The Indian Ocean is home to a rich diversity of marine life, including many species of whales and dolphins.
However, these cetaceans are facing multiple threats from human activities and environmental changes, which could jeopardize their survival and the health of the ocean ecosystem.
A recent study by researchers from the University of Exeter and Greenpeace has revealed a hotspot for cetacean diversity in a remote part of the Indian Ocean, and called for its protection as either an Important Marine Mammal Area (IMMA) or a Marine Protected Area (MPA).
A hotspot for cetacean diversity
The study, published in the journal Regional Studies in Marine Science, surveyed the waters around Saya de Malha, a vast submerged bank hundreds of kilometers off the coast of East Africa.
This area has not been previously explored for cetaceans, but the researchers found 12 species, including orcas, sperm whales, spinner dolphins, striped dolphins, and bottlenose dolphins.
The researchers used visual and acoustic surveys (over a 7,700 km area) using the Greenpeace vessel MY Arctic Sunrise, which was involved in a wider project to document marine life in the region during 2021.
According to the researchers, Saya de Malha is a unique area that includes seagrass meadows and coral reefs, and that the steeply shelving edges of the bank appear to be very important for cetaceans.
Moreover, Saya de Malha supports a diverse range of cetacean species and that the relatively shallow waters and tropical currents make it a hotspot for biodiversity.
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A need for protection
The researchers also highlighted the threats facing cetaceans in the Indian Ocean, such as habitat loss, pollution, overfishing, climate change, and coastal development.
They also pointed out that cetaceans are vulnerable to accidental entanglement in fishing nets and collisions with boats, which can cause serious injuries or death.
Furthermore, some cetaceans are targeted by illegal fisheries for their meat, fins, oil, and skin.
To protect cetaceans from further decline, the researchers propose that Saya de Malha should be designated as either an IMMA or an MPA.
An IMMA is a discrete portion of habitat that is important for one or more marine mammal species, while an MPA is a clearly defined geographical space that is recognized and managed to achieve long-term conservation of nature.
Both designations would provide recognition and guidance for conservation actions in the area.
The researchers also hoped that their study will contribute to the implementation of the United Nations treaty that aims to ensure the conservation and sustainable use of the high seas (beyond national waters), which was adopted in June 2021.
They argued that by protecting fragile and important habitats like Saya de Malha, placing them off-limits to destructive industries, we can begin to turn around the threats facing our world's oceans.
A possible connectivity
The study also discovered a possible connectivity between cetacean populations in Saya de Malha and other regions.
Analysis of sperm whale calls in the study showed a "match" with a well-studied sperm whale population off the coast of Mauritius, suggesting that whales may move between these two areas.
More research will be needed to confirm this.
The study also revealed 34 new species of microbes that have never been described before.
The whale sharks from Ningaloo had the highest number of novel microbial species, suggesting that there is still much to learn about the microbial diversity of marine animals.
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