About Aquatic Invasives

About Aquatic Invasives

An invasive species is defined as any species introduced by humans to an ecosystem where it is not native, and which ends up causing economic or environmental harm, or harm to human health.

Since the arrival of the first Europeans on the shores of North America, we have added 50,000 alien plants and animals to our native ecosystems. Yet not all of these species are considered to be invasive. Most of these foreign species are non-threatening, or even beneficial to us. Some of them have become so important to our economy that they are considered icons of the North American landscape. Familiar staples like wheat, barley, and even the “all-American” apple, did not exist on this continent before the arrival of European settlers. Others, like a strain of human cholera bacteria from South America that was transported to Mobile Bay, Alabama, are a threat to human health.

The most damage to our natural landscape is caused by a small fraction of these introduced species that become invasive. A 2004 Cornell University study pointed out that the economic damages due to invasive species, and the costs of controlling them, add up to over $120 billion a year. Florida spends more than $14 million each year to control hydrilla, an aquatic invasive plant. In the Great Lakes, municipalities spend about $360,000 per year to control zebra mussels.

The most devastating species introduced to the U.S. have been from other countries. Zebra mussels, hydrilla, and sea lampreys are examples. However, even species native to the U.S. can become a nuisance when put into the wrong environment. For example, crappies are excellent sport fish. In many lakes, they fit in well with the balance of the lake. However, in a wrong setting, the crappie could populate faster and out-compete native species for food and space.

In new surroundings, the out of place organisms are freed from predators, parasites, pathogens and competitors that have kept them in check. Once established, invasive species are difficult to manage and nearly impossible to eliminate, creating a costly burden for current and future generations.

Invasive species can turn the food chain on its head. Species such as the round goby can eat the eggs of native species and eliminate their future generations. Mollusks like the zebra mussel can filter important nutrients out of the water that support other native species. Zebra mussels compete with native mussels for food and attach themselves to native mussels, killing them by preventing their shells from opening and closing. Invasive plants such as purple loosestrife and hydrilla displace native plants that wildlife depend upon. This causes the decline of many bird species. Invasive plants can also cover the surface of a lake or pond and make it difficult for swimmers and boaters to use the waterway.

How Are Invasives Introduced and Spread?

The largest source of unintentional introductions of invasive species to the United States is from transcontinental shipping vessels. Many are carried in ballast water taken on in foreign ports for stability. When ships reach their destinations, the exotic species are released with ballast water discharge. Once introduced into the Great Lakes or coastal waters, many aquatic invasives spread to inland waterways by recreational boating, bait buckets, and barges.

What Can I Do to Help?

Cleaning your boat and other recreational equipment between waterway visits will prevent aquatic invasive species from hitching a ride and can help protect our lakes and streams from harmful invasions. Please follow our instructions for cleaning your equipment each time you leave the water.

For more information on what you can do to protect our waterways, including advocacy, education, and more, click here.

Links to More Information

National Invasives Species Information Center.  This site includes species profiles, images, educational materials, identification guides, and discussion groups on invasive species.  

Protect Your Waters. Get more details on how to clean your recreational equipment properly to stop the spread of aquatic hitchhikers. Also learn more about some of the worst aquatic invaders and what you can do to help.

U.S. Geological Survey Nonindigenous Aquatic Species. Resource pages include updated distribution maps identifying locations and spread of aquatic invasive species by region, as well as facts, images, biology, and status reports by species.

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