Common Aquatic Invasive Species of NY
Eurasian Watermilfoil
Native to Europe, Asia and Africa, Eurasian watermilfoil is a very aggressive exotic and as since found its way into virtually every U.S. state and three Canadian provinces. Its items are usually 3 to 10 feet in length, often forming dense mats on the surface. Its bright green feathery leaves are finely divided and occur in whorls (circles) around the stems. Each leaf has 12-21 leaflet pairs (native northern milfoil has 5-10 leaflet pairs). Eurasian watermilfoil can spread by both seed and, most commonly, by plant fragments.
Water Chestnut
Native to Europe, Asia and Africa, water chestnut is an annual aquatic plant with a long flexible stem that can reach 12 to 15 feet in length. On the water's surface, the plant contains a circular cluster of sawtoothed edged, triangular floating leaves that are connected to an inflated petiole (bladder), which provides added buoyancy. Feather-like leaves can be found along the long submerged stem. The fruit is a nut with four 1/2-inch, barbed spines that can cause a painful wound if stepped on. Seeds can remain viable for up to 12 years. Water chestnut can be spread from the rosette and fruits detaching from the stem and floating to another area, or by fruits clinging to objects, birds and other animals.
Fanwort
Native to South America and the southern United States, fanwort has spread throughout the U.S. It is a perennial aquatic plant with a long stem that can appear tubular. It has fan-like leaves with a short stem and finely dissected divisions that are arranged opposite of each other on the stem. Plants have white to light pink flowers that float on the surface. Fanwort primarily spreads through fragments that break off from the plant as it becomes brittle later in the growing season.
Curly-leaf Pondweed
Curly-leaf pondweed is native to Europe, Asia, Africa, and Australia. The leaves are reddish brown/green, oblong, about 3 inches long, somewhat stiff and crinkled, with finely-toothed edges. The stem is fl at, reddish-brown and grows 1 to 3 foot long. The plant usually dies off by mid-summer. Though it can reproduce by seed, it primarily spreads through burr-like winter buds (turions) which break off from the plant. New plants grow under the ice in winter, giving it a head start over other native aquatic plants.
Didymo
Didymo is a freshwater diatom (a form of algae), native to northern North America and Europe. It was first identified in New York State in 2007 in the Batten Kill and Delaware River tailwaters. Didymo is primarily found in coldwater, flowing streams. It is attached to the stream bottom by stalks. As the stalks lengthen, didmyo can form wavy mats. It can be distinguished from native algae (usually green in color) by its tan or brown color. Long strands of didymo can often be washed white at the ends. It has a wet wool texture that is not slimy and does not fall apart when rubbed between fingers. Didymo cells are microscopic, and this invasive algae can be spread by a single drop of water.
Round Goby
Round gobies are bottom-dwelling fish that were introduced to the Great Lakes from central Eurasia.Round gobies are usually 3 to 6 inches in length, but can reach 10 inches. Key identifying characteristics include a black spot on the rear of the upper dorsal fin, a raised frog-like eye, thick lips and a body mostly slate gray or black, mottled with black or brown spots.
Zebra Mussel
The zebra mussel is a small, nonnative mussel originally found in Russia. Zebra mussels grow to about 2 inches in size. They can usually be identified by striping on their shells, although this pattern varies greatly to the point that some shells have little if any noticeable striping. Young zebra mussels are microscopic in size and are spread easily by water currents.
Alewife
The alewife is native to the coastal waters of New York. Unfortunately, due to migrations from these waters and bait bucket introductions, this species has also become established in nuisance proportions in the Great Lakes and many inland waters in New York State, most recently in Lake Champlain. Alewives are silver in color with a blue-green metallic luster along the back, usually with a black spot behind the gill cover and a serrated belly. In freshwater, they usually grow to 3 to 6 inches in length; however, in saltwater they can attain lengths of a foot or more.
White Perch
White perch are an anadromous species that live most of their life in marine waters, but spawn in freshwater. Although a valued sportfish in some coastal waters, this species can become a nuisance when accidentally or purposefully introduced into landlocked waters. White perch are silvery-gray in color, with a light belly. Unlike the white bass and striped bass, they lack striping. They can attain lengths of 12 inches or more in freshwater and even larger in marine waters, but in overabundant populations rarely exceed 6 inches in length.
