Since October 2023, Dr Antonin Blaison has been setting up an acoustic monitoring system for grey sharks on the reefs of Mauritius. We take a look at the background to this first study, financed by the European Interreg V OI and the Réunion region, as he prepares to present the initial results at the end of January in Mauritius. Dominique Bellier
Fear is often rooted in ignorance, and in the case of sharks, it has been coupled with sensationalist filmography and literature that have fostered prejudice and inappropriate human behavior. Dr Antonin Blaison can testify to this, having dedicated his life to studying sharks in South Africa, Reunion and Mauritius, while the filmJaws gave him the worst nightmares of his childhood…
Today, he swims alongside these fascinating predators, which are becoming increasingly rare despite the fishing ban. At the end of August, he presented Odysseo with the MAETAG research project, aimed at observing the behavior and lifestyle of grey reef sharks, the most widespread species in Mauritius, yet considered endangered by the IUCN. The project is led by the Observatoire Marin and the Centre de Sécurité Requin de La Réunion, in collaboration with the University of Mauritius, the Marine Megafauna Conservation Organisation and Odysseo. A place like the shark pit,” he explains, “is practically unique in the world. Through this study, I’d like to help people learn to live in harmony with them. The best way to do this is to get to know them better…”.
In December, he analyzed the latest data recorded by ten acoustic receivers set up since October in the vicinity of Snake Island and Île Ronde, near the pit. He will present the analysis, the first study of its kind in Mauritius, at a public conference this month. The most delicate operation involved placing an acoustic marker on each shark, using an arrow modified to avoid injuring it. To aim at a sparsely innervated part just below the first dorsal fin, you have to get as close as 50 cm! He was able to do this at the beginning of October, accompanied by an assistant who managed his safety, while he concentrated on his shot.
Everything went really well,” he enthuses. They reacted well to the marking. Four mature females and one mature male became study subjects, including one pregnant female. The receivers detect passages within an average radius of 400 m.
“The data collected – who was there, when and at what time? at what depth?… – provide information on their activities in the listening zone. Their movements will tell us, for example, whether they are hunting or resting. Eventually, we’ll be able to map out their habits according to season and time of day or night.
