The data indicates that humpback dolphins show a contiguous distribution across the state’s waters in the Arabian sea
A study titled ‘conservation genetics of humpback dolphins along the Maharashtra coast with a secondary focus on cetacean strandings' was conducted by Mihir Sule from the Konkan Cetacean Research Team and funded by the Mangrove Foundation of the Maharashtra Forest Department.
The study was conducted between 2020-22, a first for the state. The secondary data was collected from fishermen across the entire Maharashtra coastline using interview surveys to map the distribution of Indian Ocean humpback dolphins (sousa plumbea).
The data indicates that humpback dolphins show a contiguous distribution across the state’s waters in the Arabian sea. They occur in waters less than 30-35 meters depth and may often enter the larger estuaries at high tide. There appear to be no breaks in their distribution across this region. Due to their shallow water habitat, humpback dolphins are commonly seen by fishermen, from their vessels and from the sea shores. The regional common names of the humpback dolphin differ across the coastline.
In phase two of this study, tissue samples from the carcasses of marine mammals (incidentally entangled, stranded) were collected. Two workshops (June 25, 2021: In-person and July 20 2021: online) were also conducted with the Maharashtra State Forest Department staff to train them as first responders for dealing with marine mammals stranding.
Using samples of humpback dolphins from this study, genetic analysis was also carried out.
Population genetics analyses also show that the humpback dolphin population along the Maharashtra coast (West coast of India population) is most closely related to the East Coast of India/Bangladesh population. This is a significant observation, as currently, the East and West coasts of India are thought to have two different species of humpback dolphins, i.e., Indian Ocean humpback dolphin along the west coast and Indo-Pacific humpback dolphin along the east coast of India.
The west coast population should be closely related to the Oman population, both being the same species, Indian Ocean humpback dolphin. However, the results of this study show a significant degree of separation between the Oman and the west coast of India populations.
Mihir Sule said, "The Maharashtra coastline has about twelve species of marine mammals, as documented in previous studies and stranding records. Little is known about their distribution across our coast. This study has shown that the Indian Ocean Humpback Dolphins are distributed across the coast of Maharashtra without any breaks in their population which is significant."
This study is one among the various research projects that the Mangrove Foundation has commissioned regarding scientific study of the Cetaceans of Maharashtra and the results of this study along with other similar studies will help us better conserve the Cetacean populations of the state', said Virendra Tiwari, APCCF, Mangrove Cell and Executive Director, Mangrove Foundation.