Distribution records of domestic alien bitterling fishes based on the literature

Abstract

Bitterlings (subfamily Acheilognathinae) are a group of small cyprinid fish, comprising 16 taxa (11 species and 8 sub-species) distributed in Japan, where all bitterling taxa are endangered. Because bitterlings are popular as pets and fishing targets due to their attractive and diverse nuptial colouration, they have been released deliberately in various regions, even outside of their native ranges. Therefore, many Japanese bitterling populations are recognised as domestic alien fishes that pose a major threat to native bitterling populations. In this study, we summarise comprehensively the geographical distribution, control and eradication attempts, and establishment status of domestic alien bitterling populations based on the literature. Our results showed domestic alien distribution in 14 bitterling taxa. Acheilognathus cyanostigma has been recorded as a domestic alien species in 19 prefectures, and Acheilognathus rhombeus, Acheilognathus tabira tabira, Tanakia lanceolata, and Tanakia limbata have been recorded as domestic alien species in more than 10 prefectures. Notably, there have been many invasions in the Tohoku region, which is inhabited by few native bitterling species. No records of projects to control or eradicate domestic alien populations were found. We discuss the possibility of naturalisation in both channels and still waters, as well as hindering pathways toward their introduction outside of their native ranges, based on the naturalisation records summarised in this study.