Aquatic Invasive Species in New Hampshire
Aquatic invasive species (AIS) are plants and animals that are non-native to New Hampshire and pose big problems for our lakes. These unwanted species can hinder recreational activities, hurt the economy, cause safety problems, and negatively impact the native ecology of our lakes and ponds. Once an invasive species has established an infestation in our waters, it can be difficult to eliminate, making the cost of management practices high, sometimes hundreds of thousands of dollars. Preventing their introduction is the most cost-effective measure to address these problematic species.
How can you help?
Invasive aquatic plants and animals spread into our lakes by hitchhiking on recreational equipment like boats, trailers, and gear that have not been adequately cleaned, drained, and dried. By following the simple practices below before launching into the lake, you will do your part to stop the spread of invasive species.
CLEAN off all plants, animals, and debris from boats, trailers, and any gear that has come into contact with the water. Cleaning is the law in New Hampshire. To clean your watercraft or recreational gear, use 120°F high-pressure water, or if not available, water from the hose. Make sure runoff water does not flow into the lake. Inspect your gear for any visible plants and animals, and place them in a trash can or area where they do not pose a risk of re-entry into the water.
DRAIN all water and open drain plugs. Draining is the law in New Hampshire. When draining your watercraft, raise and lower the motor to remove all water, open drain plugs, and empty live wells. Drain water where it does not pose a risk of entry into the waterbody.
DRY for five days in the sun. If possible, leave your watercraft and gear in the sun to dry for five days, keeping compartments open to air out.
Another way invasive species enter our lakes is through aquarium dumping. Do your best to purchase native species, and never dump an unwanted aquarium into a waterbody!
What makes AIS good at being invasive?
Aquatic invasive species have abilities that allow them to grow well in our lakes and out-grow our native species. An invasive species will have one or more of the following characteristics:
- Few predators
- Ability to overtake disturbed sediments quickly
- An early start to the growing season
- Ability to blanket the surface of water, blocking sunlight
- Easily spread by hitchhiking on boats and equipment
- Ability to outcompete native species for nesting habitat and food resources
To spot an infestation, look for significant changes in plant growth and unfamiliar plants and animals. Aquatic invasive plants often grow in large, dense clumps. Depending on the plant, these clumps can be floating mats of vegetation or below the water’s surface. Invasive plants typically prefer areas of a waterbody where sunlight reaches the bottom, and where currents are slow.
Keep a lookout for the following species currently infesting New Hampshire!
Aquatic invasive plants found in New Hampshire
Curly-leaf pondweed (Potamogeton crispus)
Key Identifiers:
- Leaves are somewhat stiff and crinkled, often compared to the appearance of lasagna noodles.
- Leaves are approximately 1/2-inch wide, and 2 to 3 inches long.
- Leaves are arranged alternately around the stem, becoming more dense toward the end of branches.
- Leaves have small “teeth” along the edge.
- Plant keeps its shape when taken out of water.
- Native species lookalike: Clasping-leaf pondweed
Fanwort (Cabomba caroliniana)
Key Identifiers:
- Underwater leaves approximately 2 inches across, divided into fine branches with fan shape.
- Leaves are opposite to each other on the stem.
- Submerged parts of the plant are slimy.
- Produces small white or pink flowers sometimes accompanied by tiny, diamond-shaped leaves floating at the water’s surface.
- Leaves collapse out of the water, not keeping their fan shape.
- Native species lookalike: White water crowfoot.
Hydrilla (Hydrilla verticillata)
Key Identifiers
- Hydrilla has distinct whorls (circles) of slender, serrated leaves ¾ of an inch in size.
- Leaves are bright green with a pointed top and “toothed” edges visible to the naked eye.
- Five leaves are typically observed in each whorl but have been seen in groups of three to eight.
- Hydrilla branches profusely at the water’s surface, blanketing areas with thick vegetation.
- When taken out of the water hydrilla maintains its rigid shape.
- Native species lookalike: common waterweed
Variable milfoil (Myriophyllum heterophyllum)
Key Identifiers
- Submerged leaves of variable milfoil are finely divided, resembling a feather.
