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The first dedicated surveys have confirmed the presence of blue whales around Seychelles, after their populations were decimated by whalers in the 1960s, according to a new study recently published in the journal Endangered Species Research.
The waters around Seychelles were a major hunting ground for Soviet whalers in the mid-20th century, until in 1978, having just been accepted as a member of the International Whaling Commission (IWC), the Republic successfully lobbied for the creation of the Indian Ocean Whale Sanctuary in 1979.
While Seychelles’ coral, turtles and sharks have been relatively well studied, little is known about the cetaceans of the western tropical Indian Ocean. However, scientists from the University of Seychelles, Florida International University and Oregon State University have begun to uncover just how important the waters around Seychelles are for marine mammals, having recorded 23 species over the course of just two seasons in the field.
Despite their size, blue whales (Balaenoptera musculus) are extremely difficult to locate, track and monitor, but the recent surveys have confirmed they are regular visitors to Seychelles, especially between December and April. Scientists hope that the discovery will help to reliably survey and monitor the elusive giants in the future.
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As of today, there have been five confirmed sightings in the past five years. ‘Never in my life would I have imagined that the biggest animal on planet earth cruises our oceans here in Seychelles,’ said Ms Dillys Pouponeau, a research assistant at the Save Our Seas Foundation (SOSF) D’Arros Research Centre, who joined the most recent expedition as a digital imaging technician for Oceanic Films’ Blue Whales – Return of the Giants. ‘To me, this was big news because it reflects the productivity of our oceans,’ she said.‘It shows how regulations have helped to protect this species after whaling.’
The new study was co-authored by Save Our Seas Foundation (SOSF) project leader Dr Jeremy Kiszka, professor of biology at Florida International University and research associate at the University of Seychelles.
‘Blue whales are protected because they are no longer legally hunted, but they still face a range of threats,’ said Dr Kiszka. ‘Shipping traffic causes noise pollution and can lead to collisions. Climate change is changing the distribution and abundance of their key food, krill.
‘We now need to increase our research efforts to assess the abundance of these blue whales and discover why they are using Seychelles’ waters,’ added Dr Kiszka. ‘We also need to raise awareness and help the government to protect them better. We need to raise funding to start dedicated research on blue whales.’
Of the four subspecies of blue whale that are known to exist, the scientists have confirmed that the group that visits Seychelles are members of a Sri Lankan population of pygmy blue whales. Identification of the whales is through their song, which is distinct to each group – rather like accents among humans – recorded through hydrophones and painstakingly listened to by the researchers.
Having identified the presence of the giant cetaceans, the team will focus their efforts on trying to determine how many there are, why they have returned to the area, why they seem to prefer the months between December and April,
‘Recording blue whales was a big moment – I hope that we can share this with more students from Seychelles, and from further afield,’ said Dr Kiszka. ‘Blue whales have no borders; we need to conduct research on an appropriate scale, and we need to collaborate internationally. It’s a phenomenal opportunity to understand them.’
The study ‘Acoustic detections and sightings of blue whales Balaenoptera musculus in the Seychelles, western tropical Indian Ocean (2020−2022)’, by Dr Jeremy J Kiszka, et al, is published in Endangered Species Research.
