Thanks to its river-rich geography and favorable weather, Bangladesh produces about 86 percent of the world’s hilsa. Although hilsa is a marine fish, it swims upstream into fast-flowing rivers to lay its eggs. But hilsa is a very sensitive species—it often changes course in response to sudden weather shifts. Recently, climate change has started affecting the fish’s natural habitat and behavior in Bangladesh too. Pollution in rivers is also taking a toll, reducing overall production.
Experts explain that hilsa usually travels from saltwater into freshwater rivers to spawn. After laying eggs, it floats back downstream toward the sea. But for this journey to happen smoothly, strong river flow is essential. During the monsoon, especially between July and October, the water in the lower Meghna River becomes clear and less salty, which attracts the fish. At the same time, the tides and strong currents help hilsa move inland. The fish also needs plenty of oxygen during spawning. Since river water tends to be more turbulent in the rainy season, oxygen levels are usually higher. Water temperature is another crucial factor—it directly affects the timing of egg-laying. A slight change in temperature can cause female hilsa to abandon or destroy their eggs.
But now, with growing river pollution, encroachment, sedimentation, and infrastructure development, along with the effects of climate change, the hilsa’s breeding cycle is facing serious disruption. As a result, reproduction is under threat.
According to the Department of Fisheries, hilsa production in 2008–09 was 298,000 tons. By 2017–18, it had nearly doubled to around 517,000 tons. But after that, things started slowing down. In fact, in the last fiscal year, production dropped instead of increasing. In 2022–23, Bangladesh caught 571,000 tons of hilsa. But in the following year, that number dropped to 529,000 tons—a decline of 42,000 tons.
Experts believe pollution is one of the biggest reasons for this drop. They point out that the pollution from the Buriganga River in Dhaka flows into the Shitalakshya and then into the Meghna—one of the main routes for hilsa. With growing pollution in these rivers, hilsa movement is shrinking. Dr. Niamul Naser, Professor of Zoology at the University of Dhaka, told Bonik Barta, “When oxygen levels drop due to pollution, fish start leaving that area. Hilsa behaves the same way—when it senses polluted water in the Padma or Meghna, it avoids the region for spawning.”
Hilsa, the national fish of Bangladesh, also has Geographical Indication (GI) status. According to WorldFish, Bangladesh produces 86 percent of the world’s total hilsa.
There are four major breeding grounds and six sanctuaries for hilsa across the country. The largest breeding zone stretches from Mirsharai in Chattogram to Lalmohan in Bhola. Within this zone, the top egg-laying spots are Monpura, Dhalchar, Balirchar, and Maulovir Char. Hilsa lays the most eggs in about 7,000 square kilometers across Chattogram, Bhola, Lakshmipur, Noakhali, Chandpur, Patuakhali, and Barguna. Researchers say the fish also spawns in other coastal rivers outside these zones.
Most of the sanctuaries are located in the Meghna River and its basin, along with the confluence of the Padma and Meghna rivers. Key protected areas include 100 kilometers of the lower Meghna in Chandpur, 90 kilometers of the Shahbazpur branch in Bhola, and nearly 100 kilometers of the Tentulia River. Additionally, 20 kilometers of the Padma and about 82 kilometers of the Meghna near Hizla and Mehendiganj in Barisal are also marked as hilsa sanctuaries.
People involved in the hilsa industry say silt is building up in different parts of the Meghna River, forming new shoals and underwater barriers right where the fish are supposed to pass through from the Bay of Bengal. Because of this, many mother hilsa are turning back to the sea instead of entering the freshwater to lay eggs. At the same time, the hilsa fry that hatch in the river cannot make their way out to the ocean to grow. On top of that, due to climate change, rainfall during the monsoon has also gone down in recent years. That is reducing the layer of freshwater and raising the temperature—both of which are stressing the hilsa and young jatka trapped in the Meghna.
Although fishing is supposed to be restricted during certain seasons, many dishonest fishermen continue to catch mother hilsa and jatka freely. It is another reason the hilsa population in the Meghna is falling fast.
Solaiman Bepari, a fisherman from Hizla upazila in Barisal who fishes on the Meghna river, said they barely get any hilsa in the river these days. “We still catch some in the sea, but in the river? Almost nothing. The amount of hilsa we used to catch two or three years ago has dropped by half,” he said. He blames the underwater shoals near the river mouth and the overuse of fishing nets for blocking hilsa from coming upstream.
