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Aquatic Invasive Species

What are invasive species?
Invasive species are introduced plants or animals that aggressively out-compete and in some cases displace native organisms. The official U.S. definition is an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health.

Where do invasive species come from?
Aquatic invasive species introduction can often be traced back to human-related activities, including: 

• ballast water intake and discharge from ocean-going ships;
• boat hulls;
• intentional and accidental aquarium and aquaculture releases;
• fishing bait; and
• habitat shifts from human-induced global warming.

Why are invasive species a problem?
Lacking predators, or becoming a new predator, invasive species are often capable of encroaching and smothering native species habitat due to the absence of predators and causing disruptions in the food chain. Invasive species threaten the Earth’s biodiversity, second only to habitat loss.

Click on the links below to learn more about aquatic invasive species and what you can do to protect our treasured water bodies from ecological invaders.

• The Great Lakes and St. Lawrence River
• Northeast estuaries
• Links to additional information on Aquatic Invasive Species

Great Lakes: Halting Invasive Species

Why are invasive species a problem for the Great Lakes?
Invasive species are the most pressing issues facing the Great Lakes region. They pose an unrelenting threat to the health of the Great Lakes ecosystem and economy. There are 185 known invasive species already in the Great Lakes, and a new one arrives on average every 28 weeks. Once a new species establishes itself, it is almost impossible to remove and incredibly difficult to contain.  Invasive species:

Fish kill caused by VHS, an invasive pathogen that has recently spread through the Great Lakes.

• Foul beaches, causing beach closures;
• Harm the $4.5 billion Great Lakes recreational fishery;
• Clog power plant and municipal water infrastructure;
• Disrupt the food chain;
• Deteriorate drinking water quality;
• Contribute to the “dead zone” in Lake Erie;
• Contribute to outbreaks of botulism, which kills fish, birds and other wildlife; and
• Cost citizens, business, and municipalities $5 billion annually for damage and control costs, with more than $1.5 billion spent on controlling the Zebra Mussel alone. 

Examples of Aquatic Invaders in the Great Lakes

• The Sea Lamprey is an invasive fish that brought the issue of aquatic invasive species to the forefront. First discovered in Lake Ontario in 1835, the Sea Lamprey has brought many native species to near extinction, with the cost of control programs in the Great Lakes reaching approximately $15 million annually. 
  
  
• The Zebra Mussel is a invasive mollusk that arrived in the Great Lakes through ballast water in the late 1980s, and has wreaked havoc on the ecosystem and economy ever since. Zebra Mussels clog water intakes, filtration equipment, and power generating plants, as well as contributing to the “dead zone” in Lake Erie. Control costs for Zebra Mussels are estimated at $1.5 billion annually.  
  
  
• The Round Goby arrived in the Great Lakes in 1990, most likely through ballast water. This invasive fish is aggressive, feeding voraciously upon bottom dwelling fishes, snails, mussels and aquatic insects.  The Round Goby has adversely impacted native fish populations, harming sport and commercial fisheries.
  
  
• Viral Hemorrhagic Septicemia (VHS) is an invasive virus, thought to be introduced through ballast, that has recently spread through the Great Lakes. While not harmful to humans, VHS is a serious pathogen that can cause hemorrhaging of fish tissue, including internal organs, and can cause the death of infected fish.
  
  
• The Eurasian ruffe is a small and aggressive invasive fish that was introduced into the Lake Superior in the mid-1980s, and has spread and reproduced very rapidly. The ruffe out competes native fish species, preys on native fish eggs, and has ultimately had a negative impact on Great Lakes fisheries and tourism.
  
  
• The Common reed is an invasive plant that threatens by displacing native plants and forming monocultures in otherwise biologically diverse natural wetlands. It spreads by seed and strong vegetative growth and is very difficult to control once established.
  
  
• Purple loosestrife is an invasive plant introduced in the early 1800s as an ornamental. Purple Loosestrife is able to rapidly establish and replace native vegetation with a dense, homogeneous stand that reduces local biodiversity, endangers rare species, and provides little value to wildlife.

Estuaries and their Invaders

What are estuaries?
Estuaries are highly productive, semi-enclosed coastal aquatic habitats where an ocean’s saltwater is diluted with freshwater from the surrounding watershed. Estuaries are extraordinary places enjoyed by boaters, swimmers, hikers and nature watchers. They are also essential to the U.S. economy for commercial fishing and tourism. Every estuary is unique; each individual ecosystem has different components that complete the estuarine habitat. One estuary may be enclosed by marshes and barrier islands, while another estuary's borders are the coastline and reefs. Examples of estuaries include: Long Island Sound, Long Island South Shore Estuary Reserve, and Peconic Bay.

