Aquatic invasive species like quagga mussels and zebra mussels are small organisms that could have huge impacts for the Greater Yellowstone Area's waters, boaters and anglers.

This issue is critical  because invasive species can hitchhike a ride on your equipment from/to other waters – ruining your favorite lakes, rivers and streams. Once established, they cause irreparable harm: introducing disease, killing off native species, competing for food, altering food chains, changing the physical characteristics of bodies of water, devastating water delivery systems, and negatively impacting local and national economies. Once introduced, they are impossible to eradicate without damaging other components of the ecosystem.

Heavy infestations of these species can ruin fisheries, alter aquatic environments by reducing food sources for game fish.  They can clog water intakes on motors, overheating and ruining boat engines.  They can also attach themselves to the prop and other areas of the motor, either affecting the performance of the engine or actually jamming steering equipment.  Aquatic invasive species can increase the operating costs of drinking water plants, power plants, dam maintenance and industrial processes.

Prevention remains our best defense against aquatic invasive species!

It's critical for the boating and angling public to fully cooperate in order to protect recreation opportunities and water supplies in the GYA and prevent the spread of these damaging organisms

Preventing introductions of potentially harmful species is the most efficient way to reduce the threat of AIS, and is a primary focus of the GYA Working Group.

What to Do?

• Clean – Clean all equipment that has been in contact with the water...
• Inspect – Carefully inspect all equipment that has been in contact with the water for any signs of unwanted materials ...
• Dry – You can kill live invaders by thoroughly drying your equipment. But you must make sure every bit of moisture is gone before you are safe

Zebra/Quagga Mussles:

Zebra and Quagga Mussels are freshwater, bivalve mollusks that typically have a dark and white (zebra-like) pattern on their shells. They are alien to North America but have invaded many of our waters, east of the 100th Meridian. There are two species of Dreissena in North America: Dreissena polymorpha, commonly called "Zebra Mussels" and Dreissena rostiformis bugensis, commonly called "Quagga Mussels." Despite some minor morphological and ecological differences, both species are very similar and pose a significant threat to our waters. Both species, Zebra Mussels and Quagga Mussels, in general, are usually about an inch or less long, but may be larger. When healthy, they attach to hard substrates much like marine mussels but unlike any native freshwater bivalve. They are often found in clusters.

Zebra Mussels (size = about 3/4 inch each)

Enlarged Photo of a Quagga Mussel (size = about 3/4 inch)

Informational Brief on Western Quagga Mussels (407 KB PDF)

Map on the Western Distribution of Quagga Mussels (1.1MB PDF)

New Zealand Mud Snails:

 New Zealand mudsnails are relatively small (average length of 4-5 mm in western USA), with a maximum of 11 mm in native habitats. They reach maturity at 3 mm in length in rivers in western Monta
na, Idaho and Wyoming. Their shell usually consists of a right-handed coiling of 5-6 whorls. The shell varies in color (gray, light to dark brown). An operculum (i.e., plate) covers the opening of the shell. New Zealand mudsnails have triploid, parthenogenetic female populations: asexual females are born with developing embryos in their reproductive system. Diploid, sexual male and female populations are extremely rare in western USA. Asexual females generally produce twice the number of daughters as sexual females. The adult New Zealand mudsnail may easily be confused with various native and exotic species which can be similar in appearance, and all newly discovered populations should be verified by experts. The shell of the New Zealand mud snail is narrower, longer, and has more whorls than most hydrobiid snails native to the United States. New Zealand mud snails are live bearers (they release embryos and not eggs), and therefore, the presence of newly released young may indicate a possible population.

New Zealand mudsnails can inhabit lakes, ponds, streams, rivers, lagoons, estuaries, canals, ditches, water tanks, and reservoirs and occupy a wide variety of substrates including silt, sand, mud, concrete, vegetation, cobble, and gravel. They are capable of tolerating a wide range of temperatures with upper thermal limits of 28°C and lower thermal limits near freezing. The also have a wide salinity tolerance range from saline and brackish to freshwater. Populations in saline conditions produce fewer offspring, grow more slowly, and undergo longer gestation periods. Individuals of this species are able to tolerate turbidity, clear water, and degraded conditions (including sewage and may pass through the digestive tracts of many fish species.

More Information on Species of Concern>>

  Species of Concern 

(as designated by a panel of scientists in the Greater Yellowstone Area  in the 2009 Inventory and Monitoring Framework Document)