Image copyright Brenna Hernandez Image caption The fear is that Asian carp could completely overrun high-value fisheries such as salmon

The US city of Chicago is considering drastic measures to prevent giant fish infesting North America's Great Lakes.

Authorities are thinking of blocking the city's canal system to stop Asian carp entering Lake Michigan.

Such a move could cost up to $18bn (£11bn) and cause huge economic disruption to the city.

Cheaper options are also being examined, including making burgers out of the fish and eating them to extinction.

This species of carp, as the name suggests, is native to the Far East.

They were originally introduced to southern US states more than three decades ago to control algal build-up in sewage treatment plants. But they escaped into the Mississippi River and proliferated, making their way north towards the Great Lakes.

More than a metre in length, they have displaced indigenous fish species along the way.

Technological solutions

Dozens of them will often leap out of the water as boats approach.

A local environmental campaigner, Michael Beecham, told a public consultation on the issue about his experience of this frightening spectacle.

"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 meeting was organised by the US Army Corps of Engineers, which has been asked by Congress and the White House to come up with a technological 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.

Col Frederick Drummond said that the issue had emotional as well as financial factors.

"I tell folks it's a very complex study. There are 9.1 million people in Chicago and over a period of 100 years that canal has been there and the economic impact is considerable."

Dinner proposal

Listening in at the meeting was John Goss, representing the White House, who was worried about the effect that having permanent barriers in the canal system would have on industry.

"It would certainly increase the cost of transportation," he told BBC News.

"It is currently very cheap and efficient to bring materials and finished goods down that Chicago ship canal. The steel industry, for example, depends on scrap metal by barge."

Image copyright AP Image caption The carp have worked their way up the Mississippi

Another cheaper option, not suggested by the Corps of Engineers report, is to eat the fish out of existence.

Dirk Fucik is selling carp burger at his specialist fish shop not far from downtown Chicago.

He tells me he thinks the carp are a great resource.

"To catch it and throw it away is a waste," he says. "Eating them helps solve the problem and also provides jobs."

Mr Fucik's burgers, mixed with lemon zest and pepper, did not taste bad at all. But the idea has not yet caught on. So far, he is the only person in the whole of Chicago selling carp burgers.

Media playback is unsupported on your device Media caption Pallab Ghosh went to see what Mr Fucik's carp burgers tasted like

International perspective

Although the Asian carp may appear to be an issue only for the US states and Canadian provinces, Roger Germann, of the Shedd Aquarium in Chicago, said the rest of the globe should also be concerned.

"Twenty per cent of the world's freshwater is in the Great Lakes, and from an economic standpoint it will affect shipping that folks in the UK and other parts of the world might rely on to get their goods and services here because they are going to cost more to transport."

Illinois and neighbouring states will have to find a solution soon. Many believe the fish are unstoppable and that it is only a matter of time before they make the Great Lakes their new home.

The carp problem was also being discussed in town at the annual meeting of the American Association for the Advancement of Science (AAAS).

Image copyright Reuters Image caption Lake Michigan is connected to the Mississippi River via an economically important canal system

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