Dolphins disappearing from Halda
On October 4, a dead dolphin washed up on the shores of Hathazari upazila's North Madarshah Ramdas Munshirhat area.
Chittagong University's Dr Manzoorul Kibria, professor of zoology department and Halda researcher, suspects it might have died from being suffocated on a stray fishnet -- a recurring issue on the river.
This follows another dead dolphin -- around five-feet long, weighing 30kg, that washed up in the same area four days earlier on September 30.
The Halda river is an important habitat of the endangered freshwater Ganges river dolphins (Platanista Gangetica). The 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.
But despite this, the species is disappearing from the river at a worrying rate over the last few years.
And experts say the reasons are entirely human-made, with a majority of the blame going to fishing practices in the river.
According to Prof Kibria, a total of 49 dolphins have been killed in the river Halda since 2017.
Kibria, also coordinator of the Halda River Research Laboratory of Chittagong University, said they conducted the first autopsy of one such dolphin carcass in February 2018. It was found that the cause of death was an injury caused by a sharp propeller.
"At the time, we submitted a six-point recommendation to the authorities, which included a ban on plying mechanised boats in the river, a stop to extracting soil from the river, not allowing gill nets for fishing in the river, and declaring it as a sanctuary for dolphins," he said.
"The authorities actually complied with most of the recommendations. As a result, the rate of death has decreased to a great extent."
For example, he said, a total of 18 dolphins were killed in the five months between September 2017 and February 2018.
Compared to this, a total of 28 dolphins were killed in the three years between February 2018 and December 2020, while this year has seen the death of three more.
"This goes to show the benefit of following our recommendations. However, that's not nearly enough," he said.
With a lifespan of 25 years on average, a dolphin takes nine to 10 years to mature, and it takes around two years for an adult dolphin to birth a calf. This means a dolphin can give birth to around five calves during its reproductive years at maximum, he said.
"The rate at which dolphins are dying in the river is way faster than their reproduction rate. If proper steps are not taken in time, they could get
wiped out from the river in the near future."
He added that most of these deaths are from strangulation in fishnets. "While trying to eat fish caught in the net, they get strangulated and die," he said, adding, "We urge authorities to put a stop to the use of gill nets in the river."
"Just last month, we conducted a post-mortem on a dead dolphin at Chattogram Veterinary and Animal Sciences University (CVASU) and found that it was killed from strangulation," he said.
He also said conserving dolphins is important for the river's ecosystem. "We get an idea of the river's health from the presence of dolphins. It's a good indicator," said Dr Kibria.
According to experts, the Ganges river dolphin was first discovered in 1801. Named Shushuk in Bangla, it's an endemic aquatic mammal found only in the Indian subcontinent.
According to the International Union for Conservation of Nature (IUCN), the Ganges river dolphin is endangered globally as well as in Bangladesh (IUCN Bangladesh, 2015).
The species is included in the First Schedule of Bangladesh Wildlife (Protection & Security) Act, 2012 to ensure higher level of protection for their conservation, said Dr Kibria.
In 2019, Bangladesh Forest Department formulated an action plan under "Expanding the Protected Area System to Incorporate Important Aquatic Ecosystems Project" to conserve the Ganges river dolphin and Irrawaddy dolphin.
The plan was prepared by Dr Muhammad Abdul Aziz, a national consultant of Dolphin Conservation Action Plan and professor of Jahangirnagar University's zoology department.
In it, a total of 25 important habitats of the Ganges river dolphin were identified. Of them, Madunaghat to Sattarghat areas of Halda river and New Bridge Halda estuary were identified as two very important habitats.
But why is it important to protect the Ganges river dolphin?
The action plan report says the Ganges river dolphin is a tertiary organism in the food chain and is an important indicator species of our river ecosystem.
Although the species is found in almost all major rivers of Bangladesh, the north-eastern regions, including some upstream rivers, have been a stronghold of the species.
They are a flagship species for river conservation, whose protection can benefit a wider range of aquatic and threatened species, including the softshell turtle (Aspideretes gangeticus), gharial (Gavialis gangeticus), and smooth-coated otter (Lutra perspicillata), the report says.
Protection and maintenance of the species will ensure better health of the river ecosystem, which will ultimately benefit millions of local communities that survive on aquatic resources.
Its conservation is therefore important and urgent, before the species gets listed on the IUCN Red List of threatened species, says the report.
Contacted, Molla Rezaul Karim, conservator (wildlife and nature conservation) of Bangladesh Forest Department, said the action plan has provided a roadmap on how to conserve the endangered mammalian species, but the pace of implementation is slowed due to some limitations of the department, including human resource shortage and lack of proper logistics support.
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