One of the techniques used in the whale shark monitoring efforts in Madagascar is acoustic tagging.

The acoustic tags used in this project are V16 from Innovasea and will be deployed on a whale shark when it is possible, between September and December. We only deploy tags in ideal conditions when the animal is relaxed and when we are alone at sea. It attaches externally below the dorsal fin thanks to a metallic tether, using an adapted harpoon. The sharks don’t usually react.

Once deployed, this tag will emit a unique frequency that will communicate with one of the 20 underwater acoustic receiver stations, which will record the exact time, and tag unique frequency and number if the tagged shark swims within an 800m diameter of one of the stations. This way, we gather information about which area the shark is using. We only record the data once we dive on the receivers, twice per year. The tag can last for a few years, unless it falls off the shark.