A large population of whale sharks has been discovered in the waters off Madagascar

Thanks to its historic isolation, Madagascar has long been famed for its unique wildlife, ranging from lemurs and rare chameleons to exotic birds and the carnivorous, cat-like fossa. But now a new study published in the journal Endangered Species Research has revealed that the island nation is also a hotspot for whale sharks (the world’s largest fish).

A single season survey, part of the Madagascar Whale Shark Project (a collaboration of researchers from Mada Megafauna, Marine Megafauna Foundation and Florida International University), identified 85 juvenile whale sharks swimming in an area around the island of Nosy Be in the country’s far northwest. These waters had previously been noted for sea turtles, manta rays and migrating humpback whales, but the sheer number of whale sharks that arrived to feed during the September to December period was a huge surprise. Also of importance was the fact that these individuals represented an undiscovered population – they were not simply displaced from other known feeding areas in the Indian Ocean – Mozambique, Tanzania, Djibouti, Seychelles and the Maldives – that have experienced a decrease in whale shark populations. This information came to light after the marine biologists uploaded images of the new sharks’ unique spotted patterns to the Wildbook for Whale Sharks global database and discovered no overlap.

Several of the whale sharks that were observed were also tagged to track their movements, and the team discovered a second Madagascan hotspot near Pointe d’Analalava, some 180 km to the south of Nosy Be. Other data revealed that five of the sharks swam as far as the Comoros Islands, while another two migrated some 2150km to the southern tip of Madagascar. One of the latter two made the return journey, thus covering about 4300km, an impressive figure given these slow swimmers cover only 20km or so each day.

It’s hoped the whale sharks can be a major asset for Madagascar, particularly if access is well managed by the country’s burgeoning ecotourism industry. In recent decades overfishing (including accidental catches) and boat strikes have put whale sharks on the RIUCN RedList as a globally endangered species.