Aquatic Invasive Species (AIS) Photo Gallery

Listed below are some of the top aquatic invasive species for which we are constantly monitoring our lakes. If you have noticed any of these species while you've been out on our waterways, please fill out the brief AIS form - it will alert the appropriate people at Montana Fish, Wildlife and Parks so they can follow-up. Thank you for your support.

Curly-leaf pondweed (Potamogeton crispus) is an aquatic perennial native to Eurasia, Australia, and Africa. The leaves of this rooted, submerged plant are olive green to red-brown, oblong, and finely toothed with wavy margins (~ 8cm long and 1.5 cm wide). Leaf tips are rounded, and stems are flat and alternately branched. Typically found in water less than 3 meters deep, it is tolerant of low light and low water temperatures and can be found up to 18 meters deep.

Inconspicuous, unbranched, and erect flower spikes of 1-2 cm long grow above the water surface in spring to early summer. The majority of reproduction occurs from turions (burr-like winter stem buds) that are present in fall and winter and are usually terminal on a stem or in leaf axils.

The early spring growth of Curly-leaf Pondweed shades-out and inhibits native aquatic plants. This growth can result in dense mats that inhibit boating and swimming. Once the plant dies-back (becomes dormant) in mid-summer, the decay depletes oxygen in the water, potentially encouraging algal blooms.

Eurasian watermilfoil (Myriophyllum spicatum) is a submersed aquatic plant native to Europe, Asia, and northern Africa. Like the native milfoils, the Eurasian variety has slender stems whorled by submersed feathery leaves and tiny flowers produced above the water surface. The flowers are located in the axils of the floral bracts, and are either four-petaled or without petals.

The leaves are threadlike, typically uniform in diameter, and aggregated into a submersed terminal spike. The stem thickens below the inflorescence and doubles its width further down, often curving to lie parallel with the water surface. The fruits are four-jointed nut-like bodies. Without flowers or fruits, Eurasian watermilfoil is nearly impossible to distinguish from Northern watermilfoil.

Eurasian watermilfoil has 9-21 pairs of leaflets per leaf, while Northern milfoil typically has 7-11 pairs of leaflets. Coontail is often mistaken for the milfoils, but does not have individual leaflets.

Flowering rush (Botomus umbellatus) is a perennial aquatic herb that emerges each spring from winter-hardy rhizomes. Emergent leaves are stiff, narrow, sedge-like (3-edged or triangular in cross-section) and up to 3 feet above the water surface. In deep water, the plant can be entirely submerged. Submerged plants have limp leaves and do not flower. Often unnoticed among other wetland plants until it blossoms, flowering rush has a distinctive spray of attractive white, pink, or purple flowers on a tall stalk. Blooming in late summer to early fall, flowers have 3 petals, 3 sepals and red anthers.

Fragrant water lily

The fragrant water lily is an aquatic plant with large, radially symmetrical white or pink blooms and heart-shaped glossy green floating leaves with a purple underside. The leafstalk is submerged grows out of large rhizomes which serve as a common food source for muskrats .The flowers range from 3-15 inches wide with several broad, curved petals that narrow toward the center. The center has one pistil that is densely packed with bright yellow stamens.

They are found in still, relatively shallow water (5-7 ft.) in water bodies such as lakes and ponds with silty beds. It is the most common white water lily. Native to the eastern portion of North America, its commercial popularity has caused its extensive dispersal throughout North America. The plant is now considered a secondary invader that can achieve extraordinary population growth and destabilize ecosystems.

New Zealand mudsnail

The New Zealand mudsnail (Potamopyrgus antipodarum) is a small aquatic snail.  As its name states, this species is native to freshwater lakes and streams of New Zealand.  Like many organisms today, it is being incidentally carried to many locations around the world such as Europe, Asia, and North America. In the U.S., this snail was first detected in the mid-1980s in the Snake River region of Idaho.  Since then, it has spread to waters of Montana, Wyoming, California, Arizona, Oregon, and Utah. They have even found their way into the waters of Yellowstone National Park.  The only known population in the eastern U.S. is in Lake Ontario where a population was discovered in the early 1990s.

Mudsnail densities of over one-half million per meter square in western streams are a cause for concern. Because the West is known for abundant trout and productive fishing spots, there is concern that the mudsnails will impact the food chain for native trout and the physical characteristics of the streams themselves.  Research is needed to determine the impacts of large populations of mudsnails on the native fauna, such as aquatic insects and native snails, and on any changes in the physical environment. 

The Quagga mussel (Dreissena bugensis) is a mollusk native to parts of Ukraine. This small freshwater mussel is an active filter feeder, which competes for food resources with filter-feeding zooplankton by accelerating sedimentation of suspended matter, including organic substances. It is also a nuisance and economic problem when it grows on recreational or commercial ships/boats, potable water treatment plants and electric power stations. Quagga mussels commonly have alternating light and dark brown stripes, but can also be solid light brown or dark brown. They have two smooth shells that are shaped like the letter “D”.

These mussels are usually less than 2 inches in length. In new populations, most mussels are young and therefore very small (under ¼ inch long). There are two phenotypes of D. bugensis that have been reported in the Great Lakes: the "epilimnetic" form, which has a high flat shell, and the "profunda" form, which has an elongate modioliform shell and has invaded soft sediments in the hypolimnion. The epilimnetic form uses its byssal threads to attach to objects and particles and form druses or colonies. The profunda morph can form colonies and attach to objects with its byssal threads or it can partially bury itself in soft sediments and extend its very long incurrent siphon above itself to bring in suspended food particles.

The Zebra mussel (Dreissena polymorpha) is a tiny (1/8-inch to 2-inch) bottom-dwelling clam native to Europe and Asia. Zebra mussels were introduced into the Great Lakes in 1985 or 1986, and have been spreading throughout them since that time. They were most likely brought to North America as larvae in ballast water of ships that traveled from fresh-water Eurasian ports to the Great Lakes. Zebra mussels look like small clams with a yellowish or brownish D-shaped shell, usually with alternating dark- and light-colored stripes. They can be up to two inches long, but most are under an inch. Zebra mussels usually grow in clusters containing numerous individuals.


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