The Aquatic Invasive Species Volunteer Surveillance Network (AIS VSN) is a community science initiative intended to enhance early detection efforts of priority AIS in the St. Lawrence Eastern Lake Ontario (SLELO) region. Early detection is a term used to describe the act of discovering invasive species populations in the early stages of introduction, before population sizes become too large to manage.


You can help by becoming a Water Protector. 

Step 1: Sign up for a training.

Step 2: Use the information on this page to familiarize yourself with our priority aquatic invasive species (AIS).

Step 3:Adopt a water‘ to survey. 

Step 4: Visit the adopted waterbody annually to monitor for AIS and report observations to NYiMapInvasive’s mobile app. 


Useful Apps That Aid Invasive Species Management

NY iMapInvasives is an online, collaborative, GIS database and mapping tool that serves as the official invasive species database for New York State.

 Click the links below to become familiar with iMap.

Below are photos taken during the Aquatic Invasive Species Learning Experience. Reach out to megan.pistolese@tnc.org for photo credit details. 

Priority AIS in the SLELO Region

The species highlighted below are considered a priority for early detection surveillance in the SLELO PRISM region. Please monitor your favorite waterbodies and report observations for these, and other, aquatic invasive species to NYiMapInvasives. 

Click the links below to view species information. 

  1. Eurasian Watermilfoil
  2. European Frogbit
  3. Fanwort
  4. Hydrilla
  5. Water Chestnut
  6. Water Soldier
  7. Yellow Iris

Overview: Invasive watermilfoil (Myriophyllum spicatum L. ) is a submerged aquatic plant native to Eurasia and northern Africa.  

Impacts:  M. spicatum L. can overwinter and overgrow in the spring, blocking out sunlight needed by native plants. It impairs the ability of some fish to spawn and is not a valuable habitat for larger fish species. 

Identifying Characteristics:  

Leaves:  submerged, feathery, limp when out of the water, 4 – 5 leaves whorl around the stem at each node.  Typically uniform in diameter consists of more than 12 thread-like pairs of leaflets that resemble bones on a fish spine.

Flowers:  tiny, inconspicuous, and located in the axils of flower bracts, either four petals or without.  Flower spike rises 2 – 4” above the water surface. Flowers are present in early summer through the fall. 

Fruit: globoid-ovoid in shape measuring 2 mm. Long with 4 lateral lobes; these lobes are smooth, except along their margins, where they may be slightly warty. Each fruit divides into 4 chunky 3-sided seeds.

Stem:  slender, thickened below the flower, doubles in width further down the stem, becomes leafless near the base. Usually, 3 -10’ long but can reach 33’ in length.  Often branch repeatedly at the water’s surface.

When to Look:  Mid-June through July. Flowers are present in early summer through the fall. 

Where to Look: Fresh or brackish water of fish ponds, lakes, slow-moving streams, reservoirs, and canals.

Overview: Frogbit is a floating perennial aquatic invasive plant native to Europe and northwest Asia. 

Impacts:  H. morsus-ranae reduces the growth of native submersed aquatic plants and has the potential to impact recreation.  Thick mats of frog-bit inhibit light penetration and hinder the movement of fish, waterfowl, and boats. Viable plant fragments can spread to new locations by boaters.

Identifying Characteristics:  

Leaves: thick, heart-shaped, 1 to 2 inches wide, and smooth-edged with spongy, purplish-red undersides.

Flowers: small, showy flowers are ½ inch across, appear individually, and have three white petals and yellow centers.

Roots: 3 to 8 inches long and unbranched, dangling from the underside of each rosette of leaves.

When to Look: During summer months. Their flowers can be seen above the water from June thorugh August. 

Where to Look: Slow-moving waters such as sheltered inlets, ponds, slow-running rivers.

