Rhodeus amarus; Print; The European bitterling (Rhodeus amarus) is a temperate freshwater fish belonging to the Acheilognathinae subfamily of the Cyprinidae family. It originates in Europe; ranging from the Rhone River basin in France to the Neva River in Russia. It was originally described as Cyprinus amarus by Marcus Elieser Bloch in 1782; and has been referred to in scientific literature as Rhodeus sericeus amarus. It is known simply as "the bitterling" in its native range; where it is the only species of its genus Rhodeus; and sometimes in the scientific literature; also; but this is technically wrong; being a leftover from the times when the European bitterling was united with its Siberian relative; the Amur bitterling; in R. sericeus. Properly; "bitterling" can refer to any species of Acheilognathus or Rhodeus.; 1774-1804