Mohammad Alam, a senior fisheries officer in Hizla and Mehendiganj upazilas of Barisal, told Bonik Barta that the underwater shoals near the sea mouth are reducing the river’s navigability. “With less tidal flow, it’s getting harder for hilsa to enter the rivers. That’s why we’re seeing fewer fish in the river system. If we dredge those shoals and restore the flow, hilsa migration and breeding will bounce back.”
Fisheries researchers explain that hilsa naturally swim in a straight path. When they hit an obstacle, like a shoal, they do not look for an alternate route—they just turn back. Professor Dr. Muhammad Abubakar Siddique, Dean of the Faculty of Fisheries at Patuakhali Science and Technology University, told Bonik Barta, “The availability of hilsa in our rivers is falling because of the siltation near the sea mouths. And climate change is playing a major role too. If the water temperature isn’t right, hilsa avoid those areas and move into the deep sea. But our fishing boats don’t have the kind of equipment needed to go that far. So, we need to remove those underwater shoals near the sea mouth as soon as possible.”
Studies have shown that river pollution directly affects fish movement. For instance, water needs to have a balanced pH level. If it drops below 7, the water quality degrades and becomes unlivable for fish. Similarly, low dissolved oxygen levels also make it impossible for fish to survive.
Dr. Md Mohinuzzaman, Chairman of the Environmental Science and Disaster Management Department at Noakhali Science and Technology University, said hilsa—being a marine fish—are especially sensitive to these changes. “Our ship-breaking industry is releasing dangerous levels of heavy metals into the rivers. Oil spills and industrial waste are making things worse. Hilsa also need a certain amount of open space to swim and breed. But rivers are being narrowed by dams and development projects, and new shoals are appearing in many places. All of this is hurting both their breeding and the overall catch,” he explained to Bonik Barta. “We’re simply not thinking seriously about river pollution or the habitat needs of hilsa and other fish.”
The Meghna River flows into the Bay of Bengal through Chandpur, Lakshmipur, and Hatia in Noakhali. Out of these, the 37-kilometer stretch of the Meghna estuary across four upazilas in Lakshmipur is considered one of the most important breeding and production zones for hilsa. Hilsa caught in this area are in high demand and sent to major cities like Dhaka and Chattogram. But in recent years, even during peak season, the river is not yielding as many fish as it used to. According to local fishermen, 70 to 80 percent of the hilsa they catch now come from the sea—not the river.
Dr. Anisur Rahman, a leading hilsa researcher and former Chief Scientific Officer at the Riverine Center of the Bangladesh Fisheries Research Institute (BFRI), said it is quite normal that fewer hilsa are now being found in the Chandpur region. “It’s happening because of pollution in rivers like the Buriganga and Shitalakshya, and the growing number of shoals and underwater barriers in the Padma and Meghna,” he explained. “We’re just casting our nets and catching hilsa from the river, but we’re not doing anything to clear their migration paths. Do we ever dredge the rivers to make way for the hilsa? Dredging only happens when ferries get stuck—nothing more.”
Researchers point out that many of the rivers where hilsa usually swim—especially the Padma and Meghna—now have industrial zones along their banks. These factories release untreated liquid waste directly into the rivers. To the naked eye, this pollution may not seem harmful. But over time, it changes the water quality and disrupts the breeding of hilsa and other fish.
Dr. Abdullah Harun Chowdhury, a professor in the Environmental Science Discipline at Khulna University, explained this further to Bonik Barta. He said, “It’s not just the Padma and Meghna—hilsa catches are also declining in big rivers like the Pashur. Industrial pollution is changing the quality of river water. In some places, hilsa have completely stopped coming. And even if they do show up, they often leave without laying eggs. In other cases, they lay eggs, but the eggs don’t hatch properly. Sometimes the eggs are damaged, and sometimes the gender balance of the offspring is disrupted. Normally, each generation produces both male and female fish—but lately, that balance is off. All of this is linked to pollution. If we don’t get river pollution under control, we’ll see even fewer hilsa in our freshwater rivers in the future.”
Farida Akhter, Fisheries and Livestock Adviser, recently emphasized the environmental impact as well. “Climate change is increasing salinity, and that directly affects hilsa. There’s also a strong link between rainfall and hilsa spawning. Researchers should look into what we can do in the face of climate change. If we can manage hilsa properly, we can proudly introduce it to the global stage. So, we need to promote hilsa internationally.”
(Report compiled with assistance from Bonik Barta’s Barisal and Chandpur correspondents.)