What is taking a toll on Halda’s dwindling freshwater dolphins?
46 dolphins died in Halda River over past eight years
Over the past eight years, at least 46 freshwater dolphins – locally known as shushuk or hutom – have died in the Halda River of Chattogram, once considered one of the safest habitats for the endangered Ganges River Dolphin.
The death toll is rising every year, driven by human activity and environmental degradation, researchers said.
They attribute most of the deaths to five key causes: injuries from engine-propelled boats, stones, or fishing tools; entanglement in fishing nets; targeted killing for fat extraction; poisoning from pollution; and natural causes. The first three factors account for most of the deaths.
The Halda River, South Asia's only natural carp breeding ground, has long been home to the Ganges River Dolphin (Platanista gangetica), listed as endangered by the International Union for Conservation of Nature. Globally, the species' population is estimated at just 1,100 to 1,200.
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Halda, once considered the species' most secure refuge, saw the 46th recorded dolphin death on 25 August this year.
"Since September 2017, 46 dolphins have died in Halda," said Professor Dr Md Manzurul Kibria, coordinator of the Halda River Research Laboratory at the University of Chittagong.
Dr Kibria suggested eight measures to rein in the rising death incidence: declaring Halda a dolphin sanctuary, banning dredgers and motorised boats, prohibiting net-based fishing, removing rubber dams from the river's upstream and tributaries, enforcing wildlife and fisheries laws, bringing the river under CCTV surveillance, and ramping up public awareness.
Pollution, nets, and engines taking a toll
Research by the Halda River Research Laboratory shows that over 90% of the dead dolphins had visible injury marks, suggesting most died after collisions with boat propellers or entanglement in fishing nets. A dolphin trapped in a net can die within 30 minutes if not released, researchers noted.
"Despite being declared a heritage river, Halda's dolphins remain at risk," said Yasin Newaz, divisional forest officer of the Wildlife Management and Nature Conservation Department in Chattogram. "Any development activity in Halda must factor in biodiversity conservation concerns. Otherwise, we risk losing this species from the river."
A shrinking population
A 2018 survey by the Halda River Research Laboratory found around 167 dolphins in the river. By 2020, the number had fallen to 127. Although a 2022 survey counted 147 dolphins, researchers warn that the population remains unstable due to continued human activities.
A total of 18 dead dolphins were found in the Halda River between September 2017 and February 2018. Another 10 were recovered between March 2018 and December 2020, followed by five in 2021 and six in 2022.
While no deaths were recorded in 2023, four dolphins were found dead in 2024 and three more up to 25 October 2025.
Another Halda researcher, Dr Shafiqul Islam, said, "If water pollution cannot be controlled, the dolphin population will keep shrinking." He urged the government to make a coordinated effort to save the endangered species.
Why species matters
The Ganges River Dolphin plays a vital ecological role as a top predator in the freshwater food chain and serves as a key indicator of river health. Protecting this species also helps conserve other aquatic life such as softshell turtles, gharials, and small cetaceans.
The World Freshwater Dolphin Day has been observed on 24 October since 2009 to promote conservation of and awareness about the species.
Bangladesh has observed the day since its inception. This year's theme "Nodir pran dolphin-shushuk, nirapode beche thakuk" (Dolphins, the life of our rivers, may have a safe life) – underscored the urgency of saving the species from pollution and human threats.
Scientists warn that, if urgent action is not taken, Bangladesh could lose one of its most iconic river species – once a living symbol of the country's vibrant waterways.
