FEATURE ARTICLE

With a growing public awareness of the potential impact of some high profile species in our region that are termed invasive, exotic,, or non-native, comes the question, "How are these terms different from one another?" Here is a breakdown that may help define these terms and eliminate some of the confusion for our curious population:

Exotic Species —
Any species introduced from a foreign country.

Non-Native Species —
Any species that occupies an ecosystem beyond its historic range. Think of rainbow trout that live in Maryland and were introduced here for commercial purposes.

Introduced Species —
Species that are intentionally introduced into an ecosystem for possible economic gain or biological control. The current debate over whether to introduce the Asian oyster (Crassostrea ariakensis) into Chesapeake Bay is a clear representative of this category.

Invasive Species —
An "invasive species" is defined as a species that is 1) non-native (or alien) to the ecosystem under consideration and 2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health. (Executive Order 13112) http://www.invasivespecies.gov/

Aquatic Nuisance Species —
Introduced, exotic, or transplanted species, including viruses, bacteria, protozoans, and parasites, that threaten the diversity or abundance of native species or the ecological stability of infested waters, or commercial, agricultural, aquacultural or recreational activities dependent on those waters.

Still unclear? There are overlaps between these categories that cause the confusion. For example, a species can be exotic or non-native but not necessarily invasive since it may not have an economic impact or cause environmental harm.

Snakehead photograph courtesy of MD Department of Natural Resources

So, what are the specific issues in the Mid-Atlantic region related to invasive species? You have probably heard of various species on the news that have come to Chesapeake Bay waters through a variety of means (boats, ballast water, shipping containers, etc.) and there are many that none of us have heard about since it is difficult for exotic species to invade new ecosystems and become established. Only about 10% actually gain the status as invasive species. A species is only classified as invasive when it has clearly become established in the ecosystem and alters some aspect of that ecosystem, the economy of the region, human health, recreation, or affects other social issues.

Current Exotic Issue...The Northern Snakehead

The northern snakehead (Channa argus) is a current exotic that could become invasive in our region. In 2002, you may recall that a Crofton Pond became home to about 7 adult snakeheads and over 1,000 juveniles before the pond was treated with chemicals to kill all the fish and clear the pond. Snakeheads were later discovered in the Potomac River in April 2004 and in Philadelphia in early July.

So how did the snakeheads get into Maryland waters? They are placed there either by pet owners that realize their snakehead has outgrown the tank and their budget or by someone that wants to fish for the snakehead as a food source and hopes it is able to establish itself. The result. Maryland, Delaware and Pennsylvania already have bans on selling or possessing the northern snakehead but tropical varieties may be kept as pets (there are 28 other species of snakehead).

Snakehead for sale?

What's ironic is that even as scientists plot to exterminate the fearsome beast in Maryland, large-scale artificial breeding projects are underway in China and neighboring countries to meet the growing demand for snakehead meat throughout Asia, where it's valued as both a soup ingredient and a folk remedy. While "live" snakehead imports are currently regulated, it is likely that the release of this potentially invasive organism will continue.

Sites of Interest

Invasive species information
http://www.invasivespecies.gov/

Snakehead profile from Invasive Species web
http://www.invasivespecies.gov/profiles/snakehead.shtml

Maryland Department of Natural Resources snakehead resource
http://www.dnr.maryland.gov/dnrnews/infocus/snakehead.asp

Cambridge Scientific Abstracts- story of snakehead in Crofton
http://www.csa.com/hottopics/snakehead/overview.html

Habitattitude
http://www.habitattitude.net/

Snakehead photograph courtesy of USGS

http://www.mdsg.umd.edu/Extension/msgsnn/msgsnn07_1/index.html