Overview: Fanwort (Cabomba caroliniana) is a submerged aquatic perennial plant native to South America. Its name is derived from the fan-like appearance of its foliage. Fanwort form dense mats that impede recreation and reduce light availability for benthic organisms and native plants. This results in a reduced food supply for populations of fish and other aquatic animals.

Impacts: Fanwort  can overwinter and grow rapidly in the spring and summer, outcompeting and dominating  native vegetation. Fanwort’s dense foliage reduces light availability for benthic organisms and native plants. This results in a decline in populations of fish and other animals dependent on these native organisms. Large diebacks of fanwort can result in reduced dissolved oxygen levels that can impact populations of aquatic species. 

Identifying Characteristics:  

Submurged leaves, and have a fan-like shape with divided leafletts that split like the letter “Y” at their tips.  Floating leaves are narrow and diamond-shaped and are not as common as the submurged leaves. Leaves are green to reddish brown in color. 

Stems are slightly flattened, multi-branched, and have long petiols that are attached to submurged fan-shaped leaves. 

Flowers have six white petals with yellow stamens that bloom in late summer. 

Rhizomes grow horizonally along the sediment and are short and fragile. 

When to Look: Summer months. Flowers are present in late summer. 

Where to Look: Slow low-moving waters in streams, small rivers, ponds, lakes and ditches. Fanwort is known to be present in Kasoag Lake in Williamston, NY which connects to Oneida Lake through Fish Creek.  

Overview: Hydrilla (Hydrilla verticillata) is a submerged aquatic plant that is native to Australia, Africa, and parts of Asia.  

Impacts:  Hydrilla can invade deep, dark waters where most native plants can’t grow; it is more efficient at taking up nutrients than native species and produces turions and tubers which can easily generate new plants. These characteristics give hydrilla a competitive edge against native aquatic vegetation.  Furthermore, dense hydrilla populations block-out sunlight and suppress native vegetation. Major hydrilla colonies can alter the physical and chemical characteristics of lakes, deter recreational activities, and reduce lakeshore property values. 

Identifying Characteristics:  

Leaves: Hydrilla has pointed, bright green leaves about 5/8 inches long. The leaves grow in whorls of 3 – 10 along the stem, 5 being most common. The margins of the leaves are serrated (toothed).   

Flowers: small, floating white flowers from off thin stalks at the water’s surface.  

 Tubers: A key identifying feature is the presence of small (up to half-inch long), dull-white to yellowish, potato-like tubers that grow 2 to 12 inches below the surface of the sediment at the ends of underground stems. These tubers form at the end of the growing season and serve to store food to allow Hydrilla to overwinter. 

Hydrilla can be misidentified with our native species, elodea. Elodea does not have serrated leaves or produce tubers and is often found in whorls of 3. 



Where to Look: Hydrilla can grow in deep, dark waters and nutrient-poor areas. Look for hydrilla in freshwater lakes, ponds, and rivers. 

 When to Look: Hydrilla is easiest to find in the late summer months when water temperatures are warm enough to trigger the plant to send shoots towards the water surface. Hydrilla can often be seen growing into the late fall when many other native species have died off due to cooler temperatures. 

Overview:Water chestnut (Trapa natans) is an invasive aquatic annual plant that is native to Eurasia and Africa.  T. natans is not the same as the water chestnut that can be found in supermarkets and used in cuisine. 

Impacts: Water chestnut forms large-spanning floating mats that shade out native aquatic vegetation and impede water recreation. The pointy seeds of water chestnut can penetrate and injure feet if stepped on. Additionally, the decay of dead water chestnut populations can result in areas with reduced dissolved oxygen levels, effecting native plants, fish and other aquatic wildlife.   

Water chestnut populations can be suppressed manually. If you own waterfront property where water chestnut is growing, you can take action by talking to your neighbors and organizing a water chestnut pull or you can join hand-pull efforts scheduled to occur in your area.

Identifying Characteristics:  

Leaves float on the surface forming a rosette. Floating leaves are each 3/4th to 1 ½ inches in length, waxy, triangular, and toothed. Green, feather-like leaves up to six inches in length form in alternate pairs along the submerged portion of the stem. 

