Species that are considered high risk have a well-documented history of invasiveness in at least one location globally, and a high or medium climate match to the contiguous United States.
Hypophthalmichthys nobilis, the Bighead Carp, is a carp species native to China. This species has a high history of invasiveness: since being introduced to the U.S. via aquaculture in the 1970s, it has escaped captivity and spread rapidly in the Mississippi and Missouri River basins. Negative impacts to the U.S. caused by H. nobilis and its congener H. molitrix include alterations to the zooplankton community and lowered body condition of native planktivores. H. nobilis has a high climate match with the contiguous U.S. Certainty of this assessment is medium because information available on negative impacts of this species to the U.S. did not distinguish between the effects of H. nobilis and H. molitrix. Despite this, the overall risk assessment category is still High.