Hilsa production is declining after a steady rise over two decades due to water pollution from three power plants located near the Hilsa Sanctuary, siltation of rivers and overfishing, raising concerns about the much-loved fish’s sustainability and affordability.

“I am really worried about the hilsa population,” said Anisur Rahman, former director of the Bangladesh Fisheries Research Institute (BFRI), who has researched hilsa for many decades.

In fiscal 2024-25, hilsa production stood at 5 lakh tonnes, down 5.5 percent year-on-year, according to data from the Department of Fisheries.

Industrial waste and plastic pollution are among the most consistently cited factors behind hilsa’s decline across Bangladesh’s major river systems, but three power plants in Patuakhali and Barguna appear to pose the greatest threat.

A study published in the Bangladesh Journal of Physics in June 2025 found that the Payra thermal power plant is disrupting the reproduction, growth and survival of hilsa and other fish species in the area.

The coal-fired Payra power plant receives coal-carrying vessels, creating risks of oil spills, while fly ash and discharged wastewater could seriously affect the plankton-rich waters that serve as breeding grounds for hilsa, said Khorshed Alam, an associate professor at Barishal University, who led the study.

The study also recorded a water temperature change of up to 3.5 degrees compared with pre-operation levels.

This contamination has contributed to a 45 percent reduction in hilsa catch over the previous three years, Alam added.

Hasan Mehedi, an energy expert and chief executive of the non-governmental organisation CLEAN, has for years raised concerns about pollution from three power plants inside the hilsa sanctuary: the Payra power plant, the Patuakhali power plant on the Ramnabad channel bank and the Barishal power plant in Taltali on the Bishkhali river bank.

“These coal-fired power plants release their waste and hot water into the river. We have noticed a reduction in the hilsa population following the establishment of these power plants,” he said.

Worsening navigability of the Padma is not helping the hilsa population either.

Hilsa migrate from the sea into inland waters by swimming against the current, and a lack of river navigability and reduced water flow are creating obstacles to that migration.

“When they migrate to inland waters, they need current and also depth in the water. Hilsa need at least 10 meters of water depth in the river. But they are not getting that,” said the former BFRI director Anisur.

It is for this reason fishermen like Purna Das, from Sureshwar in Naria upazila, are unable to catch hilsa these days even though nearly 20 kilometres of the Padma in Shariatpur has been declared a hilsa sanctuary.

The 70-year-old has fished in the Padma for 30 years and has never seen conditions like this. His daily catch from the Padma used to be 120 to 160.

“Now there are no fish at all. Over the last two days, we cast our nets and caught only two hilsa and one fish of another species,” he said.

Over the past five years, hilsa production in Shariatpur has dropped significantly thanks to submerged shoals and river pollution, said Biswajit Kumar Deb, Shariatpur’s district fisheries officer.

Various barriers have formed along hilsa’s migratory route across the coast, including widespread illegal net use at the mouth of the Tetulia river, said Mir Mohammad Ali, an assistant professor at Sher-e-Bangla Agricultural University’s faculty of Fisheries, Aquaculture and Marine Science.

Across the Meghna near Hatiya and Bhola, the Rabnabad, Rangabali, and Taltali areas, and the Payra, Baleshwar, and Bishkhali areas, a severe lack of navigability is obstructing hilsa’s movement.

More than a hundred such barriers have formed along the coast, with illegal nets causing the main devastation, he said.

Hilsa migration is now blocked at 20 points, including the Meghna, Payra, Baleshwar, Bishkhali, Andharmanik, Tetulia, Sugandha, and Gozaria rivers, according to the Barishal Fisheries Office.

In some areas, depth has fallen to just 18-20 feet, far short of the 75-80 feet needed for breeding, and from Chandpur to Monpura, sandbars now block channels, leaving only narrow navigable routes.

Sedimentation in the estuary of all rivers in Taltali in Barguna, Kalapara in Patuakhali and in Bhola is creating obstacle for hilsa to come in the rivers, said Abul Kalam Azad, deputy director (Hilsa Management Section) at the Department of Fisheries (DoF).

When water levels fall, temperatures rise and water quality changes, disrupting the fish’s food chain -- a balance further unsettled by excessive heat and shifting rainfall patterns linked to climate change, said Anisur, who now teaches at Bangladesh Maritime University.

Increasing salinity in the river water is also hampering hilsa production, but the rise in temperature in the river water is harming the fish most, according to DoF’s Azad.

Asked whether power plants are the reason for the rise in water temperature, he said: “Yes, it could be, but I cannot say for sure as I did not do the research on this.”

What is most worrying is that the number of bigger hilsa is reducing, according to the hilsa researcher Anisur.

“Spawning response is better from the eggs of bigger fish. If we do not have many big fish in the river, it will affect the population in the next year,” he said.

The shrinking catch means hilsa will soon be out of most people’s means.

“I didn’t even bother asking the price of hilsa this season -- it is just too expensive,” said Arshad Mia, an employee of a private company in Karwan Bazar.

Similarly, Afzal, a fish vendor in Dhanmondi, said 80 percent of his regular customers could no longer afford hilsa this season.

“The price increased so much compared to last year.”

Last year, a hilsa weighing a kilogramme used to sell for Tk 2,200; this year, it is selling for Tk 3,200, he said.

Of the 11 hilsa-producing countries in the world, Bangladesh alone harvests around 80 percent of total global production. Nearly 7 lakh fishermen are directly engaged in hilsa fishing, and the fish contributes nearly 1 percent of the country’s GDP.

[Our correspondents from Barishal, Patuakhlali and Shariatpur contributed to the story]