Joint research team discovers why male hilsa shad fish are disappearing

A joint team of researchers from Shanghai Ocean University and Jagannath University in Bangladesh has unveiled three groundbreaking discoveries about the hilsa shad, marking a milestone in international cooperation on the study, management and conservation of Bangladesh's national fish.

The findings were led by three Bangladeshi researchers — Md Rashedur Rahman, Kishor Kumar Sarke and Anirban Sarker — all of whom earned their doctorates from the Lab of Molecular Systematics and Ecology at Shanghai Ocean University.

Their research focused on three key areas: the sex reversal, whole genome sequencing and population genomics of the fish.

Notably, Rahman, who completed his doctorate in Shanghai and returned to Bangladesh in December, was the first to confirm that hilsa shad undergo sex changes. Through biological and histological analyses of 203 samples from six regions, including the Padma River, Meghna River and the Bay of Bengal, his study found that the species exhibits "protandrous hermaphroditism", meaning individuals transition from male to female at a certain stage of their life cycle.

This discovery sheds light on the long-standing puzzle of the apparent scarcity of male hilsa shad, providing key insights into their life cycles, reproductive strategies and sexual transition mechanisms.

"The hilsa shad, a flagship species in Bangladesh, holds immense economic and ecological value. These findings not only deepen our understanding of its biological characteristics, but also provide a scientific foundation for its conservation and sustainable management," said Huang Xuxiong, executive deputy dean of the College of Fisheries and Life Science at Shanghai Ocean University.

Li Chenhong, a professor at Shanghai Ocean University and supervisor of the lab, said the discoveries resulted from nearly a decade of research by three classes of Bangladeshi students.

"We hope these results will contribute to the conservation and sustainable use of hilsa shad, and we also hope that educational cooperation between the two universities will continue to yield fruitful results," Li said.

The two institutions have strengthened collaboration over the past decade in aquaculture, resource conservation and marine ecological monitoring. Since 2016, they have exchanged scholars, jointly trained doctoral students and conducted academic exchanges and research projects. In 2019, they signed a memorandum of understanding and cooperation agreement to further enhance long-term scientific research under the Belt and Road Initiative.

Huang noted that the hilsa shad species in Bangladesh is closely related to China's, offering potential for aquaculture innovation. The collaboration has advanced research on artificial breeding technologies for the fish and has created new opportunities for China and Bangladesh in aquaculture, biodiversity conservation and marine economic development.

"Bangladesh, with its rich aquatic resources and extensive coastline, shares significant potential with China in developing the blue economy," Huang said. "Through collaboration, we aim to explore pathways for sustainable marine economic growth, contributing to prosperity in both nations and beyond."

wangxin2@chinadaily.com.cn