Ecological Risk Screening Summary - Tiger Scud (Gammarus tigrinus) - 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.

The Tiger Scud (Gammarus tigrinus) is a euryhaline amphipod native to estuaries along the Atlantic Coast of North America. G. tigrinus tolerates a wide range of environments, and has been introduced to other parts of North America, Europe, and South America, mainly via ship ballast water. The importation of G. tigrinus is regulated in Hawaii. The History of Invasiveness is classified as High. G. tigrinus has caused changes to macroinvertebrate communities where introduced, displacing native gammarids. G. tigrinus has also acted as an intermediate host for nonnative parasites introduced to European eels (Anguilla anguilla). The climate matching analysis for the contiguous United States indicates establishment concern for this species outside its native range. Areas of high match were found in the eastern half of the contiguous United States, including the native range, and in patches in the Western Mountains and Colorado Plateau. The Certainty of Assessment is High. The Overall Risk Assessment Category is High.