Bighead carp, also known by its scientific name Hypophthalmichthys nobilis, is a large freshwater fish that is native to China. It is also commonly known by its Thai name, Tongsan, and other common names, such as noble fish, lake fish, or speckled amur. There have been some limits placed on introducing this fish into waterways and selling the fish in certain areas, such as Canada and the United States, because it competes against native species for food.
Bighead carp has a large head that is free from scales. It also has a large, toothless mouth with a protruding lower jaw. The eyes of the fish are low on its head and project downward. Generally, these fish are silver or gray in color, sometimes with black mottling. In addition, these fish can grow quite large. There have been reports of fish that reach nearly 100 pounds (45.4 kg), although most only grow to about 40 pounds (18.1 kg).
Although bighead carp generally prefer to eat zooplankton, they will eat other food sources if zooplankton is not available. They are filter feeders, meaning they are capable of filtering water through their gills. Using this filtering process, they only eat the food that is tiny enough to fit through their feeding filter, such as phytoplankton and zooplankton.
Interestingly, bighead carp was not introduced to the United States until the 1970s, when it was brought to Arkansas from China. The purpose of the introduction was to manage the growth of algae in freshwater ponds in the area. Unfortunately, this species of carp was unable to be contained.
Within less than ten years time, after its introduction to the United States, there were records indicating that these fish could be found in major rivers around the country. During the 1990s, when flooding was more severe, many more bighead carp managed to escape from their algae-filled ponds. The result was that they headed into the Mississippi River basin and quickly spread into many large rivers, such as the Mississippi and the Missouri. When these fish are in the same bodies of water as native species, the native species usually do not survive. This species of carp tends to consume large quantities of food, forcing other fish to perish.
Some areas have strict laws prohibiting big head carp from being introduced to local waters. In addition, some states in the United States and certain provinces in Canada forbid the sale of any bighead carp that is alive. Researchers are fearful that the fish will make its way to additional bodies of water, such as the Great Lakes, and compete with the native fish there.