are a slow-moving filter feeding sharks, the largest known extant fish species, reaching up to 12 metres in length and weighing in excess of 20 tonnes. It is the sole member of the family Rhincodontidae, originating around 60 million years ago.
Whale sharks are found in tropical and warm oceans and have a lifespan of around 70 years. They have very large mouths and feed mainly on plankton and small fish.
Whale sharks can occasionally be spotted all along the Indian Ocean coastline of Kenya, Tanzania, Mozambique and the more north-easterly parts of South Africa.
But the only place where we know that they can be reliably found year round is off Mafia Island
in southern Tanzania. Up to 2011 whale sharks were thought to be migratory, but a local fishermen reported to one of our friends on the island, Jean de Villiers of Chole Mjini Lodge
, that he was seeing them year round. We now understand that the larger adults appear to migrate away from the island May/Sep, with juveniles of up to 2.5 metres remaining in year round. The best time of year seems to be Dec/Mar, when adults up to 7 metres are regularly encountered. Visibility tends to be best November to January.
It has since been discovered that the younger creatures remain here year round, whilst the older animals undertake and an annual migration around large parts of the Indian Ocean.
In 2008 Jean helped to set up a scheme to protect these whale sharks, fearing the repeated harassment by motorboats might drive them away. The area can now only be approached with a licensed operator. Sightings are not guaranteed year round, but are highly likely. Very often visitors are able to get into the water to watch these majestic giants glide by. This is a marine experience of epic proportions and people are drawn to the island from around the world specifically to swim with whale sharks.