Challenge and FWP to ensure the monitoring for driessined mussels such as zebra and quagga mussels. This process is accomplished by pulling nets through the water column and filtering down the contents into a sample that is then sent to a lab and analyzed for microscopic larvae called veligers. These samples are often times also processed for the presence of eDNA (environmental DNA) of the mussels, a positive hit on eDNA might indicate the presence of the invasive species.

Board Meetings

Meetings are held at 4 p.m. on the third Wednesday of each month, September through May, at the Missoula County Extension and Weed District Office. Due to COVID-19, the meetings may be held virtually until further notice. Click here for more information on meeting agendas and minutes.