Examples of Estuarine Invasive Species in New York and Connecticut Waters: 

• Dead Man’s Fingers (Codium fragile) is an algae from the Asian Pacific, first reported on the east coast of Long Island, NY in 1957. Throughout the 1960’s to the present it has continued to spread up and down the US coastline. Codium is primarily transported on the hulls of ships and once established crowds and shades other plants and algae, but the most serious problem is that it is a killer of shellfish, giving it the nickname of “the oyster thief”.
  
  
• Common Reed (Phragmites australis) is a very aggressive, robust member of the grass family introduced to the US in the late 1800s from Europe. It is capable of occupying and degrading vast areas of important wetland habitat and may have arrived via ballast water.
  
  
• Purple loosestrife (Lythrum salicaria) was introduced to the Northeast in the early 1800s for medicinal and ornamental uses. Since then, it has spread rapidly and is now found in every U.S. state except Florida. This plant out-competes native marsh plant communities, replacing them with dense, homogenous stands. Also, purple loosestrife exudes chemicals that are toxic to American toad tadpoles.
  
  
• Fanwort (Cabomba caroliniana), native to South America, was introduced mainly from the aquarium plant trade. This plant is listed as banned in Connecticut because it is an extremely competitive and persistent plant capable of forming dense mats that crowd out native plants. Once established, the plant clogs waterways, disrupts natural flow, and interferes with recreational activities such as fishing and boating.
  
  
• Zebra Mussels (Dreissena polymorpha) are native to fresh and brackish waters in Europe and Asia and when introduced from ballast water spread rapidly and moved into the Hudson River in 1991, and from their into the Hudson River Estuary. Zebra mussels cause major ecological and economic problems by heavily colonizing hard substrates, displacing native mussels and clogging water intake structures which reduce pumping capabilities for power and water treatment plants.
  
  
• Brown Tide (Aureococcus anophagefferens) first found in 1985, decimated the nationally significant harvest of scallops in the Peconic Estuary of Long Island, NY and greatly impacted eelgrass beds. Brown Tide, while not harmful to human health, also adversely affects other species such as finfish due to reduced visibility.
  
  
• Chinese mitten crab (Eriocheir sinensis) is an omnivorous crab native to the coastal rivers and estuaries of the Yellow Sea. It is now spread throughout Europe and parts of the US. They have profound effects on biological communities through predation and competition and through their burrowing activities which could accelerate erosion of banks. Mitten crabs have affected commercial and recreational fishing by killing the shrimp used for bait.
  
  
• Green crab (Carcinus maenas) arrived in the Northeast via sailing ships in the 19th and 20th centuries and since then have reproduced successfully throughout the region imacting the ecology of the shallow, inter-tidal zone. Green crabs prey on bivalves and other crustaceans, such as soft-shell clams and scallops.
  
  
• Lionfish (Pterois volitans) are tropical venomous fish that were introduced in 1992 by the aquarium trade from the Pacific Ocean. They pose a threat to fishermen, divers, and wildlife inspectors and when they envenomate someone it causes extreme pain, swelling, redness, bleeding, and nausea. Currently, the negative ecological impacts from Lionfish are minimal, however, they do prey on native species and surprisingly have been able to survive in temperate waters. Water temperatures in the Northeast have increased from human-induced global warming creating adequate conditions for the Lionfish.
  
  
• Sea Squirts, Didemnum sp., shown here, “cement” the bottoms of estuaries, such as Long Island Sound. They form dense mats by attaching to firm substrates such as gravel, sea scallops, mussels, docks and other structures, and even seaweed. Tunicates can overgrow sea scallops and mussels, and they may affect other species of clams and worms that live in the seabed below the tunicate colony.

Links to Other Resources: Learn more about the invasive species in your area

Sea Grant: www.aquaticinvaders.org/

CT Sea Grant: www.seagrant.uconn.edu/ans.htm#about

New York State Department of Environmental Conservation (DEC): www.dec.ny.gov/animals/265.html

Connecticut State Department of Environmental Protection (DEP):
www.ct.gov/dep/cwp/view.asp?a=2696&q=322690&depNav_GID=1620

United States Environmental Protection Agency (EPA): www.epa.gov/owow/invasive_species/

NOAA Research: www.research.noaa.gov/oceans/t_invasivespecies.html

United States Department of Agriculture: National Invasive Species Information Center: www.invasivespeciesinfo.gov/

The Global Invasive Species Database: www.issg.org/database/welcome/

Updated by bsmith 1/8/09