In North America
Silver carp were imported to North America in the 1970s to control algae growth in aquaculture and municipal wastewater treatment facilities. They escaped from captivity soon after their importation. They are considered a highly invasive species. Silver carp, with the closely related bighead carp, often reach extremely high population densities, and are thought to have undesirable effects on the environment and native species.
By 2003, silver carp had spread into the Mississippi, Illinois, Ohio, and Missouri Rivers and many of their tributaries in the United States. By August 2009, they had become abundant in the Mississippi River watershed from Louisiana to South Dakota and Illinois, and had grown close to invading the Great Lakes via the Chicago Sanitary and Ship Canal. Navigation dams on the Mississippi River seem to have slowed their advance up the Mississippi River, and until late November 2008, silver carp had not been captured north of central Iowa on the Mississippi. Dams that do not have navigation locks are complete barriers to upstream natural movement of silver carp, and it is important for fishermen not to assist this movement by the unintentional use of silver carp as bait.
The silver carp is also called the flying carp for its tendency to leap from the water when startled. They can grow to over 40 lb (18 kg), and can leap 10 ft (3 m) in the air. Many boaters traveling in uncovered high-speed watercraft have been injured by running into the fish while at speed. In 2003, a woman jet-skiing broke her nose and a vertebra by colliding with a silver carp, and nearly drowned. In another example, a leaping silver carp broke the jaw of a teenager being pulled on an inner tube. Water skiing in areas where silver carp are present is extremely dangerous. British biologist and angler Jeremy Wade was hit by one in the head while on the Illinois River filming for the second season River Monsters.
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