Tuesday February 20, 2018 12:24 AM

Dolphins are evolving in the Bay of Bengal

Dolphins are evolving in the Bay of Bengal
A bottlenose dolphin gracefully displays its acrobatic skills Rubaiyat Mowgli Mansur/WCS-Bangladesh

The revelation comes from a recent study jointly conducted by the Wildlife Conservation Society (WCS), American Museum of Natural History (AMNH), and Centre for Ecology, Evolution Environmental Changes (cE3c).

The study titled “Oceanic drivers of population differentiation in Indo-Pacific bottlenose (Tursiops aduncus) and humpback (Sousa spp.) dolphins of the northern Bay of Bengal” was published in Conservation Genetics very recently.

The research team was headed by Dr Ana R Amaral of cE3c and AMNH’s Sackler Institute of Comparative Genomics with Brian D Smith, Rubaiyat M Mansur and Dr Howard C Rosenbaum of WCS.

The Bay of Bengal is enriched with nutrients flown in with the silt from a number of major rivers. As the river confluence encapsulates the Sundarbans – the world’s largest mangrove forest – it creates for a unique ecosystem. Furthermore, there is an undersea canyon called the Swatch-of-No-Ground (SoNG) which is renowned for recycling nutrients via a process known as upwelling.


The study took place in the Swatch-of-No-Ground WCS

As the region comprises of these diverse and unique natural factors, it creates for unparallel conditions for growth of species which can be found in different parts of the ocean.

The research team took the skin samples from 32 coastal Indo-Pacific and humpback dolphins. They extracted genetic sequences to compare with previously published sequences for both species. The findings showed both subspecies to be genetically discrete (individually different and distinct) from nearby populations.

The findings have the researchers saying the phenomenon merits further investigation.

Rubaiyat Mansur, principal researcher for WCS’s Bangladesh programme, said: “This is great news for Bangladesh.

Also Read- Desperately seeking dolphins

“Despite the challenges of wildlife conservation in our country, we take great pride in protecting our wildlife as evidenced by the recent declaration of Bangladesh’s first marine protected area in the Swatch-of-No-Ground submarine canyon and adjacent estuarine waters.”


Humpback dolphins are more popularly known because of their bright pink skins Rubaiyat Mowgli Mansur/WCS-Bangladesh

Dr Rosenbaum, director of WCS’s Ocean Giants programme, said: “The discovery of genetically distinct dolphin populations helps us to expand the body of knowledge of how these dolphin species have changed over time.

“These results have significant implications for identifying unique marine mammal populations, which in turn have important conservation implications for safeguarding the long-term biodiversity in this region.”

Also Read- Country’s southerner fishermen to turn dolphin saviours 

The two dolphin species are threatened by entanglement and death in fishing nets. Many of the individual dolphins photographed by researchers bear the scars of being entangled in fishing nets while the photographed ones are the lucky few who escaped.


Dolphins, being an intelligent species, often interact with humans, even when they pose danger in the form of fishing trawlers Rubaiyat Mowgli Mansur/WCS-Bangladesh

“The results of this study raise important questions about the exact conservation status of these small cetaceans of the Bay of Bengal,” said Brian Smith, a co-author on the study and Director of WCS’s Asian Freshwater and Coastal Cetacean Programme.

“Our findings highlight areas for further inquiry as well as the importance of protecting these marine mammals from the threat of fishing entanglement.”

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