- Leaves are arranged in whorls (circles) of 4 to 6 around a thick stem which is often red in color.
- When submerged, the plant has a robust paint roller resemblance, and when removed from the water the plant collapses.
- Native species lookalike: Native watermilfoil
Eurasian watermilfoil (Myriophyllum spicatum)
Key Identifiers
- Leaves resemble a feather with blunt ends, appearing to have been cut by scissors.
- Each leaf most commonly has 12 to 24 pairs of leaflets.
- Leaves are most commonly grouped in whorls (circles) of 4, but can range from 3 to 6.
- Stems are often brown to reddish in color growing up to 8 feet in length.
- Native species lookalike: Northern watermilfoil
European naiad (Najas minor)
Key Identifiers
- Leaves are lime green, very slender and 1 to 2 inches long with 6 to 15 “teeth” along the edge.
- Leaves are usually opposite of each other with a wide base that tapers to a tip.
- The brittle, recurved leaves branch profusely at the stem.
- European naiad is a completely submerged aquatic invasive species.
- Native species lookalike: Slender naiad
Water chestnut (Trapa natans)
Key Identifiers
- Water chestnut isn’t the same Chinese chestnuts that we eat!
- From the surface, water chestnut floats similar to waterlilies but appears as a layered wheel of shield-like leaves.
- Submerged leaves are feathery and whorled (circled) around a stem that can reach 16 feet in length!
- Water chestnuts commonly form dense, rooted floating mats.
- Seeds (or nutlets) have four sharp barbs and attach under the floating plant part.
- Viable seeds are green and drop directly beneath the floating plant part, non-viable seeds are brown and can often be found on the shore edge.
Aquatic Invasive Animals Found in New Hampshire
Asian clam (Corbicula fluminea)
Key Identifiers
- Asian clams are small, round mollusks with distinct ridges on their greenish-yellow to brown shells.
- Asian clam is a bivalve (two shells) that is up to 2 inches long.
- The inside of the shell is smooth and polished with a light purple tinge.
Chinese mystery snail (Cipangopaludina chinensis)
Key Identifiers
- Characterized by their large, globular shells, typically ranging from two to three inches in diameter.
- Shells are smooth, olive green, with no color bands.
- Chinese mystery snail has a white and blue inner shell with 6 to 7 convex whorls on top of the shell.
- Has a black round or oval outer lip and can seal its opening shut with a “trapdoor” (detached in photo), allowing it to survive out of water for a prolonged period of time.
Quagga mussel (Dreissena rostriformis bugensis)
Key Identifiers
- Bivalve (two shells) up to up to 0.8 inch wide and more than 2 inches in length.
- Byssal threads (or ropes) are on the hinge edge of its shell.
- The shell usually has dark concentric rings.
- The shell color is typically paler near the hinge.
- When laid on edge the shell topples over, unlike that of its invasive species lookalike, zebra mussel.
Zebra mussel (Dreissena polymorpha)
Key Identifiers
- Zebra mussels are tiny mollusks, about the size of a pistachio and smaller, with patterned light and dark stripes.
- Adults are 1/4 to 1-1/2 inches long and have D-shaped shells, often with alternating yellow and brownish-colored stripes.
- The shell is stable when placed on its flattened hinge side.
- Can be found attached to solid surfaces in the water.
- Young zebra mussels (veligers) can travel in even just a drop of water.
Spiny water flea (Bythotrephes longimanus)
Key Identifiers
- Grows up to 0.6 inches long.
- Long, straight tail spine twice as long as its body, which protects it from predators and is a potentially dangerous food source for small fish.
- On a fishing line, spiny water fleas look like bristly gobs of jelly with black spots.
Resources and reporting invasive species sightings
Visit the New Hampshire Lake Information Mapper for information on your lake or pond, and to see if invasive species are present.
Visit the New Hampshire Department of Environmental Services invasive species webpage for information and to report potential sightings!
by Ale Consulting