Asian clams (Corbicula fluminea) Image by Center for Lakes and Reservoirs/CC BY-NC 2.0
Chinese mystery snails (Cipangopaludina chinensis) Image by Sankax/CC BY-NC 2.0
Common carp (Cyprinus carpio) Image by Lonny Holmes/CC BY-NC 4.0
Koi (Cyprinus carpio)
Red swamp crayfish (Procambarus clarkii) Image by Ferran Pestaña/CC BY-NC-SA 2.0
Rusty crayfish (Orconectes rusticus) Image by Nicholas Pollock/CC BY-NC 4.0
Zebra mussels (Dreissena polymorpha) Image by Jenny Smith/CC BY-NC 4.0
Common reed (Phragmites australis) Image by rll97/CC BY-NC 4.0
Curly leaf pondweed (Potamogeton crispus) Image by Sean Blaney/CC BY-NC 4.0
Eurasian water milfoil (Myriophyllum spicatum) Image by Carla Corazza/CC BY-NC 4.0
Flowering rush (Butomus umbellatus) Image by Bob Heitzman/CC BY-NC 4.0
Purple loosestrife (Lythrum salicaria) Image by Ericka Mitchell/CC BY-NC 4.0
Reed canary grass (Phalaris arundinacea) Image by Anacostia Watershed Society/CC BY-NC 4.0
Southeast Asia likely from illegally emptied aquariums and bait buckets or wet recreational gear
2-inch-long brown-to-black triangular shell with distinctive elevated ridges; deep-purple to white inner shell
They live up to nine years and breed, grow and spread quickly, stealing habitat and food from native clams. They prefer shallow, quiet waters with sandy bottoms and are in many DuPage lakes and rivers.
Asia likely from illegally emptied aquariums and bait buckets or wet recreational gear
2-inch-long light to dark olive-green shells; deep purple to white inner shell
They eat microscopic plants and animals and can transmit parasites and diseases harmful to humans. They're common in DuPage lakes, wetlands and backwater areas of rivers, where they steal food and habitat from native snails and clog water-intake pipes.
Brought from Europe in 1800s and widely distributed by the federal government as a food fish
Relatively broad, heavy-bodied; variable color; toothy spine; 1 – 2 feet long and 1 – 8 pounds (but can reach 40 pounds); two rounded deep lobes on tail; sometimes has two barbels at corners of mouth
Carp grub for food along the bottom, churning up nutrients and sediment as they go, particles that prevent sunlight from reaching plants and animals that need it to survive. They breed quickly and are widespread in lakes, ponds, wetlands and rivers.
Illegally dumped from aquariums and backyard ponds
Goldfish are closely related to the common carp; koi are common carp bred for color. Hybridization between species within the carp family is not uncommon.
These are some of the most widespread aquatic invasives in the U.S. Goldfish are particularly well-adapted because they eat a variety of foods, tolerate poor environments and reproduce prolifically.
From Gulf Coast and Mississippi River basin to southern Illinois likely from illegally emptied aquariums and bait buckets (and possibly restaurants)
Dark red with raised bright red spots and a black wedge-shaped stripe on the top of its abdomen; grows to 8 inches long
Red swamp crayfish make up the majority of farmed crayfish consumed worldwide. In wild areas they've invaded, they steal habitat and food from native crayfish and lower amphibian populations by eating their eggs and young and competing with adults for habitat.
Round Goby Neogobius melanostomus
Black Sea from ballast water in commercial freighters
Up to 10 inches long; distinct black spot on first dorsal fin
These bottom-dwellers are voracious eaters that easily out-compete native sculpin and logperch and can decimate populations of native game fish by eating their eggs.
Middle Ohio River Basin likely from illegally emptied aquariums and bait buckets
What It Looks Like
Up to 4 inches long; distinctive rusty spots on sides
These aggressive crayfish steal habitat and food from native species and have rapidly expanded their range by interfering with the reproduction of native species.
