Ecological Risk Screening Summary - European Bitterling (Rhodeus amarus) - 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.

European bitterling (Rhodeus amarus) is a minnow species native to much of eastern Europe and western Asia. The method of reproduction is worth noting as it parasitizes unionid mussels with its eggs and larvae. R. amarus also has a history of human usage in the ornamental trade, in aquaculture, and as bait fish. The history of invasiveness is High. The species has been introduced outside of its native range in Europe and western Asia and has established populations. It was probably introduced to New York (some uncertainty if introductions are R. amarus or R. sericeus). If this is the species that was introduced, there is a possibility of a persisting population in the Bronx River. In a European location that may be outside the native range, the parasitic spawning method of the fish reduces mussel fitness and potentially abundance as mussels parasitized during R. amarus reproduction showed significantly reduced growth. The overall climate match was high for the contiguous United States. Small areas of low match could be found in coastal areas of the Southeast and in pockets in the west; everywhere else had medium and high matches. The certainty of assessment is medium. Scientifically defensible information on impacts of introductions was available but there is also the difficulty in determining what information actually pertains to R. amarus due to the long history of taxonomic confusion with R. sericeus. The overall risk assessment category is High.