Common reed, stout grass Phragmites australis

Description: Stalks reach heights of 6-12 feet; color of inflorescence is purple to light brown. Found at edges of marshy areas, both fresh and brackish water, along roadsides, or in open disturbed areas

Pathway: natural immigration

Current Distribution: Found in all of the New England states; native to some parts of the U.S.; has been in New England for at least 4000 years. Non-native strains were also introduced and are believed to be the ones with the invasive tendencies.

Impact: Forms huge monocultures that exclude native species

Bread-crumb sponge, Halichondria bowerbanki

Description: benthic; brown, yellow, or olive green in color; forms colonies with fingerlike projections; reaches 30 cm long, 5 cm thick; grows on rocks, pilings, and algae

Pathway: fouling organism introduced from Europe; first reported in Long Island Sound in 1871

Current Distribution:

Impact: Fouls hulls, dock pilings etc; displaces native species

Photo: James T. Carlton

Orange striped anemone, Diadumene lineata

Description: formerly known as Haliplanella lineata; benthic; blackish bodies with orange, red, white or yellow vertical stripes; generally small (up to 1.5" tall), 25-50 tentacles; found in tidal marshes and protected subtial areas, on intertidal rocks, seaweeds, and hard structures like pilings, docks, and floats

Pathway: Native to Japan; came to New England via ship hulls in 1890s; found in New Haven harbor

Current Distribution: Maine to Florida

Impact: localized displacement of native species

Common periwinkle, Littorina littorea

Description: gastropod mollusk found on intertidal rocks; brown, black, or grey in color; reaches up to 3 cm; herbivore; also known as European periwinkle

Pathway: introduced via ballast, rocks, or intentionally as food; introduced to eastern Canada in early 1800s, reached Cape Cod to Long Island Sound by 1870s

Current Distribution: Labrador to Virginia

Impact: one of most dominant intertidal omnivores, particularly on rocky shores; competes with native Littorina species; densities can reach 1,000 per square meter; grazes on algae

Photo credit: Giorgio Griffon

European flat oyster, Ostrea edulis

Description: shells are widers and rounder than eastern oyster (Crassostrea virginica); reaches up to 20 cm; also known as edible oyster or Belon

Pathway: introduced from Europe; intentionally released in Maine; found in Narragansett Bay and Long Island Sound (2002).

Current Distribution: Maine to Long Island Sound in estuarine habitats; intertidal and subtidal zones

Impact: compete with native oysters

Asian shore crab, Hemigrapsus sanguineus

Description: also known as Japanese shore crab; reaches 7-8 cm, brown striped legs with red spots on claws, with three spines on either side of carapace

Pathway: introduced from Asia to eastern seaboard most likely by ballast water; discovered in New Jersey in 1988; spread north and south; reported in Long Island Sound in 1993

Current Distribution: Maine to North Carolina; prefers rocky cobble

Impact: dominant rocky intertidal crab; consumes juvenile mussels and oysters, green crabs, snails, polychaetes, algae, hydroids, barnacles

Green crab, Carcinus maenas

Description: one of most common crabs on lower energy rocky shores, also known as European shore crab; dark green with yellow, brown, and orange blotches; reaches 8 cm; carapace has five spines along each side; omnivore - consumes barnacles, clams, hermit crabs, worms, algae, organic debris

Pathway: introduced by end of 18th century from Europe, probably via shipworm burrows in ship hulls; reported in LIS in 1817.

Current Distribution: Gulf of St. Lawrence to Delaware; lives on rocky shores, quiet backwaters, marshes, estuaries, brackish waters or coastal waters

Impact: voracious predator and scavenger; consumes juvenile shellfish (may have caused decline of softshell clam industry in Maine and even Long Island Sound); competes with native crabs.

Kelp bryozoan, Membranipora membranacea

Description: colonies found on kelp blades, also known as moss animal, lacy crust bryozoan; form large continuous mats

Pathway: introduced from Europe; reported in LIS in 1990.

Current Distribution: Maine to Long Island Sound

Impact: encrusts kelp and other algae; weighs it down, causing it to break off or die, contributing to loss of kelp habitat

Compound sea squirt, Didemnum sp.

