‘Declare Halda as dolphin sanctuary’

Prof Dr Manzoorul Kibria is the chairperson of Chittagong University's zoology department. Born and brought up in a village that borders the banks of Halda river, he grew up with a great passion for rivers. After graduating from the same university, he decided to pursue research on Halda, writing a good number of articles on it for national and international journals. Currently working as the co-ordinator of CU's Halda River Research Laboratory, he was one of the visionaries who brought the lab into being in 2017.

He recently talked to The Daily Star over Halda's dwindling Ganges dolphin population, elaborating the scenario and suggesting steps for a way out.

DS: What makes Halda so important?

Manzoorul: Halda has some exceptional characteristics. It's the only river where eggs from indigenous carp fish can be collected directly. It's also the lone natural gene bank of country's indigenous carp fish. Besides, it's a major habitat of the endangered freshwater Ganges dolphins (Platanista Gangetica).

The river plays a vital role for the national economy, contributing around Tk 800 crore a year. It's also one of the main sources of the city's drinking water. Chattogram Wasa collects 18 crore litres of water from the river every day, which is then purified and supplied to city dwellers. There is a reason why it's called the lifeline of the city.

DS: Speaking of the Ganges dolphins, what is their role in the ecosystem?

Manzoorul: Dolphins are an integral part of the area's ecosystem, to the point that their conservation can benefit a wider range of aquatic and threatened species, including turtles, gharials and otters.

DS: What are the reasons behind their slow disappearance from the Halda?

Manzoorul: It's true that the species has been disappearing from Halda at a worrying rate over the last few years. The reasons are entirely human-made. Most of the blame can be attributed to engine boats and unsustainable fishing practices. Since 2017, a total of 50 dolphins have been killed in the river.

According to the records, engine boats are the main cause, as they killed the most number of dolphins by hitting them. We conducted our first autopsy on a dolphin carcass in 2018 and found that it died after suffering injury from a sharp propeller.

Fishing nets come in second -- dolphins get stuck on them and suffocate to death. Then there are hunters who kill dolphins for their fat.

We have submitted a six-point recommendation to the authorities in 2018, which included a ban on plying mechanised boats in the river, not allowing grill nets for fishing in the river and declaring it as a sanctuary for dolphins.

The authorities complied with most of our recommendations; as a result, the rate of death has decreased to a great extent.

For example, a total of 18 dolphins were killed in five months between September 2017 and February 2018, while a total of 32 dolphins were killed in the three years between February 2018 and December 2021.

DS: What more steps can be taken to save Halda's dolphin population?

Manzoorul: Besides the points we have already recommended, taking legal action against mills and factories that pollute the river can help immensely. Moreover, locals should be made aware regarding dolphin conservation.