Eastern Asia likely from illegally emptied aquariums
What It Looks Like
Eel-like body up to 9 inches long; small narrow mouth surrounded by six barbels
Weather loaches live along the silty bottoms of low-gradient, shallow waters, often in submerged plant beds, where they steal habitat and food from native fish.
Russia from ballast water in commercial ships
What It Looks Like
1- to 1.5-inch-long striped shells
Zebra mussels are now in over 25 states; control costs in the Great Lakes alone is $100 –$400 million annually.
Just one adult can filter the microscopic plants and animals from 1 quart of water in one day; one colony can clear an entire lake. This leaves little food for small native animals, such as zooplankton and small fish. As a result, populations of larger fish, which feed on the smaller fish, also decline. In some areas zebra mussels clear the water to such an extent that walleye and other light-sensitive fish must move to deeper waters.
The increased sunlight also means aquatic plants can grow denser at greater depths, which creates habitat for small fish but prevents larger predators from finding food. The dense beds also cause problems for boaters and anglers.
As zebra mussels die, their decaying bodies create foul odors, and their sharp shells pile up on shorelines.
Europe likely accidentally in ballast water from ships
2- to 2.5-inch-wide grey-green leaves 8 – 15 inches long; distinctive purple-brown plumes at tips of stalks appear late July; grows 6 – 15 feet tall with 80 percent of mass underground
Also called phragmites, this perennial overtakes wetlands and shorelines, creating tall, dense stands. It primarily spreads by rhizomes (horizontally growing stems at or below the surface) and root fragments. Each rhizome can spread over 60 feet and grow over 6 feet tall per year. Roots and rhizomes can accumulate in the soil over 6 feet deep.
Eurasia, Africa and Australia from hobbyists in the mid-1880s for use in aquariums
3-inch-long oblong reddish-green leaves with wavy, fine-toothed edges; flat reddish-brown stems 1 – 3 feet long
The plant spreads via seeds and burrlike winter buds, which move along waterways. New plants form under the ice, making it one of the first invasives to emerge in spring. Dense mats prevent sunlight from reaching native plants and animals below and create problems for anglers and boaters. As the plants decay, they release nutrients into the water that contribute to algal blooms and create foul-smelling messes along the shore.
Eurasia, Africa and Australia from hobbyists in the mid-1880s for use in aquariums
Slender, whorled stems and threadlike leaves, each with 12 to 21 pairs of leaflets; tiny four-petaled or petal-less flowers that grow above the water; four-jointed nutlike fruits
The plant is spread by fragments that hitchhike on recreational gear and wildlife. Just one 2-inch fragment can start a new colony. Dense mats prevent sunlight from reaching native plants and animals below and create problems for anglers and boaters.
Eurasia, Africa and Australia from hobbyists in the mid-1880s for use in aquariums
Narrow 3-foot-long above-water leaves with triangular cross-sections; three-petaled flowers with three white or pink sepals in distinctive flat-topped sprays atop tall stalks
Flowering rush spreads by rhizomes (horizontally growing stems at or below the surface) and root pieces. It's often mistaken for a native rush because it's difficult to identify when it's not flowering.
Europe and Asia in the 1800s likely from gardeners or ballast water from ships
4 – 7 feet tall with up to 30 purple-flowered spikes
Each plant can produce 2.5 million seeds in one year. This hardy, aggressive perennial takes over wetlands and moist soils but offers little food value to wildlife. Unsuspecting people often pick and spread its flowers.
Reed Canary Grass Phalaris arundinacea
Gulf Coast and Mississippi River basin to southern Illinois likely from illegally emptied aquariums and bait buckets (and possibly restaurants)
Smooth, erect flowering green stems 3 – 7 feet tall; leaves 0.5 inch wide and 4 – 8 inches long
One of the most aggressive invasives in the Midwest, this plant spreads via rhizomes (horizontally growing stems at or below the surface). It forms dense stands in wet meadows and marshes and around rivers as well as in prairies and woodlands.
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