In 1972, a fish farmer in Arkansas bought some Chinese fish, called bighead carp, to help control algae in his ponds.   He and others used the fish at contained fish ponds in the south for over two decades, until a 1994 flood washed several thousand of the fish out of the ponds and into the Missouri River.  Since then, the fish – which can grow to be more than a yard in length and weigh up to 100 pounds – have reproduced and migrated throughout U.S. waterways, and now bigheads and other species of Asian carp are the most abundant fish in portions of the Missouri and Mississippi Rivers.
The problem is that, because the quick-growing fish are large, prolific, and eat huge amounts of food (up to 40 percent of their own body weight each day), the carp out-compete native species of fish for food, living space, and spawning areas, and they wreak havoc on the fragile ecosystems of the rivers and waterways.
We have witnessed the ecological destruction caused by the fish, and the accompanying financial burden, for many years.  And now, bighead carp are continuing their northward migration up the Mississippi River and are close to invading the Great Lakes, which are connected to the river through a man-made sanitary and ship canal in Chicago.
There are a number of things we can do – and have done – to help keep the Great Lakes free of this invasive species.
The Army Corps of Engineers built an electric dispersal barrier to prevent the carp and other non-native fish from moving between the Mississippi River and the Great Lakes.  The electric barrier is made of long steel cables that are attached to the bottom of the canal.  A low-voltage current is sent through the cables, which creates an electric wall in the water.  This electric barrier is not harmful to fish, but they turn back when they swim into the electric current rather than continuing through it.   A temporary barrier first became operational in 2002, and the Army Corps is currently working toward completion of a permanent barrier.
The barrier will hopefully keep Asian carp from entering the lakes from the Mississippi River, but we also need to guard against the possibility of the fish being introduced into the lakes in other ways.
As we saw with the Arkansas fish farmer, a single person buying some of these live fish can have devastating – and costly – ecological consequences.  A 1900 law called the Lacey Act prohibits the importation or interstate transportation of any species that it designates as “injurious” – which are species that threaten the interests of people, agriculture, forestry or wildlife of our country.
I recently introduced a bill in the Senate, the Asian Carp Prevention and Control Act, that would classify the bighead carp as injurious under the Lacey Act, thereby making it illegal to import or transport the fish live and, hopefully, help to minimize the risk of intentional introduction. Three other species of Asian carp (silver, largescale silver, and black) have previously been classified as injurious under the Lacey Act.
I hope that my bill will be approved by Congress and signed into law, and together with the completion of the permanent electric barriers, these safeguards should help to ensure that the bighead carp are kept out of our precious Great Lakes.

Carl Levin is the senior U.S. senator from Michigan.