Asian Carp Overview
United States Geological Survey
What are carp?
Carp are a family of fish native to Europe and Asia. Cyprinus carpio, the common carp, has been in the US for over 100 years. That's long enough that we don't really know what our waters would be like without them. The common carp is considered a nuisance fish, but it doesn't seem to be doing too much harm to the lakes and rivers it lives in. The newest carp invaders, however, seem to be causing a lot of trouble in the Mississippi and the surrounding waters. These newcomers (collectively named "Asian carp") are four separate invasive exotic species; the bighead carp, the black carp, the grass carp, and the silver carp.
These carp were introduced to the U.S. in the 1970's in hope that they would control weed and parasite growth in aquatic farms. A few of these carp managed to get into the Mississippi River, and eventually established breeding populations. They are slowly making their way northward up the Mississippi River and its tributaries, and have been found as far north as Minnesota.
Why are carp a problem?
Asian carp cause serious damage to the native fish populations in the lakes and rivers that they infest because they out-compete other fish (video, 1 min) for food and space. Carp are also thought to lower water quality, which can kill off sensitive organisms like native freshwater mussels. Asian carp have been known to dominate entire streams (video, 45 sec), effectively pushing out the native species.
Experts are worried that if these fish get into the Great Lakes, they may negatively affect the area's $7 billion/year fishing industry. By out-competing native fish species for food and habitat, carp may reduce the populations of native fish that are so important to fishermen. Even if Asian carp are kept out of the Great Lakes, continued spread throughout the Mississippi River watershed could result in them reaching 31 states and 40% of the continental United States, spelling disaster for our nation's freshwater ecosystems.
How do carp spread?
Asian carp (especially Silver carp) are capable of jumping over barriers, including low dams. Flooding can spread these fish as well, because flooding can connect water bodies that aren't normally connected. This makes it possible for fish to travel to new areas. Recent floods may have helped the fish spread further.
Asian carp are also spread by human actions. The release of live bait containing young carp has introduced these fish to numerous water bodies. Watercraft that use the Mississippi locks allow carp to move upstream when the locks are opened to allow boats through. Additionally, boats that aren't drained after use can carry young carp or eggs that may be released into the water the next time the boat is used.
Bighead and silver carp eat plankton, which native mussels and fish depend on. Grass carp consume plants, and can drastically change river and shoreline vegetation. Black carp have human-like molars and eat snails and mussels, including native species that are already endangered.
When the amount of plants, mussels, and plankton are lower in our lakes and rivers, the ecosystem becomes unbalanced and our native species that depend on these food sources suffer.
What is being done?
State and federal agencies are monitoring the Mississippi River and its tributaries for Asian carp, and studying various barrier technologies that would prevent the further spread of these species. The Mississippi National River and Recreation Area is working with other agencies on a task force to create an Action Plan for Minnesota.
The DNR is constructing a barrier on the Coon Rapids Dam to prevent Asian carp from moving up river. The plan is to increase the distance between the water above the dam, and the water below so carp can't jump over the barrier. The barrier should be finished in late 2012 or early 2013.
We're also studying how far these fish have spread. The USGS and the Upper Mississippi River states keep a record of "known established populations," which are areas that we know carp live and reproduce. The NPS is also working with other agencies in a task force to create an Action Plan and to see how close these fish are to the Twin Cities. If you have more questions about carp, check out the Frequently Asked Questions on Asiancarp.org.
What you can do: