Information about the habitats and status of bitterling species (Acheilognathinae) is limited even though 9 out of 14 native species in Japan are listed in the Red Data Book. To collect such information, we captured fish in Mondori traps and measured environmental features such as current velocity and electric conductivity at 126 points in 13 sites along the shore of Lake Kasumigaura. An alien species, Rhodeus ocellatus ocellatus, was most abundant, followed by two native species, Acheilognathus tabira subsp.1 and A. melanogaster. Of the two other native species that have been recorded in the lake, Tanakia lanceolata was captured in only 4 sites, and A. typus was not captured at all. On the other hand, A. macropterus, which was introduced in about 2000 at an estuary along the southern shore, was captured in 7 widely scattered sites in the lake. Generalized linear mixed models revealed that the occurrence of two native species, A. tabira and A. melanogaster, was negatively related to electric conductivity and/or concrete ditches, while the occurrence of R. o. ocellatus, the most successful alien bitterling species, was positively related to electric conductivity and concrete ditches, suggesting that R. o. ocellatus may have a higher tolerance than native bitterlings to habitat degradations such as eutrophication and concrete ditches.
