According to Save the Nature of Bangladesh–a wildlife conservation group–seven dead dolphins washed ashore in Cox's Bazar last year. In a sharp rise, the group found at least 15 dolphins and two whales dead along the world's longest sea beach district between January and June this year.
Although there is no study, experts assume that pods of dolphin are migrating from their south-west colonies, particularly the Swatch of No Ground and the Sundarbans, to the country's south-east marine territory due to increasing abundance of hilsa fish there.
Then, how is the migration is related to increasing mortality of dolphins?
The incident is still a mystery to the authorities concerned. The Forest Department operates a forensic lab at its headquarters in Dhaka. But it has yet to perform forensic tests on the corpses. The local forest officials prepare post-mortem report with a common finding–dolphins died from stroke.
The government has imposed a 65-day ban on marine fishing from May 20 to July 23.
During the embargo, the incidence of dolphin mortality has dropped significantly, said ANM Moazzem Hossain, chairman of Save the Nature of Bangladesh. He believes that marine fishing is the major reason for the death of dolphins.
"If there is no fishing net or motorized vessels in the sea, no dolphin would get hurt and die," Moazzem told The Business Standard.
May be there are some other reasons too. It is crucial now to find out the actual causes of such deaths when Forest Department, Department of Marine Fisheries (DMF) and Bangladesh Oceanographic Research Institute (BORI) all fail to provide concrete evidence, except blaming traditional fishing.
Traditional knowledge suggests that dolphins indicate abundance of hilsa and other sea fishes. So, fishermen place nets in the water around a pod, and the dolphins get trapped. The fishermen hit the dolphins with sharp weapons to weaken them, tie their tails with rope and then remove them from the net.
Some of the dead dolphins are eaten away by predators and some wash ashore.
BORI's senior scientific officer Abu Sayeed Muhammad Sharif has been studying marine lives for more than two decades.
According to his incidental analysis, he said, "Most of the dead dolphins were found either finless or bearing several injury marks. The death of ecologically important marine mammals is really unfortunate and worrisome."
Whales and dolphins cannot breathe underwater like fish can, as the marine mammals do not have gills. They breathe in the air through blowholes. When a dolphin surfaces for air, it takes a fraction of a second to breathe out and inhale fresh air.
Sharif explained, "When they (whales or dolphins) get entangled in the fishing net, they cannot breathe, and after a while, they die."
Before the trapped dolphins' last breath, fishermen often kill them to protect the fishing net. Because, trapped or not, the cetaceans can show their strength in the water.
Dolphin Conservation Action Plan's national consultant Mohammad Abdul Aziz, also a professor of Zoology at Jahangirnagar University, observes that fishing net is a great threat for all of the seven cetacean species available in Bangladesh water.
Of the species, fresh water-dependent Ganges river dolphins and brackish water-dependent Irrawaddy dolphins are prominent.
"The high traffic of motorized vessel which creates wave in the water disturbs cetaceans' echolocation. Fishing nets, particularly those used for catching hilsa fish, also confuse the dolphins. If their echolocation is disturbed, they go astray and often get trapped in the nets or collide with boat propellers," Aziz said.
The fishermen of Cox's Bazar contribute hugely to the country's annual marine fish production of more than six lakh tonnes. So fisherfolk always have the authorities' blessings and can escape legal actions, believes the local wildlife conservationists.
Wildlife (Conservation and Security) Act has a provision of three years in jail or Tk 3 lakh in fine for killers of dolphins or whales while a person carrying trophy or marine mammals would be punished with two years of imprisonment or Tk 1 lakh in fine.
In the near past, none has been punished for killing cetaceans.
The Protection and Conservation of Fish Act bans use of gillnets. None could be imprisoned and not a single metre of gillnet was seized in 543 raids across Chattogram division during 2017-18 fiscal year.
But Delwar Hossain, general secretary of Cox's Bazar Fishing Boat Owners Association, denied the accusation. He claimed that the boats under the association are for deep-sea fishing while the dolphins mostly live in the shallower coastal areas.
He said, "The fishermen under our association do not hurt dolphins. There are hundreds of other fishermen, the former traffickers of Rohingyas, under unregistered associations. They catch fish offshore using small boats and gillnets. But the authorities turn a blind eye to them."
The authorities turn a blind eye at the marine water polluters too. There are 216 star-categorised hotels operating in the tourist district, without any sewage treatment plant. Meanwhile, all the municipal wastewater ends up in the sea through Bakkhali channel, affecting marine habitats adversely.
Professor Aziz said, water pollution kills microorganisms like phytoplankton and zooplankton–the base of the dolphins' food pyramid.
The Department of Environment has declared Cox's Bazar an ecologically critical area. Meanwhile, the Forest Department has enacted a law to protect at least 12 marine species. But both the departments lack power to protect marine lives.
A senior forest officer, preferring to be anonymous, admitted this.
There is also the Department of Marine Fisheries.
"We could address the crimes relating to marine resources. We have the expertise. But we also need to be empowered by laws," said Mohammad Nazim Uddin, an assistant director of the Marine Fisheries department.
Citing the ongoing 65-day ban on marine fishing, Nazim added that with merely a single checkpoint at Kutubdia, it is impossible for the department to check violation of the ban.
However, the department is implementing a project for construction of 17 new checkpoints along the country's 710-kilometer coastline. The department is also expecting to get required manpower to operate the checkpoints and patrol vessels.
Sometimes, weak or injured dolphins and whales wash ashore. During low tide, they get trapped and die.
Save the Nature of Bangladesh chairman Moazzem seeks government support to form a rescue team. "Moreover, we need veterinary facility in Cox's Bazar," he said.
However, Nazim, echoing the words of Forest Department and BORI officials, said that unless an exclusive study on the threats of marine mammals is done, the reasons of the dolphin fatality will not be determined.
Another marine conservationist, Mohammad Arju, said that while some dolphins might get killed being trapped in the fishing nets, research at global stage determined that the use of underwater sonar by ships and submarines can interfere with the bisonar sounds produced by cetaceans and can be fatal for them by affecting their ability to navigate and to locate and catch their food.
"There is a dearth of research on how these dolphins are getting killed in Bangladesh. Without proper research at local level, one should not blame the fishers for the dolphins' death," said Arju.