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教育・研究

Genome analysis reveals population dynamics of Japanese eels over historical time scales

【2021.11.24】
 Grilled Japanese eel is an iconic delicacy that is traditionally eaten during summer, especially on doyou-no ushi-no-hi, to boost stamina in the hot and humid weather. However, in recent years the cost of Japanese eel dishes has increased considerably because the number of eels caught in the wild and grown in aquaculture has
decreased. In fact, only 11.1 tons of eel were caught in Japan in 2021, compared to approximately 3000 tons in the 1970s. This pattern indicates that the overall population size of Japanese eel has also greatly decreased. Indeed, Japanese eel is now listed as an endangered species by the IUCN. Researchers at Nagano University’s Institute of Freshwater Biology have been conducting genomic analyses to determine both the current and past population size of Japanese eel. By investigating historical changes in the population size of Japanese eel it is possible to gain a better understanding of current population dynamics. The study, which is now available on bioRxiv (https://biorxiv.org/cgi/content/short/2021.11.18.468312v1), found that Japanese eel experienced reductions in population size during the Pliocene (1-4 million years ago) and around the time of the last glacial maximum (19-33 000 years ago). These events were most likely caused by changes in sea level and oceanic currents that restricted Japanese eel’s natural reproductive processes (drift of larvae and/or migration of adult fish). These population declines or bottlenecks may make Japanese eel more sensitive to current and future population declines. Research on the current population size of Japanese eel is ongoing.
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