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New population of Blue Whales discovered in Western Indian Ocean

ESO - New Population of Blue Whales in the Western Indian Ocean 1
ESO - New Population of Blue Whales in the Western Indian Ocean 1

Muscat: An international team of researchers has discovered what it believes to be a new population of blue whales in the Western Indian Ocean, including the Arabian Sea and the Coast of Oman. This came as part of a research effort initially focused on the highly endangered Arabian Sea humpback whale, with ongoing collaboration between the Environment Society of Oman, New England Aquarium, African Aquatic Conservation Fund, Five Oceans Environmental Services LLC, Oman’s Environment Authority and Oman’s Ministry of Agriculture, Fisheries and Water Resources. The work was funded by Shell Development Oman LLC (SDO), with support from the International Whaling Commission, Renaissance Services S.A.O.G., and NOAA Fisheries.

Blue whales are the largest animals that have ever lived on our planet, and they are found around the globe in all oceans. All blue whales sing very low-pitched and recognizable songs, and conveniently for researchers, every population has its own unique song. In a recently published paper in the journal Endangered Species Research, the researchers describe a new blue whale song that is heard from the Arabian Sea coast of Oman across to the Chagos Archipelago in the central Indian Ocean and as far south as Madagascar in the southwest Indian Ocean.

Dr. Salvatore Cerchio, Director of the African Aquatic Conservation Fund’s Cetacean Program and Visiting Scientist at the New England Aquarium, led the analysis of recordings of the ale from three locations in the western Indian Ocean. Dr. Cerchio first recorded the novel song in 2017, during research focused on Omura’s whales in the Mozambique Channel off Madagascar, and he recognized it as a blue whale song that had never been described while working with a team of scientists collecting acoustic recordings off the coast of Oman in the Arabian Sea. While analyzing the Oman acoustic data, the team recognized the same unusual song. This novel blue whale song likely belonged to a previously unrecognized population of blue whales in the western Indian Ocean.

“It was quite remarkable,” said Cerchio, “to find a whale song in your data that was completely unique, never before reported, and recognize it as a blue whale.” Blue whale song has been extensively studied globally, and several blue whale populations have been identified based on their distinct songs throughout the Indian Ocean.

In 2018, the research team reported their findings to the Scientific Committee of the International Whaling Commission (IWC), which was in the process of evaluating the status of blue whale populations in the Indian Ocean. The finding created quite a bit of excitement at the meeting, and raised many new questions about blue whale population movements and structure in the Indian Ocean.

Dr. Thuraya al Sariri, Deputy General Director of Nature Conservation, Oman’s Environment Authority said, “Our objective is to always contribute to preserving the environment and its resources. The finding of blue whales across Oman’s coast is quite extraordinary. We look forward to continue collaborating with all partners to boost research showing evidence on how these endangered species can be conserved in the Arabian Sea.”

Upon reading the IWC report on the new song, researchers from the University of New South Whales recognized that the song had also been recorded off the Chagos Archipelago in the central Indian Ocean. The collaborative team grew, and analysis of data from three sites suggested that the population may spend most of its time in the Northwestern Indian Ocean, in the Arabian Sea and to the west of the Chagos. It has long been recognized that a unique population of blue whales resides in the Northern Indian Ocean, but it was assumed that whales in the Arabian Sea belonged to the same population that has been studied off Sri Lanka and ranges into the southcentral Indian Ocean. However, the songs tell a different story.

Walid Hadi, Oman Shell Country Chairman said, “Oman Shell is always working towards building collaborations with key partners like the Environment Society of Oman. This research provides a significant step to help scientists in formulating a new understanding of the world of the endangered blue whales’ population. Despite their incredible size, this species often depends on conservation efforts in order to keep them protected. Dedicating our efforts to understand their patterns and behaviours will certainly aid the restoration of this species’ population”

Blue whales were hunted to near extinction around the globe during the 20th century, and populations have only started to recover very slowly over the past several decades following the global moratorium on commercial whaling. The Arabian Sea was targeted by illegal Soviet whaling in the 1960’s, an activity that nearly eradicated what were already likely to be small populations of humpback whales, blue whales, sperm whales, and Bryde’s whales.

Some researchers consider both the northern Indian Ocean blue whales and Arabian Sea humpback whales to comprise unique subspecies, not simply populations, making them particularly special and important to biodiversity.


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