Black carp was accidentally brought to the US along with Grass carp for scientific research and fish farming (aquaculture). Young black carp and grass carp are very difficult to tell apart. They primarily eat mussels and snails and sometimes feed along the bottom of rivers and lakes. At one point, scientists thought they would be useful in eating a particular disease-carrying snail in fish farms. They have also been studied as a possible biological removal tool for zebra mussels. They are federally listed as injurious species, which means bringing these fish into the US or transporting them across state lines is illegal. This species hasn't been found near the Upper Mississippi yet (map).
For more information:
US Geological Survey