Ecological Risk Screening Summary - Dikerogammarus caspius (an amphipod, no common name) - Uncertain Risk

Species that are considered uncertain risk need a more in-depth assessment beyond the Risk Summary to better define the species’ risk to U.S. environments.

Dikerogammarus caspius is a Ponto-Caspian amphipod species native to the northern Caspian Sea. The exact native range of this species is not known, but it is documented to be established in the Volga River Delta and upstream to Saratov Reservoir via natural dispersion. It is also established in the Taganrog Gulf of the Sea of Azov and in the Don River basin. The means of its introduction to these environments is not known. The history of invasiveness is classified as Data Deficient due to a lack of peer-reviewed information about the invasive potential of D. caspius. There are statements that it displaces native amphipods, but the supporting information was not available to assess. There was a High climate match with the contiguous United States, especially in the Great Lakes basin and interior West, but it has not been reported as introduced or established in the United States. The certainty of this assessment is Low due to a general lack of information and lack of georeferenced observations of D. caspius in its the native range. The overall risk assessment category is Uncertain.