'Monster' carp threat to Great Lakes
18 February 2014 Last updated at 10:11 GMT
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.
Pallab Ghosh reports from Chicago.