Stem are elongated and typically about a meter long but may reach as much as 5 meters in length. 

Petioles have a bladder-like swelling filled with air and spongy tissue that provides buoyancy to the floating rosette. 

Flowers are inconspicuous with their four white petals, each about 1/3 inch long, are borne singly on erect stalks located in the central area of the leafy rosette. Blooms occur in mid to late July and continue until frost. 

Seeds, also called nutlets, grow along submerged stems under the rosette and have a nut-like structure that is about an inch wide with 4 pointed edges. Nutlets begin forming in mid-summer, typically in July, they are green when immature. Each nutlet can produce 10 – 15 new plants; in turn, each rosette can produce 15 – 20 seeds.  Nutlets are easily dispersed in water and can remain viable in sediment for 12 years. 

When to look: Late June, July and August are the best times to look for water chestnut as their floating rosettes will have grown to the surface.  

Where to Look: Slow-moving water and warmer shallow waters within tributaries.  

Water chestnut populations can be suppressed manually. If you own waterfront property where water chestnut is growing, you can take action by talking to your neighbors and organizing a water chestnut pull or you can join hand-pull efforts scheduled to occur in your area.

Overview: Water soldier (Stratiotes aloides) is a submerged perennial aquatic invasive plant native to Europe and northwest Asia. 

Impacts:  Water soldier forms dense mats of floating vegetation that displace native aquatic plants and can alter surrounding water chemistry. These mats can also hinder recreational activities such as boating and fishing. Swimmers can become injured with cuts from the plants sharp serrated leaf edges. 

Identifying Characteristics:  

Leaves form in a circular rosette, each about 40 cm long, sword-shaped, bright green, with sharp spines. Leaves begin growing underwater and become buoyant during the summer months. As leaves mature in the fall, they become waterlogged causing the plant to sink below the water surface.  

Flowers are not always present but are white with three petals, and the fruit is a fleshy berry containing up to 24 seeds. 

When to Look: The emerged leaves of water soldier can be found above the water during the summer months.  

Where to Look: Water soldier is mainly found in sheltered bays of larger lakes and waterways with shallow slow-moving waters. Known populations are currently limited to within the Bay of Quinte but it is essential to survey for and detect this species early.

Yellow Iris (Iris Pseudacorus) is an invasive perennial flowering plant that is native to Europe, Western Asia and North Africa.  

Impacts:  Yellow iris forms dense monotypic stands and expands quickly via rhizomes. It can easily replace and crowd out important riparian plants causing a loss of vital habitat. Additionally, the root systems of yellow-flag iris can narrow waterways and clog irrigation systems. All parts of the plant are toxic to livestock and other animals. 

Identifying Characteristics:  

 Leaves are a dark blueish-green color, long and flat with a distinctive midrib that runs the length of the leaf. Leaves stand upright between  11-30 inches tall and have a sharp pointed tip.  

Stems grow among the leaves at the same height or taller and from multiple flower buds at the top.   

Flowers are pale to bright yellow and appear in spring to early summer. Flowers are 3-4 inches wide and have three upright petals and three larger downward pointing sepals which may have brown to purple-colored markings.   

Fruits are angular seed pods  4-8 CM long capsules. Seeds are in densely packed rows inside the capsule that harden and turn brown as they mature.   

Rhizomes are thick and fleshy 1-4 inches in diameter with a pinkish-orange color to them. The color of the rhizomes can help distinguish the invasive yellow iris from the native blue flag iris which has white rhizomes.  

When to Look:  The best time to look for yellow iris is in the spring and early summer when the flowers are present and it’s easier to distinguish between native look-alike species like blue flag iris which has a blue flower.  

Where to Look: Look for yellow iris along stream and river banks and freshwater shorelines.  


Join a 3-part learning series to become a Water Protector. 

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