Mongabay · Climate & nature

Endangered Dolphins Persist in Highly Polluted Bangladesh River

A recent study has revealed the surprising survival of at least 20 endangered Ganges river dolphins in Bangladesh's Buriganga River, a waterway heavily contaminated by industrial and municipal waste.

Researchers observed Ganges river dolphins over a 12-month period in the 29-kilometer Buriganga River, which flows past the capital, Dhaka, and is considered one of the world's most polluted urban rivers. Dolphins were seen in 10 of the 12 months, with groups averaging four individuals and calves making up nearly 16% of sightings, indicating active reproduction.

The river's pollution levels, stemming from untreated industrial effluent and sewage, routinely exceed safety limits for toxic heavy metals. Dissolved oxygen levels drop near zero during the dry season, making the river "not livable for fish," according to a study co-author.

While native fish populations have collapsed, pollution-tolerant invasive suckermouth catfish have proliferated. Researchers hypothesize that the dolphins have adapted their diet to prey on these invasive fish.

Nationwide, a separate survey recorded 2,307 Ganges river dolphins across 4,900 km of Bangladesh's rivers.

Conservation efforts for the Buriganga dolphins must prioritize pollution reduction, alongside curbing destructive fishing practices and industrial discharges.

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