Organized activities for conserving a critically endangered freshwater fish, Rhodeus ocellatus kurumeus: An attempt to eradicate the population contaminated with Rhodeus ocellatus ocellatus by pond drying and fish removal

Japanese rose bitterling, Rhodeus ocellatus kurumeus, is an endangered freshwater fish in Japan. Both the expansion of the habitat of an alien subspecies, R. o. ocellatus, and the increased chances of hybridization between the two subspecies have threatened the genetic identity of R. o. kurumeus. To conserve R. o. kurumeus in Kagawa Prefecture, 17 populations were genetically monitored in 2006. Two individuals in a pond were found to harbor R. o. ocellatus type mitochondrial DNA through PCR-RFLP analysis. Then the contaminated population was transplanted to a closed Bio-top water system to prevent contamination in other ponds. Three-day pond drying was found to be insufficient to eradicate R. ocellatus.