Scientists Decode Extinct Sea Lion’s Genome, Confirming Overhunting as Cause of Extinction

A Jeju haenyeo holds a Dokdo sea lion (Gangchi). The Dokdo sea lion, which once lived in large numbers on the island, was hunted to extinction during the Japanese occupation. (Image provided by Professor Seo Kyoung-duk)

BUSAN, Aug.13 (Korea Bizwire) — A team of South Korean researchers has successfully decoded the full genome of the extinct sea lion species, known as Kangchi, which once inhabited Dokdo Island.

The breakthrough, the first of its kind in the world, provides scientific evidence that the species’ extinction was primarily caused by overhunting during the Japanese colonial era.

The extinct Dokdo sea lion, known as ‘Kangchi’, was once native to the waters around Dokdo Island. (Image courtesy of the Ministry of Oceans and Fisheries of Korea)

The National Fisheries Research and Development Institute (NFRDI) announced on Tuesday, that the research paper detailing the findings was published in the online edition of the international journal BMC Biology (Springer).

The study, which analyzed 16 bone fragments from Kangchi recovered from Dokdo and Ulleungdo islands, applied advanced ancient genome sequencing techniques to decode the sea lion’s genetic makeup.

Despite the challenges posed by the age and limited quantity of the samples, the researchers successfully sequenced the Kangchi genome. The analysis revealed that Kangchi diverged from the California sea lion around 2 million years ago, evolving into a distinct species.

Distribution and evolutionary history of the Dokdo sea lion (Kangchi) and related pinniped species (Image courtesy of the National Institute of Fisheries Science)

The study also uncovered traces of genetic exchange with other marine mammals, such as the Northern fur seal and the Stellar sea lion, providing new insights into the evolutionary history of North Pacific marine mammals.

One of the key findings of the research is that Kangchi maintained genetic diversity until its extinction, debunking the theory that genetic factors played a role in its disappearance. The research shows that overhunting, rather than a loss of genetic diversity, was the primary cause of the species’ extinction.

A representative from the NFRDI explained, “Some species fail to survive due to a lack of genetic diversity, but Kangchi maintained a healthy genetic pool until the end. This shows that overhunting, a human-induced factor, led to its extinction.”

The Kangchi was last confirmed to exist informally in Hokkaido, Japan, in 1974, and was officially declared extinct by the International Union for Conservation of Nature (IUCN) in 1994. The species is most closely related to the California sea lion and the Galápagos sea lion.

NFRDI President Choi Yong-seok stated, “By continuing research on the genetic characteristics of the diverse endemic species in our waters, we aim to strengthen our biological sovereignty.”

M. H. Lee (mhlee@koreabizwire.com

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