Invasive Species: Asian Carp

An invasive species is one that is introduced, either accidentally or on purpose, into a new environment which it then proceeds to overwhelm, generally with disastrous consequences. Yet another invasive species is threatening the Great Lakes. Like the Zebra Mussel before them, the Asian Carp is threatening to upset both the ecology and the economy of the Great Lakes region. There are three species of Asian Carp in U.S. waterways that are considered invasive: the Bighead Carp, the Silver Carp and the Black Carp.

Native to China, the Asian Carp was accidentally introduced into U.S. waterways, probably due to flooding along the Mississippi River in Arkansas. In just a few years, they have spread from Arkansas to as far away as California, Minnesota and Florida. They have now been found in waterways near the Chicago area and the next big concern is an invasion into the Great Lakes. If they were to enter into the Great Lakes, this could upset the ecology of the entire Great Lakes region, along with its $4.5 billion fishing industry.

Origins of the Asian Carp Problem in the U.S.

As mentioned, Asian Carp are native to China. Asian Carp are prized in China as a food source, mainly due to their fast growth. As filter feeders, Asian Carp survive on both zooplankton (microscopic animals) and phytoplankton (small plants). Because they have the ability to filter algae out of the water, Asian Carp were first brought to the U.S. during the 1970's by the Arkansas aquaculture industry in an attempt to help keep catfish ponds clean.

Introduction of Asian Carp into U.S. Waterways

Asian Carp escaped from the aquaculture ponds when flooding along the Mississippi allowed them to escape into U.S. waterways. Asian Carp have rapidly become a huge problem here. They have spread quickly throughout the Mississippi, Missouri and Ohio Rivers and their tributaries since these waterways are all now interconnected. They can now be found as far away as Florida, Minnesota and California. Because they do grow so quickly, are efficient feeders and don’t have any natural controls in place, their numbers have quickly skyrocketed. In just ten short years, they became the dominant species in the Illinois River. As they have steadily moved into Chicago area waterways, the next cause for concern is a Great Lakes invasion, since the Illinois River is also connected to the Great Lakes by a manmade connection known as the Chicago Sanitary and Ship Canal.

The Impact of Asian Carp on Native Species

The Asian Carp is a very invasive species that quickly overwhelms native species. Since they have the same food source as the young of many native species, those much smaller, younger fish have to try to compete with full grown carp, with the potential to reach 100 pounds each. And the native fish not only fight a losing battle for food, they can often end up as food for the carp themselves. Besides the competition for food, the Asian Carp also has the habit of thrashing around in shallow water, which destroys essential habitat for native fish and their young.

Additionally, Asian Carp pose a threat to people. The silver carp is skittish and easily startled by the sound of a boat motor. The sound can cause the fish to leap as high as ten feet out of the water, earning them the nickname "the flying fish." Some of these fish weigh more than twenty pounds, and when they leap they can land in boats, do significant property damage and cause injury to people.

Attempts at Controlling the Spread of Asian Carp into the Great Lakes

In an attempt to prevent Asian Carp from entering into the Great Lakes, officials have tried a number of approaches, including an electrical barrier designed to dissuade the fish with a non-lethal jolt. Although live Asian Carp have not yet been found passing the barrier, their DNA has been detected between the barrier and Lake Michigan. This raises the possibility that some Asian Carp, which have a phenomenal jumping ability, may have already breached the barrier. Also, in December of 2009, officials had to release rotenone into a six mile stretch of the Chicago Sanitary and Ship Canal while the electrical barrier was down for maintenance to try to prevent the carp from swimming past the barrier. While the poison killed many native species, its effectiveness on the carp was questionable.

There are campaigns to close the locks that currently allow shipping connections between the contaminated Illinois River and Lake Michigan. Corps of Engineers and EPA officials are looking at the proposal, but have not yet committed to it. At this point, it appears to be a battle between environmental and economic issues. Or possibly between competing economic sectors – the shipping versus the fishing industries.

At this time, while the Asian Carp has rapidly spread throughout the major river systems in the Central U.S., they have not yet been identified in the Great Lakes. How long that continues remains to be seen.