Aquatic Invasive Species

Invasive Species of Long Island Sound

For full list of Invasive Species of Long Island Sound DOWNLOAD PDF

photo of reed grass

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

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.