Aquatic Invasive Species

FOAM was among the first groups to hear about the Whirling Disease discovery in the mid-90’s, and we were involved from the beginning in helping educate our members and other anglers about the characteristics, consequences, and management of this debilitating threat to our fisheries.

Now, aquatic nuisance species, AIS, pose a threat to our recreational fisheries via contamination from infected waters in other states. Our best defense is preventing their introduction in our waters.

Which AIS threaten Montana?

Zebra Mussels

Tiny and prolific, Zebra Mussels strain nutrients from the water column, denying food for other aquatic species and completely covering rocks and gravel.

Introduced to the Great Lakes in 1988 from discharged ballast water carried by ocean-going ships, they quickly took hold, clogging water intakes and smothering native lake mussels.

In Montana, zebra mussels block irrigation and filter-plant intakes and reduce food for aquatic plant and insect species that, in turn, feed the recreational fish that sustain our industry.

A recent discovery of bacteria that can kill zebra mussels may be a break in the battle against this tiny AIS.

Quagga Mussels

Larger than Zebras, Quagga Mussels  have the same origin and effect on other aquatic species.

Unfortunately, Quaggas have taken hold in Nevada’s Lake Mead, just down Highway 93 from Flathead Lake. The Flathead Lakers organization is working hard to prevent their introducion into northern Montana.

Eurasian Milfoil

Eurasian Milfoil reproduces by fragmentation, with the broken stem pieces quickly sprouting new arms. Milfoil can form mats that block sunlight from other native aquatic plants, eventually replacing them completely.

First introduced in Wisconsin in the ’60’s, by 1993, it had overcome some 75 Wisconsin lakes and portions of the upper Mississippi and shallow bays in Lake Michigan and Lake Superior.

As a hitch-hiker on traveling watercraft towed into Montana by visiting receationists, Eurasian Milfoil has been reported in Broadwater, Flathead, Gallatin, Jefferson, Lake, Sanders, and Valley counties.


Another aquatic invasive, Didymo is a diatom that can blanket a streambed, covering all surfaces, smothering buried insects, and severly reducing availability of water-born nutrients. Appropriately called “Rock Snot”, Didymo is particularly slimy, and because it’s basic living unit is very small, it can be transported easily from one waterbody to another on boots, fishing gear and watercraft.

Currently, Didymo is present in Idaho, Kentucky, Maryland, New York, New Hampshire, South Dakota, Tennessee, Vermont, Virginia, and West Virginia.

This is only a partial list of the AIS that may be transported to Montana on wading gear and watercraft. Other invasive aquatic plants are common in other states, but these three species are of particular concern right now.

Prevention is our best defense!

FOAM teamed up long ago with key organizations like Montana FWP, the Invasive Species Action Network, ISAN, and their sister group, the Clean Angling Coalition, to help educate outfitters, guides, our clients, and other anglers about AIS and their potential effect on our fisheries and recreational waters.

Since 2007, we’ve urged our members to follow the simple protocol – Inspect, Clean, Dry – developed by MTFWP in cooperation with other angling and conservation organizations. Taking a few moments to clean your wading gear and watercraft before going to or leaving any stream, lake, or reservoir will nearly eliminate the spread of AIS to other Montana waters.

Many of our members ask their clients to leave their wading gear at home and provide clean gear for them to use while enjoying Montana. Others have set up gear- and boat-cleaning stations, using pressurized water to spray off any mud and debris, making sure the runoff doesn’t contaminate any nearby waters. A few have even installed freezers where they keep their client’s wading equipment overnight to disinfect any possible hitchhiking invaders.

For more information on the nation-wide effort to prevent AIS, check the Protect Your Waters campaign.

We also urge anglers to take the Clean Angling Pledge and remain active in preventing the introduction of AIS to Montana.