Description: cream to white in color; colonial tunicate where microscopic individuals form large colonies (up to 45 cm long) with finger-like projections; juveniles present from July to November

Pathway: introduced from the Pacific

Current Distribution: Maine to Connecticut, including Georges Banks off New England coast

Impact: fouling organisms, attaches to rocks, docks, pilings; forms encrusting mats on seafloor, usurping benthic habitat

Asian stalked tunicate, Styela clava

Description: also known as club tunicate; brown or yellow in color with a rough and wrinkled surface; reaches up to 15 cm

Pathway: native to Japan; first introduced to Europe and then the U.S. most likely via ballast water

Current Distribution: Maine to New Jersey, Prince Edward Island; Narragansett Bay in 1976; LIS (1982)

Impact: Fouling organisms - attach to boat hulls, piers, docks, lines, traps, buoys, seaweeds, firm structures; has taken over what used to be blue mussel (Mytilus) habitat

Sea Grape, Molgula manhattensis

Description: benthic underwater organism also known as solitary tunicate; reaches up to 5 cm, grayish green color with outer covering sometimes covered with mud

Pathway: introduced from Europe via west coast of North America; reported in Long Island Sound in 1838; may be cryptogenic species (unclear whether is native or introduced species)

Current Distribution: Maine to Louisiana

Impact: fouling organism

Compound tunicate, Botrylloides violaceus

Description: colonial tunicate; bright orange to red or purple in color; reaches up to 10 cm; gelatinous colonies form dense clusters

Pathway: introduced from Asia; from the Pacific in the 1970s

Current Distribution: Maine to Virginia; reported in LIS (1980's)

Impact: fouling organism - attaches to boat hulls, piers, lines, traps, buoys, seaweeds

Golden Star Tunicate, Botryllus schlosseri

Description: also known as compound tunicate, star ascidian; vary in color from yellow to green, brown, or violet; colonies up to 10 cm across

Pathway: introduced from Europe; reported in Long Island Sound in 1871

Current Distribution: Newfoundland to Chesapeake Bay

Impact: fouling organisms - attach to boat hulls, piers, docks, lines, traps, buoys, seaweeds, any firm structure

Specimen credit: Charles Yarish

Red alga, Grateloupia turuturu

Description: formerly known as Grateloupia doryphora; thin flat blade that is pink to maroon in color; grows up to several meter in length; both divided and undivided forms; is most abundant in October, least abundant in May

Pathway: introduced from Japan; first observed in North America in 1996 in Narragansett Bay (arrived about 1994); most likely introduced as spores via ballast water discharge; reported in Long Island Sound in 2004

Current Distribution: Rhode Island Sound, Narragansett Bay, Long Island Sound; restricted to subtidal pools, does not survive very cold temperatures

Impact: major competitor of Irish moss (Chondrus crispus); in upper subtidal, could crowd out sugar kelp, (Laminaria saccharina); can block sunlight; reproduces easily

Dead man's fingers, Codium fragile ssp. fragile

Description: also known as oyster thief, green fleece, Sputnick weed; branching green algae with spongey fingers, can reach a meter tall

Pathway: introduced from Asia; appeared in New England waters coincidentally with launch of world's first satellites, Sputnik I and II, by former Soviet Union in 1957; probably came attached on hulls of ships via Europe

Current Distribution: New Brunswick to North Carolina

Impact: forms extensive beds in shallow bays and harbors; called "oyster thief" or "scallop thief" because holdfast grew around oyster or scallop, then as algae grew, became buoyant and drifted off with shellfish attached

Photo: Richard Seaman
www.richard-seaman.com

Lionfish, Pterois volitans

Description: also known as zebrafish or turkeyfish; one of several species of venomous coral reef fishes; striking reddish-brown striped pattern on body and fins

Pathway: native to Indian and Pacific Oceans; introductions likely the result of intentional or unintentional releases by aquarists; reported in LIS (1999)

Current Distribution: Florida to Long Island Sound; seasonal invader of eastern Long Island Sound; comes in with warm core rings of water that break off from Gulf Stream; first observed by divers in Florida in 1994

Impact: venomous; no natural predator

Mute swan, Cygnus olor

Description: large white swan with yellowish-orange bill; long neck

Pathway: Introduced from Europe as decorative waterfowl in late 1800s or early 1900s

Current Distribution: southern Ontario to North Carolina or Florida; reported in LIS by 1920s

Impact: using long necks, the swans graze on vegetation by ripping important submerged aquatic vegetation such as eelgrass out by the roots, damaging marsh and shallow water habitats; overpopulated, displacing native swans.