Need a field guide?
There are many great AIS identification books for free and for sale. Washington
Department of Ecology has published
An Aquatic Plant Identification Manual, available for free online or
and Riparian Weeds of the West is available for purchase.
This easy-to-use photo page shows 6 possible AIS that might be
found in lakes and slow moving water bodies. It can be used to identify common
characteristics of the plants.
Below are some aquatic invaders to be on the
Photo Identification Section
Zebra and Quagga Mussels
(Quagga) and Dreissena polymorpha (Zebra) are destructive
invasive aquatic species native to the Ukraine and Russia. These mussels
are highly destructive in freshwater systems because they can:
- Reproduce quickly and in very large numbers, up to 1 million larvae per spawning season.
- Colonize on both hard and soft surfaces, from the water's surface to more than 400
feet down, including boat hulls, propellers, anchors, docks, and boat trailers.
- Coat submerged surfaces such as piers, pilings, rocks, cables, boat ramps, docks,
lines, pipes and fish screens which increases operation and maintenance costs.
- Infiltrate and damage boat engines, bilges, live wells, and steering components.
- Threaten the state's municipal water supplies hydroelectric plants, reservoirs and irrigation systems.
- Clog municipal water intake structures and obstruct the flow of drinking water.
- Cost taxpayers millions of dollars to repair damaged pipes and water transport facilities.
- Wreak havoc on the environment by disrupting the food chain by filtering the
water column of phytoplankton and depriving fish of a food source.
- Change water conditions, causing heavier aquatic plant growth, oxygen loss, and fish kills.
- Result in infested waters being closed to boating and fishing altogether.
Quagga/Zebra mussels pose serious risks and costs to you as a boat owner because they can:
- Ruin your engine by blocking the cooling system and causing overheating.
- Increase drag on the bottom of your boat, reducing speed, and wasting fuel.
- Jam your boat's steering equipment.
- Require you to scrape and repaint your boat's hull.
Only freshwater mussel in North America that clings to substrate (If you see a striped
mussel attached to anything, it is likely a zebra or quagga mussel) REPORT IT!!!
Adults range in size from the size of a grain of rice to one inch.
Plants. DO NOT SPREAD THESE SPECIES!
Montana ANS Priority Class 1
Aquatic plant from South America, Brazillian elodia was imported from the aquarium trade.
It has few natural predators to keep its growth in check and can displace native plants.
Once introduced it can form dense mats that are unsightly, interfere with recreation,
and degrade fish habitat.
- Similar to hydrilla
- Submersed aquatic weed, found in ponds, lakes, streams and rivers
May reach 6 feet in length and are freely branching
- Leaves occur in whorls of 3-6, most commonly 4
Individual leaves are 1-1 ¼ inch long, 5 mm wide
- Finely toothed leaf margins
- Undersides of the leaf midribs are smooth and without teeth unlike those of hydrilla
- Flowers have 3 white petals and 3 green sepals
- Flowers appear at water surface on long stalks, showy flowers petals are 1/3 inch long
Montana ANS Priority Class 1
Introduced from Asia for use in aquariums, this plant spreads by fragmentation and
via transport on boats, motors, trailers, fishing nets and other gear, and aquarium or water garden release.
- Grows thick mats especially in shallow water
- Quickly takes over shallow lakes and rivers, preventing boating, fishing, hunting, and swimming
- Clogs irrigation canals
Difficult to identify, sometimes confuse with Elodea or Egeria
- Sharply toothed leaves in whorls of 3-8
- Sometimes possess small teeth along underside of leaf midrib
Montana ANS Priority Class 3
Eurasian watermilfoil, right, is much denser than native norther watermilfoil, left.
- Spreads by fragmentation, currents and waves, and overland via transport on boats,
motors, trailers, fishing nets, and other gear
- Grows thick mats in waters less than 15 deep
- Eradication is nearly impossible
- Can quickly take over shallow lakes and rivers, which can prevent boating,
fishing, hunting, and swimming
- Submersed, perennial, aquatic plan with feathery leaves arranged in whorls around the stem.
- Found growing in shallow water to 25 feet deep or more.
- Tops often turn read in color.
- Milfoil stems branch several times near the water surface.
- Erect stalks emerge above water with small reddish flowers.
- Typically 4, but sometimes 3-5 leaves, form a whorl around the stem.
- Each leaf has 12 or more pares of leaflets.
Montana ANS Priority Class 4
This plant is native to Eurasia, Africa and Australia. By 1950 most of the U.S. was
infested by this species. Curlyleaf pondweed forms dense mats which interfere with recreation and
limit the growth of native aquatic plants. In shallow lakes it can grow dense enough to
affect recreational boating and fishing. It can alter nutrient dynamics of a fertile
lake causing heavy summer algal blooms.
- Leaves are alternate with crinkled leaves that are finely toothed
- Most often found in ponds with fertile, hard water
- Flower spikes often stick up above the water surface during spring
- Tolerates low light and may grow in deep water
Montana ANS Priority Class 4
An emergent in shallow areas of lakes, flowering rush has umbellate pink flowers and grows
to 3 feet tall on triangular stems. Flowering rush was introduced as an ornamental.
- Flowers grow in umbrella shaped clusters and each individual flower
has 3 whitish pink petals
Plants only produce flowers in very shallow water or on dry sites
- Green stems resemble bulrushes but are triangular in cross section
- Leaf tips may be spirally twisted
- Along shores, has erect leaves and grows to about 3 feet in height
- Forms an extensive root system that can break into new plants if disturbed