An option outlined recently by the US Army Corps of Engineering to prevent the spread of invasive species is the possibility of permanently separating Lake Michigan from the Chicago River.
As the name suggests, this species of carp is native to the Far East. They were introduced to the southern states of the US over 30 years ago to help to control the build-up of algae in and around sewage treatment plants, but some escaped into the Mississippi River where they proliferated and made their way northwards towards the Great Lakes.
The Asian carp is over a metre in length and it is feared that the aggressive fish could jeopardise the Great Lakes' lucrative fishing and tourism industry, worth about $6.5bn (£4bn) a year to the local economy. "The fish have attacked boaters, making rivers unsafe for water recreation," warned the National Wildlife Federation, America's largest conservation organisation. As a precaution the Illinois Natural History Survey Station has installed netting around the steering wheels and dashboards of its fishing boats.
Michael Beecham, a local environmental campaigner, spoke about his frightening experiences at a public consultation on the issue. "I've gone down the river and had these fish jump up and hit me in the face. It is a big problem for our natural species," he said.
The US Army Corps of Engineers organised the meeting, which has been asked by Congress and the White House to come up with a solution to the carp problem. Its study has put forward several options, one of which involves blocking parts of Chicago's canal system. This might take 25 years to complete.