A joint research project between the Department of Zoology at Jagannath University (JnU) and the Department of Hydro-biology at Shanghai Ocean University has unveiled insights into ilish.
The research, focused on the fish's sex reversal, complete genome, and population genomics, marks a significant step forward in understanding this vital species.
The findings were presented at a seminar and press conference held at JnU's Department of Zoology on Thursday morning.
The event was attended by notable figures, including JnU’s Vice-Chancellor, Professor Md Rezaul Karim, who served as the chief guest. The seminar was chaired by the Department of Zoology's Chairman, Professor Abdullah Al Masud, with special guests including Treasurer Professor Dr Sabina Sharmin, Dean of the Faculty of Life and Earth Sciences Professor Dr Mallik Akram Hossain, Additional Director-General of the Department of Fisheries Md Zia Haidar Chowdhury, and Director of Research at JnU, Professor Dr Imranul Haque.
A total number of 203 ilish fish, collected from six regions of the Padma, Meghna, and Bay of Bengal, exhibited signs of sex change. Among the collected samples, seven displayed both sperm and eggs within their gonadal tissues, supporting the hypothesis of gender reversal.
According to the study, ilish fish initially reproduce as males during their first year of life, before migrating to the sea. Over time, they gradually transform into females, eventually returning to the rivers for reproduction in their second year.
Researchers believe this discovery will be instrumental in unlocking the full life cycle and reproductive strategies of ilish, contributing to future conservation efforts and understanding of the species' behavior.
The research team sequenced the complete genome of ilish for the first time. The genome sequencing, coupled with RNA analysis from nine different tissues of 14 ilish fish from both sea and river habitats, revealed insights into the fish's oil content and flavor. The team has made all genetic data publicly available through the NCBI database.
The research also highlighted a concerning finding: Ilish in Bangladesh exists as a single population, posing a significant risk to its survival. Should this population face environmental or pollution-related threats, there is a real danger of the species becoming extinct in the region.
The genetic variation among ilish is low, making them less adaptable to changes. While production levels have increased, the fish remains vulnerable to extinction, underscoring the need for integrated management and greater public awareness to protect this critical species.
Dr Kishore Kumar Sarker, a lecturer at Shanghai Ocean University, shared his thoughts on the research, saying: “Studying ilish's reproduction was a risky venture. Its reproductive process works differently in rivers and seas, making the research even more challenging.”
Professor Dr Chin Hongli, also from Shanghai Ocean University, joined the seminar online and praised the research team's dedication, saying: “This study on ilish has been years in the making, and it is the result of immense hard work from many individuals. We are grateful for everyone's contributions.”
JnU’s Vice-Chancellor, Professor Md Rezaul Karim, expressed his admiration for the research team, saying: “The way our researchers have embarked on studying ilish fish is truly commendable. I am hopeful that these exceptional studies will play a key role in conservation efforts and contribute to the scientific community on a national level.”
