A study of genetic variations, population size, and population dynamics of the catadromous Japanese eel Anguilla japonica (Pisces) in northern Taiwan

Japanese eels are widely distributed in northeast Asian countries, and they have a catadromous life history. In this article, we explored whether Japanese elvers have temporal genetic structure and whether the population went through population expansion during the Pleistocene. In total, 273 specimens were collected from the Tanshui River estuary, northern Taiwan, in 1989–2008. The highly variable region of the mitochondrial DNA D-loop was cloned and sequenced. A genealogy was reconstructed based on the Neighbor-joining method, and results showed an unobvious yearly clade and a high level of haplotype diversity, but low mean nucleotide diversity among samples. Most of the pairwise F ST appeared statistically insignificant. These genetic parameters suggested a lack of temporal population structure combined with a sustainable high effective population size of Japanese eels. Negative values of Tajima’s D and Fu’s F s appeared in all samples with high significance. The mismatch distribution, skyline plot, and minimum spanning network indicated that historical population expansion of the Japanese eel could be traced back to the Pleistocene. Results of this study imply the Japanese eel has a complex life history, and the temporal structure of Japanese eels should be continually monitored in the future.