Bangladeshi experts and officials have expressed concern and called for immediate research as an alarming number of giant whales and dolphins have recently been found dead on seashores of the Bay of Bengal.
At least six whales and 60 different species of dolphins were recovered dead from January 2020 to September 2021, according the Wildlife Conservation Society (WCS) Bangladesh.
The government, however, does not keep record of incidents and does not have official database on how many sea mammals have died recently in the Bay of Bengal.
A 10-meter (33 feet) whale was the last casualty which was suspected to have died from stomach perforation while another one died from a suspected fishing trawler strike. However, causes of deaths for other giant mammals were still unknown, according to officials from the Fisheries Department.
Certain cause of death still unknown, sea pollution creates disturbance
Zahangir Alom, the country representative of the Wildlife Conservation Society Bangladesh, told Anadolu Agency that the “causes of giant whales’ death are still unknown, and it needs a comprehensive morphological examination of carcasses and a skin tissue analysis as well as blubber, muscle or liver tissues to identify if there is any impact caused by pollution.”
Stomach content should also be examined to see if there is any plastics or polythene swallowed by the animal, urged Alom, who is among the very few dolphin researchers in Bangladesh.
“Sound pollution is a big disturbance for all marine mammals especially those who are dependent on echolocation for movement and searching for food. There is evidence that due to noise pollution some whales have shown stress, foraged less efficiently, and moved from their feeding and breeding grounds,” he added.
Abdul Aziz, a zoology professor at Jahangirnagar University in the capital Dhaka, called for immediate research on the deaths of sea mammals.
A rise in human activities and development work, fishing intensity, and movement of vessels on the sea are visually obvious and they could be among the causes, he told Anadolu Agency.
“Plastic pollution is another concern and among the major causes behind sea ecosystem pollution. Plastics and pollutants through the Padma and Ganga rivers directly reach the Bay of Bengal,” he added.
Aziz, however, said “there is no study on it if the whales and dolphins died from plastic pollution.”
Irrawaddy dolphin threatened with extinction
Bangladesh has about 6,000 globally red listed Irrawaddy dolphins, which are about 80% of the global population, according to experts.
The Irrawaddy dolphin is threatened with extinction and on the red list of threatened species by the International Union for Conservation of Nature.
The main threat to the Irrawaddy Dolphin is entanglement in gillnets. Meanwhile, habitat loss, degradation from pollution, dam construction, sedimentation, and vessel traffic are additional concerns.
“Sundarbans, the world’s largest mangrove forest, is among factors that we have a large number of Irrawaddy dolphins in Bangladesh. Sundarbans has helped creating a friendly ecosystem and food availability for them,” Aziz explained.
“Dead bodies of Irrawaddy dolphins were found in an alarming number certainly on Kuakata beach and others, we do not have records if deaths occur in deep sea and bodies could not come to shore,” the expert added, calling for urgent probe if there is any disorder in the sea or in the ecosystem.
There is evidence of saltwater fishes coming to fresh rivers which is also a matter of concern and we have to investigate it immediately to know if there is any disturbance in the sea or their ecosystem, Aziz mentioned.
Government working to probe death incidents, create awareness
Md. Sharif Uddin, an expert at the marine fisheries survey and management unit of the Fisheries Department, also echoed similar concerns, calling the situation “alarming” and “worrying”.
Sometimes dolphins chase a school of fish and accidentally get caught in a fishing net and incidents of death happen.
“Yes, there is plastic and microplastic pollution. But there are a number of facts that remain about sea pollution. Therefore, we cannot say anything certain without conducting any scientific study,” the official told Anadolu Agency.
The government is in talks with the Wildlife Conservation Society Bangladesh in this regard, including on conducting research on the matter, while the environmental group is also working to build awareness among local communities and fishers on how to release live dolphins from fishing gear safely.
The Wildlife Conservation Society Citizen Science Fishermen Safety Network has trained 31 fishing vessel captains to use a global positioning system to document their fishing activities and catches, and safely release entangled dolphins and porpoises, as well as sharks, rays and marine turtles, in exchange for improving their navigation safety.