About 20 dolphins found in Bangladesh’s polluted Buriganga River
Scientists have found about 20 Ganges river dolphins in the Buriganga River near Dhaka, Bangladesh, despite the water body’s critical pollution from industrial effluent, untreated sewage and garbage. The study, published in the Journal of Asia-Pacific Biodiversity, covered a 27-kilometer section of the river and lasted from September 2023 to August 2024.
According to Mongabay, dolphins were not recorded in October 2023 or in July-August 2024. The largest number of animals was observed in December and throughout the winter season. The average group size was 4.18 individuals, while calves accounted for nearly 16% of observations, indicating that the species continues to reproduce.
Toxic pollution of the Buriganga
The 29-kilometer-long Buriganga receives effluent from hundreds of enterprises every day, including leather, textile, dyeing, battery and metal-processing facilities. Chromium, lead, cadmium, arsenic, mercury, nickel, copper and zinc have been found in the water and bottom sediments, with levels regularly exceeding national norms and World Health Organization standards.
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During the dry season, the concentration of dissolved oxygen in the water often approaches zero, while the environmental standard is 5 milligrams per liter. Studies link pollution to declining populations of local fish species and biodiversity loss. Canadian nonprofit organization Sea Smart has named the Buriganga the world’s fifth most polluted river.
Threats to river dolphins
Mohammad Abdul Aziz, a professor of zoology at Jahangirnagar University, suggested that the dolphins may prey on the invasive suckermouth catfish Hypostomus plecostomus, which is distinguished by its resistance to pollution. According to him, preserving the dolphins requires first and foremost stopping pollution, as well as limiting excessive vessel traffic that disrupts their natural movement.
A separate 2024-2025 survey by the Bangladesh Forest Department and WCS Bangladesh recorded 2,307 Ganges river dolphins in 45 rivers across the country. Experts also note that illegal fishing and the use of nets in which dolphins become entangled and die threaten the species.
