Asian carp include several species like silver carp and bighead carp. They were brought to the US as a food fish but have escaped into waterways and spread, damaging native populations of fish. Some species of Asian carp can grow to four feet long and weigh 100 pounds. They can consume up to 40 percent of their body weight in plankton each day, removing huge amounts of food needed at the beginning of the food chain, and also making it harder for native plankton eaters like paddle fish to survive.
When the Asian carp got into the Mississippi River they spread fast and are now found in all most tributaries of the river system. The fear is they will get into the Great Lakes through canals and, if so, be a serious problem to native fish species.
Electronic "gates" were established to stop the spread. These gates are narrow places in the waterway, often near locks, where an underwater fence is set up under the water. The gate is the only opening and it is to allow boats to pass. A low electric charge goes through the water to turn back the fish.
Recently sections of the canals leading into locks near the Great Lakes were poisoned to kill all the fish in them. This was to stop the spread of the Asian carp. Although the Rotenone used kills all the fish in the area, it was decided it was worth the loss of desirable fish to get rid of the carp in the area.