**Acknowledgements**

We would like to express thank all members who contributed to the dolphin research. Also, thanks to Dr. Mohammad Saiful Islam, chairman, Department of Zoology, JnU for his special discussion on marine mammals. In specific, we would like to express our heartfelt gratitude to Rafi, Nur Alam, Kisor Kumar Sarkar, and Hasan Al Razi. Special thanks to Ifat Jahan for picture editing and collection. We also thank an unsigned assessor for useful notes on a former draft.
