Ecological Risk Screening Summary - Ruffe (Gymnocephalus cernua) - High Risk

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.

Gymnocephalus cernua, Ruffe, is a freshwater and brackish water fish native to numerous countries in Europe and Asia. It has been introduced accidentally via ballast water or intentionally as a bait species in the Great Lakes region of North America, France, Italy, Turkey, Algeria, and in areas outside of its native range in Germany, Georgia, Norway, and the United Kingdom. Most of these introductions have resulted in population establishment. The History of Invasiveness for G. cernua is classified as High due to its documented predation on eggs of native fish species and competition for their food resources, potentially contributing to native species declines. The transportation, possession, and sale of Gymnocephalus cernua has been regulated by more than twenty U.S. States and one Canadian province because of these documented negative impacts. The climate matching analysis for the contiguous United States indicates establishment concern for this species. The climate match was high across most of the contiguous United States, and especially where the species is already established in the northern Great Lakes region. The Certainty of this Assessment is Medium due to some disagreement in the literature about the degree to which G. cernua has contributed to native species declines. The Overall Risk Assessment Category for G. cernua in the contiguous United States is High.