I’ve commented before on the misguided and occasionally disastrous measures used to control non-native species that have gotten out of control. These include the release of the South American nutria—big, water-loving rodents—in the 1940s in the southeastern US to munch on water hyacinth that was clogging canals and the more recent use of the salt cedar beetle to kill tamarisk (salt cedar) trees that had been brought to the US in the 1800s for erosion control.
Now an effort is underway to stop the Asian carp from invading Lake Michigan. The carp were brought to the US in large numbers in the 1970s and used to clean up algae in fish farms in Arkansas. They thrived and moved north where, 30 years later, they’re approaching dangerously close to the Great Lakes, the source of most of the freshwater in the US and about 20% of the freshwater in the world. The concern is not only for the ecosystem of Great Lakes but also for fisheries located there.
In November, the carp were found in a canal near Chicago about eight miles from Lake Michigan. The canal is part of a waterway that links the Mississippi River with the Great Lakes, and officials had been concerned for years about the possibility of the carp using the passage, even installing underwater electric barriers to stop them. In December, more than 2,000 of rotenone—a poison commonly used in pesticides and insecticides, also effective for killing fish—was added to a six-mile stretch of the canal. The fish kill allowed the US Army Corps of Engineers to gain access to conduct maintenance on one of the electric barriers.
Critics have noted that, of the 100 tons of dead fish pulled from the water, only one single Asian carp was found. Proponents, however, point out that the carp, which can reach lengths of 4 feet and weigh up to 100 pounds, tend to sink to the bottom when they die. (The fish that were recovered from the water were disposed of in a landfill.)
The controversy over the carp and the measures to control them involves the larger issue of control of the waters of the Great Lakes and the passage of freight traffic in the region.
This New York Times article details many of the legal issues.
What’s your opinion—is there a better way to deal with the Asian carp?