Juvenile bighead carp (Hypophthalmichthys nobilis) in the USA, where it is considered an invasive species. Bighead carp are native to China, but are now found in over 70 countries following import for use as food, and subsequent escape and proliferation. They, along with three other carp species, were introduced to the US in the 1970s to control parasites and plant growth in fish farms and canals. They later escaped into the Mississippi river during flooding and rapidly established breeding populations. They pose a threat to native species by increasing the competition for plankton.